et ‘a FAN eet rte furs a Wika teu h ‘ sone tun EAC < pene Recap an aien Su neaepy tao Sire Pyakicy a ay oh it erie ne THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Pri Sevics. VOLUME XIII. DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS & NORGATH, 14 HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1911-1913. IN : DANS fi THE SOCIETY desires it to be understood that it is not answerable for any opinion, representation of facts, or train of reasoning that may appear in this Volume of its Proceedings. The Authors of the several Memoirs are alone responsible for their contents. Dustin: Printep at THE University Press ny Ponsonpy AND Grpns, SOG Wass CONTENTS. WOlL, 200 No. I.—A Seed-Bearing Ivish Pteridosperm, Cros.stheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.sc., F.L.s. (Plates L—III.) (March 8, 1911.) . II.—Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorce H. PrroypripGr, B.SC., PH.D. (March 6, 1911.) I1I.—Mechanical Stress and ieemotieotton of Niokell (Part Ur. yy a the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witt1am Brown, 8.sc. (April 15, 1911.). TV.—A Thermo-Electric Method of Cryoscopy. By Henry H. Dixon, so.pD., F.R.s. (April 20, 1911.) V.—A Method of Exact Determination of the Gentes Gheives in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrirtam J. Lyons, B.a., A.R.c.Sc. (LOND.), (May 16, 1911.) : : : : VI.—Radiant Matter. By Joun Joty, sc.p., rR.s. (June 9, 1911.) VII.—The Inheritance of Milk-Yield in Cattle. By Jamzs Witsoy, m.a., B.sc. (June 12, 1911.) 0 0 6 : VIII.—Is Archeopteris a Pteridosperm? By T. Jounson, p.sc., F.L.s. (Plates IV.-VI.) (June 28, 1911.) IX.—The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jounson, p.so., F.u.s. (Plates VII. and VIII.) (June 28, 1911.) X.—Award of the Boyle Medal to Prorrssor Joun JoLy, M.A., SO.D., WRs. (July, 1911.) XI.—On the Amount of Radium Emanation in ‘ih Soil and its acare into the Atmosphere. By Joun Jony, sc.p., F.R.s., and Louis B. SmyrH, B.A. (Plate IX.) (August 29, 1911.) XII.—Contributions to our Knowledge of the Floras of the itt Carboniferous Rocks. Part I. By H. A. Newrxu Arser, ™.a., F.L,S., F.G.S. (Plates X.-XII.) (January 20, 1912.) PAGE 12 28 49 148 iv Contents. No. XIII.—Forbesia cancellata, gen. et sp. noy. (Sphenopteris, sp., Baily.) By T. Jounson, p.so., F.u.8. (Plates XIII. and XIV.) (January 19, 1912.) * : . XIV.—The Inheritance of the Dan Gone Caton in Horse. By James WiLson, M.A, B.Sc. (January 19, 1912.) XV.—On the Vacuum Tube Spectra of the Vapours of some Metals ce Metallic Chlorides. Part I.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Potnocr, p.sc. (Plates XV. and XVI.) (February 21, 1912.) XVI.—Changes in the Osmotic Pressure of the Sap of me Derslopae Leaves of Syringa vulgaris. By Henry H. Dixon, sc.p., F.B.8., and W, R. G. Arnins, m.a. (February 21, 1912.) XVII.—Improvements in Equatorial Telescope Mountings. By Str Howarp Grup, F.R.s. (Plates XVII.-XIX.) (March 26, 1912.) XVIII.—Variations in the Osmotic Pressure of the Sap of Ilex Aquifoliwm. By Henry H. Dixon, sco.p., r.r.s., and W. R. G. Arxins, m.a., atc. (April 9, 1912.) : ‘ : XIX.—Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera Helix. By Henry H. Dixon, so.p., F.z.s.,and W.R. G. Arxins, M.a., at.c. (April 9, 1912.) XX.— Heterangiuwm libernicum, sp. nov.: A Seed-bearing sere beh from County Cork. By T. Jounson, D.sc., F.L.s. oe XX. and XXI.) (April 12, 1912.) 6 XXI.—On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part [1.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By James H. Potnox, p.sc. (Plates XXII. and XXIII.) (May 7, 1912.) ; XXII.—The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Copper, and Lithium. By Gernrevirve V. Morrow, A.R.0.s0.1. (Plate XXIV.) (May 11, 1912.) XXIII.—Award of the Boyle Medal to Sir Howarp Gruss, F.r.s., April 16, 1912. (May 18, 1912.) 5 é XXIV.—Notes on Dischidia rafflesiana, Watu., anv Dischidia nummularia, Br. By A. F. G. Kerr, mp. (Plates XXV.-XXXI.) (September 30, 1912.) XXV.—Recherches Expérimentales surla Densité des Liquides en dessous de 0°. Par Jean Timmermans. (October 18, 1912.) XXVI.—Steady and Turbulent Motion in Gases. By Joun J. Downtne, M.A. (Plates XXXII, and XXXII.) (November 16, 1912.) PAGE 177 184 202 219 223 229 239 247 258 269 288 293, 310 375 Contents. No. XXVII.—Unsound Mendelian Developments, especially as regards the Presence and Absence Theory. By Jamus Witson, ™.a., B.So. (December 18, 1912.) : : : ; XXVIII.—Osmotic Pressures in Plants. I.—Methods of Extracting Sap from Plant Organs. By Hrnry H. Dixon, so.p., F.r.s., and W.R. G. Arxins, m.a., a.t.c. (February 8, 1918.) . XXIX.—Osmotic Pressures in Plants. I1.—Cryoscopie and Gonancnnies Measurements on some Vegetable Saps. By Hunry H. Dixon, Sc.D., F.R.s., and W. R.G. ATKINS, M.A., A.1.0. aes 8, 1913.) XXX.—A Method of Misrosospic Mensurementt ey J. j OLY, SC.D., F.R.S. (February 7, 1913.) . XXXI.—The Melting-Points of some of the Raver Monona By Musee L. FLEeroHer, M.A., B.E. (February 15, 1913.) : XXXII.—A Refined Method of obtaining Sublimates. By Arnoup L. FLETOHER, M.A., B.E. (February 17, 1913.) . : XXXITI.—On the Germination of the Seeds of some Dicotyledons. By J. Apams, u.a. (Cantab.). (Plate XXXIV.) (February 21, (1913.) XXXIV.—On Bor nodentson|(Cyetstcqna) ltoriconse ioweinion, sp. By T. JoHNson, D.so., F.L.8. (Plates XX XV.- ve wee 20, 1913.) : XXXV.—On the Rotting of Botatn Taber by a new species of Phytophthora having a method of Sexual Reproduction hitherto undescribed. By Grorcr H. Prrnysripen, PH.D., B.sc. (Plates XLII.—XLIV.) (March 26, 1913.) XXXVI.—On Pure Cultures of Phytophthora infestans De Bary, and the Development of Oospores. By Grorce H. Prruysrines, PH.D., B.sc., and Paun A. Murpay, a.r.c.sc.1. (Plates XLV. and XLVI.) (March 26, 1913.) : XXXVII.— Inter-Alternative as opposed to Coupled mencenart Factors: A Solution of the Agouti-Black Colour in Rabbits. By James Witson, M.a., B.sc. (March 27, 1913.) XXXVIII.—Notes on Recent Pampa and other Formations in Patagonia. By E.G. Fenton. (Plate XLVII.) (May 15, 1913.) XXXIX.—On the Influence of Self-Induction on the Spark Spectra of Certain Non-Metallic Elements. By Gunevirve V. Morrow, a.R.c.so.1. (Plates XLVIII.-LI.) (May 19, 1913.) 399 467 500 529 589 600 607 Pan TAO aa THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 1. - MARCH, 1911. A SEED-BEARING IRISH PTERIDOSPERM, CROSSOTHECA HONINGHAUSI, Kwsron (LYGINODENDRON OLDHAMIUM, Wrux2841amsgoy). BY T. JOHNSON, D.Sc., F.L.S., PROFESSOR OF BOTANY IN THE ROYAL COLLEGE OF SCIENCE FOR IRELAND. (PLATES lI.-Il I.) [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCILN'Y, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATEH, — M4, HENRIETTA STREET, COVENT GARDEN, LONDON, JR some 1911. Price One Shilling. Roval Dublin Society. PO On FOUNDED, A.D. 1781. INCORPORATED, 1749 EVENING SCIENTIFIC MEETINGS, Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. ——__@—_____ I. A SEED-BEARING IRISH PTERIDOSPERM, CROSSOTHECA HONINGHAUSIT, Kinston (LYGINODENDRON OLDHAMIUM, WILLIAMson). By T. JOHNSON, D.Sc, E.LS., Professor of Botany in the Royal College of Science for Ireland. (Puatzs I-III.) [Read November 22. Ordered for Publication, DrcempEr 2, 1910. Published Marcu 8, 1911.] Durine the past twenty-five years the views of botanists as to the inter- relationships of the various groups of the Vascular Cryptogams or Pteridophyta, and as to their line of evolution, have profoundly changed. At the beginning of this period it was generally thought that the ferns were connected by the Leptosporangiate groups—the Hymenophyllacez (the Filmy Ferns) and the Polypodiaceze with the Muscines, through such a Liverwort as Anthoceros. This view was abandoned largely as a result of the researches carried out by Professor F. O. Bower! on the embryogeny of the sporc-bearing members of the Filicineze and other Pteridophyta. He concluded that the earlier members of the Filicineze are the Hu-Sporangiata, i.e. the Ophioglossaceze and the Marattiaceze. This opinion, based on the investigation of the anatomy of living ferns, supported the evidence already derived from the study of fossil ferns. The earliest and most commonly 1F. 0. Bower: ‘‘ The Origin of a Land Flora,’’ 1968. On p. 654, the three allied families, Botryopteridee, Osmundacee, and Hymenophyllacez, are described as blind branches of descent. 2 Stur: ‘‘ Zur Morphologie u. Systematik d. Culm u. Carbon-Farne,”’? 1883. On p. 845 Stur states that the Gleicheniaceze, Osmuadacez, and Schizzaceze were Post-Carboniferous ; andon p. 795, that the Marattiacee reached their maximum of development (15 genera and 98 species) in the Culm and Carboniferous—especially in the Lower Carboniferous (in which the Culm of Stur is now included). The rapid change of view in this branch of botanical work is indicated by E. A. N. Arber (Annals of Botany, xx., p. 230), who states :—‘*‘ Thus the Geological Record no longer supports the conclusion arrived at by some botanists from a study of the recent ferns, that the Eusporangiate is the more primitive type as compared with the Leptosporangiate.’’ Stur’s many MJarattiacee are, SCIENT, PROC. R.D.S., VOL. XIII., NO. I. A 2 Scientific Proceedings, Royal Dublin Society. found ferns were regarded as members of or as allied to these two groups of Eu-Sporangiatee and to the Cyatheaces.' A great many of these “ferns” were, however, early in the last century, noticed to be sterile; and, according to Lotsy, Austen in 1849, at a meeting of the British Association, sought to explain this by the suggestion that the temperature in the Carboniferous epoch was too low for fructifications to be formed. One of the most beautiful of these ferns is Sphenopteris affinis, which, as Seward recalls, appears as the frontispiece in Hugh Miller’s “ ‘Testimony of the Rocks.” I find that, in describing the fern, Miller mentions that it possessed peculiarities exhibited by no fern then living (1857), according to the botanists of the day whom he consulted. One of these he mentions in another part of the book by name (Professor J. H. Balfour, of Edinburgh). Hugh Miller’s is the first suggestion I have seen that the ferns forming half the flora found in the Upper Devonian and Carboniferous deposits, were not altogether fern-like. Tn 1883 Stur, after twenty years’ devotion to Palzo-botany, emphasized this idea, and placed aside, in a group which he called “ Nichtfarne,” for subsequent description, many forms at that time included with the Ferns. As a result of the investigations of the structure of such forms, Potonié, finding characters suggesting in some respects fern- and in other Cyead- affinities, created in 1897 a special group for them, which he called the Cycado-Filices, in which one authority would place all the Devonian and Lower Carboniferous ‘“‘ Ferns.” Of these forms one of the most interesting is Lyginodendron oldhamium, whose stem Williamson described in 1873. In 1874 he described its petiole as Rachiopteris aspera, suspecting, however (as he found later to be the case), that it was part of Lyginodendron oldhamium. Later on Kidston found that a fossil fern whose foliage had been described by Brongniart under the name of Sphenopleris Honinghausi was, in reality, the foliage of Lyginodendron. ‘Thus three different parts of one type had been described under three distinct names. In 1894 Williamson and Scott completed the story of the discovery of the vegetative organs by showing that the roots Kaloxylon Hookert were the adventitious roots of Lyginodendron oldhamium. It would be out of place here to give more than a summarized account of the vegetative organs of Lyginodendron. Readers may consult the articles contributed by Williamson and Scott to the Philosophical Transactions of the Royal Society in 1894 and 1896, and especially the well-illustrated, it is now thought, mostly Pteridosperms, and there is, it is stated, little evidence even in Mesozoic rocks of the Eusporangiate type. In a forthcoming paper on dArcheopteris I hope to discuss this question. 1 Stur regarded Calymmotheca (which Zeiller corrects to Calymmatotheca) as one of the Cyatheacez, His two genera of the Ophioglossaceze haye their position as such questioned to-day. Jonnson—A Seed-bearing Irish Pteridosperm. 3) summarized account in Scott’s “Studies in Fossil Botany ” (vol. ii, 1909), in which work references to the general literature of the subject will be found. Lyginodendron possessed a branching stem not more than 4 em. in diameter, armed with hook-like emergences, like a scrambling bramble. The leaves were large and compound, being bi- to tri-pinnate. Hmergences were present on the leaf in all its parts, and appear in the pinnule impressions as tubercles, occasionally, years ago, mistaken for sori. The pinnules were slightly stalked, and divided into three or four conchoidal, rounded, slightly lobed segments. A main vein enters each pinnule segment, passes through it, sending off branches at a wide angle, which, like it, may on their way to the edge of the segment branch, i.e. the venation is pinnate with diverging branches. The stem is characterized by a vertical reticulum of sclerotic bands running in the outer cortex. The vascular system is most interesting. The stem shows an interrupted ring of vascular bundles, enclosing a pith. Hach bundle is collateral and mesarch, as is the vascular bundle of the Cycad petiole, and, in some eases, of the Cycad peduncle also. ‘The bundle is open so that secondary thickening occurred, as in Cycads. Both metaxylem and secondary xylem show trachew with multiseriate bordered pits, also asin Cycads. Thus, while the arrangement of the bundles is like that of such a fern as Osmunda, the other characters are Cycadean. ‘The leaf-trace system is also Cycadean in its course, but becomes fern-like in structure and in the mode of branching in the foliage. The venation of the pinnule is very like that of Zirichomanes radicans, without serving in this case as a sign of affinity. The adventitious roots, Kaloxylon Hovkeri, have a primary structure like that of a rcot of Angiopteris evecta, or other Marattiaceous Fern, but show, superadded to this, secondary thickening as seen in the root of a Cycad. Thus the vegetative organs alone indicated clearly, as is now generally admitted, that Lyginodendron was a member of the Cycado-Filices. For some years this new group rested for its justification on the characters of the vegetative organs of its representatives. It was not until 1903 that any knowledge of its reproductive organs was obtained. REPRODUCTIVE ORGANS. Male.—A species of Crossotheca, founded in 1883 by Zeiller as a dimorphic Marattiaceous genus, possessing sterile Sphenopteris-like fronds and peculiar fertile ones, was shown by Kidston in 1905 to be the male state of Lygino- dendyon, and was named by him Crossotheca Héninghaust.’ A fertile male 1 This name will probably replace the now well-established name Lyginodendron Oldhamium, Willm., for our fossil, owing to Kidston’s discovery. A 2 4 Serentific Proceedings, Royal Dublin Society. pinnule consists of a short rachis bearing six or seven lateral, alternating arms, each ending in a disk-like expansion, the underside of which bears an epaulette-like ‘fringe’ of pendent finger-like bilocular pollen-sacs or bisporangiate synangia. Dehiscence of the pollen-sac was longitudinal, and the pollen-grains or microspores were tetrahedrally arranged. There is nothing in its structure to prevent the male pinnule from being described as a naked, branched rachis bearing groups of sori of synangia. The foliar nature of the structure is obvious. Female.—Lyginodendron is characterized by the presence on its stem and all parts of its leaf of the bramble-like prickles or hooked emergences already mentioned, and of stalked glands. EF. W. Oliver was struck by the similarity of these glands to those observable on a seed found in the same deposits (Coal Measures), and known as Lagenostoma Lomaxi, Willm., MS. With D. H. Scott he published in 1903 a detailed account of the internal structure of this seed, which presents, it was found, characters indicating close affinity with the seed of a Cycad. Nothing but evidence of direct continuity between this seed and the vegetative organs of Lyginodendron was lacking; and Oliver and Scott accordingly felt justified in concluding that Lagenostoma Lomaxi was the seed! of Lyginodendion, and that it had become detached before it was ripe, as occurs in some Cycads and in Gnetwm Gnemon® to-day. Another feature of Lagenostoma Lomazvi is the presence of a cupule-like envelope, which has been compared to the husk of a hazel-nut. This envelope consists of some six lobes united below and free above. Hach lobe shows on its outer surface the glands already mentioned. Naturally a search was made to discover anything more indicative if possible of the con- nexion between this isolated seed and Lyginodendron. Now, in 1875 Stur published the first part of his great work on the Culm Flora, and there figured certain bodies as “indusia spuria,” suggesting that they were the five- to six-rayed indusial lobes of some fern. In 1877 he published the second part of his work, and in it was able to assign his “indusia spuria” definitely to a fossil fern, Calymmatotheca. In 1883 he went still further, and described several species of Calymmatotheca, showing a gradual diminution in size of the indusial lobes. One of these—C. Stangeri—shows on the indusial lobes emergences which suggested to Scott and Oliver that C. Stangeri represented a fertile frond of Lyginodendron oldhamium from which the seeds had been shed. A difficulty militating against the acceptance of the idea of the complete identity of the two is the fact that the Z. Lomaai seed carried its cupular lobes on it, and that in C. Stanger the lobes remain on the parent 1 It was this discovery that caused these authors to found the group Pteridospermee, to include seed-bearing Cycadofilices. ? Lotsy : Vortrage u. bot. Stammesgeschichte, Bd. ii., 1909, p. 716. Jounson—A Seed-bearing Irish Pteridosperm. 5 plaut. It must Le remembered, however, that L. oldhamium is regarded as representing rather a type than a species. Further, so many different types of Lagenostoma seeds—some quite naked—have been found since 1903 that Grand’ Eury concludes that the Pteridospermes (as those forms of the Cyeado-filices found bearing seeds are now called) possessed foliage which is more or less uniform in its characters with seeds showing considerable variety—that, in fact, for every form of foliage there were two or three different types of seed. Grand’ Eury himself observed in the Lower Coal Measures of Brittany fronds of S. Dubuissonis! Bret., a species closely allied to S. Honinghausi, and in the same layers seeds, some naked, and others enveloped, like Z. Lomavi, with eupular lobes. In addition he found the C. Stangeri condition—i.e. cupules, formed of five or six lobes, attached to the ends of slender branches of the naked rachis. He did not, however, as he informs me by letter, find the seed itself enclosed by its cupule, and at the same time attached to the branching rachis, in continuity with the Sphenopteris foliage. In connexion with the attempt to associate C. Stangeri with Lyginodendron an apparently overlooked paragraph in Stur’s Introduction to his work on the Culm Flora? is so pertinent as to deserve notice here and quotation also on account of its general interest :— “Den Maasstab einerseits fiir die Grosse der stufenweisen Verinderungen einer bestimmten morphologischen Higenthtimiichkeit des Individuums, anderseits fiir die Lange der Zeit, die verfliessen musste, um eine solche Veranderung als geschehen und durchgefiihrt zu sehen, kann ich nur dadurch zu erzielen hoffen, dass ich einen und denselben Pflansentypus [my italics] durch die tbereinander folgenden Schichten einer Ablagerung in die Lagen einer nachst jiingeren Schichtenreihe zu verfolgen mich bemiihe. In jenen Fallen, wo es gelungen ist, einen solechen Typus durch drei unmittelbar iibereinander folgende Schichtenreihen, wie den Farn-‘l'ypus, den ich im Dachschiefer Calymmotheca Falkenhaini, in den Ostrauer Schichten Calymmotheca Stanger, in den Schatzlarer Schichten Calymmotheca Honinghausi (Bet.) Andre genannt habe—zu verfolgen, da haben sich die Veranderungen dieses ‘l'ypus, die mit den drei Namen festgehalten werden, als gering erwiesen, die nur mit Miihe begreifbar dargestellt werden kénnen. Und die Veranderung besteht nur in der kaum merklichen, aber stufenweisen Verlingerung, eigentlich Indivi- dualisirung der Lappen der Spreitenabschnitte. Dabei hatte ich aber Gelegenheit zu beobachten dass die Calymmotheca Stangeri wahrend der Dauer _ 1 “Clearly,”’ said Stur in 1877, ‘‘ one of the Calymmatothece.”” 2 Abhandl. d. k.k. geol. Reichsanstalt zu Wien, Band yiii., 1875-77. Vorwort z. Bande: Die Culm-Flora, von D. Stur, p. x. 6 Scientifie Proceedings, Royal Dublin Society. der Ablagerung dreier (111-V) Flotzgruppen der Ostrauer Schichten sich gleichblieb. “ Hs fallt somit hier zwischen jenem momentanen Zustand des Typus, den ich als Calymmotheca Stangeri bezeichnet habe, und dem nachst jingeren, die Calymmotheca Honinghausi, jene Licke, die zwischen der Ablagerung der Ostrauer Schichten und der Schatzlarer Schichten besteht. In diese fallt die Vollbringung der gréssten bemerkbaren Verschiedenheit zwischen den beiden genannten Pflanzenresten, d.h. wahrend der Dauer dieser Zeitlticke muss die Veranderung der C. Séangeri in die C. Honinghausi stattgehabt haben.” Thus Stur mentions three species—O. Fulkenhaini, C. Stangeri, C. Honinghausit, which gradually change in the order named from one to the other in the ascending Culm strata—and states that they are all so closely allied as to be really not more than varieties of one and the same type, though he gives them specific names. ‘They only differ in the gradual, scarcely perceptible elongation of the pinnule segments. As C. Honing- hausi—i.e. S. Honinghausi—is, we know from Kidston, the foliage of Lygino- dendron, the transition from C. Stangeri to it is slight, and the identification of C. Stangeri, with its indusial lobes, as the fertile but seedless frond of Lyginodendron is amply justified. Recently, in the course of rearrangement of the collection of fossil plants in the Botanical Division of the National Museum, my first object was to see to what extent the newly founded group of the Pteridospermes was represented in the collection. I first of all examined all the forms of Sphenopteris, and especially two specimens which were labelled with a query, Sphenopteris Honinghausi, from the Coal Measures of Glengoole, County Tipperary. ‘The different forms of Sphenopteris were compared with those in the collection of the Geological Survey of Ireland, also housed in the National Museum, and under the charge of Professor Grenville Cole, Director of the Survey. As the result of a detailed comparison, I came to the conclusion that the two specimens of Sphenopteris just mentioned were true S. Honing- haust; and in one of them I saw characters of a fertile condition suggestive of the described characters of Calymmatotheca Stangeri. In a specimen of Sphenopteris Honinghausi in the Geological Survey collection the C. Stangert condition was unmistakably present (Plate I., fig. 1). The specimen presents a further feature of interest. Not only are the indusial lobes observable, but in the midst of these, at one point certainly, and at other points’ doubtfully, one can see, with a magnification of 45, every indication that a seed is present. ‘hus we have here, so far as one may judge from a carbonized impression, if my interpretation is correct, that direct con- tinuity between the vegetative organs of Lyginodendron oldhamium, the Jounson—A Seed-bearing Irish Pteridosperm. 7 Culymmatotheca fertile rachis and the Lagenostoma seed, for which we are prepared by the researches already mentioned. Such organic continuity of seed with parent plant was first observed in a Pteridosperm by Kidston in 1904 in Newropteris heterophylla, 1903 being the year in which the first Pteridosperm seed—Lagenostoma—was identified as such. The photograph in Plate I, fig. 1, represents the impression of the seed- bearing specimen in the Geological Survey collection, little less than natural size (4). ‘The main stalk or stem,’ 1 em. in width, shows beautifully (fig. 2) the sclerotic network characteristic of L. oldhamium, as well as the spinous emergences. The bifurcated rachis is readily recognizable. This is so general in these Carboniferous “‘ Ferns” as to lose all generic value. (‘Lhe genus Diplotmema founded by Stur to include forms with bifurcated yachis is unnatural.) The foliage is typical of S. Honinghausi (Plate I., fig. 1), showing the pinnules with lobed conchoidal, rounded segments, and branched, diverging, non-parallel venation. ‘lhe hooked emergences are visible on the rachis, and appear on the pinnule segments (Plate IT., fiz. 4) as small bosses or tubercles. The rounded form of the pinnule segments of S. Honinghausi is of some interest. On looking over a large number of species of Sphenopteris, it is possible to divide them into two main series. In the one represented by “S. Honinghausi,” the pinnule segments have a more or less rounded outline, and their branching veins diverge from one another, and from the main vein which forms -a sort of midrib to the segment. In the otlier series, represented by S. elegans, the pinnule segments are not rounded in outline. ‘They are wedge-shaped or roughly comparable to an inverted isosceles triangle, of which, in some forms, the base is very narrow. The veins of the pinnule segment, with or without bifurcation, do not, however, diverge widely from one another, but run parallel or sub-parallel to one another. In the S. Honinghausi series the rounded segments show pinnate diverging venation, and in the S. e/egans the cuneiform segments show dichotomous or bifurcated sub-parallel venation. The impor- tance of this distinction is illustrated in Lotsy’s valuable “ Vortrage iiber botanische Stammesgeschichte,” where fig. 499 (page 708), an illustration (after Potonié) of S. Héninghausi, shows the more or less triangular or cuneiform pinnule segments of the S. elegans type, and is recognizable by the transverse striz of the rachis observable in the figure, as actually S. elegans—i.e. Heterangium Grievii, Willm., another and earlier Pteridosperm. I am well aware of the possible pitfall in using venation as a test of affinity ; but it is of interest to note that the subparallel dichotomous type 1 Though the impression indicates by its characters that this is a piece of the stem, it must be remembered that the chief rachis has been found 3 em. wide, and the whole leaf 2 to 3 m. long. 8 Scientific Proceedings, Royal Dublin Society. of venation is that found not only in Heterangium Grievii (S. elegans), which makes its appearance in the rocks earlier than LZ. oldhamium, but that it is also characteristic of the still earlier forms Archwopteris Hibernica (Forbes), and Sphenopteris Hookeri! (Bailey), of the Upper Devonian or Yellow Sand- stone beds of Kilkenny. In my preliminary examination of the fertile specimen of 8S. Honinghausi, I thought it was sterile, and made rough notes to that effect. A detailed examination showed, after a time, that it was fertile, as Plate IT., fig. 1, which may serve as a key to Plate I., fig. 1, indicates. At the base of the bifurcated rachis there is a highly suggestive star-like group of radiating lobes, reminding one of the cupular lobes of C. Stangeri..-The hand-lens will reveal in Plate I., fig. 1, similar groups at various points. The most important is that at 6. In continuity with the rachis (7), itself in direct connexion with the stem (s), there is a branched naked rachis on which, at intervals, are groups of radiating lobes which agree with those figured in C. Stangeri, and now regarded as the cupular lobes of the Tagenostoma seed. In Plate Il, fig. 5, the venation of one of these lobes is shown, as far as traceable in the impression. Plate IT., fig. 6, gives a general view of the branching rachis and of one cupular group. In Plate IIL, fig. 1, the basal part of a portion of this group is shown in more detail. In both these figures there is recognizable a difference in the character of the individual lobes of a group. Five are more or less alike, oblong-linear in outline with the venation as shown in Plate IL, fig. 5; but the sixth lobe is broader and its venation different. By its basal venation it would pass well for a pinnule segment. The chief point of interest in the specimen under description is the continuity of the parts and the presence in one case (Plate IIl., fig. 2) of a seed within the spreading cupular lobes. The impression of the seed shows it to have been of the radiospermic type, 6 mm. long and 2 mm. broad, elliptical or barrel-like in shape, with suggestions of slight longitudinal ridges. In some respects it is not unlike Lagenostoma Iidstoni, Arber, and confirms the view that the seeds in the Lyginodendree occurred isolated on the tips of naked branches of the rachis, and not in strobili. In discussing the position of the seed Lagenostoma, Oliver and Scott state that the foliage of Lyginodendron, shown by Kidston to be Sphenopteris Honinghausi, had been found in the sterile form only. ‘hey admit that Stur’s attribution of the fertile condition— Calymmatotheca Stangerito the allied species Sphenopteris Stangeri may be correct, though actual continuity was wanting. Our specimen is very satis- 1 Nathorst (Zur Oberdevonischen Floia d. Baren-Insel, p. 14) in describing Sphenopteris Hookeri, Baily, as possessing a distinct midrib, must haye been misled by the figures, Jounson—A Seed-bearing Irish Pteridosperm. 9 factory in that it not only supports Kidston’s identification of S. Honinghausi as the foliage of Lyginodendron oldhamium, but shows also, by the evidence of direct continuity, that Calymmatotheca Stangeri is the fertile female frond of Lyginodendron, and that it enclosed in its tuft of cupular lobes a seed most closely allied to, if not identical with, the fully described Lagenostoma Lomazt. If this view be accepted, the synthetic reconstruction of Lyginodendron old- hamium, as an example of an extinct Paleozoic Pteridosperm, is completed. A feature that strikes one in reading the accounts of the male and female organs of these Paleozoic Pteridosperms is the marked degree of divergent differentiation aiready attained in the characters of the two. Theoretically one would expect them to show, in some features common to both, signs of their origin from a type represented in the sporangial sori of some primitive fern. Yet the contrast between the male organs of the Crossotheca type and the female ones represented by Zagenostoma shows that the differentiation had already proceeded far in Lyginodendron. In this connexion our specimen presents an interesting feature, reproduced in Plate III., fig. 5. In an other- wise normal pinnule two of the segment-lobes have become elongated and in all respects like the cupular lobes. ‘Ihese I regard as signs of commencing fertility on the part of the pinnule in question, and also as indicative, if further indication is necessary, of the foliar nature of the cupular lobes found surrounding the seed. The seed itself, indeed (Plate III., fig. 3), might easily pass for a cupular lobe on casual inspection, and is, in reality, I think, a foliar lobe transformed into a seed—ie. it is an ovule- or macrosporangium- bearing foliar segment. Looked at in this way the difference between the male and female is not so great as appears to be the case at first sight. In the case of the male the pinnule becomes fertile and forms five or six bilocular microsporangia on the underside of the expanded apex of each of the transformed segments of the pinnule. In the female the five or six segments of the fertile pinnule become ligulate, or flattened and ribbon- like, and envelop more or less one lobe which becomes stouter than the others and forms an ovule or macrosporangium. ‘The enveloping lobes may fuse more or less together to form the protecting cupule, but appear homologous with the ovuliferous lobe. If this view be correct, there is nothing to prevent the conversion of other cupular or foliar lobes into ovules, leading to the occurrence of two or more ovules in one terminal rosette of the naked branch of the rachis. ‘here is, however, one difference which one finds so frequently in plants, viz.an abundant development of the male organs, giving many microsporangia and microspores, and a small development of the female; in this case, solitary macrosporangia or ovules, isolated, on branches of the rachis. Both male and female sporangiophores are foliar in nature. SCIENT. PROC., R.D.S., VOL. XIII., NO. I. B 10 Scientific Proceedings, Royal Dublin Society. The male pinnule of Kidston’s Crossotheca Honinghausi is homologous with the female pinnule of Calymmatotheca Stangeri. They both represent Lyginodendion oldhamium in a fertile state. In Plate ITI., fig. 6, I have attempted to show by means of diagrams what appear to me to be the homologies of the sterile male and female parts of Lyginodendron. ach slightly stalked segment of the sterile pinnule (a) has in the male (2) concentrated its energy, not into the formation of a broad lamina, but of a naked stalk, carrying on its discoid tip a group of pendulous hisporangiate synangia, i.e. bilocular pollen-sacs, (Crossotheca). In (¢) the condition is comparable to that in (0); but only one of the terminal lobes is fertile. This becomes the seed; and the other lobes (though potential seeds ?) form a protecting envelope to the fertile lobe. On this interpretation the bilocular pollen-sacs and the seed are homologous with one another and with the pinnule segments or their lobes. Goeppert, in his ‘‘ Die Gattungen der fossilen Pflanzen,” describes and figures a species of Sphenopteris as S. spinosa, characterized by elongated foliar lobes similar to those I have just mentioned as present in our specimen of L. oldhamium. The digitiform processes are not found on all parts of the frond, and Goeppert explains this by saying they had there been already broken off. My explanation is that S. spnosa is really a Sphenopteris in a state of commencing fertility. Von Zittel’ states that Lesquereux? was the first to observe the mode of fructification typified in C. Stangeri, in the Carboniferous fern Staphylopteris. Stur described the star-shaped bodies as indusial lobes, within which the receptacle of sporangia could not be seen. Lesquereux, von Zittel, Zeiller, and Renault all described the lobes as the actual sporangia. Iam of opinion that Hugh Miller? had the bodies before him in 1857 in Parka decipiens of Fleming, when, treating them as of an unknown nature, he compared their appearance to that presented by the rayed calyx and fruits of a crushed bramble. It would be of interest if the specimens could be re-examined in the light of the evidence of the last few years on Pteridosperm seeds. SumMMARY. 1. The Palzeozoie group of Pteridospermee flourished in Ireland. 2. The Museum specimens of Sphenopteris Honinyhausi confirm the view, if such confirmation is necessary, that this ‘‘ Fern” is in reality the foliage of the Pieridosperm Lyginodendron oldhamium, Willm. (Crossotheca Héning- hausi, Kidst.). 1K. A. von Zittel: Traité de Paléontologie, ii., p. 106. * L. Lesquereux ; Palaeontology of Ilinois, vol. iv. > Hugh Miller: ‘‘ Testimony of tle Rocks,’’ 1857, fig. 121, p. 448. Jonnson—A Seed-bearing Irish Pteridosperm. 11 3. Calymmatotheca Stangert, Stur, described by Stur himself as, at the most, a variety of C. Honinghausi, occurs in continuity with S. Honinghausi, i.e. Lyginodendron oldhamium, and is simply the de-seminated fertile frond of this type. 4. In the Irish specimen described from the Coal Measures, Glengoole, County Tipperary, a seed, judging from the carbonaceous impression, is present, still attached to the parent plant, and seated in the midst of the radiating cupular lobes. 5. This seed, as far as can be ascertained, presents the usual characters of a Lagenostoma seed. It is 6 mm. long and 2.mm. broad, radiospermic, elliptic, and apparently ridged. 6. The “ S. spinosa” condition shows that the eupular lobes are modified foliar segments, as is apparently the ovuliferous body. 7. The male (Crossotheca) and female (Calymmatotheca) conditions are foliar in nature, and present many features in common. EXPLANATION OF PLATE I. PLATE I. CrossorHeca Hoéninenausi, Kidston. (LieinopENDRoN oLpHamium, Williamson.) Fic. 1. An imperfect specimen (# natural size). See Plate II., fig. 1, for explanation. -- 2. Part of fig. 1, showing seed-region (enlarged). (From photographs by T. Price.) Scient. Proc. R.Dubl. Soc, N.S Vol. XII. Plate 1. Bemrose,Lt¢Derby. Arges ue EXPLANATION OF PLATE II. PLATE II. Crossoturca Hoénineuausi, Midston. (LeinopENDRON oLpHAMIUM, Wéalliamson.) Fic. 1. Diagram explanatory of Plate I., fig.1. s, stem, 1 cm. wide, showing sclerotic strands and a few emergences. 7, rachis attached to stem, and having in continuity with it the Calymmatotheca condition, b. 2. Surface view of the stem, showing the sclerotic network and the hook- like emergences. Magnified. 3. Diagrams to show (a) the relation of the pinnule segments to one another, (6) the pinnate venation and the lobation of a segment. Slightly magnified. 4. Pinnule segment, showing the venation and a few of the emergences as seen in surface view. Magnified. 5. A portion of a cupular lobe, showing the venation. Magnified. 6. A cupular lobe rosette and adjoining parts, 7, rachis. Magnified. PLATE I. Ney WO, SOUT, SCIENT. PROC. R. DUBL. SOC., Rony EXPLANATION OF PLATE III. PLATE III. Crossotueca Honincuausi, Kidston. (LyainopenprRon otpHamium, Williamson.) Fic. 1. Part of Plate IL., fig. 6, ¢1, ¢2,¢8, to show the venation. Magnified. 2. Calymmatotheca condition, in continuity with the rachis r of Lygino- dendron. The seed o is shown attached to the naked rachis branch, surrounded at its tip by cupular lobes. The proximal end of the seed only was at first observable, and the convexity was broken across ate. By dissection under the microscope the distal end was laid bare and the elliptic shape recognized. ¢ and d are two grooves on opposite sides of the seed. The surface of the proximal end of the seed has a slazed appearance, due to the deposit of iron pyrites, observable elsewhere also in the specimen. ‘The regions a and 6b are well carbonized, and suggest the testa. At b especially the testa seems clearly distinguishable. 8. The seed and its cupular lobes. Magnified. 4. A cupular rosette. Magnified. 7, rachis, c, ec, cupular lobes. s, seed? Venation shown. 5. A pinnule, showing commencing fertility. Two of the segments of the pinnule are converted into ligulate cupule-like lobes, f. P represents the points of insertion of other pinnules, d the normal point of insertion of a pinnule. The rachis in the specimen is naked here, thus giving another sign of the beginning ofconversion into a fertile state. Magnified. 6. Diagrammatic representation of sterile (a), male (b), and female (c) pinnules for comparison of homologies. The lobed sterile segments of the pinnule @ are converted into the fertile male segments of the branch (d), each with its group of pendulous bilocular pollen sacs or microsporangia, and into the fertile female segments of the branch (c), each with its single seed enclosed by five or six cupular lobes. SCIENT. PROC. R. DUBL. SOC., N.S., VOL. XIII. PLATE III. NaN rn Ear ON, OA Doh st ia Ad é i 4 SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1. A Seed-Bearing Ivish Pteridosperm, Crossotheca Héninghaust, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. 2. Considerations and Experiments on the supposed Infection of the Potato Crop. with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcz H. Petuysrimce, D.SC., PH.D. (March, 1911.) 1s. DUBLIN: PRINTED ALT THR UNIVERSITY PRESS BY PONSONBY AND GIBBS- THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIIL. (N.S.), No. 2. MARCH, 1911. CONSIDERATIONS AND EXPERIMENTS on Tue SUPPOSED INFECTION or tue POTATO CROP with THE BLIGHT FUNGUS (PHYTOPHTHORA INFESTANS) sy MEANS or MYCELIUM DERIVED DIRECTLY From tours PLANTED TUBERS. BY GHEORGHE H. PETHYBRIDGE, B.Sc., Px.D., ECONOMIC BOTANIST TO THE DEPARTMENT OF AGRICULTURE AND TECHNICAL INSTRUCTION FOR IRELAND. [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, . LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, ae Pn : Koon Price One Shilling. N Rapid Roval Dublin Society. OOO FOUNDED, A.D. 1781. INCORPORATED, 1749 EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. Jounson—A Seed-bearing Irish Pteridosperm. 11 3. Calymmatotheca Stangeri, Stur, described by Stur himself as, at the most, a variety of C. Honinghaus/, occurs in continuity with S. Honinghaust, i.e. Lyginodendron oldhamium, and is simply the de-seminated fertile frond of this type. 4, In the Irish specimen described from the Coal Measures, Glengoole, County Tipperary, a seed, judging from the carbonaceous impression, is present, still attached to the parent plant, and seated in the midst of the radiating cupular lobes. 5. This seed, as far as can be ascertained, presents the usual characters of a Lagenostoma seed. It is 6 mm. long and 2 mm. broad, radiospermic, elliptic, and apparently ridged. 6. The “ S. spinosa” condition shows that the cupular lobes are modified foliar segments, as is apparently the ovuliferous body. 7. The male (Crossotheca) and female (Calymmutotheca) conditions are foliar in nature, and present many features in common, SCIEN. PROC., R.D.S., VOL. XII., NO, I. c Cw Il. CONSIDERATIONS AND EXPERIMENTS ON THE SUPPOSED INFECTION OF THE POTATO CROP WITH THE BLIGHT FUNGUS (PHYTOPHTHORA INFESTANS) BY MEANS OF MYCELIUM DERIVED DIRECTLY FROM THE PLANTED TUBERS. By GEORGE H. PETHYBRIDGH, B.S8c., Px.D., Economic Botanist to the Department of Agricuiture and ‘echnical Instruction for Ireland. [Read Decemprr 20, 1910. Ordered for Publication January 10. Published Marcu 6, 1911.] Ir is now well over half a century since the potato blight became an epidemic disease in Europe. During the latter half of this period the practice of spraying the crop with some preparation of copper has become more and more prevalent as a preventive measure against this disease, until at the present time, in Ireland at least, spraying is generally regarded as an essential item in the cultivation of the potato crop, experience having proved its effectiveness and its necessity. During the same period, however, comparatively little attention has been devoted to the extension of our knowledge of the fungus Phytophthora infestans which causes the disease; and we are not yet in a position to say that its life-history is completely known, although there are signs that the study of it is once more being resumed in earnest. In one fundamental point, in particular, we are still almost completely in the dark, and that is as to the manner in which the potato-plants first become infected each succeeding season. We do know that, during the summer, “ spores’ cause the spread of the disease from plant to plant during that season, but which are ephemeral, and are incapable of living over the winter from one season to the next. Judging from analogy, we should expect to find a second form of spore, formed sexually, and provided with a thick wall, and thus capable of living, probably in the soil, over the winter, and germinating in the following summer. If, however, we except Worthington Smith’s work (2)! on this branch of the subject, which, although extremely suggestive, has not ? are produced which 1 The numbers refer to the Bibliography at the end of the Paper. PeruysripGe—Lzperiments with Phytophthora. 13 obtained general acceptance at the hands of mycologists, and has up to the present not been confirmed by any other worker, success has not yet crowned the comparatively few efforts which have been made to discover such spores. Nevertheless, a more extended and patient search may even yet reveal them. ‘The writer, for instance, has found spores in potato foliage destroyed by Phytophthora which, judged from a morphological standpoint, might easily be regarded as the oospores of this fungus, but which, although experimented with in very various ways over a period of six months, could not be induced to germinate, and so to reveal theirnature. Resting-spores in this case, therefore, must be said to. be unknown, but their existence is by no means improbable. We also know with certainty that the fungus is found in the form of spawn, or mycelium, within the tubers, and that in them in this. form it can pass the winter successfully ; indeed, this is the only way, so far as we know at present, in which the fungus can live over the winter. Hence it would appear that, in the absence of resting-spores, diseased tubers must be the ultimate source from which the blight starts anew in any given season. The question now arises as to exactly how infection of a new crop can occur from the diseased tubers of a former one. It is a well-known and easily demonstrable fact that the mycelium in diseased tubers produces at any time, provided the latter are placed in conditions of moderate warmth and moisture, a crop of “spores” on branched hyphae, which grow out from the tubers into the surrounding air. Should “spores” be produced from such a source above ground when the potato plant is in foliage, infection is likely to occur. Even if below ground, there is just the remote chance that such spores might be brought above it by the action of worms, &e. Hence particularly on small farms, where the newly planted crop will not be far away from last year’s ground, or last year’s pit, around which some diseased tubers are almost certain to be found lying about, there is some probability that infection may occur in this way. But since it seems probable that the chances of infection in this way are not sufficiently wide- spread to explain the constant recurrence of the blight, other possible sources of infection have been sought for, and recently the view that the potato plants become infected in the field directly from the planted tubers by means of mycelium, and not by ‘“spores,’’ has been revived; and the object of the present paper is to consider whether this view is supported by any substantial evidence and can be accepted as proved. When a potato tuber is affected with Phytophthora, it shows certain characteristic external markings which proclaim the fact. Should there be any doubt in the matter, it is easy to induce the formation of the well-known c2 14 Scientific Proceedings, Royal Dublin Society. ‘spores,’ and settle it. When cut through, characteristic internal markings are also present, in the form of rusty-brown areas, confined in the earlier stages to the tissues near the skin. It is in these discoloured areas that the fungus mycelium is then to be found. If such tubers be carefully watched during the winter, it will be seen that the sprouts frequently begin to develop much earlier than on healthy tubers, as is also the case with tubers mechanically wounded, that the internal browning of the tissues gradually becomes more and more extended inwards through the tissues, and that the whole tuber becomes gradually destroyed. There is a race set up between the destroying fungus on the one hand, and the still-living part of the tuber on the other, and, in a very large percentage of cases, probably much more than half of them, the fungus gains the victory, and the tuber becomes entirely killed. On its surface, whitish pustules may often be seen, which, in some instances at least, are due to fungi other than that causing the blight. It is to be noted that there is little question of a resting period at all for the potato, and much less for the fungus. Both are active, although naturally the degree of activity depends to a certain extent on external conditions, particularly temperature. If this be raised, the activity is increased ; if it fall, it is diminished. If the tuber wins the race, that is if it reaches planting-time, say in March or April, with some still healthy sprouts upon it, and a portion of its tissues still sound, this is largely because the attack was in the first place a slight one, or the tuber was perhaps large, and the distance from the attacked parts to the sprouts great, or possibly because it was kept at a comparatively low temperature, so that the fungus progressed but slowly. To have reached planting-time with one or two sound sprouts, and a portion of the tuber still healthy, is, however, only the end of the first lap in the race. When such partially diseased tubers are planted in the soil, the moisture and warmth present there cause it to be resumed with renewed vigour. Experiments show that in a very large number of such cases no plant at all comes above ground, the tubers and their sprouts, if any, becoming completely killed before this is possible. In a few cases, however, the tubers do succeed in sending small shoots above ground, but these, after a very short time, suecumb to the fungus which undoubtedly does grow up into them from the diseased tubers. In the remaining cases, contrary perhaps to what would be expected, the tubers, though originally diseased, give rise to what appear to be perfectly healthy plants, that is plants free from Phytophthora, although they may be somewhat less sturdy than plants grown from healthy tubers. Here, then, the potato plant has won the race against the fungus; for the sprouts develop and grow into healthy stalks, independent of the parent set Pernysripge— Experiments with Phytophthora. 15 for nutrition, before the fungus has been able to invadethem. Such plants, of course, may become attacked with the blight in the ordinary way by means of aerially borne spores later on. Shortly summarized, therefore, it may be said of diseased tubers that they may— (1) die before planting-time ; (2) die if planted in the ground, without producing any overground stalks ; (8) produce small stalks above ground which soon die owing to direct infection with the fungus from the parent tuber ; (4) produce healthy plants, which, provided there be no opportunity during the season of becoming infected by aerially borne “ spores,” remain free from the disease. With regard to the tubers which are killed before planting-time, these can scarcely become a source of infection to the new crop. For, even if left lying about above ground, they will probably be no longer capable of giving rise to ‘‘spores” by the time that the new foliage has developed. The case of those tubers which are not actually dead at planting-time is, however, somewhat different. These, if too obviously diseased to be used as “seed,” may be left lying about, and may still be capable of producing “spores ” under suitable conditions when the new foliage has developed, and they would therefore be a source of danger to the ensuing crop. Little danger is to be feared from any tubers which, being badly diseased, are planted and produce nothing above ground, for the chances of any “spores” which may have been formed on the tuber below ground finding their way in a living condition to the surface are but small. On the other hand, tubers which produce small diseased shoots above ground may be highly dangerous sources of infection, for on these shoots “spores’’ are produced which can easily be carried to neighbouring healthy plants. There is, therefore, no question but that ina few cases tle mycelium in a diseased tuber may succeed in reaching a shoot which has got above ground; but this takes place comparatively early, and such shoots are soon killed off. This early killing off of young shoots by invasion of mycelium from the tubers is, however, a very different thing from the supposed infection of well-grown plauts by such mycelium some two or three months later in the season. If this actually occurs, the mycelium must be supposed to be growing with almost inconceivable slowness, or to be lying in a dormant condition during this period while these apparently healthy plants are developing. ‘The recently propounded theory of mycelial infection to be discussed in this paper 16 Scientifie Proceedings, Royal Dublin Society. involves the view that the mycelium becomes dormant for a period and then resumes its activity. ‘ é The chief advocate of the theory, which, on the face of it, as will be presently shown, has little to reeommend it, is Massee (7), whose most recently published views may be summarized as follows :—When a diseased tuber is planted, the produce of such a tuber is always diseased; yet under certain conditions of weather (in bright, dry seasons) the stem and leaves of the plant may remain perfectly free from the disease. On the other hand, during afew cloudy, damp, sultry days in July the mycelium will take possession of the stem and leaves, which will succumb within a few days. The fact that simultaneous outbreaks of an epidemic may occur, extending over wide areas, is considered to be best explicable in this way. According to this view, then, not only does the mycelium of Phytophthora he dormant in the tubers during the winter, but also during the long period - from planting-time—say, in March—until the time of the appearance of the blight in June or July. Incidentally it may be remarked that it is difficult to see how the produce of a diseased tuber can be diseased if at the same time the mycelium is lying dormant in the tuber; and the theory apparently states that, unless a season of unfavourable weather sets in, the stem and leaves remain free from the disease, and therefore in an exceptionally dry summer the produce from a diseased tuber would not be diseased ! My own observations of the behaviour of diseased tubers during the winter lead me to believe that even then the mycelium in them is not in a true state of hibernation or dormancy. During this period certain changes are going on; the tuber itself is slowly sprouting, and the mycelium invading fresh, healthy tissue at a rate depending largely upon the tem- perature at which the tubers are kept. But even if it is admitted that the mycelium in the tubers is dormant during the winter, it is almost impossible to entertain the idea that, when the tuber is planted, it still remains dormant. Surely planting the tuber in moist soil, which is also often considerably warmer than the surrounding air, would, if anything, encourage the mycelium to more active growth than before, rather than cause it to remain in, or take on, a latent condition! Another strong argument against the acceptance of this theory is that, according to it, the attack of the stalks must proceed from below upwards, whereas the exact contrary is what is actually found to take place in the fields. On healthy plants the blight always appears first as spots on the leaves or on the upper parts of the stalk or its branches, and never in the form of decay at its base. Even if the mycelium did lie dormant in the tubers, it must, to produce such spots, grow up through the stalks to reach such places ; and how could it possibly do this PrernyBripGE—Lzperiments with Phytophthora. U7 without affecting the tissues of the stalk and its branches? It is impossible to understand how this could occur without some indication of it being given by the wilting or other abnormal behaviour of the stalks and foliage, such as occurs in cases of Black Stalk Rot, Leaf Roll, &c.; but no such phenomena have ever been observed in the case of attacks by Phytophthora, Anyone who is acquainted with the history of the numerous investigations which have been carried out on this disease during the past fifty years must know that experiments have proved that from diseased tubers perfectly healthy plants may be produced, which, provided they are kept free from all means of external infection by means of spores, remain unattacked through- out the season. Indeed, long ago the Prussian Government set the problem as to whether healthy or diseased plants were produced from diseased tubers, for solution to a body of scientific men on the staffs of its Agricultural Academies and Experimental Stations, with the result that it was found that diseased tubers produced healthy plants. Experiments carried out by Professor Carroll and the late Professor Wright at the Albert Agricultural Institution, Glasnevin, gave a similar result ; and my own experiments, which will be dealt with presently, prove the same thing, so that there is no necessity to labour this point. And it is not impossible or even difficult to explain how this can be the case. ‘Those who have studied and experimented with diseased tubers know how comparatively ephemeral the growth of Phytophthora on them is when they are kept in moist warm air, and how comparatively soon the growth of Phytophthora is over, and such tubers or pieces of them become swamped with growths of other fungi and bacteria, and become completely destroyed. When such a tuber is in the soil during the period from March till June or July, there is even more chance of this taking place. Meanwhile, however, the sprouts, especially if well started at planting-time, have developed into healthy stalks independent of the parent set. _ Sufficient has now, I think, been said to show that, on a priori grounds, the theory of infection from dormant mycelium is a most improbable one. Hence it becomes necessary to examine carefully the evidence on which it is based. This, given in its chief upholder’s own words, is as follows :— “Three potatoes showing rusty stains in the flesh, indicating the presence of the mycelium of potato disease (Phytophthora infestans), were each cut into two equal parts. Hach half potato was planted separately in a plant-pot, the soil and manure used being the same for all, and was sterilized by steam. Three of the pots were placed in a house having a temperature ranging between 70° and 80° F., and very often with moisture at saturation point. Hach pot was covered with a bell-jar. The remaining three pots were placed 18 Scientific Proceedings, Royal Dublin Socicty. in a house without any artificial heat, and having the air exceptionally dry. These pots were not placed under bell-jars. An equal amount of water was supplied to each of the six pots. ‘The stems and leaves of the three plants grown under conditions of high temperature and much moisture were attenuated and weak. ‘The Phytophthora first appeared on these plants six weeks after planting; and a fortnight later all three plants were blackened and destroyed by the fungus. The potatoes grown in the cool, dry house were perfectly healthy when two months old. At this time one of the plants from the cool house was removed to the hot, damp house, and placed under a bell-jar. Within nine days this plant was completely blackened and killed by the fungus. A fortnight later a second potato plant, showing no indica- tion of disease, was removed from the cool to the hot house, and placed under a bell-jar; within a week this plant was also killed by the Phytophthora. The third plant was allowed to remain in the cool house, and at the end of thirteen weeks, when the experiment ended, showed no trace of disease.” As «a piece of scientific evidence in favour of the theory promulgated, this experi- ment is of course absolutely worthless, owing to the simple fact that no control plants derived from healthy tubers were used for purposes of comparison. The details given of the experiment are unfortunately all too few. The time of the year at which it was carried out is not stated, nor is the mode of attack, whether from below upwards or from the foliage downwards, described. There is absolutely no evidence produced to show that the plants were not attacked by “spores” in the ordinary way. It is of course conceivable that the three plants in the warm house did become diseased from mycelium from the tubers; but six weeks is, in my experience, a longer interval than usually elapses in such cases. But even if they did, this occurrence has no bearing on the idea of dormant mycelium. With regard to the two plants brought to the warm house from the cool one, what could be simpler than to suppose that they became infected from “spores” previously produced by the first three plants? There is not a particle of evidence to show that they did not become attacked from this source; and the view that this may have occurred is strengthened by the fact that the single plant which was left in the cool house did not become diseased. ‘There is a danger of laying far too much stress on abnormal weather-conditions as a necessity for the development of Phytophthora. For rapid growth and spread resulting in an epidemic un- doubtedly a spell of warm moist weather is almost a necessity ; but slow gradual development can occur under much less exacting conditions. I found, for instance, that infection and a comparatively slow but decided spread of the blight occurred on potted plants in an absolutely unheated greenhouse with a dry atmosphere even in the month of April, when the temperature PernysripGE—Lzperiments with Phytophthora. 19 ranged from about 38° to 57° F.; and it is quite possible that the third plant mentioned above, and left in the cool greenhouse, remained healthy, not because the conditions were unfavourable, but merely because ‘“‘ spores” were absent. At any rate there is no evidence against this view. Since the evidence in favour of the theory derived from the experiment described was of such an unsatisfactory nature, it seemed to me eminently desirable to carry out another one on similar lines, but with the addition of the absolutely necessary control plants. Starting in the early months of the year, in order to avoid any possible chance (at least in the early stages) of infection from aerially borne spores, I carried out an experiment of this kind which will now be described. I gladly avail myself of this opportunity of acknowledging with many thanks the assistance of my friend and colleague, Mr. F. W. Moore, M.A., Keeper of the Royal Botanic Gardens, Glasnevin, who was good enough to place at my disposal the necessary room in two of his glasshouses, and who afforded me other facilities for the work. The experiment was started on February 11th, and brought to a con- clusion on July 11th, 1910, and thus extended over five calendar months. Six potato-tubers of the variety “Champion” attacked by Phytophthora‘ were halved, thus making twelve sets in all. Six other tubers of the same variety, but perfectly healthy, were similarly cut into twelve sets. ‘Twenty-four pots were filled with virgin loam which had not been previously used for potting purposes. Of these, twelve were sterilized by heating for half an hour each in an autoclave at 120° C., the remaining twelve being untreated. Six diseased and six healthy sets were then planted in the twelve pots of sterilized soil and the same numbers planted in the twelve pots of unsterilized soil. No manure of any kind was used. Of the twenty-four pots (twelve containing diseased sets and twelve containing healthy ones as controls) six were placed at once in a warm greenhouse, the temperature of which ranged from a minimum of 60° F. at night with fire-heat, up to 85° F. in the daytime with sun-heat, or at least 65° F. with fire-heat on cold days, and the atmosphere of which was fully charged with moisture, so that the conditions for the development of Phytophthora were extremely favourable. ‘The soil in all these six cases had been sterilized, and three of the pots contained healthy sets, while the other three contained diseased ones. These pots were not covered at any time with bell-jars. The remaining six pots of sterilized soil with three healthy and three 1 Lest there should be any doubt in the matter as to whether these tubers were actually attacked by Phytophthora or not, it may be stated that I selected them personally from a severely diseased crop, and utilized the remainder of the batch not required for the experiment, for successful demon- stration of the fungus, after suitable incubation, by the members of a large class of agricultural students. SCIENT. PROC. R.D.S , VOL. XIIL., NO. Ll. D 20 Scientific Proceedings, Royal Dublin Society. diseased sets in them, together with the twelve pots of unsterilized soil con- taining six healthy and six diseased sets, were placed at the same time in a cool greenhouse with no artificial heat and with an exceptionally dry atmosphere. As regards the three healthy (control) and the three diseased sets in the warm house, two of the latter produced overground stalks after twelve days, while the third one, although left for some considerable time longer, did not do so, and was found to have completely rotted away in the soil. A week later overground shoots were also produced from the three healthy sets, and these grew into large, perfectly healthy specimens, which were of course somewhat etiolated or “‘drawn,” but which up to the end of the experiment never showed the slightest signs of Phytophthora or any other fungus on them. The plants from the two diseased sets also developed well, but in a slightly less robust fashion. One of them remained in every respect perfectly healthy and absolutely free from any form of disease whatever until the end of the experiment. The other one had but two stalks, one of which was very weakly from the start, but not owing to the presence of Phytophthora in it. After a short time one or two of the leaflets on this feeble stalk became blackened at their very tips. ‘These leaflets were kept under close observa- tion with the microscope, but only Botrytis developed on them, noé Phytoph- thora. By degrees this feeble shoot gradually succumbed from above downwards. It was kept under close and constant observation; and when nearly dead it was removed and subjected to further microscopic observation and incubation, but not the slightest trace of Phytophthora was found on it at any time. ‘The other stalk of this plant grew well, and remained entirely free from disease of any kind until the end of the experiment. Hence this part of the experiment resulted in the production of two plants absolutely free from Phytophthora from two diseased sets, placed under conditions extremely favourable to the development of this fungus. Of the eighteen sets (nine diseased and nine healthy) in the pots in the cool greenhouse, most of the diseased ones produced overground shoots earlier than the healthy ones; but out of the nine diseased sets, three produced no plants, and were found to have completely rotted in the soil. All the nine healthy sets produced healthy plants. The plants developing from the diseased sets were here, as in the warm house also, somewhat less robust than those from the healthy ones, and one in particular (No. 15) produced a shoot only 2 or 38 inches high which quickly became diseased from below upwards, and soon died. Doubtless the mycelium had entered the shoot from the parent set. ‘This plant was removed as soon as possible for fear of its causing the infection of the neighbouring ones by “spores.” Up to April 27th all the plants in the cool house, with the above exception, had PrrHYBRIDGE—Experiments with Phytophthora. 21 grown well and produced healthy foliage; but, on that date, suspicious- looking spots were seen on the leaflets of one of the plants grown from a healthy set. Microscopic examination showed that Phytophthora was present. The plant was removed immediately; but during the next few days Phytophthora gradually appeared in isolated spots on the leaves of seven of the plants from healthy, and four of the plants from the diseased, sets. ‘These affected plants were removed immediately they showed signs of the disease; and by May 9th two plants only were left, one derived from a healthy, and one from a diseased, set. In view of the stress which is so frequently laid on the necessity of a high temperature and considerable moisture for the occurrence of Phytophthora, it may be regarded perhaps as somewhat surprising that the fungus should have developed and spread in this manner in a cool greenhouse during the month of April. ‘The mean outside temperatures during the period in question were :—maximum d2°8° F., minimum 35°8° F.; and within the cool house they probably ranged from 57°F. to 38° F. Although absolute proof is lacking, it seems practically certain that the plants whose foliage became diseased must have become infected by means of “spores” from the single diseased sprout sent above ground by one of the diseased sets. There can be no question with these plants as to infection direct from the mycelium in the sets, for the attack began on plants derived from the healthy ones! It seemed hardly pos- sible that the two plants left could have escaped contamination by “ spores” like the rest and would remain free from disease for long; but yet during the period from May 9th to June 14th, extending therefore over more than five weeks, they were allowed to remain in the cool house, and no signs of Phytophthora made any appearance on either of them. On the latter date after a final, most thorough search for any incipient signs of the blight, which gave an absolutely negative result, these two plants—one derived from a healthy and the other from a diseased set—were placed in the warm greenhouse mentioned above. Hach of them was covered with a large bell-jar, and they remained under these conditions for a period of four weeks all but one day. During this time the bell-jars were occasion- ally removed for short intervals to permit of the thorough examination of the plants and to water the pots, which was but rarely necessary. So moist was the atmosphere within the bell-jars that intumescences were formed on the leaves of both plants; aud such conditions must have been ideal for the development of Phytophthora. Nevertheless no signs of it ever appeared on the plants. As they grew, parts of some of the leaflets, chiefly their tips in both cases, came into contact at one or two points with the tops and sides of the bell-jars, Where this occurred the tissues decayed into a slimy material p2 22 Scientific Proceedings, Royal Dublin Society. o~ in which bacteria were plentiful, but no Phytophthora was present; and all efforts to discover this fungus on either of these two plants during the period named met with absolutely negative results. This part of the experiment, therefore, confirms the previous part, the results being in both cases the production from diseased sets of plants entirely free from Photophthora under conditions extremely favourable to the fungus and withal adverse to the plant. The result is the exact opposite to that obtained by Massee, who obtained diseased plants from diseased sets in five cases out of six; but, as pointed out above, in the absence of controls, it is impossible to assume with any degree of certainty that these plants became affected directly through the tubers. On the other hand, the result.of my experiment is in agreement with those of many previous workers which are in the main to the effect that tubers affected with Phytophthora produce healthy plants; and the idea that the recurrence of the potato-disease year after year is due to the migration of dormant Phytophthora mycelium, in or into apparently healthy plants during unfavourable seasons of weather in the summer, can only be regarded as a theory with no evidence to support it. During the summer the question of the production of healthy or diseased plants from diseased tubers was further tested at the Temporary Station for the Investigation of Plant Diseases at Clifden, Co. Galway. A single ridge of reclaimed bog-soil, occupying an area of about one square perch, was planted with 132 uncut “champion” tubers, attacked by Phytophthora, on April 12th. Only fifty-three of these produced plants; the remaining seventy-nine rotted in the ground without doing so. The fifty-three plants were not quite so robust as neighbouring ones grown from healthy tubers; but they showed absolutely no signs of Phytophthora until July 15th. On this date the blight was found as isolated spots here and there on thie leaflets in the ordinary fashion, indicating an attack from spores borne from neighbouring plots, some of which were attacked with it three weeks earlier. It seems quite impossible to believe that these spots of blight, in many cases on isolated outstanding leaflets, could have arisen from internal mycelium, while the remaining portions of the plants, including the stalks, were quite healthy. How could Phytophthora, if present internally, have succeeded in carrying on an existence for over three months without exhibiting some signs of its presence? ven if it remained alive in the tubers all this time, which is to say the least most unlikely, how could it possibly have grown up through the stalks and out to the leaflets without leaving some impression of its strongly parasitic and destructive characters on the tissues through which it progressed ? Comparisons have been made between the. supposedly PeruyBRipee— Leperiments with Phytophthora. 23 dormant mycelium of Phytophthora, and that of some of the smut fungi; but such comparisons are entirely out of place until it has been definitely established that the former fungus does possess dormant mycelium, which is at present far from being the case. ‘he general habits and behaviour of the smuts are so far removed from those of Phytophthora and its allies that the existence of any such similarity as is assumed is most improbable. ‘Ihe dormant mycelium theory is in reality but a modification of one brought forward in the first instance by de Bary, but discarded by him some five-and- thirty years ago as not being in accordance with known facts. If this theory is correct, it seems almost impossible to explain the undeniably beneficial results accruing from spraying the crop with Bordeaux or Burgundy mixtures. Every grower of potatoes knows how essential it is to carry out this process of spraying before the blight has attacked the plants, for, if done later, the efficacy of the treatment is very seriously diminished. Spraying must be looked upon as a preventive method against the attacks of the blight from without and not from within. If the fungus once gains an entry into the tissues, external spraying does not prevent its spread in them. In some experiments which I carried out in 1909, I found that carefully painting over areas affected with bight by hand with Burgundy mixture, and even dipping affected foliage into the mixture, did not arrest the progress of disease, provided that the conditions of moisture and warmth were suitable. ‘The mycelium of the fungus was even seen to emerge and form “spores” through places on leaves thickly coated and blue with the mixture. Not only is this theory of dormant mycelium advocated to account for the infection of the over-ground parts of the potato-plant during the summer, but it is also employed to account for the attack of the new crop of tubers. It is stated that it has not been proved that the tubers become diseased as a result of the falling of the “ spores” from the foliage on to the soil, and the ultimate arrival of them, or the products of their germination, on the surfaces of the tubers. It is strange that such a statement should be made at this time of day, in view of the many experiments which have been carried out to settle this point, and which foree one to the conclusion that this in reality is at least the principal, if not the oniy, way in which the tubers do become infected. If the new tubers are infected directly from the old ones by invading mycelium, why is it that those tubers nearest the surface of the soil, and therefore generally farthest away from the diseased set, become first and worse diseased than the deeper-lying ones? Why is it that the diseased areas of the new tubers are nearly always, if not always, superficial, and 24 Scientific Proceedings, Royal Dublin Society. are decidedly not in the majority of cases, as should be the case, situated at the “heel”? end, where the rhizome enlarges to form the tuber? When the mycelium leaves the old set, and passes into the main stalk, and thence proceeds on its way to the new tuber (as if is supposed to do), why is it, as previously stated, that such stalk thus invaded at its base by a virulent parasite shows no signs of this in the drooping and other unusual behaviour of its foliage, as occurs in other similar cases such as Black Stalk Rot, &e.? The truth is that it is just as difficult to reconcile well-observed facts concern- ing the attack of the tubers with this theory as it is in the case of the stalks and foliage. In the plot-experiment described above, the crop was raised on August 22nd, about five weeks after Phytophthora was first observed on the foliage. During this time the blight had not spread to any very great extent over the plot owing to the fact that the plants were sprayed three times, and when dug, they possessed but little diseased, and still plenty of healthy, green foliage. As was to be expected from the nature of the plants and the poverty of the soil, the yield was not a large one. All the tubers, however, were very carefully examined, and not a single one showed any traces of being attacked by Phytophthora. Being raised before the foliage was badly blighted, so that a copious fall of “spores”? could not take place, it was to be expected that the tubers could scarcely have become infected from that source; but if they could become infected from the old sets direct, surely the period available for this to have oecurred can scarcely be described as having been too short? For, if the hypothetical dormant mycelium had in this time been able to awake and reach the leaflets, surely it could have traversed the much shorter distance to the new tubers, and yet they were found to be healthy in every case ! It is further maintained that by means of this dormant mycelium theory the outbreaks of severe and simultaneous epidemics are more satisfactorily accounted for than by supposing that the destruction is due primarily to the dispersion of “spores.” It is imagined that infection by this latter method would take place too slowly to permit of, say, the destruction of whole fields within a short period, as sometimes occurs. It is stated that “when a potato-plant infected with the spores of Phytophthora is placed under a bell-jar in a very damp atmosphere, subdued light, and high temperature—conditions most favourable to the development of the parasite—it is only after a period of four or five days that the fungus produces fruit on the leaves, and then only at the point of infection. On the other hand, the fact is too well known that a field of potatoes—or all the fields in a certain district—which at a given time appeared to be healthy Prernypripee—Leperiments with Phytophthora. 26 and vigorous have, under certain climatic conditions, been reduced to a blackened, decaying, footid condition within twenty-four hours. Considering the second part of this statement, the whole of its import depends on the interpretation of the words “appeared perfectly healthy.” If it is to be assumed that the words mean “were actually perfectly healthy,’ it is necessary to ask on what definite scientific evidence this statement rests, and the answer, I think, will be found to be—none! The first appearances of the blight are somewhat easily overlooked, even by trained observers, especially when a considerable area is under surveillance, for many of the attacked parts of the plant are more or less hidden by healthy foliage. Further, it is almost notorious how easily the early stages of attacks of plant-diseases in general are overlooked by farmers and others unless very special efforts are made to discover them. In all probability the words quoted are rather to be construed as meaning “seemed to be quite healthy to a casual observer,’ and, if this is so, epidemics are not by any means difficult to explain. It is quite easy to exaggerate the suddenness with which an epidemic comes on. What to afarmer might appear to be a sudden epidemic would be in many, if not all, cases to a trained observer nothing more than a rather quick culmination to a series of events which had been slowly proceeding beforehand more or less unobserved by others. ‘he appearance of an epidemic is not frequently, if ever, absolutely contempo- raneous with the advent of changed weather conditions; and my own observations lead me to believe that a serious spread of the disease occurs chiefly aiter a continuance of afew days of bad weather, rather than imme- diately on the setting in of it. Massee himself apparently requires a “spell” of bad weather for an epidemic to be set up. As mentioned previously in this paper, too much stress must not be laid on special weather-conditions as a necessity for, at any rate, the slow production of ‘‘spores,” and dissemination of the disease. It seems pretty certain, or at all events quite within the realms of possibility, that before an epidemic occurs, the blight is already present to some extent, more tlan one might be willing to admit, and that many of the leaves are spotted and bear “spore ’-producing tufts of mycelium, while many others have ‘ spores,” which have fallen on them, in more or less advanced degrees of germination and infection. ‘The advent of a spell of warm, moist weather has then, as a natural consequence, but not necessarily absolutely immediately, an alarming development of the disease. It may be that four or five days are required for infection resulting in fresh ‘“ spore”-production, to take place in artificial experiments; but it by no means follows that such a long period must elapse before the serious destruction of the tissues can occur in nature, provided that 26 Scientific Proceedings, Royal Dublin Society. the external conditions are particularly favourable to the fungus, and that “spores” of various ages and in different stages of germination, and possibly of infection, are already fairly well distributed over the foliage. There there- fore appears to be no really substantial reason for invoking the aid of this dormant mycelium theory in order to satisfactorily explain epidemics. With regard to the spread of epidemics, Massee states :—‘‘ Again in the case of every fungus epidemic proved to be due to the diffusion of spores, the disease always originates from one or more primary centres of infection, and gradually extends, whereas in the case of the potato-disease the appearance of the epidemic is often simultaneous over a considerable area.” It is true that in a given area the first appearances of blight are often observed at or about the same time in different places in that area, although where there are special cases of situation and exposure, exceptions to the general rule may occur. Now anyone who has carefully studied the question in the fields, or watched the development of the blight, knows that the disease does actually spread in them from such original centre or centres of infection exactly in the manner described ; and during the past two summers I have had abundant opportunity of observing this in the clearest possible fashion. Let a period of warm, moist weather set in after a good, though to the ordinary person easily overlooked, start of the disease from such centres, and the occurrence of an epidemic needs no further explanation. Further, it must not be assumed that epidemics are indeed invariably simultaneous even over compara- tively small areas, for I have observed in a field of potatoes of one variety, and all treated in the same way and not sprayed, one half suffering from an epidemic, while the other half has remained comparatively free from the disease. Perhaps the most serious obstacle against accepting this dormant mycelium theory lies in the fact that, if it is to be used to explain epidemics in the manner suggested, it is almost impossible to get away from the suggestion that practically every potato which is planted is diseased with Phytophthora to start with. But the fact that a certain continental writer averred, a year or two ago, that there was no such thing as a healthy potato tuber in Kurope, need not lead us as well to entertain such a ridiculous notion. In any case the said writer was probably not referring to Phytophthora, in particular, but rather to the disease known as Leaf Roll. Enough has been said to show that this theory is based on no really scientific evidence, that it is extremely hard to reconcile with many of the well-known facts concerning the potato-disease, and that others of them can be satisfactorily explained without reference to it. Were its promulgation confined to scientific periodicals where its pros and cons could be adequately PrruyBripGE—Lzperiments with Phytophthora. QT discussed, little harm would be done. But where matter of this kind is incorporated as established beyond doubt into text-books written for the information of students and others, the case becomes more serious, owing to the danger of non-critical readers being misled. There is no evidence at present existing to show that the attack of the potato-crop as a whole with blight occurs otherwise than by aerially borne “spores,” if we except the few diseased plants from diseased tubers which do undoubtedly occasionally occur, but which can scarcely be regarded as being part of the general crop. Whether the sources of these “ spores” at present known are sufficient to account for the annual recurrence of the blight, and particularly for the time of its appearance each year, are questions which must be left for future work to decide. BipiioGraPny. 1. Prinesuuim, N.—Ueber die Kartoffelkrankheit. Vierter Bericht d. Centralkommission f. d. agrikultur-chem. Versuchswesen. JLand- wirthschaftl. Jahrb., Bd. 5, 1876. 2. Smrra, Worrnineron, G.—Diseases of Field and Garden Crops, London, 1884, pp. 295 e¢ seg. 3. [Boarp or AGRicuLTURE].—Report on recent experiments in checking Potato Disease in the United Kingdom and abroad. London, 1892, p. 56. 4, Massrn, G.—A Text Book of Fungi.—London, 1906, p. 210. Perpetuation of “‘ Potato Disease’ and Potato ‘ Leaf Curl” by means of hybernating mycelium. Kew Bulletin, No. 4, 1906, p- 116. Reprinted in Journ. Bd. Agric., vol. x11., 1906, p. 233. 6. Anonymous.—The spread of fungus diseases by means of hybernating mycelium. Journ. Bd. Agric., vol. xu, 1906, p. 257. 7. Masseu, G.—Diseases of cultivated plants and trees. London, 1910, p. 126. SCIENT. PROC. R.D.S., VOL. XIII., NO. II. E SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1. A Seed-Bearing Ivish Pteridosperm (Lyginodendron Oldhamium, Williamson).. By T. Jounson, D.sc., F..8. (Plates I., II., IIT.) (In the Press.) 2. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Gzorcr H. Perayeriney, D.SC., PH.D. (March, 1911.) 1s. DUBLIN: PRINTED Al THE UNIVERSITY PRESS BY PONSONBY AND GIBES. due ire aL eas Pe aye Re THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 3. APRIL, 1911. MECHANICAL STRESS AND MAGNETISATION OF NICKEL (PART I1.), AND THE SUBSIDENCE OF TORSIONAL OSCILLATIONS IN NICKEL AND IRON WIRES WHEN SUBJECTED TO THE INFLUENCE OF LONGITUDINAL MAGNETIC FIELDS. BY WILLIAM BROWN, B.&c., PROFESSOR OF APPLIED PHYSIOS IN THE ROYAL COLLEGE OF SCIENCE FOR IRELAND. [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. 1 RTRs WILLIAMS AND NORGATH, FJ geooemsn Stig ~~ 14, HENRIETTA STREET, COVENT GARDEN, LONDON, oh UG 1911. Nan N ODnal ft Price One Shilling. Koval Bublin Society. NN FOUNDED, A.D. 1731. INCORPORATED, 1749 EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be get down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Hditor. PuraysripeE— Lxperiments with Phytophthora. 27 discussed, little harm would be done. But where matter of this kind is incorporated as established beyond doubt into text-books written for the information of students and others, the case becomes more serious, owing to the danger of non-critical readers being misled. There is no evidence at pressnt existing to show that the attack of the potato-erop as a whole with blight occurs otherwise than by aerially borne “spores,” if we except the few diseased plants from diseased tubers which do undoubtedly occasionally occur, but which can scarcely be regarded as being part of the general crop. Whether the sources of these “ spores” at present known are sufficient to account for the annual recurrence of the blight, and particularly for the ¢ime of its appearance each year, are questions which must be left for future work to decide. BipLioGRaPHy. 1. Prinesouim, N.—Ueber die Kartoffelkrankheit. Vierter Bericht d. Centralkommission f. @. agrikultur-chem. Versuchswesen. Land- witthschaftl. Jahrb., Bd. 5, 1876. 2. SmirH, Worrnineton, G.—Diseases of Field and Garden Crops, London, 1884, pp. 295 et seg. . [Boarp or AcricuLrurE].—Report on recent experiments in checking Potato Disease in the United Kingdom and abroad. London, 1892, p. 56. 4. Massrr, G.—A ‘l'ext Book of Fungi.—London, 1906, p. 210. Perpetuation of ‘‘ Potato Disease ’’ and Potato ‘ Leaf Curl” by means of hybernating mycelium. Kew Bulletin, No. 4, 1906, p- 116. Reprinted in Journ. Bd. Agtic., vol. xim., 1906, p. 233. 6. Anonymous.—The spread of fungus diseases by means of hybernating mycelium. Journ. Bd. Agric., vol. xtr., 1906, p. 257. Oo 7. Masser, G.—Diseases of cultivated plants and trees. London, 1910, p. 120. SCIEN. PROC. R.D.S., VOL. XIII., NO. IL. ath [in 228 Dae MECHANICAL STRESS AND MAGNETISATION OF NICKEL (PART II.), AND THE SUBSIDENCE OF TORSIONAL OSCILLATIONS IN NICKEL AND IRON WIRES WHEN SUBJECTED TO THE INFLUENCE OF LONGITUDINAL MAGNETIC FIELDS. By WILLIAM BROWN, B.Sc., Professor of Applied Physics, Royal College of Science for Ireland. {Read January 24. Ordered for Publication Frsrvary 14. Published Aprin 15, 1911.] Ir was shown in Part I. of this paper’ that when a nickel wire was subjected to simultaneous longitudinal and circular magnetism, the maximum twist of the free end of the wire was greater the greater the longitudinal load ; this result was obtained by observing the effects of three different longitudinal loads on the end of the wire under test, the largest load being at the rate of 3 x 10° grammes per square centimetre. The first division of the present communication gives results obtained when the same and higher loads were employed, as well as higher longitudinal magnetic fields ; and for this work a new batch of pure nickel wires was got from the manufacturer. One of these wires was prepared in the manner explained in Part I. of this’paper,? the degree of magnetic softness obtained being between H; and Hz: of the arbitrary scale there used, that is, the wire had a simple rigidity of about 720 x 10° grammes per square centimetre, and was a full size No. 16, of diameter 0°168 cm. and of cross-sectional area 22°17 x 10° square centimetres. This wire, with a given longitudinal load on its lower end was suspended vertically in the middle of a long solenoid, by means of which longitudinal magnetic fields of definite values could be applied to it. The apparatus being arranged as already indicated,” an electric current was sent through 1 Scient. Proc. Roy. Dub. Soc., yol. xii., No. 37, pp. 500-518. 2 Loe. cit. Brown— Mechanical Stress and Magnetisation of Nickel. 29 the wire, the maximum value of which was 100 amperes per square centimetre ; and the twist of the lower free end of the wire was read off by means of the usual mirror, lamp, and scale arrangement. The scale was divided into millimetres ; and its distance from the mirror on the vibrator! at the lower end of the wire was 116°5 ems. With a certain longitudinal load on the wire, the twists of its free end were observed when twenty-siw different values of longitudinal magnetic fields were successively applied ; the load on the wire was then increased, and the twists were again observed for the same magnetic fields ; and so on for six loads in all, the highest load being about 13:5 kilos, or at the rate of 6 x 10° grammes per square centimetre. The results obtained with the six different longitudinal loads, and when the wire was placed in longitudinal magnetic fields up to a maximum of 200 ¢.g.s units, are given in Table I., and are shown as curves up to a magnetia field of 100 units in fig. 1, p. 31. From the curves it will be seen that the maximum twist attains its highest yalue when the longitudinal load on the wire is at the rate of 4 x 10° grammes per square centimetre, and for the two higher loads the maximum twist is about the same, or slightly diminished. The arrangement of the apparatus would not allow with safety the application of still higher loads. If we plot on the axis of abscissa the values of the longitudinal load on the wire, and as ordinates the corresponding values of the longitudinal magnetic field in which the maximum twist occurs, the points will be found to lie very approximately ina straight line, showing that, between these limits of the load, the magnetic field in which the maximum twist takes place is proportional to the load at the end of the wire. From Table I., by plotting as abscissee the value of the longitudinal load on the wire, and as ordinates the corresponding values of the twist for any longitudinal magnetic field between 70 and 200 ¢.g.s. units, the points in every case will be found to lie very approximately in a straight line, showing that when the twists have attained their highest values, between the limits of these loads, the curves are practically parallel for high magnetic fields. It will be noticed in fig. 1 that, as the load on the wire is increased, the peak or turning-point of the curve becomes less sharply defined; and in order to bring out more clearly the effect of an increased load on the magnetisation of the wire, a series of cyclic curves were taken when the wire was surrounded by the magnetic field corresponding to the maximum twist for a given load 1 The vibrator which constituted the load on the wire in all cases was composed of brass and lead, so as to ayoid errors due to its becoming magnetised, E2 30 Scientific Proceedings, Royal Dublin Society. thus :—The maximum electric current (100 amperes per square centimetre) was sent through the wire, and the twist or steady deflection read off on the es Si Twist or deflection on the scale in millimetres when the longitudinal | 3 pee load on the wire x 10° grammes per square centimetre was :— 2 Sore = STIS a Be iSite OH | hh 8 4 5 6 | 0°45 | 23°5 15°65 9) 6 4°5 3 1 29 20°5 11°5 8 6 45 2 37 28 16 12 ) d 3 43 33 20°5 15°5 1175 9 5 52°65 42°5 28°5 22 16°8 13°8 7 59 50°5 36°5 28°5 21:5 18 10 64 60°5 47 36'5 29 24 13 66 67 56 44 35°5 29-5 16 65 12 63° 51 41-5 30 20 63 75 71 59 49°5 42 25 60 73°5 77 67°5 58 50 30 57:5 70°8 80°5 75 657A 57:5 35 55°2 67:8 81 81 72°5 64 40 58 65-2 79 8h 79 i | 45 50'S 62°8 75) 86°5 83:5 76 | 50 48°8 60-2 72 85 86 81 60 46 55°5 66 77°) 85 86 70 41-2 51-2 60°5 70 i) 85 80 38 47 55°2 63 76 77 90 35 43-2 50°5 57 63 70 100 82°5 40 46°5 52 57°) 64 120 27'8 b4 39°2 43°56 48 53 140 24 29 33:5 37 40 | 44 160 21°5 25 29 31°) 34-2 BY) 180 19:5 22:2 25°5 28 30 | 32°2 200 18 20°2 23 25 27 29 | millimetre scale; the current was then diminished by steps, and the deflection on the scale observed for each step, down to zero current, when the remanent Twist or deflection on the scale (mm.). Brown—Mechanical Stress and Magnetisution of Nickel. 31 twist was read off with the circuit open; the circuit was then closed, and the current reversed, and 8 or 10 steps again taken up to maximum current, cycle was obtained. _ the twist or deflection being read off at each step, and so on until a complete These values were then plotted on millimetre paper, with the values of the current through the wire as abscissee and the corresponding values of the twist or deflections on the scale as ordinates, the curve was drawn and its area determined. The curve or loop so obtained was very symmetrical about both the horizontal and vertical axes, but was longer and narrower than the curve obtained in a similar manuer with an iron wire.? f 80 Pa a yo Poe | 20 40 60 Fie. 1.—Longitudinal Magnetic Field. 80 Cycles were taken in this way for seven loads in all; and in each case the longitudinal magnetic field round the wire was that which gave the maximum twist with the given load; for example, when the load on the wire was 1-5 x 10° grammes per square centimetre, the magnetic field round it was 20 c.g.s. units; and when the load was 4 x 10° grammes per square centimetre, the magnetic field round the wire was 44 units; and so on. 1 Scient. Proc. Roy. Dub. Soc., yol. xii., No. 17, p. 180. 100 32 Scientific Proceedings, Royal Dublin Society. The smallest load, 0:016 x 10° grammes per square centimetre, was obtained by means of an aluminium tube with a mirror attached, and the magnetic field in which the maximum twist occurred with this load was found to be 10:3 units.’ In all the seven cases the cyclic curves were plotted to the scale in which two centimetres represented one ampere on the axis of abscissee, and on the axis of ordinates one centimetre represented ten divisions (mm.) of deflection on the scale; the total area of each curve was then measured in square centimetres. The results are given in Table IT. TABLE II. Load on the wire Longitudinal | ‘Total area of in grammes per magnetic field | cyclic curve sq. cm. x 10°. round the wire. in sq. cms. | 0:016 | 10°3 14°5 0°5 13 16°0 1°5 20 18°5 3 30 22°6 4 44, 25°5 5 54 24-0 6 64 22°6 From Table IJ. if we plot the values in the first column on the axis of abscissee, and on the axis of ordinates the corresponding values in the third column, it will be found that the first five points lie in a straight line with a rapidly rising slope, and the last ¢hree points lie also in a straight line which has a slowly falling slope. hat is, the effect of increasing the load on the wire is seen to reach a maximum with the load of 4 x 10° grammes per square centimetre, as is also less clearly shown in fig. 1, p. 31. Tne SuBstpENcE oF ‘l'orsIoNAL Visrations In Nickrn AND [ron WIRES WHEN SUBJECLED TO THE ACTION OF LONGITUDINAL MaaGnevic FIEnps. Section 1.—Nickel Wire. It seems evident that the internal viscosity of a nickel wire is the important factor in determining the maximum twist of the free end of a 1 Scient. Proc, Roy. Dub, Soc., yol. xii., No. 37, p. 507, Brown—WMechanical Stress and Magnetisation of Nickel. 38 wire when it is subjected to the combined action of circular and longitudinal magnetisation. From the fact that the magnetic field in which the maximum twist takes place increases as the load on the wire increases—that is, as the load increases the peak of the curve is displaced towards the right as shown in fig. 1—one would suppose that a wire placed under these conditions of load and magnetic field would offer more resistance to any change in its internal configuration than when placed in any other field of different strength. In order to test this, a series of experiments were made on the rate of subsidence of torsional vibrations in the nickel wire when it was surrounded by longitudinal magnetic fields of different strengths. The results of some experiments of this kind on nickel and other wires have been published by Gray and Wood,' in which nickel wires one metre long were employed, the initial amplitude of oscillation being 90°. These authors point out that this latter condition (the magnitude of the amplitude of oscillation) plays a very important part in the final results, which is confirmed in a way by the results obtained by the present writer, who used an initial amplitude of about 7° only in the results given in this and the following section. The above-named authors, however, omit to state the value of the longitudinal load that was on their wires when under test. In the experiments described below the length of the nickel wire used was 226 cms., of diameter 0°168 cm. and simple rigidity 708 x 10° grammes per square centimetre; and by means of the long solenoid already mentioned the wire was in a uniform magnetic field throughout its whole length. The amplitudes of the torsional oscillations of the wire were read off by means of the light spot on the millimetre scale, which was placed at a distance of 116°5 ems. from the mirror on the lower end of the wire; and the largest amplitude used was about 7° or 300 millimetres on each side of the zero on the scale. This initial amplitude was chosen because the maximum twists obtained in the experiments on Magnetism and Torsion fell between this value and the smallest amplitude taken in the experiments now under discussion. The method of experiment was as follows :— With a given load on the end of the wire and a certain longitudinal magnetic field round it, it was made to oscillate round its own axis; and when the initial amplitude of osvillation was correct—that is, when the ight spot was on the division marked 300 on the scale—the observer began to count the oscillations and read off the amplitude at every fifth oscillation up to the twentieth, and then every tenth oscillation, until 70 oscillations in all had taken place. The load on the wire being kept 1 Proc. Roy. Soc., vol. lxx., 1902, and vol. lxxili., 1904. 34 Scientific Proceedings, Royal Dublin Society. the same, the magnetic field round it was changed, and a series of observations taken the same as the first, and so on for sixteen different magnetic fields up to 200 ¢.g.s. units. At the beginning and end of each series of observations, with a given longitudinal load on the wire, the rate of subsidence of the oscillations was observed when there was no magnetic field round the wire, the state of no field being obtained by sending an electric current round the solenoid of such a value and in such a direction as to annul the vertical component of the Harth’s magnetism. The method of obtaining the torsional oscillation without imposing any pendulous motion on the wire was as follows:-—The wire with a certain magnetic field round it and a given load on its lower end was put in circuit with a storage cell, rheostat, reversing key and plug-key, the cireuit being completed through the wire under test by means of a short piece of iron wire fixed on the under side of the vibrator or load and dipping into a cup of mercury. When everything was quite steady, a small electric current was sent through the wire and reversed in wnison with the torsional oscillations of the vibrator until a sufficient amplitude had been attained ; the mercury cup was then taken away, thus leaving the wire free and performing only torsional vibrations. An extensive series of observations on torsional subsidence were made under fowr different values of the longitudinal load ; and the results of a few are shown as curves in fig. 2. The results here shown were obtained when the load on the wire was at the rate of 15 x 10° grammes per square centimetre ; the numbers at the right- hand end of each curve indicate the strength of the longitudinal magnetic field which was round the wire when it was being tested. Loads on the wire higher than 4 10° grammes per sq. cm. were tried; but the damping of the oscillations was so rapid at the beginning of the observations, and the amplitude became so small at the end of 70 vibrations, that considerable error was introduced, and the observations were therefore not recorded. The curves in fig. 2 show that the application of an external magnetic field increases the internal viscosity of the wire up to a field of about 20 ¢.g.s. units; then the viscosity begins to decrease when higher fields are applied. With a maguetic field of 80 units round the wire the amplitude, after 70 vibrations have taken place, is nearly the same as when there was no field round the wire; but the rates of subsidence in the two cases are different, as is shown by the slopes of the two curves. The rates of subsidence were taken tor six different maguetic fields Brown—WMechanical Stress and Magnetisation of Nickel. 35 between 80 and 200; but only two are given here (not to crowd the figure) which show a remarkable diminution in the internal viscosity of the wire, due to the high fields. The curve given for the magnetic field of 200 units may be a little high, due to the solenoid and wire becoming slightly heated during the experiment, when an electric current of nearly 5 amperes was on for about four minutes. ] 300 | KI 200 200 100 Amplitude of oscillations in scale-divisions (mm.). O 10 20 50 40 50 60 70 Fic. 2.—Number of Vibrations. The damping imposed on the torsional vibrations of the wire by a magnetic field is better brought out by considering the amplitude attained after a certain definite number of oscillations have been made. In Table III. are given the results obtained when four different longitudinal loads were on the wire and when it was subjected to the action of ten different longitudinal magnetic fields for each of the four loads. The numbers in the Table are the amplitudes of the oscillations attained after 70 vibrations had been accomplished—in every case starting from an SCIENT. PROC., R.D.S., VOL. XIII., NO. II. F 36 Scientific Proceedings, Royal Dublin Soctety. initial amplitude of 300 divisions on the scale, or from an angular twist on the lower end of the wire of 74°. These results are also shown as curves in fig. 38, in which the abscisse are the values of the longitudinal magnetic field that was round the wire when being tested, and the ordinates the corresponding values of the amplitudes after 70 vibrations had been accomplished. Tasre III. | Amplitude of vibrations in scale-divisions (mm.) after 70 vibrations have | Longitudinal | been accomplished, the initial amplitude being 300 on the scale. | magnetic =| The loads on the wire in grammes per sq. cm. x 10° were :— 05 15 3:0 4:0 0 | 72 110 136 | 165 5 ar 74 110 138 10 39 50 84 | 113 | 15 37 34 62 90 | 20 39 28 45 | 70 30 46 30 26 40 40 56 37 26 22 50 71 46 30 22 60 91 62 40 25 70 116 84 54 30 80 146 113 70 | 35 The numbers at the right-hand end of each curve give the longitudinal loads in grammes per square centimetre that were on the wire when it was being tested. ‘The curves show that the greatest damping of the torsional oscillations takes place in each case when the wire is surrounded by a longitudinal magnetic field of the same value as was round the wire when the maximum twist for the given load was obtained, as is exhibited in fig. 1— that is, the crests of the curves in fig. 1 take place in the same longitudinal magnetic fields as the ho/dows of the curves in fig. 8, or the magnetic field in which the maximum effect takes place is larger the larger the longitudinal load on the wire. Gray and Wood' have also shown that the effect of increasing the weight of the vibrator on the end of the wire is to give a greater maximum effect and 1 Loe. cit. Brown—WMechanical Stress and Magnetisution of Nickel. 37 to shift the maximum to a greater field. As already remarked, these experimenters used a large initial amplitude of oscillation; and though the actual values of the weights are not mentioned, the maximum effect for the light weight took place in a magnetio field of about 93 units, and for the heavy weight in a field of about 132 units. The fact, also, that in their experi- ments, the wire under test projected at the ends of the solenoid from 1 to 4 centimetres, leaving perhaps not more than two-thirds of the length of the wire in a uniform magnetic field, may have had some effect on the final results as well as the large amplitudes employed. 150 0-5x 10° 10 3 1-5 x105 Aye eae : 100 vations in scale-divisions (mm.) after 70 vibrations from an initial amplitude of 300 divisions or 7 }4-0x10° Amplitude of vib 0 10 20 350 49 50 60 70 50 Fic. 3.—Longitudinal Magnetic Field. In order to test the effect of a magnetic field on the internal viscosity of a harder nickel wire, experiments similar to the above were made with a wire of simple rigidity 756 x 10° grammes per square centimetre. This wire was also 226 cms. long and 07168 cms. in diameter, and was hardened by hanging it in a vertical position with a weight on its lower end equivalent to 15 x 10° grammes per square centimetre; and then raising it toa bright cherry-red heat by means of a broad Bunsen burner, and so the wire Neue E 38 Scientific Proceedings, Royal Dublin Society. hard by being allowed to cool under the tension due to the load. The wire was then placed in the solenoid, with a given longitudinal load on its lower end, and the rate of subsidence of the torsional oscillations observed when it was placed successively in longitudinal magnetic fields up to a maximum of 80 ¢.g.s. units. Three different longitudinal loads were used in this set of experiments, and, when the observations were plotted in curves, results similar to those given in fig. 2 were obtained—when the same load was on the wire—but with somewhat sharper slopes, as would be expected from a harder wire. Curves were also obtained similar to those given in fig. 38, but with slightly lower values throughout, and with the minimum points occurring in the same magnetic fields as those obtained with the softer wire. This latter circumstance also was to be expected, as it has been shown that when a nickel wire is subjected to the simultaneous actions of circular and longitudinal magnetism, the longitudinal magnetic field in which the maximum twist of its free end takes place is independent of the hardness of the wire.! Section 2.—Ivron Wire. It is known (1)’ that, when an iron wire is tested for magnetisation and torsion, the longitudinal magnetic field in which the maximum twist occurs is independent of the longitudinal load on the end of the wire between certain limits; (2)° that the magnetic field in which the maximum twist takes place is greater the larger the diameter of the wire. Experiments on the subsidence of torsional oscillations were therefore carried out with iron wires similar to those already done with the nickel wires. This was in order to find out if, like the nickel, the iron wires attained their greatest internal friction when they were placed in that longitudinal magnetic field which gave the largest twist when they were tested for magnetism and torsion. For this purpose two wires were tested— namely, one No. 16 8.W.G. when it was subjected to two different longi- tudinal loads, and one No. 14 8.W. G. when subjected to one load. Both wires were used in the physical state in which they were received from the manufacturer, the simple rigidity of each being about 815 x 10° grammes per square centimetre, 226 cms. long, the cross-sectional areas being 20:2 x 10% sq. cm., and 32°66 x 10° sq. em. respectively. The 1 Scient. Proc. Roy. Dub. Soc., vol, xii, No. 37, p. 505. * Scient. Proc. Roy. Dub. Soc., vol. xii, No. 36, p. 484. 5 Loe. cit., p. 495. Brown—WMechanical Stress and Magnetisation of Nickel. 39 No. 16 wire was placed vertically inside the long solenoid with a longitudinal load on its lower end equivalent to 10° grammes per square centimetre; and it was made to oscillate round its own axis, the amplitude of the oscillation being read off at every fifth or tenth vibration until 70 complete vibrations had been accomplished. This was done first when there were no maguetic fields round the wire, and then when there were magnetic fields round it of different strengths up to a maximum of 20 c.g.s. units. The load on the wire was then changed to 2 x 10° grammes per square centimetre, and another similar series of observations taken; the No. 14 wire was then put in place of the No. 16, and another set of observations taken when the load on it was at the rate of 2 x 10° grammes per sq. cm. The results obtained in the three cases were then plotted in curves, to the same scale as those given in fig. 2, with the numbers of vibrations as abscisse and as ordinates the corresponding values of the amplitudes of the oscil- lations; the curves so obtained were flatter than those got with the nickel wire, the rates of damping of the oscillations were less rapid, and the range more limited than in the case of nickel. The following Table gives the values of the amplitudes of oscil- lation with nickel and iron wires, when tested under the same conditions of magnetic field ; both wires were of No. 16 gauge; the load on the nickel Tasrim LV. Amplitude of oscillations in scale- divisions. Number iT of Nickel Wire Tron Wire Vibrations. H=0 H = 20 H=0 H = 20 oe ee Ee mata i = 0 300 300 300 300 | 5 269 | 209 285 | 287 10 243 | 160 270 274 15 221 116 | 257 | 262 | 20 203 103 | 245 251 30 174 73 | 292 230 40 151 | 5A 203 211 | 50 135 | 41 185 193 60 | 121 32 169 178 | 70 110 28 155 | 164 | | ss 40 Scientific Proceedings, Royal Dublin Society. was 1°5 x 10° grammes per sq. cm., and that on the iron 10° grammes per sq.cm. These values were obtained when the wires were placed successively in zero field and in a magnetic field of H = 20 c.g.s. units, in each case starting from an initial amplitude of 300 divisions on the scale or from an angle of 74". When the results obtained with the iron wires, with magnetic fields lying between these limits of 0 and 20 units, were plotted in curves, they showed that the internal friction of the wire was first increased and then decreased, as in the case of the nickel wires, but to a more limited extent. Gray and Wood, in the papers already referred to, state that no change of this nature in the internal friction of iron took place in their experiments ; they did not, however, employ any magnetic field round their wire between 0 and 22 units, whereas the present experiments show that the phenomenon occurs in low fields, that is, in a magnetic field of about 2°5 units with a No. 16 size wire, and about 3°5 units with a No. 14 wire. H. Tomlinson? has also observed that the internal ecawiar’ in an iron wire is perceptibly greater when it is surrounded by a magnetic field than when it is not; he does not indicate, however, that any definite magnetic field was found to give a maximum effect. The points where the greatest internal friction in iron wires occurs in the present experiments, though much less pronounced than in the nickel wires, are shown in the accompanying fig. 4, where as abscisse are plotted the values of the longitudinal magnetic field round the wire, and as ordinates the corresponding values of the amplitudes of oscillation when seventy vibrations had been made, starting in every case from an initial amplitude of 300 divisions on the scale (mm.) or from an angular twist on the lower end of the wire of 74. The two lower curves are those obtained with the No. 16 iron wire; the number at the end of each curve indicates the longitudinal load in grammes per square centimetre that was on tle wire when being tested. In each of these two curves the lowest point is reached when the wire is in a longitudinal magnetic field of about 2°5 units, which is the field in which the maximum twist occurred in the tests for magnetism and torsion already mentioned. The top curve in fig. 4 is that obtained with the No. 14 iron wire when loaded at the rate of 2 x 10° grammes per sq. em. ; and its lowest point occurs in a magnetic field of about 3°5 c.g.s. units, which is also the magnetic field in which the greatest twist took place in the magnetism and torsion tests. seca 1 Loe, cit. 2 phil. Trans. 1888, vol. clxxix., A, p. 18, 240 Amplitude of vibrations in scale-divisions (mm.) after 70 vibrations from an initial amplitude of 300 divisions or 74°. 180 Brown—WMechanical Stress and Magnetisation of Nickel. 41 It seems evident, therefore, in both nickel and iron wires, that the con- figuration of the molecules of the materials is such that the internal molecular friction is the greatest when that longitudinal magnetic field is round the wire which gives the maximum twist for the given load. 0 5 10. as) Fic. 4.— Longitudinal Magnetic Field. With iron wires this magnetic field is independent of the magnitude of the load on the wire, but increases as the diameter of the wire is increased, and for the sizes of wires under discussion it is also the magnetic field in which the maximum transient current was obtained when the wire was mechanically twisted.! With nickel wire this field increases as the load on the wire is increased, but is independent of the diameter of the wire.’ Section 3.— Influence of Amplitude of Oscillation. Experiments were now made in order to find out what influence the magnitude of the initial amplitude of oscillation has on the rates of subsidence of a wire magnetised longitudinally. 1 Scient. Proc. Roy. Dub. Soc., vol. xii., No. 17, p. 181. 2 Ibid., vol. xii., No. 37, p. 513. 20 42 Scientific Proceedings, Royal Dublin Society. For this purpose a nickel wire 226 cms. long, 0:123 cm. diameter, and of simple rigidity about 708 x 10° grammes per square centimetre was prepared for experiment in the manner already stated. The wire was suspended vertically in the centre of the long solenoid, with a load on its lower end equivalent to 3 x 10° grammes per square centimetre ; on the rim of the brass vibrator there was fixed a finely divided paper scale, by means of which, with the aid of a reading-telescope with a fine vertical hair in the eye-piece, the amplitude of oscillation could easily be read off to one-fifth of a scale-division. The scale was divided so that 90° was equivalent to 127 scale-divisions ; and since 0-2 of a division could be read with ease, the amplitude recorded may be taken as correct to within 8°5 minutes of arc; and since the time of a complete vibration with no magnetic field round the wire was 5.23 secs., the period was slow enough for the observer to note the turning-point with accuracy. Several sets of observations were made on the subsidence of torsional oscillations, starting from initial amplitudes of 90°, 70°, 50°, and 30° respectively, when the wire in each case was subjected to different longitudinal magnetic fields. Taste V. | | 3 8 Amplitude of oscillations in scale-divisions, from an initial amplitude of 127 | % § _ seale-divisions or 90°, when subjected to longitudinal magnetic fields of :— | Es) | AS 0 5 ) 1B) ev 30 40 | 50 60 | | | I i ae = = | | | 0 127 | 127 127 127 127 12 127 Uy | 5 117 | 108 | ney | 106 109°5 114°5 | 119 120 | | | | 10 108 89 85 84°5 92 100°7 110 113 | 15 99 72 63 62 72 86) 1 39938 105°5 20 91 59 43°5 | 39 D1 10°2 SE Os) | | | 30. 76 | 41-5 21:5 14 14°8 35°9 66 82°5 | 40 C6 | “gn | ia 8 64] 109 |} 40 | 66 nex 53:5 | 242 | 10:5 | 6-2 4 5-1 iy | 4 ! 60 | 45 19°8 8°6 3) 33 31 GZ | OS } iene70 38 | 16:5 72 4 {3 se 16:2 | | 80 32 14 6-2 |ueeS eae ees 2 | 90 27°5 1201 a7 4:9 100 23:8 10'S 5 | | 31 J \ | Amplitude of oscillations from an initial amplitude of 127 divisions (90°). 140 100} 80 60 40 20 Brown—WMechanical Stress and Magnetisation of Nickel. 43 The values obtained in one set of observations, from an initial amplitude of 90°, and for magnetic fields up to 60 c.g.s. units, are given in Table V., and six of them are shown as curves in fig. 5. 1 2 So 26 sO Gon mane BONO Fic. 5.—Number of Vibrations. In fig. 5, the number of vibrations attained from the initial amplitude of 127 divisions on the scale or 90° are plotted as abscissee, and as ordinates the corresponding values of the amplitude; the number at the right-hand end of each curve indicates the value of the longitudinal magnetic field that was round the wire when it was being tested. ‘I'hese curves show that the internal friction in the nickel wire is increased and then decreased by the presence of a magnetic field, but in a rather curious manner when high initial amplitudes are used. With no magnetic field, and with a field of five units round the wire, the slope of each curve is quite smooth and regular; but when a magnetic field of twelve units is round it, there is a slight flexure in the curve about the fifth vibration from the start ; the magnitude of this flexure is increased with a field of thirty units, and still further increased with a field of fifty units, and then diminished with a field of sixty units; the position of the flexure being shilted SCIENT. PROC. R.D.S., VOL. XIII., NO. Ils. ——___|5 JS eee 12 +30, 50 So 44 Scientific Proceedings, Royal Dublin Society. towards the right as the magnetic field round the wire is increased. ‘Ihis is not likely to be due to any errors in the observations, as the observations were taken repeatedly with the same results; this flexure in the curves did not occur when the initial amplitude of oscillation was about 7°, as is shown in the curves of fig. 2. The curves obtained in the same way when the initial amplitudes were 70°, 50°, and 30° respectively, all showed the same kind of flexure, but to a diminished extent, so that when the initial amplitude is small (74°), the flexure in the curves seems to be smoothed out. The influence of the magnitude of the initial amplitude on the rate of subsidence is perhaps better shown by reckoning the final amplitude attained after a certain definite number of oscillations have been made, starting in each ease from a different initial amplitude. ‘he results of some observations of this kind are given in Table VI., and are shown as curves in fig. 6. Taste VI. Amplitude of oscillations after 30 vibrations have taken place, starting from the initial amplitudes of :— Longitudinal | = vA - Le ae Magnetic | | Field. | 127 Divs. 99 Divs. | 70°65 Divs. | 42°5 Divs i | 90° 70° 50° | 30° eel i | | = | 0 76 59 41°5 26:2 | 5 41°5 33°) 27 20 | 12 21°5 15°5 12°5 10°5 20 14 9 7:5 6°2 | 30 15°5 78 5 4 | 40 36 | 10:5 5 3°8 i} 50 66 26 75 4-2 60 82°5 48-5 19°5 7 The number at the right-hand end of each curve in fig. 6 indicates the initial amplitude from which the oscillations were reckoned. By comparing the curves in fig. 6 with thosein fig. 3, which were obtained with a small initial amplitude of 74°, they are seen to be of the same type; but as the initial amplitude is diminished the longitudinal magnetic field in which the greatest damping of the oscillations takes place is increased; thus, with a starting amplitude of 90°, the greatest damping takes place when the wire is in a Brown—WMechanical Stress and Magnetisation of Nickel. 45 magnetic field of 24 units, which field is increased to about 30 units with an initial amplitude of 70°, and further increased to about 35 units when the amplitude at starting is 50°. The ordinates in fig. 3 are drawn to a much larger scale than those in fig. 6, and the hollows of the corresponding curve or the position of greatest damping in fig. 3 took place when a magnetic field of 35 units was round the . 90 80 _ 70 |\ al L 50 4 ] 70 40} IL 2|\ | Amplitude of oscillations in scale divisions after 80 vibrations starting from different initial amplitudes Fie. 6.—-Longitudinal Magnetic Field. wire. Though this latter wire was of larger diameter than the one used to get the results shown in fig. 6, the results are the same, as we know that for the same longitudinal load per unit cross-sectional area, the magnetic field in which the greatest internal friction takes place is independent of the diameter ot the wire. 46 Scientific Proceedings, Royal Dublin Society. The results given above show that the initial amplitude has a very distinct influence on the rate of subsidence of torsional oscillations: the greater the initial amplitude the lower is the longitudinal magnetic field in which the maximum internal friction in the wire takes place. The results obtained with the small initial amplitude of about 7° will bear more directly on any future explanation of the phenomena of magnetisation and torsion that we may attempt, because the angular displacement of the molecules of the wire is about the same both in the torsion and the subsidence experiments. That the main origin of the damping of the oscillations must exist aside the material of the wire, is, I think, shown by the following experiments. The mercury and the iron pin dipping into the mercury at the lower end of the vibrator were thoroughly cleaned and arranged so that the pin dipped into the mercury about one millimetre only, so as to reduce the mechanical friction to a minimum; the longitudinal load on the wire was the same as before, namely, 3 x 10° grammes per square centimetre, and a longitudinal magnetic field of 5 units was put round the wire. The following five sets of observa- tions were made on the rate of subsidence of the torsional oscillations, each starting from an initial amplitude of 90°: (1) when the wire was oscillating quite freely; (2) when the iron pin was dipping into the mercury, but the circuit open; (8) when the oscillating wire was short-circuited ; (4) when the wire circuit was closed through an inductive coil of 10,000 ohms resistance 5 (5) when the circuit was closed through a condenser of 3 microfarad capacity. In each of the five cases the resultant curves were identical. Section 4.—Influence of Diameter of Wire. It has been shown that when the longitudinal load per unit cross- sectional area on a nickel wire is constant, the longitudinal magnetic field in which the maximum twist of the free end takes place is independent of the cross-sectional area, and that the larger twist is obtained with the larger wire.. Experiments were therefore made on the subsidence of torsional oscillations, with nickel wires of different diameters, and in order to have them as nearly as possible in the same physical condition, they were tested in the state in which they were received from the manufacturer, who subjected all the wires to the same heat-treatment. Six different sizes of nickel wires were used—Nos. 20 to 148.W.G., inclusive—and were found to he very hard, the simple rigidity being 770 x 10° grammes per square centimetre; they were 226 centimetres long, and when under test each was loaded at the rate of 2x 10° grammes per square ! Scient. Proc. Roy. Dub. Soc., vol. xii., No. 37, p. 518. Brown—WMechanical Stress and Maguetisation of Nickel. 47 centimetre; and, as we know from page 34, above, with this load the greatest damping of the torsional oscillations will take place when the wire is subjected to a longitudinal magnetic field of 25 c.g.s. units. Hach wire was therefore tested for the subsidence of torsional oscillations: (1) when there was no magnetic field present; and (2) when a magnetic field of 25 units was round the wire; two sets of observations on the rate of subsidence were therefore made on each of the six wires, starting in each case from an initial amplitude of 300 divisions on the scale (the distance of which from the mirror on the end of the wire was 116°5 ecms.), or from an angular distance from the zero of 74°, the amplitudes being read off the scale at every fifth or tenth oscillation, until 70 complete vibrations had been made. If the results so obtained be plotted with the values of the cross-sectional areas of the wires as abscissa, and as ordinates the corresponding values of the amplitudes attained at the 70th vibration, the six points will be found to he in a straight line in the case of no magnetic field round the wire, and in a lower and practically parallel straight line in the case where the wire is surrounded by a magnetic field of 25 units. These curves, not here repro- duced, as well as the table below, show that when the cross-sectional area of the wire is increased five times, the decrease in the amplitude of torsional oscillation, after seventy vibrations have been made from the same initial amplitude, is 10 per cent., with no field round the wire, and 11-4 per cent. with a magnetic field of 25 units round it. The No. 16 wire was tested first in the hard state when its rigidity was 770 10° grammes per square centimetre, and, secondly, in the soft state when its rigidity was 708 « 10° grammes per square centimetre, this latter state being obtained by hanging the wire vertically under its own weight only, and raising it three times in succession to the temperature represented by a bright cherry-red by means of a broad Bunsen burner. The following table gives some of the results obtained with tle smallest and the largest wires, both in the hard state, and the results for the No. 16 Amplitudes of oscillation after 70 vibrations haye been mude, starting from an initial amplitude of 300 scale-divisions Longitudinal (when the cross-sectional area of the wire x 10~% sq. cms.) magnetic field are as follows :— round the wire, 6:50 22°17 22-17 32°35 0 260 244 103 234 2d 254 236 44 225 Hard. Hard. Soft. Hard. SCIENT. PROC. R.D.S., VOL. XIII., NO. 111. H 48 Scientific Proceedings, Royal Dublin Society. wire in both the hard and soft states, when there was no field round the wire, and when there was a magnetic field of 25 units round it. The extraordinary effeet of annealing will be seen from the behaviour of the No. 16 wire in the two states: in the hard state the final amplitude in a magnetic field of 25 units was only 3} per cent. smaller than in no field, whereas in the soft state the decrease in the amplitude is over 57 per cent., and this is produced by a decrease of about 8 per cent. in the rigidity. J am indebted to Mr. F. W. Warwick, B.a., B.u., of the Plrysies Laboratory in this college, for assistance in the observations and drawing of the curves in the latter part of this paper. SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.sc., F.L.s. (Plates I-III.) (March, 1911.) 1s. 2. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Groren H. Prruysriver, B.S0., PH.D. (March, 1911.) 1s. 8. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witt1am Brown, B.sc. (April 15, 1911). 1s. DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. ; TARISHS ROUEN A ek NG Red. Anat a AS) 2 Wht { AS sas yt Me ce se Wes no we acct by THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 4. APRIL, 1911. A THERMO-ELECTRIC METHOD OF CRYOSCOPY. BY HENRY H. DIXON, Sc.D., F.R.S., UNIVERSITY PROFESSOR OF BOTANY IN TRINITY COLLEGE, DUBLIN. [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1911. ——— ef a Price One Shilling. ( AUG 34391) | XM, } m “onal Mus Ws Roval Bublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749 EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to: the Editor. WE A THERMO-ELECTRIC METHOD OF CRYOSCOPY. By HENRY H. DIXON, S8c.D., F.R.S., University Professor of Botany in Trinity College, Dublin. [Read January 24. Ordered for Publication Frpruary 14. Published Aprin 20, 1911.] Iy some work! on the determination of the osmotic pressures of plant-juices I have found a thermo-electric method of measuring the freezing-points of small quantities of solutions so convenient and capable of such unexpected accuracy that I venture to think a detailed description of the method may prove of some use. On first thoughts it seems surprising that thermo-couples have not been in general use for determining the freezing-points of solutions. In the first place, itis evidently possible to make the thermo-electric method a differential one, viz., comparative of the freezing-point of the solution to be examined with that of pure water under the same conditions, and so it would seem most of the corrections necessary in the thermometric method would be rendered needless. ‘Thermo-couples have great possibilities of sensitiveness, e.g. it is by no means difficult to obtain by their use a deflection of the light- spot on a galvanometer scale amounting to 1 mm. for a difference of 0:0001° C. With this sensitiveness they can be made with a very small heat-capacity, and will consequently take up the temperature of their surroundings quickly. Their minute size and ease of manipulation contrast very favourably with the bulkiness and fragility of the ordinary freezing- point thermometers. Absence of parallax in reading the scale and the ease with which couples having various ranges may be constructed will also occur as advantages. Notwithstanding these attractions, I have not been able to find that thermo- couples have been used in eryoscopy, although in many researches their properties would be of value. This is probably to be explained by the erratic behaviour they exhibit when set up without special precautions. When a sufficiently sensitive galvanometer is used to give a good deflection for small temperature-differences, it is found also to be deflected by temperature-differences acting on accidental junctions in the circuit. These 1 Henry H. Dixon and W. R. Gelston Atkins, On Osmotic Pressures in Plants; and on a Thermo- Blectric Method of Determining Freezing-Points. Proc. Roy. Dub. Soc., vol. xii., No. xxy., p. 275. SCIENT. PROC. R.D.S., VOL. XUI., NO. IV. ii 50 Scientific Proceedings, Royal Dublin Society. junctions are usually formed at the binding-screws between brass and copper or between two different samples of copper. Strained places even in the copper leads may also act as thermo-junctions. Another source of trouble is strains in the galvanometer suspension, which lead to continual changes in the position of the zero on the scale. The slowness of the galvanometer needle to take up its final position may also be mentioned as introducing uncertainty in deciding on the true magnitude of the deflection. In view of these sources of error, it is evidently of great importance to have as few connections in the circuit as possible, and, where such connections are unavoidable, to secure that they are balanced by similar connections kept at the same temperature. In order to eliminate one usual set of connections from the circuit, i.e. that between the thermo-couple and the leads, in the apparatus which Mr. Atkins and I used, it was arranged to utilize the ends of the copper leads themselves as one pair of elements in the junctions. These leads, which had a diameter of 0:17 mm., extended right from the junctions to the reversing key (to be described later on). The other pair of elements of the couple were formed of the ends of a continuous iron, nickel, german silver, or ‘eureka’ wire. In most of the work on which we were engaged eureka-copper junctions were the most extensively used. The eureka alloy has a high thermo-electrie value when forming a junction with copper, and so is capable of giving a large deflection for a small temperature difference. Its comparatively great resistance enables one to adjust very conveniently the sensitiveness thus produced by increasing or diminishing the length of the eureka in the couple. Its low coefficient of variation of resistance with temperature secures that this convenient resistance introduces practically no error; and when, as in the apparatus to be described, it is enclosed in the freezing-chamber, the error is so small that it may be disregarded. The specific resistance of eureka is given as 47400 C.G.S. units; its variation per 1° C. as 0:0048 per cent. The construction of the eureka copper thermo-couple is simplicity itself. To each end of the silk-covered piece of eureka wire about 1 m. long a convenient length of the copper lead is soldered. The eureka wire I made use of had a diameter of 0:19 mm., and a resistance of about 16°5 ohms per metre. The soldered junctions between the eureka and copper may be neatly made by stripping a few millimetres of the ends of each from their silk coverings and dipping the bared tips into a solution of resin in spirit. After this treatment, if the ends in contact with one another are immersed in a tiny drop of molten solder, a very compact and good junction is made. Dixon—A Thermo- Electric Method of Cryoscopy. 51 To accommodate the couple to the apparatus the eureka wire before soldering was wound on a cork support (fig. 1s), leaving some 20 ems. of each end free. This cork support forms a connecting-piece hetween two drawn pine rods (p and 7, fig. 1) which are destined to carry the junctions and to keep them in position, one in a test- tube (@) containing the fluid to be ex- amined, and the other ina si milar tube (6) containing distilled water.? The two test-tubes, each about 1 em. in diameter, are supported in a large perforated cork bung (¢), which fits loosely in an outer large test-tube, which in turn is immersed in the freezing-bath, and forms the freezing-chamber (7). The perforated bung is held about the middle of the large test-tube by a metal rod (m) —a piece of stout brass wire—fixed into it and passing through another bung which closes the mouth of the large test- tube. The rod is prolonged above the second bung (d), and forms a handle by which both bungs may be removed simul- taneously from the freezing-chamber carrying the small test-tubes in the lower = —— == bung. The cork connecting-piece (s) carry- ing the eureka wire of the couple is Fie. 1.—a test-tube containing solution; & test-tube containing distilled water; » and p pine supports of the thermo-junctions ; s cork connecting-piece rigidly connecting y and p and supporting the eureka element of couple wound upon it; ¢ cork bung which is perforated to receive the test-tubes @ and 6, and into which the wire m is fixed. This wire works loosely in the cork s, but is fixed firmly in the upper cork bung @ which closes the freezing-chamber f. The pine rods r and p work loosely in perforations in d. qisastop which may be attached to one of the rods p to prevent the rods slipping out of the upper bung when the lower bung ¢ carrying the test-tubes is removed from the wire m; Z are the copper leads passing out of the freezing-chamber; H is the freezing-bath. 1 Tf a finer wire is used, the resistance may be disposed of by winding it round the lower end of the rod p, so that it remains immersed in the freezing distilled water. This eliminates any change in the resistance due to temperature Auctuation. 12 52 Scientific Proceedings, Royal Dublin Soctety. furnished with a wide median vertical perforation parallel to the two pine rods. When the pine supports are placed in the small test-tubes, the metal rod is passed through the perforation in the connecting-piece, and works loosely in it. Before fixing in the connecting-piece the pine supports are thoroughly impregnated with paraftin-wax by keeping them submerged for some time in melted wax near its boiling-point. The junctions and the wires coming from them are laid along the supporting rods thus prepared and fixed in the connecting-piece, and are bound to the rods, and the whole is waterproofed and insulated with several coats of collodion varnish. ‘The supporting rods are continued above the connecting-piece and are produced through corresponding perforations in the upper bung (d), in which the rods fit loosely. It is convenient that some kind of easily detached stop (q) should be fixed on one of the rods above the upper bung to prevent the rods slipping out of this bung when the test-tubes are removed. The copper leads (/) emerge from the freezing-chamber along one of the supporting rods. This arrangement, which will be easily understood by reference to fig. 1, allows the junctions in each of the smaller test-tubes to be simultaneously moved by raising and lowering the upper ends of the pine supports, when the upper bung is in position and the freezing-chamber is closed. ‘The double lead is easily introduced, or withdrawn at will, from the perforation in the upper bung by means of a narrow slit opening into that perforation from the side of the bung. From these arrangements it will be seen that the method has been rendered a comparative and differential one, and consequently it might be thought that corrections necessary for the thermometric methods may be partly or wholly dispensed with here. This is in part at least true, as will be understood from a consideration of the formula which Nernst and Abege have introduced embodying the corrections necessary in the thermometric method. It is k Pf te US RE x o) T, is the “ true” freezing-point of the solution under examination ; ¢’ is the observed temperature (i.e. the reading of the thermometer) ; ¢ is the so-called ‘“ convergence-temperature,” ie. the temperature which the solution tends to take up due to its loss of heat to the freezing-bath and its gain due to the stirring. This temperature depends on the heat-capacity, the con- ductivity, the size of the vessel and its contents, and also on the rapidity of the stirring and on the friction in the solution. 1 Quoted from Osmotischer Druck- und Tonenlehre. HU, J. Hamburger. Wiesbaden, 1902, vol.i., p. 66, Drxon—A Thermo-Electrice Method of Cryoscopy. a3 k indicates in the formula the velocity constant of the temperature exchange between the freezing-bath and the solution. It is dependent largely on the form of the apparatus and on the heat-capacity of the solution. i€ is the constant for the velocity with which the ice and the solution come into equilibrium, viz., it depends on the amount of ice present, its surface, its fineness of division, and the energy of the stirring. Ii we were dealing with two similar watery solutions in the thermo-electric method, it is evident that the convergence temperature depending upon the loss of heat to the freezing-bath and the gain by stirring is the same for the two tubes. In the comparative experiment, however, the actual temperatures, t’ of the formula, will of course be different for each, that of the water being the higher. Hence the error, represented by ¢’ — ¢, will tend to reduce the amount of the observed depression. k will be the same for both liquids. K will be different for the two. In the solution less ice will separate than in the water for a given temperature of the freezing-bath; but, at the same time, it 1s, in practice, found to be more finely divided. These two differences will act in opposite directions. The calibration-curve given in fig. 4, which is sensibly a straight line, shows that these errors practically neutralize each other, and that in the working of the method the galvanometer-deflection is proportional to the true depression of freezing-point of the solution examined. Bearing in mind the desirability of eliminating all needless junctions from the circuit, one would like to connect the leads coming from the junctions on the pine supports directly with the terminals of the galvano- meter. The importance of reversing the current through the galvanometer owing to shifts in the zero position of the mirror, and the advantages of being able to disconnect the couple readily from the galvanometer during various manipulations, render a key of some form or other necessary in the circuit. Such a break in the continuity of the leads involves a pair of junctions. Experience shows that even when the junctions are between two pieces of the same wire, thermo-electric effects are produced if they are not at the same temperature. In order to keep the two junctions as closely as possible at the same temperature, the following arrangement was adopted :— The leads coming from the couple are disposed so that their naked ends are exposed on opposite sides of a flat vertical support. It was my practice to stitch each naked end several times through a piece of thin cardboard in such a manner that when the card was bent and folded across the support the stitches made of the two wires lay on opposite sides of the support, 54 Screntifie Proceedings, Royal Dublin Society. Fig. 2 shows the arrangement. 7’ is an H-shaped piece of tinned iron about 5:5 cm. long. The cross-piece of the H is represented by a broad band about 3 cm. wide. It is covered by a piece of thin cardboard C about 1:2 cm. x 5 cm. This card carries three stitches of the ends of the leads on each side of its middle line. The ends of the card are folded round the eross-piece of the Hand the iron is folded in the middle along the dotted line (fig. 2.4), so that the ends of the card are nipped within the fold. Then the four ends of the H are bent out at right-angles to folded middle-piece, so as to form a stand to support the folded card in a vertical position (fig. 2 B). To prevent the ends of the leads making contact with the iron, two little plates of mica (J/, fig. 2 B) are slipped between the leads and the iron—one on each side of the vertical portion. The mica plates are held in position by the cardboard. Fig. 2.—A. Tinned iron support 7 and card C carrying the ends of the thermo-couple leads before folding. B. Side view of support 7 after folding. M plate of mica insulating bare end of lead from support. Connection between the ends of the leads exposed on this support and those coming from the galvanometer was made in the following way :—The bare ends of the galvanometer leads were fixed on the inner surfaces of the jaws of a spring wooden clip. When the clip was closed upon the vertical Dixon—A Thermo- Electric Method of Cryoseopy. 55 support of the thermo-couple leads, connection was established between the two pairs of leads, and the circuit was complete. By releasing the clip and rotating it round a vertical axis through 180°, and clamping it again on the support, the current from the couple may be reversed through the galvanometer. In this form of reversing key the junctions being of the same metal and —if desired—made of the same piece of metal, thermo-electric effects set up by temperature-difference at the junctions are reduced to a minimum. Notwithstanding this, it was found that these differences of temperature were a source of error. To maintain the junctions on the opposite sides of the support at the same temperature and so eliminate the error, these connections were made underneath liquid petroleum, contained in a beaker, on the bottom of which rested the support of the thermo-couple-leads. The petroleum was kept stirred during observations. It will be found convenient to have the galvanometer leads a considerable length, so as to allow a suitable distribution of the parts of the apparatus ; consequently it is essential that they should have a sufficiently large cross- section, so as to offer but a small resistance ; otherwise changes in tem- perature, from which it is impossible to shield them, will alter the sensitiveness of the apparatus. With the key described there is no objection to having the galvanometer leads of different copper wire and heavier than those coming from the junctions. Some special precaution is also needed to secure that the junctions at the binding-screws and those in the galvanometer are at the same tempera- ture. In the case of these connections it is all the more necessary, because elements of the junctions are of different materials—viz., brass and copper. It was found that the different temperatures of the opposite sides of the galvanometer in an ordinary laboratory could cause quite an appreciable deflection. ‘I'o remove this the galvanometer was placed in a thermostat, arranged to maintain a temperature of about 21° C. For this purpose I used one of Hearson’s incubators with a hole cut in the wooden door through which the beam of light illuminated the galvanometer-mirror, and was reflected back to the scale. The inner glass door was found not to injure the sharpness of the image of the cross-wire sufficiently to be objectionable. I found it necessary to stand the galvanometer on a stout glass plate on the copper floor of the thermostat, which otherwise slowly sagged under the pressure of its feet. The thermostat during my obser- vations, extending over a year, was maintained at temperatures which varied very slowly between 20°2° C. and 21°5° C., so that at any moment the parts of the galvanometer must have been very closely at the same temperature. 56 Scientific Proceedings, Royal Dublin Society. This constancy of temperature was probably also advantageous in maintaining the resistance of the galvanometer itself constant. The galvanometer employed is one of the Ayrton-Mather pattern, manu- factured by the Cambridge Scientific Instrument Company. Its resistance is 20°7 ohms. The deflection of the spot of light for one micro-volt, when the screen is 1 metre distant from the mirror, is 10 mm., and for one micro- ampere 206mm. A translucent screen was used to receive the spot of light from the galvanometer-mirror, which was illuminated with a Nernst-lamp. Fig. 3.—Plan showing disposition of apparatus. T thermostat containing the galvanometer G; LZ galvanometer lamp; S galyanometer transparent scale: A petroleum reversing key ; / freezing-bath on a separate table lower than that which supports the rest of the apparatus. Where one observer is using the apparatus, it will be found convenient to have the galvanometer leads so long that the petroleum key may be placed close to the screen, while the freezing-bath and thermo-couple, ete, may stand at a level 50 ems. below the screen and somewhat nearer the observer. This disposition brings the key, the supports of the thermo-couple, and the stirrer of the freezing-bath close to the observer, and he is in a convenient position for reading the position of the image of the cross-wire. The apparatus should be set up, and the thermostat and galvanometer adjusted, on the day before an observation is made. Once set up, no readjustment should be necessary. The freezing-bath is contained in the large cylindrical glass vessel, shown in fig. 1, H, with thick walls. ‘l’o prepare the bath the vessel is about a Dixon—A Thermo-EHlectrie Method of Cryoscopy. 57 quarter filled with salt solution, and then finely divided ice is added till the vessel is filled up to within about 3 cm. of the brim. A stout brass wire stirrer of the usual form is used to mix the brine and ice. Salt is added till the desired temperature is attained. This should be about 1:5° C. below the freezing-point of the solution to be examined. If the proportion of ice to the liquid is large, this temperature may be maintained constant by occasionally adding a little salt. A brass lid is fitted to the freezing-vessel, and supports the large test-tube which forms the freezing-chamber. It is also perforated to admit a thermometer into the freezing-bath and to allow the stirrer in the bath to project from it. To make an observation with the apparatus—say, to determine the freezing-point of a solution—the procedure is as follows: the leads of the thermo-couple are slipped through the slit andthe pine supports through the holes in the upper cork bung, and the stop is fixed on one of the supports above the cork, to prevent them falling down. The freezing-chamber is then closed with the cork. Meanwhile two small test-tubes, one containing about 2 cc. of the solution, and the other the same quantity of distilled water, are being cooled by supporting them in the freezing-bath, making use of the perforation in the lid through which the stirrer works. When it is judged that they have reached their freezing-point, a little hoar-frost 1s detached on a cooled platinum needle from the outside of the freezing-chamber and introduced into the distilled water. Ice crystals are immediately formed, and some adhere to the needle, which is then transferred to the salt solution. Crystallization is instantaneously started in this and the needle is withdrawn. ‘he two test-tubes are now put into the holes of the smaller cork, and it is fixed on to the lower end of the wire handle which passes down through the upper cork, and which has been removed from the freezing-chamber momentarily for the purpose. ‘The junctions on the lower ends of the pine supports are now immersed in the freezing-liquids in the test-tubes. Thus arranged the whole, test-tubes and thermo-couple, is put into the freezing-chamber and the upper cork tightly adjusted. Stirring of the freezing-fluids is immediately commenced by moving the pine rods up and down. As these are rigidly connected together, the two test-tubes are subjected to precisely similar conditions in this respect. ‘The freezing-bath is also kept stirred. The galvanometer may now be put in circuit with the thermo-couple by fixing the clip on the support in the petroleum key; and the petroleum is occasionally stirred. Immediately on making the contact the spot of light travels from zero. At first its motion is rapid, but becomes slower and slower till at last it moves with an almost imperceplible creep. It comes to rest about 60 secs. after contact is made. It will be found SOIENT, PROC, R.D.S., VOL, XIII., NO, IV, K 58 Scientific Proceedings, Royal Dublin Society. convenient to allow 75 secs. to elapse before making a reading. During this time the stirring of the test-tubes is actively kept up; for it is surprising how quickly the ice rising in the salt solution allows the lower layers round the junction to become supercooled. In the other test-tube the same does not occur, as the ice soon forms a lining lying against the wall of the test-tube, and the junction is supported in water surrounded by ice. When the first reading is made, the clip is disconnected and the galvanometer mirror swings free. Reversed connection is made when the spot of light is at the limit of its swing on the side on which the first deflection was recorded. In this way the suspension of the galvanometer is kept from any sudden strain which might be produced by suddenly checking its movement. After 75 secs., during which the same active stirring is kept up, a second reading is made. This first observation after putting in the solution should be regarded merely as a preliminary one; but still if too much ice has not been present, it will give the freezing-point within a couple of hundredths of a degree. The test-tubes are now raised from the freezing-chamber, and the one containing the solution momentarily touched by the finger to give it a little heat. When the upper cork is readjusted and stirring recommenced, it will be noticed. that the spot of light retires towards zero. If all the ice is not melted, it will quickly recover its former position; and the test-tube should again be touched. When it is certain that all the ice is melted in the solution, it is left in the freezing-chamber and allowed to cool. Meanwhile connection is broken by removing the clip from the support in the petroleum key. When it is judged that radiation has cooled the solution nearly to its freezing-point, connection is again made by the clip, and stirring is recom- menced. ‘The spot of light then travels to near its previous resting-place, or possibly beyond it. Supercooling may proceed, and the spot of light will slowly travel indefinitely beyond its previous position, or crystallization may supervene, and the spot will return somewhat on its path and tend to take up a steady position. In the latter case connection is broken at the clip, and the mirror allowed to swing free. Connection is again made, and, after 75 secs., during which vigorous stirring is kept up, a reading is made. The current is then reversed, and, at the end of 75 secs., another reading is made on the other side of the zero point. Ii, however, supercooling proceeds, and crystallization does not automatically occur, it is necessary to inoculate the solution with a little hoar-frost. ‘The inoculation should be carried out when the spot of light has definitely passed the limit of the first deflection. If it is allowed to cool too much, too much ice will separate, and the concentration of the solution left over will cause too large a depression ; if, on the other hand, it is inoculated just at its freezing-point, so little ice separates that the solution Drxon—A Thermo-EHlectric Method of Cryoscopy. 59 in parts may continue for some time supercooled, and we may get too great a deflection. Experience shows that the smallest depression is obtained if the solu- tion is allowed to cool 0:1° to 02° below its freezing-point before inoculation. It will often be found that the mean of the second pair of readings indicates a somewhat larger deflection than that of the first pair by about 1 per cent. This seems to be due to the slow cooling of the support of the junction in the solution. It will be found that readings after the junctions have been in the freezing-chamber about 15 min. do not tend to be greater than the preceding ones. In the natural routine the second pair of readings are made about 15 min. after the junctions have been put in position. A third pair of readings made in a similar manner will plainly show if the apparatus has reached a steady state. If the observations have been satisfactory, they should not diverge from one another by more than 3 per cent., and with care greater accuracy may be attained. To calibrate the apparatus sodium-chloride solutions of known strength are introduced into one of the test-tubes. ‘The deflection produced by the depression of the freezing-point of each is observed. These depressions being known by the work of Raoult, Loomis, Nernst, and Abegg, we obtain the value in degrees centigrade of a millimetre deflection of the light-spot. The following table exhibits the figures of one of these calibrations. ‘The individual readings are recorded to give some idea of the accuracy of the arrangement :— The scale reads continuously from left to right : 250 mm. marks its middle point. | 26 Observation I. Observation IT. Observation III. S| 35 No. | S| ag |S a Sse : al =; oma lei: z | SS | Se Sol. ets, 22 | oS | S| 48 oe | se} 6 45 2s | as 3 8 | au Sg OS | BE lee | @ | Ae | Sa | Se & les |i | ae Ss les 5398 | a= Le Ve tS VS 1B Se | os Be LO oS 3 AEE 1S = [ a | =| = a ca S a I aay ) Ey ays ee LE = ia a on | | | ws or| T. | 8:500 | 479:0 | 2371 | 251-0 | 227-9) 480-0 | 22:8 | 951-4 | 228-6 | 480-5 | 23-0 | 251-7 | 228-7 | 228-4 | 2-060 | | | | | IL. | 3:000 | 451:0 | 57:3 | 254-1] 196°8 | 449-3 | 58-3 | 253:8 | 195°5 | 449-0 | 56-0 | 252-5 | 196-5 | 196-2 1:765 | TIT. | 2:500 | 417-0 | 92:5 | 254-7 | 162-2 | 417-0 | 92-8 | 254-9 | 162-1) 418-0 | 98-5 | 255-7 | 162-2 | 162°2 | 1-474 | | | IY. | 2:000 | 382-8 | 124-0 | 253-4 | 129-4 | 383-0 | 124-0 | 253-5 | 129°5 | 383-6 | 124-0 | 253-8 | 129-8 | 129°6 | 1-181 | | VY. | 1:500 | 349-0 | 154-0 | 251-5 | 97-5 | 349-0 | 153-3 | 2521) 97-8 | 849-0 | 154-0 | 251-5 | 97-5) 97-6} 0°886 VI. | 1:000 | 317-0 | 187-4 | 252-2| 64-8 | 317-0 | 187-3 | 252°1| 64:8 | 317°6 | 187°3 | 252°4 | 65-1] 64:9 | 0596 | | | In this table are recorded the two positions of the spider-line in the spot of light on the scale for three successive observations of the freezing-point of each solution. The deflection corresponding to this freezing-point is obtained by subtracting the second from the first, and halving the result. It will be seen that deflections obtained in this way diverge only slightly from the moe i Grammes of Sodium Chloride in 100 grammes of water. 60 Scientific Proceedings, Royal Dublin Socvety. which is given in the second-last column. ‘The greatest divergence is not z percent. In the final column are given the actual freezing-points of the solutions derived from Raoult’s results quoted from Hamburger (/oc. cit.). Depression of Freezing-point in hundredths of degree centigrade. 50 100 (SO 200 250 SPE pameielsos BREE we es 40 25 20 05 Jt —I el 50 100 150 200 250. Deflection in millimetres. Fig. 4. It will be noticed from the positions recorded in the table that the position of the zero shifted considerably during the observations. In the first series, i.e., those on solution I., the zero point lay about 251 on the scale, while during the first observation on solution II. it was near 254. These shifts of zero show the importance of being able to reverse the current, and of obtaining the deflection by two readings, one on each side of the zero position. A graph of these observations is given in fig. 4. The ordinates correspond to. the concentration of the solutions, and the abscissee are the measures of the deflections in mm., caused by the difference in temperature of the freezing- Dixon—A Thermo- Electric Method of Cryoscopy. 61 points of the solutions and that of water. The dotted line is a similar graph of Raoult’s freezing-point determinations. The concentrations are plotted against the depressions of the freezing-point. In the second graph the abscissa correspond to hundredths of a degree centigrade. The couple on which these observations were made had a length of 126 cms. interposed between the junctions, as it was desired that it should give about 1 mm. deflection for a temperature difference of 0:01°C. The actual deflection was found to be 110-9 mm. for 1:00°C. Fer some time after being made, the thermo-couple used in these observations changed its constant considerably, owing probably to some progressive change in the metals of the junction and circuit. After nine months, when the constant was re-determined, it gave a deflection of 1304 mm. per 1°C. It had then become nearly stable, and observations during the next three months showed that its deflection varied between 129°2 mm. and 133-0 mm. per degree. The smaller fluctuations are possibly due to changes in the resistance of the circuit connected with changes of temperature. They show the need of re-determining the constant of the couple during each series of observations, just as the zero change of the Beckman thermometer necessitates a control-experiment in the thermometric method. With regard to the temperature of the freezing-bath, it would at first sight appear of little importance in this differential method, as, no matter what its temperature is, it will tend to produce the same ‘ convergence temperature’ in each test-tube. It has, however, been found to have an appreciable effect on the magnitude of the deflection corresponding to the freezing-point of a given solution, as will be seen from the table below, in which are recorded the deflections corresponding to the freezing-point of a solution of 1°5 gm. NaCl in 100 gm. of water, having a freezing-point of 0:886°, when surrounded with a freezing-bath of different temperatures. Temperature of Bath. Deflection. — 1:0° 113°6 mm. -—1°5 1165°2 — 2:0 116°9 — 275 117-7 —30 118-1 — 40 118°8 From these figures it appears that when the freezing-bath is less than 1:2° below the freezing-point of the solution under examination, a small alteration in the temperature produces a greater effect on the deflection than when the bath is about 1:5° below the solution. It consequently seemed best to adjust the freezing-bath about 1:5° below the suspected - temperature of the freezing-point. 62 Scientific Proceedings, Royul Dublin Society. As has already been pointed out, the influence of the temperature of the freezing-bath on the apparent freezing-point deflection is due to the difference in the behaviour of water and salt solutions on freezing. In the latter the crystals remain separate and the ice is finely divided. The difference of density between it and the solution causes it to rise up somewhat more rapidly, teuds to aggregate it at the upper surface, and so permits the lower layers of the solution to supercool to a small extent. In the distilled water, on the other hand, the ice adheres to the walls of the tube, and forms a lining to it, so that supercooling of the lower layers is less favoured. The convergence temperature and the constant / of Nernst and Abege’s correction are dependent largely on the heat-capacity of the solution, and consequently it is of importance that the two test-tubes should contain approximately the same amount of liquid ; otherwise the rate of exchange of heat between the solution and the freezing-bath and the water and the freezing-bath will be different. But this is no serious difficulty within wide limits. Thus the deflection due to the depression of freezing-point of a solution containing 1:5 gm. NaCl in 100 gm. of water was found to be 115°6 mm., when the solution and the water stood at a level of 3°3 cm. in similar tubes; it was reduced to 115°4 mm., when the depth of the salt solution was increased tod cm. Of course it is easy to arrange that both tubes should contain the same amount, and so have practically the same heat-capacity. Change of resistance of the circuit due to temperature-changes is guarded against by completely immersing the eureka or nickel of the couple in the freezing-chamber, while the resistance of the galvanometer is kept constant by its being enclosed in the thermostat. The complete immersion of the connecting-piece of the couple in the freezing-chamber also secures the elimination of thermo-electric effects due to want of uniformity in this wire. From what has been said, it appears that the thermo-electrie method is capable of considerable accuracy, even when only two junctions are employed. Of course if it were desired to work to greater accuracy, there would be no reason why the number of junctions should not be increased, thus greatly increasing the galvanometer deflection for the same temperature interval. In the work in which we were engaged, however, this would have been undesirable, as a comparatively large range was required. But even with a pair of junctions, the hundredth of a degree could be measured with certainty. With this accuracy very small quantities of fluid may be dealt with. ‘Lhe small quantities required render the method particularly suitable to physiological work. Its differential character might also be applied with advantage to comparing the freezing-points of different fluids ; for example, in a comparison of jugular and carotid blood. 1 SCIENTIFIC PROCEEDINGS. VOLUME XIII. . A Seed-Bearing Irish Pteridosperm, Crossotheca Honinghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, p.sc., F.L.s. (Plates I-III.) (March, 1911.) 1s. . Considerations and Hxperiments on the supposed Infection of thej Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Gurorce H. Puruysrier, B.SC., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Influence of (April 15, 19 Oscillations in Nickel and Iron Wires when subjected to. the Longitudinal Magnetic Fields. By Witu1am Brown, B.so. 11). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, so.p., F.r.s.. (April 20, 19 DUBLIN : nm\s ls. PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 5. MAY, 1911. A METHOD OF EXACT DETERMINATION OF THE CONTINUOUS CHANGE IN ABSOLUTE DENSITY OF A SUBSTANCE, te. WAX, IN PASSING THROUGH ITS FUSION STAGE. BY WILLIAM J. LYONS, B.A., A.R.C.Sc. (Lonp.), ROYAL COLLEGE OF SCIENCE FOR IRELAND. [COMMUNICATED BY PROFESSOR W. BROWN, B.SC.| {Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN : PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, ans 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.@. “ 1911. 1 fi . AK wat onal VV ie Price Sixpence. Se ae eae! ‘saonlan Insty? Roval Bublin Society. Oe FOUNDED, A.D. 1731. INCORPORATED, 1749 Ee EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be get down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Kditor. 8] V. A METHOD OF EXACT DETERMINATION OF THE CON- TINUOUS CHANGE IN ABSOLUTE DENSITY OF A SUBSTANCH, u.c. WAX, IN PASSING THROUGH ITS FUSION STAGE. By WILLIAM J. LYONS, B.A., A.R.C.Sc. (Lonp.), Royal College of Science for Ireland. [COMMUNICATED BY PROFESSOR W. BROWN, B.SC. | [Read Frsruary 22. Ordered for publication Marcu 8. Published May 16, 1911.] Introduction. ‘HE simple apparatus described in this paper was designed some time ago for the purpose of examining the volume-change which occurs on fusion in the case of waxes. In such cases the melting-point is not definite; and it was thought that the volume-temperature curve would indicate effectively the limits of temperature within which the change of state occurred more or less continuously, and would also reveal by the discontinuity of the curve the purity or otherwise of the wax. For such purposes the change in volume had to be observed continuously and for very small differences in temperature; hence the dilatometer-form with graduated stem was adopted. The appa- ratus gave very satisfactory results as to the relative change in volume during fusion; but it was soon recognized that a slight development of the method would enable exact determinations to be made of the density of the substance at any temperature above or below the fusion-stage, and would give absolute values of a high degree of accuracy. The method is now being employed by the author in a systematic investigation into the change n density on fusion of a number of organic compounds which form isomeric and homologous series; but it is thought desirable to make a preliminary communication describing in detail the apparatus and its use, and the results obtained for some samples of wax.! 1¥For an excellent bibliography of the whole subject of change of volume on fusion, see Chwolson’s “‘ Traité de Physique,’’ 1910. ‘Tome III., Second Fascicule, p. 652. SCIENT. PROG. R.D.S., VOL. XIII., NO. V. L 64 Scientific Proceedings, Royal Dublin Society. General Principle of the Method. The apparatus consisting of a bulb at the end of a capillary tube (see fig. 1) is filled at first with mercury; and the expansion of the mercury in the glass is determined by observations on the movement of the meniscus along the stem as the temperature is altered through the required range. The greater part of the mercury in the bulb is then removed and replaced by the substance to be examined ; and the expansion of the substance and the remaining portion of the mercury in the glass is again determined by the movement of the meniscus through a range of temperature from a little below to a little above the fusion-point. The conditions of temperature and stem-exposure being the same in both eases, it is easy to obtain from the two sets of observations, and with certain weighings, the volume of the known mass of substance at any temperature for which observations were made. The reduction of the observations resolves itself into finding at any particular temperature what mass of mercury in the bulb would at this known temperature have the same volume as that occupied by the substance. If this mass be divided by the known density of mercury at this temperature, the volume of the substance is obtained. No corrections need be applied for the expansion of the glass envelope, nor for expansion of the stem of the dilatometer. Fie. 1. Particulars of the Apparatus and Method. Apparatus.—The bulb, which may be of a flat or cylindrical form, is connected to the capillary tube, which is bent in the form shown in fig. 1. Lyons— Volume Change on Fusion. 65 The upper part of the bulb is drawn ont to a short and very fine capillary, the top of which is at first open and must lie at a lower level than that of the horizontal stem. The flat form of the bulb is convenient for examining the changes in appearance of the substance in its stages of fusion, and has the advantages of rapidly taking up the temperature of the bath. The cylindrical form is, however, less likely to be affected by changes in pressure, and is preferable where an exact determination at some definite temperature is required. | The stem is calibrated, and the mass of mercury required to fill one centimetre at the temperature of the room is found. It will be convenient to refer to this mass as (c). The apparatus with suitable means of suspending it from the balance is weighed empty at first. This weight will be called w,. The bulb is next filled with mercury by connecting the end of the stem to a small hand exhaust-pump, the open tip of the capillary above the bulb being placed under the surface of clean mercury. When the apparatus is filled, the pump is detached, the bulb is placed erect, and the mercury adjusted so as to fill the stem to a convenient position. By carefully drawing a bunsen flame across the tip of the capillary, the bulb is quite easily sealed. The apparatus thus filled with mercury is weighed (w,). The mass of mercury in the bulb (w, — w,) will be referred to as (M,.) The apparatus is now adjusted, so that the bulb and bent portion of the stem is immersed in a bath of water, glycerine, or oil, and the stem is fixed horizontally in contact with a millimetre-scale etched on mirror-glass. A mark X on the stem is put to a fixed division on the scale, so as to make the seale-readings always correspond to the same point on the stem. ‘The bath is heated and the temperature regulated by a very sensitive xylol or toluol thermostat. The liquid is kept well stirred by two small propellers driven by a little electric motor. ‘The bath is heated and cooled through a range, such as will include the temperatures for which the apparatus will be subsequently employed. ‘The reading of the meniscus is observed at the different temperatures by means of a low-power lens. The reading in the ease of this initial expansion of the mercury in glass will be referred to as (R,). To introduce the substance into the bulb, the capillary at A must be opened by breaking off the point or fusing the top, when the internal pressure of the mercury will make an opening. ‘his may be effected so as not to appreciably alter the weight of the apparatus and the mass of mercury. We shall assume, however, that under the most unfavourable conditions the capillary is broken off, and if necessary drawn out again. he apparatus 1,2 66 Scientific Proceedings, Royal Dublin Society. is weighed, and filled as before with mercury, the bulb being left open. Let us suppose that at the temperature of the room or of cold water (¢° C.), the mercury fills the bulb and stem to the point 6. The apparatus and mercury are weighed, and the mass of mercury now in the bulb is determined. We shall refer to this as (/). The little flask shown in fig. 1, provided with a two-holed rubber stopper, is now attached to the end of the stem, and is also connected to the small exhaust- pump. ‘The bulb is immersed in a beaker or suitable vessel containing the substance in a liquid state, at a temperature about 10° above its melting- point. The open tip of the capillary will lie under the surface of the liquid by reason of its being at a lower level than the stem. On exhausting, the substance is admitted into the bulb, and the mercury withdrawn and caught in the flask. If any bubbles of gas collect in the bulb, they are quickly removed by forcing back the mercury. When the bulb is about three-. fourths full, the top of the capillary is brought outside the liquid and sealed. The pump and flask are detached; and at this stage or at the end of the experiment, the weight of the apparatus and its contents of substance and mercury are found, and also the weight of mercury expelled and caught in the flask. This latter mass will be referred to as (m); and the mass of the sub- stance in the bulb, which is easily got from the previous weighings, will be called W. The bulb is finally placed in the bath, and the stem adjusted to the millimetre scale as in the preliminary experiment. The bath is heated and stirred, and the temperature is regulated and changed through the necessary range from about 10° above to 10° below the melting-point; the reading (2) of the meniscus is made at the different temperatures. ‘The temperature is altered very slowly, especially during fusion; the thermometer and the reading & must be found to remain constant for some time before the reading is recorded. The observations are taken first when the substance is cooling, and then when it is being heated through the same range of temperature. The same bulb may be used for several determinations; and at the end of a test it can be readily emptied and cleaned as follows :—he top of the capillary above the bulb is broken off, and the bulb is immersed in boiling water to which some caustic soda is added. ‘he stem is now attached to a small pump which may be used for exhaust and compression. By alternating the action of the pump, the bulb is soon emptied of wax and filled with the boiling solution, and all greasiness is soon removed. It is well to clean the apparatus finally with distilled water, ether, and, if necessary, with nitric acid and distilled water. Lyons— Volume Change on Fusion. 67 Reduction of Observations to determine at any Temperature T° C. the Volume (V) of one gramme of the substance. We have the following data :— Mass of mercury filling one centimetre of stem =o Density of mercury at any temperature from tables = Mass of mercury in apparatus in the preliminary experiment = MM, Reading of meniscus at any temperature Z'°C. in this preliminary experiment = 1% Mass of mercury in the apparatus previous to introducing substance Si Reading of meniscus corresponding to WM at the known temperature of cold water ¢°C. = 0 Mass of mercury expelled on introducing substance = i Weight of substance in bulb during test = W Reading of meniscus at any temperature 77°C. when the substance was in the bulb = ih The reading &, showing the expansion of mercury in glass in the preliminary experiment is plotted against the temperature. A straight- line graph is obtained from which the value of 2, at any temperature may be found. ‘The coefficient of apparent expansion of the mercury and the coefficient (g) of real expansion of the glass may also be found in the usual way. The mass of mercury J, previous to introducing substance, filled the bulb and stem to the mark 6 at the temperature ¢°C. Let the reading R, corre- sponding to the mass of mercury J, in the original bulb be equal toa at PC. The change in volume (%) of the bulb at ¢ C. due to altering the capillary above it will be M,+(6-a)o-M pt At any other temperature 7° C. tis alteration in the volume of the bulb is Op =%{l+g9(L-2)}. As already pointed out, it is possible to arrange to have the bulb alteration v so small as to be negligible. It is in all cases very small, and the variation with temperature of the corresponding mass of mercury » x p, or Up + Pr — Ut» Ptr is of a very small order. At any temperature 7° C. the substance ( /) in bulb and a mass of mercury 68 Scientific Proceedings, Royal Dublin Society. M —m filled the apparatus to the division R. If the same bulb under the same conditions of temperature and stem-exposure had been completely filled with mercury, i.e. if the substance at T° C. had been replaced by mercury at T° C., the mass of mercury in the apparatus filling tt to R would have been equal to M, - vp. pr+ (R - RB) o. Hence the volume Q, of a mass W of the substance at 7'° C. is equal to the volume at 7° C. of a mass of mercury equal to [ a, — Up. prt (R = Ry) o | = (i - mn), or ae Q,=— | M, -— (= m) = o7- pr + (R= Ro} Prt and for the volume of one gramme we have a or {or V= Pao Wn — (Il = m) = vp. pr + (Rk — R,) o| Tf the original bulb had not been altered, and if I= I/,, the final expression would have been simplified to 1 Va gE ae + (BR - h,)o |. In the more general case, however, it will be noted that My, — (M =m) - vp. pr will be constant during a particular test. If this constant () be determined at first, the values of V, the volume of one gramme at a number of different temperatures, can be readily calculated by such a tabulation as the following :— Vol. of one gramme PO ® |i. (RSP\al Pp [K+ (R= B)o| p,W General Remarks. The special advantages of the method above described are, first, that there are no corrections to be applied for the expansion of the envelope, and no errors due to exposure of stem outside the bath; secondly, the shape of the dilato- Lyons— Volume Change on Fusion. 69 meter allows the substance to be introduced in the liquid state with the greatest facility, and also renders easy the sealing of the bulb. The precision of the method, as estimated by the possible errors due to observation, may be illustrated by the following example :—In the examination of bees’ wax, the mass of mercury required to fill the bulb was about 36 grammes, and o, the mass required to fill one centimetre of stem, = °0357 grms. It was found that at 70° C. an observational error of 1 mm. in reading R would have made the value of V = 1:1929 instead of 1:1930. It was quite easy to read F& correct to 5 mm.; and asthe weighings might be carried if necessary to four decimal places, the final results might be regarded as correct to this degree in the absence of any constant or systematic sources of error. ‘he chief and practically the only source of systematic error is the effect of variation of external or internal pressure on the volume of the bulb. When the bulb is cylindrical and strong, the effect of pressure must be very slight, and in most cases negligible. If the bulb be of the flat form, and thin-walled, the conditions of internal pressure being very approximately the same when the bulb is filled with mercury as when it contains the substance in the liquid state; the errors due to the pressure effect will be extremely small in the final results. When, however, the substance solidifies, it might, under certain conditions, cause abnormal internal pressure effects ; but in the case of waxes a little below their melting-points, such effects are not likely to arise owing to the continued plasticity of the substance. As to the external pressure and its variation with the barometer and depth, corrections may be applied in the manner adopted in accurate thermometry. Such corrections would only be necessary in cases of extreme accuracy. Kxamination of some Waczes. To illustrate the application of the method to the study of solid fats and waxes, the following results, obtained for three samples of wax, are given. The samples consisted of (1) what may be regarded as genuine yellow Bees’ Wax; (2) what is referred to as “ White Wax”; and (3) a mixture composed of one part of the former to two of the latter by weight. ‘The ‘‘ White Wax” was purchased in plates as “ Cera Alba, B.P.,” but as it differed in its density, melting-point, and refractometer index from the values quoted for the B.P. wax, it is, In consequence, referred to here as “ White Wax” rather than Cera Alba.” The values of the volumes of one gramme and the density are given in the accompanying tabular statement, and the former are graphically represented in fig. 2. _'The appearances in the bulb were carefully noted during the period of fusion, and were found to correspond to marked changes in the form of the 70 Scientific Proceedings, Royal Dublin Society. volume-temperature curves. Thus in the case of the ““ White Wax” at 56° C. on cooling, minute specks appeared in the bulb ; the corresponding point im the graph is marked (4). At 53°3° C., the point in the curve marked (0), a sudden clouding of the whole mass took place, a granular structure being, however, observable in the mass for some time after. On heating, the “ White Wax ”’ showed signs of a granular structure a little above 50°C. It was semi- transparent at 54° C. (c), and just clear at 55°2°C. (d). CHANGE OF VOLUME on Fusron. He 1-225 IAX. fa ee ul a = = ae aaaie : < a | - ee 5 WT ian | 1-200 it Ww 4 ir =I Zz | A B , cS Allez fe (o}} r ; | CAL : A 1-175} 433 4 + zs = E 7 S | SSI / IL f\ 1 Z 1-150 j— - 4 es all Lt =! 1-125 + + 4 ob (ee L TEMPERATURE oC. oq hg ol a BS el Gap GS ep elo of eS eS q GQ O 1-100 é. Fie. 2. In the case of the cooling of Bees’ Wax, traces of a crystal-like deposit appeared at the bottom of the wax at 68° C. (g). The deposit was dark, and the general mass of the substance remained clear till 61°8° C. (2), when it suddenly became clouded. On heating, the Bees’ Wax became sensibly translucent at 60:4° C. (7), and at 63°4° C. (7) it was possible to read print through the bulb. The “ Mixture,” on cooling, showed no signs of freezing till 57°5° C. (e), at which point a wisp-like cloudiness suddenly appeared throughout the bulb. Lyons— Volume Change on Fusion. 71 On heating, it did not become clear till a temperature of 58°5° C.(f) was reached. Bers’ Wax. Wuitt Wax. MIxTuRE. ° Volume of 9 Volume of p Volume of Meee: one gramme, Diem one gramme. Donate one gramme. pens 46 ee — || 1-1688c.c. -8667 || 1:1386c.c. | -8783 48 = a 11723 “8530 || 1°1545 “8662 2 ___ || 4 11929 +8383 : wy (11924 {-sss6 | 11737 S40 : conra || f 172050 8299 || ( 1-1855 “8435 o2 USAONS CG: ene 11-2040 tease H{ 11843 espe : pe 1:2109 -8258 || ( 1-1928 “8384 Oe IS Soi { 1-2099 Neca Aen { +8392 5 : : 5 12014 “8324 56 1:1267 8875 || 1-2130 8244 H Fea { (8333 4 pie : : { 1:2090 “8271 58 1-1403 8779 || 1:2148 8232 |I{ 1.5086 { oor 11550 “8658 ‘ S 4 oe 60 Honey { epee | wales 8218 || 1-2116 8254 11854 “8436 pee : a0 62 { Hea { Bain || uae 8205 || 1-2136 8240 1-187 8429 a ; : vane 64 { 11868 { even || ieee g192 || 1-2158 8225 66 11894 “8408 || 1-2227 “8179 || 1-2180 “$210 68 11912 -8395 || 1-2247 “8165 || 1-2202 8195 70 11930 “8382 || 1-2269 *8151 || 1-2025 -8180 Conclusions. It was found in all cases that the process of fusion, as shown by the appearances in the wax, and by the irregularity of the curve, lasted over a considerable range of temperature. A marked loop in the curves indicates a considerable “ iag” effect between the volumes on cooling and heating during the fusion stage. ‘I'his effect is reduced by making the temperature alter very slowly, but it does not disappear, even when a very long interval of time is allowed to each temperature. ‘The loop in the case of Bees’ Wax is very marked, and was repeated with regularity on taking the wax through several eycles of temperature. SCIENT. PROC. R.D.S., VOL. XIII., NO. V. M 2 Scientific Proceedings, Royal Dublin Society. The thermal expansion of the waxes in the liquid state was quite uniform for the range studied; but below the melting-point, the expansion of the solid did not follow a linear law. The expansion of the solid below the melting-point was very much greater than that of the liquid above it. The graph for the Mixture is very similar to that of its major component the “ White Wax.” The lower limit of the fusion stage is practically the same forthetwo. The upper limit is much below that of the Bees’ Wax, and only 3:5°C. above that of the White Wax. The Mixture seems to behave as if the Bees’ Wax were dissolved in the “ White Wax.” The method described in this communication, with slight modifications of the apparatus, may be used for a variety of determinations, and would probably be found as accurate as, and much simpler than, some methods now inuse. ‘lhe apparatus might obviously be made with short stem for the simple determination of the density of a liquid ata definite temperature. As we have seen, the method enables us to get exact values of the densities of solid fats and waxes, and it seems more accurate for such purposes than those usually employed in Organic Analysis.! It may be effectively used for the determination of coefficients of thermal expansion of liquids, and also of solids, and would give the real and not the apparent expansion. Lastly, it might be employed for determining “ transition points” in many cases where the usual form of dilatometer is found difficult to fill and troublesome to use. 1 See Lewkowitsch, ‘‘ Chemical Technology and Analysis of Oils, Fats, and Waxes,’’ 1909, vol.i., chap. v. bo SCIENTIFIC PROCEEDINGS. VOLUME XIII. . A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, p.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Guoren H.‘ Peraysrmnes, B.SC., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wiuram Brown, B.so. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, sc.p., rr.s. (April 20,1911). 1s. . A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wriitram J. Lyons, 8.4., a.R.c.sc. (Lonp). (May 16,1911). 6d. DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 6. JUNE, 1911. RADIANT MATTER. BY JOHN JOLY, Sc.D., F.R.S., PROFESSOR OF GEOLOGY AND MINERALOGY IN THE UNIVERSITY OF DUBLIN. (PLATE Illa.) [Authors alone are responsib/e for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. ow gonian ins tit, 7 f ct 1911. foc eee Price One Shilling. Roval Mublin Society. FOUNDED, A.D. 1781. INCORPORATED, 1749 EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 pm. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. VI. RADIANT MATTER: By JOHN JOLY, 8c.D., F.R.S., Professor of Geology and Mineralogy in the University of Dublin. (Puare III a.) [Ordered for Publication May 9. Published Jung 9, 1911.] Raptanr matter is, in many respects, the most important manifestation associated with radioactivity which modern research has brought to light. This claim is justified by facts which it is my purpose in this lecture to deal with briefly and in outline. We shall commence our studies by observing and detecting for ourselves the existence of radiant matter. I have projected upon the screen the image of a gold-leaf electroscope. ‘here is a curved celluloid scale just beyond the range of the leaf, but in the same plane, so that its divisions and the image of the leaf are alike clearly defined upon the screen. ‘There is in the base of the electroscope a small opening. It is now closed by a slip of glass about one millimetre thick. We notice first that the leaf is practically stationary. It retains its charge so perfectly that even with the help of the scale we cannot see any movement. I now place just beneath the slip of glass covering the aperture a speck of a salt of radium. Observing the leaf carefully, we perceive a slow movement indicating a gradual discharge. The loss observed under these conditions is due to rays of two kinds which are given out by the radioactive substances present: rays known as Band y rays. They pass with facility through the glass, and confer upon the air in the electroscope the properties of a conductor of electricity. We cannot here fully discuss the nature of these rays. It is sufficient to recall that they are very penetrating—more especially the y rays; that the latter are probably of the nature of the X rays, and represent the transmission of a pulse or shock in the ether; and that the former are of the nature of the cathode rays which have been shown by Sir J. J. Thomson to consist of negatively electrified particles moving at a very great velocity, and possessing amass about the thousandth part of that of an atom of hydrogen. ‘Lhese particles are very certainly subordinate parts of the atom, and are expelled i A Lecture delivered before the Royal Dublin Society on February 8rd, 1911. SCIENT. PROC. R.D.S., VOL. XIII., NO. VI. N 74 Scientific Proceedings, Royal Dublin Society. in certain phases of radioactive change. As they are not radiant matter in the elemental sense, they do not now concern us. There is, however, another sort of ray coming from the radioactive substance which is stopped by the glass slip, and hence has not, as yet, affected the electroscope. When I now remove the glass slip, there is a rapid —a very rapid—collapse of the leaf. You perceive at once that this sort of ray, although not so penetrating as the ( or y rays, inasmuch as the glass completely stops it, is far more active in discharging the leaf. These highly active rays have been named by Rutherford (to whom we owe the greater part of what we know about the subject) the a rays. When I reinsert the glass slip, the rapid motion of the leaf ceases instantly, and is replaced by the slow movement due to the penetrating rays. This observation is important. It is known that radium is transformed into a highly radioactive gas—the emanation. The striking effect upon removing the glass might be supposed to be wholly, or in part, due to the diffusion or convection of this gas into the electroscope. The fact that the rapid collapse ceases immediately we reinsert the glass slip, negatives this explanation : for if the emanation had got into the electroscope, its effect must continue after we closed the opening, seeing that this gas preserves its vigorous effects for some days. The next experiment 1 shall make is to substitute for the glass slip a very thin cleavage flake of mica. This is not sufficient to completely stop the arays. We notice a fairly rapid collapse of the leaf. It is evident, then, that while a glass plate one millimetre thick completely stops these rays they pass through the thin flake of mica. Lastly, it is easy to show that a few centimetres of air are quite as effective as the glass plate in stopping these rays. Thus, when I leave the aperture open, but lower the radioactive salt about 8 or 10 centimetres below it, the only perceivable effect is that due to ( and y rays. The explanation “action at a distance,” when one body affects another in its neighbourhood, is, fortunately for the progress of science, not now regarded as sufficient. In such cases three alternatives present themselves. There may be some change transmitted in the intervening medium (ethereal or material) or there may be something of the nature of projectiles cast out by the active body. If the latter is the explanation, we have to admit that these projectiles can pass through solid matter as we have seen the 3 rays readily do. Not having time to enter upon the sequence of observations which led to the elucidation of these rays, I must briefly state that the projectile theory is now universally accepted, and that the truly atomic nature of the a ray has Jotyv—Radiant Matter. 75 been established. In 1906 Rutherford showed that the a rays from all sorts of radioactive bodies are alike in mass; and he gave the strongest reasons for believing that they are, in fact, helium atoms in an electrified state. He showed that these radiant atoms carry a positive charge, and suggested then, what he has since more fully established, that this charge is in quantity double that which monad atoms carry when ionized. No more fundamental discoveries in the science of matter have ever been made. The consideration of Sir J. J. Thomson’s beautiful method of determining the mass and velocity of such elusive objects as are carried in these invisible streams of radiant matter, by observing the effect of electric and maguetic forces upon their direction of motion, would require not less than the greater part of the time allotted to me. Their chemical nature once determined gives us, however, their mass directly from our previous knowledge of the element. Rutherford’s final proof that those rays are helium atoms is based upon their power, while they are in the radiant state, of penetrating a thin screen of solid matter. The gaseous body derived from radium, the emanation, is one of the radioactive elements, which, in the act of transmutation, gives out arays. Rutherford compressed some of this gas into a glass tube, so thin that the a rays could dart through its walls, just as we found they penetrated a thin mica plate. Surrounding this thin tube was a second tube in which the spent a rays collected, as bullets which have dropped behind a target. After some time a spectroscopic test of the contents of the outer tube showed a brilliant helium spectrum. The proof is complete that these rays are helium. Other evidence also exists. One most interesting fact must be mentioned. Wherever in the rocks radioactive bodies are found—and they are almost ubiquitous—there helium is also found. It probably represents the stored-up a rays. The extraordinary phenomenon of the passage of these atoms through solid screens finds its explanation in the high velocity with which radiant matter is projected from radioactive substances. Their speed, as a material speed, is by far the greatest known. It may amount to as much as 13,000 miles per second. That is to say, an a ray if unimpeded in its flight would circulate round the earth in less than two seconds. The greatest material velocity previously recorded is that of matter projected from the surface of the sun when violent disturbances take place in his highly heated gases. Velocities up to 500 or 600 miles per second have been in this case surmised. Once we recognize the enormous speed of the a ray, we are rather inclined to change our point of view, and wonder less at the penetration ot . n2 76 Scientific Proceedings, Royal Dublin Society. solids by such missiles than at the remarkable potency of the solid in absorbing the kinetic energy. One-tenth of a millimetre of glass would stop them all. The absorbing body does not, however, oppose the bombardment with impunity. Violent work is done upon the opposing atoms, many of which are, in a sense, partially dismembered. The influence of these fast-moving atoms on the matter through which they pass is revealed in their power of conferring on the air in the electroscope the properties of a conductor of electricity. The air in the electroscope, if we could quite shelter it from all external influence, would, possibly, be a perfect insulator. When the rays from a radioactive body or from the X ray tube enter it, it becomes, for the time being, a conductor. Now we know that if, say, a negative charge resides in the gold leaf, this must get an equal positive amount of electricity in order to be neutralized or discharged. ‘The view that best explains the action of radiant matter and other rays, and harmonizes with many observed facts, is that which assumes the creation by their means of free — and + charges in the gas. To account for the former, it is supposed that an electron is torn from the disturbed atom of the gas. This electron carries the unit negative charge. Its removal from the atom leaves the latter charged with an equal positive charge. The atom in this state is said to be “ionized.” A single a ray will give rise to about 100,000 ions in the course of its flight in air. Under normal conditions such ions and electrons created in a gas speedily reunite by mutual attraction. But this reunion is hindered if a sufficient electric force exists. Thus in the electroscope, if the leaf carries a negative charge, the electric force between it and the walls of the electroscope draws the ions to the negative leaf, and drives the electrons to the walls. So long as the radiation continues, however, fresh ions and electrons are being made in the gas. ‘Thus there is a continuous flux of positively electrified atoms to the gold-leaf, and hence its gradual neutralization and discharge. Ionization, or the creation of a free charge upon the atom, is well known to attend many chemical actions. We may say that the a ray does chemical work upon the air in the electroscope. The effect of these rays upon a photographic plate is similar to that of light. Jonization also takes place here, we may be sure; and as the medium is in the solid state, the ions do not recombine as they would in a gas, and the effects of the rays accumulate. Similarly many substances—such as glass—become coloured when acted upon by radiant matter. We must regard the a ray as an influence of transcendent subtlety; remembering that, in virtue of its own atomic dimensions, it has power to deal directly with the atom it encounters, Joty—Radiant Matter. 77 spending its relatively enormous kinetic energy in shaking and disrupting the harmonious balance within the opposing atom. It has been suggested that it acquires its own electric charge at an early stage of its encounters (shortly after quitting the disintegrating atom which gives rise to it), asa result of its aggressiveness, the bombarded atoms retaliating by knocking off two of its electrons. Such a loss of two unit negative charges would account for the double ionic charge which it apparently possesses. Although ionization by these rays within solids into which it penetrates must be, to a certain extent, matter of inference, we shall see later the strongest evidence that these rays, indeed, act in this way upon molecules aggregated in the solid state. The conditions under which radiant matter comes into existence are set forth in the table of the genealogies of the radio- active element. According to the theory put i HEU (eres forward by Rutherford and Soddy, a radioactive Uranium Gxl0 years. element spontaneously ‘transforms into another and different element. It is, from internal causes, Ueamen Xe 24-6 days. unstable. A new atom, derived from a preceding one, at the moment of its birth possesses a certain /owium —> a 5x10 years. “expectation of life.” When this period is over, | it, in turn, is transformed into another body. This Radium a : 2x/0°years. “expectation of life,’ or average longevity, is an important distinguishing feature of the several cy,yaroy—>a 5-85 days. substances. Some, on the average, live a long time ; some only a short time. Uranium possesses V/ z Faoium A> & 3 minutes. an expectation of life of about 9000 million years. Radium A endures on the average but 4:3 minutes. DeBoer It follows that in the case of the longer-lived bodies | only a very small portion of the total number of a : Raion C SB 19-5 minutes. atoms present transform each second; in the case y of the shorter-lived bodies the fraction is rela- Y 7 15 ; tively large. Raoiun D years It will be evident that if a quantity of a parent y substance—say, uranium—has been for a long 72/7 ESB 4 8.days: time (some thousands of years) in the rocks, it i) must accumulate all the several descendants to “gw F>% — HOdays. (Polonium) which it gives rise. ‘These, however, will not accumulate in indefinitely large amounts, for, with the exception of the final stable substance, they are being transformed as well as formed. ‘here will be a certain amount of any one particular element (on which we fix 78 Scientific Proceedings, Royal Dublin Society. our attention), formed each second, depending upon the chain of events leading back to the parent substance, and, of course, upon the amount of this parent substance. Its rate of formation being then fixed, evidently the expectation of life and dependent death-rate, or fraction of the atoms perishing per second, must determine the amount which can be present : just as the population of a city must depend upon the number of people born and the number which die every year. When the whole sequence of events is working smoothly, each element steadily forming and being transformed, the amount of each body present is called the equilibrium amount. The amount of radium in equilibrium with one gramme of uranium is 3:4 ten-millionths of a gramme—a quite unweighable quantity. Boltwood, Strutt, McCoy, and others have verified the fact that this is always the quantity of radium found associated with one gramme of uranium. The existence of these equilibrium amounts of the several elements is the test of the radioactive theory. Inthe instance cited, it is of considerable practical importance, for it enables a ready and sure estimate to be made of the amount of radium existing in an ore of uranium when the percentage of the latter element has been determined. It requires some pliability of mind, at least on the part of the older generation, to recognize that these successive substances are, indeed, distinct and definite chemical elements. But such they are. ‘lhe case of radium and the substance, emanation, to which it gives rise is particularly interesting . Radium is a metal of the alkaline-earth type, and nearly akin to the fairly common element barium in its chemical relations. It resists volatilization at high temperatures. Radioactively, it is relatively stable, its atoms enduring on the average 2,900 years. Hmanation is a gas, only condensed to the liquid form by extreme cold. Chemically, it is highly inert. Radioactively, it is very unstable, the average life being but 53 days. Here the substances differ physically, chemically, and radioactively in the most marked manner: the emanation as widely diverging from the body giving rise to it as the butterfly from the longer-lived chrysalis from which it emerges. In the transformation of one element into another those external manifesta- tions arise which occasioned the discovery of the whole matter. Sometimes these take the form of radiant matter; sometimes of the @ and y radiation. In a few cases changes can be inferred although no radiation appears, The fact that an atom of a well-recognized element, such as uranium, expels an atom of another definite element, helium, is obviously one of profound significance, the far-reaching nature of which it is impossible to predict. It has certainly completed the downfall of the tottering edifice of the earlier atomistic ideas, and has assisted to furnish those labyrinths which Jotyv— Radiant Matter. 79 science recognizes as existing within space-conditions approximating to those ’ of a mathematical point. It is worth noticing how the discovery of the chemical nature of the a ray harmonizes with such atomic weights of these new elements as have been so far determined. The atomic weight of uranium is 238-5. ‘here is a loss of three a rays before radium is reached. As the atomic weight of helium is 4, this involves the loss of 12 units of atomic weight. The atomic weight of radium should, therefore, be 2265. ‘This figure closely approximates to the results of the best determinations. Again, radium loses an a ray and becomes emanation. The atomic weight of the iatter should therefore be 222°5. Recent investiga- tions—more especially those of Gray and Ramsay—give results approximating closely to this figure. In the uranium series of changes eight a rays are lost altogether. ‘The residual body must possess the atomic weight 206°5. Now, this is nearly that of lead; and Boltwood has accordingly suggested that the final body is indeed that element. As ages pass over, the parent substance must diminish in amount. Finally, it must all disappear, and all its descendants along with it, save the stable body to which it ultimately gives rise. ‘The radiated matter, the helium, also survives. ‘The disappearance of all the uranium will take an immense time. Six thousand million years will see one half the present store of uranium used up; another six thousand million years will be required to reduce it to one quarter, and so on. When we hear such statements as the foregoing, we are inclined to think that the radiant matter must be evolved at a very slow rate. The figures regarding the rates of emission of a rays create a very different impression on the mind. ‘Thus, Rutherford, who has succeeded by a most ingenious method in counting the individual a rays projected from radioactive matter, has shown that one gramme of uranium, with all its products of change associated with it—that is, in fact, as we find it in the rocks—emits nearly 100,000 helium atoms per second; more exactly, 9°67 x 10*. One quarter of the number of these departing helium atoms signals the downfall of the uranium atoms—the transmutation of entities which have lasted probably some thousands of millions of years. The new atoms will never again be uranium; but in the course of a few thousand years, during which they run down the scale of energy, they again find an enduring stability. It is an impressive thought that, notwithstanding this rapid loss of atoms from a single gramme of uranium, so vast an interval as the half-period must elapse before one-half the number of atoms present have been transformed. The major part of the heat which radioactive substances continually generate in the rocks, the geological significance of which is so important, is due to the 80 Scientific Proceedings, Royal Dublin Society. absorption and conversion to heat of the kinetic energy of all these countless atoms of radiant matter; and I may here remind you that radiant matter possesses yet another geological application of interest. It enables estimates of geological time to be arrived at by the careful measurement of the amount of stored helium, and a comparison of this with the quantity of the primary substances, uranium and thorium, present. Strutt, by a series of laborious and brilliant researches, has carried this method to its consummation. We must now study some circumstances attending the flight of radiant matter. We first notice the interesting fact that the velocity with which helium is cast out by radioactive bodies at the moment of change varies considerably from one element to another. Thus the radiant atoms of radium CO possess a far higher velocity than those of uranium or ionium. This fact is apparent in the greater distance to which the a rays of the former will penetrate in air or in any other substance. ‘The distance traversed in air is known as the “range.” The following table shows the ranges of a rays from the various known radioactive elements. ‘Thus we see that whereas the helium from Ra C is projected nearly 7 centimetres, that from uranium only reaches 2'7 centimetres. In the thorium series, one of the elements, Th C, attains a range of 8°6 centimetres. This is the longest known. Rance in Arr. cms. cms. Radium C ; G06 Thorium C : o BG Radium A ; ote Thorium X ; o | G2 Kmanation ; 5 ales} Th Emanation . ORO) Radium F ; > BES Thorium B 5 4 5:0 Radium F os 4: Radiothorium . 5 RY) Tonium A PBS Thorium F ORD Uranium c o «PY cms. —__ Actinium X . , i , Se OZO0 Act Emanation A f ‘ a BS) Actinium B. 4 5 ; RO ZO Radioactinium ; 5 : >» eS} By a most ingenious series of observations, Bragg has revealed some unexpected and interesting features attending the ionization effects of the a rays upon gases through which they are projected. By measuring the amount of ionization effected at different points along the path of the ray, Bragg and Kleeman have shown that at first, when the velocity is greatest, the ionization effected is least, and that the amount of ionization—that is, the number of ions created—greatly increases just before the atom comes to rest. Joty—Radiant Matter. 81 Let the ray be supposed to move along the line 4 B—this line representing the range. If at each point of its path we erect a perpendicular line proportional to the number of ions created by the flying helium atom, then, by joining up the ends of these lines, we obtain the curve shown. It will be Tonisation. A 2 4 ee Be ne Range in ems. of air. noticed that a very well-defined maximum exists, after which the ionization rapidly drops to nil. The curve reproduced is due to Geiger, who has added considerably to our knowledge of the subject. I hold in my hand a small speck of the substance, pitchblende—the uranium ore from which radium is derived. All the elements of the uranium series are present. We are sure, then, that every a ray proper to this series, whose ranges are given in the table, is being emitted by this particle of pitchblende. Let us form a mental picture of what is going on around it. Furthest out of all, the helium from Ra C is projected. It attains a distance of 7 centimetres. The greater part by far of its ionization is done near the end of its flight. Hence, remembering that these rays are darting radially in all directions from the piece of pitchblende, there is a shell of intense ionization of spherical form existing around this pitchblende and at a distance of between 6 and 7 centimetres from it. This is entirely due to Ra ©. Within this shell we have a spherical shell due to Ra A. It is the next we meet as we go inwards. It has an extreme diameter of 48 cms. The next shell is created by emanation. Its radius is 4°2 cms. The shell due to Ra F succeeds at 3:8 ems.; then comes that made by radium, and lastly a very intense one due to the nearly coincident effects of three rays, two due SCIENT. PROC. R.D.S., VOL. XIII., NO. VI, 9 82 Scientific Proceedings, Royal Dublin Society. to uranium and one to ionium. ‘I'he weight of this particle of pitchblende is about voth of a gramme. [If all its rays escaped freely at its surface, some 9,600 a rays would leave it per second, and the number of ions created in the air per second would be about 960 millions. The diagram shows the successive shells, as they could be formed in air, to natural scale. RADIUM @. We shall now pursue the study of radiant matter within the confines of another branch of science—that which deals with the nature, origin, and structure of tle rocks. We gain this much by the transfer, that the invisible effects we have just. been endeavouring to picture to ourselves, as taking place Joty—Radiant Matter. 83 around a radioactive body in equilibrium, may be studied at our leisure, visibly inscribed in the ancient rocks. We require the microscope, however, in order to carry on our observations. Tf we extract a flake of brown mica from the granite near Dublin and look at it through the microscope, we find here and there dark, circular or disk-shaped marks. In the centre of each is a small crystal. This in most cases is the mineral zircon, which became enclosed in the mica at an early stage in the formation of that mineral. The dark area extends around the zircon like a darkened border, and, if the crystal is small enough, takes on the form of a perfectly true circle. The remarkable occurrence of these dark circular spots, or “ pleochroie haloes,” as they are called, has been known to more than one generation of petrologists, and has always excited interest. heir origin has till lately been unexplained. Sollas, some years ago, prophetically stated his belief that they were to be ascribed to the presence of some rare earth in the zircon. | When the minerals of the rocks were searched by Strutt for radioactive bodies, it was found that zircons were intensely radioactive—a concentration of uranium haying in some manner taken place in these early formed bodies. The minerals apatite and allenite are also sometimes conspicuously radioactive, and around these, also, haloes often exist. Let us then suppose that the halo is due to the radioactivity of the minute erystal around which it extends. We know that the radioactive elements in the zircon discharge helium atoms at high velocity into the surrounding mica. If these a rays have power to affect the mica by ionization, just as they colour glass or affect a photographic plate, then there will be a certain region affected extending just so far as the rays can penetrate and no further. It will be a test of this explanation if the radius of the circular marks is found to be just the correct distance to which the rays could travel in mica. Now Bragg and Kleeman have determined the principles upon which we may estimate from the observed ranges in air the range of a rays in any substance the chemical nature and density of which are known. Accordingly we may calculate the ranges of several a rays in biotite. The table below gives the results. Rance ny Biorrre. mms. mms. Radium C : > O08 Thorium C. Pn O:040 Radium A : nO ,025 Thorium X_.. 0026 Emanation . ee OsO20) Th Emanation ~ 0:025 Radium F : . 0:018 Thorium B. . 0:023 Radium ; > - OLY Radiothorium 0.018 Tonium 3 5 (OXO)I6} Thorium : ee O:016 Uranium : 5 Ordls 02 84 Scientific Proceedings, Royal Dublin Society. We see, as might have been expected, and as indeed I showed you at the beginning of this lecture, that the mica is much more effective in stopping the rays than is the air. The extreme penetration of the rays from Ra C is only thirty-three thousandths of a millimetre—a distance invisible to the This should be the limiting radius of a halo formed from the unaided eye. If the thorium series was responsible, then elements derived from uranium. we might expect haloes having a radius extending to the range of Th C, that is about forty-thousandths of a millimetre. Now these are just the dimen- sions we find in the rocks when, by suitable appliances, we measure the sizes of haloes. Some have a radial dimension of 0:033 mms., and are then easily” identified as due to the uranium series, and some scale 0:040 mms. : these are thorium haloes. Manyscores of measurements confirm these results. Actinium haloes are not found; and this fact supports the inference already alluded to, that this element is derived from uranium as a very subordinate derivative, its effects being masked by the much greater vigour of the radiations from the radium series of elements. There is, then, no doubt, from the foregoing evidence alone, that haloes are the result of radiant matter. capillary It is of much interest to note that Rutherford has generated the equivalent of a halo in glass. In the course of experiments in which he had radium emanation contained in a capillary tube, the halo developed as a coloured border around the capillary, the radial dimensions being just such as corre- sponded with the penetration of a rays in glass. In the figure, which I owe to the kindness of Professor Rutherford, the central dark band is the capillary, the bordering narrow shaded area, the halo. It may also be mentioned that the experimental application of radium to Joty—Radiant Matter. 85 biotite produces just such a darkening of the mica after some months as we see in the natural halo. The circular or disk-like appearance of the halo is due to the fact that it is presented to us as the cross-section of a sphere. ‘he true form is spherical. This is proved by the fact that when a crystal of mica is cut across the cleavage, the form is still circular, (Plate IIIa, Fig. 2). This shows that the a rays are projected equal distances, or at least produce equal effects, along and across the cleavage—a fact not without considerable interest in itself, for it would hardly be expected on first consideration. In the haloes which we have seen upon the screen, there is no differentiation between the effects of the slower-moving rays and those which move faster. ‘he effects of the former must lie inside those due to the latter. The obliteration of the inner shells or spheres of ionization is explained on the same principles as account for the loss of detail upon an over-exposed photographie plate. In the case of over-exposure the contrast is lost because the effects of the lower lights have overtaken those of the higher lights, a uniform blackening ultimately resulting. If the radiant matter has been acting intensely on the mica for a very long time, the several shells of ionization are merged in the accumulation of the feebler effects which are always progressing at all points along the path of the ray as shown in the Bragg curve. We should expect, however, to meet cases where, either from the smallness of the quantity of radioactive material, or from the recentness of the formation of the rock, there is a proper or correct exposure, so that the successive shells of ionization, which we may picture to ourselves as surrounding a particle of pitchblende in air, would, as developed in the mica, be made visible to the eye. In this anticipation we assume that Bragg’s laws apply to the ionization of a solid. Now, we do, indeed, find the several spheres of ionization—or at least many of them—beautifully depicted in certain minerals; and thus we, at one and the same time, find additional, indeed overwhelming, evidence that the haloes are due to a rays, and also, what would be hard to establish experimentally, that Bragg’s laws govern the effects in the solid medium. Here is a group of well-exposed haloes in the biotite of Co. Carlow. (Plate IIIa.) You see the outer ring due to Ra CO, and the gap of feebler ionization between it and the shell due to RaA. We even find some which are actually ‘under-exposed.’ These often have got no further than the record made by the intense triple effect due to uranium and ionium. I show you this photograph again, but this time with an engraved scale of 86 Scientific Proceedings, Royal Dublin Society. hundredths of a millimetre which was photographed without disturbing the microscope; so that it is possible for you to verify the fact that the dimensions of the fully formed haloes are all over the plate alike, and just that which the radiaut matter from the uranium series of elements would account for. It is possible to trace the development of haloes by observation of those arising from a feebler and feebler central radiation. A succession of photographs taken to the same enlargement reveals that the imnermost sphere is first formed. ‘Then this widens under the rays from radium and emanation; and the outermost sphere, for some unexplained reason, often becomes conspicuous before Ita A has produced much effect. ‘The effects of the latter rays sometimes appear as a distinct ring. We find a striking comment on the immense age of the haloes and of the containing rocks by a study of these objects; for it is easy to show that the growing haloes we have now been looking at are the accumulated effects of ionization acting with extreme slowness. It is calculable directly that, even if we supposed the minute nuclei of some of these haloes to consist, not of zircon, but of the most radioactive ore known, pitchblende, the rate of expulsion of the a rays has, owing to the smallness of the quantities of radioactive substances involved, been less than eighty in a year. But this is not all. Some of the nuclei are identified with certainty as zircons. If we ascribe to these a radioactivity even greater than Strutt found in his highest measurements, one or more years would have elapsed between one expulsion of consecutive helium atoms and another. But geological time is long; and we may still recognize in the feeblest haloes the work of many millions of atoms of radiant matter, each exerting its own small effect, but these effects carefully preserved and accumulated. In short, we recognize the halo and detect its nature and origin on the same principles as we recognize by their light-effects accumulated upon the photographic plate the presence of stars invisible to the eye. We find, then, in the rocks a record of the laws of radiant matter in the handwriting of the radiant matter itself—a record which took many millions of years to inscribe. aloes are not found in the younger rocks. We must clearly recognize the halo as the result of the integration of effects of unimaginable feebleness; and as we see them in the archwan granites, they probably date their beginnings from times long antecedent to the appearance of life upon the globe, not less than 100 million years ago. They assure us, therefore, of the remote antiquity of the atomic instability which calls radiant matter into existence. But even more they tell us of the enduring stability of the ordinary elements. If the common and abundant Jo~ty—Radiant Matter. 87 elements which occur in and around the mica emitted radiant matter, even at the slowest rates, the clear transparency of the mica must long ago have vanished, and the whole become obscured under the effects accumulated during the ages which have elapsed since the formation of the rocks. We seem entitled to conclude that the atomic stability and instability which we observe to-day have immutably prevailed during geological time. [ExpraNaTIon or Pare, EXPLANATION OF PLATE IIIa. Fig. 1. Radium haloes in cleavage plate of biotite (Co. Carlow); enlarged about 76 diameters. Two overlapping haloes are present, as well as a few under-exposed haloes. 2. A radium halo (lower right-hand part of the field) and a thorium halo (upper left-hand part) in brown mica in a granite. The mica is cut across the cleavage. Hnlargement about 114 diameters. The thorium halo shows an inner sphere due to Th X. The ratio of the diameters of inner and outer spheres will be found to be as 2°6 : 4:0. (See p. 83.) 3. Radium haloes in Biotite (Co. Carlow) x about 95 diameters. The more intense ionization within the sphere due to Ra A is conspicuous in many of them. Careful scaling will show that the ratios of the diameters of the inner and outer spheres are as 23 : 88. (See p. 83.) Seen on cleavage. 4. A single radium halo from the Carlow biotite. It is enlarged to about 500 diameters. The inner dark disk is due to emanation. The Ra A sphere succeeds and appears to be less developed than that of Ra C. Viewed on cleavage. 5. Developing Radium haloes in Carlow biotite. Magnification about 76 diameters. Various stages of development are shown. Four haloes are in the field. Viewed on cleavage. 6. Same as fig. 5. Two haloes in very different stages of development are present. The faint early indications of Ra C in this and the last photograph are delicately shown. Viewed on cleavage. QCWENTN, IIROG: IRs IOWNBILIUN SOY, NES, WO, Sl SAGE ee ilileneae PLEOCHROIC HALOES. SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1.JA Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. JoHNson, D.s¢., F.L.S. (Plates I.-ITI.) (March, 1911.) 1s. 2. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Guorce H ! Pernysrmer, B.SC., PH.D. (March, 1911.) 1s. 8. Mechanical Stress and Magnetisation of Nickel (Part IT.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields) By Wim Brown, .8.so. (April 15,1911). 1s. 4. A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, sc.p., F.R.s, (April 20, 1911). 1s. 5, A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wittram J. Lyons, 8.a., a.R.0.sc. (Lonp). (May 16,1911). 6d. 6. Radiant Matter. By Joun Jony, so.p., r.z.s. (June 9,1911.) 1s. DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 7. JUNE, 1911. THE INHERITANCE OF MILK-YIELD IN CATTLE. BY JAMES WILSON, M.A., B.Sc., PROFESSOR OF AGRICULTURE IN THE ROYAL COLLEGE OF SOIENCE, DUBLIN. {Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIELY,—— LEINSTER HOUSE, DUBLIN. “Nnsomian | WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.0, j 1911. y is “onal MV yseut, J Price One Shilling. Roval Dublin Society. OS FOUNDED, A.D. 1731. INCORPORATED, 1749 EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the” Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. [ be] WUE THE INHERITANCE OF MILK-YIELD IN CATTLE. By JAMES WILSON, M.A., B.Sc., Professor of Agriculture in the Royal College of Science, Dublin. [Read May 28. Published Junn 12, 1911.] Untit recently it was the common belief that variation among domestic animals was a slow and gradual process, and that, if a breed was improving, the increments of improvement from generation to generation were small and frequently imperceptible. Holding this belief, the general policy of stock-breeders was to persist in breeding not only from such stock as were obvious advances, but also from such as were believed to be potential advances, upon their parents. So, our present breeds were believed to have been “developed ” from an ancestry by no means noteworthy in attainments. In each breed a few stock-breeders were usually pre-eminently successful, and stock of their breeding or of their “blood” were largely sought after by others less successful. If a great sire or dam could not be secured, then his or her son or grandson, or a descendant still farther removed, was considered more desirable for breeding purposes than another animal equally good or even better as such, but less illustrious in pedigree. A near descendant of some great sire or dam was always more desirable, of course, than another more remote, for it was considered more likely to have inherited its ancestors’ ten(lency to improvement. This policy no doubt raised the general average, increased the number of animals that were up to the average attainment, but it also produced many disappointments, many that ‘‘harked back” to remote and less improved ancestry, although these were forgotten in the occurrence of others high above the average of their day. The difficulties of this policy were greater when applied to dairy than when applied to “beef ”’ breeds or to horses bred for strength or speed. In these other cases the characters that determined whether a young animal was likely to fulfil the purpose for which it had been bred were more obvious. here was a method by which good dairy stock might have been told, SCIENT. PROC. R.D.S., VOL. XIII., NO. VII, P 90 Scientific Proceedings, Royal Dublin Society. and so improved as quickly as other stock; but this method was not adopted till quite recently. Breeders persisted in relying upon what they took to be the outward signs of good dairy cattle rather than adopt the only sure and reliable method by which they could be identified. Some of the signs they relied upon are, no doubt, of value, as, for instance, the character and size of the udder; but others, such as the wedge-shaped shoulder, the long, thin neck, the long head—in some breeds it has to be short—and a general un- willingness to lay on “ flesh,” or, rather fat, to say nothing of such things as athin tail or the way the hairs are turned upon the udder, are open to serious doubt. As an instance of the unreliability of one of these signs only, and that, perhaps, the most important, since it involves some of the others, it need only be mentioned that cases of Aberdeen Angus cows giving five and six gallons of milk a day, and of others giving over a thousand gallons of milk during a normal lactation have been recorded, while a well-known Irishman rears three or four, and sometimes even five, calves upon Hereford cows within the year. There being thus few data in the United Kingdom upon which any theory as to the inheritance of milk-yield could be built up, the present inquiry was begun some five or six years ago by a visit to Denmark, because it was known the Danes had raised the milk-yield of their cows greatly in recent years, and it was hoped a study of their methods might throw some light upon the problem. Staats Consulent Morkeberg of Copenhagen gave ready and kind assist- ance in explaining the method, in suggesting districts and farms to be visited, and in giving introductions to individual breeders. Staats Consulent Appel of Aarhus also wrote about the Danish method, and gave advice as to districts and farmers to be visited. Two years ago an opportunity occurred of meeting Mr. Morkeberg again and discussing some of the points once more. The foundation of the Danish method was the keeping of milk records. Upon the evidence furnished by these came the knowledge that many cows were not paying their way or were occupying room that others might occupy to greater profit. ‘hen arose the demand for the sons of good milking cows as stock-bulls. It was seen from the records that good milkers were usually the daughters of good milkers, and poor milkers the daughters of poor ones. It was seen also that some bulls left better daughters than others; and although, for the want of records, it would not have been easy to prove in the early days that the sires of good milking daughters were usually the sons of good milking dams, it was generally agreed that it was safer to err on the side that presumably had most chances in its favour and assume that milk-yield Witson—The Inheritance of Milk- Yield in Cattle. 91 was inherited through the sire as well as through the dam. Eventually it became widely accepted that the bull’s pedigree as regards milk was of vital importance, and, when the selection of a particular sire was under considera- tion, his milk-pedigree, so to speak, was examined as far back as it could be given. At no time, however, was there any suggestion from Denmark, or from Holland or Sweden, where records had also been kept systematically, that there was any reason to question the theory that improvement was a slow and gradual process. But it was clear that, as time went on, the confidence of stock-breeders in the system of selecting the progeny of good milkers for stock purposes rose higher and higher. The visit to Denmark, therefore, did not result in any change of view with regard to the inheritance of milk-yield further than to emphasize the importance of keeping milk records in order to know which stock should be eliminated and which should be bred from. Three years ago, when it became apparent that Mendel’s laws applied to colour, horns, length of limb, and other less important characters in cattle, one of the first questions that suggested themselves was, Is milk-yield also inherited in some Mendelian manner ? and the inquiry was begun at once. But the great difficulty was to find data. Two or three years before that time, a number of Ayrshire breeders had commenced to keep records, and an appeal was made to the late Mr. John Speir, who had been at the head of the movement. On Mr. Speir’s recommendation, a number of Ayrshire brecders were visited, but their records were not old enough to yield sufficient data, One very important point, however, was brought out in conversation with Mr. Speir, namely, that in a number of cases, where a daughter was an improvement or the reverse upon her dam, the difference between their yields was not small, but large. Cows giving four or five hundred gallons might have daughters giving six or seven ; cows giving six or seven might have daughters giving nine; and vice versa. Poor milking cows usually had poor milking daughters, and good milking cows good milking daughters; but the rule was by no means invariable. At the same time Mr. Speir had no doubt of the power of a bull to improve or damage a herd, and to leave daughters of very unequal capacity. Unfortunately no note was taken of the cases Mr. Speir had in his mind, as it was never thought but that he would be alive to be referred to again and again. Some of his cases are referred to in his Milk Record Reports, published in the Transactions of the Highland and Agricul- tural Society of Scotland during the years 1904 to 1910, and others in a lecture on “ Milk Records,” delivered in December, 1907, and published by the Scottish Agricultural Publishing Company. In dairy literature of recent years much had been written of the great P22 92 Scientific Proceedings, Royal Dublin Society. advance made in America in breeding high-yielding dairy stock, and advantage was taken of the meeting of the British Association at Winnipeg, in 1909, to make inquiry into the question in Canada and the United States. Herds were visited at a number of colleges and experiment stations as well as at some farms in both countries. But here again there was littie more information to be gained. The records were not old enough. Besides, many of the American records are confusing, for the reason that they usually state the butter-yield rather than the milk-yield for a lactation or for a year. The butter-yield depends mainly upon two factors, which are inherited independently, namely, the milk-yield and the proportion of butter-fat it contains. Consequently a statement of butter-yield conveys no accurate information either as to the yield of milk or as to its quality ; and, as a guide in breeding, this method is bound to be elusive and uncertain, since the breeder is not clear as to whether his cows are yielding milk in quantity or in quality. If the branches of a bank report to headquarters the value each has in hand in precious metal, the officials at headquarters will easily add up and find the total sum, but they will have difficulty in determining how much is gold and how much is silver. It was also found both in the States and in Canada, but especially at colleges and experimental-station farms, that stock-breeders are much influenced by the wedge-shaped shoulder idea: the cause lying to some extent, perhaps, in their system of judging stock by scoring card. So strong is this influence that sons of a narrow-shouldered, low-yielding cow are frequently preferred as stock-bulls to sons of a higher-yielding cow whose shoulder is broad. The American visit having brought the problem no nearer solution, it was next arranged through the Department of Agriculture and Technical Instruction to have a set of forms on which were printed questions as to the yields in herds of cows, and as to the cows’ parentage. ‘These forms were sent to breeders in the United Kingdom who were known to have kept records, and who might be in a position to give information. A number were kind enough to fill up the forms, and among them were found some whose herds were large enough and whose records were old enough to supply data suitable for the purpose in hand. The answers showed, however, that a considerable amount of preliminary investigation was necessary before the data could be made use of. Breeders had been asked to give the records of each cow for as many years as possible and to state the cows’ ages against their records for each year. ‘hey were also asked to state over against each record the length of the lactation concerned. From the answers to these questions it was seen that in order to compare each cow with the others, it ia cs S Manion Giessen. + 3 23 September. 28 — = 4 24 October. — 23 — 5 3 October. — 26 — 6 3 October. = 7 wr 7 3 November. — 21 = 8 3 April. — = 22 9 3 June. — 25 — 10 3 November. _— -- 15 11 3 November. 30 = as 12 3 December. 35 — = 13 3 September. — 24 = 14 23 September. 29 — — 15 24 October. — — 16 16 3 August. — 21 —_ 17 3 September. — 22 = 18 3 September. — 23 = 19 3 September. — 24 = 20 24 June. — 24 = 21 23 September. — 23 = 22 25 October. — 22 — 23 35 October. — 23 ete 24 25 August. 32 = — 25 24 September. — 23 = 26 ay September. — 24 = 27 25 September. — 25 — 28 oF August. = 26 = 29 3y August. — 29 = 30 3 September. 33 = — 31 3 September. — 27 — 32 3 October. — — 18 33 3 November. — 25 — 34 23 October. — 22 — This bull has daughters of all three grades, and is therefore middle grade, 110 Scientific Proceedings, Royal Dublin Society. SIRE D’s DAUGHTERS. Daily yields in lbs. Number. Age. Date of Calving. High Grade. | Middle Grade.| Low Grade. 1 23 August. = = 10 2 3h September. = = 20 3 3 September. = 26 ats 4 3 September. — 25 ae 5 2h September. — = 17 6 23 September. 30 — = u 33 May. —_— 264 = 8 3 September. _ 25 = 9 8 September. = = 17 10 3 September. — 21 = 11 3 September. — = 152 12 3 October. = a 16 13 3 September. _— 223 = = 14 3 November. — 25 = 16 3 January. — 273 ss 16 3 June. ~ . BO — ae 17 23 September —_ 22% = 18 3 October. | = — 14 19 23 January. — 20 _— 20 23 November. 36 — — 21 3 November. — 214 22 3h May. 355 = = This bull has three grades of daughters and is medium class. There were in the herd daughters of this bull older than three years, and they belonged to the three classes, 7 Witson—The Inheritance of Milk- Yield in Cattle. 111 Sire B’s Daucurers. Daily yields in lbs. Number. Age. Date of Calving. ra Sa | High Grade. | Medium Grade.| Low Grade. 1 ay | August. = 20 — 2 3 August. = = | 19 3 24 ‘A ugust. — — | 18 4 2} September. -- — 16 5 3 April. us DeNty i awen epee 6 3 May. = 26 — | 7 3 May. = 26 — 8 3 May. = 26 — 9 3 August. = 22 — 10 24 August. = 22 — 11 3 August. = _ 19 12 3 August. = 215 = 13 25 September. = —_— 18 14 23 September. = 264 = 15 24 September. = 21 — 16 23 November. = 25 — 17 3 November. 293 — = 18 23 August. —_— — 183 19 3 August. = 26 | = 20 35 August. 345 — = 21 ~25 June. = 245 = 22 pe July. 354 = — K has three grades of daughters, and is therefore himself middle-grade. 112 Scientific Proceedings, Royal Dublin Society. It ought to be mentioned that data similar to those found in the Danish herd-books have been found in the dairy herds belonging to Mr. L. A. Beamish, Ashgrove, Queenstown; Mr. John Evens, Burton, Lincoln; Messrs Hobbs & Sons, Kelmscott, Oxfordshire; and Mr. George Taylor, Cranford, Middlesex. Mr. Beamish’s herd is a small one, consequently his numbers were small; and the three English breeders, like the Danes, have not been in the habit of retaining any poor-milking heifers that may have turned up in their herds till they made four or five records. Thus, since the figures got from these herds were merely a confirmation of the Danish ones, and, since their numbers as a whole were not essentially greater, it has not been thought necessary to publish them. A few remarks by way of caution are necessary. 1. The whole of the foregoing data have been gathered from full-sized cattle: red Danish, shorthorns and shorthorn crosses. It may be that there are breeds in which there are fewer or even more general grades; but this is unlikely among British breeds, as all have had a very similar admixture by way of ancestry to those from which the data have been derived. 2. It is very probable that size plays a part in determining the yields of different grades. On this, however, we have had no evidence. 3. Although it has been possible to separate full sized cows into three general grades, it is possible, and even probable, that there are sub-grades within each, just as the red-and-white colour in cattle is a sub-grade of red, and just as among white cattle, there are pure whites, whites with red ears, and whites with black ears. 4, While examining many thousands of dairy cattle during the last five or six years, the question of external signs of yield was not considered definitely because it was assumed from the first that the usual signs relied upon are not reliable. But three things in the main have impressed themselves as being common to all good milking cows, viz.: a large and roomy udder, an excellent digestive capacity, and an absence of “ patchiness,”’ that is of accumulations of fat at the point of the hooks and elsewhere. - 5. There are considerable variations in cows’ yields, depending upon the way in which they are fed and cared for. A cow which may give 1000 gallons in one man’s hands may drop to 700 or 800 in another’s, and may rise even to 1100 in still another man’s hands. ‘his fact has to be reckoned with in estimating yields. It need scarcely be pointed out that the writer of this paper realizes to the full that we are only beginning to understand how little we know about the cow and her yield, and how vast is the field of work yet before us. ‘The Witson— The Inheritance of Milk-Vield in Cattle. 113 work represented by this paper can only be regarded as, in some degree, clearing the ground for the future. In addition to the gentlemen mentioned in the body of the paper, there are many others to whom the writer is indebted for kindness and information. It is impossible to name them all, but he would wish to name specially Mr. Mansholt, of the Dutch Department of Agriculture; Dr. J. G. Rutherford, at Ottawa, and his assistants; Professor Wentworth, of the Iowa State College, Ames; Professor G. P. Grout, of the Minnesota experiment station, St. Paul; Governor Hoard, Fort Atkinson, Wisconsin ; Mr. Robert Hobbs, Jr., Kelmscott ; Mr. Howie, Secretary to the Ayrshire Milk Records Associa- tion; and the following Ayrshire breeders: Mr. Adam Montgomerie, Mr. Michael Logan, Mr. Thomas Clements, Mr. J. Moffat, Mr. W. H. Ralston, Mr. H. W. B. Crawford, and Mr. James Dunlop. Nove :—Throughout this paper yields lave been expressed, according to the usual custom, in gallons rather than in pounds; and where pounds have been recorded in a herd-book or by a breeder, the figures have been divided by ten. his involves a sight inaccuracy. It raises British yields by about a thirty-third and depresses Danish by about an eleventh. SCIVNT, PROC. R.D.S., VOL. XIIM., NO. VIT. S ae, oe a Man es Peers SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1. A Seed-Bearing Irish Pteridosperm, Crossotheca HAoninghausi, Kidston (Lyginodendron oldhamiwm, Williamson). By T. Jounson, p.sc., F.L.s. (Plates I-III.) (March, 1911.) 1s. bo Considerations and Experiments on the supposed Infection of the }Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers By Georen H ! Peruysrier, B.sd., PH.D. (March, 1911.) 1s. 3. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Writ1am Brown, B.so. (April 15, 1911), 1s.° 4, A Thermo-Hlectric Method of Cryoscopy. By Henry H. Drxon, sc.p., F.R.s. (April 20, 1911). 1s. 5, A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Witu1am J. Lyons, 8.A., a.R.c.sc. (LonD). (May 16, 1911). 6d. 6. Radiant Matter. By Joun Jony, sc.p., r.n.s. (June 9, 1911.) 1s. 7. The Inheritance of Milk-Yield in Cattle. By James Wuxson, m.a., B.SC. (June 12, 1911.) 1s. DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 8. JUNE, 1911. IS ARCHAZOPTERIS A PTERIDOSPERM ? BY T. JOHNSON, D.Sc., F.L.S., PROFESSOR OF BOTANY IN THE ROYAL COLLEGE OF SOIENCE FOR IRELAND. (PLATES IV.-VI.) | Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. —_—— WILLIAMS AND NORGATE, Hi gbv" 14, HENRIETTA STREET, COVENT GARDEN, LONDON, we 1911. Price One Shilling and Sixpence. Roval Wublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749 EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 pom. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least'ten Jay prior to each Meeting, as no Paper can be set} down for reading until examined and ‘approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. Wirson— The Inherrtance of Milk-Vield in Cattle. 1138 work represented by this paper cau only be regarded as, in some degree, clearing the ground for the future. In addition to the gentlemen mentioned in the body of the paper, there are many others to whom the writer is indebted for kindness and information. It is impossible to name them all, but he would wish to name specially Mr. Mansholt, of the Dutch Department of Agriculture; Dr. J. G. Rutherford, at Ottawa, and his assistants; Professor Wentworth, of the Iowa State - College, Ames; Professor G. P. Grout, of the Minnesota experiment station, St. Panl ; Governor Hoard, Fort Atkinson, Wisconsin ; Mr. Robert Hobbs, Jr., Kelmscott ; Mr. Howie, Secretary to the Ayrshire Milk Records Associa- tion; and the following Ayrshire breeders: Mr. Adam Montgomerie, Mr. Michael Logan, Mr. 'homas Clements, Mr. J. Moffat, Mr. W. H. Ralston, Mr. H. W. B. Crawford, and Mr. James Dunlop. Nove :—Throughout this paper yields have been expressed, according to the usual custom, in gallons rather than in pounds; and where pounds have been recorded in a herd-book or by a breeder, the figures have been divided by ten. ‘This involves a slight inaccuracy. It raises British yields by about a thirty-third and depresses Danish by about an eleventh. SCIENT. PROC. R.D.S., VOL. XIII., NO. VII. 3 i 1i4 | WDM. IS ARCH ANOPTERIS A PTHERIDOSPERM ? By T. JOHNSON, D.8c., F.L.S8., Professor of Botany in the Royal College of Science for Ireland. PLATES IV.-VI. [Read, Marcu 28. Ordered for Publication, Apriu 11. Published June 28, 1911. ] In 1852 Edward Forbes (1) communicated to the British Association meeting at Belfast a short note on the discovery in 1851 by officers of the Geological Survey of Ireland of a deposit of well-preserved fossil plants in the yellow sandstone at Knocktopher Hill, Co. Kilkenny. The plauts were accompanied by such fresh-water animals as Anodon Jukesii (a mussel), Holoptychius (a fish), and Pterygotus (a crustacean). They were the most perfect illustrations discovered up to that time of the land-flora of the Devonian epoch, and were regarded as the remains of plants growing in swampy ground or in brackish estuarine water. One of the plants was named by Forbes Cyclopteris hibernica, but was not described in any detail. It was regarded as a fern of the Neuropteris type. It is clear, despite the brevity of his communication, that the value of the find was fully appreciated by Forbes, whose premature death prevented the execution of the design Hugh Miller mentions Forbes had, of preparing a monograph of this Devonian flora. In 1858 W. H. Baily (2) communicated a note to the British Association on these deposits, and described fertile specimens of Cyclopteris hibernica, first found by H. I’. Humphreys, of Blackrock, Co. Dublin, In the meantime, in 1856, a set of the Kilkenny fossil plants, accompanied by drawings made by Dr. Samuel Haughton, had been sent by Sir R. Griffith, the Director of the Geological Survey, to A. Brongniart, whose views were communicated to the Geological Society of Dublin, and to the Royal Dublin Society! in 1857. M. Brongniart expressed great interest in the collection, and asked for amore complete supply of some of the forms before committing himself to a definite expression of opinion as to their age. Griffith, Haughton, and 1M. Brongniart’s original letter was communicated to the Geological Society of Dublin, and a translation of it to the Royal Dublin Society (Journal Roy. Dublin Soc., Vol. I., 1857). Jounson—Is Archeopteris a Pteridosperm ? 115 others regarded the deposit as Lower Carboniferous, Forbes as Devonian. Brongniart found the specimens sent not sufficiently distinctive to enable him to decide between the two views. No one now objects to the view, based on accumulated evidence, that the deposits are Upper Devonian. ‘The specimens sent (numbered 11, 12, 6, 9, 2), gave Brongniart, he wrote, a better idea of the character of Cyclopteris hibernica, which he had thought, from a previously sent specimen, might be an Odontopteris. The venation, he states, is Cyclopteris-like, but the form and arrangement of the pinnules and their flabelliform venation Sphenopteris-like, and especially suggestive of his Adiantites section’ of it, in which the pinnules are entire or only slightly lobed. Brongniart does not know any species really near it, and thinks it ought to be described as a new genus. It needs, he adds, further investigation, is unlike any Carboniferous plant known to him, and in habit approaches Sphenopteris lobata, of the Permian, though the pinnules of this species are deeply divided. In specimens 12 and 9 Brongniart calls attention, as a rarity in ferns, he says, to the now well-known pinnules directly inserted on the rachis. In 1859 H. R. Goppert (7) published an account, based on Irish specimens in the Museums of Berlin and Breslau, of Cyclopteris hibernica, Forbes. Goppert claims for his excellent illustration of C. hibernica, that it was more complete than any that had hitherto appeared. He makes the interesting and justifiable criticism that the only figure he has seen (erroneously assigned by him to Forbes), that in Murchison’s “ Siluria,” is much more suggestive of his two species—C. Halliuna of N. America, and C. Roemeriana— than of C. hibernica, judging from the Irish specimens of this species before him. C. Halliana, Gopp. was discovered in 1843 in the Upper Devonian beds in the State of New York, and C. Roemeriana, Gopp. in 1855 by Roemer, in similar beds at Moresnet near Aachen (Aix-la-Chapelle). It may be mentioned here that the figure in Murchison’s “Siluria” of Archwopteris hibernica is almost identical with Dawson’s figure of his A. Gaspiensis. I can see no difference except in size, the pinna in the A. Gaspiensis illustration being twice the size of that in Murchison’s work. Goppert’s Cyclopteris MeCoyana (op. cit., fig. 2a and b, 'l'af. 38), founded on a fragment, is in reality C. hibernica, with a slight modification of pinuule, and is therefore of no systematic value. Goppert notes the presence on the underside of the slab of the Irish 1 Brongniart included all Paleozoic ‘‘ferns’? in one comprehensive genus Filicites, with subdivisions such as Cyclopteris, Sphenopteris, indicative of the kind of venation presented by the forms included in them. He expressly stated that the terms were provisional, and must give way as reproductive organs were discovered, $s 116 Scientific Proceedings, Royal Dublin Society. specimen in Breslau of a pinnule of a species’ different, he says, from C. hibernica. In 1861 W. H. Baily (3) gave a further account of the Kilkenny deposits, and figured for the first time the fertile portion of the ‘‘ detached fronds of one of the most ancient tree-ferns, Adiantites Hibernicus.” Baily’s figures do not show clearly the overlapping of the pinnules, one of which (op. cit., fig. 1b) is shown with a distinct stalk and a non-decurrent base of attachment, suggestive of ©. Roemeriana. No more specimens appear to have been sent to Brongniart, and despite the discovery of the fertile fronds, quite different from those of Adiantum, the new genus suggested as probably necessary by Brongniart was not founded until 1869, when Schimper (10) gave it the name of Palzeopteris. Schimper’s illustrated account of Paleopteris hibernica (Forbes, sp.) is based on specimens sent by the Geological Survey of Ireland to the Museum in Strasburg. His description and illustrations have since been frequently, in whole orin part, utilized in illustrations of Archzopteris. Schimper’s diagnosis is evidently influenced by the impression that the plant may be one of the Hymenophyllacere. In the diagnosis of the genus he says ‘sori claviformes, bivalves(?)” and in that of Archeopteris hibernica (op. cit., p. 476) “ soris >is the expression used. Sphenopteris laxa, (sporangiis ?) clavatis, costulatis ’ Hall, and Noeygerathia obtusa, Lesqx. are included in the synonyms. ‘lhe representation of the fertile pinnule is unsatisfactory, since the sporangia are shown, erroneously, as arranged in racemose tufts.? Carruthers (11), writing in 1872, argues strongly in favour of the Hymenophyllaceous affinities of Archeeopteris, illustrating his remarks by a figure of a sorus with a bivalve indusium. Carruthers sees on the slabs suggestions of creeping rhizomes, possibly connected with Archaopteris fronds, and was the first to observe that the ovate-oblong ‘sori’ are generally single and not clustered as Schimper shows them. Both err, however, in describing the fertile pinnule as reduced to a midrib, which they admit is not observable in the sterile pinnule. Dawson’s illustrated account (12) of the Fossil Plants of the Devonian and Upper Silurian Formations of Canada was published in 1871. In addition to recording several species allied to the Kilkenny plant, he changed the 1 This specimen, I learn from local inquiry, has been misplaced during the transference of the geological collections to new buildings in Breslau. 2 Stur (7b) gives a list of some eleven species of Archeopteris, and includes A. hibernica, strange to say, with some hesitation. He has not, he mentions, seen a good sample of it, and thinks the published description of the fertile pinnules tends to exclude it from the genus. As the figures in this paper show, the fertile portion of 4. hibernica is normal and characteristic of the genus, Jounson—Ts Archeopteris u Pteridosperm ? 117 generic name from Paleopteris (already preoccupied by Geinitz for a supposed tree-fern) to Archeopteris. Dawson recorded three species as true Archzeopteris—A. Halliana Gipp., A. Jacksoni, Dwn., A. Rogersi, Dwn. The illustrations of these three species are very incomplete (isolated pinnules only, in the case of two of them) and no fertile pinnules are shown or mentioned. There is, however, a figure of a Sphenopteris Hitchcockiana, Dwn. (op. cit., Pl. 15, fig. 175), which Dawson thinks may be the fertile state of A. Jacksoni. In 1882 Sir J. W. Dawson (14) published a further account of these beds under the title ‘‘ The Fossil Plants of the Hrian (Devonian) and Upper Silurian Formations of Canada, Part 2.°! In this report he gives an amended diagnosis of Archgopteris, and excludes from it such sterile species as Oyclopteris obtusa, Lesqx. and Cyclopteris (Platyphyllum) Browniti, Dwn. Archeopteris Jacksoni, Dwn., is further described, and its fertile pinne are illustrated. A new species,.A. Gaspiensis, Dwn., is made known, and illustrations of the sterile and fertile pinne are given. Its fertile pinne, as shown in Dawson’s figure, are not distinguishable from those of A. hibernica or of other species, while its sterile state, especially that shown in his fic. 14, Pl. 23, suggests A. Roemeriana in its small, non-overlapping, stalked pinnules. * Dawson states that 4. Gaspiensis and A. Jacksoni are so near each other that it is not easy to distinguish them except when the fructification is preserved. Judging from the figures, these are useless for establishing specific distinctions, and on the whole they suggest that A. Glaspiensis and A. Jacksoni ave very near to, if not identical with, 4. Roemeriana, Gopp. Although it is thus difficult to decide from the descriptions, on the exact limits of the various species, one most interesting fact was established as early as 1871, viz., that Archeopteris flourished along the banks of estuaries and in marshy ground in the Upper Devonian epoch on both sides of the Atlantic, viz., in Ireland, Scotland, and other parts of Western Europe on the one side, and in the United States and Canada on the other. Renault’s illustrated account (1883) of Archeopteris (15) shows that he also regarded it as Hymenophyllaceous (e.g., ‘‘ Sores claviformes bivalves’). In 1888 R. Kidston (16) published the results of his examination of the Dublin specimens of A. hibernica. He showed that the frond was stipulate, and decided that the sporangia had no keel as stated by Schimper, and no Hymenophyllaceous features, but that they were exannulate and Marattia- ceous. He concluded (at the time), ‘There does not remain the slightest ! Members of the Society will be interested to know that Dr. A. If. Foord, v.c.s., the Editor and Librarian of the Society, is specially thanked in this publication by Sir J. W. Dawson for the help he received from him in the collection of the Canadian specimens of Archzopteris. 118 Scientifie Proceedings, Royal Dublin Society. doubt in my mind that the true position of A. /Azbernica is in the Marat- tiaceee.” In 1894 Schmalhausen (18) described two new fertile species’ of Archeopteris from the Upper Devonian deposits of Donetz-Becken in South Russia—A. archetypus and A. fissilis. One species, A. archetypus, occurs in the lower strata in this fossil locality. Its nearest affinities are stated to be A. Gaspiensis, Dawson, and A. hibernica, Forbes sp. Its pinnules are described as spirally arranged—a remark which is applied to the fertile pinnules too. One or two of the figures seem to support the view of the spiral arrangement, but in specimens of the same species subsequently described by Nathorst (19) from Ellesmere Land, as well as in Schmalhausen’s own type specimens, the spiral character is not observable by Nathorst. I have seen in specimens of A. hibernica fertile pinne in which the pinnules appear arranged just as in Schmalhausen’s figure of A. archetypus (op. cit., Taf. 2, fig. 19), and I am satisfied there is no spiral arrangement of the pinnulesin A. hibernica. ‘The ordinary pinne and pinnules in A. hibernica are readily recognizable as two-ranked or distichous ; and if the fertile pinnules are not always visible their whole length in the stone, their points of insertion are so, generally, and they show that the pinnules are not spirally or radially arranged. Involved in the interpretation of the mode of arrangement of the pinnules is the question of the morphological nature of the various structures. If the frond of A. archetypus, whether sterile or fertile, presented a spiral arrangement of its parts, it would differ in this respect from every living or extinct fern or fern-like frond, and would thus show itself more stem-like and more primitive (?) than any other known frond. Further, it would be necessary to raise A. archetypus to generic rank, and to separate it from the two species A. hibernica and A, Gaspiensis, from which, except for its alleged spirality, it would be other- wise scarcely distinguishable. Its pinnules are described as more wedge- shaped below and rounded above than those of A. hibernica, being more like those of A. Gaspiensis. (The variety of form of the pinnule observable in true A. hibernica specimens makes me attach less systematic value to the form of the pinnules.) Some pinnules are described as the same size as those of A. Roemeriana ; others are as large as those of A. obtusa (C. obtusa, Lesqx.), and others of average size, like those of A. Hibernica and A. Gaspiensis. 1 T have not yet been able to see the evidence on which Dr. White bases the following statement :— ‘“* Areheopteris obtusa and Archeopteris sphenophyllifolia of Pennsylvania and New York are A. archetypus and A. fissilis of Ellesmere Land, Spitzbergen, and the Don.”’ D. White: The Upper Paleozoic floras, their Succession and Range, p. 142, in Willis and Salisbury’s ‘‘ Outlines of Geologic History, with special reference to North America.’”’—Chicago, 1910. Jounson—Is Archwopteris a Pteridosperm ? iS) Like the American and Canadian, the Russian specimens suffer from lack of adequate illustration. Curiously enough, Schmalhausen states that when better illustrations of the species of Archzeopteris already described are available, and when earlier deposits come to be revealed, the spiral arrange- ment, he thinks, will be found to be not confined to A. archetypus. Schmalhausen lays some stress on the greater extent of preservation of the lamina, especially at the distal end, in the fertile pinnule of A. archetypus, by contrast with all other species of Archzopteris described. To this I shall return in the description of A. hibernica. In the second species of Arche- opteris—A. fissi/is—the bipinnate frond in which the pinne are distichously arranged shows pinnules dichotomously divided into four or eight filiform vascular processes, leaving very little undivided basal lamina. The fertile pinne show the usual arrangement of fusiform or club-shaped sporangia arranged on the upper side of the filamentous pinnule. The sporangia are shown, however, not arranged singly like the teeth of a comb, but two, three, or more together on a common stalk. Mach pinnule bears eight sporangia on its upper side, while the number in A. archetypus may be as high as forty. Allowing for the finely-divided state of the pinnule, the venation is on the same plan in A. fissilis as in A. archetypus and other species of Archzopteris. Both A. archetypus and A. fissilis have since been recorded from Ellesmere Land (78° N. Lat.) by Nathorst (19), by whom they are also fully illustrated. Indeed there is nothing more interesting in connection with Archeopteris than the discovery of its contemporaneity in similar estuarine deposits in such different regions as Southern Ireland, Central Europe, Bear Island (74° N.), Ellesmere Land (78° N.), and the eastern part of North America, in both Canadian and American territory. Heer was the first in 1870 to record its occurrence (22) in Bear Island, where fragments of A. Roemeriana, Gopp. were obtained. Nathorst, however, gave the most complete account of the Bear Island deposits in 1902, noting A. intermedia, Nath., A. fimbriata, Nath., and A. Roemeriana, Gopp., the last two in a fertile state, All, too, are well illustrated by him, as in the case of the two Hllesmere Land species. Schmalhausen compares his A. fissidis with Sphenopteris petiolata, Gopp. from the Cyperidines-strata near Saalfeld, now known to be Upper Devonian, and contemporaneous with the South Russian and Kilkenny deposits. The two plants, he notes, show the greatest similarity to one another, and differ in detail only in their vegetative organs. The comparison is interesting, since Brongniart, writing to Griffith in 1857, refers to Unger’s Saalfeld discoveries (23) as likely to throw light on the Kilkenny fossils. Schmalhausen sees also some likeness in A. fissilis to Sphenopteris 120 Scientific Proceedings, Royal Dublin Society. condrusorum, Gilkinet, from the Upper Devonian of Belgium. Stur’s genus Rhodea, from the Culm flora, also shows some points in common with A. fissilis, he finds. Potonié states (21) that in the Sphenophyllacese there is a direct relation between the size and degree of segmentation of the leaf and the age of the species. The earliest known species of Sphenophyllum is S. fenerrimeum, and its leaves are formed of repeatedly forked, filiform processes. The most recent Sphenophyllum —S. Thoni—has undivided leaves, the largest of any species. If Potonié’s generalization were applicable to Archzeopteris, then A. fissilis Schml. would be the oldest species of the genus. In 1903 the discovery of the seeds of Lyginodendion olithamium and the definite establishment of the Pteridospermez,! followed by the discovery of seeds in Neuropteris, Pecopteris, Aneimites, &c., led to a great and sudden change in the interpretation of the Paleozoic flora. The replacement of the view that the leptosporangiate ferns were the more primitive, and gave rise to the Husporangiate, by the view that the Husporangiate ferns, flourishing in the Paleozoic epoch, were the earlier, and subsequently gave rise to the Leptosporangiate, is now in part, replaced by the opinion that the assumed Marattiacee and Ophioglossacez of the Paleozoic were in reality Pteridosperms, and that it is only the imperfection of the geological record, or our lack of knowledge of the evidence buried in the rocks, which prevents this view from being generally demonstrated. Doubts naturally arise in the mind of one who has passed through these various phases of a somewhat revolutionary character (in keeping, it must be stated, with the revolutionary discoveries) as to the reliability of the present view expressed by some palobotanists, that the less highly organized spore-bearing ferns appeared later in time than the seed-bearing Pteridosperms, and that while the Pteridosperms are well represented in the Lower Carboniferous, and possibly in the Devonian, the fern-groups of to-day are uurepresented, though annulate and exannulate sporangia, as well as members of the Botryopteridea, are met with in the Lower Carboniferous. So all-embracing is the view of the early predominance of the Pteridosperms, that the Upper Devonian plant, Archeopteris, is now by many paleobotanists designated as a male Pteridosperm . In 1905 I arranged to make further explorations of the Kiltorean beds in Co. Kilkenny, one object being to test the validity of the view of the Pteridosperm character of Archewopteris. It is only recently that I have been free to give time to examine the specimens of Archwopteris under my 10. Horich, writing in Potonié’s Abbild u. Beschr. d. fossil. PHanzen (IV., p. 44 et seq., 1906) thinks the evidence in fayour of the establishment of the Pteridospermee inailequate—a view that few will share. Jounson—Is Archceopteris a Pteridosperm ? 121 care in the Botanical Division of the National Museum in Dublin, as well as those in the collection of the Geological Survey of Ireland, and a small collection preserved in the Geological Division of the Royal College of Science, Dublin, made a few years ago in the course of an exploration of the Kiltorcan beds by Professors Carpenter and Swain in search of fossil Isopods. I have not, as yet, been able to visit the fossil locality. It will be convenient if I first of all give an account of my examination of the Dublin specimens of Archeopteris hibernica, calling attention to any new features described :— 1. Frond (Pl. 1V.).—The frond, the only part of the plant known, is either wholly vegetative, or partly vegetative and partly fertile. It is bipinnate and, broadly ovate-lanceolate in shape, and of great size. A specimen, 5 feet long, was seen by Baily in the rock at Kiltorcan. The largest one on exhibition in the National Museum, Dublin, is nearly 3 feet long. 2. Rachis (Pl. V., fig. 1).—The base of the rachis is expanded, 1-8 inches wide and 3 inches long in its stipulate parts, somewhat concave on its adaxial side, with some five ridges and alternating furrows. It is, in the Umbelliferous sense, a sheathing base ; but inasmuch as its wings may be slightly free at their distal end, it is better, perhaps, to speak of the base as stipulate, and of the stipules as adnate, as in Rosa. Lach stipule is vascular. Kidston was the first to describe the basal wings as stipules. Baily in his amended and latest reference to Archwopteris hibernica, in his “ Figures of Characteristic British Fossils” (published in 1875), speaks of and figures the “scaly base of the frond.” Between the lowest pair of pinne and the stipules the rachis is not naked, but clothed with lateral vascular outgrowths, which are not scales or ramenta but vascular pinnules, reduced more or less. They are not spirally but distichously arranged. In one specimen I have counted eight pairs of them, and yet in another they are scarcely observable. They are sometimes exposed in the rock edgewise, and are rarely seen as clearly as in fig. 1, Plate V. The stipules and these paired appendages are all of the same texture, and, if it were allowable, it might be more indicative of their relationship to one another to speak of the basal expansions on either side of the rachis, below the lowest pair of pinna, as a whole, as “ interrupted” stipules. The bearing of this mode of designation will be more obvious later. The rachis proper is well developed; and, judging from some of the impressions, was convex on its under and slightly concave on its upper side. There is clear indication of a longitudinal striation with slightly raised ridges and furrows. In addition to this, there is a transverse or horizontal striation, which is distinct from any such puckering, blistering, or other surface-markings as might be due to the mode of preservation in the fine sandstone. The rachis was apparently traversed lengthwise by numerous vascular bundles SOIENT. PROG. R.D.S., VOL. XUI., NO. VIII. T 122 Scientific Proceedings, Royal Dublin Society. (there are signs of five or six at the base), and also strengthened by a frame- work of sclerotic plates or bands, running both vertically and horizontally. (Unfortunately, there are no petrified specimens of A. /ibernica known by which the internal structure can be ascertained.) Hvery specimen I have seen shows the rectangular reticulate striation, and it seems too deep-seated to be artificial. The presence of a cortical framework seems necessitated by the size of the frond, and the apparently small development of vascular tissue in the rachis. ‘Though the primary rachis has not, so far, been found bifurcated, I have seen several cases in which the secondary rachis (i.e. the rachis of the pinne) shows dichotomy—a feature common to so many Palzozoic plants, but not hitherto observed in Archopteris, except by - Nathorst in A. fissidis, where some doubt is expressed by him as to its actual occurrence. ‘These cases in A. hibernica are so clear and relatively frequent that dichotomy of the main rachis merely awaits discovery, I think. It is on account of unobserved dichotomy in the frond of Archeopteris that Seward would exclude from it A. Uschermaki and A. Dawsoni, described by Stur from the Culm of Altendorf. If the identification of the fertile specimen from Kiltorean as A. 7'schermaki, Stur is correct, then any doubt as to dichotomy in Archzeopteris 1s removed, as Stur describes and figures dichotomy in this species. 3. Pinne.—The pinne are two-ranked and generally opposite, though alter- nation occurs in some specimens. Hach pinna is occasionally placed at right angles to the rachis, but usually forms a wide acute angle of 70°-80° with it, and carries on its own (secondary) rachis ten to twelve pairs of imbricate pinnules. ‘The pinne are attached to the primary rachis at intervals of 4 em.,and touch one another above and below by the edges of their pinnules. The pinna is elongated and oblong in outline, and may be 30 em. long and nearly 5 em. wide (25 x 4 cm. is an average size). Hach pinnule (2°5 x 1:5 em.) is asymmetrical, oblong-obovate in outline, and attached by a narrow wedge-shaped decurrent base to the secondary rachis. ‘The pinnules are usually imbricate, and not distinctly stalked. ‘Their margin is entire, slightly toothed, or even somewhat lobed. ach pinnule is traversed by numerous sub-parallel veins, which reach the margin 0°5 mm. apart from one another, and may give rise by their projections to a toothed edge. ‘They enter the pinnule from the rachis as three or four distinct bundles, and as they pass to its edge undergo bifurcation or dichotomy several times, thus giving the numerous bundles observable. There isno suggestion of a midrib or median nerve, and the three or four bundles can be seen clearly entering the 1Scient. Proc. Roy. Dub. Soc., 1911, vol xiii, p. 137_ Jounson—T/s Archcopteris a Pteridosperm ? 128 rachis from each pinnule (PI. V., fig. 5). In some cases it looks as if one or more main veins are present; but this is due to the fact that some of the pinnules were in a state of decay, rotting in the water when fossilised, and the bundles of the skeleton of the leaf became crowded together in the process. Neither in the pinnules nor rachis (primary or secondary) is there any sign of amain vein. As already mentioned, M. Brongniart first observed that the primary rachis carries not only the pinnew, but between them, usually opposite one another and occasionally in two pairs, pinnules in all respects comparable, except for position, to the ultimate pinnules of the pinne described. Occasionally I have found such a pinnule replacing a pinna, whether sterile or fertile, and even doing this alternately on either side of the rachis, both towards the base and the apex of the frond. Such inter-pinnate pinnules or rachidial pinnules, as I prefer to name them (called decursive pinne by Potonié, and ‘ Zwischen-Fiedern” by Nathorst), are not confined to Archeopteris, though a constant feature of it. ‘They are of the same nature as the Aphlebiz of Potonié, who regards such structures as ancestral remains, indicative of a state when the rachis was clothed its whole length with a continuous lamina. The Aphlebia in this interpretation would bear the same relation in time to the general frond as the cotyledons and embryonic leaves of a flowering plant to its adult foliage. If really ancestral, they are of distinct taxonomic value. ‘The basal pairs of rachidial pinnules, along with the stipulate base already mentioned, are of interest in this connection. Archeopteris hibernica is not recorded as such outside the British Isles. When Nathorst first found the Archzopteris deposit on the south-east shore of Bear Island in 1898, he recorded as A. hibernica the form, now made known by him, in its sterile state only, as A. intermedia Nath. In its long and more erect pinnes A. intermedia suggests A. Roemeriana, but in its lobed pinnules differs from it, and approaches A. fimbriata Nath., with its still narrower but distinctly laminated laciniate pinnules. Fertile Fronds of Archeopteris hibernica. In general features the fertile frond (Pl. IV.) agrees with the purely vegetative one. Some of its pinne, usually the sub-basal ones, may be formed almost completely of fertile pinnules. Otten, however, the basal and apical pinnules of a fertile pinna are sterile, and the central pinnules only are fertile, and even of these pinnules the apical part of each may be vegetative. ‘Thus the tendency is for the non-apical parts of the central pinne of the frond to become fertile. Sterile pinnules with marginal T2 124 Scientific Proceedings, Royal Dublin Society. sporangia, as first noted by Kidston, are not uncommon. ‘The general impression one gets from the examination of a number of fertile fronds is the absence of a sharp demarcation between the vegetative and reproductive regions. ‘I'he condition is such as one might expect in a primitive type, and is occasionally met with in living Ophioglossacee. The fertile pinnule stands out almost at right angles to the axis of the secondary rachis of its pinna and is 1-2 em. long. It is, though more or less filamentous, not reduced to a midrib or median nerve, as stated. ‘The transformed pinnule is traversed along its whole length by several vascular bundles, which enter from the secondary rachis. ‘These are well seen in its general substance, and also in its slightly expanded process-like vegetative tip, which is often branched (Pls. 1V. and VI.). This fertile pinnule, hitherto known as the sporangiophore, may be called the sporophyllule. It was probably, when alive, green throughout its length, and capable, especially at its free end, of carrying on a little photo-synthesis. It is important not to overlook the presence of this vegetative tip, since Schmalhausen’s separation of the species Archwopteris archetypus is. partly based on the presence of a sterile tip of the lamina in it and its alleged absence in A. hibernica. Nathorst finds little evidence in Ellesmere Land material of the conspicuous sterile tip of A. archetypus, figured by Schmalhausen in his Russian specimens. On the other hand, I have rarely seen a fertile pinnule of A. hibernica in which a sterile, usually branched tip, is not present. Thus the complete restriction of the sporophyllule to a purely reproductive function is a rarity in A. hibernica. '‘Vhe sporophyllule gives rise on its upper surface to a hori- zontal row of six to twenty, more or less fusiform or claviform sporangia 2 or 3mm. in length, each on its own short stalk. The sporangia are only rarely biseriately arranged as Zeiller describes them. It is only occasionally, too, that the sporangium is sessile, or that two or three are borne together on the same stalk. Schimper’s figure shows a general racemose arrangement of the sporangia which is not observable in our Ivish specimens. Confusion has, no doubt, arisen owing to the crowded, crushed character of the fertile pinnules in the slab of rock in some cases. It is when the sporophyllule has a less reduced surface that the sporangia may be seen arranged on it in two rows and spread out like a marginal fringe on either side of it. Though the sporangia are normally borne on the upper or adaxial side of the pinnule, their free ends are often directed downwards, owing to the backward curva- ture of the pinna and pinnule. ‘The sporangia may thus often appear pendulous and hang downwards as really as in the Pteridosperm genus Crossotheca, in which the truly pendulous microsporangia arise on the under- side of their expanded sporophyll-segments. In such an arrangement the Jounson —Is Archceopteris a Pteridosperm ? 125 escape of the contents of the sporangia would be facilitated. ‘The stalk of the sporangium, ie. the sporangiophore proper, is vascular. A single bundle may be seen entering it from the sporophyllule, and passing to the base of the sporangium itself (Text, fig. 1). (I have seen as a rarity a possible indication that the bundle is continued asa ridge along the sporangium surface towards its apex.) In nearly all living Filicines, as well as in other Pteri- dophyta, the sporangium, and its stalk, when present, are non-vascular. The Ophioglossaceze, and less markedly the Osmundaces, are striking exceptions, it may be noted in passing. It seems desirable to use, as I have done, the convenient term sporangio- phore in a non-morphological sense, simply to indicate the stalk, whether vascular or not, carrying the sporangium or synangium, and to leave morphological interpretations to be expressed in each group by other special terms. Thus in the case of Archzeopteris the fertile pinnule or sporophyllule is clearly the homologue of the sterile pinnule. The oblong-oval, fusiform or club-shaped exannulate sporangium sometimes presents a surface which 1s uniform, except for a fine longitudinal striation due to the walls of the cells forming its outer layer. Very rarely there is a distinct more or less median eroove, suggestive of a longitudinal slit and observable as a slit or crack in the carbonaceous impression. More frequently there is a furrow running along the two sides of the sporangium. In many cases the central carbonized matter of the body of the sporangium has disappeared, and is represented in the rock by a vertical row of 3-6 distinct pockets, separated by transverse bars (Pl. V., fig. 4, Pl. VI.). The carbonized body of the sporangium is seen divided transversely into five or six sections by horizontal grooves, which can scarcely be due to artificial splitting caused by shrinkage of the carbonaceous crust. Sometimes the carbonaceous wall shows cross-bars apparently, at similar intervals. Occasionally the surface is tuberculate, as if raised by the contents of the sporangium. As these, in spite of various attempts, have not yet been seen it would be pure conjecture to suggest that sporangia with a warty surface may have contained large spores and the less irregular ones small spores. There is, however, clear evidence that the sporangium is not a simple spore-capsule opening by an apical pore as suggested by one writer. It is, it seems, divided by transverse septa into a multilocular spore-capsule, 126 Scientific Proceedings, Royul Dublin Society. formed of a vertical row of superposed compartments. It may be a synangium of united sporangia, comparable to one-half of a small vascular “sporangiferous spike,” such as that of Ophioglossum (fig. 2). I have made a number of drawings of the surface features of different sporangia, and have also had photographs taken of magnified sporangia. It is desirable to exclude as far as possible the personal equa- ae tion in the interpretation of the structure of the Archeopteris TE sporangium, and to let the evidence speak for itself, in the eG. photographs. It is not easy to dissect out an intact sporangium from the rock; but occasionally it is possible to get a fairly complete one. Such is that in Pl. V., figs. 2 and 3, in which the transverse segmentation is unmistakable. Fig. 3 isa drawing of the same sporangium magnified forty-five times. The speci- men was treated with eau de javelle for several months before Fig. 2.1 being separated out, and was subsequently, when isolated, after being photographed, treated with Schulze’s macerating liquid and ammonia, and again photographed. It became much clearer at one end, and at the other the septation was recognizable by reflected, but not by transmitted light. This septation is too constant, regular and deep-seated to be dismissed as artificial. It is, of course, impossible to say how the assumed partitions arose—i.e., whether the spore- capsule is a synangium, formed of fused sporangia, or a single sporangium made multilocular by the sterili- zation of plates of potential sporogenous tissue. ‘The compartments may open independently by their own transverse pores, or the longitudinal grooves mentioned may be indicators of longitudinal dehiscence. It is thus possible that the locules open in common longitudinally. The partitions are sometimes more or less irregular. This inconstancy in direction in this primitive fossil is uot surprising. ‘There is considerable variety in the direction of the slit of the sporangium in, e.g., Botry- chium. The vascularity of the stalk is a sure sign that the sporangium has a long past, and that it was a body of fundamental physiological importance even in the Devonian epoch. Archzeopteris has been described as a tree-fern, as one of the Hymeno- 1 From Engler’s ‘‘ Die Flanzentamilien.”’ CORRECTION. Foot-note, p. 126. For ‘‘ Flanzenfamilien” read ‘* Pflanzenfamilien ’’. Ch te 2) pert yon val u ie wa oe Naat | a Nit Mee V ans AN Jounson—TIs Archeopteris a Pteridosperm ? 127 phyllacew, as one of the Marattiacess, and quite recently, as mentioned already, it has been assigned by several writers to the Pteridospermen. Assuming that my statements as to its structure are reliable, what bearing have they on its affinities? One is at once struck by the comparability of the septate sporangium to the Ophioglossaceee “sporangiferous spike.” In Ophioglossum vulgatum the usually solitary foliage-leaf bears on its upper side the stalked body, whose free end consists of two rows of sunk sporangia opening by transverse slits. Between the sporangia (fig. 2) the vascular system of the “spike” sends, right and left, a bundle between each two superposed sporangia. Bower regards this composite body or “ sporangiferous spike” as the equivalent of a single sporangium (e.g., that of Lycopodium) which has become septate by the sterilization of potential sporogenous tissue, in which, however, it must not be overlooked, a vascular bundle runs in each septum. My own inclination is to regard Archzopteris not as a male Pteridosperm, but as a representative of the type of plant from which the Ophioglossaces (and possibly the Osmundaceze) sprang, and at the same time, as illustrative of the type from which the Pteridosperms may have arisen. This view has been strengthened by the appearance I am about to describe, presented by the fertile pinne in two different fronds. In one case the piece of the frond preserved shows eight or nine pairs of pinns, nearly all partly fertile. The sporophyllule or fertile pinnule of these pinnae shows the usual characters as described ; but it shows, in addition, from the under side, a sterile, more or less wedge- shaped lobe, which may be itself lobed (PI. V., fig. 4; Text, figs. 4, 5, and 1). Fig. 4. Fig. 5. Thus in the one pinnule we have a sterile lower abaxial! lobe and a fertile upper adaxial lobe. I have seen both lobes sterile and also both lobes fertile, as exceptions. On a small scale we have roughly represented, repeatedly in the one pinna and frond, the normal solitary condition of things in Ophioglossum. It may be urged that this specimen of Archzopteris is abnormal, and that 1The terms Abaxial and Adaxial seem preferable to ‘‘ dorsal ’’ and ‘“ ventral,’’ which are used in one sense by Continental writers, and in the opposite sense by some English writers. Seward uses the terms, no doubt inadvertently, in both senses in ‘‘ Fossil Plants,” vol. ii. 128 Scientific Proceedings, Royal Dublin Society. no conclusions can be drawn from it. It must be remembered, however, that the lobation described is general in this one frond and is observable in another, and that we have scarcely a dozen fertile fronds all-told for examination. The fine frond reproduced in Plate IV. shows many details of structure of distinct interest. Some of these may be mentioned. The sterile tip of the sporophyllule is sometimes, as seen, divided into several digitiform riband-like processes. At one point in Plate IV. the whole sterile pinnule is pinnately segmented into similar processes (Text, figs. 7 and 8). This Vy, We i YE | —— A Fig. 6. Fig. 8. pinnately-lobed pinnule is highly suggestive of several species of Sphenopteris, and seems to indicate that Archeopteris has within it Sphenopteris affinities. There are all stages of transition in these fronds between purely sterile and mainly fertile pinnules (fig. 7). Even the abaxial lobe is occasionally fringed with a few sporangia. In a row of otherwise normal sporangia one is enlarged, flattened, and evidently converted into a sterile segment. Occasionally the abaxial lobe is itself bifurcated (fig. 1). As Archeopteris grew possibly throughout the northern hemisphere in the Upper Devonian epoch, in all likelihood the lobation here noted was not uncommon. Archeopteris is one of the earliest of our known land-plants, in a labile or plastic state. Confine the assimilative and reproductive functions to definite regions, bifureate the frond so that one part is vegetative and the other fertile, and the origin of Botrychium from Archeeopteris is not difficult to trace. Restrict these two functions, reduce and simplify the output of both, and we have the condition of things in Ophioglossum. If the fertile and sterile portions of the composite frond of Rhacopteris Jounson—Is Archeopteris a Pteridosperm ? 129 paniculifera, Stur, from the Culm, were arranged into sterile and fertile lobes, Botrychium would be easily derivable from it, and such differentiation or physiological division of labour is to be expected in an ascending series. As Archzopteris is one of the earliest land-plants known, its structural features may indicate the possible lines of descent of later-formed groups or of affinity with contemporaneous groups derived in common from ancestral forms. It must be generally agreed that land-plants did not begin in the Devonian epoch, though the earlier rocks reveal little that is definite or reliable, of their presence. The lapse of time, during which the more primitive groups waxed and waned and disappeared, or were replaced by forms better adapted to the changing environment, was, it is stated, as great in the Pre-Carboniferous epoch as that since the Carboniferous records began. Considerable time is all the more a necessity if the view that the ‘‘ Ferns” of the earlier part of the Paleozoic epoch were mostly Pteridosperms is substantiated. It must be remembered, too, that during the Upper Devonian and Carboniferous epochs the conditions were most favourable to luxuriance of plant-life. It is generally agreed that the temperature over the Northern Hemisphere at least, extending from Southern Hurope to the Arctic regions (78° N.), was tropical. One authority gives 20°-25°C. as the average temperature. The Hllesmere Land plants (78° N.) are finer and larger than those of Southern Russia of the same epoch, apparently indicating a warmer climate further north. ‘The rain-fall was torrential (greater than any now known, it is stated), and the percentage of carbonic acid in the air was as high as 8. All the conditions were thus at an optimum for vegetative growth. Hence such fronds as those of Archeopteris, 5 feet long, with its thick rachis, are explicable. Under such conditions the pinnations of a frond are of less systematic value. The luxuriant conditions favoured excessive growth, accompanied by multiplication or repetition of the parts, and thus Archeopteris, with its bipinnate frond and numerous sporangia, may be regarded as the equivalent in Upper Devonian time of a plant built up on the same general plan, but represented by fewer vegetative and fertile organs, in less favourable recent temperate times. From this point of view the gap between Archzopteris and Ophioglossum, looked at externally (the only way available in the case of Archzeopteris), is not so great as appears at first sight. Again, the diffuse habit and want of definite demarcation between the vegetative and reproductive regions are signs of a primitive type. ‘The arrangement in Archeopteris meant exposure of a large surface to any adverse local conditions. In the course of time the less elongated, more SCIENT. PROC, R.D.S., VOL, XIII., NO. VIII. U 130 Scientific Proceedings, Royal Dublin Society. compact pinnules would be less injured, and plants possessing them would survive. With the transition of a whorl of two to one of three or more fertile seoments a sort of strobilus suggestive of Sphenophyllum could arise. The frond of Archzopteris is imparipinnate, and this explains the fact which Nathorst notes in the case of A. Roemeriana, that the main rachis of the frond in all species of Archeopteris is occupied at its distal end by pinnules in pairs like the decursive, rachidial, or aphlebioid pinnules. If the leaves of A. fissilis were not opposite, but arranged in whorls of three or six, they would very much resemble those of Sphenophyllum tenerrimum, the earliest of the Sphenophyllums. Again, if the apical pinnules, making the frond of Archeopteris impari- pinnate, were fertile—and there is no reason why this should not have occurred occasionally---the Sphenophyllum condition would be realizable, though in Sphenophyllum the strobilus is formed of an axis with whorled sporophylls; and in Archeeopteris it is the frond only with which the com- parison can be made. The lobed sporophyllule just described materially supports Lignier in his attempts (25) to demonstrate the possibility of the Filicinean origin of the Sphenophyllales. The change from the condition of things in Archeopteris to that of a strobilus, as seen in Sphenophyllum, is hardly more striking than that seen in living Cycadacee (e.g. in Cycas and Zamia). In Cycas the pinuate leaves, spirally arranged, show pinnules con- verted into ovules—a condition (though with intermediate connections) quite different from that in Zamia, where the ovules are arranged in a cone or strobilus on whorled peltate sporophylls. One of the most fascinating features of the study of the fossil plants is the light cast on the line of descent of groups of plants, and on their inter- relationships. In the case of the vascular Cryptogams or Pteridophyta we have to account for the origin of such main groups as the Botryopteridesx, the existing Filicineze (Leptosporangiate and Husporangiate), the extinct Sphenophyllacesx, the Hquisetacez, the Psilotaceze and the Lycopodiales, and also for the extinct Cordaitacez, as well as for the newly-formed group of seed-bearing plants or Pteridosperms. Many attempts have been made to give body to an imagined primitive group of land-plants from which the groups just mentioned might arise in the course of time. The rocks have been eagerly searched—so far in vain— for such an originating type. Several terms for such a group have been suggested. ‘The term should not, by implication, convey the idea of the acceptance by its adoption of the view of a definite source of origin. The topsy-turveydom of the classification of Paleozoic plants, caused by the discovery of the Pteridosperms, should warn one, in the present state of ~ Jounson—Js Archeopteris a Pteridosperm ? 131 knowledge, against the use of a term committing one to a preconceived idea. We need a term which will stand for a group of primitive plants which are no longer purely aquatic, have begun to develop a vascular system, to show differentiation into stem and leaf, and to reproduce themselves by sporangia. Such a term is Archegeophyta; and, as an illustration of one member of this group, I would mention a plant found in the Upper Devonian rocks of Treland, named by Baily “Sphenopteris sp.,” and apparently identical with Sphenopteris Devonica, Unger, or as Nathorst thinks, with his Sphenopteridium Keithawi. ‘Vhe term “ Primofilices” introduced by Arber to indicate the primitive group from which the Filicineze arose, is unobjectionable if con- fined to Ferns. The term now proposed is more comprehensive, as it includes the ancestral forms of the Ferns, and of the other groups mentioned. The need of such a term is illustrated by the concluding paragraph of M. P. Bertrand’s “Etudes sur la fronde des ZLygopteridese et Pterido- spermes,”’ where it is stated that the Zygopteridese and Pteridosperms are not directly connected, but perhaps have their origin in a common stock, i.e. a group of vascular Cryptogams in which the leaf or frond (appendage) had ‘not yet attained to its fundamental feature of symmetry and branching. Lignier adopts and employs in a wider sense Arber’s term Primofilices, in preference to his own of Propsilotacee. Archeopteris seems capable, too, of throwing some light on the possible paths of descent of the Spermophyta from the Pteridophyta. ‘Thus in the Aroideze we have a primitive group of Monocotyledons so low in the scale that it has, as has been said, no method of placentation of the ovule which can be called the fixed, normal method. Hyery possible mode of placenta- tion is represented in the Aroides, as if the various ways were being tried in the different genera. ‘The spadix and spathe have a relationship to one another roughly comparable to that of the ‘‘sporangiferous spike” to the vegetative leaf in Ophioglossum.1 In both groups there are signs of the same physiological division of labour. On the one cylindrical support are borne a protective assimilating sterile expansion and a fertile part, on which the reproductive organs are crowded together. In our specimen of Arche- opteris, and in some Sphenophyllums, the same principle is illustrated in the divided pinnules. In a discussion at Dresden a few years ago on the origin of the Spermophyta, Wettstein, Porsch, and others traced a line of descent of the Dicotyledons as represented by Casuarina from the Gnetacee as 1 Anyone who has observed the leayes of Arum plants, as they break through the soil under the hedgerow in early spring, must haye been struck by the similarity of their appearance to that of the unfolding fronds of an Adder’s Tongue fern in a meadow. Is the resemblance of habit purely superficial, and not indicative of ancestral affinities ? u2 132 Scientific Proceedings, Royal Dublin Society. represented by Ephedra; and Drude, in the course of the discussion, suggested that, as a further step backwards, the condition of things in Equi- setum was worthy of note. No paleontologist took part in the discussion ; but it was interesting to hear affinities suggested between types represented by these genera. In the warm, moist atmosphere, rich in carbonic acid, of the Upper Devonian epoch,’ plants throve, and some produced large, divided leaves, carrying, in not very sharply-defined regions, the reproductive organs. Under less luxuriant conditions, though the same principle of division of labour remained, the bipinnate frond was reduced to a simple or divided lobe, with an attached or fertile lobe, in which the sporangia were crowded. Later, as reproduction became more specialized, the fertile lobe became heterosporous, and branching now occurred in the reproductive instead of in the vegetative organs, giving us flowers of two kinds, each with its own sporangia. The addition, or not, of a perianth to each flower, and the conversion of the spathe into an organ attractive in pollination, would give a further stage in the evolution of the Aroidew. Engler states, though naturally not in this connection, that 92 per cent. of the Aroidea are tropical plants, and that, as they are found growing mostly in moist habitats, where they rapidly decay when dead, it is not surprising that they are little known in the fossil state. Are we now in a better position than formerly to decide as to the affinities of Archeeopteris ? Our discussion is still crippled by the absence of information on its internal anatomy. We have carbonaceous casts or impressions only to aid us, and thus the evidence is incomplete. It will be useful to consider the various characteristics of Archeopteris seriatim :— 1. The “fern-like ” bipinnate frond is found in Pteridosperms as often as in ferns, 2. The dichotomy of the frond and its pinne is common in Pteridosperms and in certain groups of ferns. 3. The aphlebioid pinnules occur in Pteridosperms, and in ferns. 4. The stipules are like those of Angiopteris, but came away with the frond from the parent plant. In the Marattiacee, as Nathorst notes, they remain attached to the leaf-base on the parent plant. Stipules are known in the Cycadew, though Wieland gives very little attention to them in his recent fine work on the Cycadoides. 1 See Chamberlin and Salisbury : Geology, vol. ii, p. 603, where another view of the climate is also given. Jounson—Is Archeopteris a Pteridosperm ? 133 5. The dichotomy of the veins and the absence of a midrib in the pinnules are worthy of note as indicative of a primitive type. The external characters of the vegetative organs, as far as known are, it thus seems, of no taxonomic value in decidiug as to the position of Archeeopteris. Until the discovery of the Pteridosperms such characters were regarded as Filicinean. 6. The fertile frond of Archeopteris, with its partial separation into vegetative and reproductive regions, is comparable to the fertile frond of the Osmundaceee, Ophioglossaceze, and of Aneimia in the Schizeeacez. Nothing like Archeopteris is known in the Pteridosperms at present. It would be dangerous to use this, possibly imperfect and “impressionist ” knowledge, as an argument against the inclusion of Archeopteris in the Pteridosperms. 7. The lobed sporophyllule of Archeopteris is more suggestive of affinities with Sphenophyllum and Ophioglossum than with a Pteridosperm . The sporangium of the great majority of the living Pteridophyta is evascular. In the extant Ophioglossacez and the extinct Botryopteridese, as repre- sented by Zygopteris, the sporangium is vascular, Le., vascular tissue runs through the stalk of the sporangium, and either ends below it, or as in Ophioglossum, runs on and sends off veins between the sporangia. In the vascularity-of the sporangium Arche >pteris is comparable among ferns with the Ophioglossaceee. ‘he microsporangia of a Pteridosperm (e.g. the bilocular sporangia of Crossotheca) are also in a sense vascular, i.e. the sporophyll segment bearing the sporangia is vascular. 8. The sporangium of Archzopteris is apparently divided by transverse septa into a series of superposed loculi comparable to one half of a small * sporangiferous spike” of an Ophioglossum. No Pteridosperm microsporan- gium, so divided horizontally, is known; but in living Angiosperms there are many genera which possess microsporangia or pollen-sacs made multilocular by horizontal partitions. 9. Archeeopteris is now known from widely-separated localities in different parts of the world—lIreland, Scotland, Belgium, Germany, Russia, China (?), Bear Island, Ellesmere Land, Hastern Canada, and Hastern United States. In no locality have seed-like bodies been found, connected directly or indirectly with the plant. On the other hand, the localities have, as a rule, not been exhaustively examined for Archeopteris, and no locality has been investigated since the Pteridosperms, as a seed-bearing group, were founded. 134 Scientifie Proceedings, Royal Dublin Society. 10. Archzopteris occurs in the Upper Devonian and Culm rocks, while the Pteridosperms are known in well-developed forms from the Culm or Lower Carboniferous. The ferns are represented in the Carboniferous by the fossil group of the Botryopteridese, from which most of the different modern groups of ferns can be derived, on paper at least. A generation ago scarcely anyone was found to suggest that Sphenopteris, Neuropteris, Pecop- teris, and other types were anything but ferns. My own inclination is to regard Archeopteris as an ancestral form of the Ophioglossacese, without excluding from view the possibility that further investigation of the beds containing it may show it to bea Pteridosperm, or to have within it the makings of a Pteridosperm. The view that the highly crganized seed- bearing Pteridosperms made their appearance in time before the spore-bearing ferns, surely needs very strong and conclusive evidence before it can meet with general acceptance. BisLioGRAPHY. 1. Forsus, .: On the Fossils of the Yellow Sandstone of the South of Iveland. Brit. Assoc. Rep., London, 1853 (Belfast Meeting, 1852), p. 43. 2. Bainy, W. H.: On the Fructification of Cyclopteris hibernica (Forbes) from the Upper Devonian or Lower Carboniferous Strata at IGltorean Hill, Co. Kalkenny. Brit. Assoc. Rep., London, 1859 (Leeds Meeting 1858), p. 75. 3, —— lixplanation to accompany Sheets 147 and 157 of the Maps of the Geol. Surv. Ireland, 1861, pp. 18-16. nS : Figures of Characteristic British Fossils, London, 1875, Pl. xxviii. 5. Grirritn, R., and Broneniarr, A.: Journ. Geol. Soc., Dublin, vol. vil., 1857, p. 287. 6. —— Journ. Roy. Dublin Soe., vol. i., 1858, p. 313. 7. Gorrurr, H. R.: Ueber die Fossile Flora d. Silur., Devon. u. unteren Kohlen-Formation oder d. sogen. Uebergangsgebirges. Acad. Ces: Leop. Nova Acta, Bd. xxvii., 1860, pp. 426-606. 8. Srur, D.: Die Culm-Flora d. Mahrisch-Schlesischen Dachschiefers.— Abhandl. d.k. k. geol. Reichsanst., Bd. viii, Wien, 1875, s. 57 et seq. Taf, xii., fig. 1, Tat. xvi., fig. 1. i J OHNSON—T/s Archeeop teris a Pteridosperm ? 135 . Murcuison, Sir R. I.: “ Siluria,” 5th ed., London, 1877, p. 255. . Scuimpgr, W. P.: Traité de Paléontologie végétale, vol i., 1869, p. 475; Atlas, pl. 36. 11. Carrutumrs, W.: Notes on some Fossil Plants. Geol. Mag., vol. ix., 1872. 12. Dawson, J. W.: (‘ Archeopteris.”) Fossil Plants of the Devonian and Upper Silurian Formations of Canada [Part I.]. Geol. Surv. Canada, Montreal, 1871. 13. — Notes on New Hrian (Devonian) Plants. Quart. Journ. Geol. Soc., vol. xxxvii., 1881, p. 299. 14. —— Fossil Plants of the Hrian (Devonian) and Upper Silurian For- mations of Canada. Part ii. Geol. Surv. Canada, Montreal, 1882. 15. Renauut, B.: Cours de Botanique fossile, vol. iii., 1883, p. 200, pl. 34, fig. 1-5. 16. Kipsron, R.: On the Structure and affinities of Archwopteris hibernica, Forbes, sp. Ann. Mag. Nat. Hist., Ser. 6, vol. i., 1888, p. 412. 17. —— On the Microsporangia of the Pteridospermex, with remarks on their Relationship to existing Ferns. Phil. rans. Roy. Soc., vol. exevi., 1906, p. 418. 18. ScHMALHAUSEN, J.: Ueber Devon. Pflanzen aus dem Donetz-Becken. Mem. Com. Geol. vol. viii., No. 3, St. Petersburg, 1894. 19. Narvnorst, A. G.: Zur Fossilen Flora der Polarlander. I.—Zur Oberdevon. Flora der Baren-Insel. Kongl. Svenska Vetensk. Akad. Handl. Bd. xxxvi., No. 3, Stockholm, 1901-1902. 20. —— Die Oberdevon. Flora d. Ellesmere-Landes. (Report of the Second Norwegian Arctic Expedition in the ‘Fram,’) No. 1, 1898-1902. Christiania, 1904. 21. Poroniz, H.: Lehrbuch der Pflanzen-Paleontologie, Berlin, 1899, p- 176. 22, Herr, O.: Kohlen Flora d. Baren-Insel. Kong]. Svenska Vetensk. Akad. Handl., Bd. ix., No. 5, Stockholm, 1871. 23. Ricurer, R., und Unesr, F.: Beitrag zur Paleontologie des Thiringer- waldes. (K. k. Akad. d. Wissensch., Denkschr.. Bd. xi., Wien, 1856, p: 87.) 136 Scientific Proceedings, Royal Dublin Society. 24, Lesqurreux, L.: Description of Fossil Plants, in Geology of Pennsylvania, vol. ii., Part 2, 1858, plate 9, fig. 6. 25. Licninr, O.: Hquisétales et Sphenophyllales. Leur origine filicinéenne commune. Bull. Soc. Linn. Normandie, Sér. 5, vol. vii., Caen, 1904, p. 98. 26. —— Sur Vorigine des Sphénophyllées. Bull. Soe. Botan. France, Sér. 4, tom, vill., Paris, 1908, p. 278. 27. Crépin, F.: Description de quelques Plantes fossiles de l’étage des Psammites du Condroz (Dévonien Supérieur). Bull. Acad. Roy. Belg., tom. xxxviii., Bruxelles, 1874, p. 356. 28. Wuitz, D.: Upper Paleozoic Floras, in “ Outlines of Geologic History,” by Willis and Salisbury, Chicago, 1910, p. 142. “AI ALV Id TIIX “IOA “SN “OOS NITENG A OONd NGIOS SCIENT. PROC. R. DUBLIN SOC., N'S., VOL. XIII. PLATE IV | | Pets SE SCIENT. RROG Ro DUBLIN SOC, Nis; VOL. XII: PILES, W/, 5. PILNINS, Wile XIII. SCIENT. PROC. R. DUBLIN SOG., N.S., VOL. SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1. A Seed-Bearimg Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonnson, p.sc., F.L.s. (Plates I-III.) (March, 1911.) 1s. 2. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers By Groner H Prruysriwwce, B.S0., PH.D. (March, 1911.) 1s. 8. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic’?Fields. By Wrt1am Brown, B.so. (April 15, 1911). 1s. 4, A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, sc.p., F.R.s. (April 20,1911). 1s. 5, A Method of Hxact Determination of the*Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrctiam J. Lyons, B.A., a.R.0.sc. (LonD). (May 16,1911). 6d. 6. Radiant Matter. By Joun Jory, so.p., r.x.s. (June 9,1911.) 1s. 7. The Inheritance of Milk-Yield in Cattle. By James Wiunson, ™.A., B.SC. (June 12, 1911.) 1s. 8. Is Archeopteris a Pteridosperm? By T. Jounson, D.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 9. JUNE, 1911. THE OCCURRENCE OF ARCH AOPTERIS TSCHERMAKT, Stur, AND OF OTHER SPECIES OF ARCHAOPTERIS IN IRELAND. BY T. JOHNSON, D.Se., F.L.S., PROFESSOR OF BOTANY IN THE ROYAL COLLEGE OF SCIENCE FOR IRELAND. (PLATES VII., VIII.) [Authors alone are responsib/e for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. JN eonien | WILLIAMS AND NORGATE, [> 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. VM 1 4 ij a | 1911. \ Ne; Price One Shilling. Roval Dublin Society. ea a a a FOUNDED, A.D. 1731. INCORPORATED, 1749 a eOOEeOESOE EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p-m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin — Society at least ten Jay prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. Th copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a ;omplete form, and ready for transmission to the Iiditor. [ ise | IX. THE OCCURRENCE OF ARCH ZOPTERIS TSCHERMAKT, Stur., AND OF OTHER SPECIES OF ARCH AOPTERIS IN IRELAND. By T. JOHNSON, D.Sc., F.L.S., Professor of Botany in the Royal College of Science for Ireland. (Prares VII. & VIII.) [Read, Marcu 28. Ordered for Publication, Apri 11. Published Junz 28, 1911. Archeopteris Tschermaki, Stur. Tue part of the frond preserved is simply pinnate, Rhacopteris-like, 10 cm. long and 2°5 em. broad. The rachis shows along its central part a distinct rectangular reticulum, as if it were divided up by transverse and vertical striae into somewhat ,tubercled minute segments. ‘This sculpturing is con- tinued into the midrib of the pinne. It looks like a blistered, cracked surface; but is apparently a natural feature, comparable to that seen by Nathorst in Archeopteris fimbriata Nath., and that by Heer in Cardiopteris Srondosa, Gopp. Pinna 2:5-4 em. long, sessile, forming an acute angle with the primary rachis; oblong in outline, with a distinct midrib; the lamina with the sub- parallel, dichotomous, or forked venation of the genus Archwopteris; more or less lobed, with slightly toothed edge, each tooth having three bundles ending in it; the lowest pinua more deeply lobed. Sporangia.—At one point towards the apex are two fertile segments or sporophyllules, each with its row of stalked sporangia, like those of A. hibernica. Archeopteris Tschermaki, Stur, suggests a connection of the genus Archzopteris with the genus Rhacopteris, Schimp. of the Culm and Carboni- ferous. Stur regarded the latter genus as a representative in the Culm of the Ophioglossacex, and saw in R. paniculifera, Stur, a now disputed type of the modern Botrychium. SOIENT. PROC. R.D.8., VOL. XIIL,, NO. IX. = 138 Scientific Proceedings, Royal Dublin Society. In Rhacopteris the frond is simply pinnate; and in R. asplenites' (Gutb.) Schimp., the pinna possesses a midrib, and, but for its more laciniate lamina, shows great likeness to the pinna of Archeopteris Tschermaki. Were it not for the sporangia in our specimen, I should have felt compelled to regard the latter f i ZF he GREE z Le fw fuk Kose sTRS SS LU INNA TREES = a gh a AY i =\\ WIS ~-b : a , Fig. 2. I'ic. 1.—Drawing of the portion of the frond preserved of Archeopteris Tschermaki, showing the dichotomous venation of the pinne, the bifurcated rachis at @ and 4, and the fertile segments at s. Fic. 2.—Illustration of a frond of Archeopteris Tschermaki, Stur (after Stur). Reproduced for comparison with Fig. 1. as a Rhacopteris. It is possible that fertile specimens of Rhacopteris may yet be found in the Carboniferous, with fructifications of the Archeopteris type, suggestive of Ophioglossum. 1H. Potonié: Abbild. u. Beschr. foss. Pflanz., Lief. 1. 1903, fig. 1. Jounson— The Occurrence of Archeopteris Tschermaki, Stur. 139 Archeopteris Tschermaki differs from most species of the genus in its dichotomous frond, each half of which is simply pinnate, or basally sub- bipinnate. Formation. Upper Devonian beds, Kiltorean, Ireland. In the same slab, alongside of Archeopteris hibernica, and Bothrodendron kiltorkense, Haughton, sp., which latter overlaps and partly hides it. This fertile Irish specimen is of interest, as it extends the range of Archeopteris Tschermaki, Stur, both in space and time, and shows that Archxopteris extended upwards into the Culm, and, like so many other Paleozoic plants, possessed a bifurcating frond. My drawing of the fertile specimen was made before I had seen Stur’s figure of A. Tschermahki, with which Nathorst suggested comparison. ‘The identity of the two figures is striking, and helps to justify the allocation of the specimen to A. Tschermaki' rather than the creation of a new species of Archzeopteris. Collection.—Botanical Division, National Museum, Dublin. ‘B.D. 10.” Archzopteris hibernica, var. minor, Crépin, and A. Roemeriana, Gopp. Some of the Kiltorcan specimens of Archeopteris show pinnules less imbricate than usual, and not more than half the ordinary size. Crépin noticed in the Brussels Museum in 1874 such a smaller specimen in a slab sent from Kiltorcan twenty years previously, and regarded it as probably identical (‘‘une forme semblable’’) with his A. hibernica, var. minor, found in the Evieux beds in Belgium. His figure shows two pairs of over- lapping unstalked pinnules, with decurrent base of attachment, quite like a Kiltorcan specimen in the Botanical Division of the National Museum, Dublin. Crépin believed that the (Cyclopteris) Archeopteris Roemeriana of Goppert from Aachen (really not far from Evieux, though the two localities are in different countries) was his A. hibernica var. minor, and that the name of A. Roemeriana Gopp., sp., ought to be suppressed. Now A. Roemeriana, Gépp., as originally described, shows two alleged points of difference from A. hibernica. Its pinnules do not overlap, and are much smaller than those of A, hibernica as usually found. There are, too, no inter-pinnate or rachidial pinnules, according to Géppert and Potonié. There are specimens in the Dublin Museum which show such non-imbricate, smaller, stalked pinnules, but they also show distinctly the presence of aphlebioid rachidial pinnules. 1D, Stur: Die Culm-Flora, (s. 57 et seq., Taf. xii., fig. 1, and Taf. xvi., fig. 1). x 2 140 Scientific Proceedings, Royal Dublin Society. As Nathorst himself states, Goppert’s diagnosis is based on a fragment showing three or four pinne only, and more abundant material would have shown him the aphlebioid pinnules. Plate VIII. is a reproduction of a photograph of the specimen just mentioned. It is labelled “ Cyclopteris hibernica, from the Devonian beds of Glanmire, Co. Cork,” though the counterpart slab is labelled ‘« from the Carboniferous limestone,” both being presented by Sir R. Griffith. The specimen is really Archeopteris Roemeriana, Gopp. Its smaller, non- overlapping, stalked pinnules are its distinguishing feature. Another important character is, it seems to me, the more erect habit of the pinne. They make a sharper angle (45°) with the rachis than the pinnee in 4. hibernica. he difference in habit suggests that A. Roemeriana was, in its habitat, more exposed to rain and sunshine than the shaded A. hibernica, with its broader, more horizontally placed pinne and pinnules. The former species seems to have provided channels for the passage downwards of the water falling on its leaves. Can one reconcile the difference of statement as to the presence of the rachidial pinnules, apart from the scrappiness of Goppert’s material? If such pinnules are vestigial, they should be less constantly present, and thus less often observable the more remote from its ancestors, i.e. the younger, the species is. If Archeopteris Roemeriana is more recent than A. hibernica, this would help to account for the statements made that in some specimens of A. Roemeriana no aphlebioid pinnules are observable. As both the Bear Island and the Irish specimens show, the aphlebiee cannot be excluded from the diagnosis of this species. Further, as Nathorst states, A. hibernica var. minor must stand as well as A. Roemeriana, since, as his figures and description show, Crépin’s variety possesses overlapping, unstalked pinnules, with decurrent base. I ought to mention that even in some of our specimens of true Archeopteris hibernica non-overlapping, smaller pinnules do occur on some of the pinne. True A. Roemeriana must possess no overlapping pinnules, and the pinnules must be attached to the rachis by a distinct stalk, a non-decurrent base. Such is the case in our Glanmire specimen. Hence the material in the Botanical Division of the National Museum, Dublin, shows the presence in the Upper Devonian beds of the South of Ireland of the following species :— 1. Archeopteris hibernica, Forbes, sp., first recorded in 1882. (Plate VIL, fig. 1, in part.) 2. A. hibernica, var. minor, Crépin. 3. A. Roemeriana, Gopp. sp. (Plate VIII.) 4, A. Tschermaki, Stur. (Plate VII., figs. 1,2, 3; text figs. 1 and 2.) Jounson— The Occurrence of Archeeopteris Tschermaki, Stur. 141 The accompanying table shows the distribution of the fertile species of Archeopteris as recorded :— DistripuTion oF Ferrite Species oF ARCH ®OPTERIS. F 3 Q g j ce a |e Se) Lees 3 S a I a a os aq i: 3 3 iS 3 ia elm |) ialce 5 Rn io 5 & a | 8 rae 5 . o 2 O o = SZ 7) cl -Q ta) nD ia) | | A. hibernica, Forbes, sp., . x x A. hibernica, var. minor, Crépin, x x A. Roemeriana, Gopp., sp.; : x x x A. intermedia,’ Nath., 6 : x A. fimbriata, Nath., 0 : x A. fissilis, Schmalh.,* 0 0 x x A. archetypus, Schmalh.,? x x A. Gaspiensis, Dawson, . 5 x A. Jacksoni, Dawson, 0 6 x 1 Sterile state only known. 2 D. White regards Archeopteris archetypus, Schmalh., and A. fissilis, Schmalh. as identical with the two American species, 4. obtusa, Lesqx., sp., and A. sphenophyllifolia. This view, if upheld, remoyes the anomaly of the geographical distribution of Schmalhausen’s two species, and indicates their occurrence in N. America. EXPLANATION OF PLATE VII. PLATE VII. Fig. 1. Slab from the yellow sandstone of Kiltorcan, Co. Kilkenny, showing at X a portion of a frond of Archeopteris Tschermaki, Stur ; overlapping Bothroden- dron kiltorkense, Haught., sp., and a fragment of A. hibernicu, Forbes, sp. Fig. 2. Reproduction of photograph of the upper fertile part of the frond, showing the two fertile segments or sporophyllules, each with a row of stalked sporangia. (See text-figure 1.) Fig. 8. Reproduction of photograph of the lower part of a frond of Archaopteris Tschermaki, showing the sculpturing of the midrib. Slightly magnified. (Photographed by T. Price of the Royal College of Science.) PLATE VII. SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. EXPLANATION OF PLATE VIII. PLATE VIII. Reproduction of photograph of Archaopteris Roemeriana, Gopp., from the Upper Devonian beds, Glanmire, Co. Cork. (Photographed by Mr. A. M‘Googan, Assistant in the Art Division, National Museum, Dublin.) SCIENT. PROC. R. DUBLIN SOC., N.S., VOL., XIII. PEATE VITE tet Jka SCIENTIFIC PROCEEDINGS. VOLUME XIII. . A Seed-Bearing Irish Pteridosperm, Crossotheca Hoéninghausi, Kidston (Lyginodendron oldhamiwm, Williamson). By T. Jounson, p.sc., F.u.s. (Plates I.-IIT.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorez H. Peruysriner, B.sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wcu1am Brown, B.sc. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Henry H. Drxon, sc.p., F.R.s. (April 20, 1911). 1s. . A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrtu1am J. Lyons, B.a., a.R.c.sc. (Lond). (May 16, 1911). 6d. . Radiant Matter. By Joun Joy, sc.p., r.z.s. (June 9, 1911.) Is. . The Inheritance of Milk-Yield in Cattle. By Jamms Wutson, M.A., B.SC. (June 12, 1911.) 1s. . Is Archeopteris a Pteridosperm? By T. Jounson, pD.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jouyson, p.sc.,¥.u.s. (Plates VII., VIII.) (June 28, 1911.) 1s. DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONKY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.8.), No. 10. JULY, 1911. AWARD OF THE BOYLE MEDAL TO PROFESSOR JOHN JOLY, M.A., Sc.D., F.RB.S., APRIL 25, 1911. pxwsani n instiiy > {<* Me \ AUG dk DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1911. Price Sixpence. Roval Dublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749 RVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. Th copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a ycomplete form, and ready for transmission to the [ditor. JouHnson— The Occurrence of Archeopteris Tschermaki, Stur. 141 The accompanying table shows the distribution of the fertile species of Archeopteris as recorded :— Disrrisutrion oF FERTILE Species oF ARCH AOPTERIS. : | 4 3 = : | or i 3 : a as nS @ 3s S =I A a a ons =| 1S = rs) Ss 3 R | Si 2 o 5) = 5 =| A 24 | n =) z Sj Fy |e Bye ; A o : eI a el | eh i ee | ee eis A. hibernica, Forbes, sp., - x x | A. hibernica, var. minor, Crépin, x x A. Roemeriana, Gopp., sp., x x x | A. intermedia, Nath., 3 4 x | a. fimbriata, Nath., ; 5 x A, fissilis, Schmalh.,* 6 0 x x | A. archetypus, Schmalh. ,* x x | A, Gaspiensis, Dawson, .- 9 x A. Jacksoni, Dawson, i , | x 1 Sterile state only known. 2D. White regards Arch@opteris archetypus, Schmalh., and A. fissilis, Schmalh. as identical with the two American species, A. obtusa, Lesqx., sp., and A. sphenophyllifolia. This view, if upheld, remoyes the anomaly of the geographical distribution of Schmalhausen’s two species, and indicates their occurrence in N. America, SCIENT. PROC. R.D.S., VOL. XIII., NO. IX, Yy X. AWARD OF THE BOYLE MEDAL TO PROFESSOR JOHN JOLY, M.A., Sc.D., F.R.S., 1911.2 In recommending the award of the Boyle Medal to Professor John Joly, the Science Committee direct attention to the very wide range of subjects covered by Dr. Joly’s researches, as well as to the general excellence of his work. His researches deal with various branches of Physics, Geology, Mineralogy, Botany, and Biological Theory; and in several of these widely different subjects he has enriched our laboratories with accurate instruments of research. In 1886 Joly published the method of condensation in calorimetry, and applied it by means of his steam calorimeter to the investigation of the specific heats of {minerals, attaining an accuracy previously impossible. By means of the same method he was shortly afterwards enabled to determine the specific heats of gases at constant volume, and so solved by experiment a problem of the highest importance in molecular theory. By means of another instrument, the meldometer, also invented by himself, Joly determined the fusion points of a large series of minerals, and showed how the same instrument was of value in carrying out the reactions of pyro- chemistry at known temperatures with greater certainty and delicacy than by the use of the blowpipe. By an original method he determined the volume change of certain rocks and minerals on fusion, and so contributed accurate knowledge of importance in geological physics. His invention of the incandescent electric furnace has also provided an instrument of much usefulness, having many applications in physical and geological investigation. In a paper on the origin of the Canals of Mars, Joly advanced a physical theory accounting for the linear markings on the planet, referring them to the gravitational effects of satellites moving close to its surface. By the application of the theories of colour-vision in 1896, he invented and elaborated a method of colour-photography by which he rendered it 1 The presentation was made at the Scientific Meeting of the Royal Dublin Society, held on the 25th April, 1911, when the medal was handed to Professor Joly by the chairman (Sir Howard Grubb, F,R.8.). Award of the Boyle Medal to Professor John Joly. 148 possible to reproduce with accuracy the colours of nature on a transparent plate. His work on the influence of temperature on the sensitiveness of the photographie plate and his theory that the latent image arises from photo- electric ionization may also be mentioned among his contributions to the science of photography. In 1898 he showed how the sodium content of the ocean could be used as a measure of geological time, and so was able to calculate the period which has elapsed since the beginning of denudation of the earth’s surface, and to establish a chronological unit of importance in cosmology. He also introduced the sodium content of the ocean as a factor enabling calculation to be extended to many far-reaching but hitherto indeterminate problems of solvent denuda- tion: for instance, the mass of the parent rock, the mass of the derived sediments, and of the sub-oceanic deposits. The theory of sedimentation has also been advanced by his researches on the cause and effects of electrolytic precipitation. By many researches he has laid the sciences of Petrology and Mineralogy under obligations to him. We would specially notice his invention of a polarizer whereby the value of birefringence as a means of identification is increased, and his application of the microscope to the determination of the quality of paving-sets and road-metal. In connexion with the new subject of radioactivity, the same happy combination of a knowledge of physics and geology, which he had already used with such effect in earlier researches, has enabled him not only to advance our knowledge of the properties of radioactive substances, but also to apply this knowledge to the explanation of geological phenomena of the most far-reaching importance. These investigations are summarized in his work on “ Radioactivity and Geology.” His explanation of pleochroic haloes in rocks as due to radioactivity removed a long outstanding difficulty, and leads to important conclusions as to the non-existence of alpha-radiation from common elements, and as to the absence or scarcity of radioactive substances other than those already known, and also affords a means of identifying quantities of radioactive matter in sitw far less than can be detected by other methods. By the determination of the thorium content of over 150 igneous and sedimentary rocks (using a method of his own), he has for the first time established a probable mean value for the distribution of that element in the various surface-materials of the earth. To the literature of speculative philosophy Joly has also contributed. Here may be mentioned, more especially, an essay on the ‘‘ Prematerial Condition of the Universe,” and one (“‘ The Abundance of Life”) on the physical laws underlying organic evolution. y2 144 Scientific Proceedinys, Royal Dublin Society. It would not be fitting in this report to leave out all mention of Joly’s work for the Royal Dublin Society. No man has done more for the Society both by giving to its publications his best work, and also by his wise counsels in the direction of its affairs, first for eight years as a member of the Council, and subsequently for twelve years as one of the Society’s Honorary Secretaries. In this latter position his world-wide reputation was no small addition to the prestige of the Section which he represented ; while his scientific zeal did not prevent him devoting an immense amount of energy to forwarding the general aims of the Society. He, with the late Professor Cunningham, suggested the Royal Dublin Society’s scheme of marine research, which was afterwards taken over by the Department of Agriculture ; and he was responsible for the policy and was foremost in the negotiations by which the Royal Dublin Society acquired the new Art Industries Hall. List or Pusxications. i. Onan Apparatus for obtaining Telegraphically the Readings of Meteorological Instruments placed at a distance from the Observer. Proc. R.D.S. 1888. 2. Notes on the Microscropical Character of the Volcanic Ash from Krakatoa. Proc. R.D.S. 1884. 3. On Photometers made of solid Paraffin, or other Translucent Substance. Proc. R.D.S. 1885. 4. On a Hydrostatic Balance. Proc. R.D.S. 1886. 5. On a Method of Determining the Specific Gravity of Small Quantities of Dense or Porous Bodies. Proc. R.D.S. 1886. 6. Notes on the Minerals of the Dublin and Wicklow Granite. 1. The Beryl and Iolite of Glencullen. Proc. R.D.S. 1886. 7. On the Occurrence of Harmotome at Glendalough, Co. Wicklow. Proc. R.D.S. 1886. 8. On the Permanency of Frost-Marks, and a possible connexion therewith, with Oldhamia radiata and O. antiqua. Proc. R.D.S. 1886. 9. On a Method of Condensation in Calorimetry. Proc. R.8. 1886. 10. On the Specific Heats of Minerals. Proc. R.S. 1886. 11. On the Phenomena of Skating, and Prof. J. Thomson’s Thermodynamic elation. Proc. R.D.S. 1887. 12. On the Formation of Crystals of Calcium Oxide and Magnesium Oxide in the Oxyhydrogen Flame. Proc. R.D.S. 1888. 13. With Prof. G. F. FirzGrratp.—On the Measurement of Small Pressures. Proce. R.D.S. 1888. 14. On the Steam Calorimeter. Proc. R.S. 1889. Award of the Boyle Medal to Professor John Joly. 145 15. A Resonance Method of Measuring the Constant of Gravitation. Nature, Jan. 16. 1890. 16. On a Method of Determining the Absolute Density of a Gas. Proc. R.D.S. 1890. 17. The Abundance of Life. Proc. R.D.S. 1891. 18. On the Determination of the Melting-Points of Minerals. Proc. R.1.A. 19. Crystals of Platinum and Paladium. Nature. April 9, 1891. 20. On the Specific Heats of Gases at Constant Volume. Part I. Phil. Trans., RS. 1891. 21. On a Direct Reading Electrolytic Ampere Meter. Proc. R.D.S. 1892. 22. On a Mercury Glycerine Barometer. Proc. R.D.S. 1892. 23. On Shutters for Use in Stellar Photography. Proc. R.D.S. 1892. 24, On a Speculation as to a Prematerial Condition of the Universe. Proc. R.D.S. 1892. 25. On the Bright Colours of Alpine Flowers. Proc. R.D.S. 1893. 26. On a Photographic Method of Detecting the Existence of Variable Stars. Proc. R.D.8. 1893. 27. On the Influence of Temperature upon the Sensitiveness of the Photo- graphic Dry Plate. Proc. R.D.S. 1894. 28. On the Specific Heat of Gases at Constant Volume. PartII. Phil Trans. R.S. 1894. 29. On the Thermal Expansion of Diamond. Nature, 1894. 30. On Useful Methods of Teaching Elementary Physics. Proc. R.D.S. 1894. 31. The Ratio of the Latent Heat of Steam to the Specific Heat of Water (contained in Principal Griffith’s Memoir on the Latent Heat of Evaporation of Water). Phil. Trans. R.S. 1894. 32. With H. H. Drxon.—On the Ascent of Sap. Phil. Trans. R. S$. 1895. 33. With H. H. Drxon.—On the Path of the Transpiration Current. Annals of Botany, Sept. 1896. 34. On a Method of Photography in Natural Colours. Trans. R.D.S. 1896. 35. On the Geological Investigation of Submarine Rocks. Proc. R.D.S. 1897. 36. On the Origin of the Canals of Mars. Trans. R.D.S. 1897. 37. On the Volume Change of Rocks and Minerals attending Fusion. Trans. R.D.S. 1897. 38. A Theory of Sun-Spots. Proc. R.D.S. 1898. 39. With H. H. Drxon.—On Some Minute Organisms found in the Surface Water of Dublin and Killiney Bays. Proc. R.D.S. 1898. 40. An Hstimate of the Geological Age of the Marth. rans. R.D.S. 1899. 146 ‘Scientific Proceedings, Royal Dublin Society. 41. A Fractionating Rain-Gauge. Proc. R.D.S. 1900. 42, Influence of Pressure on the Separation of Silicates in Igneous Rocks. Proc. R.D.S. 1900. 43. On the Imer Mechanism of Sedimentation—Preliminary Note. Proc. R.D.S. 1900. 44. Theory of the Order of Formation of Silicates in Igneous Rocks. Proc. R.D.S. 1900. 45. The Geological Age of the Harth. Geol Mag. May, 1900. 46. Du Mécanisme intime de la Sédimentation. Congrés Géologique Internat. 1900. 47. Wxpérience sur la Dénudation par Dissolution dans VYeau douce et dans Veau de Mer. Congres Géologique Internat. 1900. 48. Mémoire sur Ordre de Formation des Silicates dans les Roches Ignées. Congres Géologique Internat. 1900. 49. Incandescent Electric Furnaces. Proc. R.DS. 1901. 50. On an Improved Method of Identifying Crystals in Rock-Sections by the Use of Birefringence. Proc. R.D.S. 1901. 51. On the Pseudo-opacity of Anatase. Proc. R.D.S. 1901. 52. Some Sedimentation Experiments and Theories. Trans. R.D.S. 1901. 53. Denudation in Fresh and Salt Water. Proc. R.I.A. 1901. 54. The Circulation of Salt and Geological Time. Geol. Mag. Aug., 1901. 55. Method of Observing the Altitude of a Celestial Object at Sea at Night- time, or when the Horizon is obscured. Proce. R.D.S. 1902. 56. An Improved Polarizing Vertical luminator. Proc. R.D.S. 1908. 57. On the Conservation of Mass. Trans. R.D.S. 1903. 58. The Petrological Examination of Paving-Sets. Proc. R.D.S. 1903. 59. Radium and the Geological Age of the Harth. Nature, Oct. 1st, 1903. 60. Radium and the Sun’s Heat. Nature. Oct. 15, 19038. 61. Formation of Sand-Ripples. Proc. R.D.S. 1904. 62. On the Motion of Radium in an Hlectric Field. Phil. Mag. March, 1904. 63. The Latent Image. Address to the Photographic Convention. Nature. July 29, 1905. 64. On Floating Breakwaters. Proc. R.D.S. 1905. 65. On the Petrological Examination of Road-Metal. Proc. R.D.S. 1905. 66. Method of Determining the Absolute Dilatation of Mercury. Proc. R.D.S. 1907. 67. On Pleochroic Haloes. Phil. Mag. March, 1907. 68. On the Radium Content of Deep-Sea Sediments. Proc. R.D.S. 1908. 69. The Radioactivity of Sea- Water. Proc. R.D.S. 1908. Award of the Boyle Medal to Professor John Joly. 147 70. On the Radium Content of Deep-Sea Sediments. Phil. Mag. July, 1908. 71. Uranium and Geology. President’s Address to Section C, Brit. Assoc., Dublin, 1908. 72. On the Distribution of Thorium in the EKarth’s Surface-Materials. Phil. Mag. May, 1909. 73. On the Distribution of Thorium in the Harth’s Surface-Materials. Phil. Mag. July, 1909. 74. On the Radium Content of Sea Water. Phil. Mag. Sept., 1909. 75. On the Radioactivity of Certain Lavas. Phil. Mag. Oct., 1909. 76. Pleochroic Haloes. Phil. Mag. Feb., 1910. 77. Pleochroic Haloes. Nature. Feb. 10th, 1910. 78. With Arnoup L. Furrcuer.—Pleochroic Haloes. Phil. Mag. April, 1910. 79. On the Amount of Thorium in Sedimentary Rocks—I Calcareous and Dolomitic Rocks. Phil. Mag. July, 1910. 80. On the Amount of Thorium in the Sedimentary Rocks—II Arenaceous and Argillaceous Rocks. Phil. Mag. Aug., 1910. 81. Radioactivity and Geology: An Account of the Influence of Radioactive Energy on Terrestrial History. London. Archibald Constable and Co., 1909. 1. 10. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghwusi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, b.sc., ¥F.1.S. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Groren H. Prruysripes, B.sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wittram Brown, B.so. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Hunry H. Drxon, so.d., F.R.s. (April 20, 1911). 1s. A Method of Exact Determination of the Contmuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wuut1am J. Lyons, B.A., a.R.c.so. (LonD). (May 16,1911). 6d. . Radiant Matter. By Joun Joy, so.p., r.x.s. (June 9, 1911.) 1s. . The Inheritance of Milk-Yield in Cattle. By Jamms Winson, M.a., B.SO. (June 12,1911.) 1s. . Is Archopteris a Pteridosperm? By T. Jounson, D.sc., ¥.u.s. (Plates TV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archaopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By 'T. Jonnson, D.sc.,F.u.s. (Plates VII, VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Prorussor Joan Joy, M.a., sc.D., r.R.S. (July, Gili) Gel, DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XII. (N.S.), No. 11. AUGUST, 1911. ON THE AMOUNT OF RADIUM EMANATION IN THE SOIL AND ITS ESCAPE INTO THE ATMOSPHERE. BY JOHN JOLY, Sc.D., F.R.S., PROFESSOR OF GEOLOGY AND MINERALOGY IN THE UNIVERSITY OF DUBLIN, AND LOUIS B. SMYTH, B.A., ASSISTANT TO THE PROFESSOR OF GEOLOGY. (PLATE IX.) | Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. - 1911, Price One Shilling Roval Dublin Soctety. Oe FOUNDED, A.D. 1731. INCORPORATED, 1749. ~— EVENING SCIENTIFIC MEETINGS. Tun Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. Th copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission to the Editor. 70 71 Award of the Boyle Medal to Professor John Joly. 147 . On the Radium Content of Deep-Sea Sediments. Phil. Mag. July, 1908. . Uranium and Geology. President’s Address to Section C, Brit. Assoc., Dublin, 1908. 72. On the Distribution of Thorium in the Earth’s Surface-Materials. Phil. Mag. May, 1909. 73. On the Distribution of Thorium in the HFarth’s Surface-Materials. Phil. Mag. July, 1909. 74. On the Radium Content of Sea Water. Phil. Mag. Sept., 1909. 75. On the Radioactivity of Certain Lavas. Phil. Mag. Oct., 1909. 76. Pleochroic Haloes. Phil. Mag. Feb., 1910. 77. Pleochroic Haloes. Nature. Feb. 10th, 1910. 78. With Arnoxp L. Firrcuer.—Pleochroic Haloes. Phil. Mag. April, 1910. 79. On the Amount of Thorium in Sedimentary Rocks—I Calcareous and Dolomitic Rocks. Phil. Mag. July, 1910. 80. On the Amount of Thorium in the Sedimentary Rocks—II Arenaceous and A 81 rgillaceous Rocks. Phil. Mag. Aug., 1910. . Radioactivity and Geology: An Account of the Influence of Radioactive Energy on Terrestrial History. London. Archibald Constable and Co., 1909. 5 CIENT. PROC. R.D.S., VOL, XIII., NO. XI, Z [14s 4] KIT. ON THE AMOUNT OF RADIUM EMANATION IN THE SOIL AND ITS ESCAPE INTO THE ATMOSPHERE. By JOHN JOLY, Sc.D., F.R.S., Professor of Geology and Mineralogy in the University of Dublin, AND LOUIS B. SMYTH, B.A., Assistant to the Professor of Geology, Univ. Dubl. (Prater iX.) [Read, Junz 27. Received for Publication, Junr 27. Published, Avausr 29, 1911.] 'I'o adequately review the development of the subject of the radioactivity of the gases of the soils would demand much space ; nor is it necessary for the statement of the observations which we have to record upon this subject. A brief sketch of the state of our knowledge will suffice. The pioneer observations of Elster and Geitel showed that a wire freely exposed to the atmosphere and maintained at high negative potential had condensed upon it a radioactive substance which could be removed by friction or by solution, and which when brought into an electroscope much increased the ionization. It is now well known that this active deposit is derived from the break-up of radioactive emanations in the atmosphere. The active deposit detected by Hlster and Geitel has been observed in many parts of the world, and at high altitudes on mountain tops. It has been found in rainwater and in snow. The early observations of Rutherford and Allen in Canada’ on the rate of decay of the active deposit collected from the atmosphere by means of a negatively electrified wire, were followed by many others showing that in many cases the rate of decay indicated that the deposit is that arising from the disintegration of the emanation of radium. Subsequent observations showed that the active deposit upon the wire often behaved as if active deposit from the emanation of thorium was also present. 1 Phil. Mag., Dec., 1902, Jouy ano Smyvvu—Amount of Radium Emanation in the Soil. 149 The variations in the amount of active deposit from one locality to another are very marked. In hilly and mountainous regions—whether observations are made in the valleys or on the hill-tops—high readings are obtained. In such regions the surface-area of the ground is larger than upon the plains; and the observations are, therefore, in keeping with the view that the active substances originate in the earth. Near the sea the readings are generally lower. But the average amount of radioactive con- stituents in sea air cannot be said to be determinable from existing observa- tions. ‘I'he lately published observations of Simpson and Wright render it certain that there is considerably less over the sea than over the land. No steady interdependence between the amount of active constituents in the atmosphere and the temperature, moisture, time of year, or daily period of the potential gradient of the atmosphere, has been demonstrated. There is some evidence that a steadily falling barometer is attended by an increase in the amount of active substances in the air; but there are many discordant observations. One fact may be regarded as supported by the majority of observations :—that settled anticyclonic conditions, involving still weather, are favourable to an accumulation of radioactive constituents in the lower atmosphere. Eve,? however, arrived at the opposite conclusion. It is evident that if the soil is the source of the active constituents, the local con- ditions will largely enter into the question as to whether a still atmosphere is favourable or otherwise to the radioactivity of the atmosphere. The existence of radioactive matter in the atmosphere is connected with the presence of radioactive substances in the rocks by observations upon the active character of gases contained in the pores and capillaries of the soils. There is a striking parallel between the results of the observations upon “‘ vrouud-air ” and those we have been reviewing. The radioactivity of the ground-air has been directly observed. Hlster and Geitel found that air withdrawn from the soil possessed a conductivity as much as thirty times that of the atmosphere, and that this conductivity was not fixed in amount for a given sample of air, but at first increased for some hours—a proof of its radioactive character. It is important to note that the measure of the conductivity of the air does not express the emana- tion content. ‘The presence of moisture or dust in such gases will often, by reducing the number of small ions, lower the conductivity, although much emanation may be present.? Mbert and Hwers' deprived ground-air of its small ions by passing it through a strong electric field, and found that such air had, in three hours, regained its original conductivity—a result due 1 Proc. Roy. Soc., May, 1911. 2 Phil. Mag., Oct., 1908. 3 A. Gockel, Die Luft Electricitat. 4 Phys. Zeit. iv., 162, 1903. z2 150 Scientific Proceedings, Royal Dublin Society. to the break-up of the emanation which, owing to its purely gaseous properties, had escaped the electric field. The radioactivity of ground-air is very variable from time to time in the one locality. HH. Brandes! found that the emanation content of ground-air increases with a slow fall of the barometer, and vice versa; but sudden changes of pressure may produce effects of the opposite character. No connexion between the content of emanation and the actual height of the barometer could be traced. Gockel? confirms the observations as to the variability of the ground-air from time to time, and finds that the most effective influences are those which affect the permeability of the soil, such as rain or frost. ‘These tend to increase the emanation content, by choking the capillaries. Hive’ estimated the amount of radium emanation in the atmosphere by abstracting the active deposit from the air enclosed in a large tank. By a comparison of the ionization produced by a known amount of the active deposit of radium with that due to the active deposit derived from the air in the tank, he concluded that in a cubic metre of air the amount of emanation which would be in equilibrium with 80x 10-’ gram of radium must be present. Since this observation of Eve’s, measurements of the radioactive sub- stances in the atmosphere have been made by direct abstraction of the emana- tion. Thus Eve,‘ Ashman,’ and Satterly’ have used either the absorptive properties of charcoal, discovered by Rutherford, or the low temperature of liquid air, to condense it directly from the atmosphere. In this manner the emanation from 100 to 200 litres of air has been brought into the electro- scope. ‘These observations confirm Eve's original measurement. Satterly finds 100 x 10°? per cub. metre. ‘he variations from day to day are con- siderable. Ashman finds the equivalent radium to vary from 45 x 10% to 200 x 10° gram per cubic metre. ive’ finds the variation as much as 1 to 7. Of the reliability of these results there can be no doubt ; and, following Eve, we may accept 80x10 gram as the amount of radium in equilibrium with the emanation contained in one cubic metre of average air. How high in the atmosphere these conditions extend is not known. ‘The emanation has a half-life period of 3:7 days. The circulatory movements of the atmosphere are comparatively rapid, so that a marked falling-off in the contents of radium emanation upwards is not to be expected. Nevertheless, if we assume that 1H. Brandes, Inaugural Dissertation, Kiel, 1905. 2 A Gockel, Phys. Zeit. 1x., 304, 1908. 5° Eye, Phil. Mag., July, 1905. 4 Eve, Phil. Mag., Oct., 1908. 5 Ashman, Am. J. Sci., xxvi, 119, 1908. ® Satterly, Phil. Mag., Oct., 1908. 7 Eve, loc. cit. JoLy and Smyrui—-Amount of Radium Emanation in the Soil, 151 the observed richness in radium emanation extends no higher than 5 kilometres, we find, at first sight, difficulty in accounting for the large aggregate of emanation involved. In a vertical height of 5 kilometres there is over each square metre of the land-surface 80 x 107? x 5000 gram radium-equivalent of emanation. In 3°7 days half this amount breaks up. There appears to be only one source from which it can be recuperated—the materials spread over the surface of the land. This is the hypothesis which first presents itself. Of the surface- materials we may confine our attention to the soils; the unbroken rock- surfaces can make but a negligible contribution. The demand on the soils is even more considerable than this fact implies. It appears highly probable that the radium emanation observed to exist over the oceans must be, in part, derived from the land. We may calculate from the known rate of break-up of the radium emana- tion the amount which must leave in unit time each square metre of land- surface. This will be the average exhalation of emanation. We take the atmosphere as radioactively homogeneous to a height of 5 kilometres, and neglect non-productive areas on the land and the contribution of the land to the ocean. The radioactive constant of the emanation is nearly 2x 10°. The quantity, therefore, transforming each second in the atmosphere over each square metre, expressed as the equivalent radium, is 4x 107x2x10°=0°8x10¥ gram. This amount must, on the average, exhale each second from each square metre, or, say, 2880 x 10-” per hour. In order to investigate how far this condition might be fulfilled, we have made experiments (a) on the amount of radium emanation contained in the gases diffused through the soil, and (2) on the amount escaping from the surface of the soil. Experiments on ground-gases were begun in April this year (1911) at the conclusion of a long spell of dry weather. The first series of observations were carried out in the Park of Trinity College, Dublin. The method of experiment- ing is easily understood. Aun iron tube is closed at one end by a plug of pointed iron. ‘he tube is drilled with small holes just above the plug, the holes being sloped both downwards towards the plug and inwards, in passing through the metal. ‘This tube is driven to the required depth in the ground. The holes above the conical point, in virtue of their sloping direction, do not get clogged. The gases of the soil are withdrawn from the projecting end of the tube, which is fitted with a rubber stopper and a leading tube of glass. ‘l'his glass tube is normally kept closed by rubber tube and pinch-cock. As the iron tube has a clear bore of about 1°5 cms., an inner tube of brass, fitting 152 Scientific Proceedings, Royal Dublin Society. loosely, and closed at each end, is inserted into the iron tube, thereby, in effect, reducing its bore and its gas-content. In order to withdraw the ground-gas, an ordinary boiling-flask is exhausted of air, carried to the iron tube, and attached to it by the rubber connecting- tube. On opening the connexions, air flows from the ground into the flask. A little water is kept in the flask, and the entering air is caused to bubble through this water; in this manner the rate of entry of air is under observation, and it is known when the flask is quite filled. When the flask is full, it is brought into the laboratory, let stand for about 15 or 20 minutes, in order to allow of the decay of the emanation of thorium, and then attached to the exhausted electroscope. ‘The latter is filled from the flask, water being let flow into the flask according as air leaves it. In our experiments the flask held about one litre, and the electroscope about 600 ces. Thus, a portion only of the air withdrawn from the soil was used for measurement. The electroscope used is calibrated by the emanation from a known amount of radium in the usual manner. Before the admission of the ground-gas the rate of discharge of the electroscope is observed, and again for about thirty minutes after the admission of the gas, and finally three hours after admission. From the knowledge of the calibration constant of the instrument the amount of emanation being dealt with is easily arrived at. ‘lhe quantity of emanation in a litre of similar gas is then calculated on the known volume of the electro- scope. This method of determining the emanation content of the ground-gases is free from instrumental factors, being simply and directly comparative. In the foregoing manner the following observations were carried out. Three suction-pipes were in use. ‘Their depths were finally brought to 25, 100, and 150 ems. he pipes were within 4 or 5 metres of one another, in the grass on the east side of the School of Engineering, and in ground which had not been disturbed for many years. ‘The soil is calcareous, and presents no abnormal features. It extends to a depth of several metres, and is well drained. In the third column of the Table we give the radium equivalent of the emanation per litre of ground-gas in billionths of a gramme, and in the fourth column the ratio of this to the normal emanation content of the atmosphere, taking the latter as 8 x L0™ per litre. JoLy AND Smytra—Amount of Radium Emanation in the Soil. 158 Tasie I. Experiments in grounds of Trinity College, Dublin. panalion Em. = by Date. Depth, ems. er litre. oe ae Gum x 1072. 8x 10u. April 17 20 45 563 18 20 20 250 19 20 23 290 19 50 20 250 20 20 141 1760 20 50 135 1700 21 100 181 2262 21 20 90 1100 92 100 230 2875 22 20 140 1750 24 100 210 2620 24 20 160 2000 25 100 187 2340 95 20 160 2000 26 100 156 1950 26 25 200 2500 27 150 7) 940 oT 25 230 2900 28 150 71 900 28 25 180 2250 29 150 127 1600 29 25 225 2810 May 1 150 | 153 1900 arent 150 155 1940 2 25 205 2560 | 3 150 161 2100 4 150 161 2000 5 150 161 2000 6 25 276 } 3450 7 25 325 | 4060 10 250 j 134 1670 12 150 i 173 2160 15 25 293 | 3630 16 25 271 3400 16 | 100 420 | 5250 17 | 25 283 | 3940 17 100 440 5500 | June 7 | 100 230 | 2900 - | Experiments of the same character were begun near Milltown, Co. Dublin, about two miles south of the College, in a tennis-court at Somerset House. In these experiments the tube was consistently kept at a depth of 25 ems. Its position in the tennis-court was, however, occasionally varied. The soil is here not very different in character from that of the College, but is less blackened by atmospheric impurities. It is essentially calcareous, but is not so pervious beneath as the College soil. A close and heavy sub-soil comes within « metre of the surface; the depth before rock is met must, however» be very considerable. It will be seen from the adjoining Table that the emanation richness of this soil greatly exceeds that of the College Park. 154 Scientific Proceedings, Royal Dublin Society. Tasie IT. Experiments in the Grounds of Somerset House, Milltown. Date. Depth, cms. ae Em. =8 x 10-4. May 1 25 1300 16200 | 3 a 1115 14000 4 A 1080 13500 5 99 1510 18900 6 i 1191 15000 | 8 oA 860 10780 9 i 1080 13500 10 99 1420 17800 ll 4 1050 12500 12 yi 1302 16300 15 s 1050 12500 A few observations were also made on the west side of the city, at Inchicore and Kilmainham. Tas.e III. Experiments at Inchicore and Kilmainham, Co, Dublin. Date. Depth, cms. pee Im. = 8 x 10-14. | i | May 18 | 25 630 7900 19 | » 680 8500 | 22 ay 370 4600 24 05 254 3000 Of the above observations the first is in a garden at Inchicore ; the second in a meadow close by; the third in garden-grass at Kilmainham; and the fourth in cultivated garden-soil at Kilmainham. ‘These points are about three miles to the west of the College. ‘he soil in this neighbourhood ‘is, again, much the same in origin as that of the College, Carboniferous limestone underlying this part of the Co, Dublin, and the soil above owing much to the glacial drift, Jory anp SuvrH—Amount of Radium Emanation in the Soil. 155 The observations are, so far, confined to the amount of radium emanation contained in the gases of the soil. It is necessarily part of the inquiry to determine whether these are of sufficient richness to allow of the atmospheric emanation being ascribed to this source. The experiments show that in every case the emanation content of the soil-gas is very much greater than that of the atmosphere—in most cases some thousands of times. Obviously this is but a step in the investigation. The emanation in the capillaries of the soil might pursue its changes within the soil, and never escape into the atmo- sphere. It will presently be seen that the variations in the emanation content of the ground-gases, taken in connexion with the weather changes progressing during the experiments, afford strong evidence that the emanation escapes freely into the atmosphere. More direct proof of this is, however, very desirable. Accordingly, observations were made both in the College Park and at Somerset House to determine, if possible, the rate at which the emanation quitted the surface of the soil. The observation of this phenomenon presents some difficulties. Un- doubtedly under normal conditions the motion of the air over the surface of the ground must greatly facilitate, if it does not actually occasion, the escape of ground-gases. A collector in the form of a bell-shaped vessel placed mouth downwards upon the surface of the ground does not, therefore, realize the natural conditions when there is any motion of the air. It does not even realize the conditions of the stillest weather, for the diffusion outwards, attending the differing composition of the ground-gases from those of the atmosphere, must ultimately be brought to an end by the attainment of uniformity of chemical composition immediately beneath and above the surface. A collecting-vessel of this sort left im sitw for an hour will accumulate but little emanation, as may be determined by filling an electro- scope from its contents. Doubtless if left in sitw long enough the result would be different. The point is that this arrangement does not realize the con- ditions which go towards accelerating and facilitating the escape of emanation at the surface. It permits, in fact, only of diffusive movements, and these under very unfavourable circumstances. A modification of this arrangement which secures a gentle motion of the air over the surface of the soil, without at the same time creating a local reduction of atmospheric pressure, serves to show that during the space of one hour a very considerable amount of emanation actually leaves a soil freely exposed to the atmosphere. The collector designed on these principles will be easily understood from the figure. It consists of a cylindrical vessel of tin plate, about 20 cms. in diameter and 8 cms. deep. One end is closed save for a central opening SCIENT. PROC. R.D.S., VOL. XIII., NO. XI. 2a 156 Scientific Proceedings, Royal Dublin Society. 3 cms. in diameter. ‘he other is open and rests upon the ground, the edge being pressed in, as shown, when an experiment is progressing. Within this collector there is a disk of tin plate resting on feet which raise it about 3 cms. off the soil. It is about 1 centimetre less in diameter than the collector. The disk is centrally perforated, and carries a vertical tube which emerges through the opening on top of the collector. ‘The air-suction is applied to this pipe. This evidently gives rise to air-currents within the collector which pursue the course shown by the arrows. Of course it is impossible to secure uniformity in the currents; but, on the whole, there must be a radial and inward draught beneath the disk. As the entry of air is perfectly free and the rate of air-suction slow, there is no sensible reduction of pressure beneath the collector. This is shown by the fact that variations in the air-suction rate do not seem to sensibly affect the results, some of the highest being obtained with air-currents at the rate of 7-5 litres per hour, and some of the lowest with rates of about 25 litres per hour. ‘The experiment was also tried of placing a thin cardboard disk centrally on the ground just beneath the uptake tube. No difference in the results was noticed. In order to collect the emanation withdrawn during an hour’s application of the air-draught, the air-current drawn from the collector is led over cocoa- nut charcoal contained in a quartz tube. The emanation is thus, for the greater part, absorbed. ‘he quartz tube (a porcelain tube was also on some oceasions used) is about 1'5 cms. internal diam., and 50 ems. in length. The central part is filled with about 50 grams of the charcoal, not too finely pulverized. Loose asbestos fills the remainder of the tube. After the draught has run for an hour this tube is attached to a strong indiarubber bag and heated in a gas-furnace for about forty minutes. ‘The contents of the bag are then admitted into an exhausted electroscope. The emanation is determined by observation of the electroscope as already described. Jory and SuyvH—Amount of Radium Emanation in the Soil. 157 In this manner the observations given in Table IV were carried out in the College grounds at a point close to the outer wall of the Laboratory on the east side and in grass. The area covered by the collector being just about one twenty-fifth part of a square metre, the amount of emanation in the electro- scope multiplied by 25 is entered in the second column as the amount of emanation escaping per square metre per hour, Tasie LV. Experiments on the Exhalation of Radium Emanation in the Grounds of Trinity College. Date Emanation per square metre per hour. May 3 2600 3 Ort 4 135 0Ruee | 5 GOO 5, 8 HOB gy 10 360 5 | 12 D0 13 50 15 B80 oy 16 1000 90 | 17 600M ss It was thought desirable to make similar observations at Somerset House. The observations were partly in grass, partly in open soil, at a point adjoin- ing the tennis-court. It will be seen that these results are in keeping with those on the ground-gases. In these experiments the rate of flow of the air- draught through the collector was not very different from that used generally in the experiments recorded above, the amount of negative pressure at a point between the charcoal tube and the water-pump being sensibly the same in both cases ; that is, it was found to be such as would balance a head of from 10 to 20 cms. of water. The pump was always run with this gauge in operation, both in the case of the experiments made in College and those made at Somerset House. The exact measure of the air-flow in the case of the former experiments was ascertained by finding the time required for a certain volume of air contained in an indiarubber bag to be withdrawn by the pump. 2a2 158 Scientific Proceedings, Royal Dublin Society. Taster VI. Experiments on the Exhalation of Emanation of Radium in the Grounds of Somerset House. Date. Py aera eS metre ( | May 19 1160 x 10-1? 20 | 1720 eae 22 | GED op 23 | TO gp 25 5200s, 26 i620) aes 30 9600 _,, 31 1303) June 1 2350 i 5 1600, 6 6000s, 7 7000, The first four of these results were obtained when the collector was on grass; the remainder when it stood on open, compact soil. Throughout these exhalation experiments there is a source of error which has to be considered. The air drawn through the charcoal tube is derived from the atmosphere, and accordingly contains the amount of emanation pre- vailing at the time. It is easy to see that the error is small. The average rate of the air-current involves the passage through the charcoal of about 15 litres in the hour. This will be found to involve a correction on the figures tabulated of about 80 x 107°. As doubtless other sources of uncertainty of more considerable magnitude prevail, and as it is probable that the method on the whole underestimates the escape of emanation under normal conditions, we have not made this correction. The results now given can best be studied by plotting them on loga- rithmic paper. As there is a certain relation between the several series of experiments, all are plotted upon the one sheet. There are some points of special interest. The results for ground-gases from a depth of 25 cms. selected from Table I are seen to rise from a relatively low to a high value. The explana- Jony AND SMYTH Amount of Radium Emanation in the Soil. 159 tion is that the earlier observations were made at the conclusion of a long period of drought, during which the escape of gases from the soil had been unimpeded by free moisture choking the capillaries. A period of rainy weather then set in, and the emanation began to accumulate. Near the beginning of May fair, dry weather again set in, when the radioactivity of the ground-gases began to decline, and continued to fall throughout the earlier part of the long spell of fine weather which succeeded. The experi- ments ceased on May 17th. Careful comparison with the barometric curves of the period covered by the experiments shows no direct influence of changing pressure upon the readings. The results obtained from depths of 100 cms. show what appears to be a lag on those from the lesser depth—just such a lag as changes of temperature arising from diurnal or seasonal changes at the surface would show. The points of minimum and maximum emanation richness are at a later date than those observed at the depth of 25 ems. Followed up to June 7th they show that a rapid rate of loss of emanation was prevailing, even at this depth, during the phenomenal drought of May and June this year. When, lastly, we select the observations referring to a depth of 150 cms., we see indications of a still greater lag behind those of 25 ems. The recovery from the initial depression seems displaced about ten days later, and the partial depression of May Ist also to ten days later. The readings, as might be expected, showed on the whole a less degree of fluctuation. The readings at Milltown were only commenced when the fine weather was just coming in. ‘The absolute values of the readings are so high that they have to be plotted to one-tenth the scale of those taken in Trinity College. They agree in their tendency with those at a similar depth in the city. Mr. A. L. Fletcher was so kind as to make a determination of the radium content of the soils in the College Park and at Somerset House. As it is only the finer constituents which can supply any large amount of emanation to the ground-gases, the material examined was obtained by sifting from the soils the finer particles. A mesh of 60 to the inch was used. ‘he powders so obtained were treated in the electric furnace by the fusion method. ‘The radium content of the fine constituents from the College Park was found to be 2-8 gram per gram; that from Somerset House 5°2 gram per gram. ‘The quantity of the finer constituents in the two soils was 46 per cent. and 56 per cent. respectively. Coming now to the exhalation experiments in Trinity College, the interesting fact appears that progressive variations in the amount of emana- tion exhaled from the soil are attended by progressive changes in the other 166 Scientific Proceedings, Royal Dublin Society. direction in the amount of emanation accumulating beneath the surface—a result which might be anticipated. When rain chokes the soil, the amount of emanation beneath begins to accumulate, as Gockel has pointed out. The choking of the capillaries correspondingly reduces the amount of emanation escaping at the surface. Hence when the one quantity is on the increase, the other is on the decrease. We conclude, therefore, that fine weather tends to diminish, and wet weather to increase, the richness of the eround-gases. It is probable that after prolonged dry weather the amount exhaled reaches a steady state. Further simultaneous experiments on the amounts of emanation being exhaled and accumulating are desirable. It is also desirable to investigate the rate of exhalation at various times in the day and night. Our observations were in nearly all cases made in the forenoon. The most interesting feature of these experiments is the large amounts of emanation which are found to escape from the surface of the soil. We have already pointed out that the results obtained by several observers indicate an amount of emanation in the atmosphere which, on average conditions, would be in equilibrium with 80x10" gram radium per cubic metre ; and that from this we must conclude that there must decay each hour the equivalent of 2880x10-" gram radium over each square metre of the land-surface, assuming the radioactively homogeneous atmosphere to extend to a height of 5 kilometres. his figure is frequently exceeded by our observations near Milltown. It will remain for further experiments to show whether similar high results are of common occurrence. In the College Park it ig in no case reached. It must be remembered, however, that not only is the atmospheric content of radium emanation found to be very variable, but we are by no means sure of our assumption that the atmosphere is radio- actively homogeneous to a height of 5 kilometres. J¢ appears as if the JSoregoing observations support the conclusion that the gases which exhale from the soil are the chief and, probably, only considerable source of the emanation found in the atmosphere. It is difficult to avoid the speculative conclusion that such large amounts of emanation in the soils---and it must be remembered we have attended to the emanation of radium only—exert an important influence on organic activity. Jor instance, it seems probable that vegetable life is largely affected by ionizing activities which have been shown to be capable of decomposing carbon dioxide and other stable substances. Some experiments upon the bearing on vegetable life of the soil-gases have been commenced. The subject is attended with many difficulties, and it is too soon to report upon the results. Since our experiments were commenced a paper has reached us recording results obtained by Professor wart and Mr. Nightingall at Melbourne, on Jony and Smyru—Amount of Radium Emanation in the Soil. 161 the effects of adding radioactive materials to soils upon which wheat was raised. These results are positive, but they leave some uncertainty as to the actual nature of the influences at work. Whether the exhalation of radioactive gases from the soil in a district influences the well-being of the higher organisms which inhabit it remains to be ascertained. The physiological and pathological influences of radioactive emanations are only beginning to be studied. Descriprion or CuArr (Plate IX.). The numbers on the vertical axis are to be multiplied by 10°. Where the quantities dealt with are too large, the further multipliers 10 and 100 must be applied, as marked on the particular curves. The lighter-drawn curves refer to the emanation in one litre of ground-gas; the heavier curves to the emanation escaping in an hour from one square metre, i.e. the amount exhaled. PLATE IX. AINY. RAINYFINE; GROUND DRY. SETTLED. DRY. BATRA eens tI Aa Wak Wey aeo b n/a ¥ Paice TEC Sih rir SCIENT, PROC. R. DUBL. SOC., N.S., VOL. XIII. PLATE IX. Dry. RAIN. MUCH RAIN AT INTERVALS. 3 FiNe. FINE. RAINY. RAINY. FINE; GROUND STILLWET. GROUND DRYING. FINE AND GETTING MORE SETTLED. FINE; GROUND DRY. 480 lle alla ea I ea —- 7 T 460 a { [es E | 440 | i L in dL a ih | ic a r Z Se 400 4 AC Sad 380 + i ae Pte meee i —— 5] 340 i | T r ] Z = 320 | Bae | 300 7 | + a Za 280 +— +—--} 4 | BGO | IL T. C.D. scatete r | A 240 i 4 i : [ { 220 4. / Z IL | 200 sal | SETTLED. DRY. IL 180 Tcl: Z2 100\cms. a 160 < 140 120 io 100 Somerset 1 25 cms. Scale 7g Kilmainham 20x10. ; || IF Exhalation. Sgmerset (gras+).Scale a [Soe 2 ON 2) 22 Sz: 2/5 2 O27 OOS On 2 3 4 5 6 7 8 9 10 Il [2S S| Ge | OO eet) 2) 2 2 te SG 7 2 Ds () | | 2 3 4 5 (si 7/ ee N OS a 1. oy 10. 11. SCIENTIFIC PROCEEDINGS. — VOLUME XIII. A Seed-Bearine Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By ,T. JoHNnson, D.so., F.L.S. (Plates I.-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the , Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcz H. PrruysrincE, B.S¢., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wittram Brown, B.sc. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, sc.p., F.R.s. (April 20, 1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrtu1am J. Lyons, 8.4., a.R.c.sc. (Lond). (May 16,1911). 6d. . Radiant Matter. By Joun Jony, sc.p., r.z.s. (June 9, 1911.) 1s. . The Inheritance of Milk-Yield in Cattle. By Jamms Wiuson, M.a., B.SC. (June 12,1911.) 1s. . Is Archeopteris a Pteridosperm? By T. Josnson, v.sc., F.L.S. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archaopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jounson, p.sc., F.u.s. (Plates VII., VIII.) (June 28,1911.) Is. Award of the Boyle Medal to Prorsssorn Jonn Joty, m.a., so.D., r.R.S. (July, 1911.) Gd. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Joun Joy, sc.p., F.x.s., and Louis B. Smyru, B.a. (Plate IX.) (August, 1911.) 1s, Sf DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIRBS. ap A THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XII. (N.S.), No. 12. JANUARY, 1912. CONTRIBUTIONS TO OUR KNOWLEDGE OF THE FLORAS OF THE IRISH CARBONI- FEROUS ROCKS. Part 1—THE LOWER CARBONIFEROUS (CARBONIFEROUS LIMESTONE) FLORA OF THE BALLYCASTLE COALFIELD, Co. ANTRIM. BY E. A. NEWELL ARBER, M.A., F.L.S., F.G.S., TRINITY COLLEGE, CAMBRIDGE; UNIVERSITY DEMONSTRATOR IN PALMOBOTANY, [ COMMUNICATED BY PROFESSOR G, A. J. COLE, M.R.I.A., F.G.S. | (PLATES X-XIl.) [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. sonal WILLIAMS AND NORGATE, Le 14, HENRJETTA STREET, COVENT GARDEN, LONDON, WiC. JUN 94 1 1912. oe Price One Shilling. Roval Bublix Society. FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. Th copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. JoLy AND SmytuH—Amount of Radium Emanation in the Soil. 161 the effects of adding radioactive materials to soils upon which wheat was raised. These results are positive, but they leave some uncertainty as to the actual nature of the influences at work. Whether the exhalation of radioactive gases from the soil in a district influences the well-being of the higher organisms which inhabit it remains to be ascertained. The physiological and pathological influences of radioactive emanations are only beginning to be studied. Descriprion or Cuarr (Plate IX.). The numbers on the vertical axis are to be multiplied by 10. Where the quantities dealt with are too large, the further multipliers 10 and 100 must be applied, as marked on the particular curves. The lighter-drawn curves refer to the emanation in one litre of ground-gas; the heavier curves to the emanation escaping in an hour from one square metre, ie. the amount exhaled. SOIENT. PROO R.D.S., VOL, XIII., NO. XI. 28 [ent62 | XII. CONTRIBUTIONS TO OUR KNOWLEDGE OF THE FLORAS OF THE IRISH CARBONIFEROUS ROCKS. Parr I.—THe Lower CarsoniFrerous (CARBoNIFEROUS Limestone) FLora OF THE BALLYCASTLE CoALFIELD, Co. ANTRIM. By E. A. NEWELL ARBRER, M.A., F.LS., F.G.S., Trinity College, Cambridge ; University Demonstrator in Palzobotany. [COMMUNICATED BY PROFESSOR G. A. J. COLE, M.R.1.A., F.G.S.] (Pirates X-XII.) [Read December 19, 1911. Published January 20, 1912.] CONTENTS. TAGE PAGE 1. Introduction, : 2 5 6 - 162 4. The Age and Horizon of the Rocks, 173 9. Previous Records, é 6 0 . 164 5. Bibliography, . 5 A ‘ 5 |G 3. Description of the Specimens, é ~ 166 1. InTRODUCTION. Tr is a matter of regret that the study of the fossil plants of the Carboniferous rocks of Ireland has been so much neglected in the past in comparison with the progress made in our knowledge of the floras of the English and Scotch coal- fields, especially in regard to the vertical distribution of the component genera and species. Apparently but few Carboniferous plants have been recorded from Ireland; and, so far as the palzeobotanical evidence is concerned, the age and horizons of the coal-bearing strata found in different parts of that country remain unknown, except in one or two cases. In the present paper a description will be found of the flora of the Ballycastle coalfield in Co. Antrim, and it is hoped that, on future occasions, opportunities may arise for contributing further memoirs on the plant-remains of other Irish coalfields. ‘The specimens described here include those briefly recorded by the late Ww. H. Baily in 1888. They are now preserved in the collection of the Geological Survey of Ireland in the National Museum, Dublin. I am indebted to the Director of the Geological Survey of Ireland for the loan of these specimens for examination and description. At the suggestion of ArBER—The Flora of the Ballycastle Coalfield. 163 Professor Cole, and on behalf of the Geological Survey of Ireland, I also paid a short visit to Ballycastle, in June, 1911, to examine the coalfield, and to collect additional examples of its flora. The few specimens which I was able to obtain are also described here. They are now incorporated in the Irish Survey collection. It is not proposed to discuss here the geology of the Ballycastle coalfield. This subject has been treated of in detail by Berger and Conybeare (1816), Bryce (1887), Sir R. Griffith (1829), Professor Hull (1871 and 1877), and in the Survey Memoir on the district in question (1888).1_ Some of these papers will be again referred to in connexion with the fossil plants. The dominant lithological types of the Carboniferous sequence at Ballycastle are soft, coarse- grained, red, yellow, or white sandstones, and black shales. The subsidiary beds consist of thin seams of coal, with thin bands of argillaceous limestone and clay ironstone, both in the form of nodules and bands. The entire thickness is stated by Hull to exceed 1,200 feet. As is well known, this coalfield is intruded by a large laccolite of dolerite, which in places covers the Carboniferous rocks. A similar state of affairs is met with at Clee Hill in Shropshire. At the time of my visit to Ballycastle the opportunities for collecting fossil plants proved to be very unfavourable, though the rocks are well exposed on the coast in the cliffs on either side of Fair Head. I found that the black shales rarely contain any plant-remains, except the rhizophores and rootlets of Stigmaria, which are abundant. Some beds, however, are rich in mollusca. The soft, coarse-grained sandstones are, for the most part, unfossiliferous, though very occasionally they yield plant-remains. These consist chiefly of large, somewhat rough impressions or casts of stems or branches of Lepidodendron, or of its rhizophore, Stigmaria. At the time of my visit all the collieries and other workings for coal had been abandoned for some years, and thus one likely source of material was no longer available. On the western side of Fair Head, however, between Ballyvoy Pier and the Carrickmore Dyke, there are two or three sandstone quarries in the cliffs, containing a large amount of loose, discarded blocks. These are usually barren, though now and again they contain casts of the type above indicated. It was chiefly from these, and from the old waste heap of White Mine Colliery, closed a few years ago, that I was able to collect the few specimens described here. A search of the exposed area of Carboniferous rocks on the eastern side of Fair Head, at Fall Point, proved fruitless so far as fossil - plants were concerned. I also endeavoured to locate the spot on the western ‘ For references to these papers, see the Bibliography on p. 176. 232 164 Scientific Proceedings, Royal Dublin Society. side of Fair Head from which Baily obtained the fern-like fronds described here. These are perhaps the most interesting plants known from this coal- field. His record of the locality is not, however, very explicit, and, even if I located the beds, I failed to find any trace of similar specimens. 2. Previous Recorps. The earlier accounts of the geology of the Ballycastle coalfield do not contain any records of fossil plants having been found, with the exception of the mention of “ fucoids and ferns from Bunatraher, Ballycastle,’ by Griffith’ in 1862. Before 1871, however, some plant-remains had been collected, chiefly by Mr. W. H. Baily and Mr. A. M‘Henry, of the Irish Geological Survey, and these were described in an appendix to Professor Hull’s? paper, published in that year. The following species were then recorded by Baily :— Baity’s Names. Moprrn Namgs. Sigillaria reniformis (Brongn.) = Sigillaria reniformis (Brongn.) Stigmaria ficoides (Brongn.) = Stigmaria ficoides (Sternb.) 3 5 var. undulata = » var. undulata (Goepp.) Aspidiaria quadrangularis (Presl) = epitodende on sp. (decorticated state). Lepidostrobus variabilis (Lindley) = Lepidostrobus variabilis, L. & H. Sagenaria dichotoma (Sternberg) = Lepidodendron dichotomum, Sternb. Sagenaria aculeatum (Sternberg) = Lepidodendron aculeatum, Sternb. Sagenaria Veltheimiana (Sternberg) = Lepidodendron Veltheimi, Sternb. Sagenaria rimosa (Presl) = Lepidodendron rimosum, Sternb. 1 have not seen these specimens, but, in the light of the other plants from this coalfield which I have examined, I have very little doubt that some of them were wrongly determined. Anyone glancing through this list would imagine that the flora was of Upper Carboniferous age, for all the species of Lepidodendron indicated, except Lepidodendron Veltheimi, Sternb., are confined to the rocks of that period; and further, Sigil/aria is very rare in the Lower Carboniferous sequence. However, the plants which I have examined from Ballycastle indicate a flora of Lower Carboniferous age, and I suspect that, as regards the species, some fossils have been confused with those which are abundant in the Coal Measures, which are not perhaps, at first sight, very dissimilar. It must also be remembered that at the time this list was drawn up, very little was known on the subject of the Lower Carboniferous flora, 1 Griffith (1862), p. 54. * Hull (1871), p. 270. Arper— The Flora of the Ballycastle Coalfield. 165 and its species were for the most part difficult and ill-defined. Thus I suspect that the record of Stgillaria reniformis, Brongn., from this coalfield is really founded on a highly decorticated Lepidodendroid stem of the type of LL. Veltheim?, Sternb., which in certain stages of decortication has been the cause of many misleading attributions in the past. I am also inclined to believe that most of the species, referred in the above list to the genera Aspidiaria and Sagenaria, represent one state or other of Lepidodendron Veltheimi, Sternb., or L. Volkmannianum, Sternb., or perhaps L. hodeanum, Sternb. In 1877, Professor Hull' mentioned the occurrence of Sagenaria imbricata and Sigillaria in the “ Upper beds at Ballycastle.”’ The former name now stands for a cast of the outer surface of the wood of a Lepido- dendron; andthe Stgillaria here mentioned is no doubt similar to that already discussed. In the Survey Memoir on the district,? published in 1888, Baily enumerates the following plants from Ballycastle :—- Batty’s Names. ReviseD NoMENCLATURE. Sagenaria dichotomelegans = Lepidodendron lycopodioides, Sternb. Sphenopteris flabellata, u. sp. - ee A ed i Sigillaria, sp. (leaves). Sigillaria (Stigmaria ficoides), rootlets. I have had, I believe, an opportunity of seeing most of these specimens. Those referred to Sagenaria dichotomelegans (= L. lycopodioides Sternb.) are partly referable to Lepidodendron Veltheimi, Sternb., and to L. ¢/. L. Rhodeanum, Sternb. They are, I believe, the specimens figured here on Plate XII, figs. 12 and 165. The fern-like fronds, determined by Baily as a new species, Sphenopteris flabellata, Baily, are perhaps the most interesting plants known from this coal- field. They are, however, referable to two species. The original of Baily’s fig. 9, on p. 47, is undoubtedly a small portion of a frond of Adiantites antiquus (Htt.), first described by Httingshausen in 1865. The plant shown on figs. 9a and 9c of the same page has apparently not been described, either before or since 1888; and for it the name Sphenopteris flabellata, Baily, may be appropriately reserved. It is apparently still unknown elsewhere. This completes the list of previous records; and we will now pass on to the description of the plants from the Ballycastle coalfield which I have had an opportunity of examining. 1 Hull, (1877) p. 625. 2 Symes, ete., (1888) p. 43. 166 Scientific Proceedings, Royal Dublin Society. 3. DescripTION OF THE SPECIMENS. Archeocalamites, Stur. Archeocalamites, sp. Locality.—Small quarry in sandstone, 30 feet below the top of cliff, 100 yards east of Ballyvoy Pier, Ballycastle coalfield, Co. Antrim. Description of the Specimens.—Two badly preserved casts in sandstone were collected by the author in 1911. The best-preserved shows faint indications of two nodes and of ridged internodes, and is no doubt a pith-cast referable to Archeocalamites, though the preservation is too poor to admit of specific determination. Adiantites, Goeppert. Adiantites antiquus (Kttingshausen). Plate XI, figs. 8 and 9. 1865. Adiantum antiquum, . Ettingshausen, Denkschr. K. Acad. Wissen. Wien, vol. xxv., p. 22, fig. 7, pl. vii, fig. 1. 1874. Aneimites adiantoides,. Schimper, Traité Paléont. végét., vol. ili., p- 490. 1875. IICHBIEION SXOXCS, INGOs, WOME, AONE IPLAC ACM. FOSSIL PLANTS FROM THE BALLYCASTLE COALFIELD. de 10. ilil, 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Ivish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. JoHNson, D.S0., F.L.S. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcze H. Prruysrines, B.Sc., PH.D. (March, 1911.) 1s. : . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witu1am Brown, B.so. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, so.p., F.R.s. (April 20, 1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wriu1am J. Lyons, B.a., a.R.0.sc. (LonD). (May 16,1911). 6d. . Radiant Matter. By Joun Jouy, s0.D., F.R.S. (June 9,1911.) 1s. . The Inheritance of Milk-Yield in Cattle. By James Wusson, M.a., B.SC. (June 12, 1911.) 1s. . Is Archeopteris a Pteridosperm? By T. Jounson, v.so., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jouwson, p.sc., F.u.s. (Plates VII., VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Proressor Joun Joy, M.a., SO.D., F.R.S. (July, 1911.) 6d. On the Amount of Radium Hmanation in the Soil and its Escape into the Atmosphere. By Joun Jouy, “sc.p., F.x.s., and Lovis B. Smyrs, B.a. (Plate IX.) (August, 1911.) 1s, Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newent Arper, M.A, F.LS., F.G.S. (January, 1912.) 1s. DUBLIN: PRINTED AT [HE UNIVERSUCY PRLSS BY PONSONBY AL GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 13. JANUARY, 1912. FORBESIA CANOELLATA, gen. et sp. nov. (SPHENOPTERIS, sp., Baily). BY J OENSON) Se.) HES: PROFESSOR OF BOTANY IN THE ROYAL COLLEGE OF SCIENCE FOR IRELAND, DUBLIN. (PLATES XIII. and XIV.) [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN : PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. Price One Shilling. 0 nal Muse Roval Dublix Society, FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. ee 9 XIII. FORBESIA CANCELLATA, gen. et sp. nov. (SPHENOPTERIS, sp., Baily.) By T. JOHNSON, DSc., F.LS., Professor of Botany in the Royal College of Science for Ireland, Dublin. (Puates XIII. anp XIV.) [Read Novemper 28, 1911. Published January 19, 1912.] In the course of examination of the different specimens of Sphenopteris in the Museum Collections I was struck by the three or four small slabs of plant-impressions provisionally named by Baily (1) “ Sphenopteris, sp.,” and described by him (p. 19, fig. 1) in the “ Explanation of Sheets 187, 195, and 196” of the Geological Survey of Ireland.!’ The specimens were obtained from the Lower Carboniferous strata, near Bandon, Oo. Cork. Sphenopteris is not a generic name in the modern sense, but a form- name introduced by Brongniart (2) in 1822 for that sterile division of Schlotheim’s Filicites (a term applied to Paleozoic fossil-ferns in general) which showed (1) a differentiation into stem and leaf, (2) a segmentation of the leaf, with ultimate wedge-shaped lobes, or segments, and (8) a clearly marked forked or pinnate venation. The venation normally consists of a central or median vein running through the secondary rachis, with simple or branched veinlets passing out into the pinnule segments. Baily’s plant shows the differentiation into axis and leaf with cuneate segments very character- istically, but there is no sign in it of the venation to be found in an ordinary Sphenopteris. If it was a vascular plant, it had not yet developed a definite vascular system ; i.e., it was a vascular cryptogam without vascular bundles. Its organisation was thus lower in type than that yet seen in any Pteridophyte, living or extinct. It brings us, then, if my interpretation is right, nearer to that ancestral form from which the Filicines arose, and to this extent helps 1JT am indebted to Professor G. A. J. Cole for the permission to examine the specimens of Sphenopteris preserved in the collections of the Geological Survey of Ireland, and housed jn the National Museum, Dublin. SOIENT. PROC. R.D.S., VOL. XIII., NO. XIII, 2D 178 Scientific Proceedings, Royal Dublin Society. to fill in the great gap between ferns and the lower forms. The general character of the plant, which I propose to call Forbesia cancellata in honour of Edward Forbes, the discoverer of Archwopteris hibernica, is indicated in Pl. XIII, fig. 1. The axis is dichotomously branched several times, and gives off at long intervals leaves which show a rachis, itself dichotomously divided. The laminated part of the leaf is also dichotomously divided, and ends in obtuse, simple, or bilobed wedge-shaped segments (fig. 1). Dichotomy of axis and frond is thus a pronounced feature. Though the terms “axis” and “frond” are used, there is really no means of distinguishing one from the other structurally. Both axis and frond are honeycombed structures. They consist of numerous air-chambers partitioned off from one another by septa, which appear strengthened by a band of sclerotic tissue. In the specimens some of the air-chambers are free from mineral deposit, and under magnification | ————__ | by ny M D \ : | | SS Seep SS —— es ——————— 3 fi mene 529 ood 2 E —S | — | Fig. 1. Fre. 22 show a surface marked by fine longitudinal lines with connecting cross-lines. Tn each of the microscopic spaces so formed a dot-like depression is observable (fig. 2). In other words, the surface of the air-chamber is lined by parenchy- matous cells whose cavities are represented by the minute central pits. By magnification what appears to be a band of sclerotic tissue can also be seen running through the septum between the adjoining air-chambers. Just beneath the surface of the axis, on either side, there is observable in some cases (Pl. XIV, fig. 5) a pronounced vertical strand which is connected with the more or less rectangular reticulum formed in the septa of the air chambers in the axis. This strand curves out into the rachis of the frond. It appears to be a strengthening strand. The frond shows, as mentioned, exactly the same structure as the axis. It differs from it in position (being a lateral outgrowth from it), and in the lamination or flattening out of JoHNnson—FPorbesia Cancellata. 179 its branchings into wedge-shaped foliage segments. Neither in axis nor frond is there anything that can be described as vascular tissue, though surface anatomy alone is available in forming this opinion. At one point on the axis (Pl. XIII, fig. 3), close to and below a bifurcation, there is a small group of three or four ovate or ellipsoidal bodies. One of these seems clearly attached to the under side of the fork. Do these represent a group of caulicolous sporangia or reproductive bodies, comparable to those described by Nathorst (3) for Cephalopteris (Cephalotheca) from the Upper Devonian beds of Bear Island? ‘The group of bodies, whatever its nature, occupies the same relative position as that of the tuft of sporangia described in Cephalopteris, though the two genera are not alike structurally. On the slabs are scraps, possibly of roots, but almost too indefinite for even mere mention. The only plant at all suggestive of Morbesia cancellata I can find is one described by Unger (4) from the Upper Devonian rocks of Central Europe, contemporaneous with those in south and south-west of Ireland, yielding Sphenopteris Hookeri, Baily, Archeopteris hibernica, &c. Sphenopteris devonica, the plant in question (Pl. XIV, fig. 2), was found at Saalfeld in the Cypridinenschiefer. Its axis shows a sculpturing not unlike that of Forbesia, though it is ascribed by Unger to adjoining surface tubercles or papilla. The fronds are very similar in position and mode of segmenta- tion to those of Forbesia, but are less remote from one another, and occur alternately on the axis. They show, however, a forking venation such as occurs in Sphenopteris generally. In his introductory remarks on the plants of the Cypridinenschiefer Unger states that Richter collected all the plants and sent him drawings only of the “ impressions,” so that Unger’s descriptions and illustrations are based simply on Richter’s drawings. Unger expressly states that he cannot describe the venation of Sphenopteris devonica in detail, owing to non-inspection of the specimen itself. I strongly suspect that an inspection of the original specimen of S. devonica would show a close approximation to, if not identity with, Forbesia. Heer (8) called attention in 1871 to the close affinity of the fossil plants of Bear Island, situated at 74° N., to those of the Yellow Sandstone and Lower Carboniferous strata of south-west Ireland. In the course of the comparison between the floras he expressed the opinion that our plant (Sphenopteris, sp., Baily) is scarcely distinct from Sphenopteris Hookeri, Baily, Nathorst, writing in 1902 on the fossil plants of Bear Island, thinks that Sphenopteris, sp., Baily, is not improbably identical with his Sphenopteridium Keilhaui. He rejects the identification of our plant with Sphenopteris Hooker, on the ground that S. Hookeri possesses distinct venation. (Here and in 2p2 180 Scientific Proceedings, Royal Dublin Society. several other parts of his invaluable work on the Bear Island Flora, Nathorst, as I learnt by correspondence, uses the word ‘“‘ Mittelader ” when intending to use “ Aderung.”) Sphenopteris Hookeri has a well-marked venation, with no sign of a midrib, and is distinct from our plant, in which no venation is observable. Through the kindness of Professor Nathorst I have received a specimen of his very rare Sphenopteridium Ieilhaui, and have thus been able to compare it with Forbesia. I can see nothing in S. Keilhawi of the cancellous character of Forbesia, wnich has too a more pronounced dichotomous character than S. Keilhaui, with its keeled axis, indicative of vascular tissue. In both species, as well as in Cephalopteris mirabilis, Nath., Rhacophyton con- drusorum, Crépin, S. Lebedewi, Schmalhausen, S. flaccida, Crépin, and similar early Paleozoic forms, the leaf-lamina is but little pronounced, and looks as if it were in the first stages of emergence by the flattening out of the ultimate ramification of a branching ribbon-like axial system. Forbesia is thus a veinless plant, though found, so far as Ireland is concerned, in a later formation than that which gives us the vascular Sphenopteris Hookert. Sooner or later it will, I think, be recorded for the Devonian rocks too. It must be remembered that we are now re-examining, under the inspiration of recent paleobotanical discoveries, material collected in 1851 and left unexamined, owing to insufficiency of staff, until 1864 (by which time much of it had been lost or dispersed, says Jukes, (op. cit.). The early Palzeozoic flora of Ireland is one of the most interesting and illuminating in the world, and urgently needs further investigation. The sclerotic framework mentioned is not a surprising feature. Though the leaves were small, they needed support, and this the sclerotic bands would give, just asin Heterangium Grievii, with its small leaf-segments, the sclerotic plates supplement the vascular tissue. The chambered tissue suggests a marshy or semi-aquatic habit for Forbesia. More interesting still than the absence of vascular bundles is the lack of structural differentiation of axis and frond. Except for the flattening out of the leaf-segments, there is no marked difference between axis and frond. - | interpret this as indicating that Forbesia represents a primitive form in which the plant-body is nearer than any yet unearthed to the hypothetical ancestors of the Pteridophyta, i.e., to a form, comparable with the ‘“ Prohepatic” of Lignier (5), in which the plant-body is still more or less in the thallus state. Such a form shows no differentiation into stem and leaf and no vascular tissue, but is dichotomously divided. In its next stage it begins to erect itself and to give off flattening branches of the thallus which will gradually become leaves. ‘he line of connexion of the Pteridophyta with the non-vascular cryptogams cannot, I think, be sought through theMusci, which bear a relation to the Pteridophyta Jounson—Forbesia Cancelluta. 181 comparable to that of birds to mammals. Zoologists see the line of connexion of mammals with the Sauropsida through its lowest group—the Lacertilia—and not through the most highly specialized, the Aves. Dichotomous branching as a primitive character was not so much appreciated fifty years ago as it is now. Several of Baily’s figures (1), e.g. fig. 1 6 and d, need redrawing, that some omitted indications of dichotomy may be included. More stress may now be laid on the phylogenetic value of the dichotomously veined and branched cotyledon of ferns. At the same time, the danger of attaching undue importance to external form must not be overlooked. ‘The fern cotyledon is constant in character, both in its dichotomous lobation and associated dichotomous venation. Such marked, constant features must have antecedents. There is no sign of them in any sporophyte of moss or Liverwort; and it seems more natural to look for ancestral forms in the gametophyte generation of a Bryophyte through such a connecting form as Forbesia, and not to pass over the Muscinex altogether. Potonié (6), e.g., seeks for a connecting link in Fucus-like Alge, and treats the fern prothallus as an intercalated, secondary, aquatic adaptation. Dictyota dichotoma gives a hint of the line along which specialization might take place. In it we have an alternation of generations in which the dichotomously divided evascular aquatic thallus is externally the same in both generations. One generation is, however, asexual, and bears tetraspores only; the other bears sexual organs only. The two alternate, and yet are alike in appearance, in keeping with their aquatic habitat. It would take an enormous time to evolve a fern-sporophyte, as hypotheticated by Bower (7), from the simplest sporogonium of a Bryophyte by sterilization of sporogenous tissue and by appendicular expansions as leaves from a slowly erecting radial axis. It seems simpler to accept the view that the alternation has arisen by a change from an aquatic to an aérial mode of life, with a gradual production of vascular tissue as a necessary accompaniment of the adoption of an aérial mode of life. ‘The converse process is well seen in aquatic flowering plants which lose their xylem, and show a reduced vascular tissue. The Hepatice show, in their own gametophyte, the change from a thalloid to foliose habit, and that which we have before us perpetuated in the Liverwort, may have occurred in the ancestral Pteridophytes. D.H. Campbell (10) has shown by a consideration of the geographical distribution of Muscinez that they are an ancient group, and their infrequency in the earlier rocks is explicable by the perishable nature of their tissues. (Lindley, e.g., found no trace of the six mosses which he left for two years, with flowering and other plants, in a tank of water. Very muddy water would have been a test more in keeping with the couditions of fossilization). The morphological value altached to the 182 Scientific Proceedings, Royal Dublin Society. reduction of the chromosomes in nuclear division seems to me to have been considerably lessened by the discovery of its universality of occurrence in the different forms of life, from Algee and Fungi to Spermatophytes. The reduction is a physiological necessity. Had the water not become dry land, the alternation of generations in ferns might have occurred as it does in Dictyota to-day, but the fern’s ancestors would have remained in the thallus stage in both generations. Rejecting Potonié’s view that the prothallus is an interealated secondary body, and accepting the view that it is a true gametophyte, sufficient stress has not been laid, I think, on its reduced character. Comparison has been confined too much to what is obvious—the gametophyte of existing groups. It is easy to arrange the vascular plants in an ascending series in which the gametophyte becomes less and less differentiated and independent until its extent, not to say existence, in the highest spermatophyte is a subject of dis- cussion. In the same ascending series the archegonia become gradually simpler, more embedded and protected, and finally reduced to the essential egg-cell only. The series should be continued downwards from the fern with the thalloid, rather than the foliose forms of the Muscines as guides to the line of descent. ‘The fern prothallus with its emargination depression would become dichotomously lobed, and its archegonia would become more compli- cated and would be stalked or project as in Muscineze. We must assume that at one time the fern-sporophyte was evascular, and the now stable cotyledon seems to give a hint of an ancestor with a dichotomous bifurcation of its parts leading downwards to a stage in which the present marked difference between fern gametophyte and sporophyte, except for mode of reproduction, is lost. The adaptation of an aquatic well-developed thallus to a drier aérial environ- ment offers less difficulty of explanation and accomplishment than the differentiation, ab initio from a zygote, of a sporophyte such as a fern possesses. Forbesia cancellata would fit in as an intermediate stage in the differentia- tion of the sporophyte when the plant-body was evascular and dichotomously divided, and when the only distinctions between axis and frond were their relative position and the lamination of the frond. Forbesia was “ finding its feet,” and needed, to stand erect, the mechanical support the sclerotic framework provided. Jounson— Forbesia Cancellata. 183 BIBLIOGRAPHY. . Memoirs of the Geological Survey of Ireland. Explanation of Sheets 187, &., 1864. W. H. Baily: Palzontological Remarks, p. 19, fig. 1 a-d. . Bronentart, A.: Histoire des Végétaux Fossiles. Paris, 1837. . Natuorst, A. G.: Zur oberdevonischen Flora der Baren-Insel, mit 14 Tafeln. Vet.-Akad. Handl., vol. xxxvi, Stockholm, 1902. . Unerr, F. u. Richter, R.: Beitrag zur Paleontologie des Thiiringer Waldes. Denkschr. d. Kais. Akad., Wien, Bd. xi, 1856. . Lienrer, O.: Equisétales et Sphénophyllales. Leur origine filicinéenne commune. (Bull. Soc. Linn. Normandie, Sér. 5, vol. vii. Caen, 1903. . Poronti: Lehrb. der Pflanzen-Paleontologie. Berlin, 1899. . Bower, F. O.: The Origin of a Land Flora, 1908. . Herr, O.: Kohlen-Flora d. Baren-Insel. Kongl. Svenska Vetensk. Akad. Handl., Bd.ix. Stockholm, 1871. . Lindley and Hutton: Fossil Flora of Great Britain, vol. iii, p. 5, 1837. 10. Campbell, D. H.: On the Distribution of the Hepatic and its Significance. (The New Phytologist, vi, 1907.) a Picts TEs ; eens) hee , 1s Ly as Sty ahi EXPLANATION OF PLATE XIII. PLATE XIII. ForBESIA CANCELLATA. Fig. 1. General appearance of Forbesia cancellata, showing three bifurcations. A fourth obscured in the stone occurs half-way along the left prong of main fork. Compare Baily’s fig. 1a of Sphenopteris, sp. Fig. 2. The lowest bifurcation of fig. 1 slightly magnified. Fig. 8. Portion of fig. 1, in the region of the upper, right bifurcation, still more highly magnified to show small group of sporangium-like bodies to the left of fork, comparable in position with the mop-like group of sporangia in Cephalopteris mirabilis, N. PEATE: Si XIII. NOW, SCIENT. PROC. R. DUBEIN SOC., N:S.. EXPLANATION OF PLATE XIV. PLATE XIY. Fig. 1. Photograph of dichotomous frond or pinna—right half only exposed. The cancellous character of the rachis and frond are observable. x 3. Fig. 2. Photograph of drawing by Unger of Sphenopteris devonica, for comparison with fig. 4. Fig. 3, Photograph of the broadest piece of axis seen. Nearly x 2. Fig. 4, Bifurcating portion of fig 3. x 3. Fig. 5. Portion of axis showing sub-marginal longitudinal strie and the connected reticulum. The finer longitudinal striation is observable with alens. See text-figure 2. Fig. 6. Two overlapping pieces of Forbesia. Dichotomy of frond seen in lower specimen, partly dissected out. I am indebted to Mr. W. N. Allen for photographs of Plate XIII and of Plate XIV, figs. 3, 4, 5. XIV. E PLAT IENT.:PROC. R. DUBLIN SOCG., N.S., VOL. XIII. 7 / SES ae bel bo o SCIENTIFIC PROCEEDINGS. VOLUME XIII. . A Seed-Bearine Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamiwm, Williamson). By T. JoHnson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. . Considerations and Hixperiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorez H. Prruyerives, B.Sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witu1am Brown, B.so. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, so.p., F.R.s. (April 20, 1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wii J. Lyons, B.a., a.R.c.sc. (LonpD.). (May 16,1911). 6d. . Radiant Matter. By Joun Jony, sc.p., F.R.s. (June 9, 1911.) 1s. 7, The Inheritance of Milk-Yield in Cattle. By Jamms Wuxson, M.A., B.SC. 10. 11. 12. 13. 14. (June 12, 1911.) 1s. . Is Archopteris a Pteridosperm? By T. Jouwnson, pD.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jouson, p.sc.,F.u.s. (Plates VII., VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Proressor Joun JoLy, M.A., SC.D., F.R.S. (July, 1911.) 6d. On the Amount of Radium Hmanation in the Soil and its Hscape into the Atmosphere. By Joun Joy, sc.p., F.x.s., and Lours B. Smyru, B.a. (Plate IX.) (August, 1911.) 1s. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newent Arper, M.A, F.LS., F.G.S. (January, 1912.) 1s. Forbesia cancellata, gen. et. sp. nov. (Sphenopteris, sp., Baily). By T. Jounson, D.sc., F..s. (Plates XIII. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By James W1Ls0N, M.A., B.SC. (January, 1912.) 1s. DUBLIN: PRINTED AT fHE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 14. | JANUARY, 1912. THE INHERITANCE OF THE DUN COAT-COLOUR IN HORSES. BY JAMES WILSON, M.A., B.Sc. PROFESSOR OF AGRICULTURE IN THE ROYAL COLLEGE OF SCIENCE, DUBLIN. [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY LEINSTER HOUSE, DUBLIN. sonia WILLIAMS AND NORGATE, f 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. \. 1912. fi ZX Price One Shilling. Roval Dublin Soctety, AIR ARR RAT FOUNDED, A.D. 1731. INCORPORATED, 1749. OOS EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested +o forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. e The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. Jounson — Forbesia Cancellata. 183 BIsiioGRAPHY. . Memoirs of the Geological Survey of Ireland. Explanation of Sheets 187, &., 1864. W. H. Baily: Paleontological Remarks, p. 19, fig. 1 a-d. . Broneantart, A.: Histoire des Végétaux Fossiles. Paris, 1837. . Narnorst, A. G.: Zur oberdevonischen Flora der Baren-Insel, mit 14 Tafeln. Vet.-Akad. Handl., vol. xxxvi, Stockholm, 1902. . Uncer, F. u. Richter, R.: Beitrag zur Paleeontologie des Thiringer Waldes. Denkschr. d. Kais. Akad., Wien, Bd. xi, 1856. . Lienter, O.: Hquisétales et Sphénophyllales. Leur origine filicinéenne commune. (Bull. Soc. Linn. Normandie, Sér. 5, vol. vii. Caen, 1903. . Roront: Lehrb. der Pflanzen-Paleontologie. Berlin, 1899. . Bower, F. O.: The Origin of a Land Flora, 1908. . Herr, O.: Kohlen-Flora d. Baren-Insel. Kongl. Svenska Vetensk. Akad. Handl., Bd.ix. Stockholm, 1871. . Lindley and Hutton: Fossil Flora of Great Britain, vol. iii, p. 5, 1837. 10. Campbell, D. H.: On the Distribution of the Hepatice and its Significance. (‘The New Phytologist, vi, 1907.) SCIENT, PROG. R.D.S., VOL. XIL., NO. XIII, 25 XIV. THE INHERITANCE OF THE DUN COAT-COLOUR IN HORSES. By JAMES WILSON, M.A., B.Sc, Professor of Agriculture in the Royal College of Science, Dublin. [Read December 19, 1911. Published January 19, 1912.] In a previous paper on ‘‘The Inheritance of Coat-Colour in Horses” * it was shown, from the data then in hand, that the colours fit into each other like a nest of Chinese boxes: chestnut being innermost or recessive to all others; then coming, in succession, black, bay, brown, dun, and finally grey and roan. The following diagram will make the position of each colour clear :— BLACK. CHESTNUT, It was pointed out that the relative positions of bay and brown were not absolutely clear, and that, while grey and roan were each dominant to all the other colours, there was no evidence to indicate their relative positions. Hach 1 The Inheritance of Coat-Colour in Horses,’’ Scient. Proc. Royal Dublin Society, 1910. Witson— The Inheritance of the Dun Coat-Colour in Horses. 185 was a distinct variety ; but the behaviour of either towards the other was not disclosed. At the same time the data concerning dun were very few—only twenty- three cases being quoted, in addition to information gathered on Clare Tsland—and its position was only suggested in a foot-note. Since the pub- lication of the previous paper, search has been made for further dun data, which it is proposed to bring together in the present paper. The reason for searching specially for dun data is that, for many years, this colour has been looked upon as a reversion, liable to appear among all kinds of horses, but especially among cross-breds, no matter what the colours of the parents, and because this view has been closely connected with the subject of inheritance. It is also desirable to confirm the previous finding. It would be difficult to say when stock-breeders began to look upon animals unlike their parents but like some remote ancestor as reversions; but, if the matter was not considered previously, it was brought into notice by the publication, in 1821, of Lord Morton’s quagga experiments. Lord Morton, as stated in his communication to the Royal Society, read in November, 1820, wished to experiment in domesticating the quagga, and “endeavoured to procure some individuals of that species.” He “ obtained a male; but being disappointed of a female,” he “tried to breed from the male quagga and a young chestnut mare of seven-eighths Arabian blood, and which had never been bred from: the result was the production of a female hybrid, now five years old, and bearing, both in her form and in her colour, very decided indications of her mixed origin.” Lord Morton pro- ceeds :—‘‘ I subsequently parted with the seven-eighths Arabian mare to Sir Gore Ouseley, who has bred from her by a very fine black Arabian horse. I yesterday morning examined the produce, namely, a two-year-old filly, and a year-old colt. ‘They have the character of the Arabian breed as decidedly as can be expected, where fifteen-sixteenths of the blood are Arabian; and they are fine specimens of that breed; but both in their colour, and in the hair of their manes, they have a striking resemblance to the quagga. Their colour is bay, marked more or less like the quagga in a darker tint. Both are distinguished by the dark line along the ridge of the back, the dark stripes across the fore-hand, and the dark bars across the back part of the legs. ‘he stripes across the fore-hand of the colt are con- fined to the withers, and to the part of the neck next to them; those on the - filly cover nearly the whole of the neck and the back, as far as the flanks. The colour of her coat on the neck adjoining the mane is pale, and approach- ing to dun, rendering the stripes there more conspicuous than those on the 2E2 186 Scientific Proceedings, Royal Dublin Society. colt. The same pale tint appears in a less degree on the rump; and in this circumstance of the dun tint also she resembles the quagga.”” At the time this was held by Lord Morton and others to have been a case of “infection of the germ” or telegony, as we now call it; but, as early as 1839, Dr. W. Macdonald, of Edinburgh, in a paper also read before the Royal Society, doubted this explanation, and suggested that the chestnut mare’s foals were reversions. He pointed out that “similar markings are very commonly met with on the Hel-back dun ponies of Scotland”’; and, as the chestnut mare “‘ was not pure, she may have inherited the tendency to those peculiar markings.” He observed further that the ‘“ cross-bar markings on the legs [of the chestnut mare’s foals] are not found in the quagga, but only in the zebra, which is a species quite distinct from the quagga ”’—a fact which he considers as completely overturning the reasoning by which the conclu- sions stated in Lord Morton’s paper were deduced. The facts, he thinks, admit of a more natural explanation, and one more consistent with the known physiological laws of development, by supposing the stain in the purity of the mare’s Arab blood to have arisen from the circumstance of an early progenitor of the mare having belonged to the eel-backed dun variety, the peculiarities of which appeared in a later generation.’ Hamilton Smith, whose ‘‘ Natural History of Horses’ was published as one of Jardine’s “ Naturalist’s Library’? in 1841, and whose knowledge of the history and distribution of the horse was beyond that of such contemporaries as Youatt and Low, thought Macdonald’s “ conjecture . . far-fetched.’’® Yet he thought there was a possibility of the colours reverting. He believed that horses were descended from five original stocks, viz., the bay, the white or grey, the black, the dun or tan, and the tangum, piebald or skewbald, which had been mingled together ; that, asa result of this mingling, horses were now of many colours; but that all tended to return to the original five. His statement is worth quoting :—“ From the different colours of the original stocks, horses are clothed in a greater diversity of liveries than any other animals, cattle and dogs not excepted ; they are a natural consequence of interminable crossings of the five great stipes already mentioned, producing combinations which have caused French and Spanish writers to enumerate above sixty: the piebald and dappled find only their counterparts in the forms and shades of colour in some species of seals, and it is there also we find the light blue greys with brown spots, of which we have examples in the New Forest and in Spain: yet excepting the five primitive, all the rest have ? 1 Philosophical Transactions for 1821, p. 20. ? Proc. Royal Society, iv., p. 164. 3 «Natural History of Horses,” p. 73. Witson— The Inheritance of the Dun Coat-Colour in Horses. 187 a tendency to return to them, and sometimes it would seem capriciously to resume the bay, dun, grey, or black.”! Smith said also that, while the five original stirpes were all represented among tame horses, “ the dun is typical of the generality of the real wild horses, still extant in Asia, and the semi- domesticated, both there and in Hastern Hurope. Besides the general form, the smaller square head, great length of mane, tendency to black limbs, it is known by the black streak along the spine, sometimes, though very rarely, erossed by a second of a fainter colour on the shoulders, and often marked by black streaks on the hocks and upper arms.’” It was left to Darwin to set aside all other stirpes, and, after first suggesting the descent of all kinds of horses from a striped race, eventually to suggest them as tracing back to a race that was both striped and dun. In “The Origin of Species”? (1859) he rejected Hamilton Smith’s theory “that the several breeds of the horse are descended from several aboriginal species,” and went on to say that, although he had “collected cases of leg and shoulder stripes in horses of very different breeds in various countries, . . .” yet “in all parts of the world these stripes occur far oftenest in duns and mouse-duns.”’ He found them also in mules and in other equine crosses, and mentioned the striped foals of Lord Morton’s chestnut mare. Then, seeing the appearance of such stripes to be parallel to the occasional appearance of “slaty blue birds with two black bars on the wings,’ and so on, among pigeons, he summed up thus :—‘“ For myself, I venture confidently to look back thousands on thousands of generations, and I see an animal striped like a zebra, but perhaps otherwise very differently constructed, the common parent of our domestic horse (whether or not it be descended from one or more wild stocks), of the ass, the hemionus, quagga, and zebra.’’* But, in “The Variations of Animals and Plants under Domestication’’ (1868), the dun colour is added to the stripes as a characteristic of the ancestral horse, although the new evidence in support of the addition is not very great. ‘The second chapter of this book is devoted to horses, and consists mainly in an extension of the argument contained in “Ihe Origin of Species.” It is stated that duns are barred and striped more frequently than other species—but not that duns only and that all duns are barred—that, in places, duns are not considered pure-bred unless they are striped; and, from the fact that wild and semi-wild horses in Europe and Asia and feral horses in America‘ are, many of them, dun, it is inferred that dun is obviously the colour of wild 1 « Natural History of Horses,’’ p. 199. 2 Thid., p. 274. 3‘ Origin of Species,” 1897 ed., pp. 117 to 122. 4 Ridgeway has shown that Cortes took dun horses with him to Mexico: ‘‘ Origin and Influence of the Thoroughbred Horse,” p. 267. ‘ 188 Scientific Proceedings, Royal Dublin Society. horses. A number of dun horses have been examined and the parentage of some of them looked into, but only three are cited, none of whose parents is dun. Darwin then sums up:—‘‘ From reasons which will appear in the chapter on Reversion I have endeavoured, but with poor success, to discover whether duns, which are so much oftener striped than other coloured horses, are ever produced from the crossing of two horses, neither of which are duns. Most persons to whom I have appealed believe that one parent must be a dun; and it is generally asserted that, when this is the case, the dun-colour and the stripes are strongly inherited. One case has fallen under my own observation of a foal from a black mare by a bay horse, which when fully grown, was a dark fallow-dun and had a narrow but plain spinal stripe. Hofacker gives two instances of mouse-duns (Mausrapp) being produced from two parents of different colours and neither duns.”? On these grounds Darwin adds the dun colour to the stripes of the ancestral horse. But he says that the case for the descent of the horse from a dun and striped ancestor is less clear than that of the pigeon from a blue and barred ancestor :—‘‘ The appearance of the stripes on the various breeds of the horse when of a dun-colour does not afford nearly such good evidence of their descent from a single primitive stock as in the case of the pigeon. . . Nevertheless the similarity in the most distinct breeds in their general range of colour, in their dappling, and in the occasional appearance, especially in duns, of leg-stripes, and of double or triple shoulder-stripes, taken together, indicate the probability of the descent of all the existing races from a single, dun-coloured, more or less striped, primitive stock, to which our horses still occasionally revert.’” Curiously enough, in the argument leading to the statement just quoted, there is no mention of Lord Morton’s experiment, from which it might be inferred that the second and third foals’ from the chestnut mare carried weight in Darwin’s mind no longer. But this is scarcely possible; for they are cited in a subsequent chapter* in language which suggests that Darwin took them to be more dun than Lord Morton did. Lord Morton spoke of the filly and the colt generally as both resembling the quagga in their colour, and particularly, of the filly’s dun tint, which consisted in the colour of the ueck approaching to dun and in the same pale tint in a less degree appearing on the rump. But Darwin wrote :—“ These colts were partially dun-coloured, and were striped on the legs more plainly than the real hybrid, or even than 1 «Animals and Plants under Domestication ’’ (1868), i, p. 59. 2 Tbid., p. 61. ’ There was also a fourth foal born after Lord Morton’s communication very like the second and third. ‘Their portraits are in the Royal College of Surgeons Museum in London. 4 Animals and Plants under Domestication,’’i, p. 403. Witson—The Inheritance of the Dun Coat-Colour in Horses. 189 the quagga. One of the two colts had its neck and some other parts of its body plainly marked with stripes. Stripes on the body, not to mention those on the legs, and the dun-colour, are extremely rare.’”! However, if Darwin thought the colts—both the colts—to be more dun than Lord Morton’s description warranted, some later writers have gone much farther and called them dun altogether. Yet if we are to judge by their portraits, painted by Agasse—“ the accurate Agasse,” as Hamilton Smith called him—and now in the museum of the Royal College of Surgeons in London, they were not dun at all, but just such ordinary bays, excepting for the extraordinary striping, as might be met with anywhere. It is also doubtful whether the “black Arabian” was not a very dark brown. Before discussing the data collected concerning duns, we may first refer to some of the difficulties connected with the question of colour, the most serious of which is the error of description. This applies to all colours, but most of all, perhaps, to grey, since grey horses are not usually born so, and their true colour is not disclosed until one at least, and frequently several, coats have been cast. Other colours may be misdescribed by the describer not knowing them well enough; but, in some cases, those who have a good knowledge of coat-colours may call one colour by another’s name when the shade of the one approximates to a shade of the other. Secondary markings help to mark some colours, as, for instance, the lack of black “points” in chestnuts and their presence usually, together with frequent lighter-coloured muzzle-patches, in bays and browns. But these distinguishing marks are not so well known as might be desired, and misdescriptions result in consequence. As yet no clear distinguishing mark has been found to separate bay and brown; and so these colours are frequently confused. And, since the muzzle-patch, though frequent, is not constant in bays, dun, which has not got it, runs some risk of being called bay, and bay of being called dun, when the shade of the one approximates to a shade of the other. Dun also is liable to be called chestnut: an example being found in Low’s “ Breeds of the Domestic Animals of the British Islands,” in which the Connemara breed of horse is represented pictorially by a dun, but is described as “ generally of the prevailing chestnut colour of the Andalusian horses.”* 1 « Animals and Plants under Domestication,’’ i, p. 403. 2 Low repeats the same description in his ‘‘ Domesticated Animals of the British Islands,’’ 1846, p. 523. 190 Scientific Proceedings, Royal Dublin Society. The data now brought together come chiefly from stud-books, but also from animals not entered in stud-books. But in neither case is it possible to find many instances of individual animals having a large number of progeny —and such instances are the most desirable—because dun has been an unwelcome colour in all British breeds, not only in stud-book times but before them, and, so, has not been bred from freely. Some breeds, as, for instance, the Suffolks, Yorkshire Bays and Coach Horses, and Shires, have no duns—or at any rate only very few—in their stud-books. The dun colour, which had been receding northwards and westwards, had left the east coast before these breeds were entered in stud-books. Dun entries occur, however, in all our other stud-books, namely, in the Shetland, the Clydesdale, the Hackney, the Polo and Riding Pony, and the Thoroughbred. The last contains a comparatively larger total number of entries concerning dun and also the largest number of individual dun animals leaving a fair number of progeny. Curiously enough, these individual animals, with one exception, the Gower Dun Barb, belong all to one family, the explanation being no doubt that this family had racing ability, and so was bred from for a few generations in spite of its colour. The other dun and presumably dun animals which left either only one or two recorded progeny or none at all are these:—the Darcy Yellow Turk, presumably a dun of Charles the Second’s time which left two sons, viz.. Spanker, a bay, and Brimmer, whose colour is not given; Lord Oxford’s Dun Arabian, imported early in the eighteenth century, which left two daughters whose colours are not given ; Thwaitess Dun Mare, a daughter of the Akaster Turk, living early in the eighteenth century, which left a son and a daughter whose colours are not given ; the Northumberland Golden Arabian, presumably a dun, which left a daughter, Leda, whose colour is not given; and three others which left no recorded progeny, viz., Morgan's Dun, a dun colt by His Majesty’s (George the Second) one-eyed grey Arabian out of young Kitty Burdett, and a dun filly by Gregory’s Arabian out of Miss Middleton. None of the foregoing is responsible for a dun entry other than its own in the stud-book. In addition to these there was a filly by Young Cade out of Miss Thigh (1763?) entered as dun; but it is doubtful if she was dun, for none of her nine foals was recorded as such. The following table shows in detail the results of the matings with the dun family above referred to, and also with the Gower Dun Barb, Witson— The Inheritance of the Dun Coat-Colour in Horses. 191 TasLe or Enrries concurninc Dun In THE Firxsry VoLuME oF THE THOROUGHBRED Srup-Book.! First GENERATION. 3 | g | 3 Sire or Dam. 3 Dam or Sire. 3 Progeny. aS) a1 | Page. o o ‘s) 2 s =} Silverlocks, ch. [?]| Godolphin Arabian | bay | filly (B.i) dun | 1788 | 183 do. do. filly (B.ii) {dun] | 1739 | 183 do. Middleton Saucebox| ? colt, Silvertail dun | 1740 | 188 do. Godolphin Arabian | bay | colt, Buff-coat(B.iii)} dun | 1742 | 183 do. Whitefoot ? filly ? ? 183 Srconp GENERATION. (B.i) mare, dun | Devonsh. Blacklegs| ? | colt, John Trot ? R 93 do. Crab er. | colt, Brilliant(C.iii)| dun 1750 93 do. Oroonoko blk. | colt P 1753 93 do. do. | filly 2 ? 93 (B.il) mare, {dun]} Snip br. | filly ? 1748 93 do. Shock bay | colt, Ginger dun | 1750 93 do. do. colt, Easby Miller | dun | 1751 93 do. do. colt, Silvertail dun | 1753 93 do. do. colt ch. [7], 1754 93 do. Slouch ch. colt, Well-done. dun | 1756 93 do. Shakspeare ch. | filly dun P 93 do. Young Snip er. filly (C.i) dun 1760 93 do. do. filly bay 1762 3 do. Young Cade bay | filly, Isabella (C.ii) | dun | 1765 93 (B.iii) Buff-coat, . | dun | Somerset Arabian | gr. colt er. 1753 30 | mare do. | Cartouch mare ? colt, Creampot dun 1755 56 do. | Cloudy ch. colt, Turf ch. [2] 1755 61 do. Jigg mare ? colt, Whitefoot dun 1749 | 106 do. do. colt dun | 1751 106 THIrpd GENERATION. (C.i) Young Snip | dun | Syphon ch. colt dun | 1771 | 194 mare Nabob p colt dun | 1773 | 194 | Sulphur ? filly dun | 1775 | 194 Count br. colt ? 1779 | 194 (C.ii) Isabella, dun | Squirrel bay | colt, Pierrot dun | 1771 | 104 Herod bay | colt, Rebel bay | 17738 | 104 Squirrel bay | filly ? 1774 | 104 Herod bay | colt bay | 1775 | 104 do. colt, Golden Dun | dun | 1777 | 104 do. filly bay | 1778 | 104 do. colt dun | 1779 104 do. colt ? 1780 | 104 Rutland Arabian P colt bay | 1787] 104 Wisbech ® colt bay | 1788 | 104 1 The fifth edition (1891) has been used. SCIENT. PROC. R.D.S., VOL. XII., NO. XIV, on 192 Scientific Proceedings, Royal Dublin Society. THIRD GENERATION—continued. € E 5 Belle Sire or Dam. 2 Dam or Sire. & Progeny. I oa S | (=) oO 2 | 3 A (C.iii) Brilliant, dun | Lord Oxford’s grey | gr. filly dun | 1771 j ; Babraham mare gr. | filly, Lily of the bay. | 1771 Valley Babraham mare gr. filly R 1763 Blank Mixbury ? filly ? 1766 do. colt, Spindle dun | 1767 Crab mare ? filly {gr.] | 1758 Cade mare bay | colt, Petulant dun | 1767 Cade mare ? colt ? 1771 Cade mare er. colt > 1769 Cara ? colt, Opinion ch. 1771 Cassandra bay | filly dun | 1763 Changeling mare | bay | colt, Nabob blk. | 1762 Young Country ? colt, Amethyst ch. 1756 Wench | Crab mare gr. filly gr. 1758 do. colt bay | 1766 | do. colt br. 1767 do. colt, Gewgaw bl. 1770 | Lady Anne bay | filly, Virgin dun | 1760 | Lath Mare ? colt, Richmond bay | 1763 Atalanta bay | filly, Sultana ? 1764 Lovely ch. colt, Sparkler ch. 1770 Miss Modesty ? colt ? 1776 | Miss Vernon bay | colt bay | 1769 Modesty ch. colt, Bellino bay[?}| 1766 Panton Arabian | gr. filly dun | 1771 mare do. gr. colt gr. 1772 | Peggy bay | colt, Spangle dun | 1769 Pussy bay | colt dun | 1771 | Rachel ? colt, Dunny dun | 1771 Regulus mare ? filly bay | 1768 do. filly 2 | 1769 Regulus Tartar roan | colt, Don Dun bay | 1769 Sally ? colt ? 1770 Shepherd’s Crab ? filly bay | 1761 mare do. filly bay | 1765 do. colt dun | 1766 do. filly (D.i) dun | 1767 do. colt, Gem dun | 1768 do. filly bay | 1770 Shepherd’s Crab | bay | filly, Brillianté ch. 1766 mare Wasp er filly, Catherina bay | 1768 Miss Slammerkim! | gr. colt, Ballario bay | 1763 do. filly bay | 1764 do. filly bay | 1765 do. filly, Lais bay | 1766 do. colt, Paris bay | 1767 do. colt, Dorilas dun | 1768 do. colt dun | 1770 do. colt, Ethon ch. 1771 do. filly, Loretta dun | 1774 Golden Grove ck. | colt dun | 1771 Page. 1 This mare breeds like a bay. Witson—Vhe Inheritance of the Dun Coat-Colour in Horses. 198 Fourra GENERATION. | | 4 5 | : g | 3 Sire or Dam. a) Dam or Sire. 2 Progeny. | 8 + | Page 3 3 3 3 o i=) | |} © — a | | (D.i) Brilliant mare | dun | Eclipse ch. filly ? 1772 43 | Vernon Arabian ch. colt, Custard dun | 1774 43 Florizel bay | colt, Crookshanks | bay | 1777 43 do. filly bay | 1783 43 do. colt bay | 1784 43 Highflier bay | colt dun | 1786 43 Tur Gower Dun Bars’s Srock. he Honey Dun | dun | Babraham mare! bay | filly, Honeycomb | dun | 1760 25 ar Cadette br. filly bay | 1757 53 Crab mare gr. ?]| filly br. 1759 68 do. colt bay | 1760 68 do. colt dun | 1763 68 Fly ch. | filly bay | 1758 87 Godolphin Arabian |[bay ?]} filly bay | 1762 92 mare Louisa bay | colt dun | 1757} 119 do. colt dun | 1758} 119 do. colt bay | 1769) 119 Partner mare bay | filly bay | 1761} 141 do. colt dun | 1762] 1651 The colours attached to each animal in the above table are those given in the stud-book; but where no colour is given and the colour can be inferred, or where that in the stud-book can be shown to be wrong, the inferred or corrected colour is attached in brackets. Omissions and errors occur in all stud-books; but some corrections can be made by reason of the work already done upon the inheritance of coat-colour in horses. Few corrections are necessary in the Thorough-bred Stud-book, even in the earliest volumes. Judging by the greys, the errors in the first volume are not more than four 1 This mare is stated to have had also, in 1759, a dun colt, Doubtful, either by Blank, a bay, or the Gower Dun Barb. 2In this connexion, and in addition to Mr. ©. C. Hurst’s work and to a paper in the second number of The Mendel Journal by Mr. Robert Bunsow, the writer of this paper wishes to draw attention to two most valuable papers published in Landwirtschaftliche Jahrbiicher, vol. xvii, 1888. They are on the colours of the horses of the royal Trakehnen studs in Germany, by Dr. M. Wilckens and Dr. Crampe. The writer saw these articles casually ten or twelve years ago, and, although he has searched for them again and again during the last three years, could not find them, through not remembering where they were published. A few weeks ago his attention was drawn by Mr. Condon, the Librarian of the Royal College of Science, to some “ papers on the colour of horses ”? in an odd back volume of the Jahrbiicher in the college library. These were the two papers so anxiously sought after. Had these papers been available during the last few years, an enormous amount of very hard labour would haye been saved, for from them the relative positions of chestnut, black, QF 194 Scientific Proceedings, Royal Dublin Society. per cent.; for we know grey to be dominant to the other colours (roan, perhaps, excepted), and that, therefore, every grey foal must have at least one parent grey; yet, among 248 grey foals noted in that volume, only nine are entered as having neither parent grey. Inferences can be made with greatest confidence concerning greys. Ifa dam whose colour is not given have a grey foal to a horse of another colour, she is presumably grey ; if she have several such, she is grey without doubt. As the colour descends towards chestnut, confidence also descends, and greater care must be exercised in drawing conclusions; but help can be got frequently from the colours of parents and progeny, and from those of other near rela- tives, even though the colours be well down the scale. For example, the colour of the third parent (B 2) in the preceding table is not given in the stud-book; but the fact that six of her foals by five different sires were dun is very strong evidence that she herself was dun; and this inference is con- firmed, if that were necessary, by the further fact that one of her sisters and both her brothers, all well-known animals, were of that colour. From the foregoing tables the position of dun can be worked out by more than one method. We could employ the statistical method, and, by adding up the total results of the matings of dun with other colours, find out which colours it did and which colours it did not include. But, since the total numbers are so small, it will be better, in the first instance, to find the position of dun by considering the gametic composition of some of the best-known animals. The mother of this dun family, Silverlocks, was described as a chestnut. Let us assume her colour to have been correctly described. She had three dun foals to the Godolphin Arabian, who was a homozygous bay.1 His foals out of Silverlocks must, therefore, have got their dun colour from their dam, in whom it must have been hidden by chestnut; and, since each of this homozygous bay sire’s three dun foals must have carried a bay bay and brown (these two are not separated), and grey could haye been made out easily and clearly. Three of Dr. Crampe’s conclusions as to what happens when both parents are of the same colour, which are underlined in his summing-up, might be quoted :— i, Chestnuts have chestnut foals exclusively, among which are chestnut-roans and chestnut- greys (darunter stichelhaarige Fiichse und Fuchsschimmel). ii. Blacks have both black and chestnut foals, and also roans and greys of these colours. iii. Browns (that is browns and bays) have foals of all colours. Crampe points out that the stud-books show exceptions to rule among chestnuts and blacks, but that those exceptions, for the most part, are the result of erroneous entries: ‘‘ der bei weitem grosste Theil dieser Falle auf irrthtiimlichen Eintragungen beruht.’’ Crampe did not discover the position of roans and greys, or he would have seen why they are registered as occasionally occurring from other colours. Roans and greys among browns caused him to say browns have foals of all colonrs. 1The colours of at least fifty-six of his foals are known, and there was not a chestnut among them. From chestnut mares he had thirteen bays, one black, and one brown; from bay mares, sixteen bays and one brown; from grey mares, seven greys and three bays; and from mares of unknown colour, one grey, one brown, and twelve bays. ‘The browns and blacks are just such a pro- portion as might be expected in view of the uncertainties in descriptions of bay, brown, and black. Witson—Vhe Inheritance of the Dun Coat-Oolour in Horses. 195 gamete, bay must be recessive to dun. Accordingly, bay, being recessive to dun, must also be recessive to chestnut, which, as we know, is absurd. Our assumption with regard to Silverlocks needs revision therefore; and we can only suggest either that she was dun or some colour containing dun, or that she was not the dam of the Godolphin Arabian’s three dun foals. But there is no need to adopt this kind of argument, for the homozygous bay Godolphin Arabian’s three dun foals are sufficient proof that dun is dominant to bay. Hach of them must have carried a bay gamete from their sire, which was hidden by dun, and, therefore, recessive to it. The relative positions of dun and chestnut can also be made out from the table. But there is really no need to do this; for, since chestnut is recessive to bay, and bay to dun, therefore chestnut is @ fortiori recessive to dun. The table may be used in confirmation. Brilliant (C3), the best-known dun of this Thoroughbred dun family, was the son of Silverlocks’ eldest dun daughter and Crab, a very famous sire. Brilliant had a number of chestnut foals, and this colour must have been included in his gametic composition, and is, there- fore, recessive to dun. His dam, as we have just seen, was a heterozygous dun, with bay recessive, while his sire was a heterozygous grey, with chestnut recessive! In him a dun gamete from his dam must have united with a chestnut gamete from his sire; for, had a dun gamete united with a grey, Brilliant would have had a number of grey foals, but no chestnuts. The position of dun relatively to brown and black cannot be made out from the table, because the colour of only one foal from a brown and dun mating is given, and only two black foals appear in the table. Besides, there is uncertainty as to whether brown and black were accurately dis- tinguished from each other. Black, however, may be taken as recessive to dun, since it was found to be recessive to bay in the previous paper. Nor can the relative positions of dun and grey be made out by an exami- nation of the gametic composition of the animals concerned ; for, although the duns in the table have grey foals only when mated with greys, the grey gametes of the foals may all be associated, although this is unlikely, with recessive bay and chestnut gametes from their dun parents. In any case, the numbers are few. For evidence on this point we must go to the Polo and Riding Pony Stud-book, in which we find the statistical argument suggested in the last paragraph completely confirmed ; for, here again, and now over a considerable number of cases, dun does not produce grey unless it be mated with that colour. ‘There are now eleven volumes of this stud-book published, in which 50 matings of dun with other colours than grey are recorded, and in no case 1 This has been found by working through Crab’s progeny in the first volume of the stud-book. 196 Scientific Proceedings, Royal Dublin Society. has a grey foal resulted; while, from 35 matings of dun with grey, 10 grey foals are recorded. These 35 foals were 1 chestnut, 3 black, 5 bay, 1 brown, 15 dun, and 10 grey. A very striking case might be quoted from Clare Island, off the west coast of Mayo. A dun pony sire stationed there for a year left about 50 foals, and, according to Mr. Garvey, the Department of Agriculture’s officer now on the island, “‘ there were no grey ones, except one from a grey mare.”’ The statistical evidence can be confirmed directly by a few individual cases. A black stallion, The Monk, and a grey polo pony mare, Sibyl, had a dun foal, Hermit!; Old Highland Laddie, grey, and a grey pony mare had a dun foal?; Shooting Star, a grey pony sire, and Bleddfa Periwinkle, a dark bay mare, had a dun roan foal*; The Chief, a black Clydesdale, and Grey ‘less, a Clydesdale mare, had a dun foal, Nell of Haplands‘ ; and there is the case quoted in the previous paper from Professor Cossar Ewart: “in one specimen of this variety’ met with in Perthshire (a 14-hands grey mare which produced a dun colt to a grey garron) the profile isstraight.... There are two cases quoted by Dr. Crampe in the paper referred to in the foot-note on p. 193. A grey horse, Sterling II, sires two dun foals, one from a black mare, Nacht, the other from a brown mare, Galante.’ There now remain only the relative positions of dun and brown. In the Thoroughbred, Polo, and Clydesdale stud-books only 23 matings of brown with dun have been found where the colours of the foals are given: but in no case can the gametic composition of the parents be worked out. The colours of these 23 foals are 1 black, 3 bay, 10 brown, and 9 dun; but these, although suggestive, do not admit a clear inference. Evidence on the point has been sought in the west of Ireland, where there is still a very considerable number of dun ponies. Mr. Michael Scully, one of the Depart- ment of Agriculture’s officials in County Mayo, reports on some dun stock in 6 that county, and mentions two dun mares which have had brown foals to black sires. One of these mares had three foals dun and one brown, and the other mare had one foal dark brown and the other black to black sires.® But the fullest evidence comes from Clare Island. Indeed, it is sufficient to place dun in position with regard to every colour. This island is one which received special attention from the Congested 1 Polo and Riding Pony Stud-Book, vol. v, p. 56, Polo Pony Section. 2 Thid., vol. viii, p. 158, Fell Section. 3 Tbid., vol. ix, p. 91, Welsh Section. 4 Clydesdale Stud-Book, vol. x, p. 413. 5 The long-headed variety. 6 Highland Society’s Transactions, 1904, p. 267. 7 Landwirtschaftliche Jahrbiicher, yol. xvii, p. 858. Sterling left also two fawns, no doubt shades of dun. Sterling’s other progeny mentioned by Crampe were greys. 8 Crampe mentions vwo duns, viz. Culblanc I and Pandora, which had a brown daughter, Antigone. See Landwirtschaftliche Jahrbiicher, xvii, p. $54. Wiitson—The Inheritance of the Dun Ooat-Oolour in Horses. 197 Districts Board. Pony stallions were sent out by the Board for service on the island from 1895 to 1903; and the practice has been continued by the Department of Agriculture down to the present time. ‘he sires in service since 1895 are as follows :— 1895, 0 . Movement, . Welsh, . dark chestnut. 1896, 6 0 do. 1897, : : do. 1898 (apart) . do. 1898 (a part) . Bay Prince, . Hackney, . bay. 1899, do. 1901, 5 . Oscar, ’. Norse, dune 1902, Bares do. 1903, ; , do. 1904, é . Norseman, . Norse, . dun. 1905, : F do. 1906, : : do. 1907, 6 . Express IV., . Welsh, . black. 1908, . Conn, . Connemara . dun. 1909, ; . Movement, . Welsh . dark chestnut. 1910, é 6 do. ; 1911, 6 9 do. At the time the first dun sire was introduced, the mares on the island were chiefly browns and bays, with a very few duns and greys.!. The annual birth-rate is from forty to sixty foals, the most of which are exported to the mainland in the year of their birth. Accurate figures therefore cannot now be got ; but Mr. Garvey, the present agricultural instructor on the island, has made close and careful inquiry ; and one or two quotations from his letters will make the question perfectly clear. Information has also been received from Mr. M‘Cabe, of the Granuaile Hotel, Clare Island. “There were three dun stallions brought in by the Department. All the foals of the first two were dun, and the foals of the third were of different colours.” (28th October, 1911.) “There were three-fourths? of the last [dun] stallion’s foalsdun. The other colours were brown and bright red. There were no greys, except one from a grey mare.” (19th November, 1911.) “T have been told by a good many of the islanders, especially the man that kept the stallions, that all the foals got by Norseman and Oscar were dun except one that was rather white.” (8th December, 1911.) Mr. Garvey’s earlier statements were seen to be so important that he was 1 Information supplied by Mr. Garvey and Mr. M‘Cabe, of the Granuaile Hotel, Clare Island. 2 This, of course, is only an estimate. : 3 A reddish bay found frequently among Western ponies. y i) Pp 198 Scientifie Proceedings, Royal Dublin Society. questioned again and again to see whether his statement that “all the foals of the first two were dun ” could be shaken. Additional information, the result of closer and closer inquiry, comes out in every succeeding letter ; but the first two sires’ foals are always dun. Such cases as “‘the one that was rather white” are met with occasionally. The foal is a kind of creamy white, which darkens into a dun. Mr. Garvey mentions two such foals by the chestnut sire “ Movement,” out of dun mares. Another quotation from Mr. Garvey will show the thoroughness of his inquiries, and at the same time bring out a very interesting point. The Welsh pony “Movement” has been stationed twice on the island—the second time after a lapse of eleven years. Consequently he must have been mated again and again with his own descendants. He has a very peculiar irregular grey splash on the rump and loins. This splash was not noticed in his progeny of 1896 to 1899; but it is noticed in his recent progeny, and Mr. Garvey observes that it does not occur where the foal is dun.' “In the majority of cases, black, bay, and red mares served by this horse have produced foals of the same colour as the sire with the white stripe; but it has not occurred on any occasion that the dun foals have the white stripe on their backs.” Apparently the splash on the rump is recessive; but it did not get a chance to come to the surface till “ Movement’s”’ second visit. On Clare Island, therefore, there have been two homozygous dun stallions ; and their progeny, which must have mounted to about 300, show that their colour is dominant, not only to brown, but to all other colours on the island, excepting grey. In searching for evidence concerning dun, three other colours have been occasionally met with—namely, piebald and skewbald, fawn, and cream. About thirty of the first kind were seen; and where the parentage was recorded there was no progeny without either a piebald or skewbald parent. Only a few fawns were noticed; but notes were kept concerning about thirty cases of creams. Unfortunately, however, they allow no clear inference to be drawn. Creams are usually found where dunsare found; and individuals are described as “‘ cream or dun,” ‘dun cream,” ‘‘ cream dun,” and so on. From this, cream might be expected to be a variety of dun, and, when black “points” are present, it probably is so. But occasionally such descriptions as “chestnut cream” and “cream chestnut”’ are also found. If these are misdescriptions, they have no weight ; but if not, there may also be a cream which is a variety of chestnut. ‘I'wo entries in the Polo Pony stud-book— _ 1 The dun foals’ dams must haye been dun and therefore not ‘‘ Movement’s’’ daughters. 2 Oscar, the Norse sire sent to Clare Island, is recorded as a ‘‘ dun or cream, with white or cream mane and tail, and bla:k stripe down back,’’ in the books of the Congested Districts Board, although he is clearly a dun to most who have seen him, Witson—The Inheritance of the Dun Coat-Colour in Horses. 199 namely, Nutmeg,! cream, by Woodman, chestnut, out of Meg, cream; ani Maey,’ cream, by a chestnut horse, out of Baby, dun—place cream somewhere between dun and chestnut; but the remaining data carry us no farther; and there the question must remain for the present. In the foregoing arguments concerning dun, the gametic composition of well-known animals has been chiefly relied upon. The argument from statistics could also have been used; but these are small. The following is an abstract of them, the Clare Island data not included. Cases the least doubtful are treated as entirely so. For instance, the foals of the filly by Young Cade out of Miss Thigh, which was registered as grey, but bred like a bay, are put in the column for cases in which the colour of one parent is unknown. AxpsTRact oF Dun Marines. Contours oF PARENTS. = Cotours or Foats. Dun X Chestnut, . | Thoroughbreds, Clydesdales, Ponies, 5 Non-registered, |] | u& Mile [eee L111 | co Il oi (elelelas s i=) Dun X Black, . | Thoroughbreds, Cly desdales, Ponies, Non-registered, | | ele at [esata ale Hol | Jel | wl Il Dun X Bay, . | Thoroughbreds, Clydesdales, Ponies, : Non-registered, |) es re l nae ll wol AUN S or lle —_ | Dun X Brown, . | Thoroughbreds, Clydesdales, Ponies, Non-registered, Slee leat | ) honors [Feoten| lool [0 | | Dun X Dun, . . | Thoroughbreds, Clydesdales, Ponies, Non-registered, Lot leet Ht I (lel wo l | Vela (ieee Dun X Grey, . | Thoroughbreds, Clydesdales, 0 Ponies, 6 7 Non-registered, let lrol wel ror wool war! os eleie Dun X Roan, . | Thoroughbreds, Clydesdales, Ponies, Non-registered, alee (eli Le LI eatin alt | Dun X unknown, . | Thoroughbreds, Clydesdales, Ponies, 5 Non-registered, He COR EN Jello | co] o elielal eel ror 1Vol. i, p. 90. 2Vol. vi, p. 121. SCIENT. PROG. R.D.S., VOL. XIII., NO. XIV. 26 200 Scientific Proceedings, Royal Dublin Society. But it must not be assumed that no cases were found while data concerning dun were being collected which would suggest the dislodgment of dun from the position in which we have placed it. A few such cases were found; but only three in the stud-books—viz., two Clydesdales and one pony, which indicate an error of only 1:5 per cent. ‘Vhe others are Darwin’s three cases and three cited by Mr. J. B. Robertson. These make nine cases in all, and it may be suggested fairly that in all probability they are misdescriptions either of colour or paternity. Darwin’s second and third cases ought not perhaps to be quoted, as each may have had a grey parent. The following are the nine cases :— Progeny. Sire. Dam. Authority. Dun filly Dolly, foaled | Bay Dartmoor pony, | Black Dartmoor mare, | Polo Pony Stud-Book, 1893 Chagford Black Bess vol. v, p. 65 Dun filly, foaled 1878 | Brown Clydesdale, Bay Clydesdale, Polly | Clydesdale Stud-Book, Jack’s the Laird vol. iv, p. 51 Dun filly, Kate, foaled | Bay Clydesdale, ‘The Brown Clydesdale, Love do., vol. xiii, p. 505 1887 Professor Fallow dun foal Bay horse Black mare Darwin’s “ Animals and Plants under Domes- tication,”’ vol. i, p. 59 Mouse-dun foal Not dun Not dun dc. (from Hofacker) Mouse-dun foal Not dun Not dun do., do. Dark iron-grey foal? Brown Hackney, Handy | Yellow dun Welsh cob | Mr. J. B. Robertson in Andy The Veterinary Re- cord, October 15, 1910 Light grey foal? do. do. do. Bay dun hackney filly, | Brown Hackney, Light yellow bay Hack- | Mr. J. B. Robertson in foaled 1898 General Gordon ney mare, with black Nature, Dec. 1, 1910 dorsal band, Fanny Gordon To the foregoing cases ought to be added another eight cases cited from the Thoroughbred Stud-Book, first by Mr. J. B. Robertson in “The Veterinary Record ” for October 15th, 1910, and afterwards in “‘ Nature” of November 24th, 1910, by Professor Cossar Ewart, as “reversions to dun,” and, therefore, exceptions to our placing. Six of these “reversions” are by no means free of the charge of misdescription, and the other two do not inter- fere with our scheme. To show this we give the cases as described by Mr. Robertson and Professor Ewart, and add in a parallel column such 1 These two cases, if correct, would place dun dominant to all other colours (roan perhaps excepted) , and so demolish its last chance of ever becoming a reversion. Witson— The Inheritance of the Dun Coat-Colour in Horses. 201 remarks as are necessary to indicate how doubtful are the grounds on which they may be taken as “ reversions to dun.” Progeny. Sire. Dam. Remarks. Dun colt, foaled 1730. Dun filly, foaled 1763. Dun filly, foaled 1829. Dun or chestnut filly, Sancta, foaled 1884. Light dun filly, foaled 1886. Dun filly, Sarah Curran, foaled 1892. Dun colt, foaled 1897. Bay-dun filly, foaled 1907. King George II’s one- eyed grey, Arabian. Young Cade, bay. Lottery, brown. Exminster, bay. Lord Gough, bay. Robert Emmet, bay or brown. Sir Frederick, bay. Ash, chestnut. Young Kitty Burdett, bay. Miss Thigh, grey. Octavia, bay. Hallowe’en, chestnut. Danseuse, brown. Cellulites, black. Lobelia, bay or brown. Unexpected, bay. ‘Lhe sire here is grey, and our placing of dun is not interfered with. The dam here is grey, and the case is referred to in the text. This foal died when two days old. See vol. y, To 0, The description indicates doubt. This filly had several foals, none of which is entered as dun. See vols. xy, p. 183, and xvi, p- 198. This filly is entered as bay when a foal in vol. xvi, p- 577, and light dun in vol. xx, p. 499. She had eight or nine foals, but none is entered as dun. In vol. xvii, p. 692, Cellulites” foal of 1892 is entered thus: ‘£1892... f. (dead) by Robert Emmet.’’ In vol. xviii, p. 727, her foal of 1892 is entered thus: “©1892, dun f. Sarah Curran, by Robert Emmet,’” and there is a foot-note :— “This mare erroneously appeared in last vol. as dead.”’ In vol. xix, p. 368, this foal is entered “‘b. or dun c.”’ In vol. xxi, p. 839, this filly is entered as a foal, ‘‘b. or dun f.”’ et bo SCIENTIFIC PROCEEDINGS. VOLUME XIII. . A Seed-Bearine Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By 'T. JoHNson, D.so., F.L.S. (Plates I-III.) (March, 1911.) Is. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcz H. Prruysries, B.sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wituram Brown, B.so. (April 15, 1911). 1s. . A Thermo-Hlectrie Method of Cryoscopy. By Henry H. Dixon, sc.p., F.R.s. (April 20, 1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density 0’ a Substance, e.g. Wax, in passing through its Fusion Stage. By Wriu1am J. Lyons, 8.a., a.R.c.sc. (Lonp.). (May 16,1911). 6d. 6. Radiant Matter. By Joan Jony, sc.p., r.R.s. (June 9, 1911.) 1s. 10. 11. 12. 13. 14. . The Inheritance of Milk-Yield in Cattle. By James Wiuson, M.A., B.SC. (June 12, 1911.) 1s. . Is Archzopteris a Pteridosperrm? By T. Jounson, D.sc., F.L.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and ‘of other Species of Archeopteris in Ireland. By T. Jonson, D.sc., F.u.s. (Plates VII., VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Prorgessor Joun Jouy, M.A., SO.D., F.R.S. (July, 1911.) Gd. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Joun Jony, sc.p., F.x.s., and Louis B. Smyre, B.a. (Plate IX.) (August, 1911.) 1s. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By HE. A. Newent Arper, M.A, F.LS., F.G.S. (January, 1912.) 1s. Forbesia cancellata, gen. et. sp. nov. (Sphenopteris, sp., Baily). By T. JoHNSON, D.sc., F.u.s. (Plates XIE. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By Jamzs W1LsoN, M.A., B.SC. (January, 1912.) 1s. DUBLIN: PRINTED AT fHE UNIVERSUtY PRUSS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIIL. (N.S.), No. 15. FEBRUARY, 1912. ON THE VACUUM TUBE SPECTRA OF THE VAPOURS OF SOME METALS AND METALLIC CHLORIDES. Parr L—CADMIUM, ZINC, THAL- LIUM, MERCURY, TIN, BISMUTH, COPPER, ARSENIC, ANTIMONY, AND ALUMINIUM. BY JAMES H. POLLOK, D.Sc., ROYAL COLLEGE OF SCIENCE FOR IRELAND, DUBLIN. (PLATES XV. and XVI.) [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. ERS WILLIAMS AND NORGATE, Ceara « 14, HENRIETTA SYREET, COVENT GARDEN, LONDON, W.C. 1912. Oe ye Jal Hi USEY Price One Shilling. Koval Bublin Zociety. FOUNDED, A.D. 1731. INCORPORATED, 1749. OOS EVENING SCIENTIFIC MEETINGS. Tue Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Jllustrationstin a complete form, and ready for transmission of the Editor. Witson— The Inheritance of the Dun Coat-Colour in Horses. 201 remarks as are necessary to indicate how doubtful are the grounds on which they may be taken as “ reversions to dun.” Progeny. Sire. Dam. Remarks. Dun colt, foaled 1730. Dun filly, foaled 1763. Dun filly, foaled 1829. Dun or chestnut filly, Sancta, foaled 1884. Light dun filly, foaled 1886. Dun filly, Sarah Curran, foaled 1892. Dun colt, foaled 1897. Bay-dun filly, foaled 1907. King George II’s one- eyed grey, Arabian. Young Cade, bay. Lottery, brown. Exminster, bay. Lord Gough, bay. Robert Emmet, bay or brown. Sir Frederick, bay. Ash, chestnut. Young Kitty Burdett, bay. ~,, Thigh, grey. Octavia, bay. Hallowe’en, chestnut. Danseuse, brown. Cellulites, black. Lobelia, bay or brown. Unexpected, bay. ‘Lhe sire here is grey, and our placing of dun is not interfered with. The dam here is grey, and the case is referred to in the text. This foal died when two days old. See vol. y, p- 90. The description indicates doubt. This filly had several foals, none of which is entered as dun. See vols. xv, p. 183, and xvi, p. 198. This filly is entered as bay when a foal in vol. xvi, p- 577, and light dun in vol. xx, p. 499. She had eight or nine foals, but none is entered as dun. In vol. xvii, p. 692, Cellulites’ foal of 1892 is entered thus: ‘*1892...f. (dead) by Robert Emmet.’? In vol. xviii, p. 727, her foal of 1892 is entered thus: “©1892, dun f. Sarah Curran, by Robert Emmet,” and there is a foot-note :— “‘This mare erroneously appeared in last vol. as dead.”’ In vol. xix, p. 368, this foal is entered “b. or dun ¢.’’ In vol. xxi, p. 839, this filly is entered as a foal, ‘‘b. or dun f.”’ SCIENT. PROC. R.D.S., VOL, XIII., NO. XIV. XV. ON THE VACUUM TUBE SPECTRA OF THE VAPOURS OF SOME METALS AND METALLIC CHLORIDES. Parr I.— CADMIUM, ZINC, THALLIUM, MERCURY, TIN, BISMUTH, COPPER, ARSENIC, ANTIMONY, AND ALUMINIUM. By JAMES H. POLLOK, D.Sc., Royal College of Science, Dublin. (Prares XV. anp XVI.) [Published Fepruary 21, 1912]. Since the researches of Dr. J. Plicker, of Bonn, and Dr. J. W. Hittorf, of Miinster,! in 1864, very little work has been done in the examination of the vacuum tube spectra of the vapours of metals and their compounds; and writers on the subject invariably refer to the difficulties and uncertainties of observations on vacuum tube spectra, for impurities show their spectra with surprising persistency, and many unexpected phenomena manifest themselves. In view of the growing importance of this class of spectra, in the discovery and identification of new gases, and the investigation of the pro- ducts of the action of radium and radio-activity, it seemed desirable to make a systematic examination of the vacuum tube spectra of as many substances as possible. Some years ago I began this work by photographing and examining the spectra emitted by a large number of old tubes in the collection of the Royal College of Science. ‘These tubes were, I believe, made by Mr. C. F. Cassalla many years ago, and are, no doubt, precisely the same as those used by Professor C. Piazzi Smyth in his investigations ‘‘On the Measurements of Gaseous Spectra” in 1884, and were very likely made at the same time—the gases being prepared and purified in the manner described in the above paper. The results were very unsatisfactory, most of the spectra showing the banded spectrum of nitrogen, the bands attributed to cyanogen, or the lines of hydrogen, with or without the bands of water-vapour, together with all, or some of, the lines or bands due to the elements contained in the compound in the tube ; but I did not find marked indications of definite 1 Phil. Trans., vol. cly, pp. 1-29. 1864, Potiox— The Vacuum Tube Spectra of some Metallic Vapours. 208 lines or even bands that could be readily and exclusively attributed to any definite compounds. About this time I examined the reproduction of the vacuum tube spectrum of stannic chloride in Higgenbach and Konen’s Atlas, and compared it with the vacuum tube spectrum of chlorine and the spark spectrum of tin, and noted that all the lines of the chloride were either the lines of tin or chlorine, and that I could not find any new lines due to the compound. Now the lines of the spark spectra of the metals are very well known; there is no doubt or ambiguity about these spectra, and as a preliminary step to the investigation of elementary and compound spectra it seemed desirable to obtain photographs of a large number of volatile metals and their chlorides, and see how far their spectra were composed of the lines of the spark spectra of the metal and the chlorine. In my earlier experiments I used glass tubes with quartz windows, and in some cases glass tubes with the centre part of the capillary tube of quartz, and joined the two ends by rubber tube wired on; but the former cracked and broke, and the latter could not be used with a high temperature, and much trouble was experienced until I invented the simple little quartz vacuum tube shown in the illustration, Pl. XVI., when all the difficulty vanished, and the photographs of spectra were taken with the utmost ease and rapidity. To measure every line in each spectrum and identify them all would be a very laborious task, and I do not think at all necessary at the present stage of the inquiry. In Pl. XV.I have placed the spark spectrum of the metal in each case just over the vacuum tube spectrum, and the lines that obviously correspond are identified by the use of an ivory wave-length scale applied to each spectrum, and the accepted values of the lines adopted and tabulated. In many cases lines are seen in the vacuum tube spectra that are not seen in the spark spectrum of the element. Those lines, when not due to chlorine are generally found to be due to accidental impurities in the metals or chlorides used, or to the presence of nitrogen, water-vapour, or carbon ; but ix some few cases they are not so easily accounted for, and will receive further consideration in subsequent investigations. The scope of the present paper is confined to a rapid survey of a large number of metals and their chlorides and the identification of the lines that are common to both spectra, with some indication of the relative intensities of the lines in the spark spectrum, and in the vacuum tube spectra with and without a condenser, together with the approximate position of the bands that are a prominent feature of some of the vacuum tube spectra. ‘The author hopes later to make a detailed examina- tion of a variety of compounds from the same metal, in the case of the more characteristic metallic vacuum tube spectra, to ascertain how far the presence 2H 2 204 Scientific Proceedings, Royal Dublin Society. of any of the lines or bands of a spectrum may be due solely to a particular compound, and not to either of the elements of which it is composed, or to the accidental presence of some other element. The apparatus used consisted of a spectrograph, coil, condenser, pump, dryers, pressure gauge, and quartz vacuum tube. The spectrograph was one of Sir Walter Noel Hartley’s design, the property of the Royal Society, and kindly lent me for the purposes of this research. The research was also assisted financially by the Government Grant Committee, to enable me to procure the large number of quartz vacuum tubes necessary. The spectro- graph is a one-prism instrument, fitted with quartz lenses of 15 inches focal length. It was carefully adjusted with cadmium line 17 at the angle of minimum deviation, using a barium platino-cyanide screen. This line was then brought into accurate focus on a plate, and the plate rotated until the best possible general effect was obtained from the red to the ultra violet. Through a slight defect in the plate-carrier the lines of the spectra are not vertical ; and at the time of the experiments it was not thought desirable to alter this, as the focus of the instrument was very good, and gave an excellent spectrum from the red to the extreme ultra violet. ‘lo remedy this for purposes of reproduction would have entailed a repetition of the whole of the work, which is quite unnecessary for the accurate measurement and identifi- cation of the lines, the scale at the top of the plate being only intended as a rough indication of the position of the lines to facilitate the comparison of the photographs of spectra with the table of wave-lengths. The coil was an Apps coil, giving a 12-inch spark when worked by five storage cells, and the condenser in the secondary circuit consisted of a sheet of glass, with two sheets of tin foil about 15 inches by 18 inches. The pump was of the Geryk type, supplied by the Pulsometer Company. To it were fixed drying-tubes of phosphorous pentoxide and some tubes of caustic potash to absorb any acid vapours that might be liberated from some of the chlorides; also a tube dipping into mercury, set by the side ofa barometric tube, to give a rough indication of the degree of exhaustion. Two or three strokes of the pump easily exhaust vacuum tubes to about two millimetres pressure, which is the most convenient pressure to work at. The vacuum tube, shown in Pl. XVI., is made entirely of quartz, and of the same form as the glass tubes used by Pliicker and Hittorf, but with open ends. ‘I'o one end is attached a glass stopper, through which one of the platinum electrodes passes, and to the other is attached a glass tube and stop- cock, through which the second electrode is introduced and the tube is exhausted, the junction between the glass and quartz being effected simply with an ordinary piece of rubber tube wired on. The connection to the Pottox—The Vacuum Tube Speetra of some Meitalhe Vapours. 205 dryers and pump is made by having the tube beyond the stop-cock drawn out a little, covered with a piece of thin india-rubber tubing, and capable of slipping into the cup of an ordinary mereury junction, so that the tubes can be rapidly taken to pieces, cleaned, filled, and exhausted. The illustration shows the tube on its stand, with the wires connecting the electrodes to the coil, and a Mecker burner in position for vaporizing the chloride contained in the tube. The experiments were all performed in substantially the same way: about five centigrams of the substance to be examined were placed in the lower limb of a clean dry quartz vacuum tube; the stopper with its electrode was then attached to this end, and connected to the electro-negative pole of the coil. The tube and stopcock with its electrode were attached to the other end, and to this, the upper electrode, was connected the electro-positive pole of the coil. The connecting tube was slipped into the cup of the mercury junction, shown at the side, and the vacuum tube was then exhausted by two or three strokes of the pump, warmed a little, and exhausted again for the removal of nitrogen by the traces of water vapour that are invariably present, and are found very convenient for this purpose. A Mecker or Bunsen burner was then placed under the capillary portion of the tube to keep it hot, and the side bulb containing the substance warmed by a Bunsen or Mecker burner according to the volatility of the material under examination, the burner being best held in the hand, and applied as required, so as to maintain a steady luminescence in the tube. If large quantities of vapour are evolved, bands are generated in the spectra, and this seems to be universally the case; but as the author’s present desire is to get a preliminary knowledge of the lines common to the spark and vacuum tube spectra of the metals and their compounds, this part of the inquiry was not followed up, and care was taken to avoid excessive heating, so as not to obscure the lines by the development and extension of bands. The author hopes to make a more critical examination of the bands later ; and the generalisations regarding lines do not apply to bands. When possible, a photograph was first taken of the spark spectrum of the metal, using metallic electrodes, in air, with a Hemsalech self-induction coil for the removal of air lines, and a spherical condensing lens to throw the image of the spark on the slit, thus preserving the character of the continuous and discontinuous lines, which of course is lost if a cylindrical con- densing lens is used. Wratten and Wainwright plates were used throughout. The exposure for the metallic spark spectra was one minute. With the vacuum tubes the same spherical condensing lens was used, to throw the image of the capillary tube on the slit, and an exposure of five minutes was 206 Scientific Proceedings, Royal Dublin Society. given in each case, a photograph being first taken with the coil alone, and then with a Leyden jar or condenser in circuit. In Plate X V., metallic spark spectra are marked S, vacuum tube spectra without the Leyden jar V, and vacuum spectra with the Leyden jar V’. The character of the discharge was interesting, the colour being regulated, of course, by the dominant lines in the visible part of the spectrum, but the appearance was greatly affected by the introduction of the Leyden jar, the change being generally from a voluminous discharge of uniform colour, to a thin crackling discharge of varying colour, bordered with green, the green lines that came out being those of chlorine, which for the most part did not show without the condenser, and did not show with equal facility with all compounds. The vapours of metals and their chlorides, such as cadmium, zine, and mercury, conducted the current with great ease, while the vapours of metal- loids and their chlorides, such as arsensic and antimony, allowed the spark to pass with difficulty, and only when a precisely suitable quantity of vapour was present. The tables give a comparison of the relative intensities of the more pro- minent lines of the vacuum tube spectra of the metals with and without a condenser, compared with the spark spectra of the same metals. Plate XV. shows reproductions of the spectra themselves, together with a rough scale of wave-length to facilitate identification of the lines. The wave-lengths and intensities taken for the spark spectra of the metals are those published by Dr. Marshall Watts, and are mostly from the measurements of Hder and Valenta, Exner aud Haschek, and Kayser and Runge. The general conclusions that may be drawn from a study of the spectra of the vapours of the metals and their chlorides, so far examined, are :— 1. That the lines shown by the vacuum tube spectra of metallic vapours consist of all, or some, of the lines shown by the metallic spark spectrum of the same element. 2. That those lines which show as continuous lines in the spark spectrum of an element are invariably the strong lines of the vacuum tube spectrum, and discontinuous spark lines often do not show, particularly when no Leyden jar is used. 3. That certain lines are enhanced by the introduction of a Leyden jar, and that such lines are very frequently prominent discontinuous lines in the spark spectrum of the metal. ' 4. That some lines show more prominently without a Leyden jar than with it, but this is a rather exceptional phenomenon. Pottok—The Vacuum Tube Spectra of some Metallic Vapours. 207 5. That with the chlorides you get precisely the same lines as you do with the vapour of the metal, with or without the addition of the lines of chlorine, according to circumstances. 6. That the chlorine lines, as a rule, do not show unless a Leyden jar is introduced in the circuit, and even then they do not show with equal facility with all compounds. 7. That in all cases where a line is enhanced or otherwise by the intro- duction of a condenser in the circuit with the vapour of the metal, a precisely similar change takes place with the vapour of the chloride. 8. Lines that show in the are spectrum of an element, but not in the spark spectrum, are not seen in the vacuum tube spectra of the element, either with or without a condenser. 9. That in many of the spectra, especially when much vapour is present, and no Leyden jar is used, very beautiful bands develop, some of which are entirely new to science, and these will require further study before any general conclusion can be drawn regarding them. They are quite independent of the lines of the spark spectra of the elements, and probably owe their origin to the molecules of the compounds under observation. In the tables, as usual, the strongest lines are marked 10, the numbers decreasing to 1 for lines that are just visible; » indicates a nebulous line, s a sharp line, ¢ a continuous line, @ a discontinuous line, 7 a line frequently reversed, ) a band measured at the centre and shading off on each side, b’ a band measured on the ultra-violet edge and degrading towards the red, 0” a band measured on the red edge and degrading towards the ultra-violet ; w, w, y, @ indicate the quantitative persistency of the lines in the spark spectra of solutions of the chlorides, as used in the author’s papers on Quantitative Spectra. w seen with -0Q01 per cent. or more in solution. w ” 010 ” ” ” xX ” 100 ” ” ” Co) ” 1-000 ” ” ” CADMIUM. Both the metal and its chloride give a very brilliant luminescence in the tube, and the introduction of the condenser makes a remarkable change in the spectrum of the vapour of the metal, but little difference with that of the chloride, the spectrum of chlorine not being developed. The behayiour of the lines \2748°7 and 2573-1 and the characteristic 208 Scientific Proceedings, Royal Dublin Society. group from A 2829 to A 2306 is peculiar, though many of them are very strong lines in the spark spectrum of the metal, they do not show at all with the vacuum tube spectrum of the metal unless the condenser is used. Some of them, however, show with the chloride, both with and without the condenser. Prinicpal Lines of Cadmium. Vacuum Tube. | Vacuum Tube. Tea Spark. Toe : Spark. | No L. J. | With L. J. No L. J. | With L. J. 6439-3 10 s.c.r. 8 10 2980°8 WO ROK 20 5879°3 10 s.c. 0 1 2880-9 10 b. 10) 5338-6 10 s.c. 0 1 2868-4 Si | 2 4 5154°9 3 8.d. 1 1 2837-0 8b 8 8 5086°1 10 s.c. 10 10 Q775°1 6s 2 4 4800-1 10 s.c. 10 10 2764-0 4s. 4 6 4678°4 10 s.c. 10 10 2748°7 x 10s. 4 10 4662°7 38 9% 2 2734-0 3 1* 1 4415°9 10 s.c. 4# 6 2677-6 8 n.c 6 8 4095:0 7s 4 6 2639-6 3b 3 4 3940-4 8 s.d. 1 1 2573-1 x 10s. 4% 10 3613°0 y 8s. 10 10 2329°3 7s 0 St 3610°7 Wy 10 s.c. 10 10 2321-2 ® 8s. 0 6 3467°8 Y 10 s.c. 10 10 2313-0 v 10d. 2* 6 3466°3 Wy 10 s.c. 10 10 2306-7 ds 0 4 3403-7 x 10 s.c. 10 10 9288-1 Y 10s. 10 10 3261-2 » 8s. 10 10 2267°5 35 o | 3t 3252°6 7s 5 2 9265°1 w 10s. 8 8 3250°5 7s 5 2 2239°9 3 0 6t 3133°3 8s. 6 8 2194°7 > ds. 0 2 30854 5s 4 6 2144-5 » dsr 4 4 Zinc. Zine and its chloride give a very brilliant luminescence when heated in the quartz vacuum tube, and the introduction of the condenser makes very little difference, and does not develop the spectrum of chlorine at the * Seen with the chloride but not with the metal. + Seen with the metal but not with the chloride. Pottox—The Vacuum Tube Spectra of some Metallic Vapours. 209 temperature at which I carried out the experiment. Bands developed when no condenser was used, and there was an excess of vapour in the tube, particularly with the vapour of the metal, and they show on the plate from about 4300 to X 4100. It is a noticeable fact that in the case of zine, which gives some very characteristic lines in the are spectrum, that do not appear in the spark spectrum, not one of these lines shows with the vacuum tube spectrum even faintly on the original plate, and those so marked were carefully looked for. Principal Lines of Zinc. Vacuum Tube. Vacuum Tube. Wave ‘ , Wave 4 a Length Spark. Length Spark. No L. J. | With L. J. No L. J. | With L. J. 6364-0 10 10 10 2873-4 Are. 0 0 6103-1 10n 0 1 2863°4 Are. 0 0 6023-5 Sn 0 1 2833°1 1 1 2 5894:6 8s. 0 1 2823°3 Are. 0 0 5182-2 Are. 0 0 2801:0 | » 8 | 10 10 4926-8 10 n.d. 0 4 2781°3 Are. 0 0 4912°3 10 n.d. 0 4 2771-0 o 8 10 10 4810-7 » 10 10 10 2756°5 6 10 10 4722-8 ¢ 10 10 10 2712-6 2 2 2 4680-4 » 10 10 10 2706-6 In. 0 0 4630-1 Qn. 2 D 2684-3 Qn. 2 2 4300 2670-7 In. 1 1 = Bands. — 4100 2663-2 Are. 0 0 4058-0 2 2 4 2608-6 ia, || 6 6 3671-6 Are. 0 0 25826 Qn. 6 6 3345-5 y 10r. i 2570-0 2 1 1 10 10 3345-1 | wp l0r. 2568°0 1 1 1 i} 3303-7 | w 10x. ) 2558-0 x 10 10 10 10 10 | 3302-7 y 10r. 2516-0 2 | 1 1 3282-4 y 10 10 10 2502°1 x 10 4 10 | 3076-0 8 6 6 2491-7 In 1 1 3072-2 10 by. | 6 6 2479°9 In 1 1 3035°9 She | 6G 6 || 2393-9 ee | 0 0 3018-5 Ai, | 6 | 6 2246-9 Are 0 8 | SCIENT. PROC. R.D.S., VOL. XIII,, NO. XV. ; 21 210 Scientific Proceedings, Royal Dublin Society. THALLIUM. Both the metal and its chloride give a very intense green luminescence in the tube, and the characteristic lines of thallium sbow with brilliancy. Thallium has some very strong but discontinuous lines in the spark-spectrum of the metal in air, that is the atoms have vibrations at the electrodes that do not persist as they are shot across the spark gap. In the vacuum tube spectrum these lines do not show at all when no condenser is used, and come out quite strongly when a condenser is put in the secondary circuit. This is seen particularly well with the lines A 30919, 2430-0, and A 2298:2. The rule regarding the non-appearance of lines showing in the are, but not in the spark, also holds. Principal Lines of Thallium. Persistency, Intensity, and Character. Persistency, Intensity, and Character. ieee Vacuum Tube. nas Vacuum Tube. Spark. | Spark. No L. J. | With Ibe de No L. J. | With L. J. | | 5350°6 | 10n.r. | 10 10 2609°9 Are, 0 0 3775°9 wy 20 s.r. 10 10 2609°1 27. 2 2 3529°6 | 10s. 8 8 2580-2 3n.r. 8 8 3519-4 x 20 s.r. 10 10 2552°6 4s. 0 0 3229°9 6n. 8 8 2530°0 x) 0 8 3091°9 x 8s.d. 0 8 2469°3 5d. 0 1 2921°6 8 n. 8 8 24652°0 4 n.d. 0 2 9918-4 | @10n. | 10 10 2379°7 10r. 8 8 2826°3 2s. | 2 2 2316-0 4 0 0 2768-0 wW 6 n.r. 10 10 2298°2 aS 0 8 2710°8 Are. 0 0 2288°1 2 2 2 2709°3 3 nr. 8 8 | 2265:0 3 0 2 2665°7 3n. | 2 2 2168°7 Are 0 | Mercury. The vacuum tube spectrum of the vapour of mercury has already been carefully investigated by Eder and Valenta,’ and both lines and bands measured, but the photograph and table of wave-lengths (Plate XV.) will be found useful, as these give the lines that are certain to develop with a much shorter exposure than they evidently employed. With excess of vapour, 1 Denksch. Wien., Bd. lxi. 1894, Pottox—The Vacuum Tube Spectra of some Metallic Vapours. 211 bands develop with great freedom, especially when no condenser is used. The vapours of mercuric and mercurous chloride, so far as examined, appear to give rise to the same lines as metallic mercury when under the same condition ; the bands seen on the plate are mostly due to nitrogen accidentally present. The ultimate line of mercury is A 2536°7 and not A 2534-9, as given in my short table in the paper on “Index of the Principal Lines of the Spark-Spectra of the Elements.’”! ‘Lhe same line is evidently the ultimate line in the vacuum tube spectrum, both with and without the condenser. The lines X 2847-9 and \ 2225°7 show with the condenser, but not without it, in the case of both metal and chloride. Principal Lines of Mercury. Vacuum Table. | Vacuum Tube. ai | ES i | |) Se No L. J. | WithL. J. No L. J. | With L. J. 5804°3 10 10 LOM 3274°5 1s.br. 0 5769°6 10 10 10 | 3264-3 2 8 8 5461°0 10 10 10 3131°9 x 10b. 0 a@ 4517-1 2 s.br. 0 3131:7 | x 10b. 4396°3 3 s.b". 0 3125°8 p 10b. 10 10 4358°6 10 b. 10 10 3023°7 10 b. 10 10 4347°7 2 2 2 2967-4 x 10 10 10 4336°9 2 : 2 2925 6 2n. 4 4 4218-9 3 s.br. O= |. oeeRd 10 8 8 4120°9 8 2847°9 » 10 0 8 4115°3 8 | 2803-7 3 3 3 40781 10 10 10 27§2°9 2n. 6 6 4046°8 10 b. 10 10 2655°3 2 6 6 401775 4s.b'. 0 2653-9 2 6 6 3984-1 10 b. 10 0 2652°2 2 8 8 3728°6 2 s.br. 0 2642°7 2n. 0 0 3663°3 o 10b. 10 10 2576°3 3 3 3 3654°9 10 b. 8 8 2536°7 w 6r 10 10 3650°3 10 b. 10 10 2464°2 2 i 1 3500°1 1s.br. 0 2378°4 2 3 3 3390°5 Sn. 4 0 2292-0 2} 2 2 3341°7 10 n. 8 8 2225°7 o 2 0 4 1 Proc. Royal Dublin Society, vol. xi., p. 214, 1907. 912 212 Scientific Proceedings, Royal Dublin Society, Tin. The metal will not readily give a spectrum, but shows that of any volatile impurity, such as lead, that may be present. Stannous chloride gives a spectrum with great ease, and shows the principal continuous lines of the spark spectrum of tin with brilliancy. On the introduction of a condenser the lines of chlorine come out, and many of the discontinuous lines of the spark spectrum of tin are also seen. Principal Lines of Tin. Vacuum Tube. Vacuum Tube. Wave Bhi || Wave nani Length. P || Length. P No L. J. | With L. J. No L. J. | WithL. J. | 6453-5 10 n. 0 2 || 2788-1 In. 1 1 4585°4 8 s.d 0 4 2779:9 x 8 1 1 4524-9 10 n. 10 10 2706'6 y 10x. 10 10 3801-2 x 10 n. 10 10 ‘|| :2661°3 Qe. 4 2 36559 8 4 4 2658°9 x 10d. 0 4 3573°8 6n 2 2 2643°8 x 10 d. 0 4 3352°5 x 10 b. 10 10 2632:1 x 8d. 0 4 3330°7 10 10 10 2594°5 o 4 4 4 3283°6 x 10 db. 10 10 Q571°7 x 8n. 6 6 3262-4 x 10 ber 10 10 2546-6 x 6 6 6 3175°1 x 10 br 10 10 2495°8 > 6 6 6 3141°9 8 2 2 2483°5 x 6 6 6 3032-9 x 10 10 10 2429-6 y 81 6 6 3009-2 x 10 rv. 10 10 2421°8 x 8r 6 6 3913°6 > 8 4 4 2354:9 x 4r 4 2 2896°2 » 8a. 0 2 2334-9 ~ 2 2 1 2863-4 Y 10 d.r 10 10 2317°3 @ 2r 2 1 2850°7 » 8 8 8 2286°8 In. 1 0 2840-1 10 br 10 10 2269-0 In. 2 0 agia:7 il 6 4 4 2246-1 | » In. 1 0 Pottox—Zhe Vacuum Tube Spectra of some Metallic Vapours. 213 in the metal, though one or two bismuth lines were seen. BIsMuTH. I did not succeed in getting a good vacuum tube spectrum of metallic bismuth, the spectrum being due almost entirely to a trace of arsenic present With the chloride there was a brilliant luminescence of a deep blue colour, and this was easily maintained by the use of an ordinary Bunsen. Unfortunately a little nitrogen found its way into the tube, so the nitrogen bands are seen as well as the lines of bismuth. The introduction of a condenser did not make any notable change in the spectrum, and the chlorine lines did not develop on the plate. Principal Lines of Bismuth. Vacuum Tube. 1 Vacuum Tube. Se | se fe | = | Nol. J. With L. J.) | NoL. J. | With L.J. 4722°7 10 s.c. 10 10 29891 | » 8r. 8 8 4302°6 9 br.d 0 4 2938-4 | @ 10x. 10 10 4259°9 9 s.d. 0 8 28981 | x l0r. 10 10 4122-0 8 6 6 2855'8 6 s.d 0 4 4121-7 8 6 6 2780-6 4 nr 8 6 4079-4 10 n. 0 2 2696°8 4 8 6 3793-0 | 9 8b. 0 6 2628-0 4n 8 6 3695°6 | 10 0 1 2524-6 2b. 2 0 3596°3 | » 10s.c.r. 8 6 2515-7 1b. 1 1 35110 | @ 8 s.c. 8 8 2489-5 Are. 0 0 3397°3 | » 10r. 10 10 2276°6 2d. 2 2 3067-8 | y 10 br.c.r. 10 10 2230°7 Inr 1 1 30248 |x Sr. 10 10 2228°3 1a. 1 1 2993°5 |x 8r. 8 8 COPPER. Metallic copper was not tried, as it was not thought likely to be suffi- ciently volatile to yield a spectrum; but the chloride gave a brilliant blue luminescence in the tube, and when watched with a hand spectroscope 214 Scientific Proceedings, Royal Dublin Society. beautiful blue bands were seen to develop whenever there was an excessive quantity of vapour in the tube. The bands can be seen on the plate from about wave-length 4700 to 4100. When the condenser was introduced, there was a forked spark of a blue colour, with red border. ‘The bands were greatly reduced, and the chlorine spectrum came out on the plate. Principal Lines of Copper. Vacuum Tube. | Vacuum Tube. tee ; Spark. wes, Spark. = No L. J. | With L. J. No L. J. | With L.J. | i 5218-4 10 s.r. 8 2 2599°1 8s. 5153-4 10 s.r. A | ) 2571°2 Tn. 5105°8 8s. 8 0 2545°1 | x 10s. 6 8 4700°0 25296 | xy 8s. 6 4651°3 Ba | Sint 0 ©6©|| 2506-5 | x 10s. 6 8 4539-6 3b. 2499-2 | » 6s. 8 6 4480°5 3 aa | | 2489-8 ~ 8s. 0 2 4415-9 1b. | 2473-6 | 8s. 0 4100-0 J 2468-7 8s. 0 4062°9 7 7 1 2441-7 6s. 8 6 4022-9 4s, 7 1 || 2406-8 Ls. 1 36021 4n. 1 0 || 23928 4 33081 | xy 7s. 7 0 || 2370-0 | x1los. 10 10 32906 | » 3b. 1 0 23082 | 4s. 4 0 3274-1 y 8s. 10 10 2294-4 | Gs. 6 5 32476 | w10s. 10 10 2263°2 2b. 1 0 2961:2 | » 5s. 5 4 9947-1 | x 7s. 7 7 2824-5 | 6c. : | 6 4 || 22426 | x 7. 7 7 2766°5 2s. 2 1 2230-2 3b. 3 3 27138 | x 8s. || 2297-9 2n. 2 2 2703-5 9s. 22258 2s. 2 2 2701°3 | » 10s. 2915-4 3s. 3 3 26897 | x 10s. || 2214-6 35. 3 3 3618-5 8 8. 8 6 || 21998 3 8. 3 1 2609°4 7s. 2179-4 5s. 5 5 2600°5 | @ 10s. Pottox— The Vacuum Tube Spectra of some Metallic Vapours. 215 ARSENIC. The spark did not pass very readily with arsenic, and only with the very greatest difficulty with chloride of arsenic ; with the slightest excess of vapour the spark ceased to pass. In the vacuum tube spectra of the element the lines of zinc are seen in addition to those of arsenic. The introduction of the condenser did not make any difference to the arsenic lines, but appeared to make it more difficult for the spark to pass with the chloride. Some of the chlorine lines show without the condenser, which is unusual. Only a comparatively small number of the arsenic lines show; these, however, come out quite strongly. Principal Lines of Arsenic. Vacuum Tube. Vacuum Tube. ek i Spark. Si Levan f Spark. No L. J. | With L. J. | No L. J. | With L. J. | 3119-7 8 n.c. Onn 0 2493-0 8 8.c. 10 9 3033-0 6 8.0. 6 4 2456°6 8 s.c. 10 9 2991-2 1 0 1 2437-3 8 8.¢. 9 8 2959°8 10 n.d. 0 4 2381:3 | 8 s.c. 9 8 2898:8 2 4 8 2370°9 | 8 n.c. 1 2 28605 | @ 10s.c. 9 10 2369°7 | 8 n.c. 1 2 2831:0 8 nc. 1 0 |} 2349°9 | @ 10ne. 10 10 2780°3 x 10 ne. 10 10 | 2988-2 | » 10n.. 10 10 2745°1 10 s.c. 6 S| | | | } ANTIMONY. With antimony the spark, as in the case of arsenic, passed with difficulty, and the luminescence in the tube was of a curious straw colour, due to many lines in the orange that were easily seen by the hand spectroscope, though they have not developed on the plate with the exposure given. To get good photographs in this region would require much longer exposures, and this would fog the rest of the plate. ; ; 216 Scientific Proceedings, Royal Dublin Society. With the metal many more lines are seen than with the chloride, and when a condenser is introduced there is a considerable changein the intensity of many of the lines, and in the case of the chloride the chlorine lines develop. In the spectrum of the chloride some of the lines of cadmium show in addition to those of the element. Principal Lines of Antimony. Vacuum Tube. Vacuum Tube. ae Spark. | is Hane Spark. — at | NoL. J. | With L. J. The | No. L. J. | With L. J. | —————— 4592°4 6 n.c. 0 1 2878-0 Che BHO 10 10 4033°7 8 1 1 2851-2 8 4 6 8739°5 > 8s.d. 1 1 2790°6 x 8 1 1 3722-9 8 4 4 2770°0 8 s.¢. 8 8 3637°9 8 s.c. 8 8 2719°0 6 s.c. 6 6 3630°0 5 s.d. 0 4 2670-7 fan's 7 7 3597-7 | @ 8nd. 8 8 2598-2 | w 10x. 10 10 3504°8 6 n.d. 1 2 2590°4 anede 0 1 3498°6 6 n.d. 1 4 2528°6 x 10r. 10 10 3474°0 6 n.d. 2 6 2478°4 6 s.c. 2 2 3383°2 6 s.c. 4 4 2445°7 6 s.c. 2 2 3337°3 p 8nd. 1 1 2311°6 p 2n. 4 4 3305°0 6 s.d. 1 1 2306°6 i an, 2) 2 3267°6 gp 10 s.c. 10 10 2262°6 1 1 1 3241-3 8 n.d. 0 8 2179°3 6 n.c. ] 1 3232°6 o 8 8 8 2176°0 6n.c. | 1 1 30299 | » 6s. 6 6 ALUMINIUM. The metal will not give a spectrum in the vacuum tube, but the anhydrous chloride gives a beautiful luminescence, and the characteristic pairs of aluminium show well, both with and without the condenser. Without a condenser, and when much vapour is present in the tube, aluminium chloride gives a beautiful band from \ 2750 to A 2610, and a weaker band from ) 2610 to 2590, both having their heads at the more refrangible side, and degrading Pottox—The Vacuum Tube Spectra of some Metallic Vapours. 217 towards the red. With the condenser the weaker band disappears, the other is narrowed down, and a beautiful spectrum of chlorine is seen. The remaining lines in the plate are those of tin, accidentally present, either on the electrodes or in the chloride. Principal Lines of Aluminium. Vacuum Tube. Vacuum Tube. nee Spark. Leen Spark. No L. J. | With L. J. NoL. J. | With L. J. 3961-7 Ww 9s.c. 10 10 2660°5 x 5s.d. 0 0 3944-2 W 9s.c. 10 10 2652°6 x 5s.d. 0 0 3587°0 10 b. 0 2 2610 0 10 br. 6 by. 30930 Arc. 0 0 2590 0 4b". 0 3092°8 w 98.c. 10 10 2575:2 x 78.d. 1 | 2 3082°3 w 98.¢. 10 10 2568°1 x 78.d. 1 2 3066°3 8 0 0 2378°5 1 0 0 3064°4 8 0 0 2373°4 3060-0 1 0 0 2373-2 ores ; : 3057°3 8 by. 0 0 2372°2 2n, 0 0 3054-8 8 0 0 2367°1 2n. 1 0 3050-2 8 by. 0 0 2269-2 ? In. 0 0 3816-4 | x 10 1 1 22638 | » 1 0 0 CHLORINE. The spectrum of chlorine will be examined later, together with the spectra of a number of electro-negative elements and their compounds, but it may be stated now that hydrochloric acid gives the lines of hydrogen and chlorine, and the author has failed so far to detect any extra lines other than those due to the accidental presence of nitrogen or carbon, or the bands due to water-vapour. ‘I'he chlorine lines come out beautifully when the condenser is used, especially if the gasis heated. With metallic chlorides the chlorine lines hardly ever show unless the condenser is used, and they develop best when the vapour is highly heated, but the lines are shown much more prominently with some metals than with others. Thus, with the chlorides of arsenic, antimony, aluminium, tin, and copper, the lines are well seen, but with the chlorides of cadmium, zinc, bismuth, and mercury the lines of chlorine are not seen, or only very faintly seen, under the conditions in which the present spectra were taken. SOIENT. PROC. R.D.S., VOL, XIII.) NO. XV. ~ 2k 218 Scientific Proceedings, Royal Dublin Society. The following table gives the lines of chlorine that are most frequently seen in the vacuum tube spectra of metallic chlorides :— Principal Lines of Chlorine. ee Spark. Vacuum. Ten. Spark. Vacuum. 5443-6 8 5 bY. 4132°7 9 9 bv. 54234 9 10 by. 3861°0 10s. 5392°3 9 6D. 3851°5 8 2) 5221°5 8 6 b. 3851°2 8s.) - 5218-1 10 8 by. 3845'8 8s. 4819-6 10 9b. 3843-4 5s. OF 4810°2 10 9b. 3833-5 6 bY. 4794°6 10 10 b. 3827°8 | 5 4373'1 8 8s, 3820°4 5 4343°8 10 10 s.r. 3805°4 6 4307°6 8 8s. 3329°1 5b. 4253°6 10 10 by. 3815:5) | | 4b. 4241-5 8 by. 3306-4 3b. SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XV METALLIC VACUUM TUBE SPECTRA. Wave length Scale. 6000 5000 == | baantavtnlvidltdaiilesiliiaiy Cd I LIL 1 TT ae Tepe iid | II i il I ie | | | ee ee Cd Cl; aH EE TA Al | 5 lerdal | POE Et | | . Zn illl eal HI iif af | zr iil fi || | I a et ZnCl, | aa a Wes as " | LT tea (Pia eescalan ets Tl i a eee | HM " | Lo ea it | Hg PTS UST see eT eleaa | : | TEE Wey) i i | | | | | Hg Cl, | Tt | | ” HM SM | Sn LLL a A) at Sn Cl, | HE I A ee A th Al Bi TEA I CT i a Bi Cl, | HP AEE MM i OE I Bil ii | Cu asda al ae peel Cu Cl, | Ma Kael er | HM! 0 II N TMM Ee & tk Be Oo As oe EST: Ln ee ;s If. ) Il (lat As Cl, | | | Sb prmerereer i000 80711000081 10 | mV TAROT Da TO | i i I " LS Sane A A ey ee I Te gd @ddmdd n E on Sy SO og Gs Og 4 2d 2 2 oO ae fae a Boa Gg & 29 Gk; Wmenieeennt ell tll iat ” | re Vv = a ia ie el ! S ae} I | | | | a V SCIENT. PROC. R. DUBLIN SOC., N.S.. VOL. XIII. PLATE XVI. QUARTZ VACUUM TUBE AND STAND. SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1. A Seed-Bearine Ivish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. 2. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcz H. Pxrruysringe, B.Sc., PH.D. (March, 1911.) 1s. 8. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witutam Brown, B.so. (April 15, 1911). 1s. 4, A Thermo-Hlectric Method of Cryoscopy. By Henry 4. Dixon, se.p., F.R.s. (April 20, 1911). 1s. 5, A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrtu1am J. Lyons, B.a., a.R.c.sc. (LonD.). (May 16,1911). Gd. 6. Radiant Matter. By Joan Jouy, sc.p., r.R.s. (June 9, 1911.) Is. 7. The Inheritance of Milk-Yield in Cattle. By James Witson, M.a., B.SC. (June 12, 1911.) 1s. 8. Is Archxopteris a Pteridosperm? By T. Jounson, v.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. 9. The Occurrence of Archaopteris Tschermaki, Stur, and of other Species of Archezopteris in Ireland. By T. Jounson, p.sc.,¥.u.s. (Plates VIL, VIIL) (June 28, 1911.) 1s. 10. Award of the Boyle Medal to Proressor Joun Jouy, m.a., so.D., F.R.S. (July, 1911.) 6d. 11. On the Amount of Radium Hmanation in the Soil and its Escape into the Atmosphere. By Joun Joty, sc.p., F.x.S., and Louis B. Smyru, B.A. (Plate IX.) (August, 1911.) 1s. 12. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newent ARper, M.A, F.LS., F.G.S. (January, 1912.) 1s. SCIENTIFIC PROCEEDINGS—continued. 13. Forbesia cancellata, ger. et. sp. nov. (Sphenopteris, sp., Baily). By T, Jounson, D.sc., F.L.s. (Plates XIII. and XIV.) (January, 1912.) 1s. 14. The Inheritance of the Dun Coat-Colour in Horses. By Jams Winson, m.a., B.Sc. (January, 1912.) 1s. 15. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jamrs H. Porzok, psc. (Plates XV. and XVI.) (February, 1912.) 1s. DUBLIN: PRINTED AT fHE UNIVERSITY PRUSS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 16. FEBRUARY, 1912. CHANGES IN THE OSMOTIC PRESSURE OF THE SAP OF THE DEVELOPING LEAVES OF SYRINGA VULGARIS. BY HENRY H. DIXON, Sc.D., F.R.S., UNIVERSITY PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN, AND W.R. G. ATKINS, M.A., ASSISTANT TO THE PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN. {Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBUIN SOCIETY, LEINSTER HOUSE, DUBLIN.’ WILLIAMS AND NORGATE, Paeconianine M4, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. / ae 1912. Price Sixpence. Roval Dublin Society. PA eee FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tue Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. L 2le | XVI. CHANGES IN THE OSMOTIC PRESSURE OF THE SAP OF THE DEVELOPING LEAVES OF SYRINGA VULGARIS. By HENRY H. DIXON, S&c.D., F.RB.S., University Professor of Botany, Trinity College, Dublin ; AND W. R. G. ATKINS, M.A., Assistant to the Professor of Botany, Trinity College, Dublin. [Read January 23. Published Fesrvary 21, 1912.] Previous experiments in determining the osmotic pressures of the saps of plants! showed that in one and the same plant the pressure may vary within fairly wide limits. For example, the osmotic pressure of the sap of Syringa vulgaris was found to vary between 26°87 atm. and 11:57 atm. In the cases examined it was found that external conditions—especially those controlling carbon assimilation, respiration, and the hydrolysis of carbohydrates—effected the most important changes in the osmotic pressure. In addition to the changes due to external conditions, it was found that the age of the leaves from which the sap was taken also influences the osmotic pressure—the younger leaves having a lower osmotic pressure than the more mature. Observations of this rise in osmotic pressure with age have since been extended to the leaves of some evergreens, viz., [ler Aquifolium and Hedera Helix. The following experiments were carried out with the view of tracing the changes in the osmotic pressures during the unfolding of the buds and the maturing of the leaves. The buds and leaves of Syringa vulgaris were selected for the work. All the samples used were taken from a group of plants growing in a sheltered position in Trinity College Botanic Gardens. ‘The osmotic pressures, asin the previous work, were obtained from the freezing-points of the saps determined by the thermoelectric method of cryoscopy’ already 1H. H. Dixon and W. R. G. Atkins: ‘On Osmotic Pressure in Plants ; and on a Thermoelectric Method of Determining Freezing-Points.’’ Proc. R.D.S., vol. xii (N.S.), No. 25. 2H. H. Dixon and W. R.G. Atkins, loc. cit. SCIENT. PROC. R.D.S., VOL. XIII., NO. XII. 2u 220 Scientific Proceedings, Royal Dublin Society. described. It may be pointed out that the osmotic pressure determined in this manner is the osmotic pressure of the sap at 0° C., and consequently will be somewhat lower than the osmotic pressures determined by the plasmolytic method, which are usually measured at about 15°-20° C. Buds of Syringa vulgaris gathered during the autumn of 1909 and during the winter 1909-10 yielded no sap, or at least none in sufficient quantities for the experiment. Consequently, during that period no determinations were possible. It was not till February 19, 1910, that a sufficient amount (viz., about 2 ¢.c.) could be pressed from a handful of buds. With this date the determinations begin. The following table shows the depression of freezing-point A, the osmotic pressure P calculated from it, and the mean molecular weight M of sub- stances dissolved in the sap. ‘he last figure is derived from the depression Date. Description oF MATERIAL. A. 1B, M. 1910. | Feb. 19 | Buds, 0 0 0 6 4 . | 07930 | ISU) _— op 8 | Buds same : 5 5 5 - | 10381 | 12°40 166 Morano | Bw bo SS ye eae || meat | aia sy TD Wels, cs. F , a. a | alen@n. | ASMP || of MEN WER, ede ee a ORES imap | | April 6 | Young leaves from opening buds, . | 0°965 | 11°60 176 sp @ | Older leaves from opening buds, . | 0-829 | 9:97 | 173 py ee | Young leaves not 2 ems. long, a || Orgity | 11:08 152 5 Older leaves more than 2 cms. long, | 0:838 | 10-08 164 | May 2 Leaves not fully grown, . . | 07839 | 10°10 — | Ls Leaves apparently full grown, '. | 0-873 | 10°50 = » 30 ” » ” p 9 0-986 | 11:86 | 192 | June 20 rs Fa a a 0 |) HOURS || EHS |) He 1909. | Sept. 14 | Mature leaves, : : 5 - | 13810 | 15°45 = Oct. 25 | Yellowish leaves ready to fall, *. | 1:215 | 14°61 — of the freezing-point and the dry weight of the dissolved substances. When no molecular weight is given, the expressed sap was too viscid to allow of the removal of colloids and undissolved substances by filtration. Consequently, it Dixon anp Atxins— Changes in Osmotic Pressure, Se. 221 was not feasible to determine the weight of the dissolved substance. Attempts were made to remove the undissolved matter by centrifuging, but the speeds then accessible—viz., 2000-4000 revolutions per minute—were insufficient to clear the sap. Subsequently it was found possible to clarify the sap in a centrifuge giving 9000 revolutions per minute. This machine was obtained too late to be utilized in the present research. From the foregoing table it will be seen that the osmotic pressure of the sap of the buds rose from February 19th up to March 12th. It seems rational to attribute this rise to the transport of dissolved substances into the buds, and to the solution of previously undissolved bodies in them. On March 19th, while the older leaves of the buds were still cohering, the pressure of the sap of the buds taken as a whole was 11°49 atm. (A = 0°955°). As the buds opened and the leaves expanded it was possible to obtain the freezing-poimt of the sap of the older leaves apart from that of those still cohering in the bud. On April 6th the older leaves had an osmotic pressure of 9:97 atm. (A = 0°829°), while in the younger leaves still cohering together in the buds the osmotic pressure was 11:60 atm. (A=0:965°). On April 22nd the older leaves, which were now over 2 em. long, hada pressure of 10:08 atm. (A = 0°838°), while those from the same buds which were less than 2 cm. in length had a pressure of 11°03 atm. (A = 0°917°). The rapid increase in size during the beginning of April was associated with a dilution of the sap, indicating that during this expansion the absorption of water predominated over the accumulation of dissolved substances. At the end of April assimilation and transpiration more than counterbalanced the absorption of water, and the osmotic pressure rose to 10°08 atm. From that on, as the leaves grew and matured, the pressure continued to rise, until in June the pressure attained 13°56 atm. (A = 1:128°). Here this series of observations had to be brought to a close. Observations on mature leaves of Syringa in the preceding year make if probable that the pressure continues to rise in the leaves during the summer. These observations made on leaves from plants grown in a similar position indicate an average osmotic pressure for the month of September, 1909, of 15:45 atm. (A =1:310°). Such a rise also is to be expected owing to the accumulation of electrolytes during continued transpiration and to the increased efficiency of the leaf in the production of carbohydrates. ‘Towards the end of the season it seems probable that the pressure due to the former class of dissolved substances amounts to almost 11:5 atm.—a pressure which was twice found in Syringa leaves after they had been screened from the light for several days, and in which it is improbable that any assimilation products contributed to the osmotic pressure. 222 Scientific Proceedings, Royal Dublin Society. The mean molecular weight of the dissolved substances seems to point to an increase in the amount of dissolved carbohydrates as being partly responsible for the rise in osmotic pressure. The dissolved substances in leaves from a similar position during the month of September, 1909, had a mean molecular weight of 238. ‘This indicates a further rise in the amount of dissolved organic constituents of the sap during the late summer After the final rise of osmotic pressure in the late summer a diminution in the osmotic pressure was registered in the sap from leaves just about to fall. This diminution may be attributed to the transport of materials from the leaves. ie 10. ial, 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearinge Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.sc., F.1.S. (Plates I-III.) (March, 1911.) Is. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. >By Grorcz H. Prtuysrives, B.sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wituram Brown, B.sc. (April 15, 1911). 1s. . A Thermo-EHlectric Method of Cryoscopy. By Henry H. Dixon, sc.p., F.R.s. (April 20, 1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wiut1am J. Lyons, B.a., a.R.c.sc. (LonD.). (May 16,1911). 6d. . Radiant Matter. By Joan Jony, sc.v., F.R.s. (June 9, 1911.) 1s. . The Inheritance of Milk-Yield in Cattle. By James Witson, M.a., B.SO. (June 12, 1911.) 1s. . Is Archzopteris a Pteridosperm? By T. Jounson, p.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermakt, Stur, and of other Species of Archeopteris in Ireland. By T. Jouwson, D.sc.,F.u.s. (Plates VII., VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Proressor Joun Joty, M.a., sc.D., F.R.S. (July, 1911.) 6d. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By ,Joun Joty, sc.p., F.x.s., and Lours B. Smyru, B.a. (Plate IX.) (August, 1911.) Is. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By HE. A. Newsnn Arper, ma, F.LS., F.G.S. (January, 1912.) 1s. 13 16 SCIEN TIFIC- PROCEEDINGS—continued. . Forbesia cancellata, ger. et sp. nov. (Sphenopteris, sp., Baily). By T, Jounson, D.sc., F.u.s. (Plates XIII. and XIV.) (January, 1912.) 1s. . The Inheritance of the Dun Coat-Colour in Horses. By James Winsov, m.a., B.sc. » (January, 1912.) 1s. . On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jamms H. Pottog, p.sc. (Plates XV. and XVI.) (February 21, 1912.) 1s. . Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Drxon, sc.p., r.z.s., and W. R. G. Arxins, ma. (February 21,1912.) 6d. : DUBLIN: PRINTED AT fHE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.8.), No. 17. MARCH, 1912. IMPROVEMENTS IN EQUATORIAL TELESCOPE MOUNTINGS. BY SIR HOWARD GRUBB, F.R.S., VICE-PRESIDENT, ROYAL DUBLIN SOCIETY. (PLATES XVII.—XIX.) | Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. ' WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. e aon 1912. [sx Price One Shilling. Latin a, Roval Bublin Society. OO a a FOUNDED, A.D. 1781. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.80 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be get down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Llustrations in a complete form, and ready for transmission of the Hditor. [ 2B XVII. IMPROVEMENTS IN EQUATORIAL TELESCOPE MOUNTINGS. By SIR HOWARD GRUBB, FE.RS., Vice-President, Royal Dublin Society. (Puates XVII.-XIX.) [Read Novemper 28, 1911. Published Marcu 26, 1912.] Anti-Fricrion ARRANGEMENTS FoR PoLAR AND DrciinaTIon AXES OF Heavy HevaroriaL InsrRuMENTSs. Polar Azis:—The great improvements in the manufacture of ball and cylinder bearings of late years, owing to the general adoption of this form of anti-friction apparatus for so many purposes, has naturally led to its adaptation to large equatorial mountings, and in the most up-to-date instruments we have adopted a necklace or ring of hardened steel rollers for the large upper bearing of polar axis where nearly all the friction takes place, and a ring of balls running between hardened steel plates for the end thrust. The side-thrust on lower bearing of polar axis is so slight (the instrument being nearly balanced on the large upper bearing), and the axis itself is so small here in diameter, that there is no necessity to apply any apparatus to relieve the lateral friction on that pivot. It should be premised that, as the two essential features sian require to be kept in view are those of precision of motion and freedom of motion, the general principle adopted is to allow the axes to revolve on or in Y bearings, but to relieve these bearings of about 19/20ths of the weight by some efficient anti-friction arrangement, leaving only the remaining 1/20th to ensure the - necessary precision of movement. Attempts have been made to carry the axes of equatorial instruments entirely on friction wheels or rollers; but while this ensures the condition of freedom of motion, it does not provide for the necessary precision, whereas, by adopting the combined system of Y bearings coupled with tho anti-friction rollers, both conditions are fulfilled. The single roller under the large upper bearing of polar axis used in the older instruments is therefore now replaced by a necklace of live rollers of hardened steel rolling on the inside of a ring of hard metal as shown in figs, land 2, Plate XVII. (See p. 228.) SCIENT. PROG, R.D.S., VOL. XII., NO. XVII, 2u 224 Scientific Proceedings, Royal Dublin Society. This system, while giving even greater freedom of motion than the old single roller, has the additional advantages that it rarely requires lubrication, and that the weight being distributed among several rollers there is not so much tendency to wear grooves on the rolling surfaces. Declination Awis.—The relief of friction for the declination axis of an equatorial telescope mounting suitable for any latitudes except those near the Pole is a much more complicated and difficult problem, as a little consideration will show. Suppose the latitude to be, say, 45° north, and that fig. 1, Plate XVIII, represents an end view of declination axis in its bearings viewed from the east in north latitude—A and B being the bearings—it will be evident that in this position the bearing B is taking the entire weight, while A has none to bear; while if the telescope is turned half round on axis P, P’, so that the tube be on the other side of the pier, the bearing A will be receiving all the weight and B none, as in fig. 2, Plate XVIII. While in the six-hour position, half-way between, the weight will be equally distributed between A and B. Any arrangement, therefore, to relieve the weight in the first instance by an upward thrust from B to C would act in a totally wrong direction when the telescope is turned to the other side of the pier. The problem is, therefore, much less simple than that of the polar axis, in which case the direction of gravity bore a fixed relation to the position of the Y bearings. As far as I am aware, my father was the first to attempt to provide means for satisfying these conditions, and on this principle :—In fig. 3, Plate X VIII., the force of gravity acting in the direction C W, instead of being resisted by an upward thrust represented by the diagonal D C of the parallelogram, could be equally well resisted by two forces represented respectively by the sides of the parallelogram A C and B C, of which one A Cis constant in its direction, irrespective of the revolution of the polar axis. He therefore used an arrange- ment of this nature :—figs. 4, 5, and 6, Plate X VIII. :—The upper end of the - polar axis is closed by a plate ee, having a hole in the centre ; G, Gis the cross- head; #’the declination axis ; 7, fis a strong, steel, fork-shaped casting of a T section, and partially surrounding the declination axis; this fork, / 7, is carried on the end of a steel bar X which passes through the hole in the plate e e loosely, and, projecting down through the polar axis, carries a series of heavy weights, W. This steel fork, / /, carries on its extremities two gun-metal blocks which serve as carriers for three rollers each ; two of these rollers, rr, at each side roll against turned rings on the declination axis provided for the purpose, while the two rollers, y y, roll freely in a groove prepared in the axis between the two rings. In the case of an equatorial at the Pole, of course, this apparatus would Grusp—IJmprovements in Equatorial Telescope Mountings. 225 be inoperative, as the bar X would then hang vertically ; nor, as we have seen before, is it required. In every other latitude, however, it will be seen that the heavy weight JV acting on the lower end of the lever X, pivoted in plate e e, exerts a force on the axis exactly counterbalancing the component B C in fig. 3; and, furthermore, that this apparatus, though attached to and carried by the polar axis, exerts a force whose direction is constant as regards gravity, but variable as regards the polar axis, &c. When the instrument is to the east of the pier, one set of rollers acts; when to the west, the other set—whichever happens to be below; and in a position six hours off the meridian, the pair of rollers Y act and take off the end pressure of the axis. Having disposed of the component B C, fig. 3, Plate XVIII., we are prepared to deal with the other component A C. This is easily managed, for its direction is constant as regards the polar axis and cross-head. At d, b, b’,U’, figs. 4, 5, and 6, Plate X VIIL., are placed a pair of bracelets (so-called), i.e., frames carrying rollers, and these are connected together by two side levers centred at # at each side of the centre of cross-head, the amount of force being regulated through the nut h, by screwing up which the whole declina- tion axis, telescope, counterpoises, &c., can be lifted out of the Y bearings, and the weight of all transferred to the fulerum H. In practice, as with other bearings, a sufficient portion only of the weight is lifted, and the remainder is allowed to rest on the Y bearings. The application of these “bracelets” would not be possible until the internal arrangements mentioned above are first brought into action. The system above described is good in principle, and has been applied with success to many equatorial mountings; but practical difficulties have arisen in applying it to the newer, and, more particularly, to the larger, forms of equatorial mountings, one of the principal being the difficulty of getting a sufficient amount of weight on the internal lever. This weight being neces- sarily inside the polar axis is limited in its size, and, moreover, there is no possibility of getting the fulerum high enough to obtain a fair leverage, as the declination axis itself comes in the way. Various modified forms of this anti-friction arrangement have been tried. I shall confine myself to a description of the latest form, which I have adopted for all the later instruments of large size, as it leaves little to be desired. In this form, figs. 1, 2, and 3, Plate XIX., the centre of gravity of all parts that turn with the declination axis (i.e., the telescope itself, cradle, declination axis, &c.) falls very near where the larger anti-friction ring or bracelet surrounds the axis, so, there being very little weight on the smaller bearing at the other end, and the axis here being small in diameter, there 2u 2 226 Scientific Proceedings, Royal Dublin Society. is no occasion for any second anti-friction ring or bracelet, but a double set of ball bearings is mounted, 0 b, outside this smaller bearing to take the end- thrust and relieve any friction that might be due to this. The one bracelet, B B, shown in section in fig. 2, Plate XIX., which con- tains the live rollers, surrounds the neck of the declination axis near the centre of gravity, and has cast on it two lugs; one of them, Z, the lower, has a hole drifted in it which strings upon a pin attached to the cross-head and fitting it in the direction of xr, but slotted in the direction of y y, so that the ring or bracelet is capable of a small amount of motion in the direction y y of the polar axis. A lever I, centred on the cross-head at C, applies (as to its shorter end) against the lower side of this lug, while the longer arm of the lever is carried to a convenient distance, and is furnished with a pushing screw P, which bears on a lug attached to the cross-head. When this lever is brought into action by forcing up the screw, a pressure is exerted on the lower side of the bracelet which lifts on the rollers that component of the weight which is represented by the line ac, in diagram fig. 3, Plate XVIII., and which is constant in direction as respects the polar axis. On the upper side of the bracelet is another lug with a hole, into which applies the shorter arm of another lever VV J, centred on a pin C’ and working in a plane at right angles to the first described lever. The longer arm of this lever extends beyond the central cube, and has fixed upon it a heavy counterpoise WV. When the telescope is in the six-hour position, this lever is non-effective, i.e., it is not exerting any force one way or another. All the weight carried by the declination axis is then divided between the lever I/ under the cross- head and the thrust ball-bearings at the end of the declination axis. If, how- ever, the instrument be turned to east or west, the lever V on the top begins to act, and its effect increases in precisely the correct ratio as the telescope is turned, till the meridian position is reached, when the thrust on the end- bearing becomes nil (as the axis is horizontal), and all the weight is divided between the lever JZ below and the lever WN above the cross-head. If the telescope be turned to the other side of the pier, the top lever acts in exactly the opposite direction. If the weights be properly siete Hint and the levers properly set, all the weight of the declination axis and the telescope it carries (with the exception of a few lbs. left on Y bearings to ensure steadiness) can be carried on the rollers of this “ bracelet.’’ Grusp—Improvements in Equatorial Telescope Mountings. 227 ImprovepD ARRANGEMENY OF DIFFERENTIAL Hour-CircLEs FOR HaQuatortaL ‘l'ELESCOPES. The position in the heavens of any celestial object at any given moment is determined by :— (a) Its declination (that is the number of degrees, ete., north or south of the Equator) ; (0) Its R.A. (that is, its angular distance from a certain fixed point in the heavens measured in a direction parallel to the Equator) ; and (c) The time as shown by the sidereal clock. Setting a telescope in declination is comparatively simple, because the instrument has only to be turned until the correct declination is read upon the declination circle ; but setting in the other direction is not so simple, because it depends upon two quantities, that of its right ascension and the time as given by the sidereal clock at that particular moment. As this time is con- tinually varying, the setting in this direction is more complicated than in the direction of declination. Ifa single circle be used, the reading of that circle from a fixed vernier should be the difference between the time as given by the sidereal clock and the A.#. of the star. This involves a reading of the clock and an arithmetical operation for every setting, which is troublesome in an observatory; and to avoid this trouble a device was introduced (I think by the late Sir George Airy) of a second circle, which was strung loosely upon the axis, and could be set from a fixed vernier to read the time as given by the sidereal clock. Differential readings between this and the circle fixed to the axis would give true 4.#.s, without the troublesome arithmetical computation. As, however, the setting of this differential circle (which should always read sidereal time) varies from minute to minute, the device was adopted of connecting it to the main driving clock of the equatorial, so that when once set for sidereal time it would still read, at any other time of the night, true sidereal time, as it was carried round by the clock-work at the corresponding rate. So long as that circle was kept moving round by the equatorial clock differential readings between the two circles would give the correct A.R. of any star that the telescope was pointed upon without the arithmetical operation of subtraction. In other words, it formed a mechanical subtraction machine.. This is the form that is usually adopted in modern equatorial telescopes. There are objections, however, to this arrangement. Most telescopes are driven by a sector or portion of a circle only ; and this has to be wound back at 228 ‘ Seientifie Proceedings, Royal Dublin Society. the end of its run; consequently its differential circle has to be re-set every time the sector is wound back, or at any time the clock is stopped. There is a second objection also, that the vernier by which this circle is read varies its place from time to time, and may be anywhere round the circle ; consequently it is less convenient to read than a fixed vernier, more especially in the case of large instruments, where it is necessary to read these circles through a microscope from a distance. In the large equatorials which are now being built for Johannesburg and Santiago, an arrangement has been made at the suggestion of Sir David Gill, F.R.S., by which this differential circle is kept continually moving in the proper direction—not by the main clock of the equatorial itself, but by a series of electrical contacts from the sidereal clock of the observatory. So long as these contacts act perfectly, this completely obviates the first objection above mentioned; but there is still the objection remaining that the vernier is to be found in various positions round the circle under different circumstances. I have therefore devised another form in which this objection is avoided. In this last form (see fig. 3, Plate XVII.) the differential circle is caused to travel backwards as regards the polar axis, by a piece of clockwork which is carried upon the axis itself, and in this way it is possible to read the actual A.R. of a star from a fixed vernier without any reference to the sidereal clock, and this small subsidiary clock which is carried upon the polar axis is always acting, whether the telescope is in use or not—or whether the main clock is working or not—so, as long as this is kept wound up and going, the instru- ment can be set to actual A.R. without reference to the sidereal clock, and thus avoids both the objections mentioned above to the existing forms. Description or Fie. 3, Prars XVII. AA. A.R. circle read by vernier V for actual right ascension, and also by vernier v (which is carried on an arm fastened to the polar axis) for sidereal time. The 4.2. circle 44. is strung loosely on the boss of the disc D.D., so that it can be set to correct reading at any time, after which it is kept revolving backwards on the polar axis by the independent piece of clockwork and escapement C, the driving force of which is a weight attached to a cord passing round the V-grooved circle f/f. SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XVII SVL ZLLB Ba Y SN lane, Y) = AANA : : we 4 4 ia Y Yj a Lo 19a. SN ZL KSEE Gas oa 4 po VLLLLLILLL LL g D1J g (OI 6 (9IY ] ‘SIA y Oly SG. GSS SSS 4 KS My a y- - SH - is aie eee Se TAX ALV Td JIIX “IOA “S'N “OOS NITANG “YM OONd “LNAIOS —____— — ZI 1 SI cm amt TILE. e aa Gaia Z B SQOX XS AAAS L WY Sees PE Sv 5S S 4 "% a Ju SSNSKIA I» lll “XIX ULV1d THX “IOA ‘S'N “OOS NITHNG “A “OOUd “LNAIOS SCIENTIFIC PROCEEDINGS. VOLUME XIII. 1. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. 2. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorce H. Prruysrince, B.sc., PH.D. (March, 1911.) 1s. 8. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wituram Brown, B.sc. (April 15, 1911). 1s. 4. A Thermo-Electrie Method of Cryoscopy. By Henry H. Drxon, sc.p., F.R.s. (April 20, 1911). 1s. 5. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wruu1am J. Lyons, B.a., A.R.c.so. (LonD.). (May 16,1911). 6d. 6. Radiant Matter. By Joun Jony, sc.p., F.R.s. (June 9,1911.) 1s. 7. The Inheritance of Milk-Yield in Cattle. By James Wruson, M.A., B.SC. (June 12, 1911.) 1s. 8. Is Are ropteris a Pteridosperm? By T. Jounson, v.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 64d. 9. The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Avchzopteris in Ireland. By T. Jounson, p.sc.,F.u.s. (Plates VIL, VIII.) (June 28, 1911.) 1s. 10. Award of the Boyle Medal to Proressor Joun Joy, M.A., SC.D., F.R.S. (July, 1911.) 6d. 11. On the Amount of Radium Hmanation in the Soil and its Escape into the Atmosphere. By Joun Jony, sc.p., F.x.s., and Lours B. Smyru, B.a. (Plate IX.) (August, 1911.) 1s. 12. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By HE. A. Newent ARBER, M.A., F.L.S., F.G.S. (January, 1912.) 1s. 18. 14. 15. 16. 17. SCIENTIFIC PROCEEDINGS —continued. Forbesia cancellata, gen. et sp. nov. (Sphenopteris, sp., Baily). By T. Jounson, D.sc., F.L.s. (Plates XIII. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Witson, M.A., B.SC. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I1.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Pottox, p.so. (Plates XV. and XVI.) (February 21,1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, sc.p., r.n.s., and W. R. G. Atrins, ua. (February 21,1912.) 6d. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, res. (Plates XVII.-XIX.) (March 26, 1912.) 1s. a DUBLIN: PRINTED AT CHE UNIVERSULY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 18. APRIL, 1912. VARIATIONS IN THE OSMOTIC PRESSURE OF THE SAP OF IJLEX AQUIFOLIUM. BY HENRY. H. DIXON, ScD., F.RS., UNIVERSITY PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN, AND W.R. G. ATKINS, M.A., A.LC., ASSISTANT TO THE PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN. [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIBTY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. \ Price Sixpence. Roval Dublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749. RVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. [29 4 XVIII. VARIATIONS IN THE OSMOTIC PRESSURE OF THE SAP OF ILEX AQUIFOLIUM. By HENRY H. DIXON, 8c.D., F.R.S., University Professor of Botany, Trinity College, Dublin; AND W. R. G. ATKINS, M.A., A.I.C., Assistant to the Professor of Botany, Trinity College, Dublin. [Read Fepruary 27. Published Aprin 9, 1912.] Previous observations have brought to light considerable fluctuations in the osmotic pressure of the sap of the leaves of plants during short intervals of time. Further, it has been shown that, other conditions being equal, a difference is observable between the osmotic pressure of the sap of leaves of different ages.! The present research was undertaken to ascertain if there was a periodic fluctuation in the osmotic pressure corresponding with seasonal changes. The materials selected for the investigation were the leaves of two evergreens Ilex Aquifolium and Hedera Helix, so that a continuous series of observations might be made throughout the year. In the case of Iles Aquifolium the leaves examined were growing in the open in Trinity College Botanic Garden, all taken from the same individual, and from off the upper branches, 3-4 metres from the ground, so that they were exposed to as uniform external conditions as possible. ‘he leaves were gathered for each experiment between 9 and 10 a.m. For the sake of comparison measurements were also made on the sap of the roots. The observations on Hedera Helix are recorded in a subsequent note. Former observations had shown that the sap from the young leaves of various plants has as a rule a smaller depression of freezing-point than that of the mature leaves. Experiments on Ilex showed that the same rule held good in its case; for usually the young leaves of this plant have asap with a smaller depression, and consequently a lower osmotic pressure than that of the mature ones. 1 On Osmotic Pressures in Plants, and on a Thermo-electric method of Determining Freezing- Points.”” Dixon and Atkins. Sci. Proc. Roy. Dubl. Soc., vol. xii, pp. 275, et seq. SCIENT,. PROC. R,D.5., VOL. XII., NO. XVIII, 2N 230 Scientific Proceedings, Royal Dublin Society. To quote examples illustrating this point :— Taste I. Llex Aquifolium. Date. Description of Sample. | A | 12, M 1910 June 20} Young leaves, Q 0 c 6 0 . | 0:706 | 8:49 | 245 20 | Leaves of penultimate growth, : 3 a || Ose 10°49 236 | Sept. 23 | Young leaves, : : : 2 : . | 0-713 8°57 278 23 Mature leaves, A B : : 5 || Oxsple/ 9°82 235 Oct. 5 | Young leaves, . . . : 6 - | 0-608 6-98 — Bl iteamaene, | ee a PE EG Eoin | ee fe | Oct. 15 | Young soft leaves, . 0 0 6 é of] WP 8°56 240 15 | Mature leaves of penultimate growth, . . | 0-935 | 11-25 — 15 | Mature leaves of antepenultimate growth, - | 0-982 | 11-81 — Oct. 24 | Young leaves, soft, light green, : 6 . | 0°624 7°80 260 24 | Mature leaves of antepenultimate growth, - | 0°949 11:41 300 | In this table, as throughout the paper, under A is given the depression of freezing-point observed by the thermo-electric method, under P the osmotic pressure caleulated from it and under J/ the mean molecular weight of the dissolved substances producing the osmotic pressure, calculated from the dry weight of the dissolved substances in a certain weight of sap and from the freezing-point. It may be noted here that the osmotic pressures calculated in this way will be somewhat lower than those obtained by the plasmolytic method, as in this case the osmotic pressure is that which the dissolved substances exercise at 0° C., while when measured by plasmolysis the osmotic pressure found is that exerted at ordinary room temperature, viz., about 15° C. With regard to the mean molecular weight of the dissolved substances, the presence of colloids which are not removed by filtration will tend to make our determinations too high. In any case the method for deter- mining it, the usual chemical method, is not one of great accuracy; and Drxon ann Arkins— Variations in Osmotic Pressure, §e. 231 it is only recorded in order to give some idea of the relative amounts of disaccharides present. Not only is there a difference observable between mature and immature leaves, as appears from the table above, but also between mature leaves of various ages considerable differences are found, as shown in Table II. The branches of Ilex seem normally to make two growths in the year. The limits of these growths are defined by a crowd of small scars. Leaves may be found on the last four or, in small numbers, on even the last five growths. Taste II. Tlex Aquifolium. Date. Description of Sample. A. P. M. Oct. 25 | Mature leaves of ultimate growth, . 5 5 |}, Worden 9°16 254 25 | Mature leaves of penultimate growth, . . | 0°864 10°38 262 - Noy. 1 | Mature leaves of penultimate growth, . - | 0°788 9°48 233 1 Mature leaves of antepenultimate growth, . | 1:020 12°26 267 | This rise of the cryoscopic value of the sap will further very clearly be seen from the averages given on page 233, for the saps of the leaves from successive growths. This variation of the osmotic pressure with the age renders the comparison of the pressures at different seasons more difficult, and makes it necessary to compare the pressures of the sap of leaves of the same age. In order to make this possible on each date separate determinations were made on the saps derived from the leaves of the last three growths. The leaves of the last growths were further subdivided, and separate determina- tions were made on the sap from the ultimate three and from the penultimate three of these latest growths. In the following Table (No. III) the depression of the freezing-point (A) and the osmotic pressure (P) is given for each sample dealt with; and in the last pair of columns the depression and the pressure of the sap pressed from the roots is added. In order to eliminate as far as possible errors arising from water adhering to the surface of the roots, on each occasion, before pressing the sap, the roots were dried by drawing them repeatedly through air-dried soil. 2n2 232 Scientific Proceedings, Royal Dublin Society. Taste II].—-Llex. Date Ultimate leaves of | Penultimate leaves|| Leaves of pen- || Leaves ofantepen- Roots: 4 ultimate growth. |/ofultimategrowth.|| ultimate growth. || ultimate growth. 1910 A. P. A. P. A. P, A. P. A. i. Oct. 5 || 0-608 | 6-98 |] 0-672 | 8-09 8 | 0-461 | 5:55 15 0-712 8°56 || 0°935* | 11-25 0-982 11°81 24 0-624 7750 0-682 8-20 0-949 11-41 25 0-761 9°16 0-864 10°34 0°605 7:28 Noy. 1 0°842 10°13 0-788 9°48 1-020 12°26 0°528 6°35 18 0°800 9°62 0°827 9°94 0°365 4°39 21 1:020 12:26 1:061 12°75 28 0°747 8:99 0°735 8°84 0°846 10°18 0-940 11°31 Dec. 6 0-683 8:22 14 0°757 9°10 0°962 11°62 1-060 12°75 0°469 5°64 22 0-826 9:94 0°894 10°75 1-060 12°75 28 0-969 11°66 0-940 11°30 1911 Jan. 2 0-916 11°02 0-880 10°58 0-853 10°26 0-966 11°61 11 0°715 8°61 07838 10:08 0°807 9°70 0-999 12°01 0°427 5:13 27 0-686 8-26 0°727 8-74 0°895 10°71 0-712 8°61 Feb. 1 0-709 8°53 0-605 7:27 0-742 8-93 0-614 7°39 10 0-726 8°73 0°847 10°19 0°846 10°19 0-901 10°84 0-699 8:41 22 0°735 8°81 07641 7-70 0°72 9-29 0°903 10°86 Mar. 6 0-696 8°37 0°678 8°15 0-890 10°71 23 0-916 11-00 0°932 11°21 0°956 11:48 07884 10-64 April 6 0°851 10°24 0-888 10°68 0-944 11°35 0-615 7°39 18 0-648 7:79 0-747 8-99 0-839 10710 0-692 8°32 May 3 0-791 9°51 0-731 8-79 0-868 10-44 0-662 7:99 24 || 0-707 8-50 0-718 8°64 0-811 9°76 0-696 8-38 June 13 0°932*| 11-21 0-879 10°57 0-909 10°94 0°870 10°44 July 1 || 0°780+ 0-730T 0-772 9-29 0-502 6°02 Aug. 8 || 0-683 | 8-21°|| 0-734 | 8-82 || 0-836 | 10-06 0-729 | 8-77 28 0-749 9-01 || 0-757 9°22 0°797 9°50 0:903 10°85 Sept. 25 0-691 8:32 || 0:°700 8-04 0°839 10-01 0-795 9°56 Oct. 6 || 0-787 | 9-47 || 0-787 | 9:47 || 0-900 | 10-82 0-851 | 10:24 23 0°683 8:21 0°736 8°86 0-900 10°83 0-811 9°76 Nov. 7 0-776 9°33 0°735 8°84 1-028 12°36 0°852 10:25 22 0°75 9°34 0°846 10°18 Dec. 8 0-638 7-68 0°759 9-13 0°840 10°10 0°672 8-09 experiments recorded in the first two columns. * These figures, although determined in experiments on actual ultimate growths, should be perhaps more properly assigned to the column for the leaves on penultimate growths; for at the time the developing buds had not produced six mature leaves; hence these figures were obtained only from shoots which had not yet developed the current ultimate growths which gave the leaves for the + This figure, viz.: A = 0-730°, was obtained from an experiment on a sample of leaves from Dixon ano Arkins— Variations in Osmotic Pressure, §c. 288 The figures in this table may be summarized as follows :— Leaves on uliimate growth : Ultimate 3: mean = 0:7388°. max. = 0:916°. Jan. 2; 1911. min. (immature leaves) = 0°608°. Oct. 5, 1910. min. (mature leaves) = 0°638°. Dee. 8, 1911. Penultimate 3: mean = 0°770°.1 max. = 0:°969°. Dec. 28, 1910. min. = 0°605°. Feb. 1, 1911. Leaves on penultimate growth : mean = 0°882°. ma, = IA, INO Wp WOilil. ming — 074225) Heby Ly oir Leaves on antepenultimate growth : mean = 0'978°. max. = 1:061°. Nov. 21, 1910. min. = 0:901°. Feb. 10, 1911. Roots : mean = 0°670°. max. = 0:'903°. Aug. 28, 1911. min. = 0°365°. Nov. 18, 1910. Figs. 1 and 2 are graphs constructed from Table III. A glance at these numbers and curves shows the extremely erratic manner in which the freezing-point (and with it the osmotic pressure) varies. In the first place it may be noted that the intensity of illumination does not define the rises and falls of the curves. Except in the case of the penultimate leaves (fig. 1) where the curve is raised by one erratic observa- tion, the lowest average osmotic pressure is found in the summer months. Again, at the end of the month of May, 1911, in which there had been 235 hours’ sunshine, and where we might have expected a concentration of dissolved substances if their accumulation depended on the intensity of illumination, the depression of freezing-point of the sap from the leaves of the ultimate growths was only 0°718° and that of the penultimate growths only 0°811, while at the end of the previous December, in which there had ultimate growths which was not divided, as in the other cases, into ultimate and penultimate leaves. Hence it is reasonable to suppose that the ultimate three leaves of these shoots had a depression of freezing-point less than 0°730°, and the penultimate three had one of more than 0:730°. 1 This mean is obtained by omitting the high observation on June 13, which, as already explained, should be treated as belonging to the leaves of the penultimate growth. 234 Scientific Proceedings, Royal Dublin Society. been only 20 hours’ sunshine, the figures were 0:969° and 0:940°. It will further emphasize this point when we see that the highest value for the sap of the leaves of the penultimate growths was recorded in the two years of Nov. Dec. pt. Oct. Feb, March April Ma Oct. Nov. Dec. Jan. oO °o ° SS o So o i=) i=} oO co 2 oe @)) ty eee observation in the month of November, although the Octobers of these years had only 71 and 62 hours’ sunshine respectively. An attempt to correlate the rain-fall with the eryoscopie values was found Fie. 1—Innx Aquirolium. June July Aug ic 4 / # / \/ FAVE a + LEAVE Oct. Nov. Dec. Jan. Feb, March April Dixon aNd Arxkins— Variations in Osmotic Pressure, Sc. 239 equally hopeless. The spring and summer months of the year 1911 were characterized by a very small rain-fall ; and hence, if diminution of soil-water TE GROWTH. LTIMATE GROWTHS. D OF PENUL7/. OF ANVEPEN \ ROOTS. 1:00 0:90 0:80 tended to concentrate the saps, we might expect that there would be a rise of the osmotic pressure and an increase in the depression of the freezing-point 790 0:60 0:50 0-40 0:30 0-20 0:10 {0:00 Inex AQuIroLium. 2 Fic. 236 Scientific Proceedings, Royal Dublin Society. during the summer. During the months of November and December, 1910, 7:818 inches’ rain-fall was recorded in Dublin. The soil must then have been almost water-logged. Yet at this time the freezing-point depression of the sap was in each case something over 0°900°. The rainfall for the six months ending June 30, 1911, was 7-915 inches, but the depression of the freezing- point of the saps was in each case less than 0°800°. In spite of the fluctuations, which are surprising, inasmuch as the above conditions do not seem to exercise a direct influence upon them, the annual curves seem to show two indistinct cusps best marked in the record of the penultimate growth, one about November or December and the other about March or April, with corresponding depressions, one about February and the other about June and July. These depressions seem to correspond roughly with the ends of the periods of elongation of the growths. In the autumn the buds may begin to open at the beginning of October, and the axis may continue to elongate till January. In the spring the leaves begin to unfold in May, and elongation proceeds till July or longer. It is evident that during the elongation of the axis of the terminal bud the various growths are at their youngest. Hence if concentration of the sap proceeds with age, we may expect to find the smallest depressions of the freezing-point of the saps coinciding with these periods of elongation. If all the shoots elongated simultaneously, we should get a sudden depression in the curves corresponding with this elongation and followed by a slow rise corresponding with the ageing of the growths formed. As a matter of fact, however, the elongation of the shoots is by no means simultaneous, so that the period of elongation is ill-defined, and consequently the depression is gradual. In spite of fluctuations the curves traced by the freezing-points of the two sets of leaves from the terminal growths run on the whole parallel to one another (fig. 1). The two most marked divergences, viz.,in October, 1910, and June, 1911, are apparently attributable to the same want of simultaneity of elongation. To take, for example, the divergence in June, 1911, here most of the terminal buds had not elongated sufficiently to have formed six mature leaves. Consequently while the three ultimate leaves were for the most part furnished by the buds opening in the spring, 1911, the three penultimate leaves were chiefly furnished by growths of the autumn of 1910 which had so far not yet begun to elongate their spring buds. Thus the ultimate leaves were only just formed, while the penultimate leaves tested were mostly six months old. With regard to the graph of the roots it might appear that the depressions Drxon anp Arxins— Variations in Osmotic Pressure, §¢. 237 correspond with the occasional increases of the water in the soil due to rain- fall. The lowest dip of the curve in November and October, 1910, may, in this way, be attributed to the large rain-fall in those months (viz, 7-818 inches). The second dip (viz. in April) may be assigned to the slightly increased rain-fall in March and April (2°08 inches and 2°77 inches respectively). he third dip at the beginning of July is hard to account for, unless we assume an accidental local supply to the roots from a moderate rain-fall on June 23 amounting to 0°370 inches. A few determinations on the sap of roots in February and March, 1910, show quite different figures for the depressions of freezing-point. Tasie LY. Llex Aquifolium: Roots. Date. A. 1 M | 1910 | Feb. 26 0°619 7:45 206 Mar. 6 0°294 3°54 180 Mar, 12 0559 6°72 — Mar. 19 0°452 5°45 208 They are much lower than those found in 1911. The observation on March 5, 1910, is the lowest record for the sap of Ilex, viz. 0:294°, and indeed for any plant we have so far examined, though in all close on 500 observations have now been made. We have found it futile to attempt to correlate these figures with the rain-fall. In January and February, 1910, the rain-fall was 5:826 inches, in March of the same year only 0:674. On the whole it seems that the roots are able to maintain the cryoscopic values of their sap irrespective of large variations in the amount of soil-water. Possibly the great variations in the osmotic pressures recorded for the roots may be attributed in part to the fact that the roots dealt with were of different ages. Owing to the difficulty of removing the undissolved substances from the sap, only a few determinations of the mean molecular weight of the dis- solved substances were possible. Filtration in most cases was impossible owing to the viscid consistency of the sap; or at least it took so long that a change in the nature of the sap during filtration might be feared. At SCIENT. PROC. R.D.S., VOL, XII., NO, XVIII. 20 238 Scientific Proceedings, Royal Dublin Society. a later date undissolved bodies were successfully removed by centrifuging at a speed of 9,000 revolutions per minute, so that these determinations can now be readily made. So far the highest mean molecular weight obtained in Ilex is 300, viz. in the mature leaves of the antepenultimate growth, October 24, 1910. The highest previously obtained for leaves were 273 for Syringa vulgaris and 280 for Eucalyptus globulus. The lowest for the leaves of Ilex was furnished by mature leaves, February 26, 1910, viz. 215. Generally the mean molecular weight of the dissolved substances in the roots is below these extremes, viz. 180-208; but in the sap of the roots, October 5, 1910, the mean molecular weight of the dissolved matter was determined at 254. The mean molecular weight of the dissolved substances in the roots of Syringa vulgaris has already been found to vary between 178 and 254. ‘I'he latter figure was determined on a sample gathered October 23, 1909. SCIENTIFIC PROCEEDINGS. VOLUME, XIII. 1. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. 2. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Georce H. Preraysripeg, B.SC., PH.D. (March, 1911.) 1s. 8. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wittram Brown, B.so. (April 15, 1911). 1s. 4, A Thermo-Electric Method of Cryoscopy. By Henry H. Dixon, so.p., F.R.S. (April 20, 1911). 1s. 53 A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrttiam J. Lions, 8.a., a.8.c.s0. (Lonp.). (May 16,1911). 6d. 6. Radiant Matter. By Joun Jony, sc.p., r.z.s. (June 9,1911.) 1s. 7, The Inheritance of Milk-Yield in Cattle. By James Wuitson, M.A., B.SO. (June 12, 1911.) 1s. 8. Is Are eopteris a Pteridosperm? By T. Jounson, pD.sc., F.u.s. (Plates Iy.-VI.) (June 28, 1911.) 1s. 6d. 9. The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archxopteris in Ireland. By T. Jouvson, p.sc.,r.u.s. (Plates VIL, VIII.) (June 28, 1911.) 1s. 10. Award of the Boyle Medal to Prorsssor Jon Joy, m.A., So.D., F.R.S. (July, 1911.) 6d. 11. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Jonn Jony, sc.p., F.x.s., and Louis B. Smyru, B.a. (Plate IX.) (August, 1911.) Is. 12. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newsrn Arper, M.A, F.LS., F.G.S. (January, 1912.) 1s. 138. 14. 15. 16. 17. 18. SCIENTIFIC PROCEEDINGS—continued. e Forbesia cancellata, gen. et sp. noy. (Sphenopteris, sp., Baily). By T. Jounson, D.sc., F.L.s. (Plates XIII. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Winson, M.A., B.SO. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic: Chlorides. Part I.—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jamms H. Ponnox, p.so. (Plates XV. and XV1.) (February 21, 1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Drxoy, sc.p., r.r.s., and W.R. G. Atkins, mA. (February 21,1912.) 6d. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, rer.s. (Plates XVII-XIX.) (March 26, 1912.) 1s. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Dixon, sc.d., r.n.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. DURLIN: PRINTED AT THE UNIVERSITY PRUSS RY PONSONKY AND GIKBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 19. APRIL, 1912. VARIATIONS IN THE OSMOTIC PRESSURE OF THE SAP OF THE LEAVES OF HEDERA HELIX. BY HENRY H. DIXON, ScD., F.R.S., UNIVERSITY PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN, AND W.R. G. ATKINS, M.A., A.LC., ASSISTANT TO THE PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN. [Authors alone are responsible for all opinions expressed in their Communications. | Mies VEN (Oe) | j JUI LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATH, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. Price Sixpence. Roval Dublin Society. oN TN FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. e239 al XIX. VARIATIONS IN THE OSMOTIC PRESSURE OF THE SAP OF THE LEAVES OF HEDERA HELIX. By HENRY H. DIXON, Sc.D., F.RS., University Professor of Botany in Trinity College, Dublin, AND W. R. G. ATKINS, M.A., A.L.C., Assistant to the Professor of Botany, Trinity College, Dublin. {Read Fesruary 27. Published Aprin 9, 1912.] SIMULTANEOUSLY with the observations on Ilex Aquifolium recorded in a previous paper,! observations were made on the depression of freezing-point of the sap of leaves of Hedera Helix. ‘The leaves which supplied the sap were taken from prostrate Hedera plants. Two series of measurements were “made, one on the sap from the leaves of plants growing in a north aspect, and the other on the sap of leaves gathered from plants growing in a south aspect. ‘Those in the north aspect were so sheltered, that they at no time were exposed to direct sunlight, while those in the south aspect were exposed when the sky was clear to direct sunlight, except when the sun was near the east and west horizon. This selection of plants for examination was made in order to determine the effect of direct sunlight on the osmotic pressure. It had been previously noticed? in the case of deciduous plants, that exposure to sunlight raised the osmotic pressure. ‘The leaves for each experiment were gathered between 9 and 10 a.m. As in the case of Ilex aquifolium, the age of the leaves was found to have a marked influence on the osmotic pressure, This will appear from the figures recorded in Tables I and IT, relating to north and south aspect leaves respectively. 1 “Variations in the Osmotic Pressure of the Sap of Ilex 5 0:573 | 6:90 14 | Olderstill, ,, ob % 90 0°723 | 8-70 Oct. 16 Small leaves from 1910 shoots, | Overcast. Overcast. 0-455 | 5:47 | 193 16 oe 2) ” 1909, ” ” 0°622 7°48 | 216 16 Large ,, pp LOMO op 99 99 0:750 | 9:02 | 223 Nov. 22 Ultimate 5, Some sun, frost.| Overcast. 0°706 | 8-49 22 Penultimate 5, 99 99 0:858 | 10°32 22 | Antepenultimate 5, | bs ie 0-900 | 10°82 | Noy. 24 Ultimate 5, Rain Misty. 0°629 | 7°57 24 | Next 3, a 5 0-700 | 8-42 24 | Next 3, » 6 0°796 | 9°57 Noy. 29 Ultimate 3, Sun. Frost 0-578 | 6:95 29 Large mature leayes of 1910, . is Hh 0°717 | 8:62 29 Leaves of 1909, ‘ 0 0-823} 9-90 June 7 Young mature leaves, Clear. Clear. 0:426| 5:12) 7 | Old 50 90 9 0-756 | 9-09 Tasie II. Hedera Helix: Leaves from north exposure. Bee | Weather | Date. Description of Sample. on previous | at time of A. P. M. | | day. | gathering. | | June 7 | Young mature leaves, | Clear. Clear. 0°559 | 6°73 | | 7| Old ad ee | rs | iS 0°744| 8-95 Dixon anp Arkins— Variations in Osmotic Pressure, §c. 241 In addition to the depression of freezing-point A, the osmotic pressure P, and, where filtration could be accomplished, the mean molecular weight I of the dissolved substances in these tables, is given a record of the weather on the day previous to and at the time of gathering. At the outset it was expected that the conditions of lighting, humidity, &c., would have had a large influence on the results, especially in the case of the leaves taken from the south aspect. As will be seen, however, this expectation was not realized, or at least the influence of these factors was by no means very marked. In each case the depression of freezing-point of the sap of the ultimate leaves is less than that on the penultimate leaves, and generally the sap of the younger leaves has a smaller depression than that of the older. The observations on October 16th, 1910, show that smaller leaves, although older, may have a smaller depression than larger leaves formed at a later date. This is possibly due to the fact that these smaller leaves are more or less covered over by the larger and often younger ones of adjacent shoots. The growth of Hedera shoots is more continuous than that of Ilex shoots, and the limits of each growth are not defined by a crowd of scars as they are in the latter plant ; consequently it is not so easy to keep the leaves of various ages apart. Furthermore, the observation of October 16th, Table I, shows that the size of the leaves has an influence upon the cryoscopic value of the sap. Hence it was deemed best to collect on each date full-grown mature leaves, and to make the determination of the freezing-point of the sap pressed from these. In the following table these determinations are given for the plants grown in both the south and north aspects. [Tasun III. 242 Screntific Proceedings, Royal Dublin Society. Tass ITI. Hedera Helix: Yeaves. Date E Weather — ; From S. aspect. | From N. aspect. on previous day. | at time of gathering. A. | A. f 1910 | Feb. 28 || Cloudy with sun. Rain. 0:990 | 11-91 0-918 | 11-04 Mar. 3 Overcast. Overcast. 0-951 11°47 14 | Cloud, with sun, frost.) Overcast, frost. 1:073 12-91 1-076 | 12:94 | April 6 Showers, with sun. Overcast. 0°844 10°15 0°837 10:07 | Sept. 30 Cloudy, with littlesun. Sun. | 0-762 9°17 0-594 714 Oct. 16 |) Overcast. Overcast. 0°750 9-02 Nov. 22 || Cloud, with sun, frost.| Overcast. 0-858 10°32 24 || Overcast, rain. Misty. 0-796 | 9:57 | Dec. 6 || Overcast, little rain. | Misty. || 0:733 | 8-82 9 Rain. | Rain. | 0:809 | 9:73 0-802 9°65 14 || Little rain. Overcast. | 0-734 8:83 20 || Overcast. | Overcast. | 0-804 9°67 28 Frost, overcast. | Overcast. 0-942 11 33 1911 | | Jan. 2 || Sun. Frost. OST7 10°54 10 Sun. ~ Clear. 0-763 9°18 0°821 9°88 25 Overcast and sun. Overcast. 0-867 10°43 0°753 9-06 Feb. 9 Overcast, bright. Overcast, bright frost.|| 0°890 10°70 0°831 9°98 21 Sun, frost. Overcast. 0°788 9°48 Mar. 9 Cloud, little rain. Sun, frost. 0-978 11°76 0-883 10°62 24 Overcast. Overcast. 0°851 10°24 0°815 9°81 April 4 |) Sun, frost. Overcast, frost. 0:°968 11°64 0-779 9°37 21 Sun. Overcast. 0°833 10-02 0-784 9°43 May 5 || Sun. | Overcast. 0-913 | 10-98 || 0-770 | 9:26 23 Sun. | Overcast. 0°895 10°76 0-704 8:47 June 7 Sun. Sun. 0-591 (foul 0651 7°83 30 Showers, sun. Overcast. 0°489 5°88 0°514 6:19 Aug. 9 Sun. Overcast. 0°623 7-49 0°522 6°28 96 || Sun. Overcast. 0-607 | 7-81 || 0-526 | 6-32 Sept. 26 || Rain. Sun. 0°624 761 0-640 7°70 Oct. 9 Sun. Sun. 0°723 8-69 0-628 7°55 24 Sun, little rain. Sun. 0-767 9-23 0-659 7:93 Nov. 8 Sun, rain. Overcast. 0-825 9-93 0°651 7°85 21 Sun. Overcast. 0-703 8°46 0-703 8°45 Dec. 7 Rain. Sun. 0°749 9-01 0°749 9-01 28 Rain. Overcast. 0-770 9°26 0°723 8°69 Drxon anp Arxins— Variations in Osmotic Pressure, &c. 248 From this table it will be seen that, in spite of a few exceptions, the eryoscopic value of the sap of the leaves from the south aspect is very consistently greater than that of the leaves from the north aspect. The average depression of freezing-point over a period of nearly two years was 0°799° for the sap of the south-aspect leaves, and 0°748° for that of the leaves from the north aspect, indicating osmotic pressures of 9°61 atm. and 9-00 atm. respectively. This result is quite parallel to Trinchieri’s observations on the cryoscopic values of the sap of Salpichroa rhomboidea. He found that, on the whole, the depression of freezing-point of the sap of the aerial portions was greater in plants grown in a sunny position than in those grown in a more shaded one.’ The higher average eryoscopic value of the insolated leaves finds an obvious explanation in the increased photosynthesis and evaporation. Fig. 1 is a graphic representation of the results set out in the table, omitting the first few observations. This shows there is a rough general correspondence in the variations of the osmotic pressures of the leaves of Hedera with those already described in Ilex. The maximum is attained in the early spring ; the pressure then falls rapidly to a minimum in the summer, rising later in the autumn to a second cusp. There is a second depression indicated, as in Ilex, in the winter months. In spite of the greater irregularity of the curve for the south-aspect leaves, it is surprising how closely parallel it keeps to that traced by the cryoscopic values of the sap of the leaves from the north aspect. As in the case of Ilex, the depressions in the curve seem to correspond to the periods of elongation of the shoots and the formation of new leaves; but in the case of Hedera so great is the summer depression that it seems reason- able to assume that not only is the average age of the mature leaves less at that period, but that also in all probability the sap of the mature leaves is made less concentrated by the transport of dissolved materials into the growing organs, and by other causes. 5 As in the case of Ilex, it seems impossible to correlate the form of the curves closely with external conditions. In the first place, the plant seems to maintain its cryoscopic values quite independently of the rain-fall. The large rain-fall in November and December, 1910, did not succeed in depressing the curves, nor did the drought lasting from January-July, 1911, succeed in raising them. The General Form of the Curves.—The conditions recorded in the second and third columns of Table III show that the amount of sunshine is not an all-important factor; this is also borne out by the fact that some- times in sunny weather, e.g., June 7, 1911, the cryoscopic value of the north- 1G. Trinchieri. Bull. dell’orto botanico. Napoli, 1910. Dec. Nov. Nov. Dec. Jan. Feb. March April May June July Aug. Sept Oct. FRO Sept Oct. 244 Scientific Proceedings, Royal Dublin Society. aspect leaves, which could receive no direct sunshine, is greater than that for the leaves from the south aspect. Again, the fact that the maximum for the —_ _—_ SS LA {yeaosee| Ee ee SOUT) $ FROMNORTH 4 is) oO os2 fos) 30 -8 7 ie) shaded leaves of the north aspect is not nearer the midsummer maximum of illumination than the maximum of the south-aspect leaves, indicates that the excessive sunlight of summer cannot be held responsible for the depression. Fie 1—Heprra Hetrx. Drxon anp Arxins—Variations in Osmotic Pressure, &c. 245 An experiment made in December, 1911, indicates the amount of influence we may attribute to photosynthesis during dark weather about that date. In this experiment comparison was made of the sap of mature leaves freely exposed to the light in the two aspects with that of leaves close by covered from the light for a period of eight days. The results are shown in Table IV. Tasie LY. Hedera Helix: Leaves. Date. Conditions. A. P. M. | 1911 | Dec. 28 | From north aspect exposed, overcast, wet, .| 0°723 8°69 231 6 of 90 », covered 8 days, . | 0:791 9°51 244 5 From south aspect exposed, . 5 0 . | 0°770 9°26 264 D 3 55 », covered 8 days, ; a || O7/il@ 8°54 234 Here the cryoscopic values of the exposed leaves from the north aspect closely correspond with those of the covered leaves from the south aspect. This may be taken as indicating that the conditions of the north-aspect leaves did not at the time allow of very active photosynthesis. The slightly higher value for the sap of the exposed leaves in the south aspect, together with the higher mean molecular weight of its dissolved substances, indicates that in this case photosynthesis was active in raising the concentration. During these observa- tions very wet weather prevailed, so that transpiration was reduced to a minimum, and concentration from that cause may be neglected. The rise in the leaves from the north aspect which were covered for eight days may possibly be explained by the activity of enzymes bringing insoluble bodies into solution. This process in the covered leaves in the south aspect may have been masked by more vigorous respiration in the warmer situation. A similar rise in the eryoscopic value of the sap is often observed in leaves which have been taken from the plant and kept in the dark ; but sometimes this rise is more than counterbalanced by some other process, probably respira- tion, which reduces the cryoscopic value. This latter process is largely or entirely removed when the sap is pressed from the leaves, so that the cryo- scopic value of the sap in the uninjured leaves may fall or rise but slightly, while that of the sap pressed from the same sample of leaves will rise con- siderably, and continue to do so for some days. The figuresin Table V show that the change taking place in sap in vitro is large compared with that proceeding in the picked leaves, both being kept under the same conditions, and, of course, protected from evaporation. 246 Scientific Proceedings, Royal Dublin Society. TaBLE V. Hedera Helix: Leaves. Date. Description of Sample. A. Re M. 1910 Feb. 28 | Leaves from north exposure, : 6 . | 0°918 11:04 239 Mar. 2 Part of last sample kept as leaves, . . . | 0°899 10°79 230 Mar. 3 Leaves from south exposure, y 4 e095. 11°47 250 5 | Part of last sample kept as leaves, . . o || Woe 12°23 4 | Part of March 3 sample kept as sap, ; . | 1:056 12°70 254 Mar. 14 | Leaves from north exposure, ¢ 0 . | 1:076 12°94 15 | Part of last sample kept as leaves, . : 5 |) Loma 12°22 15 | Part of March 14 sample kept as sap, . 5 || Lsilise 13°92 Oct. 5 | Leaves north exposure in town, , 0 . | 0-774 9°31 6 | Part of last sample kept as leaves, . 0 .| 0-781 | 9:39 6 | Part of October 5 sample kept as sap, _ . . | 0°8538 10°53 Taste VI. Hedera Helix: Weaves. | March He BS | US te ue | A of sap pressed from leaves of north aspect and kept, —._| 1076 1-157 | 1-232 1°310 | 1:450 WH on PA a 0 i” 5 : | 1-016] 1-116 1-215 | 1:267 In Table VI are records of the cryoscopic rise taking place in two samples of sap pressed from their leaves, and stored in the dark in a closed test-tube. Reference to Table III and the graph in fig. 1 will show that the highest figures for the freezing-point depression in winter coincide with frosty weather. On these occasions we may conclude that the raising factors of photosynthesis, or solution, or both, were active, while the cold completely or partially inhibited respiration and translocation from reducing the concentra- tion. This seems the only instance of external conditions producing a well- defined effect on the seasonal curve of the cryoscopic values of the sap of Hedera. 1. bo 10. 11. 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearine Ivish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamiwm, Williamson). By T. JonNson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from thejplanted Tubers. By Georcz H. Prruysriven, B.S¢., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wittram Brown, B.so. (April 15, 1911). 1s. . A Thermo-Hlectric?Method of Cryoscopy. By Henry H. Dixon, sc.p., F.R.s. (April 20, 1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wiut1am J. Lyons, B.A., a.R.c.sc. (LonD.). (May 16,1911). 64. - Radiant Matter. By Jon Jony, sc.v., r.r.s. (June 9,1911.) Is. . The Inheritance of Milk-Yield in Cattle. By Jamms Wusson, m.a., B.Sc. (June 12, 1911.) 1s. . Is Arc zopteris a Pteridosperm? By T. Jonson, v.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archaopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jounson, p.sc., F.1.S. (Plates VII., VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Prorgssor Joan Jony, m.a., sc.d., ¥.R.S. (July, WOU) Gah. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Joan Jony, so.p., F.x.S., and Lous B. Smyra, B.a. (Plate IX.) (August, 1911.) 1s. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newern Arser, ua, F.LS., F.G.s. (January, LOAD) elise 13. 14. 15. 16. 17. 18. 9), SCIENTIFIC PROCEEDINGS—continued. Forbesia cancellata, gen. et sp. noy. (Sphenopteris, sp., Baily). By T. Jounson, D.sc., F.u.8. (Plates XIII. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Witson, M.A., B.SC. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jamms H. Potnox, p.so. (Plates XV. and XVI.) (February 21,1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, sc.., F.R.s., and W. R. G. Arxins, u.a. (February 21,1912.) 6d. Improvements in Equatorial Telescepe Mountings. By Sr Howarp Gruss, Fk.s. (Plates XVIL-XIX.) (March 26, 1912.) 1s. Variations in the Osmotic Pressure of the Sap of Ilex aqwifoliwm. By Henry H. Drxon, sc.p., r.R.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Drxon, sc.p., F.R.S., and W. R. G. Arxins, u.a., aac. (April 9, 1912.) 6d. ue DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIRBSo THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 20. APRIL, 1912. HETERANGIUM HIBERNICUM, sp. nov. : A SHED-BEARING HETERANGIUM FROM COUNTY CORK. BY Pe OLINSON DESc. HLS: PROFESSOR OF BOTANY IN THE ROYAL COLLEGE OF SCIENCE FOR IRELAND. (PLATES XX., XXI.) [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, PET 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.¢. A.” 1912. EAS Ean} an Price One Shilling. Roval Dublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749. OOOO EVENING SCIENTIFIC } MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. co J XX. HETERANGIUM HIBERNICUYM, sp. nov.: A SEED-BEARING HETERANGIUM FROM CO. CORK. By IT. JOHNSON, D&c., F.LS., Professor of Botany in the Royal College of Science for Ireland, Dublin. (Puarrs XX anp XXI.) [Read Frsruary 27. Published Aprin 12, 1912.] In continuation of my endeavours to examine, in the light of recent dis- coveries, the specimens, as far as available, of fossil plants recorded from Ireland, I was puzzled for some time as to the nature of those described by Baily under the general term of “ Linear Plants” and more specifically under that of Filicites lineatus. Some of the specimens suggested leaf-stalks or rachises of genera of one of the most ancient groups of Ferns—the Botryopteridea— though certain markings seemed to indicate affinities with a Heterangium type of plant. Figures of Filicites lineatus are given by Baily (1) (fig. 2, p. 20) in the Memoirs of the Geological Survey of Ireland (Hxplanation of sheets 187, 195, and 196. . . of County of Cork, 1864). The specimens! figured were found in the Upper Old Red Sandstone and Carboniferous Slate of Bandon, Co. Cork. Baily says of them—‘The plant remains in the slate rocks of this district—provisionally named ‘ Linear Plants’—consist of stems nearly straight, marked by fine longitudinal striations and having usually a central depression, with a corresponding ridge on each side, arising probably from compression, as they are more or less flattened. From these stems proceed on either side diverging branches of smaller diameter, which again become forked and terminate without any trace of attached leaflets; the principal stems vary in diameter from about half an inch to two lines (or two-twelfths ofan inch). From the character of these plants I have no doubt of their having been terrestrial and probably allied to Ferns; there is nothing to guide us, however, at present as to their exact position in the vegetable series. I would propose to name them provisionally Filicites lineatus.” Unfortunately the particular specimens illustrated in Baily’s account are temporarily mislaid,and we are compelled to form our conclusions as to their nature apart from these specimens. Nathorst (2), e.g., considers that, in Baily’s 4 As in other cases, I am indebted to Professor Grenville A. J. Cole, r.a.s., for permission to examine these specimens from the Collections of the Geological Survey of Ireland. SCIENT. PROC. R.D.S., VOU. XIIL., NO. XX. 2Q 248 Scientific Proceedings, Royal Dublin Society. fig. 2, two distinct genera are represented. Fig. 2u (“ Dichotomizing stem of the ordinary size”) of Baily is, he thinks, very like his own Cephalopteris mirabilis from the Upper Devonian Rocks of Bear Island. In the specimen figured to the right the uppermost primary pinne appear to him opposite and fertile. Nathorst further regards fig. 2b (“ Dichotomizing stem of a larger size”) of Baily, on account of the transverse strie figured, as a Heterangium or allied genus. Though Baily’s “type” specimens of Filicites lineatus are not at present forthcoming, there are other specimens of ‘‘ Linear Plants” in the collections of the Geological Survey, and these I examined, and had in some cases photegraphed, without venturing to locate them definitely, spite of Nathorst s suggestions. One day, however, Mr. Hallissy, of the Geological Survey, showed me a specimen of a “ Linear Plant” he had unearthed from the stores of the Survey, and a very cursory examination satisfied me that the specimen was a fine impression of a Heterangium (Pl. XX., fig. 1). Heterangium Grievii (Willm. sp.), the best-known species, was described as long ago as 1720 as Fumaria officinalis, but in 1822 was separated by Brongniart (3) as a Fern under the name Sphenopteris elegans. Brongniart’s description is confined to the fragments of foliage he had before him. His fig. 2 shows the dichotomy of the rachis, though he does not call attention to it. He includes in his diagnosis the transverse striation of the rachis, without, however, introducing it into his igure. The fullest account of the external features of H. Grievit is due to D. Stur (4), who was so impressed with the importance of dichotomy of the frond in the Paleozoic plants that he created a genus Diplothmema, in which he placed a heterogeneous collection of fossil plants with dichotomy of the primary rachis as a distinguishing feature in common. In this genus he placed Brongniart’s S. elegans under the name of Diplothmema elegans. Although Stur speaks of making transverse sections of the stem, he does not describe them, and, in fact, says nothing of the internal anatomy of the plant. On the other hand, he gives an elaborate illustrated account of the external features. His figures are so true that I at once recognized my “linear plant” as the same as his D. elegans. Kidston (5) notes that the transverse striation in AH. Girievii occurs in S. elegans Bret. and S. grandifrons Sauvear. Stur concluded his plant was a Fern, though he rightly rejected Goppert’s evidence of the presence of sporangia. The most complete account of Heterangium Grievii is given by Scott (6) in his “Studies in Fossil Botany.” It is based on the investigation of the anatomy of the plant by Williamson (7) and Scott in 1896, this being a revision of Williamson’s investigation in 1873. We learn that Heterangium Jounson—A Seed-Bearing Heterangium from Co. Cork. 249 almost certainly was like Lyginodendron oldhamium (Crossotheca Heninghausi Kidston sp.), a Pteridosperm of the group Lyginodendres. Its angular stem, rarely branched, formed adventitious roots, and bore large compound pinnate, fern-like leaves, spirally arranged with a divergence of 2 or 3. Its stem shows a central Gleichenia-like monostelic or haplostelic vascular axis, without pith. Its peripheral or peri-medullary mesarch primary xylem is arranged in indistinct groups with internal metaxylem mixed with con- junctive parenchyma, occupying the position of the pith. Secondary thickening of regular character (xylem within, phloem without) occurred, though no stem is known more than 2 em. wide, the average diameter being 15 cm. (The Bear Island specimen doubtfully referred to Heterangium by Nathorst has a diameter of 3 cm.) The tracheids, other than the protoxylem ones, show multiseriate bordered pits on their radial walls. Very striking to the naked eye is the transverse striation, which was shown by Williamson to be caused by horizontal plates of rounded sclerotic cells arranged in vertical rows in the inner cortex. The surface of the stem is also longitudinally striate, owing to peripheral sclerotic strands comparable with those forming the network in Lyginodendron, but running almost vertically. The phyllotaxis, elaborately worked out by Stur, was independently ascertained by Williamson by the study of the internal anatomy. The transverse striation is continued into the rachis, which presents on its upper side a deep median groove with a ridge on either side. The under side of the rachis is convex. The striz are best seen as a single row in the adaxial groove, but are not confined to it: Judging from the pronounced transverse striation of Sphenopteridium rigidum (Ludw.) Pot., and S. furcillatum (Ludw.) Pot., as described and figured by Potonié (8) in the rachis of these two fossil plants from the Upper Silurian (?) beds of the Harz Mountains, they will be found when more complete specimens are available to be members of the Pteridosperms. It is worthy of note in passing that Potonié compares the two species with S. edegans, now recognized as the foliage of Heterangium Girievii. Again, the Rhodea dissecta (Brgt.) Presl, figured by Potonié (9) as synonymous with Diplothmema Schiitzei Stur, differs only in its smaller size from D. elegans i.e. Heterangium Grievii, and is clearly a Pteridosperm—a view already held by Kidston (10). The single leaf-trace bundle arises opposite the primary xylem,and is in direct con- tinuity with it. It at once passes out from the pericycle into the cortex to run through 7-8 internodes, 2 cm. high, before entering the base of the rachis as a solitary trace. The bundle is at first collateral and exarch, but becomes concentric in the rachis. Sufficient has been said to show that, from a study of the vegetative organs alone, the evidence was strong enough to justify the inclusion of Heterangium in the new transitional group of 2Q2 250 Scientific Proceedings, Royal Dublin Society. Pteridosperms or Cycadofilices. It is fern-like in habit, and in some of its anatomical features, but is Gymnospermous in others (mesarch xylem, bordered pits, secondary thickening in stem and roots). Heterangium is recorded from Bear Island (?), Scotland, England, France, Germany, and now from Ireland. It extends from the Upper Devonian, through the Carboniferous to the Permian strata, but always, as hitherto described, in a sterile state. Hence I examined with peculiar interest our Irish specimen. It is the carbonaceous impression of a piece of stem and attached leaf- stalks. It is 14 cm. long, and 1 em. wide in the internodes, and shows some three leaf-stalks spirally arranged. No specimen of Heterangium has ever been found showing the stem, leaf-stalk, and leaf-blade all in connexion. Further, the leaf-stalk is naked from its base upwards for at least 20 cm. of its length. Stur gives a figure of a leaf-scar, and considered the leaves of Heterangium deciduous like those of Acrostichum among modern ferns. In the Irish specimen the lamina is unrepre- sented. The sclerotic plates are well pre- served as cross-stri#, both in stem and leaf-stalk. The wings cf the stem formed by the decurrent leaf-bases are well indi- cated at the nodes. In H. Grievii the leaf-trace is found to be occasionally, in H. lomacii regularly double. The leaf- stalk of our specimen presents a feature I cannot find described in any other Hete- rangium. From the under side of each Fis: 1.—Reduced figure of H. hibernicum, : i ‘ R 5 showing the spur-like appendages (a) of petiole near its insertion there arises a the rachis. spur-like outgrowth, showing signs of bifurcation. This abaxial basal appendage may be the proximal part of a sporangiophore as suggested by the similarly placed one of Cephalopteris mirabilis. Its presence, in association with other minor points of difference, prevents me from identifying our specimen with H. Grievii; and I propose to call it accordingly H. hibernicum’—a specific name which wili serve also to indicate its origin. (PI. XXI.) 1 Baily’s fig. 2 represents, I think, (a) the branching rachis, (2) the stem with petioles of Heteran- gium. I have at thesame time satisfied myself from inspection of specimens that all Baily’s ‘linear plants’’ are not referable to Heterangium. Jounson—A Seed-Bearing Heterangium from Co. Cork. 261 The slab on both sides shows scraps in which I have sought in vain for signs of pinne. In fig. 2 one sees a forked scrap in connexion with a branch of the rachis, and ending in its curved tips in dilatations not unsuggestive of seeds. The clearest case is that represented in fig. 3. A branch of the rachis (Fig. 2, a) bears a small curving rachidial filament on which, in addition to one or two finer branches and lateral expansions, an oval body is carried at its tip. This sessile body, 2 mm. long and 1 mm. wide, shows a central space or cavity bordered by a wall of fairly uniform thickness, slightly papillate at the apex. It is continuous with the rachis branch, and appears to be an immature ovule or seed, of less size than an ordinary Conostema (10) seed, but of the same general ‘“boat-like” form. It is unfortunately only an impression ; and I must leave the illustrations (Pl. XX., figs. 2, 8) to support me in concluding that it supplies additional proof that Heterangium, like Lyginodendron, is a true Pteridosperm. In this Fig. 3—Shows the “‘ ovule”’ borne on a branch of the Fig. 2—Cf. Pl. XX., fig. 2. rachis. connexion the following note from the columns of “ Nature” on a paper read by Dr. Margaret Benson (12), March, 1909, is of interest. So far as I know it is the only information yet published on the investigation :— ““Spherostoma ovale, n. gen., and Crossotheca Grievit, n. spec., an account of the structure and relations of the reproductive organs of Heterangiwm Grievit. “ Spherostoma ovale (Conostoma ovale et intermedium, Williamson) is the earliest Palaeozoic ovule so far known structurally. It is a small ovule 3°5 mm. in length, and shows the same general type of organization as the ‘Lagenostoma’ series of ovules. The pollen-chamber, however, does not engage with the micropyle, but opens and closes with a very perfect 252 Scientific Proceedings, Royal Dublin Society. mechanism, somewhat reminiscent of the peristome and epiphragm of Poly- trichum. The paper also deals with the relation of this ovule to Heterangium Grievii, and with a new Orossotheca which is attributed to the same plant.” It is interesting to find that two seed-bearing members of the Pterido- sperms closely allied to one another, and members of the Lyginodendres, viz., Crossotheca Heninghausi Kidst. sp., and Heterangium hibernicum sp. nov., grew in Ireland, H. hibernicum in the Upper Devonian and Lower Car- boniferous rocks of Co. Cork, and C. Heninghausi in the Coal Measures or Upper Carboniferous beds of Co. Tipperary. 12. BIBLIOGRAPHY. . Baity, W. H.: Explanation of Sheets 187, &c., of the County of Cork, 1864, p. 19, fig. 2a and 6. (Mem. Geol. Sury. Ireland.) . Narnorst, A. 8.: Zur Oberdevon. Flora der Baren-Insel, Kongl. Svenska Vetensk. Akad. Handl. Bd. xxxvi., 1912, p. 11, Taf. 1, Figs. 1, 2. . Bronenrarr, Apo.pue T.: Histoire des Végétaux fossiles, &c., Tom. i., 1828, p. 178, Pl. liii, figs. 1, 2. . Stur, D.: Die Culm-Flora d. Ostrauer und Waldenburger Schichten. (K. k. Geol. Reichsanst. Bd. viii. Wien, 1875-77, Taf. xiii, fig. 5; Taf. xiv., figs. 1-6.) . Kipston, R.: On the Fructification and internal structure of Car- boniferous Ferns, &c. (Trans. Geol. Soc., Glasgow, vol. ix, 1893.) . Scorr, D. H.: Studies in Fossil Botany, 1909, Part ii, p. 401. . Wittiamson, W. C., and D. H. Scorr: Further Observations on the Organization of the Fossil Plants of the Coal-Measures. Part iii, Lygino- dendron and Heterangium. (Phil. Trans. Roy. Soe, vol. elxxxvi, 1896.) . Poronit, H.: Die Silur und d. Culm-Flora des Harzes, &e. (Abhandl. d. K. preuss. Geol. Landest., Heft xxxvi., Berlin, 1901.) . Poronti, H.: Lehrbuch der Pflanzen-Palaeontologie, Berlin, 1899. . Scorr: supra, (6) p. 418. . Oriver, F. W.,and EH. I. Sarispury: On the Structure and Affinities of the Palaeozoic Seeds of the Conostoma Group. (Annals of Botany, vol. xxv., 1911.) Benson, Marcarrer: Spherostoma ovale, gen. nov., and Crossotheca Grievii, sp. nov., an Account of the Structure and Relations of the Reproductive Organs of Heterangium Grievii. (“ Nature,” April 22nd, 1909, p. 239.) EXPLANATION OF PLATE XX. PLATE XX. HETERANGIUM Hisernicum, sp. nov. Fic. 1. Reproduction of photograph (somewhat reduced) of the impression of Heterangium hibernicum. (See fig. 1, p. 250.) 2. A branching piece of a rachis, showing, just below the arrow, the seed impression. (See also figs. 2 and 3, p. 251.) 3. Enlarged reproduction of part of fig. 2, showing the seed, the position of which is indicated by the arrow. SCIEND. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XX. OF PLATE XXI. ; PLATE XXI. Hetrrancium Hipernicum, sp. nov. Kinlargement of Fig. 1, Plate XX. PLATE XXI. VOL, XIIT. NESS SOC., SCIENT. PROC. R. BUBLIN i Voy Render it ice 1) iia iis) i, 10. 11. 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jounson, D.s0., F.LS. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Georcn H. Peraysriner, B.Sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wiitiam {Brown, 8.80. (April 15, 1911). 1s. . A Thermo-Electric Method of Cryoscopy By Henry H. Dixons, so.p., F.R.s. (April 20,1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wituam J. Lyons, 8.a., a.R.c.sc. (Lonp.). (May 16,1911). 64d. . Radiant Matter. By Joun Jouy, sc.p., r.z.s. (June 9,1911.) Is. . The Inheritance of Milk-Yield in) Cattle. By James Winson, .4., B.S0. (June 12, 1911.) 1s. . Is Are wopteris a Pteridosperm? By T. Jounson, v.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archaopteris Tschermaki, Stur, and of other Species of Archzopteris in Ireland. By T. Joawson, D.sc.,F.u.s. (Plates VIL, VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Prorsssor Joun Joy, m.a., s0.D., F.R.S, (July, 1911.) 6d. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. (By Joun Jony, sc.p., F.z.s., and Louis B. Smyrx, B.a. (Plate IX.) (August, 1911.) 1s. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newettn ARBER, M.A, F.LS.. F.G.S. (January, 1912.) 1s. 13. 14. 15. 16. 17. 18. 19. 20. SCIENTIFIC PROCEEDINGS—continued. Forbesia cancellata, ger. et sp. nov. (Sphenopteris, sp., Baily). By T. Jounson, D.sc., F.u.s. (Plates XIII. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Witson, M.a., B.Sc. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Potuox, p.sc. (Plates XV. and XVI.) (February 21,1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, sc.., r.z.s., and W.R. G. Arms, m.a. (February 21,1912.) 64d. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, res. (Plates XVIT-XIX.) (March 26, 1912.) 1s. Variations in the Osmotic Pressure of. the Sap of Ilex aquifolium. By Henry H. Drxon, sc.p., F.z.s., and W. R. G. Arxins, u.a., a.t.c. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Dixon, s¢.p., F.B.S., and W. R. G. Arxins, m.a., a..c. (April 9, 1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jonnson, p.sc., F.u.s. (Plates XX. and XXI.) (April 12, 1912.) 1s. DUBLIN: PRINTKD AT CHE UNIVERSITY PRLSS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 21. MAY, 1912. ON THE VACUUM TUBE SPECTRA OF SOME METALS AND METALLIC CHLORIDES. Part I.—LEAD, IRON, MANGANESE, NICKEL, COBALT, CHROMIUM, BARIUM, CALCIUM, STRONTIUM, MAGNESIUM, POTASSIUM, SODIUM, AND LITHIUM. BY JAMES H. POLLOK, D.Sc., ROYAL COLLEGE OF SCIENCE FOR IRELAND. /7-xysonlai (PLATES XXIl., XXIII.) [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. Price One Shilling. Roval Dublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC } MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. [ 253 | XXI. ON THE VACUUM TUBE SPECTRA OF SOME METALS AND METALLIC CHLORIDES. Parr IIl.—LEAD, IRON, MAN- GANESH, NICKEL, COBALT, CHROMIUM, BARIUM, CAL- CIUM, STRONTIUM, MAGNESIUM, POTASSIUM, SODIUM, AND LITHIUM. By JAMES H. POLLOK, D.Sc., Royal College of Science for Ireland. [Pirates XXII. ann XXIII. ] {Published May 7, 1912.] THE experiments were conducted precisely in the manner described in the first part of this paper, the same apparatus and method being used through- out. ‘The quariz vacuum tube has already been illustrated and described in detail. The illustration in Plate XXIII. shows the whole apparatus, with the spectrograph, coil, condenser, pump, dryers, gauge, vacuum tube, and Meker burner, in working order. The generalizations arrived at in previous observations were confirmed by the observations on this new series of metals and their chlorides. Bands were not so prominent a feature of the spectra of the compounds examined in this part of the paper, except in the cases of manganese and magnesium ; with them a greater number of lines show when the condenser or Leyden jar is used, and the bands are less conspicuous. Apart from the bands, the spectra of the vapours of metallic chlorides appear to consist exclusively of the lines of the spark spectra of the metals of which they are composed, with or without the lines of the spark spectrum of chlorine, together with the ultimate lines of any impurities that may be present. ‘There is, so far, no reason to believe that compounds give rise to extra lines in the spectrum ; and in all cases where lines have been observed that were not due to the metal and chlorine, and have been carefully measured and investigated, they have invariably proved to be the ultimate lines of the vacuum tube spectrum of some other metal or non-metal present as an impurity. It would be premature to assert that no lines due to the compounds of the metals with chlorine existed until every line in each spectrum was accurately measured and identified; but it may safely be asserted that such lines are not a prominent feature of spectra, and, if they exist at all, SOIENT. PROC. R.D.S., VOL. XIII., NO. XXI, 2k 204 Scientific Proceedings, Royal Dublin Society. they are faint lines not likely to cause confusion in an analysis, and need not be considered; so that if three or four prominent lines are obtained in a vacuum tube spectrum, that cannot be identified as the ultimate lines of a known element, one may safely conclude that they are the ultimate lines of an unknown element. With bands it is quite otherwise. Different compounds appear to give rise to different bands, not in any way related to the spark spectra of the elements of which they are composed, but due to the molecular aggregation of the elements or com- pounds present, so that, from an analytical point of view, no importance can be attached to the appearance of a new band in aspectrum. On investigation it will certainly prove to be the most prominent band in the banded spectrum of some compound of the elements present. The only danger of confusion with bands is when only a small quantity of the compound that gives rise to them is present, when the band fades away and leaves only one or two pro- minent lines of the head of the band, which then have much the appearance of the lines of aline-spectrum, and may possibly cause the analyst to erroneously suspect the presence of some new body. As a general rule, the strongest lines in the spark spectrum are the strongest lines in the vacuum tube spectrum of an element; and, as a general rule, the ultimate lines in the vacuum tube spectrum appear to be identical with the ultimate lines of the spark spectrum, but this is not always the case, and it is very desirable that the ultimate lines of vacuum tube spectra should be carefully investigated and tabulated at an early date, for without a knowledge of the ultimate lines of the elements it is often difficult, if not impossible, to arrive at any certainty in the identification of the lines of a spectrum. Manganese gives a very characteristic group of lines that are surprisingly persistent in the vacuum tube A 2801°3, A 2798-5, and A 2795°3, and these are quite different from the ultimate lines of the spark spectrum of manganese X 2605°8, X 2594:0, X 2576-2. I have seen this group in the vacuum tube spectra of metallic lithium, and of potassium chloride, and barium chloride, no other lines of manganese showing. The tenacity with which metals adhere to a tube when once they are introduced is very surprising, and would indicate that very small quantities are all that are necessary to give a spectrum. Photographs of the various spectra are reproduced in Plate X XII., and an approximate scale of wave-lengths is given to facilitate the identification of the lines, but it is not exactly in position over the lead spectrum. For the purpose of accurate measurement the cadmium spectrum has been photographed through the middle of some of the spectra. T have to thank the Government Grant Committee of the Royal Society Pottox—On the Vacuum Tube Spectra of some Metals. 255 for the loan of instruments, and for a grant which has partly defrayed the expenses of this investigation. Leap. Both the metal and its chloride give a brilliant luminescence in the vacuum tube, and the spectrum is photographed with ease, giving all the principal lines of the metallic spark spectrum of lead, and a number of bands show faintly, especially when no condenser is used. Many of the discontinuous lines of lead do not show, and the introduction of the Leyden jar fails to bring them out. Certain lines of lead at the ultra-violet end of the spectrum show with the metal, but not with the chloride; and lead once introduced in a vacuum tube remains with surprising tenacity; no amount of boiling with acid, or washing with water, removes the ultimate lines of lead from the photographs of the spectra of other materials subsequently examined in the tubes. A very minute quantity of lead must be capable of giving a good spectrum. Principal Lines of Lead. Vacuum Tube. Vacuum ‘lube Deere | spare. MPR sere NoL. J. | With L. J. | No. L. J. | With L. J. | 5608-2 10 0 5 3176°6 10 0 0 4387°3 9 7 8 313778 10 0 0 4245-2 10 8 9 2873°4 10 10 10 4168-2 (o) 5 6 2833°2 10 8 8 4062°3 6 6 6 2823°3 10 9 9 4058-0 x 10 10 10 2802-1 10 10 10 4019°7 8 4 4 2663°3 x 10 4 4 3854-0 10 0 0 2614°3 10 8) 9 3833-0 8 0 0 2577°3 8 0 i 3786-4 10 0 0 2562°3 8 0 0 3740°1 x 10 10 10 2476-5 8 8* 8* 3683°6 x 10 10 10 2446°3 6 6* 6* 3671-7 8 8 8 2443-9 6 5* 6* 3639°7 x 10 10 10 2428°7 2 0 0 3572°9 vy 10 10 0 10 2411°8 2 if Is 3262°5 1 4 4 2402:0 2: Dy.) 2* 3220°7 2 1 1 2393°9 4 4* 4* * Seen strongly with the vapour of the metal, but not always with that of the chloride. 2R2 206 Scientific Proceedings, Royal Dublin Society. Tron. Ferric chloride gives a brilliant luminescence in the vacuum tube, both with and without the condenser; but there is a difficulty in getting a good photograph of the spectrum, as the capillary portion of the tube is often rendered opaque by a black deposit that forms at an early stage in the experiment: this is best guarded against by having only a small quantity of the material present, and having it thoroughly dehydrated before exhausting the tube. When a successful photograph is obtained, it contains apparently all the lines of the spark spectrum of the metal, with much the same relative intensities, so that there is no need to tabulate them in full, but the following table gives the lines that are most prominent when only a minute quantity of the substance is present, or only a short exposure is given. ‘The Leyden jar makes little difference other than to increase the intensity of all the lines, or shorten the time of exposure necessary. No prominent bands are seen. Principal Lines of Iron. Vacuum Tube. Vacuum Tube. Tees ; Spark. Ten Spark. = No L. J. | With L. J. NoL. J. | With L. J. | 4144-0 7 1 D) | 3631-6 10 8 9 4132-2 8 1 6 } 3618°9 9 9 10 4071°9 10 5 6 | 3609-0 9 8 9 4063°8 10 5 6 || 3681°8 10 9 10 4046-0 10 9 10 3570°3 8 9 10 3860:1 9 9 10 || 3565-5 8 9 10 3856°6 8 7 8 3475°6 7 2 2 3850°1 6 7 8 3466-0 7 2 p) 3840°6 8 7 8 3441°1 6 9 10 3834:4 8 7 8 3399°5 5 3 4 3826-0 9 7 8 3370°9 4 1 1 3820°6 9 9 10 3348°1 1 1 1 3745°7 7 9 10 ~—'||_:«3323°8 1 1 1 3735°0 10 9 10 ‘|| 3306-5 7 1 1 372071 | 8 9 10 3306°1 7 1 1 3648-0 9 8 9 || 3227-9 6 1 1 PottoK—On the Vacuum Tube Spectra of some Metals. 257 Principal Lines of Iron—continued. Vacuum Tube. | Vacuum Tube. WO | Sete -=——————]| (28 | sot en NoL. J. | WithL. J. a No L. J. | With L. J. 3180°3 2 P) 2 2617-7 7 2 9 3059-2 3 3 4 2613°9 9 2 9 3047-7 3 3 4 2612-0 9 3 9 3021-2 8 8 10 2607-2 9 3 9 3001-1 2 1 1 2599°5 10 8 10 2999-6 g 1 1 2598-5 10 8 10 2994-6 3 1 1 2586°0 8 2 8 2984-9 6 4 8 2567-0 4 2 4 2973-4 2 4 8 2563°5 5 7 8 2973°3 2 4 8 2562°6 6 7 8 2970-2 2 1 2 2549-7 4 1 2 2969°5 1 1 1 2639-0 5 1 1 2965-4 1 4 8 253399 7 3 4 2948-0 2 3 6 2532°4 1 1 2 2937-0 2 1 1 2529-6 6 3 4 2813°4 2 1 1 2526°3 6 1 2 2783'S 7 1 1 2525°5 7 1 2 2779°3 5 1 1 2525-1 3 1 2 2778°3 2 1 1 2522°9 6 1 2 2767°6 7 2 6 2511-8 7 1 4 2755°8 10 4 10 2497 9 5 1 2 2749°4 10 4 10 2493°3 8 2 8 2746-6 7 4 10 2413-4 8 2 6 2739°6 10 4 10 2410°6 8 3 10 2727°6 8 2 4 2406°7 6 1 2 2714°5 7 7 2 2405:0 7 1 2 2692°7 6 1 1 2399°3 8 4 6 2684°8 6 1 1 2395°7 7 6 8 2667:0 1 2 2382°1 9 6 8 2664°7 7 10 2 2348-2 7 4 6 2631-4 4 2 10 2343-6 9 4 6 2631-1 4 2 10° 2338°1 8 1 2 2628-4 8 2 8 2332:9 8 2 4 2625°8 7 2 8. 258 Scientific Proceedings, Royal Dublin Society. MANGANESE. Manganous chloride gave a very brilliant luminescence in the tube, and the photograph showed all the lines of the spark spectrum of metallic manganese with very strong bands in the visible part of the spectrum from ) 3980 to A 3520, and the introduction of the Leyden jar into the secondary circuit made very little difference to either the lines or the bands. It was remarkable that three lines that are quite weak or only of medium strength in the spark spectrum of the element showed very strongly in the vacuum tube. I noticed the same three lines present as impurities in the spectra obtained from potassium chloride, barium chloride, and metallic lithium, though no other lines of manganese showed; the lines are 22801°3, \ 27985, A2795°3, and their origin should be further investigated. They are certainly not the ultimate lines of manganese in the spark spectrum, these being marked w on the table. Principal Lines of Manganese. | | Vacuum ‘ube. | Vacuum Tube. eave | Sak. j= ware. Spark. ength. | ength. : No L. J. | With L. J.| No L. J. | With L. J. | 0218 | 10 1 1 4456-0 6 6 6016-6 | 10 1 1 4455°5 4 6 6 6013-6 10 | 1 || 4455-9 4 6 6 5420-6 6 1 1 || 4458-2 4 6 6 5413-9 6 W]e | aapiiee 6 GL yl Ma 5341-2 6 6 6 4436°5 4 ee | 1 4893-7 8 W | x0 4416-1 4 1 1 4754-2 6 8 8 4281-3 4 2 2 4472°9 4 6 6 4266-1 3 2 | D 4470°3 4 6 6 4257°8 4 2 2 4464-9 4 B | 6 4939-9 6 6 44622 6 6 6 4235°5 6 6 4461-2 4 6 6 4235°3 6 6 4458-4 4 a | 6 4083-8 6 i0 10 4457°7 4 Ge | 6 4083°1 6 eam 9 4467-2 | 4 Gut 6 4079°6 4 9° | 9 PotioK— On the Vacuum Tube Spectra of some Metals. 259 Principal Lines of Manganese—continued. Vacuum Tube. Vacuum Tube. Des | SP | nen, | SE No L. J. | With L.J.| No L. J. | With lope | | 4079°4 4 9 9 3496°0 8 4 4 4063°4 6 6 3488°8 10 4 4 4061°9 6 6 3483°0 10 4 4 4059°5 6 6 3474°2 10 8 8 4059°1 4 6 6 3460°5 10 8 8 4055°7 6 6 6 3442-1 10 10 10 4048-9 6 6 6 2949-3 x 10 10 10 4045-3 6 6 2939-4 8 10 10 4041-4 6 6 6 2933-1 x 8 10 10 4034-6 6 10 10 2889°5 6 6 6 4033°2 6 10 10 2879°5 6 6 6 4030°9 6 10 10 2801°3 4 5 G2 3839°9 4 6 6 2798-5 4 6 10* 3823°6 6 6 6 2795°3 4 6 10* 3806-9 10 10 10 || 2605-8 | « 10 10 10 3570-2 8 4 4 2594-0 w 10 10 10 3548-2 10 10 10 2576°2 # 10 10 10 3548-1 10 10 10 2452°6 6 9 ‘9 3532-0 10 10 10 2438-2 8 9 6) 3532°1 10 10 10 2428-0 6 9 9 * Seen in other yacuum tube spectra. 260 Scientific Proceedings, Royal Dublin Society. CHROMIUM. Chromyl chloride was used, and gave the spectrum with great ease, showing all the principal lines of the spark spectrum of the metal; no bands were seen. The condenser made little or no difference. Principal Lines of Chromium. Vacuum Table. Vacuum Tube. Teme | SEES een Lengtn, | Sbark. NoL. J. | WithL. J. | No lL. J. | With L. J. 5410-0 8 2 2 3578°8 se 0 10 10 5296:9 2 2 2 3430°5 10 8 8 5275:3 4 2 2 || 3422-9 10 8 8 5264:3 J | a | 2 3421-4 10 8 ee | A247°7 4 2 2 3408-9 10 8 8 5208-6 10 TON eet OM eal eers40325 10 8 8 5206-2 10 10 10 || 3368-2 10 6 6 | 5204°7 10 10 10 3360-5 10 | 6 6 4351°9 Bea Celia Simei s340;8 9 |e Gita 4351-2 7 8 8 3340-0 10 6 6 4344-7 8 8 8 3307-2 10 6 6 339°8 8 8 8 | 3197-2 10 10 10 | 4339°6 8 | 8 || 8 3180-8 10 | 10 10 | 4289-9 #19. || 20) tO Bitepes 10 6 6 4274-9 10 | 16 10 | 3195-1 10 6 6 4254-5 10 | 10 10 | 3120-5 10 6 6 | 3976-8 9 | 8 8 || 3118-8 10 6 6 | 3971-4 3 8 8 2851-4 x 10 10 10 3963-9 10 | 8 8 2843-3 x 10 10 10 3928-8 6 6 6 2835-7 x 10 10 10 3919-3 8 a al 6 | 2766-6 10 10 10 3605-5 x 10 | 1G 10 2762°7 10 10 10 3593°6 x 10 | 10 10 Nicken. Nickel chloride gives its spectrum with great ease in the vacuum tube, all the principal lines of the spark spectrum of the metal showing both with and without the condenser, Bands are not very prominent, Pottox—The Vacuum Tube Spectra of some Metals. Principal Lines of Nickel. 261 Vacuum Tube. Vacuum Tube. ne Spans Wea Spark. Ra Nowe Ji. |) Watheis Jp | IN@ Tbs da |] WAI Ds af 5035°6 6 6 6 3947-7 7 4 4 4714:6 10 10 10 3243-2 7 4 4 4401-7 4 8 8 3233-1 8 8 8 3858-4 8 10 10 3217-9 7 n 1 3807°3 8 10 10 3134-3 8 10 10 3783-7 6 8 8 3102-0 8 10 10 3775°7 6 8 8 3101°6 8 10 10 3736:9 8 6 6 3080-8 7 8 8 3722°6 6 4 4 3064°7 7 8 8 3674-3 3 1 1 3057-7 8 7 7 3619°5 10 10 10 3054-4 7 7 7 3612:9 6 10 10 5050-9 8 7 7 3597°8 10 10 10 3038-0 7 8 8 3572-0 8 6 6 3012-1 8 10 10 35665 10 6 6 3003-7 8 10 10 3524-6 10 10 10 3002-6 6 6 6 3515-2 10 8 8 2992-7 7 4 4 3510°5 10 8 8 2944-1 6 6 6 3501-0 8 6 6 2913-7 6 6 6 3493-1 10 10 10 2821°3 4 6 6 3472-7 8 8 8 2802°8 7 4 4 3461-8 10 8 8 2795-6 7 4 4 3458-6 10 8 8 2546-0 i 7 7 3458-5 10 8 8 2510-9 8 8 8 3453-0 7 8 8 2441°8 D 1 1 3446-3 8 8 8 2437°9 7 7 7 3433-7 7 8 8 2416-2 7 8 8 3423-8 7 8 8 2394-5 a 8 8 3414:9 8 10 10 2270:2 4 4 4 3393-1 7 10 10 2264-6 4 4 4 3380°7 7 10 10 2216°5 4 4 4 3369-7 8 4 4 SCIENT. PROC. R.D.S., VOL. XUII., NO. XXI, 2s 262 Scientific Proceedings, Royal Dublin Soctety. CoBALr. Cobalt chloride gives its spectrum with great ease, all the principal lines of the spark spectrum of the metal showing in the photograph both with and without the condenser, though in many cases lines are intensified by the use of the condenser. Bands were not seen. Principal Lines of Cobalt. Wave Length. Spark. Vacuum Tube. With L. J. | Wave Length. Vacuum Tube. No L. J. | With L. J. 4868.0 4840-4 4813°7 4793°0 4780°1 4749°9 1663-6 1629°5 4531-1 412175 4092°6 4045°6 3998-0 3995°5 393671 3894-2 3873° 3527°0 8623°6 3506-4 3602-4 s.d. 3495-8 3489°5 347471 3465-9 3462°9 3453°6 3449°6 3449°3 8 10 Pottox—The Vacuum Tube Spectra of some Metals. 263 Principal Lines of Cobalt—continued. Vacuum Tube. | | Vacuum Tube. WEE Spark. 2 | WE Spark. | Length. ; Length. ; No L. J. | With L. J. | No L. J. | With L. J. | u = 314071 5 | 4 4 2531°9 2 1 D 3137-5 5 | 2 2 2528-7 | 7 4 7 3121°7 5 6 6 2525-1 fi 4 7 3086-9 6 6 3 2521°0 2 1 2 3072-5 6 leer: 6 2519-9 8 6 8 3044-1 7 | 8 8 2517:9 2 1 2 : 2954-8 8 [iQ 6 . || 2511-2 7 4 8 2943-2 6 | 2 6 2506°5 8 4 8 | 2871:3 7 | 2 6 2496°8 2 1 2 2825°3 6 2 4 2472-9 2 1 2 | 2694-7 8 8 8 2456-2 2 1 2 | 2663-6 8 2 8 2432-6 5 8 8 2653-7 7 0 4 2425-0 4 2 4 2648-7 7 | 6 6 2411°6 4 2 4 2632'3 8 4 6 2407-7 4 2 4 2618°8 4 4 4 2402+1 2 \ 2 2614-4 7 4 4 2401°6 2 1 2 2587-2 8 4 8 2397-4 6 2 4 2582°3 8 ie 8 2388-9 6 2 4 2580°4 8 | 4 8 2386-4 4 2 4 2564-2 8 cue’ Ser ae SS 2383°5 5 2 4 | 2562-3 2 6 10 2378-6 7 4 6 266071 re 4 8 ~ 2363°8 ih) 4 6 2559°5 8 4 8 2353°5 5 4 6 2546°8 7 4 q 2307°7 4 4 6 2542-0 8 2 8 2293-4 4 2 4 2540-7 6 2 6 || 2286°3 5 4 6 CaLcium. Calcium chloride does not readily yield a spectrum in the vacuum tube, and as a rule only three lines show in photographs, \ 4226°9, d 3968-1, and \ 3933°8, these lines being also the ultimate lines of the spark spectrum of 282 264 Scientific Proceedings, Royal Dublin Society. the element, but by taking special pains to heat the tube as much as possible by a Meker burner, and photograph the capillary tube just at the lower bend, close to the bulb containing the chloride, 1 got a good photograph showing a fair number of the calcium lines, and the bands in the red were strongly developed. It is probable that by stronger heating similar photo- graphs of strontium and barium might be obtained, though I did not succeed. The band in the ultra-violet is due to chlorine. Strong bands are seen in the orange and red, also from X 3600 to X 4100, due, no doubt, to calcium chloride. Principal Lines of Calcium. an Vacuum Tube. Soe Vacuum Tube. Length. Spark (> awe cea eee Length. Snare | No L. J. | With L. J. No L. J. | WithL. J. 6494-0 10 s.c. 0 0 4425°6 10 s.c. 2 4 6462°8 10 s.c. 0 0 | 4302°7 10 s.c. | 6 6 6439-4 10 s.e. 0 0 4226°9 w 10 n.c. 10 10 6162°5 10 s.c. 0 0 3968-6 w 10 n.c. 10 10 6122°5 10 s.c. 0 0 3933°8 w 10 n.c. 10 10 5589-0 10 s.e. 0 0 3737-2 wv 10 4 4 4586-1 4s.d. 1 1 37062 | w 10 4 2 4581-7 4s.d. 1 1 8644°5 2 2 2 4578°8 4s.d. 1 1 3630°8 1 2, 2 4627°2 4 3.¢. 2 3624-2 1 : 2 2 4455°0 10 s.c. 6 8 3179°4 x 10 bv. 10 10 4436-1 10 s.c. 6 8 3159°1 x 10 brr. 10 10 SrRoNTIUM. Strontium chloride yields a spectrum in the vacuum tube with difficulty, and only at the strongest heat of the Meker burner, when three lines photograph well, these being the ultimate lines of the spark spectrum of the element. The luminescence is occasionally a very deep carmine, and, as with calcium and barium, it does not extend up the capillary tube. The strong line at the extreme red is lithium, \ 6708'2. The water-vapour and chlorine bands are seen, and there do not appear to be any other bands. The ultimate line of magnesium, A 2852:2, is seen, but not the fainter pair seen in calcium. Pottox—The Vacuum Tube Spectra of some Metals. 265 Principal Lines of Strontirm. | Vacuum Tube. || | Vacuum Tube. No L.J. | With L.J. \ No L.J. |With L.J. =a Ie el eee 6408-6 IO >| | 0 4215-7 w 10 b*. 4 4 54810 | 10s. 0 | 0 4077-9 w 10d. 4 | 4 | 52383 | 10s. 0 0 || 3475-0 ¢ 10n. 0 0 4962-4 8s. 2 2 3464-6 10 br. 0 0 4855°3 2 | 2 2 3380-9 10 nr. 0 0 460775 | w 10 |. 20 10 3351°3 || x 3in: 0 0 _ 4305-6 w 10 by. 0 2 Barium. It is extremely difficult to get a spectrum with barium chloride, and the strongest heat of a Meker burner must be used; the luminescence is a brilliant green in the bulb, but does not extend up the capillary tube, and in the photograph only a few of the lines of barium show. Repeated trials were made, and no better results obtained ; possibly if an end-on tube were used, a more complete spectrum would be obtained. The chlorine and water-vapour bands show also a few faint bands, probably due to barium chloride. Principal Lines of Barium. Vacuum Tube. Vacuum Tube. aie ain Spark. eee Spark. | NoL.J. | With LJ. No L.J. | With L.J. | | 6497°1 10 s.c. 0 0 3993°6 8 0 0 5535°7 10 s.c. 2 2 3892-0 10 b. 8 8 4934-2 10 n.c. 10 10 3501-3 8 2 2 4554-2 10 b.r. 10 10 2335°3 4y. 2 2 4130°9 10 b. 4 4 2304°3 27. 2 2 Magnesium. Magnesium chloride gives a brilliant luminescence in the tube, but the oxide rapidly deposits in the capillary portion and renders it semi-opaque if much of the chloride is used. The metal is not sufficiently volatile to give a spectrum. ‘The line \ 2852-2 is remarkably persistent, and shows quite 266 Scientific Proceedings, Royal Dublin Society. strongly as an impurity in most of the spectra of the alkalis and alkaline earths; if more is present, the lines A 2802°8 and \ 2795°6 also show, so these three lines may be accepted as the ultimate lines of the vacuum tube spectra of magnesium. If any appreciable quantity of the substance is present, practically all the lines of the spark spectrum of the element come out, and there is little change on the introduction of a condenser. When much vapour is present, some strong bands show from A 3880 to d 8680. Principal Lines of Magnesium. | Vacuum Tube. | Vacuum Tube. Wave : Wave aes = Length. Spare || Length. SDS No L. J. | With L. J. NoL. J. | With L. J. | 5528-7 6s. 4 4 2928-7 10 n. 8 8 | 5188°8 10 s.x. 10 10 2915°6 10 n. 0 0 5172:9 9 s.r 10 10 2852-2 81 wl0 | wild 5167-6 | 8s. 10 10 2802-8 10r w10 | ul0 4703°3_| In 4 1 9798-2 | 81 a O° | 4481-3 | 10 b. 1 10 | 2795-6 101 | u2l0 wld | | | 4352-9 2n 4 1 | 279079 8x | 4 ieei| Oo. | | | i} S 3895°8 6n. 0 0 | 9783-1 4 | 4 | eeeeea | Sage 10 1 ii) oR | 4 4 | | | 3832:5 10r 10 10 2779°9 6 6 6 | 3829°5 10 n 10 10 | 2778°4 4 4 4 3336:8 8n 8 8 2776°8 4 4 4 3332°3 8n 8 8 | 3880 6 nb 1 nb 3330-1 6n 8 8 3870 = | | 3097-1 In 0 6 | 3830 | ee | | 10 nb. 8 nbr. | 3093-1 In 6 6 || 3800) | 3091-2 D ine 6 | 378 | | al psee oe | | 10 nb | g nbr. | 2942°2 In 0 Oil SAO) || | | 2988-7 = Oo | 0 | 3700) | | 5 | 2937-0 100 8 | 6 Il sap). || ocala | ese i | | PowvassiumM. The specimen of potassium chloride examined gave a brilliant lumi- nescence in the tube, but the photograph consisted of the lines of the spectra of sodium and lithium, together with the banded spectrum of water-vapour, and the lines of chlorine, together with one or two other lines, not yet Po.ttoK—The Vacuum Tube Spectra of some Metals. 267 identified; but there was only one line belonging to the spark spectrum of potassium, the double line XA 4047-4, 4044-3, but this line showed quite strongly ; the spectrum is not reproduced, as it will be further investigated. The metal rendered the capillary portion of the tube opaque, and could not be photographed. Principal Lines of Potassium. Vacuum Tube. Vacuum Tube. Wave Wave Length. Spark. eae a Eaaaonart es | Length. Spark. Rees ans | | No L. J. | With L. J. | No L. J. | With L. J. 7699°3 8s. 0 0 | 4047°4 10a | 10.. | 20 | 7665°6 Ss. 0 0 | 4044-3 10s. 10 10 | | | 5359°9 | 8s. 0 0 | 3447-5 10 | Oo | 0 5340-1 Bae cd 0 3440-5 6 Patience Bs 0 ; | eel ee | Sopim. Sodium chloride gives its spectrum with great ease and brilliancy in the vacuum tube, the luminescence being of an intense yellow colour. The metal was very easily volatilized, but rendered the capillary portion of the vacuum tube opaque, so that I failed to obtain a photograph of its spectrum. The spectrum of sodium chloride is not reproduced in the plate, but most of the lines are seen in the spectrum of lithium chloride, owing to a small amount of sodium present as an impurity. The introduction of the Leyden jar made practically no change in the spectrum of this element. Principal Lines of Sodium. Vacuum Tube. . | Vacuum Tube. wie || ers =| PGR) oe No L. J. | With L. J. | No L. J. | With L. J. | | | 6161-1 | 8s. 1 | 1 || 4979-3 | Ge. | 1 | 1 6154°6 8s. 1 1 || 4752-2 2s. Oo I =O 5896°2 10s. 10 10 4748-4 Qs. o | 0 5890°2 10s. 10 10 4669°4 3n. 1 1 5688°3 6n. 6 6 || 4665-2 38. 1 1 5682-9 6s. @ | 6 |i ganpa 10s. i@ | a 5153-7 5s. O. | 0 3302-5 10s. i | % | 5149-2 5s. o. | 0 || 2852-9 10s. 1 1 4983-5 6s. 1 1 2680:5 8s. 0 0 268 Scientifie Proceedings, Royal Dublin Society. Lirxium. Lithium chloride gives a beautiful spectrum without difficulty, the luminosity in the tube being of a bright red colour, and a good supply of vapour was easily maintained by the occasional application of a Meker burner. The metal did not readily give the spectrum of lithium, as it is not sufficiently volatile at the temperature of the Meker burner. The red glow of the lithium was seen in the bulb, but it did not extend to the capillary tube, and the photograph only showed one line of lithium, A 4972-1, the other lines being due to more volatile impurities in the metallic lithium used, and were the lines of hydrogen and sodium, together with helium, A 4026°3; magnesium, A 2852°2; mercury, \ 2536-7; and manganese, dA 2801-3, A 2797°8, and X 2795°3. ‘These are, no doubt, the ultimate lines of these impurities, ; but, if so, it is very remarkable that-they are not the strongest lines, and that the lines of manganese are not the ultimate lines of the spark spectrum of that element, and it is certainly strange that, out of the whole spectrum of manganese, only three inconspicuous lines should show. The spectrum of metallic lithium sparked in air is reproduced on the plate for comparison with the vacuum tube spectra of the chloride. Principal Lines of Lithium. Vacuum Tube. : Vacuum Tube. yg | sie | ee | spar ——— NoL.J. | With L.J. | | NoL. J. | With L.J. | Hieesteoves Ngee ore |e | 6708-2 10s. 10 10 | - 3915°2 4 4 6103°8 10 10 10 3794°9 | 1 1 4972°1 4 4 4 | 3239-8 | 5n. 10 10 4602°4 10 n.r. 10 10 2741-74 | 2 4 | 4 4273-4 4n. 4 4 | 2562°6 | 1 1 4132-4 6n. 6 6 | 2476-1 | 0 | 1 SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. METALLIC VACUUM TUBE SPECTRA. Wave length Scale. ati ie idl it Pb ff) era an Pb Cl, ll i (3 eae " ili TH Pe Mn ioe PA AU 0 hd TTR TRG A Mn Cl, (i i ot I| 1) iim) i itt II Fe ee eee ee canny Fe Cl, WN LSM tical eee ee ern a, il ll || Ca Cl, | EW Us ay 1) ae n wi ' ur " 1 1‘ iil en vw chthf anfllfffpomeca |p a 4! ras al 4 \1 | ud Peasants mee a SCS eases) aeeeees (OU Paeere ) Coen Sr Cl, (|) ot ce ftamenmieccsmans| afm a Bach, | | iff) tefemestmiumefeememscsn cil aces ue i bs [lp jedpeenphegpfemmaen dG a af own a : Li Cl a et PP oe tefemefemeseamen af yo an ne Li Dio) FT| Mg Cl, Pelee Apaches | LF coi Gh tel) aval A [| 4 | I! jase dead ete Ni eee NOT DUTT TE eae ee ce eT Ni Cl, LES TE A MM | : MN Jue a leet Co 1 i wt atte hi atl Co Cl, | n “MA: 7 | {UIA aN bili ht (I ae {YUU MUO EEE Cr | een AONUMA 0 11 Cr O,Cl, | i ii Tl ] io i 0 Ym SE EP UT OA A AR PLATE XXII. aA gig w a4qdq0@ qaqa @dq @ : eli rye } rt os , { i y h is Byte ie WaLoddS adNAL WANOVA ONIHdVYOOLOHd YOA SNALVUVddV ALATAINOO THXX @LV1d TNX “IOA “SN “OOS NITANG “AY ‘OOUd “LNAIOS a SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. Mn Cl, bf ot HATH | Pb Cl, [| both Mlbed MD ff wis CuCl, eo 0 LiCl Ls bel TTD Mh HB) PLATE XXIV. No. II. SPECTRA GIVEN BY LESS THAN ONE-TENTH OF A MILLIGRAM. Mn Cl, eiadeamfieccerenc en MP fa ce ‘Pb Ol, f i He esceaaficae | Cu Cl, | , {oom ee My Sorte No. III. SPECTRA GIVEN BY THE LAST TRACES. Mn Cl, tit ae eann Pee a | oe ong a 1 wa Pb Cl, 1 Pe geass caer nn Ty row zm m4 1 nna Cu Cl, I (1 gmnnies 2 canine | | aaa ua gt 1 iene 1 0b Tas grr i a | 1 Hiow 1 1 te | Li Cl ! SCIENTIFIC PROCEEDINGS. VOLUME XIII. .1. A Seed-Bearine Ivish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, p.so., F.1.s. (Plates I-III.) (March, 1911.) 1s. 2. Considerations and Hxperiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorez H. Peruysrivaes, B.SC., PH.D. (March, 1911.) 1s. 3. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wimu1am Brown, 3.s0. (April 15, 1911). 1s. 4. A Thermo-Hlectric Method of Cryoscopy By Henry H. Dixon, so.p., F.r.s. (April 20, 1911). 1s. _ 5. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its pa Stage. By Wiuuiam J. Lyons, 8.4., A.B.0.S0. (uonp.). (May 16, 1911). 6, Radiant Matter. By Joan Jony, sc.p., r.z.s. (June 9, 1911.) 1s. 7. The Inheritance of Milk-Yield in Cattle. By James Winson, m.a., B.Sc. {June 12, 1911.) 1s. 5 8. Is Archeopteris a Pteridosperm? By T. Jounson, p.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. 9. The Occurrence of Archaopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. JOBNEON) D.sc., F.L.S. (Plates VII., VIII.) (June 28, 1911.) 1s. 10. Award of the Boyle Medal to Prorsssor Joun Jony, u.a., $0.D., F.R.S. (July, 1911.) 64d. 11, On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. ‘By Joan Jony, sc.p., F.x.S., and Louis B. Smyru, B.a. (Plate IX.) (August, 1911.) 1s. 12. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newetn ARBER, M.A, F.L.S., F.G.S. (January, 1912.) Is. SCIENTIFIC PROCEEDINGS—continued. 18. Forbesia cancellata, gen. et sp. noy. (Sphenopteris, sp., Baily). By T, JoHNSON, D.so., F.L.Ss. (Plates XIII. and XIV.) (January, 1912.) 1s. 14. The Inheritance of the Dun Coat-Colour in Horses. By James Witson, M.A., B.SC- (January, 1912.) 1s. 15. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jamzs H. Poxtok, p.so. (Plates XV. and XVI.) (February 21,1912.) 1s. 16. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, sc.p., r.r.s., and W. R. G. Arzins, u.a. (February 21,1912.) 6d. 17. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, Fes. (Plates XVII.-XIX.) (March 26,1912.) 1s. 18. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Drxon, sc.D., r.R.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. 19. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Dixon, se.p., F.n.s., and W. R. G. Arxins, u.a., atc. (April 9, 1912.) 6d. 20. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jounson, v.sc., F.u.s. (Plates XX. and XXI.) (April 12, 1912.) 1s. 21, On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part [I.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By James H. Poxttox, D.Sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s. 2 DUBLIN : PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIE (W8.), No.22. MAY, 1912. THE ULTIMATE LINES OF THE VACUUM-TUBE SPECTRA OF MANGANESE, LEAD, COPPER, AND LITHIUM. BY GENEVIEVE V. MORROW, A.R.C.Sc.1. [COMMUNICATED BY JAMES H. POLLOK, D.SC.] (PLATE XXIV.) [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: TNL PUBLISHED BY THE ROYAL DUBLIN SOCIETA in : LEINSTER HOUSE, DUBLIN. ( Aran : WILLIAMS AND NORGATE, ena \ / 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. NG Tale 1912. nal Museu Price One Shilling. Roval Dublin Soctety. FOUNDED, A.D. 1731. INCORPORATED, 1749. EO EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 ‘p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested +o forward their Communications to the Registrar of the Royal Danie Society at least ten Jays prior to each Meeting, as no Paper can be ‘set down for reading until examined and approved by the Science ‘Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Kditor. [ 28 7 XXII. THE ULTIMATE LINES OF THE VACUUM-TUBE SPECTRA OF MANGANESE, LEAD, COPPER, AND LITHIUM. By GENEVIEVE V. MORROW, A.R.C.8c.1. [COMMUNICATED BY JAMES H. POLLOK, D.SC. | (Prate XXIV.) [Read Fesruary 27. Published May 11, 1912.] ReceEnr advances in spectrum analysis have made it desirable that we should have an accurate knowledge of the ultimate lines of vacuum-tube spectra, as so far no accurate determinations of this kind have been made; and without a knowledge of the ultimate lines of the elements, it is often impossible to determine with certainty the origin of the lines of a complex spectrum. It has long been known that very minute quantities of certain elements give brilliant spectra in vacuum-tubes, often to the exclusion of the spectra of substances present in large quantities, so that it is also desirable to have an accurate knowledge of the absolute quantity of each element necessary to develop a particular spectrum under given conditions. The following investigation has been undertaken to determine these two points in respect of the elements manganese, lead, copper, and lithium. The spectra of most of the elements have been obtained under various conditions, and the wave-lengths of the lines determined with accuracy. Quantitative analysis by means of the spectroscope was first successfully applied by Sir Walter Noel Hartley’ to the spark-spectra of the elements, and he investigated the quantitative spectra of many substances by sparking solutions of known concentration, and has tabulated the lines which appear when certain percentages are present. This work was continued by Drs. Pollok and Leonard,’ who determined the quantitative spark-spectra of all the remaining common elements, and of many of the rare elements. Investigations of this kind have also been made by M. de Gramont and others, so that our knowledge of the quantitative spectra and ultimate lines of the spark-spectra is now fairly complete. Sir Walter Hartley also indicated the importance of the persistency of 1 Phil. Trans. Roy. Soc., 1884, vol. clxxy., Part 11, pp. 325-342. * Scient. Proc. Roy. Dub. Soc., 1907-1908, vol. xi., pp. 217-236, 257-279, 331-337. SCIENT, PROG, R,D.S., VOL. XIII., NO. XXII. 27 270 Scientific Proceedings, Royal Dublin Society. the lines in a spectrum. ‘To detect the presence of a trace of a substance the most persistent or ultimate lines of that substance obtained under the same conditions require to be known; that is, those lines which are the last to become extinct as the quantity sparked is diminished. ‘The absence from a spectrum of these lines for a particular element proves conclusively the absence of that element, no matter how many other lines in the spectrum appear to coincide with others of that element. As an example, suppose the spectrum of a certain sample of zine has been obtained, and the wave- lengths of the lines measured, if none of these correspond with the ultimate lines of cadmium, that is conclusive proof that there is not the smallest trace of cadmium present, no matter what lines apparently correspond with the other lines of cadmium. In order to make spectrographic analysis com- plete it is obvious that the ultimate lines of all elements under all conditions require to be known. The vacuum-tube was first invented by Geissler, and greatly improved by Plucker and Hittorf,! who found that when a capillary tube was placed between two wider portions, the whole exhausted, and a current of electri- city passed through, the brilliancy of the illumination was enormously increased in the narrow portion. ‘These tubes have long been extensively used for obtaining the spectra of gases, but they are now equally useful for the spectrographic analysis of solid substances, owing to the recent improve- ments by Dr. Pollok. His tubes, which somewhat resemble those of Plucker, were used throughout the present investigation. They are composed entirely of quartz, and are open at each end, having the electrodes sealed into glass, and attached by rubber tubing, as described in his paper, “ On the Vacuum- Tube Spectra of the Vapours of some Metals and Metallic Chlorides.’ The general arrangement of the apparatus in the present experiments, and the method of working, were substantially the same as those described in the paper referred to. ‘The fact that the tubes are made of quartz enables the whole of the ultra-violet region of the spectrum to be photographed with facility. The presence of a much smaller quantity of an element may be detected by the vacuum-tube spectra than could possibly be determined by the ordinary balance. The apparatus used consisted of a vacuum-tube, spectrograph, coil, condenser, pump, and driers. ‘The spectrograph was one of Sir Walter Hartley’s design, as used in his researches described in the Scient. Trans. Roy. Dub. Soc., 1882, Vol. L., pp. 231-238, and having quartz lenses of 15 inches focal length. 1 Phil. Trans. Roy. Soc., 1865, vol. cly., pp. 1-29. * Scient, Proc. Roy. Dub. Soc., 1912, vol. xiii., p. 202. Morrow—Spectra of Manganese, Lead, Copper, and Lithium. 271 The Apps coil used gave a 12-inch spark ; and the condenser consisted of a sheet of tin foil about 15 inches by 18 inches on either side of a sheet of glass. The drying tubes contained phosphorus pentoxide and caustic potash to absorb any acid vapours which might be liberated, and were connected with a Geryk vacuum-pump. During the experiments the pressure in the tubes was about three or four millimetres, which was observed by having a tube from the connexions set vertical in a small trough of mercury, with a barometric tube for comparison. Sir Walter Hartley has shown that in almost all cases the spectra of the solutions of salts are the same as the corresponding metals: the non-metallic constituents do not affect the spark-spectra ; and Dr. Pollok has proved that, with the chlorides in the vacuum-tube spectra precisely the same lines are obtained as with the vapour of the metal with or without the lines of chlorine, and that these lines agree with those of the spark-spectra. Chlorides were used in preference to other salts, because they are easily obtained, and are readily volatilized without decomposition. Four new quartz tubes fitted with new platinum electrodes were used. Into the lower bulb of each tube was put a drop of the distilled water used for making the solutions required for the experiments. The electrodes were connected, the tube exhausted, and the current passed, the capillary portion being heated all the time during the passage of the current, and a second burner used for warming the lower limb. Photographs were taken of the spectrum, giving five minutes’ exposure in each case. To facilitate the identification of the lines, on the centre of each photograph the spark-spectrum of cadmium was superposed, using a Hemsalech coil for the removal of air lines. The exposure in this case was for one minute. On comparing the spectra which are superposed it will be found that unless the two sources of light be placed in the same position with regard to the slit, and the rays fall on it at the same angle, the photographs of the spectra will be displaced relatively to each other, but if the image of the vacuum-tube be focused on the slit by means of a spherical lens, and this lens be not moved before the cadmium spectrum is photographed, the two spectra on the plate will be quite correctly placed in relation to each other. Care should be taken that tie light source, the slit, and the centre of the collimating lens are in the same straight line as seen by vertical pointers attached to the instrument. Of course in each case the cadmium electrodes and the centre of the capillary portions of the tubes were equidistant from the slit. ‘The lines in the cadmium spectrum were shortened by means of an aluminium sliding shutter with a horizontal V-shaped noteb. The photographs obtained from the distilled water showed water-vapour 272 272 Scientifie Proceedings, Royal Dublin Society. bands, and hydrogen lines, but no trace of any lines due to lead or any other impurities, this proving that the tubes were quite clean and the water pure. Standard solutions containing one gramme of the metal per litre were made of the chlorides of manganese, lead, copper, and lithium respectively. The solutions of the substances were then introduced into the tubes, the method being precisely the same for all. The stopper containing the electrode was detached and 0°1. c.c. of the standard solution introduced into the lower bulb of the quartz tube from a clean burette. The other end of the quartz tube with the attached stop-cock was joined to a Bunsen pump, the tube heated and a current of dried air drawn through, the solution in the tube being kept as near as possible to the lower limb of the capillary portion, and heated gently until all the water was driven off. The tube was then cooled in a current of dried air. When cold, the tubes were disconnected from the Bunsen pump, the second electrode attached, and the tube connected to the Geryk pump, exhausted, and the current passed as with the distilled water, having the capillary portion and the lower limb of the quartz heated to volatilize the chlorides ; five minutes’ exposure was given for each photograph, and the spectrum of cadmium was superposed as before. The spectrum given by this small quantity (00001 gramme, metal) consisted of many lines, manganese especially giving a great number (Plate XXIYV., No. 1). In all the photographs there were lines due to hydrogen and water-vapour, and some showed bands due to nitrogen which had not been expelled from the tube owing to the smallness of the quantity of metallic vapour present. In the case of the new gases—helium, argon, neon, krypton, and xenon—Collie and Ramsay have shown that the presence of hydrogen greatly influences the spectrum obtained, as under certain conditions of pressure the spectrum of the rare gas is entirely invisible and only that of hydrogen shows; but so far as I have observed their presence in no way affects the spectrum of metals; and it is very difficult to eliminate the last traces of hydrogen and water-vapour without the introduction of nitrogen. In order to avoid the presence of nitrogen and to take another photograph with each tube, the lower limb was opened and a small glass rod, which had been moistened with strong hydrochloric acid, was inserted, allowed to touch the side of the tube, and then withdrawn. This was repeated with each tube, which was then closed, and photographed as before. ‘The small quantity of hydrochloric acid vapourised when it was heated, and drove out any nitrogen present; it also combined with and helped to volatilize any of the metal which might have been reduced during the experiment. Of course most of the chloride had probably disappeared out of the tube ; but apparently not all, as there still remained many lines in the photographs, due to the metal, Morrow—Speetra of Manganese, Lead, Copper, and Lithium. 273 together with hydrogen lines and water-vapour bands, but none of nitrogen. (Photograph II.) The tubes were then opened at both ends by disconnecting the electrodes, and each quartz tube was boiled with dilute hydrochloric acid, washed with distilled water, and dried by means of the Bunsen pump as described. A little strong hydrochloric acid was then introduced into the lower limb of each tube by means of a glass rod as before, the tubes were closed, exhausted, the current passed and another set of photographs taken. Most lines had now disappeared, but the ultimate lines can be seen on the original plate. The electrical evaporation of the electrodes was seen by the deposition of the platinum as a mirror on the quartz tubes in the region of the electrodes ; but it in no way affects the spectra obtained, as there are no lines showing which are due to platinum. The panchromatic plates of Wratten and Wainwright were used for taking the photographs, and were subsequently developed with amidol. The linear measurements of the lines were obtained by means of a micro- meter reading to ;>s00 Of an inch, but being certainly accurate to ,.,; of an inch. ‘The cadmium line 14800°1 was taken as the starting-point for the measurements in each case; and the cadmium lines were measured at the same time as the spectra of the chlorides. The cadmium lines as numbered by Mascart were taken as the fiducial lines and their linear measurements corrected from a curve previously obtained for the particular spectrograph used. ‘The corrections for the other linear measurements were obtained, and the corresponding wave-lengths observed by interpolation between these known cadmium lines. The wave-lengths obtained, and derived in this manner, were compared with those of Eder and Valenta, and the lines were thus identified. In some cases there were no lines to correspond in their wave-lengths, but these lines were recorded by Wxner and Haschek, and in these cases I adopted their wave-lengths. The original photographic plate of Plate XXIV., No. II, was examined, and the lines appearing on it were noted, and are marked ‘u,’ in the last column, provided that they are not the ultimate lines of the metal which are marked ‘u,’ and appear on No. III. The comparative intensities of the lines of No. I are indicated by ‘S, ‘m,’ ‘f,’ and ‘ff,’ signifying ‘strong,’ ‘medium,’ ‘faint,’ and ‘ very faint. In the last column these intensities are given more accurately by numbers ranging from 10 to 1, the strongest line or lines being marked 10, and those exceedingly faint 1. ‘The intensities of the spark-spectra as observed by the authors of the accepted wave-lengths are given in the next column for comparison. 274 Scientific Proceedings, Royab Dublin Society. In quantitative spectra obtained by sparking solutions, the degree of persisteney of lines is indicated by means of Greek letters, thus— o lines seen with strong solutions. O94) > 2s) percent? solutions: X » » » ‘1 per cent. solutions. ww , » » ‘01 per cent. solutions. Ww 4» » > ‘001 per cent. solutions, In representing the persistency of the lines of vacuum-tube spectra I have adopted these symbols when the absolute quantities necessary to develop the lines are known, and assign to them the following values :— represents the presence of -0001 grammes. Xx ” ” ” 99 ‘00001 ” wD > 5 9 OOOOH — y OQ » : gg COOOOOOL Thus all the lines of manganese, lead, copper, and lithium obtained in No. I (Plate XXIV.) are ¢ lines. On the Continent ‘w’ has been used to represent the ultimate lines of an element, but when the actual quantity of a substance present is unknown, the lines might be graded in accordance with their persistency, thus— wu, representing the ultimate line or lines, us representing the next in order of persistency, u; representing the next in order of persistency. This notation would then approximately correspond with the previous notation, and can be used when the absolute quantities are not known; and I have adopted it when necessary in the present investigation, and the persistencies are thus recorded in column 8 of the tables. MANGANESE. The standard solution of manganous chloride was prepared by dissolving 2'824 grammes of pure manganous carbonate in hydrochloric acid, and diluting the solution to 1 litre with distilled water. When the first photograph (Plate XXIV., No. I.) was being taken, there appeared in the tube for about four minutes a green luminescence tinged with pink. On viewing this with the hand-spectroscope a great number of lines were visible. As may be seen, many of these lines appear in the photograph, thus showing that this extremely small quantity (0001 gramme) of the metal will Morrow—Spectra of Manganese, Lead, Copper, and Lithium. 275 give almost a complete spectrum in a vacuum-tube. In No. II are seen many lines which appear when even still less than 0001 gramme of the metal is used, and No. JII shows the ultimate lines of manganese, appearing when the most minute trace of the element is present. ‘These ultimate lines did not appear at all on the photograph of the spectrum taken when the tube had been boiled for a second time with hydrochloric acid. When the spectrum was being photographed for the second and third time, the colour in the tube was rose, the grecn luminescence seen before having disappeared. Lines due to chlorine appear in all the photographs. A very characteristic group of three lines, A 2801°3, \ 27985, and d 2795°3, which are due to manganese appear in Dr. Pollok’s vacuum-tube spectra! of manganese, potassium chloride, barium chloride, and metallic lithium, and as they are not the ultimate lines of the spark-spectrum of manganese, and no other lines of manganese appear, their presence seemed peculiar. They may be seen on Dr. Adeney’s photograph of the grating spectrum of manganese,’ but are not nearly so strong or characteristic as in the vacuum-tube spectra. From my photographs it is evident that as these three lines are strongest on the last photograph of manganese, they are the ultimate lines of the vacuum-tube spectrum of that substance, and are quite different from the ultimate lines given by the spark-spectrum, which are A 2605°8, X 2593°8, and \ 2576:2. The characteristic group of three lines referred to above are thus accounted for as being due to the merest trace of manganese. z “ 8 & | fe ga ere Persistency and RES Sate! ge oS 2s Intensity. Sed aS 3é 2g Element. ean SS} Sale aS Bo gs ss | Vacuum Mo = r=) 3 43 ‘ S i) = iS) S| = > Spark. awe 205:00 | Cd [5] | 157°60 S 6550 H | 6563°0 20 10 15995 | Ca [1] 6439-3 Gl | 183°55 f 5425-0 Cl 423°4 10 2 189:70 | f 5226-5 Gl | Gane 6 3 193-95 | Ca [4] 194-44 | 5086-1 200°75 f +21 4902°5 Cl 4903°2 1 200:°95 f + 20 4897°2 Cl 4895-5 2 202°40 |S +14 4866-0 H | 4861-5 10 203°85 m +11 4825:0 Mn | 4823°7 o 10 8 1 Scient. Proc. Roy. Dub. Soc., 1912, vol. xiii., p. 253. ? ‘Trang, Roy. Dub, Soc., Ser. 1, 1901, vol. vii. Plate XXVII. 276 Scientific Proceedings, Royal Dublin Society. pee a treke oye ze 42) Sete | UR 204°46 m + 09 4810°5 Cl 4810°2 9 8 204°90 Cd (5) 204°98 48001 205°00 NS) + °08 4797°5 Cl 4794°6 10 10 207°35 ff +12 4740°0 Mn 4739°3 6 1 214°64 f + ‘21 4573°0 N 4573°7 2 21850 ff + +26 4490°3 N 4489°6 il 220:05 m + 127 4458°8 Mn 44584 4 us 5 226°05 S) + °35 4342-8 Cl 43438 10 10 227-85 m $+ °36 4308°8 Cl 4307°6 8 iii 228°73 f£ +37 4292°2 Mn 4292-4 2 1 231:00 m + 142 4251-6 Mn 4251°9 2 5 231°65 m + +43 4240°0 Mn 4239-9 5 232°00 m + °43 4234:0 Mn 4935°3 5 233°60 ff 4°44 4206°3 Mn 4206°5 2 1 238°05 8 = 5 il 4130°7 Mu 4131°3 4 8 2389°95 f + *52 4100°2 Mno 4100-1 1 uz 2 241°40 fi + 154 40777 Mn 4077°9 1 2 242°80 ff + +65 4056°5 Mn 4055°7 co 6 1 243°45 f + 67 4046°4 Mn 4045°3 5 2) 243-85 m +97 4040°7 Mn 4041°5 ao 6 6 244°40 8 + :58 4032°3 Mn 4033°2 o 6 8 244°60 S + °58 4029°8 Mn 4030°9 x 8 ue 8 246°95 8S Ca 247°58 3994°1 247°65 ff HL o(}8} 3983°8 Mn 3983°1 2 iL 262°75 ff + °60 3912°0 Mn 3911°6 2) 2 256°10 ff + °58 8866°7 Mn 8865°8 1 1 256°65 Ss + -58 3860°7 Cl 3861°0 10 10 257°35 8 + °68 8850°3 Cl 885174 10 10 257°80 s + *58 3844°7 Mn 8844-1 4 uw 8 258°70 iS} + :57 3833-2 Mn 38384:0 ue 8 259°15 f + 67 3827-2 Cl 38827°8 5 3 259°50 m 4+ 57 3822°9 Mn 8823°6 » 6 5 259°75 f +°57 8819°5 Cl 3820°4 5 2 260°60 f + °56 3808°8 Mn 3809-7 4 ug 2 Morrow—Spectra of Manganese, Lead, Copper, and Lithium. 277 z ae Bec 86 EY Element. oe er ae gee ae SE | Spmk. | ie 260°85 |S + °56 3805°3 N 3804°8 10 261-45 | £ + °56 3797:9 Mn 3798°3 1 D) 262-10 | iF +55 3789°6 Mn 3790-3 4 1 26285 | ff 955 3780°5 Cl 3781°4 5 1 265°30 | m +54 3749°5 Cl || 3750-1 5 5 268-95 | £ 4+ +52 3705°4 Mn 3706°2 4 2 270:00 | m +°51 3692°9 Mn 3693°8 4 4 973:05 | f +750 3657°5 Mn 3658-0 1 3 273°80 |f + -49 3650°0 Mn 3650-0 1 3 277-25 | Ca [9] 277-72 3611°8 Q77°55 | m +47 3608-0 Mn 3608-6 6 ur 6 279°60 | £ 4°47 3586°3 Mn 3586-7 6 uw 3 280°50 | m 4°47 3577°0 Mn 3578-0 6 u? 6 28115 |S + °47 3570-0 Mn 3570°2 8 uz 8 283-20 |S 4°47 3549-0 Mn 3548-1 10 uz 9 28480 | m + +46 3532°8 Mn 3532-1 10 uw 7 288-25 |S + +46 3497°3 Mn 3497-7 8 7 989-00 |S + +46 3490-0 Mn 3488-9 @ 10 8 289:65 |S + °46 3483°3 Mn 3483-0 » 10 8 290°55 |S +46 3474-4 Mn 3474-2 10 9 291-25 | Cd[10] | 291-70 3467°8 291:90 |S Fi Of05 3460°2 Mn 3460°5 @ 10 9 29385 |S + 48 3441°9 Mn 3442-1 $ 10 10 297-90 °| Cd [ll] | 298-46 3403°7 301-60 | m +67 3370°3 N 3371-2 10 30355 | m 4°57 3353°3 Cl 3353°4 5 5 305°50 | f + 158 3336°6 Mn 3336-5 2 2 306°35 | m + °58 3329-6 Cl 3329°1 5 4 307°90 | m + 58 3316°2 Cl 3815°5 4 5 308°75 | f + 759 3309°0 N 3309-4 3 31545 | Cd 316708 | 3252°6 315-75 | Cd [7)) 516-33 3250°5 317-50 | m + +59 3236°5 Mn 3236°9 3 4 318°55 | m + 759 3228-2 Mn 3228-2 6 4 SCIENT. PROC. R.D.S., VOL. XI, NO. XXII, 2u 278 Scientific Proceedings, Royal Dublin Society. aa |a| ie | oe gia aes 3 Bs Element. BS A ag = “E ES £ 5 5 5 Shopvik | Vacuum ss = o AE = pare tube. 329-35. | f +64 | 3147-3 Mn | 3148-3 1 2 331-10 | f +°65 | 3134-9 N 3135-7 2 333-40 | m +66 | 3118-0 H.0 | 3117-4 5 4 337-35 | S bv +°68 | 3090-1 H20 | 3089-3 6 8 338-55 | m +-69 | 3081-6 H.0 | 3081-0 5 6 340°60 | m + °70 3067°7 H.0 3067-2 5 6 341-10 | S bv +:70 | 3064-4 H20 | 3064-6 4 8 341-80 | f +°70 | 3059-6 Mn | 3059-1 3 2 343-10 |m +71 | 3050-8 Mn | 3050-7 4 5 344-20 | f +°71 | 3043-4 Mn | 3043-4 2 uz 3 344-95 | m +:72 | 3038-6 Mn | 3038-6 3 5 345-45 | m +°72 | 3086-1 Mn | 3035°5 3 5 346-05 | S +°72 | 3031-3 Mn | 3031-2 6 8 346-35 | S 4°73 | 3029:2 Mn | 3029°5 2 7 347-80 |S +°73 | 3019°6 Mn | 3020-0 6 7 35390 | Cd [15] | 354-65 | 2980°8 354-70 | m +°75 | 2975-6 Mn | 29766 3 6 35915 |S +°76 | 2948-6 Mn | 2949°3 | x10 up 10 36010 | m +°76 | 2949-4 Mn | 2943-2 3 6 360°75 |S +°76 | 2938-4 Mn | 2939-4 8 uz 10 361-85 | 8 +°76 | 2932-0 Mn | 2933-1 8 up 10 363-65 | m +°77 | 2921°3 Mn | 2921-4 1 ur 5 367-60 | S +°77 | 2899-0 Mn | 2898:8 3 8 36780 | 8 +-77 | 2897-9 Mn | 2898-8 3 7 368:85 | 8 +°78 | 28920 Mn | 2892°5 4 ue 7 369-45 | 8 +°78 | 2888-6 Mn | 2889-5 6 7 369°90 | 8 +°78 | 2886-3 Mn | 2886-8 6 ur 8 370°85 | S$ Cd +°78 | 28808 Ca 2880-9 37120 | 8 +°78 | 2879-0 Mn | 28795 | » 6 8 37240 | m +°78 | 2872-4 Mn | 2873-1 3 6 37290 | 8 +°79 | 2869-5 Mn | 2870-2 4 7 377-40 | m +°79 | 2845-1 2 378-95 | Cd [16] | 379°75 | 2837-0 380-20 | m +°78 | 2830-6 Mn | 2830°8 3 ur 6 Morrow—Spectra of Manganese, Lead, Copper, and Lithium. 279 2 B sd a istenc g Ad aon E E a8 Element. uf Chienty =) 246 = 25 Ee 8s 2 § g Vacuum s 4 2 Ss Ae S Spark. tube. 38140 | £ LE itl 2824°5 Mn 2824:8 2 3 383°20 | m 4°75 2815°3 Mn 2815:2 3 5 383-70 | m + °74 2812°5 Mn 2812°8 3 uz 45 385°10 | m +°71 2805°5 Mn 2805°5 5 4 385°85 |S ae rAl 2801-6 Mn 2801°3 p) u 9 386°50 |S + °70 2798-2 Mn 2798-5 2 uy; 10 387:05 | § + +69 2795-4 Mn 2795°3 4 ui 10 389°60 | £ + °66 2782°6 Mn 2782°3 2 2 390°90 m + 64 2776:0 Mn 2775:9 2 4 392-40 | m +61 2768°7 Mn 2768-6 3 5 39365 | m + 60 2762-8 Mn 2762°3 2 4 396°50 | Cd [17] 397-05 2748-7 398-75 | £ + °56 2737°6 Mn 2737-6 2 3 400°60 | m 4°57 2728°7 Mn 2728°6 3 5 401-45 | m 4°57 2725°6 Mn 2726°0 2 4 402°45 | § + 58 2719°9 Mn 2719°6 3 7 404-25 | § +759 2711°4 Mn 2711-7 5 7 404°50 | m 4°59 2710°3 Mn 2710:4 3 6 404°85 | m + 59 2708'8 Mn 2708°5 4 6 405-45 | § + 759 2706-0 Mn 2705-7 6 7 406°35 | § + -60 2702°3 Mn 2701°7 6 8 407-75 | m + 60 2695°3 Mn 2695°4 3 5 409°35 | m +61 2687°9 Mn 2688°3 6 6 411/00 | § + 62 2680°4 Mn 2680°4 3 7 412°30 | m +°63 -| 2674°8 Mn 2674°8 2 6 412-70 | § +63 2673-0 Mn 2672°8 > 6 7 414:00 | § + °64 26671 Mn 2667°0 4 8 416°60 | m + 65 2655°7 Mn 2655°9 4 6 417°30 | m + 65 2652°6 Mn 2653:0 3 5 417-70 | m + °65 2651-0 Mn 2651-1 3 4 420°25 | § + °67 2640-0 Mn | 2639-9 a) 7 420°60 | § +67 2638°5 Mn 2638-2 6 8 422:05 | § +68 2632°0 -Mn 2682°5 6 8 423°60 |S + -68 2625-7 Mn 2625-7 6 8 280 Scientific Proceedings, Royal Dublin Society. soa Pee | ae | Bs ge ee ee | 23 gE Bp | Element. | 8ry = er eelos Ss lacs 8) | Spans, | ese A rs eS b 425-45 S + °69 2618-0 Mn 2618°2 p 6 8 427°25 SS) +°:70 2610°3 Mn 2610°3 8 8 428°30 ) poral 2600°7 Mn 2605°8 w 6 um 9 430-00 m +°72 2598°9 Mn 2599-0 8 6 431:30 S + °72 2593°3 Mn 2593°8 w 1d u, 9 432°10 m + 13 2590-71 Mn 2590°2 2 5 432°45 m +73 2588°8 Mn 2589°1 3 5) 433°30 f +73 2585°2 Mn 2585°6 1 3 433°60 f + °73 2584:0 Mn 2584-5 2 3 433°90 f +°73 2582-7 Mn 2583°0 2 3 434°95 m +74 2578°7 Mn 2579-0 3 4 435°65 SS) +74 2575°6 Mn 2576°2 » 10 u 9 436°45 Cd [18] 437°20 2573°1 438°80 bs) +°75 2563°3 Mn 2563°7 5 7 440°10 s +°75 2558°4 Mn 2858°6 4 a 440°60 Ss) +75 2556°3 Mn 2056°6 3 7 442°65 m +775 2548°5 Mn 2548°8 3 b) 444-05 i) +75 2543°1 Mn 2543°3 3 7 445°45 m +75 2537°8 Mn 2538°0 2 5 446-00 f +75 2535°7 Mn 2535-7 2 3 450°10 f + 4 2520°4 Mn 2520°5 2 3 451:10 f ceaartia: 2516°6 Mn 2516°8 2 3 451°85 f +74 2513°9 Mn 2414°3 2 2 453°55 m +°74 2507°7 Mn 2507°7 2 4 455°90 m +°74 2499-0 Mn 2499-1 4 5 463°30 ff +74 2472°6 Mn 2472°9 2 1 464-05 | Cd [20] | 464-78 | 247071 46510 f + °73 2466°6 Mn 2466°8 2 3 469°15 SS) +73 2452°7 Mn 2452°6 8 473°55 i) +°73 2437°7 Mn 2438°2 8 8 476°55 iS) +78 2427-5 Mn 2428-0 6 7 481°75 ff + °73 2409°6 Mn 2409-4 1 1 493°50 ff +78 2373°0 Mn 2373°5 3 1 511°40 ff +°73 2320°2 Mn 2320°5 3 1 Morrow—Speetra of Manganese, Lead, Copper, and Lithium. 281 } Leap. The standard solution of lead chloride was prepared by dissolving 1-342 grammes of pure lead chloride in hot distilled water. One drop of strong hydrochloric acid had to be added in order to clear the solution, which was then diluted, before cooling, with distilled water, and when cold was made up accurately to 1 litre. ‘The quantity of this solution (0-1 cc.) which was then put into the vacuum tube contained therefore 0-0001 gramme of lead. As soon as the water had been driven off when the solution was being evaporated to dryness in the vacuum tube, the solid suddenly volatilized and condensed in the capillary portion of the tube, rendering it opaque ; but it did not remain so whilst the current was passing, so that the spectrum was obtained quite well, there being a bluish colour for about 30 seconds, which appeared again at intervals for about a second. When taking the third photograph of the lead spectrum, the colour in the tube was pink, probably mainly due to the presence of hydrogen. Many lines show in the first spectrum of lead, using 0:0001 grammes of the metal, and a broad band appears from ) 4068-2 to X 4058-0, which pro- bably consists of the lines \ 4068-2, \ 4062°3, and 4 4058-0. In the second photograph the band has disappeared, a strong line \ 40682 remains, which line appears again strongly in Plate XXIV., No. III, as one of the ultimate lines of lead. g F 3 2 as 3 I a 2 Persistency and Had ele oe S a Sa Intensity. gE fas Se Aig Element. ai = AS 3c : “2 io oS) Fslie a2 Se lara | 6° 28 ak Sand Vacuum = | = ay z o Fe = spare tube. 205°00 | Cd [4] 155°50 f Pb | 6687-3 10 3 158-10 iS) 6560°0 H 6563°0 20 | 10 160°35 | Cd [1] 6439°3 | 171°65 iS) 5888-0 Na 5893°2 10 10 174°78 ff 5608-0 Pb 5608°2 10 2 19440 | Ca [4] 194°35 | 5086-1 202°70 m —'08 4861-0 H 4861°5 20 7 204-95 | Cd [5] 204-98 | 4800-1 | 222°60 | mCad[7]| 222°52 | 4415-9 | | 223°95 iS) — 07 4389°8 Pb 4387°3 9 8 226°50 m — +03 4341°2 H 4340°7 15 6 282 Scientific Proceedings, Royal Dublin Society. 2 5 ee BE ar Element. an eee) eae “2 | see | a 23175 | § +-07 | 4244-8 Pb 4245-2 10 10 236°30 | m +15 4166-0 Pb 4167°2 5 242:40 | edge 4-23 | 4067-6 Pb 4068-2 6 10 8 Pb 4062°3 6 10 24315 | edge 4:25 | 4056-5 Pb 4058-0 | x10 ui 10 245-60 | m +30 | 4019-0 Pb 4019°7 8 6 247°05 br + *32 8997°2 N 3998°0 10 247-25 | Ca 247-57 | 3994-1 251-00 | be 4°31 | 3940-0 N 3942°5 10 261-25 | be 4°28 | 3804-2 N 3804°8 6 262°65 | +28 | 3786-4 Pb 3786-4 10 3 265°25 | m $27 | 37635 N 3755°1 6 26635 |S +27 | 3739°9 Pb 37401 | x 10 uz 8 27110 | 8 4-25 | 3683-5 Pb 36836 | x 10 11 10 27210 | 4:25 | 3671:8 Pb 3671°7 8 uw 8 274-85 |S 4-24 | 3640-3 Pb 3639°7 | x 10 wi 10 27750 | Ca[9] | 277-72 | 3611°8 280°70 | bs 4:22 | 3577-5 N 3576'S 10 28110 |S 4°23 | 3573-0 Pb 35729 | w 10 u2 10 284-60 | br 4:23 | 3587-1 N 3536°5 10 288-20 | £ 4°24 | 3500-0 N 3500°1 3 291-50 | Ca[10] | 291-75 | 3467-8 29810 | Cd[11] | 298-45 | 3403-7 301°75 | be 4°35 | 3871-0 N 33712 10 30300 | m 4°35 | 3360-1 e 6 31460 | m Od 4°36 | 3261-6 Cd 3261°2 8 6 315°70 316-06 | 3252-6 31595 |( 9 Et) | 516.35 | so50-5 319°80 | m +42 | 3219-9 Pb 3220-7 2 4 327-95 | m 4:46 | 3158-3 N 3158-9 6 33145 | Ca[13] | 331-95 | 31333 333°65 | m 4-49 | 3117-5 N 3116-4 5 337°65 | m +-47 | 3089°5 Pb 3089°2 6 5 341-40 | br +45 | 3064-0 H,0 | 30646 4 10 Morrow—Speetra of Manganese, Leud, Copper, and Lithium. 288 cae 2 g | Sra oi Persisteney and a lela S.S Qe Ss Ss Intensity. 2 Ee a a 3 SS Bre Element. Pin Sees sare a SE | Be | Be i] Be | 32 | go ||) oe s = S) = | = P tube. 354-25 | Cd[15] | 354:65 | 2980°8 354°95 f +°40 2976°5 N 2976-7 3 357-40 | f +-41 | 2960-8 N | 2961:9 | 3 358-85 | m +41 | 2952-0 N | 2953-0 4 371-20 8 Cd +47 2880°8 Ca 2880°9 372°60 iS) +747 287371 Pb 2873°4 x 10 uw 8 37925 | Ca[16] | 379-75 | 2837-0 379°95 iS) + °50 2833°3 Pb 2833°2 x 10 uw 8 381°80 S) + °49 2823°9 Pb 2823°3 gp 10 uw § 385°95 8 + °47 2802-2 Pb 2802°1 10 uz 10 393°50 m Cd + °45 2764:0 Cd 2764-0 396-60 Cd [17] 397-02 2748-7 41516 m + 42 2663°2 Pb 2663°2 x 10 ug 6 423-20 f + 41 2628°3 Pb 2628-4 2 3 426°55 Sy) + ‘41 2614°3 Pb 2614°3 x 10 uz 10 43°60 m + °40 2577°3 Pb 257773 o 8 uz 6 436°60 Cd [18] 437:00 2673°1 462°55 m + *40 2476°5 Pb 2476°5 8 uz 6 464-40 | Ca[20] | 464-80 | 2470-1 471°30 m + °40 2446°5 Pb 2446°3 6 uz 6 472°00 f + *40 2444-1 Pb 2443°9 6 uz 3 481-70 f +740 2411-9 Pb 2411°8 2 3 484°75 f + 40 2402°3 Pb 2402-0 2 3 487°30 m + °40 2394:0 Pb 2393°9 4 uz 6 507750 ff + *40 2382-2 Pb 2332°5 1 1 531°60 Cd [24] 532-00 2265°1 538°55 si + 742 2246°5 Pb 2247-0 1 2 559°40 Cd [25] 559-90 2194:7 CopPEr. The standard solution of copper chloride was prepared by dissolving 2'6570 grammes of copper chloride in distilled water and making the solution accurately up to 1 litre. The solid did not appear to volatilize very much when the current was 284 — Setentific Proceedings, Royal Dublin Society. passing in the tube, giving only a slight green luminescence. Afterwards there remained a beautiful red coloration on the quartz tube, where the copper had probably entered into combination with the silica. Whilst taking the second photograph there was a green fluorescence on the capillary portion of the tube for about 30 seconds at first. After some time a greenish blue colour appeared on the lower limb for a short time. This green fluorescence appeared again when taking the third photograph. The few lines which are seen on Plate XXIV., No. I, show the slight volatility of copper chloride. The second photograph gives only the ultimate lines of copper, A 32741 and X 3247°6, both of which appear faintly on No. III. : 4 aieGe a 34 4 Persistency and | I Ed ae & 2 3 ey 3 oy Teneo) eS5 | 28s 32 a | Element. iad Ad-ls | rE z Be 2 e 4 e Sook Vacuum = = © Ae = a tube. 205°00 | Ca [5] 15815 | m 6560-0 H 6563-0 20 4 160-40 | Ca [1] 6439-3 19450 | Cd [4] 194°35 5086°1 202:70 | f —-01 4857°2 H 4861°5 3 20495 | Cd [5] 204:97 4800-1 210:10 | 8 Ca +°02 | 4678-9 Cd 4678°4 10 10 29250 | Cd [7] 922-52 4415°9 226°50 | m + :03 4339°8 H 4340°7 5- 298-20 | Cdpil] 298-45 34087 301°80 | br 4-25 3371°3 N 3371°2 10 305-70 | m 4 +25 3337°9 Cu 3837°9 2 5- 309°10 | m + 25 3308°9 Cu 3308-1 x 6 311:90 | m $25 || 3985-2 Ni 3284°8 8 313-20 |S + +25 3274°3 Cu 3274°1 v8 ui 10 31410 | m 4°25 3266°8 N 3267°5 +8 315°80 |) Cafi2] | 316-06 3252°6 316710 | J 316-35 3250°5 31650 | 8 4:25 3247-2 Cu 3247°6 w 10 ui 10 328-05 | be + +94 3159-3 N 3158°9 10 | 381-30 | br 423 | 3136-2 N | 3135-7. 10 3387°80 m + °22 8090°2 ? : 341:00 | br + -21 3068-3 H20 3067-2 5 10 Morrow—Spectra of Manganese, Lead, Copper, and Lithium. 285 ~~ na : : ae | 24 EP a coo) eae ie 2a 3S S| Element. a 4 2 43 = “s BS s 5 | s e fe Vacuum si =) = 5 nts > > Spark. manee 341°60 | bv +21 3064-3 HO 3064:6 4 10 35445 | Cd [15] 354°65 2980°8 | 355-20 | br +21 2975:9 N 2976:7 10 357°60 | br 4 +29 2960°7 Cu 2961-2 » 5 10 359°00 | S$ + 28 2952-0 N | 2953-0 10 371-40 | Ca + -26 2880°8 Cd 2880-9 379-45 | Ca [16] 379-75 2837-0 | 383°80 | f + -26 28145 | 2 384-30 | br 4:25 | 28120 | HO | 2811-2 4 4 39685 | Cd [17] 397-00 2748-7 436-85 | Cd[18] 437-00 2573-1 458:50 | ff 4°15 9491:8 | Cu 2492-2 > 6 1 Liruium. The standard solution of lithium chloride was made by dissolving 5°279 grammes of pure lithium carbonate in hydrochloric acid, and diluting to 1 litre with distilled water. When passing the current for the first time, there was a strong yellow coloration in the tube until nitrogen leaked in through the mercury trap, which gave the usual mauve tint. Whilst taking the second photograph there was a persistent yellow colour in the tube, which had almost disappeared when taking the third photograph. Not many lines of lithium appear on any of the photographs, as it is evidently not very volatile, but the ultimate lines are \ 6708'2 and X 4602°4, which are seen on Plate XXIV., No. Il. In No. III there is an exceedingly faint indication of A 6708-2 on the original plate. The sodium lines \ 5890:2 and X 5896:2 appear as one line on all three photographs, showing the greater volatility of sodium than of lithium. SCIENT. PROC. R.D.S., VOL. XIII., NO. XXII. 2x 286 Scientific Proceedings, Royal Dublin Society. 3 a E Ee 36 en Element. ae = Se | so ee Se | Seis | aie 205-00 | Cd [5] 155-45 |S Li 6708-2 10 uy 10 158:05 | 8 6560-0 H 6563-0 20 9 160-40 | Ca [1] 6439°3 167°10 | m 6050-0 Li 6103'S | 10 6 171-55 |S 5880:0 Na 5893°2 10 10 194°35 | Cd [4] 194°35 | 5086-1 20275 | m 4858-0 H 4861°5 20 7 205-00 | Cd [5] 204-98 | 4800-1 213-70 |S —-07 | 4599-4 Li 4602-4 10 ur 8 222-65 | Cd [7] 222-53 | 4415-9 226-65 |S —-ll | 4339-5 H 4340-7 8 238-15 | in —-08 | 4139-0 N 4141°2 10 238°65 | m --08 | 4130-6 li 4132-6 6 10 240-50 | f - -08 | 4100-7 H 4101°8 2 241-05 | £ —-07 | 4093-2 N 4094-0 10 251-20 | bt —-05 | 39425 N 3942-5 10 253:20 | m —"04 | 3614-7 Li 3915-2 5 254-60 | m —-04 | 3895-2 N 3894-2 10 277-70 | Ca [9] 277-72 | 3611-8 298-40 | Cd[11] | 298-48 | 3403-7 301-80 | br +07. | 3373-0 N 3571°2 10 305:80 | m +°05 | 3338-6 N 3338-6 10 309°30 | br +03 | 3309-0 N 3309°4 10 509-90 |S +-03 | 3303-9 Na 3302°8 10 10 812°15 | br +702 | 3285-2 N 3284°8 10 314-30 | m +01 | 3267-0 N 3267°5 10 316-00 | Cd ) [12] 316-05 | 32526 316-35 | Ca 316°35 | 3250-5 31855 | m +00 | 3233-0 Li 3232°8 5 6 328°30 | br --04 | 3159-4 N 3158°9 10 331:55 | br 05 | 3136-5 N 3135-7 10 334-20 | m ~-05 | 3117-4 N 3116-4 8 341-03 | br --07 | 3068-0 H20 | 3067-2 5 10 Morrow—Spectra of Manganese, Lead, Copper, and Lithium. 287 5 fe 2 A 3 32 | ae Persistency and zed SoA 2 Sa | | 25 Intensity. See) ean 35 a Element. a 3 Gp 333 Lo aD So I le = UE Be. = ake Vacuum a ie s os Ne | =e Spank Tube. 841°75 bY — 07 5065°2 H20 | 3064°6 4 10 354-715) (Cau lei i) 854265 2980-8 | 359°50 br — 10 2976-0 N 2976-7 10 359-50 br = ll 2951-2 N 2953-0 10 371°80 Ca 371-65 2880°8 379°85 Cd [16] 379°75 2837:0 383-30 it -— 12 2819°7 N 2819°7 2 884°35 f — 18 2813'S N | 2814-1 2 397-40 | Ca[17] | 397-02 | 2748-7 398-90 ff — +38 2741°3 Li 2741-4 5 1 43760 | Cd [18] 437-00 2573°1 (Sie J. bo cr 10. 11. 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearine Irish Pteridosperm, Crossotheca Héninghiusi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, D.sc., F.L.Ss. (Plates I-III.) (March, 1911.) Is. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Georce H. Pernysriper, B.S¢., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wituram Brown, B.sc. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy By Henry H. Dixon, so.p., F.R.s. (April 20, 1911). 1s. . A Method of Hxact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrt1am J. Lyons, 8.a., a.R.c.sc. (LonD.). (May 16,1911). 6d. . Radiant Matter. By Joan Jouy, sc.p., F.R.s. (June 9, 1911.) Is. . The Inheritance of Milk-Yield in Cattle. By James Wixson, m.A., B.Sc. {June 12, 1911.) 1s. . Is Archzopteris a Pteridosperm? By T. Jonson, p.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) Is. 6d. . The Occurrence of Arch@opteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jonson, D.sc.,F.u.s. (Plates VIL, VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Prorzssor Joan JoLy, M.A., S0.D., F.R.S. (July, 1911.) 6d. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. ‘By Joun Jouy, sc.p., F.x.S., and Lours B. Smyru, B.a. (Plate IX.) (August, 1911.) 1s. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newent Arper, M.A, F.LS., F.G.S. (January, OTS) ells 13. 14. 15. 16. 18. NG), 20. 21. 22. SCIENTIFIC PROCEEDINGS— continued. Frovbesia cancellata, gen. et sp. nov. (Sphenopteris, sp., Baily). By 'l'. Jonnson, D.sc., F.u.s. (Plates XIII. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Winson, ™.a., B.Sc. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part 1.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Pounox, p.sc. (Plates XV. and XVI.) (February 21, 1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, se.p., .z.s., and W.R. G. Arxins, m.A. (February 21,1912.) 6d. . Improvements in Equatorial Telescope Mountings. By Sir Howarp Gruss, r.r.s. (Plates XVII-XIX.) (March 26,1912.) 1s. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Dixon, sc.p., F.z.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Dixon, sc.p., F.z.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from Jounty Cork. By 'T. Jounson, p.sc., r.u.s. (Plates XX. and XXI.) (April 12, 1912.) Is. On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part IJ.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By James H. Potnox, D.Sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s. The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Coprer, and Lithium. By Genevieve V. Morrow, A.R.C.Sc.1. (Plate XXIY.) (May 11, 1912.) 1s. DUBLIN: PRINTED AT CHR UNIVERSUCY PRESS BY PONSONKY AMD GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 23. MAY, 1912. AWARD OF THE BOYLE MEDAL SIR HOWARD GRUBB, F.RS. APRIL 16, 1912. DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. Price Sixpence. Roval Dublin Society. a aaa ~ FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tux Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be get down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready ior transmission of the Kditor. Morrow—Spectra of Manganese, Lead, Copper, and Lithium. 257 ~ a : : J4|2 4) ge | 33 ap | “Sade g eid q a3 ec a Element. eS Ae 3 3 Be Se a3 ease Vacuum r->| iz 2) al = ne Tube. 341°75 by — 07 3065°2 H20 3064°6 4 10 354°75 Cd [16] 354°65 2980°8 355°50 br — 10 2976°0 N 2976°7 i0 359°50 br --ll 2951-2 N 2953-0 10 371-80 Ca 371-65 2880°8 379°85 | Cd[16] | 379-75 | 2837-0 383°30 f — 12 2819°7 N 2819°7 2 384°35 f — 13 2813°8 N 2814°1 2 397-40 | Ca[i7] | 397-02 | 2748-7 398-90 ff — +38 2741°3 Li 2741-4 5 1 437°60 Cd [18] 437-00 2573°1 SCIENT. PROC. R.D.S., VOL. XII., NO. XXII. Q2y ; 28 7 XXII. AWARD OF THE BOYLE MEDAL TO SIR HOWARD GRUBB, F.R.S., 1912. In recommending the award of the Boyle Medal to Sir Howard Grubb, it is necessary to explain why it is that the proposal is only now submitted to the Council. When the Medal was instituted in the year 1896, it was thought desirable that no honorary officer of the Society should be eligible for the award ; accordingly a rule to that effect was adopted, and remained in force until, at the suggestion of this Committee, the Council repealed it in December, 1911. Sir Howard Grubb has been an honorary officer of the Society since the year 1889; hence it is that itis only now in the power of the Society to mark its appreciation of merit which would otherwise have been recognized long ago. Sir Howard Grubb’s first communication to the Royal Dublin Society was received on November 15th, 1869, and his most recent communication was received on November 8th, 1911. His contributions to the scientific publications of the Society have therefore already extended to a period of forty-two years. Many of Sir Howard Grubb’s communications take the form of suggested improvements in the construction and mounting of telescopes and other optical instruments. It is, however, in the actual construction of the instruments that Sir Howard Grubb’s work demands the most marked recognition the Society can bestow. The Melbourne telescope, which is described in the Journal of the Royal Dublin Society for 1869, was the first large reflector to be mounted equatorially, and thus prepared the way for the great equatorial reflectors of more recent years, which have been employed with conspicuous success in celestial photography, and have greatly increased our knowledge of the nebula. The great refractor erected for the Austrian Government in Vienna in 1878 exceeded mee one inch the aperture of the largest telescope then in- 1 The presentation was made at the Scientific Meeting of the Royal Dublin Society held on the 16th April, 1912, when the medal was handed to Sir Howard Grubb by the chairman (Professor John Joly, D.sc., pee Award of the Boyle Medal to Sir Howard Grubb. 289 existence—the Washington refractor. In this instrument, not onl were the optical parts of the highest excellence, but the mounting marked a new departure, and placed in the hands of the astronomer facilities he did not previously possess. ‘The anti-friction arrangements of the bearings were of a most ingenious type, especially in their application to the declination axis, in which they were successfully carried out in this instrument for the first time. The first instruments in which declination was read from the eye-end of the telescope seem to be the 15-inch equatorial by Grubb, and the 6-inch instrument by Cooke erected for Lord Crawford at Dun Echt, Aberdeen, about 1873. The plan is now universally adopted. It was, however, reserved for Sir Howard Grubb to accomplish the feat of enabling the observer to read the right ascension circle from the eye-end also, and this he succeeded in doing for the first time in the great Vienna telescope. Another interesting feature is the electrical control of the clockwork for driving the telescope in right ascension. This ingenious device ensured uniformity of motion under normal conditions, and also afforded a means of correcting any error which might accidentally arise. The slow motion in right ascension consists of a set of differential wheels, which increase or diminish the rate at which the telescope is driven, without interfering with the rate of the clock or exciting any oscillatory motion in the telescope. It is needless to dwell upon the influence that accuracy of control has had upon stellar photography; without it the wonderful developments of recent years would not have been possible. Several of the telescopes employed in the formation of the great astrographic chart of the heavens (notably those at Greenwich, Oxford, and the Cape) were constructed by Sir Howard Grubb and fitted with his clock control. The 26-inch refractor which Sir Howard Grubb constructed for the Royal Observatory, Greenwich, exhibits these refinements in a more elaborate form. It is not necessary to mention in detail the many famous instruments Sir Howard Grubb has constructed. Suffice it to say that they are to be found in observatories in Germany, Austria, Russia, Belgium, Italy, Spain, Turkey, America, the British Colonies, India, China, as well as in many places in the United Kingdom. Sir Howard Grubb’s attention has been by no means confined to telescopes and their mountings. Nearly forty years ago he was Chairman of the Committee of Science when it was decided to institute a system of electrical control of the clocks of Dublin. A Report, published as an Appendix to the Minutes of the Council (Proceedings, vol. cx), shows that at that time no public clock in Dublin showed the true time, the error in 2x2 290 Scientific Proceedings, Royal Dublin Society. some of them amounting to several minutes. Sir Howard Grubb was the principal worker in the reform which the Society instituted. On the introduc- tion of the telephone, with its innumerable overhead wires, which were constantly breaking and short-circuiting the clock-wires, the system was restricted to Leinster House, Trinity College, and the Port and Docks Board, where it is still in operation. In the year 1900 Sir Howard Grubb patented an entirely new form of gun-sight, and he subsequently devised the improved form of periscope— the instrument used for seeing above water from the hull of a submerged sub-marine. ‘This instrument is now used in the Royal Navy. Among other instruments which he has improved or invented may be mentioned the micrometer, stereoscope, heliostat, depleidoscope, cireum- ferentor, and various geodetic instruments. It is not alone in his own particular line that Sir Howard Grubb has done work which has made his name known in every country in the civilized world, and shed lustre upon his country. He has for an unusually long period taken an active part in the entire work of the Royal Dublin Society— which alone merits the Society’s highest approbation. We append a list of Sir Howard Grubb’s chief contributions to the scientific publications of the Royal Dublin Society and other bodies. List or PuBLications. . On a Recently Observed Meteor. Journal Royal Dublin Society. 1869. . On the Great Melbourne Telescope. Journal Royal Dublin Society. 1869. . On Clocks for Equatorial Telescopes. Journal Royal Dublin Society. 1873. . On the Testing of Large Objectives. British Association Report. 1876. 5. On a Method of Photographing the Defects in Optical Glass arising from want of Homogeneity. British Association Report. 1876. 6. On Babbage’s System of Mechanical Notation as applied to Automatic Machinery. Scient. Proc. Royal Dublin Society. 1877. 7. On Great Telescopes of the Future. Scient. Trans. Royal Dublin Society, 1877. 8. On a New Form of Electrical Contact-maker for Astronomical and other Clocks. Scient. Proc. Royal Dublin Society. 1878. 9. Improvements in the Stereoscope. Scient. Proc. Royal Dublin Society. 1879. 10. On the Equatorial Telescope, and on the New Observatory of the Queen’s College, Cork. Scient. Proc. Royal Dublin Society. 1879. -m © BO Award of the Boyle Medal to Sir Howard Grubb. 291 11. With Cuas. E. Burton.—On a New Form of Ghost Micrometer for Use with Astronomical Telescopes. Scient. Proc. Royal Dublin Society. 1880. 12. Note on the Effect of Flexure on the Performance of Telescopic Objectives. Scient. Proc. Royal Dublin Society. 18838. 13. On a New Form of Equatorial Telescope. Scient. Trans. Royal Dublin Society. 1884. 14. Notes on some Points in the Construction of Turret Clocks. Scient. Proc. Royal Dublin Society. 1885. 15. Note on some Improvements in Equatorial Telescope Mountings. Scient. Proc. Royal Dublin Society. 1886. 16. Note on a Graphical Method of Solving certain Optical Problems. Scient. Proc. Royal Dublin Society. 1887. 17. The Construction of Telescopic Object-Glasses for the International Photographic Survey of the Heavens. Scient. Trans. Royal Dublin Society. 1890. 18, On a Heliostat for the Smithsonian Institution, Washington. Scient. Proc. Royal Dublin Society. 1890. 19. Revolving Machinery for the Domes of Astronomical Observatories. Scient. Proc. Royal Dublin Society. 1891. 20. On an Improved Equatorial Telescope. Scient. Proc. Royal Dublin Society. 1892. 21. On a New Form of Equatorial Mounting for Monster Reflecting Telescopes. Scient. Proc. Royal Dublin Society. 1894. 22. Notes on a Paper recently published in the Astrophysical Journal (vol. v., No. 2, February, 1897), by Professor EH. Haun, of the Yerkes Observatory, Chicago, on ‘The Comparative Values of Refracting and Reflecting Telescopes for Astrophysical Observations.”” Scient. Proc. Royal Dublin Society. 1897. 23. Note on the Results that may be expected from the proposed Monster Telescope of the Paris Exhibition of 1900. Scient. Proc. Royal Dublin Socicty. 1899. 24. On the Correction of Errors in the Distribution of Time Signals, Scient. Proc. Royal Dublin Society. 1899. 25. Proposal for the Utilization of the ‘‘ Marconi” System of Wireless Telegraphy for the Control of Public and other Clocks. Scient. Proc. Royal Dublin Society. 1899. 26. A New Collimating Telescope Gun-sight for Large and Small Ordnance. Scient. Trans. Royal Dublin Society. 1901. 27. Some New Forms of Geodetical Instruments. Scient. Trans. Royal Dublin Society. 1902. 28. Registration of Star-Transits by Photography. Scient. Proc. Royal Dublin Society. 1904. 292 Scientific Proceedings, Royal Dublin Soevety. 29. A New Form of Dipleidoscope. Scient. Proc. Royal Dublin Society. 1904. 30. A New Form of Position-Finder for Adaptation to Ships’ Compasses. Scient. Proc. Royal Dublin Society. 1904. 31. A Circumferentor. Scient. Proc. Royal Dublin Society. 1904. 32. Floating Refracting Telescopes. Scient. Proc. Royal Dublin Society. 1904. 33. A Modified Form of Electrical Control for Driving Clocks. Scient. Proc. Royal Dublin Society. 1905. 34. A New Form of Right-Ascension Slow Motion for Equatorial Telescopes, Illustrated by the Driving-Gear of the Cape Town Equatorial. Scient. Proc. Royal Dublin Society. 1905. 35. Improvements in Equatorial Telescope Mountings. Scient. Proc. Royal Dublin Society. 1911. The foregoing Report and recommendation of the Committee of Science and its Industrial Applications were adopted by the Council on the 21st of March, 1912. 1. 10. 11. 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Irish Pteridosperm, Crossotheca Hoéninghwusi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, D.s¢., F.L.s. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on tae supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Groner H. Peraysrwen, B.sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wiiu1am Brown, 8,so. (April 15, 1911). 1s. . A Thermo-Electric Methed of Cryoscopy By Henry H. Dixon, so.p., F.r.s. (April 20, 1911). Is. . A Method of Exact Determination of the Contimuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wittram J. Lyons, B.a., A.R.c.sc, (LonD.). (May 16,1911). 6d. . Radiant Matter. By Joan Jony, sc.p., r.x.s. (June 9, 1911.) Is. . The Inheritance of Milk-Yield in} Cattle. By Jamms Wuuson, M.a., B.so. (June 12,1911.) 1s. . Is Archzopteris a Pteridosperm? By T. Jounson, D.so., F.L.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archxopteris in Ireland. By T..Jounson, p.sc.,F.u.s. (Plates VII., VIII.) (June 28, 1911.) Is. Award of the Boyle Medal to Proressor Jon JoLy, m.a., so.D., F.R.3. (July, 1911.) Gd. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. ‘By Joun Joby, sc.D., F.k.s., and Louis B. Smyru, B.a. (Plate IX.) (August, 1911.) 1s. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newstn ARBER, M.A, F.LS., F.G.s. (January, 1912.) 1s 138. 14, 15. 16. 17. 18. 19. 20. 21. 22. 23. SCIENTIFIC PROCEEDING S— continued. Forbesia cancellata, ger. et sp. nov. (Sphenopteris, sp., Baily). By T. Jounson, D.sc., F.L.S. (Plates XIII. and XIV.) (January, 1912.) 1s. The Inheritance of the Dun Coat-Colour in Horses. By James WInson, M.A., B.SC. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Ponuox, p.so. (Plates XV. and XVI.) (February 21,1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Hmnry H. Dixon, sc.p., ¥.n.s., and W.R. G. Arxins, ma. (February 21,1912.) 6d. Improvements in Equatorial Telescope Mountings. By Sir Howarp Gruss, F.k.s. (Plates XVIL-XIX.) (March 26, 1912.) 1s. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Dixon, sc.p., r.n.s., and W. R. G. Arxins, ma., atc. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Dixon, sc.d., F.n.s., and W. R. G. Arxins, w.a., ao. (April 9, 1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jounson, p.sc., rus. (Plates XX. and XXI.) (April 12, 1912.) 1s. On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part {I.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By James H. Potnox, D.Sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s. The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Copper, and Lithium. By Gznrvinve V. Morrow, A.R.C.Sc.1. (Plate XXIV.) (May 11, 1912.) 1s. Award of the Boyle Medal to Sm Howarp Gruss, F-.8.S., April 16, 1912. (May 18, 1912.) 6d. DUBLIN: PRINTED AT CHE UNIVERSITY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 24. SEPTEMBER, 1912. NOTES ON DISCHIDIA RAFFLESIANA, Wat.., anp DISCHIDLA NUMMULARLA, Br. BY A. F. G. KERR, M.D. [COMMUNICATED BY PROFESSOR H. H. DIXON, SC.D., F.RB.S.] (PLATES XXV.—XXXI.) ahs alan Insti . ANS loa het “ey, DEC 311912 ) [Authors alone are responsible for all opinions expressed in thir Communications. | 7A WS, Rienal Musew DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. Price Two Shillings. Roval Bublin Society. Oe FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tue Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the [ditor. f 28 J XXIV. NOTES ON DISCHIDIA RAFFLESTANA, Watt. anv DISCHIDIA NUMMULARTA, Br, By A. F. G. KERR, M.D. [COMMUNICATED BY PROFESSOR H. H. DIXON, SC.D., F.R,S, | [Read Mancn 26. Published Serremper 30, 1912,] (Pratrs XXV.-XXXI,) Habit and General Morphology. Dischidia rafilesiana, Wall., and Dischidia nummularia, Br., are common epiphytes in the dry, deciduous jungles of Northern Siam, particularly in “Ene” jungle. Dischidia raflesiana is most commonly found on Dipterocarpus tuberculatus, Roxb., the predominant tree of this jungle, but by no means exclusively so; Shorea obtusa. Wall., Pentacme siamensis, Kurz, Melanorrhea usitata, Wall., Eugenia fruticosa, Roxb., Bridelia retusa, Spreng., and other deciduous trees also act as hosts. Dischidia nummularia is found on nearly all the trees of this jungle; it also extends into jungles containing both deciduous and evergreen trees. In accordance with their mode of life, both these epiphytes show decided xerophilous characters. D. nummularia has fleshy, orbicular, yellowish-green leaves, 1 to 1:4 em. in diameter; they are biconvex, though, as a rule, somewhat flatter on the lower surface, which lies on the bark of the host. The epidermis has a thick, waxy cuticule. The plant is attached to the host by adventitious roots arising from the ventral surface of the stem, a pair springiug from each node close to the insertions of the petioles. Once I observed an additional root from the dorsal surface of a node, comparable to the pitcher roots of D. raflesiana, to be described later. ‘The roots serve as organs both of attachment and absorption, Adventitious roots appear at a very early stage in the life-history of the plant; with the expansion of the cotyledons the primary root ceases to develop and begins to wither, while adventitious roots are developed from the swollen lower portion of the hypocotyl. When a plant grows in a shady sitnation, the leaves are thin, flat, more elliptical in shape, less thickly coated with wax, and of a more decidedly SCIENT. PROG. R.D.S., VOL. XIII., NO. XXiy, 22 294 Scientific Proceedings, Royal Dublin Society. green colour, like the young leaves of the ordinary form. A single plant of D. nummularia often covers an area of several square feet, completely covering that part of the trunk or branch on which it grows. D. rafiesiana is heterophyllous, having three well-marked forms of leaf (though one of these is confined to the young plant), and is also heterorhizal. The early stages of germination are identical with those of D. nummularia; and the first foliage leaves are very similar to and often indistinguishable from those of that plant. Usually three to five pairs of these leaves are produced; they may also be borne by the first lateral branches; sooner or later, however, the pitcher-leaves appear, either on a continuation of the main axis, or on a lateral branch. Intermediate forms of leaf are not uncommonly, though not always, found between the first foliage and the pitcher-leaves. These intermediate forms have their upper surface very convex, and the lower correspondingly concave, the tip being slightly inturned ; more rarely there is a series of leaves in which the convexity increases and the mouth narrows until the typical pitcher form is reached. The pitcher-leaf is formed by the more rapid growth of the central part of the lamina, so that a bag-form is produced, the outside corresponding to the upper surface of the leaf and the inside to the lower. The mature pitcher reaches a length of about 12 cm.; it is of a light yellowish green colour externally, and of a deep purple colour within. The small entrance, or mouth of the pitcher, is bounded on one side by the short, stout petiole, on the other by the inturned edge of the leaf. ‘The spout-like, inturned tip of the leaf forms a short passage from the mouth into the pitcher. ‘This passage will barely admit the entrance of a small goose-quill. ‘The mouth of the pitcher is normally turned towards and pressed against the supporting branch. Asin D. nwnmularia, a pair of adventitious roots spring from the ventral surface of each node, close to the insertion of the petioles; in addition to these, the pitcher-bearing branches have other roots—pitcher-roots—which arise in pairs from the dorsal surface of the nodes. Each root makes its: appearance from the stem very close to the petiole, and then grows along the petiole into the interior of the pitcher, where it branches freely. Rarely, in the plants examined by me, does the pitcher-root appear to arise from thie petiole; in such cases, by pulling gently on the root, it tears through the superficial tissues of the petiole; and its real origin from the stem is readily seen. Scott and Sargant agree with Treub in describing the origin of the pitcher-root from the petiole as the normal one.’ No doubt plants from 1Scott and Sargant onthe Pitchers of Dischidia vaffesiana (Wall.), “‘ Annals of Botany,”’ yol. vii, No. xxyi, 1893, Kerr—Dischidia rafilesiana and Dischidia nummularia. 290 different localities vary in this respect as they doin others. or instance, Scott and Sargant have noted differences in the structure of the root, and the proportion of stomata on the inner and outer surface of the pitcher, in plants from Burma and Java.’ Occasionally young plants with only tlat leaves have dorsal roots, in which case these roots grow towards the support, and, like the ventral, act as attaching-roots. Twenty or more closely crowded pitchers may be produced on one branch; but at some time or another from this branch spring one or several twining shoots which climb with a sinistral twist up the branches of the host-tree. ‘These twining shoots, which have very long internodes, bear the third form of leaf—the ordinary foliage leaf—which is considerably larger and thinner than the leaves of the seedling ; it is very caducous. The twining shoots have adventitious roots at the nodes, and frequently also scattered along the internodes. The lateral branches of these shoots bear pitchers. Hventually it may happen that most of the branches on a large tree carry one or more groups of pitchers of the epiphyte, all the groups being connected by the now leafless twining shoots. he pitchers,-as I have already mentioned, have their base, with the entrance to the interior, turned towards the support, and pressed close against it. According to their position on the branch, the pitchers may have any direction, from pointing straight downwards to pointing straight upwards ; in the former case it is hardly correct to describe them as pendulous—a term which conveys the idea of hanging loosely and swinging; whereas they are always—in the first instance at least—firmly fixed. Sometimes a group of pitchers, owing to the weight of their contents, may become partially detached from a branch. It has been noted that D. rajlesiana prefers to live on decaying trees, and certainly it is frequently to be seen ou dead branches; but dead branches are common on Dipterocarpus tuberculatus, whether this tree is the host of a Dischidia or not. After examining a number of trees, I came to the conclusion that, on the whole, dead branches were more frequent on those trees which carried either D. ruflesiana or D. nwmmularia. The histology of the vegetative orgaus of D. raflesianu is considered very fully in papers by Scott and Sargant’, and Groom’, aud need not be gone into here. ‘Ihe tissues of the leaf of D. nuwmmularia resemble those of the foliage leaf of D. rafflesiana ; the greater part of the leaf is composed of thin- walled water-tissue cells; there is no palisade parenchyma, the tissues of the upper and lower surface being similar. In the ordinary form of the leaf the ' Scott and Sargant, doc. cit. + Groom on Dischidia rafflesiana (Wall.), ‘‘ Annals of Botany,” vol. yii, No. xyi, 1893. 222 296 Scientifie Proceedings, Royal Dublin Society. number of stomata on the upper and lower surface is practically the same ; but in the shade form they are about four times more numerous on the lower surface. In both forms water-pores occur on the upper surface. Relations with Ants. Both of the species of Dischidia under consideration harbour ants. They are not unique in this respect, as ants have been noticed in connexion with several other species of this genus. In D. nummularia the ants are found beneath the leaves, where they form nests of clay and vegetable debris, in which the roots of the Dischidia branch freely. The ants also make. passages, covered in with the same material as that of the nest, which run in the crevices of the bark down the trunk to the ground, and along many of the branches to their leafy extremities. I was able, through the kind offices of the authorities of the British Museum, to obtain identification of these and other ants from Dr. Forel. They proved to belong to two species of Iridomyrmex—Z. myrmecodie, Emery, and a new variety, Waldoi, Forel, of J. cordatus, Smith. Sometimes a small black ant, Cataudacus granulatus, Latr., sub-sp. Aispidus, Smith, was found wandering about plants of D. nwmmularia, but always in small numbers, and apparently in perfect agreement with Iridomyrmex. In May, June, and July of 1911, I examined eighty-one plants of D. nummularia growing naturally, taking them consecutively, except that I only counted one plant on each tree, and did not count any plant which was on the same treeas D. raflesiana. lvidomyrmex was found nesting under the leaves of seventy-seven of the eighty-one plants examined. In three of the four plants where Iridomyrmex was not found their deserted nests were present under the leaves, and their runs on the trunk of the host-tree. In two of these three cases other ants were present in large numbers on the tree—Dolichoderus bituberculatus, Mayr, in one, Gicophylla smaragdina, Fabr., in the other. ‘They had possibly driven away the Iridomyrmex. ‘The fourth plant was in a dying condition; there were termite runs about the tree and under the dying plant. Of the eighty-one plants examined, therefore, eighty either had a species of Iridomyrmex actually living under their leaves, or there was evidence of its recent presence, the only plant with no sign of Iridomyrmex being ina dying condition. I think, then, we may conclude that, as far as Northern Siam is concerned, Dischidia nummularia normally harbours one of the above species of Iridomyrmex. These two species of Iridomyrmex appear very similar to one who is not an entomologist ; and it was not until I had sent to London Kirr—Dischidiu rafilesiana and Dischidia nummularia. 297 several batches from different plants that I discovered two species were involved. In D. rafilesiana the ants make their nests within the pitchers, and also plaster clay about the bases of the pitchers, and over the attaching roots. I was not able to examine such a large series of this species, as it was not quite so abundant as D. nwnmularia, and is usually more inaccessible, growing near the tops of large trees. I followed the same procedure as for D. nummularia, only counting one plant on each tree, and omitting any plant growing on the same tree as D. nwmmularia. In all, forty-five plants were examined, and in forty-four of these the nests of the sametwo species of Iridomyrmex were found in one or more of the pitchers of each plant. The single exception was a young plant with only one small pitcher. No runs were seen near it or on the same tree. hese facts warrant us in drawing the same conclusion with regard to D. raflesiana, i.e. that in Northern Siam it is usually associated with a species of Iridomyrmex. Structure of Flowers and Pollination. In both D. raflestana and D. nwnumularia the flowers are borne in shortly stalked umbels in the axils of the leaves, of either the foliage or pitcher leaves in the case of D. raflesiana. In both species only one or two flowers in each umbel open at a time. The flowers of D. vaflesiana are about 0°7 cm. long; they are of a greenish colour, with brown longitudinal lines from about one-third of the way up the corolla to its tip. ‘These lines mark the adjoining edges of the petals; the petals are free for somewhat less than one-third the length of the corolla, but remain in close apposition. When the flower opens, the tips of the petals separate slightly, not sufficiently to admit the passage of an ordinary pin; this entrance is protected within by a circle of stiff, inwardly pointing hairs. From the base of the staminal column spring five bicornuate appendages, the adjacent horns of which meet and form a circle round, but at some distance from the column at the level of the clips. The edges of the anthers are produced into wings narrow above but broadening out below; the edges of the wings of adjoining anthers meeting for the greater part of their length form a long, narrow chamber; in the lower part of this chamber, however, the boundary is formed by the thickened median portions of the wings, the edges of the wings being here turned outwards to form a short furrow. ‘The ovary and the greater part of the style are surrounded by the staminal column. The style is expanded in the middle and again, to a lesser extent, at its free 298 Scientifie Proceedings, Royal Dublin Society. extremity, where it projects beyond the anthers. The median expansion bears five ridges which lie at the bottom of the chambers formed by the anther wings. ‘The ridges are covered with high columnar glandulat cells whose function is the secretion of nectar; they also secrete the clip, which is found lying on them at the upper part of the ridge, and probably the bands connecting the clip with the pollinia. he clip is a horny plate whose inturned edges form a furrow narrowing upwards, the lower end of the furrow being continuous with the slit between adjoining anther wings ; from near its upper end on either side a horny band is given off which embraces the lower end of the pollinium on the corresponding side. ‘The stigmatic surface of the style ison the under surface of the median expansion, below the nectar ridges. The staminal appendages have no nectar tissue. In these flowers, then, the nectar-secreting spots are not on the same radii as the stamens, and we would, following Knuth, expect to find that the clips clasp the proboscis of the pollinating insect, not the legs as in Asclepias. This is doubtless the case. The insect visitor reaches the nectar ridges by inserting its proboscis into the slit between two anther wings. This it will most readily do at the lower end of the slit where the edges of the wings turn out a little. In withdrawing its proboscis, it will draw it-along the slit into the clip where it will become firmly wedged; and in withdrawing it further the clip and bands with attached pollinia must come too; now in visiting another flower the pollinia may be introduced into the slit and left there, though I have not observed this. In two cases, however, I found the pollinia lying at the base of the flowers, from which position their pollen-tubes had made their way up through the lower part of the slit to the stigmatic chamber (see Plate XXYV., fig. 5). Possibly the chief function of the staminal appendages is to scrape the pollinia off the proboscis of the visiting insect. This would explain their curious shape. The secretion of nectar is very abundant, so much go that when the flower opens a drop of nectar is extruded from the tip of the corolla. This nectar is greedily taken by the Iridomyrmex living in the pitchers, and also by another ant, Polyrachis acantha, Sm., var. Kerrii, Forel, though the Irido- myrmex often drives the Polyrachis, a much larger ant, away from the flowers. I have had very few opportunities of observing the flowers of D. rafiesiana, and the above ants are the only visitors to the flowers I have seen. It is, however, a physical impossibility for either of them to effect pollina- tion, as they have no means of reaching the column. Occasionally flowers are found with a hole at the base of the corolla, evidently made by some insect in search of nectar; but I have not noticed, that such flowers were fertilized, whereas it is not uncommon to find fertilized flowers with intact Kurr—Dischidia rafilesiana and Dischidia nummularia. 299 corollas, It is highly probable that pollination in this species is effected by a bee, as is the case in D. nummularia. D. nummularia has white flowers somewhat smaller than those of D. rafflesiana; when the flowers open, the tips of the petals turn back, affording a relatively large entrance to the interior of the corolla; the structure of the staminal column and style is similar to that of D. rafflesiana. The flowers are freely visited by the Iridomyrmex living beneath the leaves and by other ants, which, in this case, can readily enter the corolla. The circle of hairs at the entrance seems to be no obstacle even to very minute ants; but I have never seen an ant removing pollinia. ‘Ihe flowers are also visited by two small bees ; one of these, Allodape, sp., is found at the flowers about mid-day : of five bees caught on the flowers not one carried pollinia ; the other species, Nomia, sp., appears from about 7 a.m. to 8 a.m. The only two of this bee I was able to catch both had pollinia attached to their proboscides. The Nomia is probably the chief pollinator of these flowers. Possibly an examination of a larger series of the Allodape would have shown some with pollinia, Dispersal of Seeds. The seeds, like those of other Asclepiadacez, have a well-developed coma of silky hairs, and appear well adapted for dispersal by wind; but there is evidence to show that they are commonly dispersed by another method. I had always found the young seedlings of both D. rafflesiana and D. nummularia coming up either in the runs or nests of Iridomyrmex, and also had often seen a follicle, half or quite dehisced, still containing the silky hairs but no seeds; from these two observations I inferred that the Iridomyrmex removed the seeds. I watched for some time before I was able to prove this, as it is not easy to time the exact moment of dehiscence of a follicle ; at last, however, I was fortunate enough on two occasions to see the ants removing the seeds. On the first of these occasions I noticed a number of Iridomyrmex round a follicle of D. nuwmmularia which was just commencing to dehisce; when first seen it had a small slit at its base for about one-fourth of its length. As this widened sufficiently the ants seized bunches of protruding hairs in their mandibles, and began to pull on them, doing so by walking round the follicle away from the slit on either side, by this means accelerating dehiscence ; when the opening extended nearly the whole length of the follicle, a seed was removed, with the hairs still attached, and carried into the nest. The whole process, from the time the small slit was seen till the first seed was carried into the nest, occupied about half an hour, On the other occasion, also in D, nummularia, the follicle was already 300 Scientific Proceedings, Royal Dublin Society. open, and the ants were removing the seeds, without the hairs, to their nest. It is probable that these seeds are removed and stored for food, those that are not eaten germinating, though there is no evidence that the seeds are stored in one particular place, as the young seedlings are found scattered along the runs at considerable distances from the parent plant. I have several times seen the seedlings growing through holes in the pitchers of D. rafflesiana ; if the ants intended the seeds to germinate, they would hardly choose so unsuitable a place. The supposed preference of D. rafflesiana for decaying trees may be really the preference of the Iridomyrmex, which often makes its runs along dead branches, and uses the dry wood of those branches in the material of its runs and nests. Such branches are not advantageous to Dischidia, as they break off all the sooner when burdened with the weight of the pitchers and their contents ; broken off branches carrying clusters of pitchers may be often seen hanging suspended by the twining shoots of the Dischidia, The Contents of the Pitchers of D. rafflesiana. While the older pitchers of D. rafflestana nearly always have nests of Iridomyrmex, the younger frequently contain only pitcher-roots. “The nests are built round the roots, the roots branching most freely where the nest- material is abundant; root hairs are usually not developed unless the roots are in contact with the nest-material. A microscopical examination of the nest-material showed it to be composed of clay mixed with bits of wood and other vegetable matter ; occasionally fragments of branched, septate, fungal-hyphe were seen, and once or twice some two-celled spore-like organisms. I made several attempts, by keeping the material constantly damp in the dark under a glass, to develop these hyphe, but never obtained any growth. Most observers have mentioned water as a content of these pitchers. I had in previous years, during the dry season, opened pitchers without finding water. Last year (1911) I systematically examined a number of pitchers a few days after rain or while rain was falling, not selecting the pitchers in any way, but examining all within reach, Kerr—Dischidia raflesiana and Dischidia nummularia. 301 The following table gives the results of this examination :— | | Date of examination, . | June 21st.) July 4th. | July 11th. | July 18th. | July 21st.| Totals. | Number of plants ex- ) | 4 amined, 4 J . : : nt : Total number of pitchers ) 41 95 62 | 80 | 19 pay on plants examined, § : re | oh Number of pitchers more H or less pointing down- 9 | 29 wards and capable 22) mm wy ae ti wy 88 holding water, | | cee A he a ee Number of pitchers con- ) 6 1 9 { 1 14 taining water, 4 | A few pitchers were found with minute drops of water on their sides. I regarded this as water condensed from transpiration vapour, and so have not included such pitchers among those containing water in the above table. The pitchers with water were from one-eighth to two-thirds full. I give below some further details about the water containing pitchers. The six pitchers with water found on June 2Ist were all in one group belonging to one plant which was on a nearly erect, decayed branch. I did nos notice if the pitchers were partially separated from the branch. The pitcher with water of July 4th was a rather young one, about one- eighth full of water. There were a few ants in it, but no nest-material. One of the pitchers of July 11th had slightly separated from the support- ing branch, so that a small pocket was formed between its base and the branch ; there was a good deal of nest-material about the roots, and the mouth of the pitcher had been stopped up with the same material ; there were no ants, though there were plenty in the adjoining dry pitchers; they had evidently been flooded out. ‘The other pitcher with water of this date contained no nest, though there were a few ants in the dry part of the pitcher. Of the four pitchers of July 18th one was a young one with pitcher-roots not fully developed ; no ants were present, and it was about one-fifth full of water. The other three pitchers were all together, and formed part of a cluster which had become partially detached from the nearly vertical supporting branch, so forming a pocket in which water could collect, and from which it could run into the pitchers. Two of these three were young and contained no roots at all; in the third there were roots, a little nest- SCIENT, PROC. R.D.S., VOL. XIII., NO. XXIV, 3a 302 Scientific Proceedings, Royal Dublin Society. material and a few ants; in none of the three was the mouth blocked with clay. The pitcher of July 21st was about half full of water, and contained plenty of roots and ant-nest-material. Sometimes, but not at all commonly, other insects are found in the pitchers. The small black ant, Oataulacus granulatus, Latr., mentioned before in connexion with D. nwnmularia, was found inhabiting one pitcher; winged adults as well as workers were present, but they had brought in no clay ; the adjoining pitchers of the same group had nests of Iridomyrmex. On two or three occasions I have found one of the hysanura, usually in fully formed but young pitchers, in which ants have not yet nested. Once I found several scale insects in a similarly empty pitcher. I have never noticed dead insects in the pitchers. Function of the Pitchers in D. vafftesiana. The pitchers of Dischidia rafflesiana lave attracted the attention of many observers ; and various theories have been advanced as to their function. I have not been able to refer to the original articles of the older writers, but have seen two papers in the “ Annals of Botany,” one by Groom,! the other by Scott and Sargant,? which give a good summary of these theories. The chief views which have been put forward may be given as follows :— (1) Beceari regards the pitchers as galls which have become hereditary, and now serve mainly as ant-shelters, the ants protecting the plants from the attacks of other animals; or perhaps Acari, which he found in numbers on a very young pitcher, may regularly visit and deposit eggs in the pitchers at an early stage, thus exciting the characteristic development. (2) Delpino holds the view that the plant is carnivorous, the pitchers serving to entrap insects. (3) Treub’s view is that the pitchers serve to collect rain, and in a less degree to economize the watery vapour given off in transpiration, the detritus sometimes found in pitchers also serving as a food-supply. This view also receives the support of Scott and Sargant, who, however, make a difference between the function of the erect and pendent pitchers. ‘ The former,” they say, “can bave no other function than to store up the water given off as vapour in transportation”; while “the obvious function of the pendent pitchers as catch-reservoirs of rain-water requires no further explanation.’ (4) Groom considers the pitchers to be mainly organs adapted to provide shelter for the ants, on the one hand, and on the other to secure for the use of 1 Groom, loc cit. 2 Scott and Sargant, doe cit. Kerr—Disehidia rafjlesiana and Dischidia nummularia. 303 the plant the materials collected by the ants, while they also confer upon the plant the power of storing up rain-water and substances brought down with it. There is no analogy for Beccari’s theory of hereditary galls. The pitchers have evidently been evolved from flat leaves; traces of that evolution we see in the ontogeny of the plant, and also in such a form as D. Oollyris, Wall., which has concave leaves with purple under-surface. Pitchers developed normally on a plant grown in the Royal Gardens, Kew, though no Acari were present.! I have never seen Acari in young pitchers. ‘'lhere is little evidence either for the view that the plant is carnivorous; dead insects are rarely found in the pitchers; 1 found none in a large series; water, in which Delpino says the insects are drowned, is found in only a small percentage of the pitchers; there are no digestive glands within the pitchers; and, finally, as Treub and others have pointed out, the roots afford a ready means of escape for any insect which may accidentally enter the pitchers. , The remaining views give to the pitchers a combination of two or more of the following functions :— 1. Water reservoirs. 2. Organs for economizing the water-vapour of transpiration. 3. Receptacles for storing humus, detritus, &e. 4, Ant-shelters. There are several strong objections to the water-reservoir theory, i.e., in the sense that the pitchers either catch rain-water directly or water coursing down the branches of the host tree. In the first place, at least 50 per cent. of the pitchers are incapable of holding water; if calculated from my figures in the foregoing table, about 62 per cent.; but the direction of the pitchers may be taken as at raudom and the percentage left at 50, though it must be remembered that a large number of these, owing to their nearly horizontal position, will be able to hold but little water. Water is only found in a few of the pitchers capable of holding it. The pitchers do not naturally occupy a suitable position for catching water, even when pendent; on the contrary, the close apposition of the mouth to the bark of the supporting branch would seem to indicate an adaptation to avoid the inflow of water. I have before mentioned that many of the pitchers containing water had been accidentally separated from their support, so forming a pocket between it and the pitcher in which water flowing down the branch must of necessity collect, and thence filter into the pitcher. ‘This, however, cannot be considered the normal position cf 1 Scott and Sargant, loc. cit. 3a 2 304 Scientific Proceedings, Royal Dublin Society. the pitcher. During the dry season, when the plant is most in want of water, the pitchers contain no water. Finally, quoting Scott and Sargant, “ the inner surface of the pitcher is characterized by its structure as the ¢ranspiring surface par excellence of the plant, this being indicated both by the presence of spongy parenchyma in this region only, and by the relatively large number of its stomata.” It is obvious that this surface could not so function in a - pitcher containing liquid water. ‘Taking all these points into consideration, together with my observations on the plants growing 7 situ, I am strongly of the opinion that the storage of liquid water is not a function of the pitchers, the presence of such water in them being accidental. These objections do not apply to the view that the pitchers are organs for economizing the water-vapour given off in transpiration. ‘The main transpiring- surface of the plant is the inner surface of the pitcher; and as most of the - absorbing surface of the roots is contained within the pitchers, there can be no doubt that the great part of the water-vapour of transpiration is condensed on these roots, or the nest-material, and directly or indirectly absorbed by them. Scott and Sargant have pointed out that the development of the purple coloration turns the pitcher into a dark chamber, into which the negatively heliotropic roots are attracted. I came across an interesting confirmation of this in one of the intermediate forms between foliage leaf and pitcher. This was an almost perfect pitcher in shape, but having no purple pigment; the dorsal root was well developed, but instead of entering the pitcher it had grown round the stem, and become an attaching root. Supporting this is also the fact that the dorsal roots do not, in normal pitchers, make their appearance till some time after the ventral roots, when the pitcher is almost fully developed, and the purple pigment has appeared. The view that the pitchers act as receptacles for storing humus, detritus, &e., and that which regards them as ant-shelters, must be considered together, for they are closely connected. Groom thinks that ‘‘ the solids in the pitchers are partly derived from detritus washed down the stem and branches of the host by the rain; but they are also, and perhaps chiefly, brought by ants which nest in the pitchers.” I think that the fact of these solids being found in both pendent and upright pitchers, not lying in their lowest parts, but built up around the roots, and being of the same material as the ant-runs, leaves no doubt that they have been brought there altogether by ants and not washed in by rain. ‘That they are constantly inhabited by ants I have already shown. ' Scott and Sargant, doc. cit. Kurr—Dischidia rafilesiana und Dischidia nummularia. B05 To conclude, the functions of the pitchers are :— 1. To economize the water-vapour of transpiration. 2. To provide shelters for ants, which in return supply the roots with food- material. Are these two species of Dischidia myrmecophytes ? A myrmecophyte may be defined as a plant living in symbiosis with ants to the mutual benefit of both plant and ants. Both D. nummularia and D. rafflesiana come, I think, within the definition. The adult plants of neither of these two species hold out attractions to ants in the way of special glands. In this connexion, however, the discovery of an apical gland in very young pitchers by Scott and Sargant is very suggestive. Probably at one stage in the evolution of the plant this gland was functional throughout the life of the pitcher. ‘This might explain the meaning of the long, inturned tip, the gland at its end then serving to attract ants into the interior of the pitcher.’ It is possible the very abundant secretion of nectar by the flowers may help to attract ants. D. nummularia remains in flower for about three months— March, April, and May—during which time the flowers are constantly visited by Iridomyrmex. WD. rafiesiana probably does not remain in flower so long, but its secretion of nectar is more copious, though only available to ants for a very short time after the flower opens. I feel on surer ground when I say that the shelter afforded by the leaves— even by the flat leaves—of D. nwmmeularia, much more so by the pitchers of D. rafflesiana, is of distinct benefit to the ants. As Iridomyrmex rarely exposes itself openly, keeping for the most part in its nest or runs, it is reasonable to suppose that it is subject to attack by enemies, which there is some evidence to show are birds and other aunts. The benefit, on the other hand, which the ant confers on the aan is a very great one, as the materials of the ants’ nest are a source of food to the roots. Possibly, also, the ants may protect the plant from some enemies. They always swarm out and attack the marauder when a plant is pulled down. Their bite is not very severe, however; and I have observed caterpillars eating the young leaves of D. nummularia unmolested. It is even possible that they sometimes attack animals detrimental to the plant. Round holes in the pitchers of D. rafflesiana are quite common ; and I believe they are 1 Groom’s explanation of this structure, that it acts like the inturned edge of an ink-pot from which ink cannot. be spilt, can hardly be the correct one, as the pitchers are fixed, ana could not be reversed. 306 Scientific Proceedings, Royal Dublin Society. made by birds in search of ants’ ‘‘eggs.” Such holes are seen plastered up with clay by the ants. The ants are, perhaps, not absolutely indispensable to the plants. D. rafiesiana has been cultivated in England, and was in a flourishing con- dition two years after its importation, at which time no insects were present in the pitchers. Some imperfect experiments of my own, however, tend to show that, under some conditions, the ants may be necessary to the plants. On two occasions I transplanted plants of D. rafflesiana from the jungle to trees in my garden, within three miles of the place where the plants were growing, and at about the same altitude. On the first occasion I brought one plant, on the second two: in each case within five or six days all the ants disappeared; most of them, I believe, died, as their bodies were seen lying in the neighbourhood of the plants; nevertheless, all the plants soon started into growth ; about a month later I noticed that growth had stopped and the pitchers were drying up, and within six months two of the plants were completely dead, the third, which started growth by throwing gut a twining shoot, was still alive, though half the pitchers had withered and dropped off. On examining the remaining pitchers I found that numbers of another ant, Oremastogaster Rogenhoferi, Mayr, subsp. Merrit, Forel, had taken up their abode in them. I do not wish, though, to lay too much stress on these experiments, as other conditions may have been unfavourable to the plants. We have seen that ants are constantly present under the leaves of D. num- mularia; they have also been observed nesting under the concave leaves of D. Collyris; the ontogeny of D. rafiesiana leaves little reason to doubt that it was evolved from a flat-leaved form like D. nwumularia through a form like D. Oollyris with concave leaves ; therefore, I think we may conclude that ants have been closely associated with D. raflesiana through all stages of its evolution, and have had a considerable share in the evolution of the pitcher. Observations on some other species of Dischidia. Dischidia singularis, Craib, is epiphytic on trees in evergreen jungle, chiefly on Quercus Junghuhnii, Mig. It is heterophyllous, having flat elliptical leaves and narrow linear leaves with a small projection on either side of the middle of the blade. The plant sends out long, slender shoots which usually hang free, more rarely climb. ‘Uhese shoots may bear either kind of leaf, but chiefly the narrow form; the elliptical leaf is more often found on young plants. When I first saw this plant, I concluded it was parasitic, as it appeared to Kerr—Dischidia raflesiana und Dischidia nummularia. 307 spring directly from the trunk of the host, no roots being visible; later on, attempting to cut out a plant, I found that it was growing through and com- pletely filling a small hole in the trunk of the host ; this hole communicated with a hollow in the centre of the trunk where the roots were freely branching and surrounded by the nest of an ant. I examined four plants and found the manner of growth to be the same in all, except that some grew through a small slit instead of a hole inthe trunk. The ants were identified as belong- ing to two species of Cremastogaster, C’. biroi, Mayr, var. guadriruga, Forel, and C. Rogenhoferi, Mayr, var. fabricans, Forel. Later I found, in another locality, two plants with no ants near the roots, though there was humus material round them—perhaps only decayed wood. In this species also ants probably play an important part in the life- history. Three of the plants examined grew out of very small holes, and it is difficult to see how they could have reached such a situation if the seeds had not been brought there by ants. Dischidia Collyris, Wall.? I saw two specimens of what I take to be this plant in evergreen jungle at Sriracha, on the east side of the Gulf of Siam; both were on branches which had fallen from lofty trees. The concave leaves were purple beneath, and their edges were applied to the bark of the host so closely that they must be almost as efficient in conserving the water-vapour of transpiration as the pitchers of D. raffesiana. In both plants ants were nesting under leaves, the roots branching freely in the materials of the nest. Dischidia hirsuta, Dene. This species was not uncommon in the same jungle, but it affected moist trunks of trees near the ground and small, often rotten branches of under shrubs. No ants were seen near the plants, whose small scattered leaves would afford them no protection. This species is practically saprophytic, and in becoming so has been able to dispense with the aid of ants. [Expianation oF Praves. 308 Scientific Proceedings, Royal Dublin Society. EXPLANATION OF PLATES XXV.—XXXI1. PLATE XXV. * Dischidia rafflesiana, Wall. Fig. 1. Portion of twining shoot in flower. Natural size. Fig. 2. Flower with calyx, and portion of corolla removed to show column. x 9. Fig, 3. Longitudinal section through column; the horizontal lines, from below upwards, indicate the levels of transverse sections in figs. 5, 6, 9, 7 respectively. The dotted line indicates the path of pollen tubes. x 12. Fie. 4. Glandular cells on nectar ridge. Tig. 5. Transverse section of column, level of base of staminal appendages ; the horizontal line indicates the direction of sections in fig. 8, x 15. 6. Transverse section of column, level of lower end of nectar ridges. x 15. Fie. 7. Tranverse section of column at the level of clips. aillor 8. Part of section in fig. 7 further enlarged. Fig. 9. Seedling. Lettering : p, pollinium; n, nectar ridge; s, staminal appendage; c¢, corolla; k, calyx; 0, ovary; w, anther wings; me, median expansion of style; te, terminal expansion of style; cl, clip; b, band connecting clipto pollinium ; g, gland-cells of nectary. PLATE XXVI. ry = fe) . 1. A run of Lridomyrmex on Metragyna hirsuta, Hay. ; the run branches near upper part of the photograph; two seedlings of D. nuwmmularia are growing in the left-hand branch. Fig. 2. The two forms of D. nummularia ; the upper is the exposed, the lower the shade form. Kurr—Dischidia rafilesiana and Dischidia nummularia. 309 PLATE XXVII. A young plant of Dischidia rafflesiana growing on the trunk of Melanorrhea usitata, Wall.; the flat leaves first formed are seen below the pitchers ; near the lower end of the plant is a lateral branch with two very young pitchers ; some of the pitchers and flat leaves have been partially eaten, probably by a caterpillar: in particular one small imperfect pitcher, the first formed, is nearly destroyed; there were large numbers of Tridomyrmex in these pitchers. PLATE XXVIII. Dischidia nummularia growing on the trunk of Metragyna hirsuta, Hav. This photo- graph shows how closely the leaves lie, forming a very good protection to the nests of Iridomyrmea:. PLATE XXIX. Dischidia raflesiana growing on Hugenia fruticosa, Roxb. This gives a good general idea of the habit of the plant and the random position of the pitchers; some of the twining shoots still carry foliage leaves. PLATE XXX. Dischidia rafflesiana, pitchers and twining shoots with foliage leaves ; round the bases of the pitchers is a quantity of ant-nest-material in which seedling-plants are growing. PLATE XXXI. Dischidia rafflesiana, two pitchers with one side of each removed ; the origin of the dorsal, or pitcher, root from the stem is seen in the right-hand figure ; the ventral root is better seen in the left-hand figure; the ant-nest-material is built up round the pitcher-rootlets. Both of these pitchers are rather young, and the branching of the roots within the pitcher has not reached its full development, nor is there as much nest-material as there often is in older pitchers. SCIENT, PROC. R.D.S., VOL. XIII., NO. XXIV. 3B BT: aise ay'lee ae hey Phoh SP ah REX hy eae toa 1 hie ea oes oii oN asi fou 3 it EEAPRY ie Bn m an SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XXV — [ West, Newman lith. PLATE XXVI Nie PROG] Ry DUBLIN SOGS NESS WOVE Sxcini: SCIE Oven i hs hi fren i {ey uh i ign i a ahe im . SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIIT. PEADRE OxOVin: SKCMAIN/AS IRON, IR, IOVOBILION, (SHOX, INS ig WADE, ASTIN, PILZMINS, MOSOWIDO, SCIEND. PROG: RK. DUBLIN SOG: N:S:, VOLE. XII XXIX. Eile | | | | | | XXX ALVId ‘THX “IOA “S'N “OOS NITANG UY DOAd LNAIOS Di. aya? SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XXXII. ( 4 1 \ Ue bo 10. 11. 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Ivish Pteridosperm, Crossotheca HAdninghausi, Kidston (Lyginodendron oldhamiuwm, Williamson). By T. JouNson, D.so., F.L.S. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorez H. Prruysrives, B.Sc., PH.D. (March, 1911.) 1s. . 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Award of the Boyle Medal to Proressor JoHn Jony, M.A., SC.D., F.R.S. (July, 1911.) 6d. On the Amount of Radium Hmanation in the Soil and its Escape into the Atmosphere. By Joan Joty, sc.p., F.x.s., and Louis B. Smyru, B.a. (Plate IX.) (August, 1911.) 1s. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By HE. A. Newern ARrper, Ma, F.LS., F.G.8. (January, 1912.) 1s 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24, SCIENTIFIC PROCEEDINGS—continued. Forbesia cancellata, gen. et sp. noy. (Sphenopteris, sp., Baily By T. Jounson, D.sc., F.u.s. (Plates XIII. and XIV.) (January, 1912. 1s. The Inheritance of the Dun Coat-Colour in Horses. By Jamzes Winson, ™.A., B.Sc. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jams H. Ponnox, p.so. (Plates XV. and XVI.) (February 21,1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris., By Henry H. Dixon, so.p., F.r.s., and W. R. G. Arxins, wa. (February 21,1912.) 6d. Improvements in Hquatorial Telescope Mountings. By Sm Howarp Gruss, rr.s. (Plates XVII-XIX.) (March 26,1912.) 1s. Variations in the Osmotic Pressure of the Sap of lew aquifolium. By Hunry H. Drxon, sc.p., F.r.s., and W. R. G. Arxins, m.a., a.c. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Dixon, sc.d., ¥.R.s., and W. R. G. Arxins, u.a., atc. (April 9,1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jonson, p.sc., F.u.s.- (Plates XX. and XXI.) (April 12, 1912.) 1s. On the Vacuum Tube Spectra of some Metals and Metallie Chlorides. Part II.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By Jamus H. Potnox, D.Sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s. The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Copper, and Lithium. By Genevizve VY. Morrow, A.R.C.Sc.1. (Plate XXIV.) (May 11, 1912.) 1s. Award of the Boyle Medal to Sir Howarp Gruss, F.z.s., April 16, 1912. (May 18, 1912.) 6d. Notes on Dischidia rafflesiana, Watu., anv Dischidia Numunularia, Br. By A. FE. G. Kerr, m.p. (Plates XXV.-XXXI.) (September 30,1912.) Qs. DUBLIN: PRINTED AT THE UNIVERSULY PRESS BY ’ONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 25. CCTOBER, 1912. RECHERCHES EXPERIMENTALES SUR LA DENSITE DES LIQUIDES EN DESSOUS DE o. PAR JEAN TIMMERMANS. [COMMUNICATED BY PROFESSOR SYDNEY YOUNG, F.RS. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATH, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. Price Three Shillings. Roval Dublin Society. OO FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and § p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. Krrr—Dischidia rafflesiana and Dischidia nummularia. 309 PLATE XXVIII. A young plant of Dischidia rafflesiana growing on the trunk of Melanorrhea usitata, Wall.; the flat leaves first formed are seen below the pitchers ; near the lower end of the plant is a lateral branch with two very young pitchers ; some of the pitchers and flat leaves have been partially eaten, probably by a caterpillar: in particular one small imperfect pitcher, the first formed, is nearly destroyed; there were large numbers of Iridomyrmex in these pitchers. PLATE XXVIIL. Dischidia nummularia growing on the trunk of Metragyna hirsuta, Hay. This photo- graph shows how closely the leaves lie, forming a very good protection to the nests of Iridomyrmex. PLATE XXIX. Dischidia rafflesiana growing on Hugenia fruticosa, Roxb. This gives a good general idea of the habit of the plant and the random position of the pitchers ; some of the twining shoots still carry foliage leaves. PLATE XXX. Dischidia rafflesiana, pitchers and twining shoots with foliage leaves ; round the bases of the pitchers is a quantity of ant-nest-material in which seedling-plants are growing. PLATE XXXII. Dischidia rafflesiana, two pitchers with one side of each removed ; the origin of the dorsal, or pitcher, root from the stem is seen in the right-hand figure ; the ventral root is better seen in the left-hand figure; the ant-nest-material is built up round the pitcher-rootlets. Both of these pitchers are rather young, and the branching of the roots within the pitcher has not reached its full development, nor is there as much nest-material as there often is in older pitchers. SCIENT, PROC, R.D.S., VOL. XIII., NO. XXIy. 3B FeO J XXV. RECHERCHES EXPERIMENTALES SUR LA DENSITE DES LIQUIDES EN DESSOUS DE 0°. Par JEAN TIMMERMANS. [COMMUNICATED BY PROFESSOR SYDNEY YOUNG, F.R.S.| {Read Marcu 26. Published Ocroner 18, 1912.] Introduction, ; 2 F : . 810 | «v. Données numériques, . i . 848 1. Méthodes, . 0 : é oat | y. Discussion des résultats au point de 11. Substances examinées : purification vue théorique, . 5 5 - 3853 et constantes physiques, . 20 vi. Conclusions, . : ‘i 4 5 6 BYAD) um. Choix de l’échelle de températures, 335 | yar. Appendice, . a : . - 32 1. Introduction—lrétude expérimentale de la densité des liquides en dessous de 0° offre un double intérét; au point de vue théorique, elle permet de résoudre plusieurs problémes concernant l’équation d’état des fluides; elle est tout aussi nécessaire au perfectionnement technique des thermométres a liquides destinés 4 la mesure des basses températures. Un pareil travail n’aurait pu étre entrepris il y a plus de dix ans: outre les difficultés que présente toute étude dilatométrique de précision, il s’en rencontre d’autres spéciales au domaine des basses températures, et qui n/avaient pas encore été surmontées a cette époque. Ainsi, je n’aurais pu arriver 4 un résultat précis, si je n’avais eu a ma disposition les recherches faites antérieurement au laboratoire cryogénique de Leyden, sur le coefficient de dilatation du verre et sur le calibrage du thermométre 4 résistance aux basses températures. J’ai done fait usage dans mes expériences de la méthode du dilatométre ; en voici le principe: on enferme dans un récipient thermométrique, appelé dilatométre, une quantité connue du liquide étudié dont on mesure le volume apparent aux diverses températures considérées; le poids du liquide divisé par le volume quwil occupe a4 une température déterminée donne, toutes corrections faites, la densité du liquide a cette température. Sile principe de cette méthode est simple, le degré de précision des expéri- ences dépend essentiellement des soinsminutieux qu’on prend pour éliminer les diverses erreurs systématiques. Un travail préliminaire? m’avait montré que pour réaliser 4 coup sir l’équilibre de température entre le réfrigérant et * Bull. Soc. Ch. de Belgique, 21-395. 1906, Timmermans—La densité des liquides en dessous de 0°. 31 le liquide du dilatométre on doit disposer d’un cryostat capable de maintenir une basse température constante pendant une durée relativement longue; la premiére partie de mon mémoire comprend la description de ce cryostat et une série de détails techniques se rapportant a des mesures de volume et de température. Pour connaitre la valeur absolue des constantes que je déterminais, je me suis efforeé de ne faire usage que de substances parfaitement pures (2° partie), et de fixer avee précision mon échelle de températures (3° partie). Les données numériques obtenues et leur discussion constituent le reste de mon article. Premiire Partie—Merrnoves. 2, Dilatométres (fig. 1).—lLes dilatométres? employés, au nombre de cinquante, avaient la forme de récipients thermométriques avec une boule de six centimétres de haut et de trois cem. de capacité; le tube capillaire de 2 24 em. de long et d’un mm.’ de section était pourvu eae échelle millimétrique gravée sur la tige. Il est facile de lire & la loupe la hauteur @ laquelle un liquide monte dans le capillaire, avec une approximation de 5 de mm., correspondant a une erreur maximum de ;5}5> du volume apparent total. Si javais employé un senl dilatométre pour chaque liquide a étudier, le capillaire aurait été fort long; j’ai préféré faire usage pour chaque liquide de plusieurs dilatométres remplis jusqu’d des niveaux différents et ne faire de mesures avec chacun d’eux, que pour les T* auxquelles le liquide ne s’éléverait pas dans le capillaire au- 2 dessus du cm. 10, compté a partir de la boule; de cette maniére la longueur totale du tube a placer dans le bain eryostatique ne dépasse jamais 16 cm., ce qui est indispensable, avec l'appareil dont je dis- Fig. 1. pose comme on le verra dans la suite. Dés lors les portions du eapillaire, supérieures au cm. 10, deviennent inutiles aux 7’ sous 0°, et pour rendre les dilatométres moins longs et plus maniables, j’ai fait remplacer la plus grande portion du tube capillaire par une boule, de volume variable suivant les cas, souftlée entre les em. 10 et 11 de la tige. 3. Culibrage des Dilutométres.—Ue calibrage a été fait en pesant les quan- tités de mercure pur contenues dans les portions successives de la tige et dans les boules ; j’opérais par double pesée avec des poids contrdélés et en ramenant les pesées au vide, J’ai pris des précautions spéciales (jamais de contact direct avec la main) pour que la 7’ du mercure restat uniforme pendant le calibrage et égale a celle d'un thermomeétre sensible placé a cété du dilatométre. Ce calibrage w été le 16pete deux luis au moins pour chaque tube jusqu’a > Construits par la maison Arno Haak a Téna. 3 J’ai écrit partout 7 pour température. 3B2 312 Scientific Proceedings, Royal Dublin Soctety. concordance a s5}97 prés; une pareille différence peut provenir d’une erreur de } de degré sur la 7’ pendant le calibrage. Tout le calibrage a été ramené au volume a 0°; pour cela j’ai dt tenir compte de la dilatation du verre des tubes. Les dilatométres étaient construits en verre d’Iéna 16% dont le coefficient de dilatation entre 0° et— 200° a été déterminé avec précision an laboratoire d’Onnes a Leyden‘; la contraction de ce verre est d’environ zo4oq par degre. Les mémes facteurs de correction ont servi a calculer également le volume réel du dilatumetre aux diverses 7Z' sous 0°. Le verre d’Iéna 16 présente également l’avantage d’une élasticité partaite: le zéro de mes dilatométres est resté absolument constant depuis plusieurs années méme aprés des immersions brusques et répétées dans lair liquide; a basse température aussi, les observations sont concordantes quand on les répéte a de longs intervalles. Hxemples: (a) Dilatométre a éther 0'1 mm. =0:1°. A 0° le liquide s’éléve dans la tige a 175°3 mm. en 1907. 175°3 mm. en 1908. 175°3 mm. en 1911. (b) Dilatométre a isopentane 0-1 mm. = 0:03°. Le liquide s’éléve dans la tige 4 140°9 mm. au point de congélation de Veau—a 9:1 mm. au point de congélation de Visopentane. Réchauffé brusquement il marque 140°9 mm. au point de congélation de ’eau—aprés trois ans on retrouve 9:1 mm. au point de congélation de l’isopentane. J’aurais voulu répéter mes expériences avec des tubes en verre de Thuringe dont Onnes a également fait déterminer le coefficient de dilatation a basse température ; malheureusement la qualité de ce verre est mal spécifiée, et il m’a été impossible de m’en procurer de nouveaux échantillons. 4, Corrections pour Ménisques (Fig. 2).—Ces corrections sont au nombre de deux. En effet j’ai toujours fait mes lectures de volume en A a Vextrémité du ménisque, et mes calculs sont basés sur l’hypothése que le liquide remplit complétement le capillaire jusqu’a une section horizontale passant par le point A. Or, dans le calibrage au mercure, le volume occupé réellement par le mercure, est inférieur au volume supposé, tandis que pour les autres liquides qui mouillent le verre, ce volume est supérieur au volume caleule ; il faut done faire une premicre correction additive, pour passer du volume réellement occupé par le mercure au volume suppose ; et une seconde pour passer de ce volume a celui des liquides autres que le mercure. 4 Communications from the Physical Laboratory of the University of Leyden. No. 85, V (1903) et 95, X (1906). TimmermMans—La densité des liquides en dessous de 0°. 313 Pour des tubes de faible diamétre, @’aprés Schalkwyk,° le volume d’un ménisque de mercure est égal 4 la moitié du volume d’un eylindre, de méme base 6 et de méme hauteur / que le ménisque (3 44). La base du cylindre peut étre caleulée a partir de mes expériences de calibrage du capillaire et la hauteur nous est donnée en fonction du diamétre de la base par les expériences de Géckel®; j’ai done pu me dresser une table des corrections a faire de ce chef. Pour les autres liquides qui sont étudiés, prés de leur point de fusion, jai admis que la surface du ménisque correspond sensiblement a celle d’une demi-sphére ayant le diamétre du capillaire. Ici, par conséquent, le volume a ajouter est égal au volume d@’un cylindre dont la base est la section du eapillaire et la hauteur le rayon de ce capillaire, diminué du volume d’une demi-sphére de méme rayon. Cette correction est donnée par la formule } a? ou? est le rayon du capillaire. La somme des deux corrections additives cquivaut a environ ;5)59 du volume total 4 mesurer. 5. Remplissage des Tubes (Fig. 3)—Au début des expériences, les tubes ont été passés successivement au mélange sulfurique nitrique, puis x au mélange chromique, a la potasse, rincés a Veau distillée, a Valeool, a l’éther pur et sechés par un courant d’air sec. Il est indispensable de ne remplir le dilatométre que d’une substance pure, anhydre et complétement privée d’air. En effet quand un gaz étranger est emprisonné dans la partie supérieure du capillaire d’un dilatométre, il se trouve soumis a des pressions Q qui varient €normément avec le volume occupé par le liquide aux diverses températures, et s’y dissout plus ou moins. L’équilibre de ce systéme a deux constituants varie done sans : cesse, et ne sétablit que trés lentement. Il en résulte des Mis. 3- variations lentes du volume apparent du liquide méme a température constante. Pour éviter ces inconvénients, j’ai employé pour le remplissage un dispositif inventé par Young. | On soude a l’extrémité du capillaire un petit récipient représenté dans la figure 3. On met en relation avec une pompe a vide. On fait alors a différentes reprises, le vide pour ne laisser entrer que de l’air desséché par son passage sur une colonne d’anhydride phosphorique. ®» Communications . . ., etc., 67, 1 (1901). ® Zeitschrift f. angewandte Chemie, 1903, p.3. Mes valeurs numériques sont extraites du Tandolt- Bornstein, 3° édition, p. 29, 1905; par suite d’une erreur, les valeurs qui y sont données pour la hauteur du ménisque sont dix fois trop furtes, ct je les ai corrigécs en consé ;uence. 314 Scientific Proceedinys, Royul Dublin Society. Quand le tube est bien sec, on détache l'appareil de la pompe et on introduit dans le récipient le liquide a étudier de maniére a ce qu’il recouvre complétement l’extrémité du capillaire a. On fait alternativement un vide partiel qui enléve une certaine quantité d’air du dilatométre, pour revenir ensuite a la pression atmosphérique normale. Le liquide remplit alors par- tiellement la boule du dilatométre; on ferme, au moyen d’une pince, le tube de caoutchoue qui relie ’appareil a la pompe, et on le détache de celle-ci. On fait bouillir le liquide contenu dans la boule du dilatométre, et ses vapeurs entrainent ce qui reste d’air. Par refroidissement la boule se remplit de liquide plus qu’auparavant, et l’on recommence de la sorte jusqu’a ce qu’on ait complétement chassé 1’air du dilatométre. On porte enfin le dilatométre a une 7 connue et une fois l’équilibre établi, on chasse par ébullition le liquide jusqu’a une division du capillaire, calculée d’avance, et on scelle. j En effet, j’ai pu calculer le rapport en volumes du liquide contenu dans le dilatometre, a la 7 de remplissage et a la Z’ ot la mesure de densité devait se faire, en faisant usage des coefficients approximatifs de dilatation de mes liquides purs que j’avais déterminés precédemment, et fixer done a priori le degré de vemplissage de chaque tube a la T ordinaire. 6. Poids du liquide en expérience.—Les tubes calibrés étant remplis, reste a mesurer le poids de liquide pur qui y est contenu. Pour cela j’ai déterminé le volume occupé par le liquide a 0°, et j’ai multiplié cette quantité par la densité du liquide a cette temperature. J’ai porté le contenu du dilatometre a 0° en le plongeant dans un bain de glace fondante. Ici, comme dans toutes mes autres mesures du volume oceupé par le liquide a telle ou telle 7, j’ai eu soin de m’assurer : A, que la colonne liquide était complétement immergée dans le bain ; B, que la hauteur du ménisque restait absolument constante pendant 10 minutes au moins. Dans le cas de liquides trés volatils, j’ai été obligé de tenir compte également du poids de la vapeur saturée qui remplit le dilatomeétre au dessus du liquide et qui se condense a basse 7; car cette correction pouvait atteindre roses du poids total. Les volumes occupés par la vapeur m’étaient connus, et j’ai emprunté les valeurs de la densité des vapeurs saturées, soit aux données de la littérature chimique, soit aux conclusions numériques de la loi des états correspondants. (Voir & ce sujet la 2° partie, § 23.) J’ai également tenu compte de cette correction pour les déterminations de densité sous 0°. TimmermMans— La densité des liquides en dessous de 0°. 315 Reste la constante qui a servi de base a toutes mes mesures: la densité des liquides a 0° par rapport a la densité d’un égal volume d’eau pris a 4°. J’ai déterminé cette densité au moyen d’un picnometre, du type Ostwald modifié par Perkin, avee boule permet- tant la dilatation des liquides de 0° ot se fait le calibragv, A lu Z' ordinaire a laquelle se fait la pesée (fig. 4). Ce picnométre, construit en verre d’Iéna 16%, et contenant un volume d’environ 30 centimétres cubes, a été recalibré a plusieurs années @’intervalle, au moyen d’eau fraichement bouillie; son volume n’a varié que de ;sptzz autour de la valeur moyenne. (Pour des détails supplémentaires voir le 2° partie, § 13.) En résumé, dans toutes ces mesures de volume et de densité, la plus forte erreur systématique, sgq5>, parait étre due a ce que, au cours du calibrage Vig. 4. des dilatométres, la 7’ du mercure n’était pas connue avec une approximation supérieure a 7 de degré. 7. Obtention e¢ Mesure des basses Températures.—La seconde partie du probléme que j’avaisa résoudre consistait 4 préparer des bains de 7' constante et uniforme sous 0°, et d mesurer exactement les Z'ainsi obtenues. La méthode la plus simple et la plus exacte pour maintenir un corps a une 7Z' déterminée au dessus de 0°, est de le plonger dans la vapeur d’un liquide pur, bouillant sous pression constante. C’est ce quia été fait également a basse 7’ par divers savants et notamment par Onnes de Leyden; mais cela nécessite des appareils cofiteux et compliqués, car il faut opérer avec des gaz préalablement liquéfiés, et empécher autant que possible le rayonnement de la chaleur ambiante. J’ai done préféré opérer avec des bains de liquides purs, maintenus rigoureusement a leur point de solidification. J’ai construit pour cela un appareil eryostatique basé sur le méme principe que l’appareil pour eryoscopie, avec Vair liquide comme réfrigérant, inventé par Beckmann.’ Quant a la mesure exacte des basses 7’, elle a fait objet de nombreuses recherches dans ces vingt dernieres années. 7 Zeitschrift f. physikalische Chem, 44, 169 (1903). 316 Scientific Proceedings, Royal Dublin Society. Seuls les thermométres a gaz donnent a ce sujet des indications d’une valeur absolue, mais ils sont encombrants et d’un maniement difficile. Jusqu’au présent travail, les thermoméetres a liquides n’avaient pas fait Vobjet de calibrage suffisamment soigné sous 0°; ii ne restait donc a ma disposition que les thermometres électriques. : J’ai choisi le thermomeétre a résistance de platine qui donne des indications précises et invariables, et dont l’échelle, grace aux recherches de Travers et de Onnes, peut étre ramenée a l’échelle thermodynamique avec une approximation suffisante pour mes essais. (Sur le choix de 1’échelle, voir 3° partie.) 8. Description de Vapparetl cryostatique (tig. 5)—Mon appareil était composé des piéces suivantes :° A. Un vase de Dewar, profondeur intérieure, dh i 25cm.; diamétre intérieur, 10cm. Les parois sont complétement argentées, sauf sur une ligne f df ey de 2 cm. de largeur faisant tout le tour de l’ap- pareil de haut et bas, de maniére 4 pouvoir observer par transparence le contenu du vase. | | B. Un second vase de Dewar, hauteur in- térieure, 20 cm., diamétre intérieur, 6 cm., s’y PACH DARA AAA ill trouve suspendu. A Ce vase n’est pas argenté; il est pourvu dune tubulure latérale avec robinet rodé ; cette tubulure est mise en communication avec une " a | Vi; x pompe a main et un manométre permettant de TT iTarTuTNH il régler 4 volonté la pression entre les parois du AT TT i | vase. C. Entrant 4 frottement doux dans le vase précédent un grand tube eylindrique dont la partie supérieure sengage dans l’armature de Se Pélectro-aimant; diamétre intérieur, 53 em.; hauteur intérieure totale, 25 cm.; hauteur Se intérieure utile, 17 cm.; volume intérieur utilisable pour le bain cryostatique, 3 litre. ae Ce tube est fermé par un bouchon de liége eer percé de 3 trous par lesquels je pouvais intro- duire dans le bain, soit mes dilatométres, soit la tige de mon thermométre de platine. L’indépendance des diverses parties de ’appareil rend possible le remplace- ment des dilatométres sans arrét de l’agitateur, ou bien le changement de bain sans perte de mélange réfrigérant. 8 Construit par la maison Fr, Hugershoff, a Leipzig. TimMrermans—La densité des liquides en dessous de 0°. 317 D. L’agitateur électro-magnétique plongé dans le cylindre © était formé dun cercle de fer doux, relié 4 une tige centrale par 3 rayons. disposds symétriquement; sur la tige venaient s’attacher de méme 2 autres cercles contribuant a l’agitation. Cet agitateur était suspendu au bouchon par l’intermédiaire d’une petite spirale d’acier formant ressort. L’électro-aimant était mis en action par un courant de 70 ou 110 volts et 0°15 ampere. Linterruption et la prise alternative du courant, assurant la chute et ascension de l’agitateur dans le bain, était produite par intercalation d’un métronome dans le circuit. 9. Mesure des résistances du thermométre de platine.—Les mesures de résistances ont été faites par la méthode usuelle du pont de Wheatstone avec galvanométre 4 miroir, employé comme indicateur du zéro; le circuit n’était fermé que pendant la courte durée des mesures, pour éviter l’échauffement du fil de platine et une augmentation de résistance con- -comitante. Enfin on ne fermait le courant qu’avec une clef thermoélectrique spéciale, systéme Griffiths,? permettant d’éviter les courants induits. La boite de résistance était une “ Callendar and Griffiths self-testing bridge” du type le plus perfectionné, construite spécialement pour les mesures de basses 7'.° Les résistances fixes varient de 45 ohm a 12.8 ohms; elles sont pourvues de contacts au mercure systéme Collins, éliminant complétement les erreurs provenant de résistances de passage. Le fil offrant une résistance totale de ;'3, d’ohm est pourvu d’une gradua- tion et d’un vernier permettant de lire le ;5455 d’ohm; le contact avec le fil est assure par un systeme de déclanchement produisant une pression moyenne et toujours semblable a elle-méme. - Les résistances de comparaison sont construites en fil de Manganine pour lequel la variation de résistance avec la 7'est trés faible (-,75 > par degré) ; de plus, la boite est construite de fagon a ce que toutes les résistances soient plongées dans un bain de paraftine liquide trés volumineux dont la grande masse s'oppose 4 des changements brusques et irréguliers de 7’; je n’ai done pas eu a tenir compte ici des variations de résistance avec la 7; qui étaient absolument négligeables. - 9 Décrite dans |’ Electrician, 1907. ~ 10 Construite par la Cambridge Scientific Instrument Co. Voir catalogue de la C. 8. I. Co. (‘‘ Thermométrie de précision’’). SCIENT. PROC. R.D.S., VOL. XII., NO. XXY, 30 318 Scientific Proceedings, Royal Dublin Society. Toutes les résistances avaient été recalibrées par rapport ala plus élevée d’entre elles ; les corrections de ce chef n’ont jamais dépassé quelques dix- milliémes. iar En résumé, les résistances du thermométre de platine ont pu étre mesurées avec une approximation de ;y4y,, représentant une erreur tout a fait néglige- able de 0:01 de degré et dépassant méme la limite de sensibilité de mon galvanometre. 10. Thermometre a résistance de platine—C était un appareil construit d’aprés Callendar avec résistance de compensation pour éliminer influence du fil abducteur. La résistance thermomeétrique proprement dite est un mince fil en alliage de platine et d’argent, enroulé sur un support de mica et protégé par un tube en verre. La liaison du thermométre au restant du pont de Wheatstone était assurée par des fils dont les soudures sont contenues dans une boite maintenant la T uniforme, pour éliminer les effets thermoélectriques secondaires. Cet instrument, malgré les soins apportés & sa construction, m’a causé assez bien d’ennuis; la boite qui protége les soudures lui donne des dimen- sions génantes; ensuite la résistance thermométrique proprement dite n’étant pas en contact direct avec le milieu se met difficilement en contact de température avec celui-ci: on n’obtient de résistance nettement mesurable que par immersion dans un bain dont la température est invariable: Hnfin les constantes de l'appareil ont subi des variations d’abord rapides, puis de plus en plus lentes, mais toujours perceptibles méme apres son maintien & + 100° pendant plusieurs heures. Ces constantes sont au nombre de deux: 1° la résistance 4 0° déterminée dans la glace fondante; 2° le coefficient de variation de la résistance avec la température au-dessus de 0° ou “intervalle fondamental ”’ ; cet intervalle a été caleulé a partir de déterminations de la résistance & + 100° faites dans un bain de vapeur 4 doubles parois avec de l’eau fraichement distillée et en tenant compte de la pression barométrique. Le tableau suivant contient la valeur des deux constantes déterminées a différentes époques :— a Cambridge, Dublin, Dublin, Bruxelles, Bruxelles, Peet 1907. 1907. 1908. 1908. 1909. Intervalle fondamental, 0:9938 09956 0:9966 0:9966 0:9955 Résistance, ~ 0 - 2°6811 2°6852 2°7535 2°7548 ~ -2°7528 Dans tous les calculs sur les températures, j’ai fait usage de la valeur la plus récente des constantes; il n’en subsiste pas moins une incertitude qui eut aller jusqu’au 0° i équiv: rreur 1° sur p a Jusquau 0°1, ce qui équivant & une erreur de todos Sur la densite. TimmerMans—La densité des liquides en dessous de 0°. 319 11. Description @une eapérience duns le cryostat.—On commence par introduire le liquide pur a congeler dans le cylindre intérieur; on y place deux dilatométres et le thermométre, et on met l’agitateur en mouvement, puis on verse le bain réfrigérant dans le vase extérieur. Le vase de Dewar intérieur, bien desséché a l’avance pour éviter la formation de fleurs de glace qui empécheraient les lectures du dilatométre, est laissé sous pression atmosphérique jusqu’au début de la solidification du bain eryostatique. Tl est important qu’aprés une légére surfusion, le liquide du bain cristallise brusquement en petits cristaux répandus dans toute la masse, et non pas en un culot grandissant a partir du fond ni surtout en couches collées sur les parois du tube, car alors la solidification du liquide interne s’arréte et jamais un équilibre de Z' ne pourrait se produire. Pour réaliser ce desideratum, il faut que le bain réfrigérant soit maintenu a une 7’ inférieure d’au moins 15 a 20°, au point de solidification a atteindre; lair liquide peut done servir a congeler jusqu’a 1]’éthylene (- 170°), tandis qu’avee les mélanges carboniques qu’on ne peut rendre trop opaques, le chlorbenzol est le dernier corps a se congeler (— 45°). La cristallisation se produit généralement au méme moment dans toute la masse, et, au bout de quelques minutes, une 7’ stationnaire est atteinte ; pourvu que l’agitateur ne s’arréte pas, il est alors possible de maintenir cette 7' absolument constante pendant des heures, ce qui permet de faire tout une série de déterminations successives dans un méme bain. Mais il faut pour cela qu’une fois la cristallisation commencée, l’action du réfrigérant extérieur wintervienne plus que pour compenser le réchauffement du bain aux dépens de latmosphére ambiante. Pour y arriver, il faut rendre la réfrigération moins active qu’auparavant, ce que l’on obtient en réduisant la pression intérieure du vase de Dewar, a une valeur variant en 5 et 20 cm. de mercure, suivant la différence de 7’ entre les deux bains. Dans ces conditions, la hauteur du liquide d’un dilatométre lue par transparence dans l’appareil, reste absolument constante, aussi longtemps qu’on veut, et la résistance du thermométre de platine, dont les valeurs étaient jusqu alors erratiques, devient également brusquement constante. Comme il est difficile d’empécher la condensation d’une faible quantité Whumidité atmosphérique & Vintérieur du vase cryostatique, i est bon @employer, comme liquides pour bain, des corps tort peu hyyroscopiques dans lesquels l’eau se dissout si peu & basse 7, que le point cryohydratique des solutions coincide en pratique avec le point de congélation du liquide yur. 320 Seientifie Proceedings, Royal Dublin Society. / 2° ParrizE—SuBSTANCES EXAMINEES : PURIFICATION WL CONSTAN'TES PHYSIQUKES. 12. Choix des substances étudiées.—Au cours de ce travail j’ai di: preparer des corps purs pour deux destinations différentes: pour l’étude du coefficient de dilatation et comme bain cryostatique. Les liquides dont j’ai examiné la variation de densité avec la température ont été choisis parmi les substances dont le point de congélation est suffisamment bas, de maniére a comprendre des représentants des principales catégories de substances organiques, en donnant la préférence a des corps qui avaient déja fait objet de mesures semblables 4 haute température, par S. Young notamment. Quant aux substances dont je voulais me servir comme bain cryostatique, une recherche préliminaire" m’a guidé dans le choix d’une série de composes dont les points de fusion s’étageaient réguliérement par intervalles de 7° a 10° entre 0° et -158°. Autant que possible, je n’ai pris pour cet usage que des corps dont il est facile de se procurer de grandes quantités, qui soient peu hygroscopiques et stables au contact de lair. La nécessité de disposer de bains cryostatiques de température constante, autant que le désir de faire des déterminations d’une valeur absolue, m’a engagé a accorder une grande attention a la purification des produits chimiques en expérience. Le mode de purification adopteé a été la distillation fractionnée, combinée a laction de réactifs appropri¢s (des- hydratants, ete.) ; les critériums de pureté sont la constance de la densité a 0°/4° et des points d’ébullition et de congélation. (Ce dernier chapitre ne sera traité que dans la 3° partie.) 13. Critériums de Pureté: Densité.—J’ai choisi comme critérium de pureté essentiel la densité aux diverses températures depuis 0°, jusqu’au point de congélation, parce que telle était précisément la constante que je voulais déterminer; je ne me suis considéré comme satisfait qu’aprés avoir réeussi 4 préparer a partir de différents échantillons des produits dont la densité fut constante, aux erreurs de lecture prés, c’est-a-dire + 3p} 55- Les densités ont été mesurées au picnometre de Perkin (fig. 4), qui présente sur celui d’Ostwald-Sprengel deux avantages: on peut le remplir a 0° et faire la pesée a la température de la balance, la boule permettant une dilatation du liquide sans perte; de plus, on évite dans les manipulations subséquentes au remplissage, des erreurs provenant de pertes éventuelles de substance s’écoulant par les capillaires trop remplis. Le picnométre employé a été décrit (1° partie, § 6). , Toutes mes mesures ont été faites 4 0°, par rapport a l’eau prise a son "| Bull. de la Soc. Chim. de Belgique, 24, 300, 1911. Timmermans—La densité des liquides en dessous de 0°. 321 maximum de densité 4°; les mesures 4 0° dans la glace me paraissent prée férables & celles faites A 15°, 20°, ou 25°, car on évite ainsi Pusage du thermostat toujours ennuyeux 4 régler et dont la température n’est exacte- ment connue que pour autant quel’on dispose d’un thermométre pourvu d’une table de correction. Les pesées ont été ramenées au vide au moyen de la formule ree? @ , 0001 0-001 } d, 1 ohn ou d, représente la densité corrigée, «/, la densité observée, 8°5 la densité des poids de laiton usuels et 0:0012 le poids du cem. d’air pris dans les conditions ordinaires de température, de pression et d’humidité; cette derniére valeur est une moyenne dont les valeurs réelles peuvent dans des cas extrémes s’écarter suffisamment pour entrainer une erreur de + ;5}75 sur le poids spécifique des liquides de faible densité (éther, hydrocarbures, etc.), alors que la correction est elle-méme de l’ordre du 7755 (Wade).” En prenant les précautions indiquées, j’ai pu déterminer la densité avec une grande exactitude: les diverses valeurs observées pour un méme liquide nont jamais différé entre elles ni des déterminations de S. Young a plus de sat: 14. Température @ébullition—La valeur absolue du point d’ébullition est aussi un excellent critérium de pureté, mais il est d’un usage plus délicat, par suite des diverses corrections a faire subir aux observations. J’ai évité systématiquement les corrections aléatoires pour la colonne de mercure émergeante du thermométre, en la plongeant complétement dans la vapeur. Ensuite j’ai caleulé & partir de mes propres observations la variation du point d’ébullition des diverses substances examinées, pour un changement de pression barométrique de 10 mm., ce qui permet de ramener toutes les températures d’ébullition 4 la pression normale de 760 mm. Reste la correction la plus délicate, celle qui consiste 4 ramener les lectures faites sur divers thermomeétres (j’en ai employé plus de 10) 4 une méme échelle de températures absolues; j'ai adopté comme reperes les points d’ébullition indiqués par Young pour diverses substances que j’ai eu également l’occasion de purifier—températures que ce savant a mesurées au thermomeétre a gaz ; j’ai pu observer de la sorte que, dans la presque totalité des cas, les points d’ébullition que j’ai obtenus concordent absolument avec ceux de 8. Young.. Jusqu’a 150°, les échelles de températures des divers observateurs concordent, mais au dela, elles divergent de plus en plus (voir tableau No.1). J’ai continué cependant a me baser sur les données de Young, qui a trouvé pour le point d’ébullition de la naphtaline une valeur en parfait accord avec les meilleures déterminations récentes. 1 Journal of the Chemical Society of London, 95, 2174, 1909, 322 Scientific Proceedings, Royal Dublin Society. Tasieau LI. Températures @ébullition. Substances étudiées. 8S. Young. Kahlbaum.!* Perkin. !4— Brombenzol, 156-15° 155°5° = = Aniline, 184-40° 183-9° 183-4° 183'7°.15 (Thorpe). Naphtaline, 218:05° — — 218-05°.18 (Aten). Pour le brombenzol 8. Young” a indiqué 156:0° calculé au moyen d’une formule d’interpolation, mais l’observation directe lui avait fourni 156°15° en parfait accord avec mes propres déterminations. Ces reperes étant choisis, j’y ai rapporté toutes les autres températures par l’intermédiaire de thermométres Baudin donnant le 1° et dont j’ai pu apprécier les qualités d’ exactitude, de constance, et de régularité. 15. Méthode de purification: la distillation fractionnée.—Pour préparer des corps trés purs, il est presque indispensable d’opérer sur de grandes masses de produit, et de partir d’échantillons commerciaux de trés bonne qualité; le traitement des produits techniques bruts est communément tres laborieux et plus facile a opérer en grandes masses comme on le fait dans l’industrie ; il reste alors, aux travailleurs de laboratoire, 2 éliminer les dernieres traces d’impureté, ce qui dans bien des cas est déja suffisamment long; a ce point de vue, les produits de la maison Kahlbaum, que j’ai presque toujours employés, sont trés recommandables. La méthode de purification adoptée est la distillation fractionnée ; je me suis servi des excellents déphlegmateurs de Young (“ modified evaporator still-head ”) ; j’ai poussé le fractionnement jusqu’a constance absolue du point d’ébullition 4 + 0°01° (lectures a la loupe); j’ai vérifié également la constance de densité des diverses fractions. Mais la distillation seule peut ne pas suffire 4 préparer des substances pures, entre autres dans le cas ot existe un mélange a température d’ébullition minimum ; il sera done prudent de s’assurer encore de Vhomogénéité des substances distillées en les soumettant 4 un autre mode de fractionnement (la congélation, par exemple) ou a un traitement chimique appropric; j’al choisi le second mode opératoire. 16. Réactifs deshydratants. — L’anhydride phosphorique. — Les réactifs les plus employés au cours des processus de purification sont ceux qui enlévent l’eau et l’aleool mélangés aux produits organiques; il faut que ces réactifs soient 4 la fois assez avides d’eau pour produire une deshydratation complete et néanmoins incapables d’altérer le corps a purifier, enfin 13 Zeitschr. fiir Ph. Ch. 26, 577 et 603 (1898). M Journ. of the Chem. Soc., 45, 430 (1884); 55, 691 (1889); 69, 1244 (1896). 16 [bid., 37, 196 (1880); 63, 283 (1893). ‘6 Zeitschr. fiir Ph. Ch. 78, 1 (1911) ; (avec la bibliographie du sujet). 7 Landolt-Bornstein, 3° édition, 146 (1905), Timmrermans—La densité des liquides en dessous de 0°. 323 faciles 4 extraire du milieu réactionnel a la fin de leur action; l’anhydride phosphorique est la substance qui réunit le mieux ces diverses qualités. Lianhydride phosphorique absorbe l’eau en se transformant en acide métaphosphorique dont la tension de vapeur n’est pas mesurable (Morley *) ; de plus il enléve complétement l’alcool mélangé a d’autres corps, mais ne réagit pas avec la majorité des substances organiques. Quand son action est terminée, on peut distiller directement le liquide pur, mais il faut opérer au bain-marie, sans quoi l’attaque du verre est trop rapide; quand la substance a purifier bout a haute température, on peut séparer tout d’abord P.O; par décan- tation ou filtration, et dans ce cas également, la perte de substance reste faible. L’anhydride phosphorique convient spécialement pour la dessication des hydrocarbures de la série grasse (a la fin de lopération, on le retrouve a peu prés inaltéré, a l'état d'une poudre blanche), des éthers-haloides et des nitriles (auxquels il enléve les alcools qui forment avec ces produits des mélanges température d’ébullition minima), des hydrocarbures et éthers haloides de la série aromatique (il forme alors des solutions colloidales tres diluées, ot une portion de P.O, passe au travers des filtres en donnant une liqueur opalescente blanchatre, se clarifiant a 1’ébullition), du sulfure de carbone, des éthers-oxydes (dans ce cas il est préférable au sodium métallique, incapable d’enlever complétement l’aleool en présence)—avec les éthers sels préalablement desséchés sur du carbonate de potassium, il donne aprés des traitements répétés et suivis chaque fois d’une distillation, un gel brunitre (sauf avec le formiate de méthyle: gel blanc); Vapparition de ce gel qui a l'état stable envahit toute la masse liquide et se fluidifie a l’ébullition est le meilleur eritérium de deshydratation des éthers-composés; apres distillation, ’anhydride phosphorique reste sous forme d’un résidu noir; l’aleool qui donne également avec les éthers des mélanges 4 point d’ébullition minimum est enlevé com- plétement dans la méme opération. Au contraire voici des cas ot l'emploi de P,O; est peu recommandable ; . avec les acides gras, il est incapable de deshydrater a fond V’acide formique (Sapojnikow™) pour lequel la congélation fractionnée est préférable; avec la pyridine dont le traitement par P.O; (recommandé par Freundler) entraine des pertes énormes. Quelquefois des traitements répétés par P.O; conduisent a une décomposition du produit a deshydrater (acétone, chloroforme). 17. Les autres deshydratants.—Quand l’emploi de l’anhydride phosphorique est impossible, il faut recourir 4 d’autres deshydratants, parmi lesquels la chaux vive et le sodium métallique sont spécialement intéressants. . Lia chaux vive est facile 4 préparer par calcination prolongée de marbre pur; l’aspect du produit qui se délite au contact de faibles quantités @humidité, permet d’apprécier les progrés de la deshydratation. 18 Journ. de Chimie Physique, 3, 241 (1905). 19 Jour, dela Soc. Physico-chimique russe, 2, 2° partie, 626 (1893), et 28, 2° partie, 229 (1896), 324 Scientific Proceedings, Royal Dublin Society. - La chaux est préférable a la potasse, qui produit souvent le charbonnement des liquides organiques surchauffés au cours de la distillation (pyridine, éthylamine), et a la baryte, qui introduit quelquefois de l’eau dans la liqueur ‘par suite d’une réaction réversible (dans les alcools, par exemple, suivant Crismer) .”° La chaux vive, laissée au contact de la liqueur pendant un jour, au bain-marie porté a l’ébullition, est recommandable pour la deshydratation des alcools de la série grasse, autres que l’alcool méthylique (procédé Crismer), et des bases de la série pyridique (Bouveault a employé dans ce cas -la baryte). La chaux ne convient pas pour les cétones, qui sont condensées, méme a froid. Iie sodium en rognures ou en fils a été recommandé pour Th des- hydratation de V’alcool méthylique (Crismer) ; Young se contente d’une distillation au moyen d’un bon déphlegmateur—on peut l’employer pour deshydrater l’éther, mais un traitement préalable par l’acide sulfurique et Yeau est alors nécessaire pour extraire l’alcool présent ;—enfin le sodium permet une deshydratation et purification complétes du méthylal; ce corps ne résiste pas a action de P.O, et donne alors des produits de polymérisation aldéhydiques (trioxyméthyléne, etc.). Quant -aux différents sels qu’on a renoinaandés comme deshydratants (CaCl,, COsNa,, SO,Cu, SOiNa,, ete.), la tension de dissociation de leurs — hydrates est trop élevée a la température ordinaire pour pouvoir étre négligée: il faut méme prendre garde de ne pas mettre au contact d’une liqueur parfaitement anhydre, des fragments d’un sel qui ne serait pas completement privé de son eau de cristallisation, car on risquerait de voir cette eau s’évaporer en quelque sorte dans le milieu sec mis a sa disposition, jJusqu’a ce que la pression osmotique de l’eau en dissolution soit en équilibre avec la tension de dissociation du sel hydraté, a la température considérée. On ne pourra done se servir de ces sels que pour priver un liquide de la majeure partie de l’eau quil contient, quitte 4 terminer la dessication sur un agent approprié. Le chlorure de calcium fondu a cet avantage d’enlever a la fois l’eau et Valeool d’un liquide a deshydrater, en formant les combinaisons addi- tionnelles correspondantes (hydrate, alcoolate). Le carbonate de potassium, bien neutre, préparé par décomposition ignée du bicarbonate, se recommande pour le premier traitement des éthers-composés, car il neutralise les acides libres quils pourraient contenir et qui seraient capables d’hydroliser une proportion notable de l’éther sel pendant les distillations subséquentes,— Enfin le sulfate de cuivre blanc anhydre a été employé par Perkin, pour la dessication des cétones et des aldéhydes, corps trop instables pour résister a *9 Bull. de la Soc, Chimique de Belgique, 18, 1 (1904). Trmmermans— La densité des liquisles en dessous de 0°. 325 des agents plus énergiques (j’ai observé cependant une condensation partielle d’acétone restée longtemps en contact avec SO,Cu). 18. Constantes physiques de 25 liquides organiques purs.—J’ai réuni dans le tableau IT. (§ 19) les constantes physiques des corps organiques que j’ai dt préparer a l'état pur; voici les données des diverses colonnes. A. Le nom de la substance examinée. B. Ia température d’ébullition telle que je |’ai observée; Vindication +... représente en centiémes de degré la variation de la température d’ébullition durant une distillation. C. La température d’ébullition indiquée par 8. Young ou par d'autres auteurs (dont le nom est alors insecrit entre parenthéses). dt D. La variation dp @ébullition pour 10 mm. de pression d’aprés mes observations. H. Idem, d’aprés les observations de 8. Young ou d’autres auteurs. F. La densité a0°/4°, telle qu’elle résulte de mes expériences ; Vindication + es . . . représente en wnités de la cinquieme decimate ao-a00 2 variation maxima 5) de densité observée dans une série de mesures répétées sur divers échantillons de la méme substance (entre parentheses est indiqué le nombre de fois que Vexpérience a été faite). G. La densité a 0°/4°, indiquée par S. Young ou par d’autres auteurs. En examinant le Tableau II. on pourra se rendre compte du degré de pureté des corps que j’ai préparés et de l’exactitude des valeurs indiquées pour les constantes. Hn comparant mes données a celles de S. Young, on reconnaitra généralement un accord presque absolu; dans le cas ow les données comparables aux miennes n’existent pas chez S. Young, l’accord avec les valeurs numériques fournies par les autres observateurs laisse souvent A désirer ; aussi ai-je cherché 4 me rendre compte, par une étude attentive des mémoires originaux, du degré de confiance 4 accorder aux travaux de mes prédécesseurs. J’ai suivi généralement les méthodes de purification indiquées par S. Young” dans ses travaux classiques, auxquels je renvoie pour de plus amples détails ;” pour les corps dont cet observateur ne s’est pas occupé, on trouvera des renseignements supplémentaires dans les § 20 et suivants. *1 Philosophical Magazine, 50, 291 (1900), et communication privée de résultats en partie inédits de S. Young, de Thomas, et de Miss Fortey. * Young: Trans. Chem. Soc. 71, 446 (1897). (Pentane-normal.) Young: Proc. Phys. Soc. 18, 602 et 658 (1895), et Q. J. Ph. Ch. 29, 193 (1895). (Isopentane. ) Young: Trans. Chem. Soc. 59, 125 (1891). (Chlor. et Brombenzéne.) Young: Trans. Chem. Soc. 59, 911 (1891). (Létrachlorure de Carbone. ) Ramsay et Young: Phil. Trans. Royal Soc. 178, 57 (1887). (Ether.) Ramsay et Young: Phil. Trans. Royal Soc. 178, 313 (1887). (Alcool méthylique.) Young et Thomas: ‘Trans. Chem. Soc. 63, 1191 (1893). (Acétate et Propionate d’éthyle.) SCIENT. PROC., R.D.S., VOL. XUI., NO. XXV, 3D n Socrety. yal Dubhi qs. Ro ? 0 Serent 326 fie Proceed ~*~. ——— - wemea | ve “rer ~~ es LIGTL-0 } | . 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Canvqiyry) .9-061 f| 1 * 08-161 ele monued 8G 089-0 09-0 (JT neatqei 110A) .0-9¢T I + .GI-9eT © * OZMoqolg “TZ o8F-0 o6F-0 00-281 I ¥ 000-81 ~ = *TOZUAqLOTYD “0% 3 “arSiignp ennea¥ “aT oGT-LL J ee! i ; = 068-0 of8-FE1 GF oGg- FEL fanbuisinqosy aploy “GT = o0F-0 | og TIMI) oF GF O8-GF ~ * RAUIOTL “BT sa(SHPID) 88-0 | .08-0 oF 9 I F 01-99. ” e ‘ALOJOW “ST a 328 St ientific Proceedings, Royal Dublin Society. 20. Hydrocarbures de la série grasse et leurs dérivés halogénés.—L’ échantil- lon de pentane normal a été mis a ma disposition par M. Young; ce corps avait été préparé par distillation fractionnée d’une grande masse d’éther de pétrole. Ses constantes concordent trés bien avec celles des autres échantillons préparés par le méme auteur. Le point d’ébullition ealculé par M. Young au moyen de la formule de Biot est 36°13, et il a aussi trouvé récemment le point d’ébullition plus bas que 36-3. I] y avait, sans doute, une erreur dans le thermométre, dont il a fait usage auparavant. L/’isopentane mélange & de petites quantités d’amyléne, est vendu par la Maison Kahlbaum sous le nom de ‘‘ Pentan fir Thermometer”; cette substance a été purifice par la méthode de S. Young; outre ses autres constantes, j'ai déterminé la température critique de dissolution dans l’ortho-nitrotoluol: au cours d’un fractionnement, cette température a varié entre 9°0° et 9:1”. Le bromure d’éthyle et le chlorure d’éthyléne préparés par Perkin, Thorpe, ete., contenaient sans doute de Valecol, ce qui explique la valeur trop faible des densités données par ces auteurs. Tasrieau III. ; Ut } j : a ae Chloroforme i = 035° Regnault a trouvé 0°39°, mais son produit était impur. Auteurs Purification | TG Ebu: | d 0°/4° d 15°/4° Impuretés Timmermans, | P20; 61-20° 1°52636 + 5 | 1:49845 — 9” | méme produit oxydé | 61:20° 1°52668 | — HCl + COCl: S. Young, . | P205 | 61°20° | — | — _ Wade, | HeS04 61°16° | — | 1-49889 “= [rea P205 | oer | = | 1:49957 oxydé (?) | Thorpe, . | as | oie 4 1:52657 £ 4 = = | Regnault *8, . | — | 60:°2° | — = alcool | | {N.B.—Quand la comparaison des densités a di étre faite 4 une température autre que 0°, Verreur peut atteindre quelques dix milligmes 4 cause du peu d’exactitude du coefficient de dilatation. ] Le cas du chloroforme est intéressant (‘'ableau III); le produit médical contient toujours de l’alcool (ce qui entraine une diminution notable de la densité), avec lequel il forme un mélange a point d’ébullition minimum et qui le rend plus résistant a l’oxydation atmosphérique et a l’action de la lumiére; une fois l’eau et Valcool enlevés par PO,, il tend a se décomposer en HCl + COCI,, corps trés toxique, qui rend la densité du chloroforme trop 40 Journ. Ch. Soc., London, 85. 988, 1904. ‘Timmermans—La densité des liquides en dessous de 0°. 329 élevée ; a haute température, la dissociation est encore plus rapide et plus compléte avec dépot de carbone (Pictet). Un échantillon de chloroforme partiellement oxydé peut étre régénéré par traitement au carbonate de potassium et distillation sur P.O; frais. Wade a dailleurs montré qu’il est possible de préparer du chloroforme pur par simple fractionnement d’une grande masse du produit médical. Le chlorure dallyle a été préparé a partir d’un échantillon de Merck; sa pureté ne semble pas garantie. 21, Les composés oxygénés de la série yrasse.—Je n'ai pu abaisser la densité de mon alcool méthylique en dessous de 081015; il contient sans doute des traces d’une impureté autre que l'eau. On trouvera dans le tableau IV une étude comparative de l’action de quelques déshydratants sur l’acétone. Presque tous les auteurs sont partis d’acétone purifiée au moyen de la combinaison au bisulfite : leur produit ne pouvait done plus contenir comme impureté que de eau. D’aprés Makovicki," la courbe de tension de vapeur des solutions aqueuses d’acétone s’abaisse directement a partir de l’acétone pure; la distillation fractionnée au moyen d’un bon déphlegmateur devrait suffire par conséquent a opérer la séparation des deux constituants, mais Pexpérience ne ratifie pas cette maniére de voir; comme Makovicki n’est pas parti d’une acétone rigoureusement anhydre, il se peut que la présence d’un mélange a tension de vapeur maxima lui ait échappé; mais il est plus probable que la courbe de tension de vapeur est simplement trés aplatie aux environs de l’acétone anhydre et une séparation compléte est dés lors trés difficile. On voit aussi que ni la constance du point d’ébullition, ni sa valeur absolue n’est un bon criterium de pureté pour ce produit; la température critique de dissolution n’est pas non plus d’un usage tacile dans ce cas, car Pacétone est soluble en toutes proportions dans le pétrole, méme a 0°. Par leur densité, les échantillons de Perkin, de Squibb, et de Zander concordent avec le mien d’une maniére satisfaisante; pourtant ces auteurs sont d’accord pour déclarer quils n’ont pas une complete confiance en la siecité absolue de leur acétone ; en répétant leurs essais, je nai pu confirmer non plus leurs bons résultats; le seul deshydratant qui m’ait fourni des échantillons bien homogénes et des propriétés constantes est l’anhydride phosphorique ; malheureusement il reste au fond du ballon, a la fin du fractionnement, un résidu important formé par une masse visqueuse d’acide métaphosphorique mélangée a des produits de condensation, et les pertes qui en résultent peuvent atteindre } du poids total. Hn résumé on ne connait encore aucun procédé de deshydratation de l’acétone qui soit absolument satisiaisait. 41 Journ. Rus. Phys. Chem. Gesellsch. 40, 216, 1908. 330 Scientifie Proceedings, Royal Dublin Society. Tasieau LV. Acétone — = 0°30°: Crafts a trouvé 0°38° avee un produit trés impur. Jone ay | Observateur Déshydratant | 2s ee | GOyee | alGeyEs Impuretés | Timmermans, P205 56°10° + 1 | 0°81249 + 3) 0°79574 | Pure mais perte | | | importante. of redistillé & plusieurs | 56-25° | 0°81286 | _— Produits de con- reprises sur P20? | densation 99 S0!Cu | 56°10° | 0-81375 — | Produits de con- | densation et eau ON) CaCl? 56°10° | 0°81370 — Eau | | oH CaO | 56:40° 0°81298 — Produits de con- densation et eau an simple fractionnement | 56:10° 0°81391 —— Eau 8. Young, idem. 56-40° — — idem. Perkin, !* CaCl et SO4Cu 55'8° + 2 — 0°79582 Pure et anhydre i} Squibb, ?? CaO et CaCl? ASEH 0°81261 | 0°79592 Traces d’eau Zander, ** CaCl? | 56°3° 0°81241 — Pure et aulydre | = Krugg et McElroy,*4) a l’ébullition sur CaCi? | 56°4° — 0°79764 Kau Thorpe,!° Fractionnement | 56°58° + 1 | 0°81858 — Trés impure Sapojnikow,!9 idem. | — 0°81378 — Kau | Crafts, ?7 — | ae = — Trés impure Regnault,” . _ |756°3° — — Eau J’ai réuni daus le tableau V les données numeriques concernant mon acide isobutyrique et celui d’autres auteurs; les produits de Kahlbaum, de Perkin, et le mien sont parfaitement concordants quant au point de congélation et a la densité; nos échelles de température au point d’ébullition ne sont pas comparables; l’échantillon de Faucon devait contenir des quantités notables d@un homologue, car son point de congélation est beaucoup trop bas; enfin Smirnoff a opéré sur une substance trés impure; son hypothese, d’apres laquelle la fraction dont la température critique de dissolution dans l’eau est de 15:7° serait plus pure que la fraction a température critique de dissolution 23°7°, est évidemment erronée, puisque la présence d’acide butyrique normal a pour effet d’abaisser la t. er. de D. dans l’eau ( —3° pour Lacide normal et + 26° pour l’acide iso), et de donner a la courbe de saturation l’allure asymétrique qu'il a observée, tandis que mon produit a une température critique de dissolution relativement trés élevée et suffisamment constante. 4 Squibb: Journ. of the Amer. Ch. Soc. 17, 187 (1895). 43 Zander: Liebig’s Ann. der Ch. 214, 138 (1882). 4 Krugg et MckKlroy: Journ. of Anal. and Applied Ch, 6, 187 (1893). 331 Tes en dessous de O°. qu La densité des TIMMERMANS “CLOGT) 199 ‘89 “UD “Ud “FZ “Yourtug 6, “(OLGT) OL “6T “OM9S aTITA “YO op 90 “sAGq ep “UUW : UoONTYA 5; (8681) SEF {9G NO “Ud “FWog : punurgzoyY o¢ *(auinsaqy) *(1061) 119 ‘8 “YO “Yd “FZ 2 T0pUR[PETMT 15 (6681) 9¢F *69 “UUP “pera “66ST “yorunTy ‘eseyT, : YOSAtET UOA of oGL-EL ce aa = HASTEN iets “WLapL * ‘uorjaety ,[ Wapt oGL-8G — — = oGEL & oF ST “WLapL pytonionsy 3g Young oli 008 — S1OA = = = “Wapt 9 s gr “Ones o8eGG = = = FF of -CST “Wwapt p sy LOPUL[POLL of PG = = = = sqUUOlp RI UOTYT[YSI e * op PUNTAIIOY a: rie = 1696-0 a = : * g2‘Olletg “5, — = 6066-0: Jar? — — = + + gy YOSATET woA — ~ = 86F96-0 1 F ol- FL — 0 6g EER = = 0866-0 _ © F of 8G WOU [SUCH 19 Ld Sea: pr ULILOCT == lin= = = I F ob-@ST UONVPSUOD 19 UONTITASI] | “ * ¢, wNeaTyLyy = = = = | ofE-FGT “ule eS ULOKGLS 010¢6-0 : Fer P oF:9G B 9G cok = 8086-0 ZF 61896-0 @ F oGh-FO1 aQUUOTORAG LOIVRTTNSI ‘supULe WL, veo aes UoHY[esu0H ep * I, F/G P °F/.0 P UOTTINGA PAL uorwogLnd ep epow SUNIL dp : “.68-0 = oh anbuiliqngosy apo Kv "A AVOIAY, 332 Scientific Proceedings, Royal Dublin Society. On voit que la séparation des acides gras lun de l’autre par distillation fractionnée est trés difficile a réussir parfaitement; c’est au point que Perkin a recommandé leur transformation préalable en éthers composés dont la température d’ébullition plus basse rend Ja distillation aisée; mais c'est 14 un reméde héroique qui entraine trop de pertes; au contraire, la congélation fractionnée serait 4 essayer, puisque ces acides ne donnent pas de solutions solides ]’un avec l’autre: les expériences de Kahlbaum et de Faucon dans cette direction sont trés encourageantes. 22. OComposés aromatiques et composés azotés—Le métaxylol provenait de la maison Schuchardt ; il a été soumis a des distillations et 4 des congélations fractionnées alternantes jusqu’a ce qu’iln’y eut plus amélioration du produit ; il contient cependant encore des traces d homologues. L’anisol a été deshydraté soit sur Na, soit sur P,O; (qui se colore en rose violacé) ; la pureté de l’échantillon ne me parait pas encore absolue. Le tableau No. VI. contient les données sur la pyridine. Mon échantillon est pratiquement identique a ceux de Louguinine, cle Zawidzki, et de Dunstan; il a été préparé a partir du produit synthétique “ Kahlbaum”’: le simple fractionnement de la pyridine impure ne permet pas d’enlever entiérement les traces (homologues (a—picoline—d 25/4: 0-941), qui abaissent la densité (Hartley); des traces d’humidité suffisent a faire baisser la température d’ébullition de quelques dixiémes de degré et ne sont pas séparables par distillation fractionnée ; la densité est alors trop élevée (Constam et White, Dunstan). Pour l’éthylamine, les déterminations de densité sont difficiles a cause de la volatilité du produit, d’ou lerreur anormalement ¢levée. 33 Q » fé des liquides en dessous de 0°. SU RMANS—La den . Ny TIMM! 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PROC, R,D.S,, VOL. XTMI., NO. XXV, SCIE 334 Scientific Proceedings, Royal Dublin Society. 23. La densité de la vapeur saturée ad O° ct en dessous.—Pour les douze corps dont j’ai étudié avec exactitude le coefficient de dilatation, la connais- sance de la densité de vapeur saturée a 0° et en dessous m’etait nécessaire pour déterminer l’allure réelle du diamétre rectiligne et aussi pour calculer le poids de vapeur qui surmontait le liquide dans les dilatometres. (Voir § 6.) Les composés dont le point d’ébullition est supérieur a 65° ont a 0° une tension de vapeur si faible que la densité de la vapeur saturée a cette température est négligeable (plus petit que 0™0001 gr. par em’). Pour le chloroforme et l’acétone j’ai calculé cette densité a partir de la tension de vapeur a 0° et en appliquant les lois des gaz parfaits. Voici les résultats obtenus :— Densités de vapeur a 0°. 0:00040 0:00022 Chloroforme, Acétone, Restent l’éther, le pentane, et l’isopentane, dont les densités de vapeur ont été déterminées et recalculées par Young,” jusqu’a 0°. Hn dessous de 0° il n’a fait d’observations que pour isopentane (jusqu’a — 380°; les valeurs a - 40° et - 50° ont été extrapolées). Les densités de vapeur du pentane et de l’éther en dessous de 0° ont été caleulées par comparaison avec celles de Visopentane (en gr. par cc.). | Le tableau No. VII contient les valeurs adoptées. Tanieau VII. 58 Young, Zeitschr, fiir Ph. Ch. 70, 620 (1910). t Tsopentane. Pentane. Ether. + 30 0:00327* 0°00245* 0:00268* + 20 0:00234* 0:00176 0-00187* + 10 0°00165* 000120 0:00126* 0 0°00109 0:00082 0:00083* — 10 0:00072 600063 0°00053 ) — 20 0°00046 0:00084 0:00034 | p extrapolé extrapolé — 30 0‘00028 0:00020 0:00020 — 40 0-00015 \ 0:00009 J 0-00009 J extrapolé — 50 0:00005 ) = Ea * Calculé par 8. Young. TimmermMans—La densité des lquides en dessous de 0°. 335 3° ParttE—CuHorx DE L’ ECHELLE DE TEMPERATURES: POINT DE CONGELATION DE 25 LIQUIDES ORGANIQUES. 24. Kehelle du thermoméetre a résistance de platine.—Pour déterminer les températures fondamentales de mon échelle, je disposais d’un thermométre adrésistance de platine et j’ai décrit antériewrement mon dispositif expérimental pour la mesure des résistances (1° partie, §§ 9 et 10); supposons done connue la résistance du thermométre (tableau VIII, colonne 2) observée dans une série de cryostats (bains de liquides purs maintenus a leur température de congélation), et cherchons a dantes. Pour atteindre ce but deux méthodes ont été proposées: la premiére due 4 Travers, () la seconde recommandée par Ostwald (“). Pour faire usage de la formule de Travers, nous devons connaitre la résistance du thermomeétre 4+100°,a 0°, et 4 une température connue, inférieure calculer quelles sont les températures correspon- a zéro, La résistance croit régulicrement quand la température s’éléve et la différence des résistances 4 + 100° et a 0° est ce qu’on appelle l’intervalle fondamental, dont le centiéme équivaut @ la variation moyenne de résistance par degré de température entre 0° et 100°. Quand on applique par extrapolation la valeur de l’intervalle fondamental ainsi déterminé au calcul des températures infériewres & 0°, Vexpérience montre que les temperatures obtenues sont toujours trop basses; il existe done entre la température vraie 7’ et la température mesurée au thermométre a résistance ¢, une différence D qui est fonction de la température. T=t+ D. Pour caleuler D, Travers a proposé la formule suivante :— t t D=d (30 Too -1) 100? d représente une constante qui vaut généralement 1:50 et qu’on peut déterminer dans chaque cas particulier en mesurant D a une température connue inférieure a 0°, par exemple au point d’ébullition de l’oxygéne liquide, J’ai fait usage de cette formule de correction pour évaluer les tempéra- tures en fonction des résistances ; les résultats de ces calculs sont consignés dans le tableau VIII, colonne 8. Travers n’a fourni 2 l’appui de sa formule que deux séries d’observations se rapportant a—78° et a—190°. Onnes,“ en multipliant les points de eomparaison, a en l’occasion de montrer que ce mode de correction donnait 52 Travers et Gwyer: Zeitschr. is Ph. Ch. 52, 446 (1905) et Proce. R. Soe. qh 528 (1905). 83 Ostwald Luther: Physiko-Chemische Messungen, 3¢ éd., 1910, p. 512. 64 Communications, ,., no. 95 (1906), 99 et 101 (1907). 3m 2 336 Scientific Proceedings, Royal Dublin Society. généralement des résultats exacts 4 + 0°1° jusqu’a la température de l’air liquide, pourvu que le platine employé pour la construction du thermométre fit suffisamment pur; aux environs de — 200°, le coefficient de température de la résistance décroit de moins en moins vite, et la formule de Travers n’est plus applicable. Or, le platine du thermométre n’est généralement pas pur: le passage dans la filiére a pour effet le dépdt sur le fil de métaux étrangers, ce qui diminue considérablement le coefficient de température de la résistance et reléve d’autant la région a partir de laquelle la formule de Travers devient inexacte. J’ai calculé pour toute une série de températures la résistance du platine pur d’Onnes (tableau VIII, colonne 4) et celle du platine impur de mon thermométre (colonne 2); pour rendre les résultats comparables, toutes les mesures ont été ramenées au cas d’un fil dont la résistance a 0° serait égale a lVunité. En comparant ces deux séries d’observations, on remarque que la différence des résistances est proportionnelle a la température, car, en retranchant de mes valeurs l’équivalent du terme 0°00028¢, on retrouve exactement les valeurs d’Onnes (colonne 6), sauf aux températures inférieures 4 — 125°, ot les anomalies de résistance de V’alliage commencent a se faire sentir; dans l’air liquide le thermométre a résistance fournit des valeurs trop basses de plus d’un degré, et une variation de valeur de la constante d ne conduit pas a de meilleurs résultats. On voit que la formule de Travers ne donne pas de bons résultats aux trés basses températures; dés lors, au lieu de s’efforcer de représenter les résultats par une formule encore plus compliquée, il devient préférable d’opérer par interpolation graphique, comme Ostwald le recommande, Les points de repére que cet auteur a choisis sont les suivants: Température de congélation du mercure — 38°8° (d’aprés Chappuis). Température de congélation du systéme CO, + alcool — 78°35° (d’aprés Regnault)®. Température d’ébullition de loxygéne liquide — 182-8 (d’aprés Onnes).* En me servant de cette méthode, j’ai obtenu pour les températures correspondant aux diverses résistances les valeurs indiquées dans la colonne 10; la concordance est bonne, sauf encore une fois aux températures trés basses; pour rendre les résultats comparables aux précédents, il est donc absolument nécessaire de choisir entre les points—78 et — 183, qui sont trop éloignés l'un de Vautre, au moins un repére supplémentaire, l’éther, par exemple, qui se congéle a —123°3°, 6° Regnault, Mém. Acad. 26, 339, 1862. — ®° IX. Onnes, Communications.,., no. 107, 1908. 337 urdes en dessous de 0°. aq La densité des 1 | | X co-gep — AGot SL = OL-9ET > 96-861 8¢-111 ¢8-F01 sas 06-76 — 68-8 — 86-81 > 6G-FL = 86-69 — Wi xg = 00-:cF% — 69-86 — 06-LE — LO-eg Lg-08 = 96-66 — GL-eL — 0-891 —. 0.861 — OF-9E1 — OF-9E1 — PP-9EL — Os-e21 — | 08-82 — Gu-8B1 — 09-111 ~ ¢¥-TTT — $9-T11 — ¢g-FOL~ | 0L-FOT- | 18-F0r - 02-46 -— | 09-46 — 09-46 = 0F-88. — | 08-88 — 68-88 — e.g! — | X¢e.g1 — 0¢-8L — GCP |) =8e-7) = 60-bL — A) he = | Gee = 09-7¢ — | Y9-"¢ — 99-69 — 00-6 — 06-GF — 10:97 = 09-82 — | x08-8¢ — 09-86 — 06-18 — OF-LE — Hiol = (Be = | WAGE = ae-ce — 09:08 — | 080g - #9-08 — 66-76 — | 06-66 — 76-06 — over - | eter - 01-81 — (Ke) = 03-9 — Glick) = 00 rc!) of comnrugop | Transg | S240 SEAS! adwiay, samqvagdura g, soanqvagdwiag, Il Or 6 SIAAVIT, sade p sainjzigduray, 8 0G + 08¢e-0 \ 0996-0 ( bC0F-0 =) ~ y * ‘attejuadosT SStF-0 | 0Z600-0 8L4F-0 | ggeo0-0 IL8F-0 27 TA ep aansopyp 806.0 | 120950 | 088-0 Ban sce > Gonpor ST ( L1¢¢-0 \ 1089-0 he ‘auoqava ap ainging * €61¢-0 | 60#00-0 F6L9-0 | 0800-0} ) 9809-0 eens (CNTR 6029-0 ( £129-0 ( GL¥9-0 Be ee i Ton om 9999-0 9999-0 f 6689-0 ~ + ey Aqn9,p eegQ0V $989-0 6989-0 | S80L-0 ‘ P - eur +2700 FE01-0 mvs FE0L-0 - rene { 1¥GL-0 - _ ‘atAqna.p ayeuordorg 91¥1-0 CL 0862-0 [ 8G91-0 7s + (Qu TOFOIOLYD, CZ8L-0 { 1682-0 { 1161-0 : : : ‘os - UL G0Z8-0 | 6028-0 | 8268-0 “+ + {fozuaqsoryO, 99¥8-0 ~ | 00600-0 i ¢98-0 | 1600-0 d £108-0 Se ey eee OTN OIO TY 8368-0 | 1298-0 | 1298-0 S50 oo GaaNy 1698-0 L 66¢8-0 ( 9698-0 + reuaAqia,p eanso[yQ 6818-0 f sgLs-0 ( 1lss0 | ° * * “ozueqmosg 1606-0 | 0606-0 | CC16.0 ‘QUOG.IV) ap aINLO[Goe.Ya J, ¢876-0 | 6600-0 ‘ ¥8F6-0 | 69800-0 4 1296-0 7 + * ferLyTmozueg 8616-0 | 1616.0 | anest) | & 2 2 Sarna 0000°T \ 0000-1 {0000-1 = aos eer 13) saamliiod | 4p SOUU() HY SUBULLAULULLT, S99UBISISAIT | Ip soude.p Ip saude,p uleg | SODURSISOYT SODUPRISISOY 9 g % € 6 T TILA Avoid 338 Scientific Proceedings, Royal Dublin Society. . En résumé, les échelles de températures fixées de cette maniére concordent & + 0°1° jusqu’a - 125°, mais au-dela elles divergent et un résultat absolument satisfaisant ne parait pouvoir étre obtenu que par la connaissance trés exacte d'un point aux environs de 150° sous 0°. L’échelle de températures que j'ai adoptée définitivement est donnée dans la derniére colonne du tableau VIII; elle me parait d’autant plus satisfaisante que, par l’intermédiaire des observations d’Onnes, elle est mise en relation, indirectement il est vrai, avec léchelle du thermometre a gaz. ? 25. Températures de congélation.— Une fois déterminée de la sorte, l’échelle des températures fondamentales en fonction de la résistance du thermomeétre, je possédais en méme temps la température de congélation des différentes substances qui me servaient de bains cryostatiques ; j’ai fait dans ces mémes bains mes observations dilatométriques : les dilatométres ainsi calibrés m’ont servi 4 mesurer la température de congélation des autres substances que j’examinais. J’opérais généralement dans un réservoir cryoscopique de Beckmann pourvu d’un agitateur et séparé par un bain d’air du réfrigérant extérieur (mélange carbonique ou air liquide). J’ai toujours eu soin d’éviter les corrections de tige émergeante en choisissant des dilatométres convenables pour la zone de températures a explorer.’ Hnfin j’ai répété certaines de ces observations au moyen d’un thermométire a mercure de Baudin donnant le 4~ de degré: cet instrument avait été construit en admettant que la température de congélation du mercure est de-38-80° (d’aprés Chappuis), alors que j’ai trouvé — 38°60°; de la un léger désaccord pour les températures inférieures a — 20°. Toutes les mesures faites dans ces conditions sont en bon accord avec celles faites au thermométre a résistance comme on le verra dans le tableau no. IX. On y a indique le nom du corps étudié, la température de congélation trouvée au thermométre a résistance et celle indiquée par l'appareil Beckmann ; pour ce dernier, je signale quel est le dilatométre ou le thermométre employe. Contrairement a l’assertion d’autres auteurs, tous les corps que j'ai étudiés, y compris, les pentanes, les éthers composés, et l’alcool méthylique cristallisent trés nettement sans donner de verre, et possédent un point de congélation bien marqué; seuls des corps moins purs comme le métaxylol ne fournissent que des indications plus aléatoires. emarquons enfin, que tous les corps étudiés se congélent avec diminution de volume. N.B.—Toutes mes mesures ont été faites 4 lair libre et s’entendent donc de liquides saturés d’air sous la pression normale; l’erreur qui en résulte ne parait pas devoir étre bien élevée. * Sur d’autres précautions 4 prendre dans l’usage des thermométres 4 liquides pour basses températures, voir mon article dans Bull. Soc. Chim. Belgique, 25, 305, 1911. TimmMrerMANs— La densité des liquides en dessous de 0°. Tas LEAU IX, Températures de Congélation. 339 ee ue | ee Thermomeétre employe Ly Pentane normal, — | 46 (a isopentane) — 130°8° — 130-8° Tsopentane, — 158°04° 46 (a isopentane) — 158°05° —158-05° Tolnol, — 94:50° 49 (& pentane) — 94-4° — 94°5° m-Xylol, (— 54°69°) | 27 (a pentane) — 53°6° — 53°6° Chloroforme, — 63:28° 37 (a acétate d’éthyle) — 63:2° = 63°3° Tétrachlorure de carbone, | — 22°96° Baudin (a mercure) — 22-96° — 22°95° Bromure d@’éthyle, . — 47 (a isopentane) — 119:0° — 119-0° Chlorure d’éthyléne, — 35°27° =_ | — — 35°3° Chlorure dallyle, — 136°40° 46 (4 isopentane) | — 136:4° — 136°4° Chlorbenzol — 45:00° | 29 (a pyridine) | = Agere — 45-0° Brombenzol, — 30°57° Baudin (& mercure ) | — 30°80° — 30°6° Sulfure de carbone, — 111°58° 49 (a pentane) — 111°6° — 111-6° Alcool méthylique, Sa ae = Ghare | = SmI Ether diéthylique : ii { 42 (a éther) — 116°35° —~ 116-2° 1. forme stable 37 (& isopentane) — 116: 13° 5 m1. forme instable, — 123°86° 47 (a isopentane) — 123°3° — 123°3° Méthylal, — 104-80° | 47 (a isopentane) = 104-7° — 104:8¢ Anisol, = 37:20° Baudin (a mercure) — 37°34° — Si22 Acétone, — 35 (a toluol) — 94°3° — 94:3° COE SP EHO a {39 aa Bae Agi) |S Fee | = oes OS see = ee He aa tluol) d’éthyle) S oe 5° = OS Acétate d’éthyle, = Bera — | = =. §3°4° Propionate d’éthy le, — 73:91° _ _ — 73°9° (2¢ échantillon = 74-29) Acétonitile, = |feochsseen | Sep | Benzonitrile, = 18-07" -- = ~ 131° Aniline, — 6:18° Baudin (a mercure) — = 6:2° EYER, a { 16 ti ae) z roe eee Mercure, — 38-62° Ga eee. = Be a eae 340 Scientific Proceclings, Royal Dublin Society. VTasiuau X.— Temperatures a ___Thermométres a Gaz : l Corps étudiés / || Timmermans Haase : ! | : Olszewski | Holborn Archibald Divers : 710 | 71 72 | 73 | Aniline, eRe eariate — 6:29 — | = ey | = ne Benzonitrile, . 0 , — 13:12 = = = as = Tétrachlorure de carbone, = 22-952 — | = —= | a a Brombenzol,. . . || — 30°6° =) 3h? == = | we = Chlorure d’éthyléne, —. — 33°3° — 42°0° | — = LES ay Anisol, . 6 ; = Suede <— 75° = no | sce ae Pyridine, i : : — 42°0° — = = fier == | Acétonitrile, . ¢ 3 — 44:9° — | = == ae = Chlorbenzol, . 6 : — 45:0° — 449° = = = — Acide isobutyrique, 0 — 47:0° — | = <= a = m-Xylol, .. a : — 53:62. || — — = ee Es Chloroforme, . i 9 = 63:32 — 62:0° | — — — 63°2° = Propionate d’éthyle, = 73:99 |i<— 76° = = ie By COz + alcool éthylique, . —_ — | = — 78-3° = — 78:23° CO2 + éther, dn , = see | = \) =) 78:2° = = 7eray - Aeeee COz + acétone, : ‘4 — 78:4° = | = = we) Se) Ethylamine, : 6 — | = a ee = tl | Acétate d’éthyle, . i 2) RECO Clie a) | = ae pcde ae Acétone, 5 9 - — 94:3° | —- = = — = | Toluol, eee ac = 94:5° | = | = — 102° — 97° — 99° = Alcool méthyiiqne, «| — 97°19 | = ST ee hc — | Methyl al ean a eee aeen04 82 on. ce Po. 3) Sulfure de carbone, ; — 111:6° | = | — 110° — 112°8° | — — | Ether (forme stable), . — 116:2° — — 117:4° — 117-6° — 117°6° — | | Bromure d’éthyle, : = 119:0% "| <= | — 125:9° = aes = Ether (forme instable), . — 123°3° | — a= — = = | Pentane normal, : — 130-8° | == = | = | == == | Chlorure d’allyle, b — 136:4° — | = | = = 2s Tsopentane, : Ales 158-06° — a as = oh CO TET a FD : Timmermans— La densité cles liquides en dessous de 0°. B41 de Congélation. \ ‘Thermométres Electriques | Thermométres & Liquides | | 23 "I. x I a oe Ladenburg | Carrara Guttmann Divers | Schneider | Guye a a | anes pacauyels "4 | "5 16 a 48 | mercu | ly ers at Bena spa | aurea 28 es. = 16780) fe 15-962) = G1 1) = Gng° (84) (69) | - (80) = = = = = Noe? — a — — a = = = = | = = 22-9°| —99:96°] — 22-6° (85) (69) | (86) — — = = = 380°5° | = = BoP7? |) SB — (86) | (68) _ = = = — 36:0° = =e kM ao se = _ _ — _ = BA = eM os | | f- 49-S° i} _ = ae = <— 100° = 2 =H Kk | Sp (93) _ — = — = Alea = = — 30:0° (94) — == = = = Ger) = = = 45-9° = (68) i mn Fe = <= GF 47-0? |<- 79° | (88) (95) = = — 548° = <— 80° — — — 54:0° = 57° (82) (68) = 63°02 _— — 62:2° —_— — — et — — _— | — 63°5° = = = 72:0° as ee at Beer te lt) | = = | = ely, = = = — 784°); — i (82) 90) | = | = = = = = = 1) = TOE (91) (96) = Be = = en es = = WP | (89) _ = PEP — = = §3:6°} — = BPP |) | (80) | = — 94:6° — — | | 76° | | (94) = ORF | = Gp = <— 100° =} ie = C8 (68) = 94:0° = 97:8° = = ee aS = = — 108-6° as aq fl) (228 = aes _ a | a os = WIG GP ||| = Wigen® - = = Se — (83) (92); | | | = = = |i = lappa — — = | = = = = 17? = = = — = i1Gale (82) | | | (90) = — 147-5° = a ae a ue = sel | e | SCIENT, PROG, R.D.S., VOL, XITM., NO. XXV. BF 342 Scientific Proceedings, Royal Dublin Society. 26. Comparaison avec les données dautres auteurs.—J’ai cru utile pour terminer ce qui concerne les températures de congélation de les comparer a celles d’autres auteurs (Tableau X). Dans un pareil travail on est immédiatement frappé des divergences énormes que l’on rencontre surtout au dela de 30° sous zéro. Les erreurs peuvent provenir de trois causes différentes: l’usage de produits impurs, l’emploi d’une méthode défectueuse ou d’un mauvais thermométre, et enfin le choix d’une échelle de températures inexacte. L’usage de produits impurs intervient pour beaucoup dans les déterminations erronnées de chimistes organiques (ex. Massol) et de purs physiciens (Wroblesky). a méthode de mesure choisie a généralement été convenable, sauf chez Haase, dont les déterminations ont été faites en observant la température de fusion des substances congelées dans des capillaires ce qui peut conduire a des erreurs de plusieurs degrés. Certains chimistes qui se servaient de thermométres 4 liquides ont oublié de tenir compte de la correction pour la tige émergeante qui peut étre trés élevée; d’autres, tels que Ladenburg et Kruegel, paraissent ne pas avoir su se servir du thermométre a gaz. Notes pu Tasirau X. 68) Mentschutkin: Journ. de Ch. Ph. 9, 538 (1911). 9) T'ammann: Kristallisieren und Schmelzen, pp. 222 et 228 (1903). Haase: Ber. d. deutsch. Ch. G. 26, 1052. (1893). 1) Olszewski: Wied. Ann. 20, 253 (1883), et Monatsh. f. Ch. 5, 127 (1884). 2) Holborn et Wien: Wied. Ann. 59, 226 (1896), et Drude’s Ann. 6, 242 (1901). Archibald et McIntosh: J. Am. Ch. Soc. 26, 505 (1904). Ladenburg et Kruegel: Berichte 32, 1818 (1899), et 33, 637 (1900). 5) Carrara et Coppadoro: Gazzetta Ch. It. 35 I, 329 (1903). 6) Guttmann: J. Ch. Soc. of L. 87, 1037 (1905), et J. Am. Ch. Soc. 29, 345 (1907). 7) Schneider: Z. f. Ph. Ch. 19, 155 (1896), et 22, 225 (1902). 8) Tsakalotos et Guye: Journal de Ch. Ph. 8, 340 (1910). 9) Steele, McIntosh et Archibald: Z. f. Ph. Ch. 56, 226 (1905); et Ph. Trans, 205 A, 99 (1905). 0) J. K. Wood et J. D. Scott: J. of the Ch. Soc. London, 97, 1575 (1910). 1) Regnault: Ann. de Ch. et de Ph., III, 26, 247 (1849). 2) M. A. Hunter: J. of. Ph. Ch. 10, 330 (1906). 3) H. E. de Leeuw: Z. f. Ph. Ch. 77, 285 (1911). 4 5 6 7 8 9 0 = wm CO ) Ampola: Gazzetta Ch. It. 27 I, 35 (1895). ) E. Amagat: Compt. R. 105, 165 (1887). ) Bugarski: Z. £. Ph. Ch. 71, 710 (1910). Zawidski: Chem. Zeit. 30, 299 (1906). ) Kahlbaum: Z. f. Ph. Ch. 26, 577 et 603 (1898). ) Pickering: J. Ch. Soc. Lond. 63 I, 141-et 11, 998 (1898). 90) J. Homfray: Z. f. Ph. Ch. 74, 154 (1910). (91) Villard et Jarry: C. R. Acad. Se. 120, 1262 et 1413 (1895). (92) D. McIntosh: J. Am. Ch. Soe. 33, 71 (1911). (93) Kahlenberg et Brewer: J. of Ph. Ch, 12, 285 (1908). (94) P, Walden: Z. f. Ph. Ch. 55, 216 (1906), et 73, 260 (1910). (95) Massol: Bull. Soc. Ch. Paris, III, 18, 758 (1895). (96) Faraday: Ph. Trans. I, 16 (1846). meme ee ee eee ee TN ee ce oe ae eo ee MAIMBDDDaBOoOwm ont AIAN Ws ssa OS TrmMermMans—La densité des liquides en dessous de 0°. 345 Mais la cause d’erreur la plus répandue est le choix de points de repéres fautifs pour le calibrage du thermométre. Beaucoup d’auteurs se sont servis du point de congélation de l’éther, et, comme ils ignoraient son dimorphisme, ont été conduits 4 des valeurs tout & fait mauvaises variant de- 112° (T'sakalotos) &-128:1° (Homfray); toutes les valeurs de T'sakalotos, de Ladenburg, et de Carrara sont faussées par ladoption de la valeur — 113°. Beaucoup de mesures fournissent des valeurs aux environs de-117°, ce qui concorde avec la température de congélation que j’ai mesurée (~116-2°), mais a coté de cette forme stable qu’on obtient surtout par congélation brusque, j’en ai observé une tout autre, se congélant a— 123°3°, forme que Hunter et Miss Homfray devaient sans doute avoir déja rencontrée ; on ne Vobtient que si le refroidissement est suffisamment lent; cette forme est moins stable que la premiére, puisque la température de la liqueur partiellement congelée 4-—123:3° s’éléve brusquement a -116-2°, si lon y introduit quelques cristaux de la forme stable. Ein tenant compte de ces quelques observations on pourra remarquer que Vaccord avec les recherches les plus récentes et les mieux faites (Gutmann, Smits, &c.) est malgré tout assez satisfaisant. Pour d’autres renseignements voir le travail cité no. 67. 4° Partite.—Donn&ES NUMERIQUES. 27. Explications des tableaux de données numériques.—Les résultats des mesures de densités sont réunis dans les trois paragraphes suivants :— § 28. Chlorbenzol, acétonitrile, acide isobutyrique, pyridine, et chloroforme. (Tableaux XI a XV.) § 29. Acétate d’éthyle, acétone, alcool méthylique et toluol. (Tableaux XVI a XIX.) § 30. Ether, pentane normal et isopentane. (Tableaux XX a XXII.) La disposition des tableaux est la suivante :— le colonne: T. de l’expérience. 2° colonne: numéro du dilatométre employé. 3° colonne: Densités observées, toutes corrections faites. (Par rapport a l’eau 4 son maximum de densité.) R. Quand Vexpérience a été refaite a plusieurs reprises, la densite indiquée est la moyenne de toutes les valeurs observées; l’écart le plus considérable qui ait été constaté entre la valeur moyenne et les valeurs observées est indiqué en unités de la 5° décimale dans la méme colonne aprés le signe +. BRr2 344 Scientific Proceedings, Royal Dublin Society. L’écart entre la valeur moyenne et les valeurs expérimentales obtenues soit au moyen d’un méme dilatométre, soit au moyen de dilatométres différents, n’atteint presque jamais le ;>455°; il n’y a d’exception que pour les points suivants :— — 23° dilatomeétre No. 26 (acétate d’éthyle) ; — 45° dilatom. No. 32 a (acétone) ; — 37° dilatom. No. 32 B (éther) ; — 116° dilatom. No. 50 8B (pentane normal) ; — 28° dilatom. No. 50 a (isopentane) ; — 95° dilatom. No. 47 a (isopentane). (6 mesures sur 250.) 4° colonne: La densité calculée au moyen de la formule placée en téte du tableau correspondant. 5° colonne: La différence exprimée en unités de la 5° décimale entre la densité observée et la densité calculée. R. Quand une densité observée a servi pour le calcul des constantes de la igrmule et que l’accord entre la densité observée et la densité calculée est done absolu, j’ai mis le signe ~ dans la 5° colonne. La formule dont j’ai fait usage pour représenter les variations de densités avec la température est du type général :— NOLO She TES OP J oc At = densité a 7°. ° = densité a 0°. t = températures sur l’échelle centigrade. a—B—y— = constantes a calculer. Dans ces formules, j’ai généralement pris suffisamment de termes dans le second membre pour pouvoir calculer la densité 4 755° prés au moins; pour y arriver, il suffit d’employer une formule: 4 une constante, pour l’acétonitrile et le chloroforme ; 4 deux constantes pour la plupart des autres corps; trois constantes pour l’alecool méthylique. De cette maniére la concordance entre les valeurs calculées et observées est tout a fait satisfaisante pour le chlorbenzol, l’dcétonitrile, Vacide isobutyrique, la pyridine, le chloroforme, Vacétate d’éthyle, et le toluol; cela est d’autant plus remarquable si l’on considére que je n’ai fait aucun choix dans les données numériques que je communique, mais que je donne toutes les valeurs de densités que j’ai observées. k. La forte déviation constatée pour le chloroforme a—- 63°, me parait due 4 l’erreur d’une expérience que je nai pu répéter ; il en est de méme pour le point ~ 95° de l’acétone et peut-étre pour le point — 35° du pentane normal. Pour les cing autres corps, la concordance est moins bonne; un examen attentif permet d’attribuer les anomalies a trois ordres de causes différentes : (a) Les formules ne s‘appliquent que par extrapolation au point + 15° de aleool méthylique, et aux températures les plus basses pour léther et les deux pentanes; cette constatation montre une fois de plus le danger d'une extrapolation trop étendue pour les expériences d’une grande précision. TimmermMans—La densité des liquides en dessous de 0°. TABLEAU XI.—Chlorbenzol. Az = Av — 0°0010606¢ + 000000071747 = ae A nedts Densité observée Densité calculée O-C 0° = 1°12795 | 1:12795 = | GaP 7 113452 1°13453 = il = 1c 7 1:14201 + 0 1-14193 += 8 — 22-95° 19 1715253 1:15268 =15 | — 30:6° 19 1:16103 1:16103 = = SareP 19 1:16630 1°16625 + 6 — 45:0° 19 117712 1°17713 = TABLEAU XII.—Acétonitrile. At = Ao — 0:0010609¢ Tf No (6) C O-¢ + 18-2° 2a 0-78417 0°78419 —- 2 0° = 0-80350 080350 = — 62° 2a 0-81013 0:81009 + 4 — 131° 2a 0°81724 0°81739 =15 — 22°95° 216 0°82774 + 0 0°82785 = iil — 30°6° 16 0°83592 + 2 0°83597 = 6 == 216 083593 = = ¢ | — 35-8° 16 0-84074 084096 = 22 | —87:2° 16 0-84288 + 7 0°84297 = 9 | = 450° 16 0°85124 085124 = TABLEAU XIII.— Acide isobutyrique. At = Ao — 0-0009849¢ + 0:000001036¢2 | Te) | Nos ) Cc O-¢ + 17:5° By 095060 0:95066 2o56 moe 5 0°96820 0°96829 = = 6:2° 5 0-97450 + 5 0:97433 +17 = igi’ 5 0-98141 0:98125 + 16 — 2295° 5 0:99136 + 0 099136 == = 17a 0:99116 - = 0 — 30°6° 5 099930 099928 oe — 36°3° lla 1:00430 1:00433 = 8 — 45°0° 17a 1:01462 1:01462 = ee 345 546 Scientific Proceedings, Royal Dublin Society. TaBLEAU XIV.—Pyridine. At = Ao -- 0°0009873¢ + 0:00000066S8¢" mp No. ) 0 | O=G 4 18:2° 1 0°98499 0-98505 - 6 0° 1 1:00304 1-00304 us _ 62° 1 100926 1:00917 a) 13°1° i 1-01621 101606 4116) | 99-959 228 1:02606 102606 Se | — 30:6° 228 1-03385 1-03385 0 | — 35°3° 228 1:03894 103869 +25 — 37:2° 22 1:04059 1-04069 = 10 WHEE ~ 45:0° 22y 1:04882 + 0 104882 a TABLEAU XV.—Chloroforme. Ar = Ay — 0:00185524 T No. 0) C 0-¢ 4 150° 8 1:49849 1:49854 SNS 0° a 1752637 1°52637 ee = 9 8 153811 4 1 153787 424 Sha 8 1°55071 + 11 1°55067 a A — 2295 180 1°56888 + 12 1-56895 6 ~ 30-6 18a 1°58325 +0 — 1-58314 +11 = Bee! Sa 1°59220 + 0 1°59186 + 34 a 148 1:59214 p + 28 — 37°22 148 159511 + 0 1°59538 - 27 — 450° lta 1-60984 + 10 160985 = = 148 1:60998 — A +18 == 18 1:60982 = = 8 — 53-6 148 162581 1°62581 ae = 18 162578 a =8 — 63°3° 318 1:64312 (?) 164380 — 68 (2) Timmermans—TLa densité des liquides en dessous de O°. TABLEAU XVI,— OFY oF-68 — or r GO0LL-0 Gi = 16692-0 0 F #8692-0 $5 — is ¢ ¥ LYCI8-6 Aty = OF — 10918-0 1918-0 gee ofS FL — i= a GF 9ET9L-0 )) B= SLE18-0 (4) 00¢18-0 OEP 086-81 — 68 — Ne $Z19L-0 i 8 = L9T9L-0 0 = FE19L-0 1 us 2508-0 aby = 6. + sss 9 ¥ 60¢2.0 og — st FEF08-0. dee = ¢ + $80¢1-0 0 = 880¢2-0 63 — e 0F OFFO8-0. vee = cg — 6IEFL-0 GF G8FL-0 6% = 69F08-0 PFROS-0 gE 08-89 — = 1298-0 10981-0 = 5 FF GSP6L-O 9g = = sf O881L-0 | cI + BSF6L-0 19% 61-0 ge 09-89 — fos 06812-0 SS8IL-0 9-0 9) 6) oN L DO ) (0) mee dE de nee GI GI 00°F — 09 08 — 096-66 — ol EL Siege 206 0°67335 067323 +12 = 137-20 208 0-67493 067501 - 8 — 45:0° 4ly 0°68238 068233 + 5 =159;60 4ly 0°69035 0°69035 = = 63:3° 41, 069894 0769932 = 38 = 38B 0:69888 » sd = CoS 388 0-70884 070935 = — 83-4° 47a 0-71715 071764 49 — 388 0-71722 a — 49 = (945° 47a 0°72785 (°) 0°72763 4c OG = 387 072760 ‘ = 8 = 104-852 478 0°73672 + 4 073685 =. 3 = 111-6° 47B 0-74281 + 0 074281 - — 116-2° 47B 0-74691 0-74687 ney = 123:3° 478 0-75320 + 5 0-75306 +14 = 46 0°75323 s alia — 136°5° AG) ee OGG 0°76450 +211 = [EO 46 0-78714 + 0 0-78283 + 431 TimmermAns—La densité des liquides en dessous de 0°. 303 1 1 0° Partie: Discussion DES RESULTATS AU POINT DE VUE THEORIQUE, § 31. Coefficient de dilatation.—Connaissant la densité de mes liquides a différentes températures, j’ai pu en calculer le volume spécifique et déterminer leur coefficient de dilatation. Pour représenter les variations du volume spécifique avec la température, je me suis servi généralement de formules quadratiques : Vi=Vo+at+e7... Ces formules suffisaient pour obtenir une approximation de 5,))5°, sauf en ce quiconcerne l’alcool méthylique ot un terme supplémentaire était néces- saire; pour l’acide isobutyrique, la pyridine, et le chloroforme, une formule linéaire suffisait ; pour l’éther et les deux pentanes une formule quadratique ne donnait qu'une approximation du milliéme, mais l’adjonction d'un terme supplémentaire ne fournissait guére de résultat plus avantageux. J’ai réuni les constantes de ces diverses formules dans les tableaux suivants :— (a) Tableau XXIII: variation de la densité avec la température. TABLEAU XXIII. ; = | Substance examinée | Densité a 0°/4° a x 107 | B x 10° y x 101 Chlorbenzol, ; 112795 — 10606 | A Fy as Acétonitrile, é 0°80350 — 10609 | — = Acide isobutyrique, | 0:96820 — 9849 | + 1036 —= Pyridine, : =| 1:00304 — 9873 + 668 = Chloroforme, . 3 | 1-52637 — 18552 — — Acétate d’éthyle, . | 092450 | _ 11987 | — 3265 | a= Acétone, . .| 081248 | 11142 | — 315 | ae Toluol, 2 a 0788448 = 9159 + 868 — Alcool méthylique, | 0°81015 — 10041 — 1802 | — 1687 there, w iar | 0°73627 — 11190 = 603 = Pentane normal, . 0764537 — 9467 — 450 | oo Isopentane, . : | 0°63943 — 9719 = 408 | —_ 304 Scientific Proceedings, Royal Dublin Society. (0) Tableau XXIV: variation du volume spécifique avec la température. TABLEAU XXIV. Substance examinée Nolumerneciique a x 107 B x 10° y x 10" Chlorbenzole | 088754 4 8846-5 + 884 a Acétonitrile, . 5 124456 + 16111 + 1333 — Acide isobutyrique, 1:08284 + 10490 — _— Pyridine, . . | — 0:99697 + 9671 2 = - Chloroforme, . | 0°65515 + 7475 — — Acétate d’éthyle, . | 1:08167 + 13921 + 1825 = Acétone, A 6 123080 + 16735 + 2290 _— Toluol, 6 S | 1:18061 + 11807 + 820 _ Alcool méthylique, 128434 + 15190 + 3989 + 2258 Ether, 6 3h 135821 + 20397 + 3302 —_ Pentane normal, . | 1:54950 + 22367 + 3344 _ Isopentane, .. oth 1:56389 + 23384 + 3474 = (c) Tableau XXYV : coefficient de dilatation réel. TasLeau XXYV. Substance examinée Volume a 0° ax 107 B x 109 y x 10 Chlorbenzol, 5 1:00000 + 9967 + 996 _— Acétonitrile, : 1 + 12142 +1071 — Acide isobutyrique, 3 + 10157 = = Pyridine, 6 5 x + 9700 —- | — Chloroforme, 3 m9 + 11410 — — Acétate d’éthyle, . 0 + 12869 + 1687 _ NBR, 2 x + 13597 aie | A Toluol, eats 5 + 10443 + 7255 | a Alcool méthylique, 30 + 12306 + 3232 | + 1829 Ether, : . ” + 15018 + 2424 = Pentane normal, . : ” + 14429 + 2158 _ Isopentane, . 5 ” + 14952 + 2221 | —— ~ Timmermans— La densité des liquides en dessous de 0°. 359 Dans le Tableau X XVI j’ai mis en présence le coefficient de dilatation moyen de mes liquides tel que d’autres auteurs l’ont mesuré entre 0° et — 1° et tel que je l’ai obtenu entre 0° et — 6°. TasLteau XXVI. Be Coefficient de dilatation moyen x 107 réel a froid Coefficient de dilati ution @apre és 27 ee Autres Awan 7 y o te) Substance examinée x 10 entre 0° et — #° | (entre 0° et—6-2°)| (entre 6° et — 1) Chlorbenzol, 5 9520 | — 465° 11269 — Acétonitrile, : 12462 — 465° 13193 12100 (100) Acide isobutyrique, | 1017 — 45° 10410 9739 (101) Pyridine, . . 9700 = 45° 10030 = Chloroforme, . : 11410 — §3°6° 12286 11025 (102) P 92 : ; 12555 (103) Acétate d’éthyle, . 11464 — 83°4° 12987 { 12716 (104) Acétone, : 3 12041 — 83-4° 13681 13202 (104) Toluol, 0 9 9765 — 94°5° 10228 10262 (106) Paitin f ( 11514 (104) Alcool methylique, 10808 — 94-5° 11734 \ 11840 (107) ( 16109 (107) Ether, . P 123804 — 111°6° 14546 14768 (104) (16170 (97) Pentane normal, . 12026 — 111°6° 14001 14615 (98) 14632 (98) Isopentane, . D 12471 — 111°6° 16089 15890 (99) 15035 (110) Dans le Tableau XX VII, je compare le coefficient de dilatation apparent moyen de mon toluol et de celui étudié par Chappuis et celui de mes deux pentanes avec le coefficient de dilatation du pentane commercial étudié par (97) Tammann et Hirschberg, Z. f. Ph. Ch., 13, 548 (1894). (98) Thorpe et Jones, J. of the Ch. Soc., 68, 278 (1893). (99) Bartoli et Stracciati, Atti delia R. A. Lincei, 19, 643 (1883/4). (100) Kopp. Lieb. Ann., 98, 367 (1856). (101) Zander. Lieb. Asia, , 224, 56 (1884). (102) Is. Pierre, Ann. de Ch. et de Ph. 11, 38, 199 (1851). (108) Is. Pierre, ibid., mr, 19, 193 (1847). (104) Kopp. Pogg. Ann., 72, 1 et 223 (1847). (105) Zander, Lieb. Ann., 214, 138 (1882). (106) Louguinine, Ann. He Ch. et de Ph., rv, 11, ae (1867). (107) Is. Pierre, Ann. de Ch. et de Ph., 11, 15, 324 (1845). 306 Scientific Proceedings, Royal Dublin Society. Baudin. Pour faire ces caleuls, j’ai négligé la contraction de volume de mes dilatométres, et j’ai done admis implicitement que le coefficient de dilatation de mes récipients en verre dJéna était identique a celui des appareils en verre frangais dur qui ont servi 4 Chappuis!” et & Baudin?” (dont les recherches avaient un but purement thermométrique). Si Ton tient compte de cette cause d’erreur, de la différence des échantillons des liquides employés et de la concordance seulement approximative de nos échelles de températures, on peut considérer le résultat de cette comparaison comme satisfaisant. VasLeau XX VII. Coefficients de dilatation moyen apparent Auteurs Toluol entre 0° et — 95° | Pentane normal | entre 0° et — 138° entre 0° ef — 135° Isopentane Timmermans . Chappuis, | Baudin, 0-000952 0-000975 0-001109 | 0-00/108* 0-001195 * Le pentane de Baudin a une densité de 0-622 a 14°/4° — Le pentane normal a la méme température : 14°/4° : 0°63200 — L’isopentane 9 w 1 0°62553 Enfin, dans le Tableau XXVIII, je compare mes nombres sur les pentaues a ceux de Hofimann et Rothe." Tasreau XXVIII. Coefficients de dilatation réels x 107 Auteurs et Corps | a — 3° | a— 120° Pentane commercial (H. et R.), 14966 | 12503 Tsopentane (T.), 15089 10231 Pentane normal (T.), 14001 9638 108 Chappuis, Archives de Genéve, iii, 28, 285, 1892. 103 Baudin, Comptes Rendus, 133, 1207, 1901. 110 F. Hoffmann et Rothe. Zeit. f. Instrumentenkunde Paris. . 27, 266, 1907. TimmerMANS—La densité des liguides en dessous de-0°. B57 Ces données sont les seules que j’ai pu découvrir dans la littérature concernant la dilatation des liquides en dessous de 0°; encore sont-elles difficilement comparables aux miennes, puisqu’elles ont été déterminées dans un but purement thermométrique et en faisant usage de substances dont la composition chimique est mal établie. J’espére que les déterminations de densités que j’ai faites sur le toluol pourront étre utiles au point de vue thermométrique, car cette substance est sans contre-dit la plus convenable quand il ne s’agit pas de dépasser une température de - 90°. 32. Autres formules de dilatation.—Outre les formules ot la variation de volume ou de densité d’un liquide est exprimée par un développement en séries, on en a proposé beaucoup d’autres qui ont des bases théoriques plus ou moins sérieuses. Mais comme ces formules ne représentent généralement les faits que trés approximativement, je n’ai pas cru utile de m’y arréter, et je me contenterai de me servir de mes données numériques pour critiquer deux travaux trés récents. (A) Ter Gazarian’™ a énoneé cette régle empirique : A des températures également éloignées de leur température critique respective, les membres d’une série homologue possédent des densités presque égales ; la différence des densités observée dans ces conditions est égale a la différence de la densité critique des corps considérés augmentée d’un terme de correction trés petit et proportionnel a l’éloignement de la température critique. Cette régle peut étre représentée par la formule suivante: Di=De+Ar+at, ou D' et D* représentent Ja densité cherchée et la densité de la substance type considérées 4 des températures également éloignées de leur température eritique respective; A la différence de leur densité critique respective ; ¢ la différence entre la température examinée et la température critique de la substance étudiée; et a une constante. Ter Gazarian a vérifié sa formule 4 partir de données de 8. Young, et croit pouvoir admettre que a est nul dans le cas de substances isoméres telles que le pentane normal et Visopentane. Mais en poursuivant la comparaison en dessous de 0° au moyen de mes expériences (‘J’ableau XXIX), on doit reconnaitre que méme dans ce cas a a une valeur positive excessivement petite, il est vrai (a = 0-000012). Le résultat des caleuls faits dans ces conditions est indiqué dans le Tableau XXX; dans la derniére colonne se trouve la différence entre la valeur de la densité observée et de la densité calculée, toutes corrections faites, et l’on voit que ces différences se répartissent réguliérement le long de l’échelle de température et dépassent les erreurs d’expérience. ul J. de Ch. Ph. 6, 492, 1908; et 7, 273, 1909. SCIENT, PROC. R.D.S., VOL. XIJI., NO. XXYV. 3H aety. Soe am yal Dubl OY wo ape ings Proceed ific Scient. 308 e) Sqqn) BRO 06 GPT — 09-981 — (é) $2 892 gen oO8l = | pe: — 1g *TT¢L PGPL 00-121 — of LIL — 9¢ ToL C6eh o6-PLY — o8-FOL - 11+ 188¢ F98e 00¢ oF 66 56 8o8L 9g08L 06-601 — of 76 — LI+ 69L9 oeLg 209 oF 69 0g 0962 "6062 08-36 = = PG + gege oege 04 oF 6 6 PLIL COIL 09:88 = 9% + OFge FICE 008 oF 68 8 SLOL 0goL 09:3L — Co) = Lo+ SIRS ogee oF 66 Ey 3669 "869 00:89 = 09:8 = 0% + SLZG 8cze oF 601 568 3169 S189 oF FE — 00-SF — 0% + OFIE 0z¢ oF GIL 88 9689 8619 99h — Hel S 8% + 166% 896F oF 661 18 E89 PSL9 lie = 08-98 — 96 + IESE 008F oF 681 Lg 9119 6819 00:0F — 09:08 — 9% + GhOF 919F of GFI ifs BOLO 8999 oF GR = AME = zg + CPEP SLFF oF-6G1 206 1099 89149 KG = ale = 9% + 908F OSTF oF 691 1g 899 Z1¢9 oon = to) = 81 + F168 9688 oF 611 89g, 89 £egr9 oF6 = 00 FI + S6FE FSFE oF 681 88% 6o£9 “0¢¢9 OB — Ap 00-81 + 9 + PIE sels oF F61 29% + 8089-0 6129-0 avo 4p cB + 4 Lest. FE8G- oF 961 0% + SFEG-0 8086-0 ot L61 (1q-"dq) 01] "Geta | dye -dq WL “dy, (1a -°4q) ;01 Vd dy, supUtewmMty, sarde (qT sunox *g saidv.q "XIXX Avaravy, Timmurmans—La densité des liquides en dessous de 0°. 359 TABLEAU XXX. Ti. ’ See Différence | Différence ; Tp. | =Tp. — 9-4° Dp. a Tp. Di. a Ti. cues ni One A calc.—A obs. | : p- i. p- + 197:2° + 187-8° 0°2323 | 0°2343 + 0°0020 + 0:0020 — +119-4° | 4110°0° | 0-120 | 0-140 | +0-0029 | +0-0020 | + 0-0009 + 49:4° + 650:0° | 0°d864 | 0°5881 + 0°0036 + 0°0017 | + 0°0019 + 18:2 + §8:8° 0°62795 | 0°6308 + 0:00415 + 0°00285 eras 0°0013 — 23:0° — 32°4° 0:6668 0°6702 + 0:00465 + 0:0034 + 0°00125 — 63:°3° — 72°6° 0°7030 070738 + 0:0051 + 0°00435 | + 0°00075 — 104°8° — 114-2° 0°7395 07451 + 0°00565 + 0°0056 | —_ — 136°5° — 145:9° 0°76825 0°77555 + 0:0060 + 0:0073 — 070013 — 263°6° — 273°0° 0°86365 0°87435 + 0:0076 + 0°0107 | — 0:0031 Voila done une formule empirique qui parait susceptible de fournir a partir de deux données expérimentales (densités a la température critique et a une autre température suffisamment basse) et par comparaison avec un corps type, les densités d’une substance quelconque non polymérisée a toutes les températures avec une approximation d’au moins ;},°; mais elle est cependant incapable de représenter les résultats avec une exactitude comparable a celle des expériences méme. (B) Duclaux™ a proposé de représenter la dilatation de l’eau aux environs de son maximum de densité par une formule relativement simple, puisque le développement en série ne dépasse pas le terme en 2’, mais qui contient un * terme exponentiel 47 o4 & et n sont des constantes et 7’ la température absolue. Cette formule se comporte excessivement bien en ce qui concerne l’eau, et son auteur espérait qu'elle pourrait également rendre des services dans l'étude d’autres corps polymérisés; j’ai donc essayé de l’appliquer a l’alcool méthylique. M. le Professeur Mineur, auquel je suis heureux de pouvoir témoigner tous mes remerciements, a bien voulu se charger des calculs délicats que nécessite la détermination des constantes de l’équation a partir de mes expériences: Il résulte de ses recherches qu’une formule qui en dehors du terme exponentiel ne contient qu’un terme en ¢ est incapable de représenter les résultats, 4 moins de donner an une valeur négative qui lui enléve tout sens physique. En ajoutant un terme en ?° le résultat est meilleur, mais la formule contient alors quatre constantes, ce qui la rend inférieure 4 la formule courante qui n’en contient que trois, pour arriver a une approximation tout aussi élevée. u2 J, de-Ch. Ph., 10, 73, 1972. 3H2 360 Scientific Proceedings, Royal Dublin Society. 33. La Régle du Diamétre Reetiligne.—La regle du diametre rectiligne découverte par Cailletet et Mathias et souvent vérifi¢ée expérimentalement, peut s’énoncer comme suit :—Les moyennes des densités d’un liquide et de sa vapeur saturée sont fonction linéaire de la température. 8S. Young™*a démontré depuis que ce diamétre étudié dans un trés grand espace de température n’est plus strictement une droite mais une courbe excessivement aplatie. Le sens de la courbure reste le méme a toute température pour un corps donné, mais varie d’une substance a autre a peu prés paralléle- ment a la valeur du rapport: a ; en effet le sens de la cour- ensite theorique bure change au moment ot la valeur de ce rapport est de 3°78, et pour le © pentane normal ot le rapport précédent a cette valeur, le diamétre rectiligne serait une droite rigoureuse entre le point critique et 0°. L’un des buts les plus importants que je me suis proposé dans la présente recherche est l’examen du diamétre rectiligne de quelques corps types jusqu’a leur point de congélation situé fort bas sous zéro. Dans la plupart des cas, j'ai opéré sur des substances dont la densité de vapeur saturée est négligeable a 0° et en dessous par rapport a la densité du liquide; ce n’est que pour V’éther et les deux pentanes, qu'il faut tenir compte de la densité de vapeur saturée pour le caleul du diamétre rectiligne, et les valeurs choisies pour cela ont été indiquées au § 23. J’ai commencé par yérifier si les valeurs du diamétre obtenues dans mes expériences coincidaient avec celles que l’on peut calculer par extrapolation a partir des formules de Young. Le résultat de cette comparaison se trouve résumé dans le tableau XXXI: pour le chlorbenzol, lacétate d’éthyle, et méme l’alcool méthylique, l'accord est satisfaisant jusqu’aux températures les plus basses (concordance minima, =4,° prés). Pour l’éther et les deux pentanes, l’extrapolation s’étend sur une trés grande région de température ; on observe des déviations systématiques qui vont en grandissant quand on s'approche du point de congélation et qui peuvent atteindre le =4,°. Enfin, jai comparé aussi les valeurs que j’ai déterminées pour la densité de Vacétonitrile a celles que l’on peut calculer a partir d'une formule du diamétre indiquée par ler Gazarian™; ici il n’y a plus aucune concordance, ce qui montre bien que pour l’acétonitrile le diamétre doit étre assez fortement courbé; je nai pu représenter lensemble des résultats expérimentaux de Ter Gazarian (entre + 270° et + 212°34°) et des miens (entre 0° et — 45°) que par une formule cubique que voici: d = 0.840540 — 0°0°49591T + 0-0715287" — 0-0°22347°. la forte courbure du diamétre dans ce cas est bien en accord avec le degré de polymérisation élevée des nitriles. 113 Ph. Mag. 50, 291, 1900. 114 J. de Ch. Ph., 4, 156, 1906. 361 des en dessous de 0°. aur des Tai té Timmermans — La densi | O8LL — | 9866 — | SPGPP-0 | ZILSP-O of SCOLP-0 GLIOF-0 | a) OT aatnoyvo | aDatosqo. ae | : aot x aaqnoyeo | apaaosqo | * | Senseo ni eS eta CUeu Be (Ta acs CUS le erat ramus Ue lepers i (ees | UVELUZBY =O], SAAB pp O[LLUOJQ0V if i Te scte ¥ ea ee i WAS 86F6E-0 19868-0 = fay => a os | = of 0-891 | | | S20 = PESLE-0 199L8-0 PG — 6008-0 99LLE-0 PPL — SIPESP-0 =| G69GEF-0 of E61 Sunox “9 EL = LEGGE-0 O98dE-0 | gol — POL9E-0 | GFODE-0 (iS = OOELP0 19G1P-0 of 88 Fl bios ice: 9BTPE-0 COLPE-0 66 COEPE-0 N9EPE+0 PL + 09G68-0 PLObE-0 00 GF yar 0Z0Z8-0 960GE-0 Ors 0686-0 OT8SE-0 ees PG896-0 9806-0 000. oT X ol X o0L X saenyn sda Hi Vv, te Vv wt tt v 0 LA i decoys fal at a €— Va a d = Voy C ae ? aunzuadosy | [BULLION OURZWO TONNE {| : 7 | 901 + GOPPP-O SOOPP-0 te} = S6LTY-0 OLT1¢-0 co = a | of 68) = SUNOK “9s | 68 + PIGSP-0 EG9GP-0 86 — LIGSP-0 6O888P-0 Ch + GI88¢-0 LO88¢-0 of F Sit 00G0F-0 S0¢0P-0 Os OPGIP-0 SCG9F-0 Chon 00F9S-0 8689¢-0 ol oT X oO X 01 X aneyn i bt V/ SNe i Vv eee He Vv "4 ny i+ Vg d a tL vq qd ar fie vq Ok (TL | anbip ‘ounjuedosy 6F6E0-0 OGSF0-0 | 089¢0-0 6690-0 6120-0 €GF80-0 | S&F60-0 9601-0 9691T-0 TEGZI-0 | “Tetutou ouvzueg ae G16F0-0 8eZ¢0-0 6L¢90-0 | O1E40-0 FGPS80-0 TP ¥F60-0 6EC0T-0 S89TI-0 | OS6GT-0) | © > REM TaT | | 06-0 ¥G-0 8<-0 G&-0 | 96-0 OF-0 FF-0 8F-0 GE-0 | 9¢-0 | SOUNp OL TL | | Sunox *g saadv (7 5 = = = | 0&2z-0 6686-0 6066-0 6666-0 | lee ae SaprayTu0j99V - Fah f018-0 6LTE-0 G9GE-0 = = | = oe ~ ‘ozuaq.toryo = = 9008-0 SLOE-0 | ecle-0 LEGE-0 FOFE-0 | a x ‘at Aq39,p alvjza0y" 8608-0 I0TE-0 GLIE-0 GhGE-0 | GESe-0 | GOFE-0 GSFE-0 | P8Cb-€ 789-0 | — ‘auvjuodosy 9166-0 8F08-0 FI1E-0 cste-0 | 1928-0 | L¢e8-0 €Gre-0 | SISE-0 €19&-0 ‘Teuou ou) zed es 6608-0 1606-0 LOTE-0 | €F68-0 » GGEE-0 SOFe-0 | GOes-0 £09€-0 S ; TIA i | | ce i 86-0 GE-0 9¢-0 0F-0 | FF-0 SF-0 GS-0 9¢-0 09-0 SOIT Waals “squppuodsa.lloo s7n99 sap WI—' AXXX AVAIAVY, - 370 Scientific Proceedings, Royal Dublin Society. Il me reste a faire remarquer qu’avec tous les modes de calcul, Visopentane — se montre singuliérement aberrant, ce qui m’a engage a recalculer les données obtenues par la méthode de Mme. K. Meyer, et qui sont généralement si concordantes, en adoptant comme correction du volume + 00066 au lieu de + 0°0166; les résultats sont donnés dans le tableau No. XXXYV sous le titre: isopentane — a. VI. Concrusions. Les principaux résultats auxquels je suis arrivé dans ce travail sont les suivants :— A.—Auwu point de vue expérimental. 1, La mise au point d’une méthode qui permet la mesure de la densité des liquides en dessous de zéro avec une approximation de;>}75°- 2. La fixation au ~1;° de degré prés d’une série de repéres de température entre 0° et — 160°. 3. La détermination de quelques constantes physiques de 25 liquides organiques a l'état pur. 4. La mesure au 757° prés du coefficient de dilatation sous 0° de 12 liquides organiques. B.—Aw point de vue théorique. 5. La régle du diamétre rectiligne ne se vérifie jamais d’une maniére absolue pourvu que les déterminations s’étendent suffisamment loin de la température critique; exemple: le diamétre du pentane normal, rectiligne entre la température critique (197°) et 0° se courbe nettement entre 0° et le point de congélation (- 130°). 6. On ne connait aucun liquide (sauf Peau et V’hélium) méme parmi les corps les plus notoirement polymérisés, qui présente un maximum de densité. 7. La loi des états correspondants modifiée par Mme. K. Meyer se veérifie jusqu’aux plus basses températures. 8. Le rapport de la densité maxima a la densité critique est égal au rapport de la densité critique a la densité théorique. J’ai l’intention de continuer les présentes recherches en examinant de nouveaux corps) dont l'étude puisse jeter quelque lumiére sur les différents problémes théoriques envisagés au cours de ce travail, et de reprendre avec encore plus d’exactitude l’examen des liquides qui peuvent servir 4 la construction de thermométres de précision pour les basses températures. ‘Timmermans—La densité des liquides en dessous de 0°. 371 En terminant mon exposé j’ai la chance et l’honneur d’avoir 4 remercier un grand nombre de personnalités et. d’institutions savantes. J’ai commencé mon travail 4 Dublin il y a six ans sous la direction de M. le Professeur S. Young, Je ne saurais assez lui témoigner ma reconnais- sance pour les conseils et les exemples qu’il n’a cessé de me prodiguer. Jai Vhonneur de remercier également le Board de Trinity College, Dublin, dont la généreuse intervention a seule permis l’achat des appareils cofiteux qui ont été mis & ma disposition. Enfin, je suis heureux de pouvoir dire ma gratitude a la Royal Dublin Society et a son secrétaire si prévenant, Mr. Moss, qui ont libéralement placé & ma disposition les grandes quantités d’air liquide dont j’ai eu besoin. J’ai terminé mes expériences a l'Université de Bruxelles, ot j’ai pu me procurer l’air liquide nécessaire au moyen de la machine dont Mr. Solvay a généreusement fait cadeau aux laboratoires. Je saisis l’oceasion pour remercier également MM. les Professeurs Chavanne, Verschaffelt, et Wuyts, de lintérét quils n’ont cessé de prendre a mes recherches. Dusuin Ev BRuxe..es, le I* Mars, 1912. [VLUI. Appunvtcs. 372 Scientific Proceedings, Royal Dublin Society. VII. APPENDICE. Au cours de la publication du présent travail, j’ai pris connaissance d’une recherche de Fr. Korber’! ayant le méme objet. Je crois utile d’en comparer ci-dessous les résultats aux miens. Les détails fournis par Korber au sujet de son mode opératoire montrent qu'il ne pouvait guére dépasser une exactitude du ae En effet l’auteur déterminait le volume apparent des liquides étudiés, a diverses températures au cours du réchauffement lent du bain cryostatique, ce qui conduit foreément a des inégalités considérables de température entre le bain, le thermométre, et le dilatometre. De plus Korber ne me parait pas avoir pris suffisamment de soin pour pouvoir répondre de la pureté de ses échantillons; les constantes physiques des quatre liquides que nous avons étudiés tous les deux sont mises en regard dans le tableau XXXVI. Enfin la comparaison de nos températures de congélation pour l’acétone et le sulfure de carbone montre que nos échelles different déja de pres de 5° a - 100°; les valeurs de Korber sont d’ailleurs beaucoup plus basses que celles de tous les autres observateurs (voir a ce sujet le tableau X); il faut en conclure, me semble-t-il, que le thermométre a pentane dont Korber s’est servi, bien qu'il ait été vérifié par le Reichsanstalt, ne peut étre considéré comme suflisamment exact. TABLEAU XXXVI. T. d ébullition. T. de congélation. Densité & 0°/4°. Substance. Korber. as Kéorber. sis Korber. dt, Ether, . 5 B | 34°6° 34°60° — —116°2° 0°7356 0°73627 Alcool Méthyligue, . || 64-8—65-0° | 64-70° a — 97-12 || 0-3108 | 0-81017 Acétone, . d - | 56°2—56-3° 56°10° —99-0° — 94°3° 0°8140 0°81249 Sulfure de Carbone, || 46-2° 46°25° —115:7° | —111-6° 1-2918 1-29272 \ Les données expérimentales de Kérber sont peu nombreuses; j'ai réuni dans le tablean XXXVII nos valeurs respectives pour le volume spécifique sous 0° de l’acétone, de l’éther, et de l’aleool méthylique ; les divergences e atteignent méme le ani ce qui s’explique quand on songe aux causes d’erreur que je viens de signaler. 121 Annalen der Physik, IV° série, 37, 1014-1912, et Nachrichten, Gottingen, 1911. Timmermans—La densité des liquides en dessous de 0°. 308 TABLEAU XXX VII. Volumes spécifiques a — t° quand le volume spécifique a 0° = 1:0000. : Ether Alcool Méthylique | Acétone (lag Kener mee =a | icy bere cDes KeaT | Kérber K.-T. | x 10,000 |, x 10,000 || x 10,000 | | 0° | 1-0000 | 1-0000| —- 10000 | 10000, — | 1-0000| 1:0000) — = 80° || 0-9585 | 0-9569| +16 || 0-9670/ 0-9655| +15 | 0-9618 | 0-9612| + 6 — 50° || 0-9327 | 0-9307 | +20 |] 0-9456 | 0-9445| +11 || 0-9381 | 0-9367| +14 | | — 80° || 0-8970 | 0-8962] + 8 || 0-9140| 0-9199) +11 | 0-9043 | 0-9032 | 411 | x rgge Wee = = 0:9036 | 0:9020 | +4 16 | = ae = | — 110° | 0°8643 | 0-8643 0 tte pa Be = age ae | Par contre, Korber a eu Vheureuse idée de représenter ses résultats par des formules ott les températures sont comptées a partirdu zéro absolu; ce genre de formules fournit directement le volume spécifique A — 273° et les divers termes du développement en série, ne font sentir leur influence qu’au fur et a mesure que la température s’éléve, ce qui répond bien a Vallure générale des phénoménes de dilatation. J’ai cru utile de recalculer mes courbes de densité en faisant usage de formules analogues; les constantes obtenues sont réunies dans le tableau XX XVIII. TABLEAU XXXVIII. A, = Ao — aT — BT? — yT3. Substance. Ao a B OY | Isopentane, . .| 0°88010 + 0:000°8063 + 0°000:000:2757 = Pentane normal, .| 0°87620 +0 000-7609 | + 0-000-000-3118 — Ether, . 5 F 1°00298 + 0°000°S482 | + 0-000-000-4716 — Yoluol, . 5 5 |} LONE 7 + 0-001°0614 + 0°000-000-2478 — Alcool méthylique, .| 1-29946 + 0:003:8800 — 0°000°012°4172 | + 0:000°000-0174738 | Acétone, . n .| 1°09289 + 0:000:9398 + 0:000°000 3200 _— Acétate d’éthyle, .| 1-22741 + 0:001:0204 + 0:000:000°3266 -- SCIENT. PROC. R.D.S., VOL, XIII., NO. XXV. 3K 374 Scientific Proceedings, Royal Dublin Society. Les valeurs ainsi obtenues pour la densité au 0° absolu concordent fort bien avec celles qui j’ai caleulées par d’autres formules (voir le tableau XX XIII); cela ne peut que confirmer l’exactitude de la loi que j’ai indiquée sur la valeur du rapport de la densité critique a la densité maxima. Guidé par des considérations théoriques que ‘Tammann’” a récemment développées, Korber montre que le volume spécifique des liquides au zéro absolu est toujours notablement plus grand que la valeur limite obtenue par extrapolation du volume spécifique aux pressions les plus élevées; le tableau XXXIX montre que mes données numériques confirment cette conclusion pour Vacétone et pour l’éther, mais qu’elle est en défaut pour l’aleool méthy- lique; je ne pense pas que ce désaccord résulte seulement du choix de ma formule de dilatation, mais qwil est réel, puisque la valeur que j’ai trouvée obéit a la loi sur le rapport de la densité critique a la densité maxima; en tous cas, il nous invite a étre tres prudent dans les conclusions a tirer @extrapolations aussi étendues. TABLEAU XX XIX. ‘p= oo T= 0,p=1 | Substance ! Tammann | Korber Timmermans Ether, . : 0-694 0°751 0°734 Acétone, Pas 0-701 0-747 0-743 | | Alcool méthylique, . 0-722 0-729 0-623 12) Nachrichten, Gottingen, 1911. “ae bo 10. 11. 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Ivish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamiwm, Williamson). By T. Jounson, D.s¢., F.L.s. (Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Groraz H. Preruysrmes, B.SC., PH.D. (March, 1911.) 1s. : Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witu1am Brown, B.so. (April 15, 1911). 1s. . A Thermo-Electric Methed of Cryoscopy. By Henry H. Dixon, sc.D., F.z.s. (April 20, 1911). 1s.’ . 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(Plates XXV.-XXXI.) (September 30,1912.) 2s. Recherches Expérimentales sur la Densité des Liquides en dessous de 0°. Par Jean Timmermans. (October 18, 1912.) 3s. DUBLIN: PRINTED AT THE UNIVERSITY PRLSS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 26. | NOVEMBER, 1912. STEADY AND TURBULENT MOTION IN GASES. BY JOHN J. DOWLING, M.A., LECTURER IN PHYSICS, UNIVERSITY COLLEGE, DUBLIN. (PLATES XXXII. and XXXII.) vA Rs - { We € fj ~~ TAIN {Authors alone are responsible for all opinions a iheirCommunications.] 3 /, Ser ; Ma DUBLIN : PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. Price One Shilling and Sixpence. Roval Dublin Society, a OO a FOUNDED, A.D. 1781. INCORPORATED, 1749. OES EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until, examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Lilustrations in a complete form, and ready for transmission of the Iditor. hee | XXVI. SYEADY AND TURBULENT MOTION IN GASES. By JOHN J. DOWLING, M.A., Lecturer in Physics, University College, Dublin. Prates XXXII. anp XXXIII. [Read Jun 25; published Novemner 16, 1912.] Parr I. Introduction. OsporNE REYNOLDs,! experimenting with water, showed that at a certain so-called “critical” velocity the motion of a liquid through a tube ceased to be a linear flow, and turbulent motion then set in. His results are usually expressed in the form— i= 1090 » Rite (1) pa where V. = the critical velocity, » = the coefficient of viscosity of the fluid, p = the density, a = the radius of the tube. He also gave certain theoretical reasons for his results. His general results were confirmed by later workers. Reynolds’ method of experimenting was to allow water to flow through a glass tube, and to observe the behaviour of a thread of coloured water introduced by means of a fine delivery tube placed along the axis of the larger tube, near one end. At the critical velocity the turbulence manifested itself by dissipating the even thread of colour. He worked also on another method, and examined how the volume of water delivered by a pipe several feet long depended on the head of pressure causing the flow. At first the resistance was proportional to the velocity; but after the critical point was passed the resistance soon varied nearly as the 1°72 power of the velocity. he point where the first condition ceased gave the critical velocity. 1! Reynolds, (Phil. Trans. Roy. Soe., yol. clxxiv, 1883). SCIENT. PROC, R.D.S., VOL. XIII., NO, XXYI. BL 376 Serentific Proceedings, Royal Dublin Society. These experiments were confirmed by somewhat different methods by Barnes and Coker.! They also found that it was possible to maintain linear flow at speeds much above the lowest critical velocity, provided that the conditions were ‘steady.’ If the water in the supply reservoir were allowed time to become perfectly steady, and if the tube were very uniform, straight-line flow persisted much beyond the point found in other circumstances. The motion would then be unstable. Some investigations have been made on the flow of air in pipes. Almost all that have a bearing on the subject of the present paper are referred to in a paper by Gibson,? on the resistance to the flow of air through a pipe. The object of the paper was not to determine the critical velocity, but it is possible to estimate from the curves given that for a tube of diameter ‘0104 feet, the critical velocity would be about 3846 feet per second, the pressure being about 16-7 pounds per square inch. Consequently the critical velocity for the tube in question is < 346 x 30°35 or 1050 cms. per second. The diameter (¢d) is ‘0104 x 30°5 or 317 cms. From Reynolds’ formula the product V,xd should be independent of the size of the tube. In this case Yo 8 @ = O38 5 6 (A) where we have not allowed for the variation of density from the average atmospheric density. More recently in an investigation of the value of the Pitot constant, Fry and Tyndall,? using a tube about 2 inches in diameter (5 ems.), found indications that stream-line motion gave way to turbulence somewhere below a velocity of 76 cms. per second. They did not attempt to determine the exact critical point. Here the product, V,x d, wouldbe +76x5 or $380... (B) The comparatively good agreement of these two estimated critical velocities with Reynolds’ law is remarkable, considering the widely different diameters of the tubes. It seems interesting, therefore, to pursue the problem further. Possibly the reason why the problem has not been hitherto attacked is its peculiar nature. To work with tubes of wide bore requires the measurement of large volumes of air and of small-pressure slopes. ‘The flow of air can be measured readily enough by some form of air meter; ! Barnes and Coker, Phil. Trans., Roy. Soc., vol. Ixxiv, 1904. * Gibson, Phil. Mag., vol. xvii (1909). ’ Fry and Tyndall, Phil. Mag., vol. xxi, 1911, Dowiinc—Steady and Turbulent Motion in Gases. B77 but the pressure-differences are of a very small order, unless, indeed, tubes of an abnormal length are employed. For example, Riedler and Gutermuth! experimented with pipes upwards of 10,000 to 50,000 feet long, and about 1 foot in diameter. ‘They had pressures of upwards of twenty pounds to the square inch. ‘They, however, obtained only a few numbers— mostly referring to velocities above the critical. Other experimenters used tubes down to one-eighth of an inch bore, in which case the length could be cut down to between 30 and 100 feet, still having pressures of some pounds per square inch. These experiments were performed at different times, and all with a view to solving the problem of the resistance to the flow of air through pipes. The experimenters were not specially concerned with the problem we are now considering. To verify the applicability of Reynolds’ formula to the case of gaseous flow, through tubes of widely different diameters, by methods involving pressure measurements, would present great difficulties. Another method was therefore adopted. Parr II. Principle of the method employed. It will be, perhaps, well to notice in what turbulent motion consists. When a certain mean velocity (the “ critical ”’ velocity) is reached, the fluid flowing in a pipe ceases to follow stream-lines. This condition of affairs manifests itself in various ways. For example, the pressure-difference required to maintain a certain velocity in a fluid above the critical point is much greater in proportion to that required below that point. We may notice that probably the turbulence sets in at the centre of the tube at first, and gradually spreads itself over the whole cross-section. ‘The net result of the action is that a fluid particle on the average will follow a longer path during turbulent motion in travelling between any two points of a tube than in covering the same distance in “‘stream-line” conditions. For our purpose this is the important point to keep in view. Now a gas that has been made electrically conducting by the in- fluence of a radioactive substance will gradually lose its conducting power, if removed from the vicinity of the ionising agent. This gradual loss of conductivity is due to the ions in the gas becoming neutralised in one or other of the following manners. (1) Ions of opposite charges may recombine. (2) Ions will diffuse to the walls of the containing vessel: 1 Gibson, Joc. cit. Bi 378 Scientific Proceedings, Royal Dublin Society. this will be important if the vessel is small. (3) Ions may collect molecules to Earth. ™~ Electrometer & Fig- 1. or dust-particles, forming what are known as large ions. This loss of conductivity of an ionised gas is made use of in the method of experimenting. Fig. 1 shows the general arrangement of tlie apparatus. A tube AB, usually of glass, fits into a larger metallic tube BC, from which another exit tube C leads to (1) an apparatus for measuring the volume of air (if required); and (2) to an ap- paratus (e.g. electric fan or gasometer) for drawing the air through. It isin AB that the flow of air is to be studied. The vessel BC is insulated and connected to the negative pole of a battery (D) of some two hundred volts. The positive pole of the battery is earthed. ‘Through an insulating plug (#) in the side of BC awire E passes out; this is joined to one pair of quadrants of a Dolezalek electrometer (F’), and to one side of a variable condenser (K). The other electrometer quadrants and the other side of the condenser are, of course, earthed. The key Z allows of the wire # and its connexions being earthed when required. ‘The radioactive substance (radium bromide) is placed at the end A of the tube; and its rays are screened from the rest of the tube by a lead block placed as shown. On air being drawn through the tube in the direction ABO, it is rendered highly conducting on passing the radium at A; butit gradually loses this conductivity as it moves down the tube away from A. On arriving in the chamber BC—the ionisation chamber—all the small negative ions, and perhaps a few of the large ions, are driven into the wire E, conveying a charge thereto. This charge is a measure of the ionisation of the air on -reaching B, and is measured by the rate of motion of the needle of the electrometer. The ionisation is thus expressed as so many divisions on the electrometer scale per minute. When turbulent motion setsin the elements of the flowing gas commence to follow sinuous paths, so that a certain Dow iinc—Steady and Turbulent Motion in Gases. 379 amount of “mixing” takes place. The air-particles will frequently be brought near the sides of the tube. We should expect this to aid the processes which destroy the conductivity. If we plot a curve showing the variation of residual electrical conductivity at B, with the rate of flow of air through the tube, we find that the con- ductivity at first increases “smoothly,’ as we should expect, with the velocity—but at a certain velocity there is a well-pronounced discontinuity. After this occurs, the curve may continue to show an increase of conductivity with velocity, as before, or, in some cases, a drop, as explained later. In what follows, instead of the volumes flowing per second through a tube, we shall speak of the mean velocity of the gas. If V denotes this mean velocity, and if » isthe volume passing per second through a tube of radius a, obviously we have 5 Vea 2): (2) Wl Also if Vinar is the maximum velocity (on the axis) for stream-line flow, Vines a VA PAR Delle Verification of law connecting the Critical Velocity with the Tube Diameter. The first experiment, made principally with a view to verifying the suitability of the method, was carried out as follows :— The tube AB (of glass, 75 cms. long, and 1°6 cms. internal diameter) was connected through BC, as described, to a gas meter, and an electrically driven fan was utilized to draw air through the system ABC and the meter. The end of the tube AB was situated just at the point A, and the air was ionised as it entered the open end. Variations in the velocity of the air were obtained by altering the speed of the fan-motor ; and the rates of flow were calculated from the quantity of air registered by the gas meter in a minute. The mean velocities of the air, plotted against the ionisation measured, are shown in curve 1, Plate XXXIL, the electrometer readings being taken with the capacity J = -01 microfarad. A decided discontinuity occurs at a mean velocity of 232 ems. per second (corresponding to ‘97 cubic feet per minute). The break is extremely well marked, and was, beyond doubt, not in any way due to the action of the gas meter, which was well within its range of working. The mean diameter being 1°6 cms., the product Fae d= DOD 2 1B AAs ee (C) and is in good agreement with the values (4; B) already referred to. This agreement may be taken as an indirect proof of the validity 380 Serentific Proceedings, Royal Dublin Society. of assuming that the discontinuity is due in fact to turbulence setting in ; but at the time the experiment was carried out, the writer was unaware of Gibson’s results, and it consequently appeared all the more advisable to examine whether the discontinuity might not be due to some ‘end-effect,” the air being ionised before entering the tube at A. A further experiment was accordingly carried out with the tube AB prolonged beyond A, by a stiff paper tube, tightly fitting in, and of very nearly the same diameter. The air in this case was not ionised until it had settled, more or less, into its state of flow down the tube. The fact that the discontinuity was again obtained at the same velocity was taken to indicate that it resulted from the supposed cause. To Second Gasometer Using this form of apparatus, it was not possible to work over a large range of velocities, because of the limitations imposed by the gas meter. This was capable of passing a maximum of only about two cubic feet per minute, and was found to be unable to register at all at velocities much lower than one-eighth of that amount. However, as this experiment had shown the possibilities of the method, a new arrangement of apparatus was adopted. Dow iine—Steady and Turbulent Motion in Gases. 381 A. large gasometer was available, which was capable of holding about twenty cubic feet. (Fig. 2.) The drum V was suspended by a thin wire rope Vf, passing over pulleys in a wooden scaffold, and carrying a counter- weight W. A centimetre scale was attached to the wire Y and served to record the vertical movements of the gas-container V. A wire Z was stretched tightly across, as shown, and served as a mark behind which the scale Y moved. ‘he rate of movement was calculated from the time taken for a known number of divisions on Y to pass Z Two methods were available for altering this rate. One was by altering the weights W, the other by varying the aperture of the tap 7. Let D be the diameter of the drum JV, and d that of the tube AB (fig. 1), used in the experiment. Also, let ¢ be the time in seconds for the drum V to rise (or fall) 7 centimetres. The mean velocity of the air in the tube AB will then be bs i eso geo: (3) One difficulty only presented itself in working with this gasometer. ‘The displacement of water by the walls of V altered appreciably the effective driving-weight. This was, however, overcome quite easily; for it only occurred to a troublesome extent when working with small blasts. The method then adopted was to ‘‘throttle” the blast by turning 7’, almost “ off” and adding a considerable excess to W. Another possibility may be referred to. The air in V will necessarily be at a different pressure than the atmosphere. Usually, the air was being drawn in ; so that the pressure in V was below the atmospheric pressure. We will consider the most extreme case possible in practice, where the weights W were somewhat short of 100 kilogrammes. The diameter of V was 84 cms., so that its area was about 5500 sq. ems. Neglecting the weight of V, which was considerable, the pressure-difference between the air in V and the atmosphere was less than 20,000 dynes per square centimetre, or only two per cent. less than the atmospheric. Thus in this extreme case, never really attained in practice, an error of less than two per cent. would result from the calculation of V by the formula (8) above. The cock Z’ was connected by wide rubber tubing to the tube C of the ionisation chamber BC, used in the first experiment. ‘The various tubes were inserted at B in tight-fitting corks. Glass tubing, in ordinary stock-lengths, selected as being straight and of as uniform diameter as possible, were used. Their length varied between 120 and 160 cms. In most of these experiments two lengths of tubing were employed, which were joined together by a tight- fitting paper tube slipped inside, the joints being made air-tight by covering 382 Scientific Proceedings, Royal Dublin Society. them outside with ‘“‘ Plastacene.” The radium was placed so that its rays penetrated this paper tube between the ends of the glass tubes. ‘Thus the radium produced a strong ionisation due principally to 6 radiation. The fig. 1 represents this arrangement, the paper tube being at A, represented by dotted lines. In the case of the narrowest tubes (1:1 cms. diameter), the ionisation would have been very small at B, and the quantity of air passing into the gasometer would also have been rather too small to measure accurately. Consequently two tubes were used, both of the same diameter, each being in two lengths, and joined together with paper tubes as before. This pair of tubes was placed so that the radium affected each equally, and they entered BC through two holes in a cork, one at either side of the electrode L. The double tube delivered twice the quantity of air, and also gave twice the ionisation current. It was assumed, of course, that similar conditions obtained in each tube. It was found that the largest velocities required for tubes 5:03 ems. in diameter were just obtainable by the gasometer, the whole drum V becoming filled in about a minute. In order to work with larger tubes, the gasometer was out of the question, and another arrangement was adopted. The method then employed was to draw the air through the system ABC by means of a fan. A small series-wound electric motor was used to drive the fan; and a large range of speeds was obtainable by using a variable resistance in the motor circuit. ‘lo measure the velocity of the air an air meter was fitted at the end (C) of the chamber BC. The air meter was the ordinary fan-type used for measuring air-currents and was first calibrated over a large part of its range by means oi the gasometer. As it was feared that the fan might have possibly produced some irregularities in the flow, a few experiments were made with a fine gauze screen placed between the ionisation chamber and the air-meter. ‘lus noticeably retarded the flow; but the discontinuity in the experimental curve occurred for the same mean velocity of the air. From this it was concluded that the effects noticed were due to turbulence of the ordinary kind setting in, and were not due in any way to the action of the fan. When using these arrangements it was occasionally found difficult to obtain a smooth curve. This was thought to be due to draughts in the laboratory (a very large room, 30 feet by 90 feet, and 40 feet high), where the experiments were being carried out. It was generally found, indeed, possible to obtain very ‘‘ good” numbers on a calm day—and one when the room was unoccupied. The numbers were then usually quite steady, and produced smooth curves like the majority of those shown. Subsequently, for work with carbon dioxide gas, the gas was transferred from one gasometer, DowLtine Steady and Turbulent Motion in Gases. 383 through the tube, to another. In these experiments, it was noticed that, the conditions were much steadier, which was probably due to the fact that the interior of the tube was completely protected from outside influences. Those of the former curves with air, which did not appear satisfactory, were accordingly repeated with the double gasometer arrangement. Such curves are indicated below by the title “two gasometers.’ The method of working in this case will be dealt with more fully in a later part of the paper. An examination of the curves (Nos. 1 to 15, Plates XXXII. and XX XTII.) shows us that in general for each ¢wbe there are two “ discontinuities ” on the curve. There are four instances, however, where this is not the case. Curve No. 1 refers to the experiment first carried out and already described. A few numbers only were taken, and these were mostly in the vicinity of the ordinary “‘ turbulence” discontinuity. Curve No. 5, Plate XXXII. (for 3-cm. tube), shows only one discontinuity; while Nos. 10 and 13, Plate XX XIII. (for 7-4 em. and 1:9 em. copper tubes), also show only one. We will later consider the significance of the second discontinuity on the other curves, and for the present confine our attention to the turbulence effect. One remark may be made with regard to the form of the curve immediately after a discontinuity. In many cases the curve simply continues sloping upward, but at a rate different from before. In other eases, however, there is a sudden drop, followed usually by an increase. This occurs with the narrower tubes. Just before the discontinuity the curve is in these cases becoming more and more horizontal, indicating that, with the high velocity then used, the greater part of the ions formed by the radium are being carried right down to B. When turbulence sets in, fewer ions are left in the gas on its arrival at the electrode, and consequently a falling off occurs in the electrometer readings. The following table (Table I.) collects the results for the turbulence effect. The table includes only one number for each tube. In most cases, however, several independent experiments were made on each separate tube; but, on the whole, these results agreed well amongst themselves. It seems unnecessary to give more than a single result for each size of tube (especially as the degree of accuracy attained would seldom appear to be more than five per cent.). The tube bores were measured with calipers across two perpendicular diameters at each end. ‘This method was accurate enough, considering that the tubes were mostly of rather wide bore and fairly uniform. The temperatures are those given by a thermometer in the air near the apparatus. ‘The pressures were taken from a barograph record. The viscosities were calculated by Sutherland’s formula (Kaye and Laby’s tables). The density was calculated from the pressure and temperature. SCIENT, PROC. R.D.S., VOL. XII., NO, XXVI, 3M Scientific Proceedings, Royal Dublin Society. 384 Column 8 in the table gives the product of the critical mean velocity and the tube diameter. Il Or 6 8 L 9 ¢ v g 3S I -uaddog €1 OZ1E StF €Z100- 111000- 8-66 roi 986 6-1 fs10}9 OS) OT, “S8t[9 31 O19 Gog GZ 100- ¢11000- 1-0€ 01 OST 60-3 “19}9WOSey) 2UC sraddosy Or 0686 OLE 0Z100- 911000- 8-6 ZI 0¢ ia ‘LOJOULILY puy uy “SSB 6 093 L@e GG100- 911000- F-6 “1 co) 20-6 ‘layewosty 9UuC “sup b 008% LEE FG 100- 111000: 6-62 él 98 8-8 a 409) 9 O1G% 698 ZG100- | 4L1000- G66 || PL LIL 1-€ ‘S10 9WOSUH) OMT, “SSUID) g 086% 698 €3100- 911000- 8-63 at art 0-8 nt an “SsU[D) +? 006@ 6G GG100- ¢11000- G66 Oe |) < Meu 8-3 ea in “SSULD) g 000 06 GGL00- 111000- 1-6 él 9G LI “1a}aWLOSv BUC) “SST [H) I 019 ILE ¥Z100- 911000- 08 GI é |. ae 9-1 ‘IoJWSeH) PUL UBT PO) | “9e8/*swuO Uo) I eee oe = Sa |) DEA “Apisuaq aan ‘aanssaig | “dwg, ace ee | “poyyey ‘(Qy) ‘[ @1avy, Reynolds’ formula can be written in the form (4) ress1on The exp For water AK has the value 2180. where A is a constant, Dow iine—Steady and Turbulent Motion in Gases. 385 ne has been calculated for each curve, and the result is given in column 9 of the table. With two exceptions the numbers lie close together. ‘lhe two exceptions are for curves No. 3 and No. 13. No. 3 curve represents the results for the narrowest tubes, and, as we shall see, there are reasons for believing that this number might very well be too low. The conditions in the tube in the case of No. 18 are also different. This was a copper tube, thirteen feet long, and very straight and uniform, and there was no joining throughout its whole length. It will be as well to consider here the possible effect that a constriction in the tube would have on the results. Let us consider the tube 1:1 cms. diameter. It is very probable that at best the paper tube was narrower by a millimetre (indeed, it might very well be more different). If V is the mean velocity in the . 2 glass tube, the velocity in the paper one would be v= (=) V. Now the critical velocity will be reached in the narrowest part first. The condition fulfilled by the critical velocity V, is that V.x d = constant, but v= (+) V and the ratio of the diameters being only 1: 1:1, the product »xd for the narrow part will be reached when V x D for the wide glass tube is still only i of its value for the critical velocity. That is equivalent to saying that the velocity is =: of the critical velocity, or 10 per cent. short of the critical. If turbulence sets in in the paper tube, its effects will be probably identical with those produced by turbulence in the glass tube, and consequently the electrometer readings will indicate the passing of the critical point when the velocity in the glass tube is still 10 per cent. short of its critical value. If the joining tube differs by more than | mm, for a 1-1 cm. tube—the effects will be correspondingly greater. ‘The net result is that the product Vx d is tco small, and so also the expression for K. This investigation shows us that even the other glass tubes may all give a result a little too low. However, the other values of K vary irregularly and “do not show any progressive diminution with decreasing diameter, such as would be expected if the effect we are considering were important, except for the case we have considered. The other case where there was a radical difference between the tubes was that of the copper tube (Curve No. 13). In this case the resulting value of the constant A is much higher. We ' A small place on the tube wall was filed thi to allow the radium rays to enter. DM 2 386 Scientific Proceedings, Royal Dublin Society. have already remarked that this tube was in a single unbroken length, some 400 centimetres. Now in the light of the previous discussion this would mean that the critical velocity shown was probably really that corresponding to the diameter, inasmuch as there were no constrictions of the bore. Another explanation of the discrepancy would be that the part of the tube used for experimental purposes (between 4 and 2) was wider than the mean diameter: This was not the case. A third possibility—one which I think at least as probable as any of the others—is that the tube being long and very uniform, the point where the linear flow became sufficiently unstable to give place to turbulent motion was at a somewhat higher velocity. With shorter tubes, small eddies produced at entering have not time to die away; with uneven bores, eddies are produced, which, as the critical point is approached, naturally help to precipitate the destruction of the linear flow. This behaviour resembles results obtained by Barnes and Coker (éoc. cit.). We may then summarize Table I as follows:—The mean value of the constant A for all the glass tubes (excepting that of smallest bore, 1:1 ems.) is 2481. That is to say, Reynolds equation would become, for air in these glass tubes :— ye RD Soe (D) pu while for copper tubes (or possibly for all tubes sufficiently long and uniform) the constant X is 3120, and the equation :— p _ edeD (B) pa The value of the constants in each case is higher than Reynolds gives for water ; but it is remarkable that the difference is only, at most, about fifty per cent.; the order of the number is the same both for air and water. Parr DW: Verification of the law of dependence of the critical velocity on Density and Viscosity. The first attempt to examine how the critical velocity depended on the density and viscosity was made by comparing tle results obtained by working at widely different temperatures. Two lengths of hard glass tube were employed for the tubes 4B and AG, the latter one being selected as long as possible. They were fitted through corks in two large copper tubes (7 ems. diameter) which enclosed each of them for the greater part of their length. ‘The copper tubes served as steam-jackets for the experimental tubes, and steam inlet and outlet tubes were inserted through the corks at either end. Curves were plotled (1) at room-temperature, and subsequently Dowrinc—Steady and Turbulent Motion in Gases. 387 (2) while a blast of steam was passing steadily around the glass tubes. The arrangements, save for the steam-jackets, were again as represented in fig. 1; and the gasometer-method was, of course, employed to draw and measure the air-current. The method of measuring the air-current for the hot air was exactly the same as for the unheated air. No correction had to be employed for the temperature of the air in the drum V (fig. 2); for, after filling this drum with air through the heated pipes, it was found that the air was not appreciably higher in temperature. In its passage through the pipe P inside the gasometer, it parted completely with its heat. Thus the rate of rise of the drum gave the volume at room temperature flowing in per second. The equation we are to verify may be written :— V. of) as or, in words, that the product V. should be proportional to the viscosity. Now Vp is proportional to the mass of gas carried past a point in the tube when the gas has a density p. If suffixes denote temperatures, for a given rate of rise of the g asometer, the gas being at room-temperature (10° C.), we should have :— Vr P10 = Vo Pe, e., Vy is the velocity the gas would have if the tubes were at 10°C. Vio, however, is given by the formula (3) above, viz. :— Vn =e We will call Vy the “apparent” velocity ; and it is easy to see that this “apparent” velocity is proportional to the product Vo pe. Consequently, it will be sufficient to show that the ‘‘ apparent ” critical velocity at any known tube-temperature (@) bears the same ratio to the critical velocity at 10° as the viscosity at 0° C. bears to the viscosity at 10° C. The temperature 9 of the gas in the tube cannot be assumed to be that of the walls of the tube, for the gas will take some time to become heated. ‘lo determine this temperature, as closely as possible, a separate experiment was carried out. Into the tube, AB, was inserted a fine platinum wire stretched along the axis, and the ends of this were connected by thick copper leads to a Post-office box. Its resistance was then measured in the usual way. Several determinations were made of the resistance ; first at room-temperature; then when the steam-jackets were heated, but while no air was being drawn down the tubes GAB; and finally while the air was being drawn down at various speeds, both above and below the critical velocity. 388 Scientific Proceedings, Royal Dublin Society. The temperature of the wire was taken as 100°C., when the jackets were heated, with no blast on. ‘The resistance as measured at room- temperature and at 100° allowed the other temperatures to be calculated. Since the temperatures varied with the blast, the method adopted of representing the results by “apparent” velocities saves a large amount of unnecessary calculation in plotting the curves. At a velocity close to the critical velocity the temperature was found to be 90°C., and this is The curves No. 12 (Plate XXXIII.) represent the results of this experiment. We can best express them in tabular form as below (Table II). Sutherland’s formula is again used to calculate the viscosity of the air. consequently taken as the temperature of the air at that point. Tase II. a —_—— —-—— Ratios. Temperature, 10° 90° , ‘Apparent ’’ Critical Velocity, 180 212 1:18 ) | Viscosity, 000175 “000203 1-16 J Density, 00125 000973 78 True Critical Velocity, . 180 270 1:5 eh | elie =i 2610 2620 1-004 | 7 The values of the ratios in brackets in the last column, as well as the values of the constant XK calculated on the last line, indicate the excellent agreement between theory and experiment. It appeared of interest to push the inquiry further and to examine how. the law applied to other gases. In this investigation it is the ratio n/p that is important, and a gas is required for which this ratio differs from its value for air. With the exception of coal-gas, the gases most easily obtained in quantity are given in the accompanying table (‘lable III). Tanne IIT. Sia | n/p relative [ | | Air, “000175 00129 | -136 1 | Hydrogen | “000089 “0000897 99 7-29 | Oxygen, “000195 “00143 "134 0°99 | | ..Carbon Dioxide, \ 000146 00198 50a 0:5438 Dow iine—Steady and Turbulent Motion in Gases. 389 The critical velocity for a gas in a particular tube is proportional to n/p. Thus the critical velocity would be seven-fold greater for hydrogen than for air. It would be difficult to measure so great a velocity. Thus our choice remains between the other two. Oxygen differs little from air. Carbon dioxide was accordingly used in the experiments. In the experiments with carbon dioxide two gasometers were employed. The gas flowed from one to the other through the experimental tube GABC. As it was not convenient to take elaborate precautions against leakage, the following device was adopted :—A second wire (X) was attached to the drum JV of the first gasometer, and carried over the pulleys as shown in fig. 1. This wire passed in an exactly similar fashion over the pulleys of the second gasometer, and was attached to the drum thereof. Thus if no balance weights were hung from the original wire #, the gas in both the gasometers would be under identical pressures. When the weight was hung on its wire, it diminished tie “effective” weight of V, and the other drum pressed on the gas in the second gasometer. Thus at one end of the tube there was a slight excess, and at the other end a slight defect of pressure. At no point would there be any serious difference from atmospheric pressure. In performing an experiment, the gas was drawn, of course, in the direction ABC; and when the gasometer at C was full, the gas was driven back down the tube ready for another series of numbers. The speeds were adjusted as before by either altering the driving weight W, or throttling the flow by the tap 7. Preliminary experiments with this double gasometer arrangement showed that it worked even better than the original method. Steadier and more concordant readings were obtainable at all times. This was probably due to the fact that draughts and other external conditions did not influence the blast of air inside the tube. In consequence of this, some of the previous curves for air which had not been regarded as satisfactory, were repeated with this apparatus. ‘These are indicated in Table I by the remark “two gasometers.” Being satisfied by the experiments with air of the working of the new arrangement, one of the gasometers was filled with carbon dioxide; and after “ washing out” the tube-system and the other gasometer with the gas, the filled gasometer was connected to the tube system ABC. ‘The method of filling precluded the possibility of much admixture of air, and a small quantity would produce only a small effect on the viscosity, which for a mixture is given by the formula | 1) Vaal Ze yy = = - ue 2 (5) due to Graham. (Where »° is the covflicient of viscosity of a mixture of 390 Scientific Proceedings. Royal Dublin Society. volume V, of the gas A, with volume Vz of gas B.) A similar equation is approximately true for the density. An indirect confirmation of this law follows from some observations recorded later. ~The experiments with carbon dioxide are represented in the curves Nos. 14 to 16 (Plate XX XIII.). Subsequently a mixture of this gas with air was made by admitting some air. Curve No. 17 was obtained while using the mixture. Perhaps it will be simplest to compare each curve with the corresponding one for air. This is done in the following table. Waren JOW. Diameter of |No. of , xd | Lempera- Tube. Curve.| Velocity. aia Density. | Viscosity. gate K. d, cms. — Vem sec | = | 2 Cc | p n CO2 Air. | 1-9 (Copper), | 14 126 939 | 16 | -00185 | -000146 3030 | 3120 a | | 2-03 (Glass), | 15 104 212 15 -00186 | -000146 2720 | 2610 | | : ; | ( 98 | 304 ( \ | 700121 -000177 ( PANE E: ( 2460 | 3-8 (Glass), 17) | iis | 1] zo t| 266 t| () -o0157 |} -ooo164 || Mixture, || 2450 i} — | | — j— —_——. —_ i eal. ow Breen 6 7 8 9 he first seven columns give the particulars of the CO, experiments. In pVd ; 7 ot K for air. In the case of the third tube (3:8 ems.) the numbers for air were taken immediately after those for the CO,—air mixture; and they are given completely on the third line of the table. For the copper tube, the two values of K differ by 3 per cent.; for the narrower glass tube, by 4 per cent.; and for the wider tube the difference is less than } per cent. The gas mixture was analysed by drawing off about 100 ces. through the tap O into a Hempel gas-burette; after measuring the volume of the mixture, the CO, was absorbed in a potash bulb; and the volume of air remaining was measured. ‘I'he mixture contained almost exactly 60 per cent. of air by volume. The viscosity was calculated by the formula (5) above. The density by the corresponding formula, column 8, the values of = K are given; in column 9, the values (6) which gave results sufficiently accurate for our purpose, Dow1ine-—Steady and Turbulent Motion mm Gases. 391 For the copper tubes we now have two numbers for X, the mean of which is 3075; and for this tube Reynolds’ equation now becomes approximately 1540 » pl i Also for glass tubes, taking the mean of all the results in Table I (excepting Nos. 8, 10, 18), and those for CO. in glass tubes in Table IV., we obtain the mean value 2500 for 1, giving the equation for glass tubes 1250 y == ae These results, of course, are subject to the same remarks as to steadiness, &e., which were made in discussing ‘lable I. We have now shown that Reynolds’ equation applies to gases, as well as to liquids—but that the constant J, while of the same order, is greater for gases We will now consider the significance of the second discontinuity in the curves, which clearly indicates a second critical stage in the flow. (B’) V. (D’) Part V. Investigation of the second critical stage. The existence of the second critical stage was not suspected. There were no a priori reasons for supposing the existence of such an effect in a tube of uniform bore. The effect we now consider was first noticed on one of the widest tubes (5°03 ems.), and was there so well marked that it was mistaken for the ‘ Reynolds’ effect. ‘This caused some surprise, for the product V x d was about twice too great. ‘This experiment was the first performed with the gasometer arrangement. The next tube was the 3-centimetre tube, and this gave only one discontinuity in the curve, at a velocity which made v x d = 369, or of the order expected.! The next tube used gave the clue to these discrepancies. wo ‘discontinuities’ were found on the curve (No. 4, Plate XXXII.), for one of which the product V x d= 359. This we have already identified (Table I) with the ‘Reynolds’ effect. It was noticed that the other, together with that for the 3-cm. tube (Curve No. 5), and that found for the 5:03-em. tube, were roughly proportional to the radius of the tube. Fresh experiments with the large tube revealed the fact that this also gave two well-marked ‘discontinuities ’—that for the lower velocity giving the product V x d= 327, not very different from the other ‘ Reynolds’ critical points. In subsequent experiments both discontinuities were sought for, and, 1Cf. Part I, A & B, Part ITI, C. SCIENT, PROC. R.D.S., VOL. XIII., NO. XXVi. 3N 392 Scientific Proceedings, Royal Dublin Society. generally speaking, found, near the velocities expected. We had better, perhaps, postpone the consideration of the possible causes of this second critical stage until we have given a résumé of the facts regarding its production. First, a remark may be made as to the appearance of the effect. Curves nos. 2, 4, 6, 7, 8, 11, and 16 all have the discontinuity due to the effect. It occurs at the velocities 46, 75, 96, 118, 145, 79, 39, respectively. In many cases it is remarkable that the course of the curve could be prolonged from a little before where this discontinuity occurs, so as to pass into the subsequent part. We may also remark that the irregularity produced on the curve is usually much less marked than in the case of turbulence. These two characteristics seem to indicate that the effect is due to some phenomenon that does not influence the flow of the main body of gas, and would therefore seem to have its seat at the surface of the tube. The general facts regarding this second ‘discontinuity’ are given in Table V. (The last set of numbers refers to an experiment for which no curve is given).! Taste V. Diameter . : ae q Ye No. of Gas. Tube. Velocity. Temp. Pressure. | Viscosity. | Density. dn Cie cms. ems./secs. Oh, Inches. Air. Lop, P46 13 29°7 *000177 00122 289 2 50 2°03 ?79 10 30 175 125 256 wil 90 2°3 75 10 29°2 175 122 227 4 on 31 96 14 29°5 177 124 213 6 ” 3°8 118 15 29°9 177 124 216 7 90 5:03 145 12 29°8 176 125 204 8 COz, 2°03 39 16 29°8 146 186 245 16 Mixture, 3°8 88 14 29 164 154 218. = 1 2 3 4 5 6 7 8 9 The first six lines refer to experiments on air. These results are given graphically in fig. 3, where the abscissae represent the tube-diameters, and the ordinates the velocities. With one exception, the points lie very well on a straight line. This line cuts the axis of velocities at a point 1Tt was found that this discontinuity was very indistinctly marked in the case of the two smallest tubes. JI have marked the critical velocities as doubtful. Dow1ine—Steady and Turbulent Motion in Gases. 393 representing a velocity 16, and the axis of diameter at a point ‘6 em. to the left. Thus the results may be expressed by either of the equations— V, = 266 (d@+°6)... (7) or V. =(V - 16) = 266d... (8) Three possible explanations suggested themselves. First, that it was due to some irregularity introduced by unevenness on the tube-walls. ‘That this was improbable seems indicated from the fact that the effect was best marked on the wider tubes, and was very indistinct on the narrower ones, 60 40 20 100 Critical VelOcities Tube Diameters Fig 3. The electrical quantities could be measured with confidence even at velocities of 40 on the 1:1 cm. tubes; and their variations were certainly very small where the discontinuity ‘kink’ occurs (Curve II). Thus the unevenness of a tube can hardly be the cause of the discontinuity. The second possibility is that it is due to some persistent eddies set up at the mouth of the tube when the air enters and continuing inside. In that case the effect would depend on the length of the experimental tube. Varying lengths were used, no attempt at uniformity in this direction being aimed at, yet the equations given above (7, 8) hold for all. BN 2 394 Scventific Proceedings, Royal Dublin Society. On no occasion was it found possible to locate the discontinuity for the copper tube (19 cm. bore). This seems the most peculiar fact connected with it. As for the wide (7'4 cm.) tube, also of copper, it was not possible with the fan at our disposal to reach the speed of over 203 ems. per second mean velocity where this tube might have been expected to give it. A third possible explanation may be found in something of the nature of “slip.” It could very well be imagined to result in the same law, equally well during stream-line and turbulent motion. Measuring as we do the mean velocity of the blast, the velocity so measured, where slipping would take place, would not necessarily depend on whether the greater mass of the gas was moving according to stream-lines or not. What we should take into account would be the viscous drag on the walls, or on the layer of gas condensed on the walls. ‘The question arises, of course, what is meant by “slip,” in such a case. The most probable phenomenon to expect is something of the nature of ordinary turbulence, but in the layers nearest the walls of the tube. A sort of rolling motion of the gas-layers— may set in here instead of a sliding. For the same volume delivered, if no “slipping” took place near the walls, the maximum velocity in the gas must be greater than with slipping. Thus, since the ionisation measured at B depends on the time required to come from A to B as well as on the volume of air coming down the tube, if the volumes increase only slightly while the average time is not decreased sufficiently (which would occur if slipping had meanwhile begun), then the velocity-ionisation curve would commence to slope upwards less rapidly at the critical point in question. Let us for a moment consider the flow in a narrow tube. For, although our tubes are by no means narrow, yet some idea of the conditions existing before turbulence sets in may be gained from the case of narrow tubes. It is easy to show that if v,, is the mean velocity of the whole gas at any cross-section of the tube, since we have /au’ eal ey t (9) ” but we have seen (formula 8) that when the second “discontinuity ” occurs A for air (v,, — 16) is approximately proportional to the radius a. Hence * Ap at the surface would be a constant in any tube for a velocity 16 units less than the “ critical” velocity. Of course it is obvious that this argument assumes Dow.iinc—Sveady and Turbulent Motion in Gases. 395 conditions which are not closely approximated to in the experiment. Again, the law obeyed by this “critical” velocity seems to hold equally well for wide tubes, where it occurs after turbulent motion of the ordinary kind has set in. It is of interest, however, inasmuch as it seems to connect the proper- ties of the gas with the phenomenon we are considering. We have shown that it would follow from equation (9) that for all tubes e would have a con- stant value at the surface of the tube for a velocity just below the “ critical ”’ ov 2 represents rate of shearing, so to speak, of the gas at the or velocity. Now » : Ov . : ; : suriace layers. Again, 7 = for a given tube is proportional to the distance or from the centre, so that the shearing is greatest in the layers of fluid nearest the walls, If we grant that beyond a certain point “shearing” becomes unstable and tends to give rise to something, say, in the nature of “ rolling,” we should expect that this instability should depend on a “critical” value of the expression : a That is, for a given gas, it would depend on the velocity-slope ; for different gases it would depend directly on the viscosity, and inversely on the density. Unfortunately we have few numbers to check these deductions. However, in column 8 of Table V are given the values a I ; of the quantity = The simple ‘theory we have given would require this dy to be a constant; but such is hardly the case. ‘The numbers, however, seem to tend to a constant limit for the wider tubes. One fact, however, they appear to bring out, and that is the dependence of V on »/p, for the numbers for CO, and the CO, mixture agree quite well with those of the corresponding size tubes for air. — In a recent paper Stanton’ has shown that, even when turbulent motion obtains in a tube, the air flowing very close to the walls continues probably in linear flow—or, at least, that the factor governing the flow is the ordinary coefficient of viscosity (») and not the ‘ dynamic viscosity ’ (2), This throws some light on what we are now considering. Since the ‘ Reynolds’ critical point occurs at a velocity inversely proportional to the radius, while the second effect occurs at a velocity proportional thereto, for the smaller size tubes the second effect occurs during stream-line flow, while for larger tubes it occurs during turbulence. It is clear, therefore, that with Stanton’s result, it becomes less difficult to imagine how our second effect could obey 1 Stanton, Proc. Roy. Soc., vol. Ixxxy, 1911, p. 366. 396 Scientific Proceedings, Royal Dublin Society. the same law both when it precedes and when it follows the Reynolds’ critical point. A few other experiments were carried out to obtain further information on the origin of the second critical velocity. The first was made with a view to trying whether it might be possible to obtain the ‘discontinuity’ by producing irregularity inside the long copper tube. As we have seen, this tube yielded no sign of the effect. A short piece of glass tubing fitting closely was pushed down close to where the air was ionised and just to the left of the point 4. This exaggerated the effect of a paper tube in the case of the glass tubes. No break appeared on the curve, however, at any point near the velocity expected. This negative result seemed to dismiss almost completely any explanation based on irregularities in the bore of the tube. It was accordingly sought to investigate the phenomenon by an altogether new method. Parr VI. Heperiments on the Skin Eviction due to Air flowing in Tubes. Let us consider equation (9), above. It may be written nfs) ttm (90) or al where the left-hand term represents the tangential force (per square centi- metre) on the ¢wbe due to the moving gas. Let us calculate the possible magnitude of this force for velocities such as we have been using. Consider a tube 60 centimetres long, 1:9 cm. diameter; and imagine a blast of 50 cms./sec. average velocity to be traversing it. Suppose the temperature is 17°C., the viscosity will then be ‘000179; hence the total force on the tube in the direction of its length will be Qe aD = Bry mL. (10) or 8 x 3:14 x -000179 x 50 x 60, or 13:4 dynes, equivalent to 13°7 milligrammes weight. . . (F) This seemed a sufficiently large quantity to measure; and an experiment was devised whereby this ‘ skin-friction,’ as the force may be called, was utilized as the effect whose variations should indicate the various changes in the flow of the gas. Fig. 4 represents the arrangement adopted. One scale-pan of a Sartorius balance was removed, and also the pan-arrester. This left a small Dowiine—Steady and Turbulent Motion in Gases. 397 opening in the base directly beneath the hook on the end of the beam. A glass tube B was fitted with the wire frame C, and thereby suspended from the balance by a fine wire. A bent pipe P of almost the same diameter as B was held in the position shown, and accurately adjusted so that the paper tube, projecting from inside it, passed about a centimetre down inside B without touching. Thus the tube B was free to move with the swing of the balance-beam. The pipe P was connected to a gasometer of the pattern already described, from which a measured blast of air could readily be obtained by adjusting the stopcock and allowing the drum to fall by its own weight. ‘The ex- periment consisted then in counterbalancing the downward pull on B by weights on the scalepan. No allowance need be made for differences in the densities of air inside B, ~ and outside; for the effect of these will be small in comparison with the quantities we are measuring. The weights on being plotted against the mean air-velocities in the tube give a curve at first almost straight and then gradually bending upwards. At one point there is a distinct break in the curve—the rate of increase of resistance becoming suddenly less. ‘This occurs at a point agreeing very well with our expectations; for a 1:9 cm. tube it is at a velocity of about 70 cms./sec., while for a 25-cm. tube it occurs at about 84 cms,/sec. ‘The expected values are 66 and 81 respectively (cf. curve, fig. 3). The general form of the eurve and “break” seems to indicate that a change of some kind has taken place in the nature of the flow. Consequently we can assume that the production of the second “break” of the former experiments may really be due to some cause of the nature indicated previously. In conclusion, it is interesting to inquire whether the numerous experi- ments on gaseous ions may not in some cases be influenced by the phenomena we have been discussing. In such experiments the flow of gas is usually constant, whereas we have used different velocities and a constant electro- 398 Scientific Proceedings, Royal Dublin Society. motive force. Besides, in most of such experiments it is unlikely that a critical velocity is reached. ‘The effects of turbulent motion might, however, become of importance in such work when higher velocities are used. T have to thank Professor McClelland, F.r.s., for suggesting this research, and also for the interest he has taken in its progress. ‘To him and to the Royal Dublin Society my thanks are due for the use of the radium employed. I have also pleasure in recording here my indebtedness to Mr. J. J. Nolan, m.a., Assistant in the Physics Department of University College, for devoting much time to assisting me during many of the measure- ments, which were difficult to carry out single-handed. SCIENT. PROC. R. DUBL. SOC., N.S., VOL. XIII. 400 300 200 200 100 PLATE XXXII. (KE :O/) per min. OW) ELECTROMETER ELECTROMETER (A= -00/) pressure Lean Velocity cm /Sec) 120 160 200 240 N° 1. Are. ELECTROMETER ( K= -0/) Diameter 5 cms. pressure 29-8" temperature 12°C Lean Velocity cm/Sec. 30” T Diameter 1:6 cms. ELECTROMETER ( K 280 320 360 400 Diameter II cm. pressure 29-7" temperature 15 °C Llean Velocity em/Sec. 440 20 40 60 N° 2. AIR. _| Diameter 35:1 cms. pressure 29°35” temperature 14°C Ltean Velocity cm/Sec 70 80 90 100 110 N° 6. Air. Diameter I] cm. pressure 29-7” temperature J3°C Lean Velocity cm/sec. 80 100 140 180 220 260 300 340 380 N° 3. AIR. ELECTROMETER ( K=:0/) ‘0/) ELECTROMETER (KH 60 pressure 29-9" temperature 15°C 70 80 90 100 10 120 N° 7. AIR. Diameter 3:8 cms. 130 (K=0Z) ELECTROMETER 140 Diameter 2-3 cms. pressure 29-2” temperature 10°C Mean Velocity cm/sec. Diameter 5-03 cms. pressure 29:8" temperature I2°C 120 140 160 180 200 N° 8. AIR. = ‘meter 7° ssure 2, pperature velocity « | R i ( Copper Dian pres fem Mean Velo« 120 Prconr Dia pre: bem Mean Vela 120 ) ING B54 mse Gee ae rs iV! ty ican ‘eae Present) tea tian tl a : i mA a ae Sa i 5 nie mn mikes ye Ry ined acs pemeistis a ni wees SCIENT. PROC. R. DUBL. SOC., N.S., VOL, XIII. ‘0/) 40 —_ 20 PLATE XXXIII 100 80 i Execrromerter \(A= -0/) ExecrRomerTer \( A ELECTROMETER \( A= ‘O/) 60 40 Diameter 7-4 cms. pressure 29-25" temperature 12°C Mean Velocity cm/Sec. Diameter 5-03 cms. pressure 29-4" 20 temperature 12°C Mean Velocity cm/Sec.: 30 40 S50 60 70 80 90 20 40 60 80 40 60 N°? 9. Arr. N° 10. Arr. (Copper tude) Ol) FLECTROMETER (F- 130 Diameter 1-9 cms. pressure 29°7" temperature 16°C 120 No 14, C0, (Copper tube) 90 Diameter 1°93 cms. pressure 29°8" temperature 13°C Mean Velocity 210 220 230 240 250 260 270 280 190 200 Diameter 2-03 cms. pressure 29-8" temperature 15°C N° 13. AIR. (Copper tube) *O/) pressure 30” temperature 10°C 80 100 120 N° Il. Arr. Diameter 2-03 cms. FtecTRomerer \( A= ‘O/) Diameter 2:03 cms. pressure 30-1” “Apparent” mean velocity em/Sec. 80 100 20 40 60 80 200 20 40 N° 12. Air. “0/) — N° 16. CO2. Diameter 2°03 cms. pressure 29-8" temperature 15°C [Lean Velocity 20 40 60 = ELECTROMETER |(A Diameter 3°8 cms. pressure 29°5" temperature 14°C 80 N° 17. (CO, mixture bo 10. 11. 12. SCIENTIFIC PROCEEDINGS. VOLUME XIII. . A Seed-Bearing Irish Pteridosperm, Crossotheca Honinghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, D.sc., F.L.S. (Plates I.-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcr H. Peraysrince, B.sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witiam Brown, 2.so. (April 15, 1911). 1s. . A Thermo-Electric Method of Cryoscopy. By Henry H. Dixon, se.p., r.r.s. (April 20, 1911). 1s. . A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Witttam J. Lyons, B.a., a.R.c.sc. (Lonp.). (May 16,1911). Gd. . Radiant Matter. By Jon Jony, sc.p., r.z.s. (June 9,1911.) 1s. . The Inheritance of Milk-Yield in Cattle. By James Whitson, u.a., B.SO. {June 12, 1911.) 1s. . Is Archeopteris a Pteridosperm? By T. Jounson, p.sc., v.t.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Joayson, p.sc.,F.u.s. (Plates VII., VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Proressor Joan Jony, M.a., sc.p., F.R.s. (July, 1911.) 6d. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Joun Jony, sc.p., F.x.s., and Lours B. Suyra, Baa. (Plate IX.) (August, 1911.) Is. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks., By KE. A. Newett ARBER, M.A, F.LS. .G.S. (January, 1912.) 1s. 13. 14, 15. 16. 17. 18. 19. 20. 21, 22. 23. SCIENTIFIC PROCEEDINGS—continued. Forbesia cancellata, gen. et sp. nov. (Sphenopteris, sp., Baily.) By T. Jounson, D.sc., F.L.S. (Plates XIII. and XIV.) (January, 1912. 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Winson, ™.a., B.Sc. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Pontos, p.sc. (Plates XV. and XVI.) (February 21, 1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris., By Henry H. Dixon, sc.p., v.r.s., and W. R. G. Arxis, m.a. (February 21,1912.) 6d. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, F.R.s. (Plates XVIL—XIX.) (March 26,1912.) 1s. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Dixon, sc.d., F.z.s., and W. R. G. Arxins, u.a., atc. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Dixon, sc.p., F.n.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jonson, p.sc., ¥.u.s. (Plates XX. and XXI.) 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DURLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBBS. oe THE SCIENTIFIC PROCEEDINGS OF THE rOVAS DUBIN SOCIETY. Vol. XIII. (N.S.), No. 27. DECEMBER, 1912. UNSOUND MENDELIAN DEVELOPMENTS, ESPECIALLY AS REGARDS THE PRESENCE AND ABSENCE THEORY. BY JAMES WILSON M.A., B.Sc. PROFESSOR OF AGRICULTURE IN THE ROYAL COLLEGE OF SCIENCE, DUBLIN. { Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBUIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1912. lee Price One Shilling and Sixpence. Roval Bublin Society. Oa a FOUNDED, A.D. 1731. INCORPORATED, 1749. ——— OOS EVENING SCIENTIFIC MEETINGS. Tax Scientific Meetings of the Society are held alternately at 4.30 p-m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable ior the purpose will b2 printed with the least possible delay. Authors are requested to hand in their MS. and necessary Llustrations in a complete form, and ready for transmission of the Editor. [ 899 J XXVII. UNSOUND MENDELIAN DEVELOPMENTS, ESPECIALLY AS REGARDS THE PRESENCE AND ABSENCE THEORY. By JAMES WILSON, M.A., B.Sc., Professor of Agriculture in the Royal College of Science, Dublin. [Read Noyemuer 26; Published Decrmper 18, 1912.] In this paper it is proposed to show— i. That the Presence and Absence theory is unsound. i. That it leads to erroneous conclusions. iii. That phenomena to which it has been applied can be analysed by ordinary Mendelian formule. To do this it will be necessary first of all to state some part of the Mendelian position, and to show how formule are used in analysis. It is that there are factors or determinants for every character. he characters of similar parents may be represented thus :— The factors which such parents produce to be handed on to their "progeny may be represented thus :— SCIENT. Mate. FEMALE. Bbeeoerd ppp YYO 6 3% - » ppp (PHO os 0 © 9949 G97 ---- - 999 999 - +e» Os UP 56 rey SRP onc ane . &e, Ce PROC. R.D.S., VOL, XIII., NO, XXVIII. 30 400 Scientifie Proceedings, Royal Dublin Society. Being compelled to select similar semi-factors from each parent, the progeny must bear characters similar to those borne by the parents, and must breed true. If, however, the parents are not similar, but differ in one or more pairs of alternative characters, the progeny will receive mixed factors from their parents, and will not breed true as regards the differentiating characters, though they will breed true as regards the others. li the parents differ in one pair of alternative characters, and we repre- sent the dominant by X and the recessive by «, the progeny of their progeny, i.e., their second crosses, split into two groups, one bearing X and the other z, and the number of individuals in the group bearing X is to the number in the group bearing z in the ratio3: 1. If the parents differ in a second pair of alternative characters, say, Y and y, the group bearing X on the one hand and that bearing z on the other split each into two further groups, one bearing Y and the other y; and the numbers bearing Y are to those bearing yas3:1. Thus there are four groups altogether, one bearing the characters XY, ancther Xy, another zY, and another zy, and the numbers of individuals in these groups are in the ratio 9:3:3:1. For every additional pair of alternative characters in which the parents differ, the number of groups into which their second crosses divide is doubled —for one pair there are two groups, for two pairs four groups, for three pairs eight groups, and so on—and the proportional numbers in each group expand in accordance with a well-known mathematical formula. This can be shown diagrammatically : x £ For 1 pair: 3 1 YS eS 4 ab NS Ye S Ya ~ Va iN Ze SX Ki y iY y For 2 pairs: 9 3 3 1 Yer YEN YEN. Yes Zo NeoN ON ete LEN : Z 2 Z zg Z zg Z z For 3 pairs: 27 9 9 8 9 3 3 1 TNC ET IS OY NS STEN ASTRA A RA Gs A =A eA eG eA eG Hor pairs Si 27,027. 9 = 27 919) 3) 279 a oS and so on. If we consider by way of example the case for three pairs of characters, we see that there are eight groups of second crosses; and if we follow the Witson—Unsound Mendelian Developments. 401 forking lines from X and « downwards, we see that these eight groups bear the following characters, while the numbers in each are shown by the figures seed, Viz, 21 XYZ, 9 MVs, 9 key Z 3 kgs 9aeVZ, 3 Vs, 3 sy xyz. The following table shows how the groups and the numbers of individuals in each expand up to the case in which ten pairs of characters are considered :— NUMBER OF GROUPS. Number of For For For For For For For For For For individuals in 1 2 3 4 5) 6 7 8 9 10 each group. | pair. pairs. pairs. pairs. pairs. pairs. pairs. pairs. pairs. pairs. UU 1 1 1 1 1 l 1 1 1 1 3 1 2 3 4 4 6 7 8 9 10 9 1 3 6 10 15 21 28 36 45 27 1 4 10 20 35 56 84 120 81 if 5 15 30 70° 126 210 243 1 6 21 56 126 252 729 i 7 28 84 210 2187 1 8 36 ©6120 6561 1 9 45 19683 i 10 59049 1 Total number of groups = 2 4 8 16 32 64 128 256 412 1024 Reading from the top of the columns of figures downwards, the top groups (always containing one individual) carry every recessive operating in the ease; the next groups (of three individuals) carry n-1 of the recessives and one dominant; the next groups (of nine individuals) carry » - 2 recessives and two dominants, and so on. Reading from the bottom upwards the same rule holds, if dominants be substituted for recessives and recessives for dominants. The table will indicate how difficult it is to deal, experimentally or otherwise, with cases in which more than three or four pairs of characters are considered. The chief uses of the foregoing formule are three, viz., (1) to tell how many groups are formed, with the proportionate numbers of individuals in each, by the second crosses from two individuals differing in one or more pairs of alternative characters; (2) conversely, to tell, from the numbers of groups of second crosses and the proportionate numbers in each, in how many pairs of alternative characters the original parents differed; and (3) to indicate which characters are alternatives and how the two characters in a pair stand to each other as regards dominance and recessiveness. Let us consider several examples, by way of illustration; and, since they 302 402 Scientific Proceedings, Royal Dublin Society. must be either familiar or readily imagined, we shall take them from domestic animals rather than from plants. Take first the formula for one pair of characters, viz., X:e2=3:1. A set of second-cross cattle may be divided into two groups by reason of their colours, which are black and red, intheratio 3:1. The formula tells us that, in this case, there is one pair of differentiating characters, namely, black and red, and that these colours are an alternative pair with black dominant and red recessive. It tells us that the grandparents of the second crosses were black on the one side andred on the other. It can be inferred readily that a factor whose function is to produce blackness produces the black character, and another whose function is to produce redness produces the red. Take next the formula for two pairs of characters, viz., DEERE SG Te Vig Ven 3 3) 3) 2 i Another set of second-cross cattle may be divided into four groups by yeason of their colour and their horns. he groups are—black and hornless, 9; black and horned, 3; red and hornless, 3; red and horned, 1. The formula tells that there are two pairs of characters concerned, that both dominants are shown by the group of nine, one dominant and the remaining recessive by each group of three, and both recessives by the group of one. Thus the two alternative pairs are blackness and redness on the one hand, and horn- lessness and hornedness on the other: the first-named being dominant in each case. The formula cannot tell whether the grandparents were similar to the two end or to the two middle groups, since the same result could come from either mating. As in the previous case, the characters and the factors which produce them are obvious. Take next the formula for three pairs of characters, viz., BL ENG SIS AE DAG 8 2 op 2% IGe IZ SCR ILS 7) 44, 2, BUG LIGS D253 ZFS % Pi aVeteothe ais 3.5 a) 2 I Still another set of second-cross cattle may be divided into eight groups by reason of their colour, their horns, and their faces. The differentiating characters in the groups and the numbers of individuals in each are—black, hornless, and white-faced, 27; black, hornless, and black-faced, 9; red, Witson— Unsound Mendelian Developments. 403 hornless, and white-faced, 9; black, horned, and white-faced, 9; black, horned, and black-faced, 3; red, hornless, and red-faced, 3; red, horned, and white-faced, 3; red, horned, and red-faced, 1. According to the formula there are three pairs of characters concerned in the case. The three dominants are exhibited in the group of twenty-seven, two dominants and the third recessive in each group of nine, one dominant and the two remaining recessives in each group of three, and the three recessives in the group of one. In each group of nine the recessive which is shown is the alternative of the dominant which is not shown. In each group of three the dominant which is shown is the alternative of the recessive which is not shown. ‘Thus the three dominants in this case are blackness, hornlessness, and white-face, while their three corresponding recessives are redness, hornedness, and normal face: normal face being that in which the face colour is the same as that of the body. As in the previous cases, there is no difficulty in identifying the characters and the nature of the factors to which they are due. That being so, we may set down this case, just as the typical one for three pairs of characters was set down, with letters indicating the characters concerned instead of the unknowns, Xx VyZz. B = black. 7 =yed. P = hornless or polled. / = horned. W = white-faced. n = normal-faced. ‘To make the descriptions of the groups clearer we shall range them across the page thus :—- 27 B P W : Black, polled, white-faced. 9 B Pn : Black, polled, normal-faced. 9 +P W : Red, polled, white-faced. 9 Bh W : Black, horned, white-faced. 3 Bh n : Black, horned, normal-faced. 3 Pn: red, polled, normal-faced. 3 7 h W : ved, horned, white-faced. 1 +h n_: red, horned, normal-faced. But many cases have been found since the Mendelian method of analysis came into use in which the interacting characters have been difficult to identify. One of the first was that of fowls’ combs. When rose and single combs were mated the first crosses were all roses, and the second crosses roses and singles in the ratio 3:1; and, when pea and single combs were mated, the first crosses were all peas, while the second crosses were peas and singles in the ratio 3:1. From this it was inferred that the rose and pea combs 404 Scientific Proceedings, Royal Dublin Society. were each dominant to the single, and it was expected that either rose or pea would be dominant the one to the other—“ that either rose or pea would dominate in the hybrids, and that the #2 generation ” (i.e. the second crosses) “would consist of dominants and recessives in the ratio 3:1.’ But the expectation was not fulfilled, for, when rose and pea were mated, their first erosses were a new kind of comb—walnut—and their second crosses consisted of four kinds, namely, walnut, rose, pea, and single—also new—in thie ratio 9:3:3:1. This ratio shows that there are really two pairs of alternative characters concerned in the case. ‘he characters and their factors may be difficult to identify, and, because of this difficulty, they can be represented in the meantime by unknown symbols only. By so representing them, we may be able to trace the connections between some of the determinants and to get some idea of their effects. The formula to meet the case is:— Walnut 9. Rose 3. Pea 3. Single 1. xX Xx x B Vv y Iv y No single character can be identified, nor can the effect of any factor be told. All that can be said is that walnut results with the concurrence of X and Y, rose with X and y, pea with # and Y, and single with w and y. Nor can it be said how far any factor is responsible for the character produced. How far X or how far Y, for instance, is responsible for walnut there is no evidence to show. And no more can it be said, since each is the result of more than one factor, that rose or pea is dominant the one to the other, or that either is dominant to single. What can be said is that a factor in the rose-comb is dominant to a factor in the single, and a factor in the pea is dominant to another factor in the single. But from matings between some of these combs and another kind—the Breda—further information can be gathered. The fowl with this comb “is usually spoken of as combless, for the place of the comb is taken by a covering of short bristle-like feathers. In reality it possesses the vestige of a comb in the form of two minute lateral knobs of comb-tissue.’’* When this comb is mated with rose on the one hand, or single on the other, the first crosses have two points in common. The progeny of the roses are still roses, but split in two ; and the progeny of the singles are still singles, but also split in two. ‘lhe Breda comb, therefore, carries a factor for splitting or duplicity which is dominant to a factor for non-splitting or simplicity carried by both the rose and single combs. ‘Then, if we represent the duplicity 1 Punnett’s Mendelism, 3rd ed., p. 29. * Idem, p. 30. Witson— Unsound Mendelian Developments. 405 factor by D, and the simplicity factor by s, the factorial constitutions of pure rose and pure single, so far as we now know them, may be written down in the customary manner as XXyyss, and wryyss. But the matings with the Breda comb show another pair of factors. The rose and single combs are both of some size, while the Breda comb is merely a vestige ; and the first crosses of the two former with the Breda are also of some size. Thus, the roseand single combs each carry a factor which allows or causes to be produced a comb of some size, while the Breda carries a factor which is responsible for nothing but the vestige of a comb; and, since the first crosses are of the size of rose and single, the size factor is dominant to the vestige factor. ‘Then, if we represent the former by (C, and the latter by v, the constitutions of pure rose and single combs should now be written down XXyyssCC, and vrxyyssCC. From the same matings the constitution of the Breda comb can also be found. We have seen already that it contains D and v. It can also be shown to contain wand y. Let us go back to the typical examples chosen from cattle. In the third example from cattle differing in three pairs of characters, there were a group black, polled, and white-faced, and another red, horned, and normal-faced. But these two groups had many other characters besides—how many we do not know—in none of which they differed. ‘he characters of these two groups may therefore be written down LEIP WED G) POS, o pbb in the one case, and Pl WG iG PP 6s 60.8 in the other. Some of the characters pyr ..... are dominant, some recessive to other characters in other cattle; but most of them are the same as in other cattlo. There can be no doubt, however, that pgr..... are common to both the above groups, else their second crosses would have differed in more than three pairs of characters. Thus it must not be assumed that, when two groups differ in one or more pairs, they have no other characters than those in which they differ. If one group is dominant to another in the way the rose comb is dominant to the single, it must not be assumed that the two groups are each the result of only one factor: that they have no other factors. The real state of affairs is that they may have many others, but, when sufficient crossing brings out no differences, these others (so far as they are mateable) are the same for both groups. When the Breda comb was mated with the single, the first cross was a split or duplex single comb. The factor for duplicity had effect, but the vestigial factor had no apparent effect. The factors 2 and y of the single comb also had effect, since the result was still what we call a single comh 406 Scientific Proceedings, Royal Dublin Soctety. though split in two. Thus the Breda comb carried either factors that were recessive to x and y, or the factors x and y themselves. The first crosses of the Breda and single mating were not mated again, and so no second crosses were produced by which this point could be decided. But from the rose and Breda matings, half the doubt can be decided. There were single combs in the second crosses. Where did they come from ? The constitution of the rose parent was A XyyCCss, and of the Breda, so far as yet known, DD. From these a single comb, whose constitution we know to be zxyyCCss, was bred. The factor wv was not contained by the rose- combed parent, and must therefore have been carried and brought in by the Breda, whose constitution, therefore, must be at least vzvvDD. As to whether it also contains yy, there is no direct proof; but the fact that it contains wz, together with the further fact that its progeny when mated with the single comb are apparently different in no way from single, except in duplicity, is very strong presumptive evidence that it does. If a mere opinion were expressed, it would be that the constitution of the Breda comb is zvyyovDD. The matter cannot be settled absolutely until second crosses are bred from Breda with pure pea or walnut, neither of which contains yy. It may be pointed out, however, that there is further presumptive evidence in support of the above opinion. If it be correct, the constitutions of all the combs discussed should be at least when pure :— Sime . ¢ o oe Oo CO 84. Rose So 0 200 9 y CC. ee Pea song We IY C6 3 Weal) o 5 0 AOC JAY CO 36, JBC 5 5 5 Oa We Ow JDID, The rose comb and the Breda were crossed. On the assumption that the constitution of the Breda, as given in the above table, is correct, then the rose and Breda differ in three pairs of characters; and, in their second crosses, there should be eight groups with the usual numbers in each, and with the pure individuals showing these constitutions :— XX yy CC DD _ : Duplex roses, : i oi) BY XX yy CC ss _: Simplex roses, é 9 XX yy ce DD : Combless duplex roses, . 9 vx yy CC DD : Duplex singles, 9 XX yy vv ss : Combless simplex singles, 3 ze yy CC ss _: Simplex singles, 3 zx yy vv DD : Combless duplex singles, 3 vu yy vv ss : Combless simplex singles, ] Witson— Unsound Mendelian Developments. 407 This result corresponds with the results given in Professor Punnett’s “‘Mendelism,”! excepting that there the combless fowl are all lumped together as “ Bredas,” and the numbers of individuals in each group are not given. Had the Bredas been grouped and counted, the evidence would have been complete. As it is, it is very strongly presumptive that the constitution assumed for the Breda is correct. In any case the foregoing is an example of how the Mendelian formule may be applied, and may help us to follow the working of the presence and absence theory. Unfortunately this theory has not yet been fully explained. It has, however, been used frequently for analytical purposes, and, from statements made in cases in which it has been so used, its general purport can be made out ; but, since theunderlying logic has not been exhaustively expounded, the principle desired to be established may be difficult to find. The theory originated at the time the fowls’ combs were being studied, and was first used to explain the experimental results in that case, which seemed unusual. Its authors took a different view from that taken in this paper as to the factors concerned in the production of rose, pea, and single combs. Although it seems impossible to think otherwise than that, when a set of second crosses split into four groups standing to each other, as regards the numbers they contain, in the ratio 9: 3:3: 1, there must be two pairs of differentiating characters concerned, and that each group must bear at least two characters, they took the view that rose, pea, and single comb are each the result of one factor only. Holding this view they saw nothing unusual in the walnut resulting from the mating of rose and pea. It was a com- pound character, one of a kind “ produced by the mutual interaction of factors belonging to distinct allelomorphic systems.” The difficulty arose when two first-cross walnut combs mated produced a single comb. How was this to be accounted for? Professor Punnett puts the case thus :—‘‘ How are we to express the fact that while single behaves as a simple recessive to either pure rose or to pure pea, it can yet appear in (2 ” (i.e., in the second crosses), “‘from a cross between those two pure forms, though neither of them should, on Mendel’s view, contain the single?” (‘on Mendel’s view ” ought rather to be on the view that rose and single combs are due to single characters). The explanation given of the anomaly is that, while walnut is the com- bined result of the rose and pea factors, and the other combs are each the result of their own individual factors, the single comb emerges from the 1 p. 37, Diagram Si, Bille SCIENT. PROC. R.D.S., VOL. XIII., NO. XXVII, : BP 408 Scientific Proceedings, Royal Dublin Society. crossing in the case when the factors for rose and pea are absent. ‘The con- stitution of the walnut comb is written RRPP. That of rose ought to be written RR; but, in order to indicate that the factor for pea has no hand in the case, i.e., 7s absent, the letter p is added, and the constitution is written RLRpp. Similarly, to indicate the absence of the factor for rose in its produc- tion, the constitution of pea is written 7PP. Following these precedents the constitution of single comb ought to be written, say, SiSipp—sSS to denote the factor for single comb, and spp the absence of the factors for rose and pea—but it is written »7pp. By writing it thus we are not told what does produce the single comb, but what does not; and the danger of 77 and. pp changing their significance in the course of manipulation is increased by the absence of a positive symbol of some kind to represent the factor for the single comb. Divided into separate paragraphs to make the reasoning clear, Professor Bateson’s statement of the case is as follows :— 1. “A rose comb is not due to an elemental factor which can segregate from the pea comb factor. 2. “The two factors belong to distinct allelomorphic pairs, and each in the gametogenesis of the heterozygote segregates from its own allelomorph, which is simply the absence of the factor in question. 3. “The single comb contains neither & nor P. 4. “The rose comb is a single comb modified by the presence of R&, while the pea comb is produced by the presence of P. 5. “* Wemay therefore describe the roseas & no P, and the pea as P no R. 6. “ It is convenient to use capital letters for dominants, and small letters for recessives, the rose being written thus, Rp, andthe pear P. The walnut comb is the RP, while mp gives the single.’’! Thus the first two paragraphs affirm rose and pea to be due each to single factors. The second paragraph states that these factors “segregate” from their own absences. ‘This could be understood if the word “absence” were used’ metaphorically for real factors alternative to rose and pea; but it is not easy to think of such a thing as a factor segregating from nothing, or, at any rate, from something which is not present. As already mentioned, the third paragraph tells what the single comb does not contain, but not what it does contain. In the fourth paragraph the rose and pea combs become due to something more than & and P, namely, to the effect of the factor for single comb plus 1 Bateson’s ‘‘ Mendel’s Principles of Heredity,’’ p. 66. Witson— Unsound Mendelian Developments. 409 that for rose in one case and that for pea in the other. This paragraph is thus inconsistent with the first, and, if it be correct, the descriptions in the next paragraph of rose as “ no P” and pea as “ Pno R” are incomplete, since they leave out the thing modified by RK and P. One or other of these two statements, viz., that rose is due to a single factor in the first paragraph, or that it is due to more in the fourth, must be wrong. Consider whether the facts of the case agree with the view that rose and pea combs are each due to single factors. Let RR be the constitution of rose and PP of pea. If RR and PP can be brought in simultaneously to the same comb, they will be brought in either as non-alternative or as alternative factors. In the former case they may have effects that are independent of each other or they may have effects that cannot be separated by the eye the one from the other, but it is difficult to imagine anything being produced in the second crosses but roses and peas and combs the same as the first crosses. On the other hand, if RR and PP are alternatives, their first crosses will be hybrids of the constitution RP, and their second crosses should be of the constitutions RR, RP, and PP in the ratio 1:2:1. But neither of these results is found in the second crosses from rose and pea. ‘The results do not fit the assumption of hybridization, and, on both assumptions—hybridization and combination—there is a comb produced which has no business to be produced at all. Thus, unless the rose, pea, and walnut second crosses are produced from the first-cross walnuts in some way which allows an extra comb to be produced ex nihilo, the assumption that rose and pea combs are each due to single factors must fail. Consider next whether the assumption holds when the case is dealt with on the presence and absence theory. According to Professor Bateson’s sixth paragraph, the constitutions of the four combs, walnut, rose, pea, and single, are RRPP, RRpp, 7rPP, and rrpp. It must not be forgotten that the small letters merely represent the absence of the factors represented by the large ones. They are merely helps to the memory, and unless as such might as well be absent. In the case of the single comb, »pp indicates that it is produced without the assistance of RR or PP. By what, then, is it produced? It must be produced by something, and since RR and PP are both absent, that some- thing must be separate and distinct from both. Causes that are absent can have no hand in producing effects that are present. A cause, by being absent, may allow another cause which it previously obstructed or whose effect it obscured to have effect, but the essential cause of this effect is the one which is present. ‘There being no symbol set down to represent the factor or BP 2 410 Scientific Proceedings, Royal Dublin Society. factors that produce the single comb, the mnemonics 77 and pp are com- mandeered instead, aud thus are made use of as positive factors. And not only does this happen with the single comb; it happens with other combs also. In the chess-board scheme displaying the presence and absence solution of the problem to be found both in Professor Bateson’s and in Professor Punnett’s books, the constitutions Rrpp (rose) and 7pP (pea) are given: and unless the small letters represent positive factors, these two combs are produced by only half a factor—a thing which, so far, has not been found possible, for it would mean that only one parent is necessary. ‘Thus, when the case is dealt with by the presence and absence theory, the assumption that the rose and pea combs are each produced by single factors fails again. Since the facts of the case which the presence and absence theory was first set up to explain are not as they were taken to be, the theory itself comes under suspicion, and the suspicion is deepened when symbols are used mnemonically at one time and positively at another. A little further con- sideration will show the theory to be unsound on its own merits, and will bring out the nature of the fallacy. Doubt has already been raised as to whether a factor could segregate from its own absence. It was raised upon the statement that “the two factors ” (i.e. for rose and pea) ‘ belong to distinct allelomorphic pairs, and each in the gametogenesis of the heterozygote segregates from its own allelomorph, which is simply the absence of the factor in question.” There is no question about a factor “segregating” from its own allelomorph, that is, vacating a position which its allelomorph is about to occupy. ‘The question is, Can a factor’s allelomorph be its own absence, and can the factor segregate from its absence —that is, Can a factor segregate from no factor at all? Unless the word be used figuratively for what has taken the place of the absent factor, the action suggested is impossible. For, when a factor is removed from any position, its place must be taken by something else—and as yet we kuow of nothing that can do so but another factor—and the only “segregation ” possible must take place with that something else. Ifa book be taken from its shelf, we may say that its absence is left—that the book has “segregated” from its absence—but we can only say so figuratively, for what is really left is air and dust; and, when the book is put back again, we may say that it takes the place of its absence, but we can only say so figuratively. In dealing with the application of the presence and absence theory to Mendel’s peas, Professor Punnett writes':—‘‘On this theory the dominant character of an alternative pair owes its dominance to the presence of a factor ' Punnett, p. 31. Witson— Unsound Mendelian Developments. 411 which is absent in the recessive. The tall pea is tall owing to the presence in it of a factor for tallness, but in the absence of this factor the pea remains a dwarf. All peas are dwarf, but the tall is a dwarf plus the factor which turns it into a tall. Instead of the characters of an alternative pair being due to two separate factors, we now regard them as the expression of the only two possible states of a single factor, viz., its presence or its absence.” Dealing with the general question, Professor Bateson writes that ‘* All observations point to a conclusion of great importance, namely, that a dominant character is the condition due to the presence of a definite factor, while the corresponding recessive owes its condition to the absence of the same factor.” Without doing more than remark that the latter part of Professor Punnett’s statement virtually makes the presence and absence theory turn two factors into one, only to be obliged immediately to turn the one factor into two again, it may be said that these two statements are ambiguous. They are open to two interpretations, and unfortunately the worse one is frequently taken. If these statements mean that the long factor turns a short pea’s progeny tall, and that on its removal the tall pea’s progeny become short again, but that the short pea is still due to the same cause or causes that made tt short before the intro- duction of the long factor, there is no ground for quarrel with the statements further than that they do not state the whole case. But this is not the usual interpretation put upon them; and the other interpretation, which is probably taken because of the above incomplete statement, is that, while a factor itself is the cause of a dominant character, its absence is the cause of the corresponding recessive. ‘lhis credits a thing which is absent with the work done by another thing which is present but overlooked. The real state of affairs is that the ABSENCE OF THE LONG FACLOR MAY BE THE CAUSE OF THE ABSENCE OF THE LONG CHARACTER, BUY 11 IS NOY THE CAUSE OF THE PRESENCE OF THE SHORT. If long and short peas were crossed and re-crossed again and again so as to produce alternate generations of long and short peas, the view might be taken that the absence of the long factor allowed the effect of the short to become visible, but that would not deprive the short character of its own essential cause. Under such circumstances the absence of the long factor might be regarded as a “condition” necessary to the emergence of the short character; but this does not justify us in preferring this condition as the cause of the production of the short character over a still more essential condition. If a pedestal supporting a bust be knocked away, we are not justified in 1 Mendel’s ‘‘ Principles,’ p. 44. 412 Scientific Proceedings, Royal Dublin Society. preferring the absence of the pedestal as the cause which brings the bust to the ground and overlooking the action of gravity. As might be expected, the presence and absence theory, when used for analytical purposes, falls into the error of overlooking real recessives. Being frequently hidden, they are not always.readily identified and connected with their proper dominant. ‘hen, when the dominants in a case under analysis are already allotted their own absences as their only possible recessives and one or more recessives turn up without their connexion with their dominants being identified, so many more factors are introduced beyond the number which the case can hold. One such case will be sufficient by way of example. Mr. C. C. Hurst made a long series of experiments with rabbits! He started with what seemed to be only three kinds, namely, grey, black, and albino. But the albinos were found to be of two kinds, and thus he really started with four pure kinds. When greys and blacks were mated, the first crosses were all grey, and the second crosses greys and blacks in the ratio 3:1. Thus grey seemed dominant to black. When greys were mated with one albino, the first crosses were all grey, and the second crosses greys and albinos in the ratio 3:1. Thus, grey seemed dominant to albino also. But when grey was mated with the other albino, while the first crosses were grey, the second crosses were greys, blacks, and albinos in the ratio 9:3:4. Thus, while the first two cases indicated that there was only a pair of determinants concerned in each, the last case showed that there were more. In this last case there are presumably two pairs of determinants concerned; but one of the second-cross groups of three is indistinguishable from the group of one. Three of the albinos form one of the two groups of three, and the fourth albino forms the group of one. If this assumption results in a disagreement with the facts, it can be abandoned. Let us find what each determinant stands for. Write down the four groups by name, with the non-committal formula and unknown symbols below :— 9 Grey. 3 Black. 3 Albino. 1 Albino. x xX x oD 1% y wy y At first sight it would appear as if the two dominants were albino and black; but, since albino is carried by the last group, it must be recessive, and, since the same character is carried by the third group, it must be ‘ See Journal of the Linnzan Society, Zoology, yol. xxix, p. 283. Witson— Unsound Mendelian Developments. 413 represented by 2, which is common to both groups. Its dominant must therefore be X. Tt will be noticed that, when X has a chance of showing itself, the rabbits are coloured, while, when # has a similar chance, they are albinos. The difference between X and « is that X is concurrent with colour-production, and x with albinism. It is no unfair assumption, therefore, that, in some way not disclosed, X allows or causes colour to be made, while x does not. Thus, the factor which allows colour to be produced as in the grey is dominant to that which does not allow it to be produced as in the albino. The factors left over to have effect in the production of some particular colour are Y and y; and, since grey occurs in the group of nine, and black in the group of three, 1’ must be the factor connected with grey, and y with black. Substituting now the initial letters of the words ‘colour,’ ‘grey,’ ‘black,’ and ‘albino’ for the symbols previously used, we can write down the whole case thus :— Grey. Black. Grey albino. Black albino. C C a a G b G b And this solution agrees with the facts of the case. The constitutions of the pure individuals in each group are grey CCGG, black CCbd, grey albino aaG@G, and black albino aabdb. One albino contains the factor for greyness, while the other contains that for blackness, just as Mr. Hurst found; and in the first crosses the greys will behave as dominants to all, just as Mr. Hurst found, while the second crosses from all possible pairs will come out in agreement with experimental and other observations, thus :— 1, Grey x black will give 3 grey : 1 black. 2. Grey x grey albino will give 3 grey : 1 albino. 3. Grey x black albino will give 9 grey : 3 black : 8 grey albino: 1 black albino. 4, Black x grey albino will give the same result. 5. Black x black albino will give 3 black : 1 albino. 6. Grey albino x black albino will give albinos only. The presence and absence theory arrives at a different result. It introduces an extra factor which pushes the factor for blackness out into a new position. The factors employed are—grey (G), absence of grey (g); presence of colour (@), absence of colour (c); and black (B). The factor g 414 Scientific Proceedings, Royal Dublin Society. is extra ; and B, which was formerly a recessive, is now something common to all. The reason for this divergence is that, since, on the presence and absence theory, the only possible alternative to G is its own absence, g, there isno alternative left for black but to be pushed out of its place. But this solution is not consistent with the facts of the case, for the factor for black- ness was not carried by the original grey parent, nor was it common to all Mr. Hurst’s crosses. He showed clearly that it was introduced by one of the albinos. Jet us see how the problem is solved on the presence and absence theory. ‘Applying the presence and absence system to the case of the colours of rabbits, the first pair of allelomorphs can obviously be represented as— Dominant Recessive 1. Presence of colour (C). Absence of colour (c). The second pair we have so far spoken of as the grey determiner and the black determiner, regarding the two as allelomorphic to each other. But it is equally possible to describe them thus 2. Grey determiner (@). Absence of ditto (,). Then in the case where grey x albino gives in 2 9 grey: 3 black: 4 albino, we simply have to regard B, the black determiner, as common to both parents, and the same numerical result is produced.”’ The error arises through failing to realize that g and B are the same. Another solution of the same problem on the presence and absence theory might also be quoted :—“ Agouti,” i.e. grey, “‘ was previously known to be a _ simple dominant to black, i.e. an ‘agouti is a black rabbit plus an additional greying factor which modifies the black rabbit into agouti. This factor we will denote by G, and we will use B for the black factor. Our original agouti and albino parents we may therefore regard as in constitution GGOCBB and ggccBB.” With regard to this statement it might be asked : if agouti, since itis dominant to black, is a “black rabbit plus an additional greying factor,” might it not be regarded equally as an albino plus an additional greying factor, since it also ‘‘ behaves as a dominant to the albino variety ?” With regard to the above case, it might be pointed out that in a parallel case, viz., that of colour in pigeons, in which the second crosses were 9 black, 3 blue, 4 white, just as the rabbits were 9 agouti, 3 black, 4 albino, a parallel? solution was not found as it ought to have been. ‘Bateson, p. 76. 2 Punnett, pp. 48 and 60, Witson— Unsound Mendelian Developments. 415 While the presence and absence theory, being unsound, must lead to erroneous conclusions, some of the work it has helped to produce is workably sound. ‘This happens in cases where no real recessive is identified to raise confusion with the unidentified “absence.” The theory originated in the error of taking characters due to several causes to be due to one; and it fails in assuming a factor’s absence to be its own recessive, with the result that, when a real recessive is identified as active, a factor just one too many for the case to hold has to be introduced, as we saw in the ease of the rabbit colours. We shall see this if we analyse by the Mendelian method a case which has been brought to a correct conclusion by the presence and absence method, and incidentally we shall see the power of the Mendelian formule in analysis. We shall take the case of mouse-colours dealt with by Cuénot and Miss Durham. : Miss Durham’s first experiment, in which two pairs of characters are concerned, was with agouti and chocolate mice. The second crosses were 9 agouti : 3 cinnamon agouti : 3 black : 1 chocolate.’ Write down these groups with the non-committal scheme below:— Agouti. Cinnamon agouti. Black. Chocolate. P Ie p p Q q q q In Miss Durham’s second experiment, the second crosses from black and silver-fawn were 9 black : 3 blue : 3 chocolate : 1 silver-fawn.2 From the first experiment we know black to consist of pQ and chocolate of pg. As to the other characters in the case, we can only write down non-committal symbols. Thus the provisional scheme becomes Black. Blue. Chocolate. Silver-fawn. p ~p Q q S S 8 8 R r R r The new characters may or may not be the same as the previous ones. Ss is obviously the same as Qg, or a new pair in which S concurs with Q and s with g. In that case the two pairs could not be separated, and we therefore take Qq as representing both Qg and Ss, which are either the same or two inseparable pairs. The pair Rr is obviously new, since it can concur with no other pair already present. It is just possible for R to be the same as p, ! Kyolution Committee Report, iv, p. 42. 2 Ibid. SOIFNT. PROC. R.D.S., VOL. XIII., NO. XXVII. 3Q 416 Scientific Proceedings, Royal Dublin Society. that is recessive to P and dominant to 7, but this is unlikely. It would mean a series like that of the horse colours. Assume &r to be a new pair for the present. The assumption can be dropped later if found inconsistent with the facts. Then the provisional scheme for these four colours and the two left behind in the first experiment becomes Agouti. Cinnamon agouti. Black. Blue. Chocolate. Silver-fawn. IP TP p p Y) q @ @ q q R r Tt iP But we can go farther. The first experiment showed that agouti and chocolate differ in only two characters. Therefore agouti contains &. The same experiment showed also that cinnamon agouti and agouti differ in only one character. Cinnamon agouti, therefore, also contains R. The second experi- ment showed that blue differs from black and from silver-fawn each in one character. Therefore blue and silver-fawn both contain p. We can now write these six colours more fully :— Agouti. Cinnamon agouti. Black. Blue. Chocolate: Silver-fawn. iP P p p p p Q q Q @ q q R R R r R r At this stage 1r CAN BE PREDICTED that, when the complete set of colours is worked out, there will be eight groups in all, viz., one for every combination of six characters in groups of three. In Miss Durham’s third experiment, agouti and blue gave 9 agoutis: 3 dilute agoutis (a new colour) : 3 blacks : 1 blue.t Thus dilute agouti differs from agouti, black, and blue, each in one factor. Its composition might be found in several ways. ‘The simplest is to write down the possible combina- tions in groups of three of the six factors PQRpq’, and select that which fits the case. There are eight groups, viz., PYF, pQRk, Pak, PQr, Par, pQr, pqk, and pgr. Since dilute agouti differs from agouti in one factor, it must contain two dominants and one recessive, and it must be found therefore in the second, third, or fourth group. It cannot be pF, since that represents black. It cannot be PR, since then it would differ from blue in three characters. It can only be PQr. In Miss Durham’s fourth experiment, the last of the eight groups was 1 “ Journal of Genetics,’’ vol. i, No. 2, p. 177. Witson— Unsound Mendelian Developments. 417 found. Cinnamon agouti and silver-fawn gave cinnamon agouti, dilute cinnamon agouti (the new colour), chocolate, and silver-fawn in the ratio 9:3:3:1.1 Thus dilute cinnamon agouti differs from each of the others in one factor, and it can only be Pqr. If we now write down the eight groups, we see that they are really such a set as might be produced in the second crosses from two parents differing from each other in three pairs of characters. We may therefore set down in addition the numbers for each group. Agouti. Cinnamon Dilute Black. Blue. Chocolate. Dilute Silver- agoutl. agouti. cinnamon agouti. fawn. P iP P p p p iP p q 1 @ @ q q q q R fe ip R ? th r r 27 9 9 9 3 3 3 1 In this case the two methods of analysis arrive at the same result; but the presence and absence method arrived at this result because no effective recessive was disclosed to raise confusion among the absences, and there was therefore no need to introduce a factor more than the case could contain. Had such been disclosed, the presence and absence theory would have had to give it a name; its dominant would then have had two recessives —its absence and the disclosed character—and confusion would have resulted. So long as the presence and absence theory introduces no superfluous factor it works like the Mendelian theory itself, although those who use it may imagine they are working with the other. Since the presence and absence theory is unsound, it follows that any theory depending upon it is also unsound, and that work done upon the presence and absence or upon any dependent theory will have to be revised. In this connection it may be suggested that the first essential is that more attention be given to the logical consequences of the Mendelian formule. It is not necessary to give less attention to micrographic and internal aspects, but it is necessary to give more to macrographic and external. By way of illustration, several tentative solutions of cases suggested by the data given in Professors Bateson’s and Punnett’s volumes might be put forward. It must be understood clearly, however, that these solutions are only tentative because the complete data have not been available. 1“ Journal of Genetics.’’ vol. i, No. 2, p. 177. 418 Scientific Proceedings, Royal Dublin Society. (i) Whole-coloured yellow rabbits were mated with Himalayan rabbits which are white with black ‘“‘ points.’ The first crosses were whole-coloured agoutis. Thus, whole colour is dominant to the Himalayan pattern. The second crosses were agouti (27), yellow (9), black (9), tortoiseshell (3), and Himalayan (16). The whole-coloured rabbits are thus—agouti (9) : yellow (3): black (8): tortoiseshell (1). Black and yellow are thus dominants: together they produce agouti, and their recessives together produce tortoiseshell. The three pairs of factors concerned in the case are thus :— Y, which produces Yellow when concurrent with 0, and its recessive y. B, which produces Black when concurrent with y, and its recessive 0. W, Whole colour, and its recessive 4, Himalayan pattern. Their second crosses will be represented by the following scheme :— Y B W = whole-coloured agoutis, ; 6, 2 Y B h = Himalayan agoutis, Y 0 W =whole-coloured yellow, y B W =whole-coloured blacks, y b W =whole-coloured tortoiseshells, y B h = Himalayan blacks, Yb h = Himalayan yellows, y b h = Himalayan tortoiseshells, ~t rFPwowmw oOo © (ii) Black barb pigeons were mated with white fantails.® The first crosses were black with white splashes. Thus splashing was dominant to the plain colour, and had been carried, though obscured, by the white fantails. Thus, also, black seemed dominant to white, but the second crosses revealed the white fantails to be carrying another obscured character, namely, blue which is black’s recessive. ‘There were 9 blacks: 3 blues: 4 whites. It is a case similar to Hurst’s rabbits, and may be represented thus :— Black (3) Blue (8) Black albino (8) Blue albino (1) C C a a B bl B b1 The three pairs of factors are—— C, colour and its recessive a, albino. B, black and its recessive 07, blue. S, splashed and its recessive p, plain. 1 Punnett, p. 56. ? Punnett, p. 60, Witson— Unsound Mendelian Developments. 419 Their second crosses will be represented as follows :— C BS = Black, splashed eur C Bp = Black, plain. eee) C bl S = Blue, splashed . peed its) a BS = Black albino, splashed 9* a bl S = Blue albino, splashed 3° a Bp = Black albino, plain . 3* CG bl p = Blue, plain ‘ eB a bl p = Bluealbino, plain . 1* The different albinos (*) cannot, of course, be distinguished from each other by the eye. (iii) From two white kinds of sweet pea, Professors Bateson and Punnett were able to extract six kinds of coloured sweet peas whose colour-factors the whites had been carrying without their effects being apparent. From these six coloured kinds the white factors were eliminated and the coloured kinds bred and observed separately. The point to be noticed is that there are six groups: an unusual number. Is there something wrong with the Mendelian formule, or are there really more than six groups or less ? The first crosses from the two whites were a purple flower with blue wings. ‘The second crosses were purples and reds in the ratio 3:1. Thus purple is dominant to red. But the purples on the one hand, and the reds on the other were subject to a set of parallel variations. The first-cross purple had bluish wings; and this same kind appeared in the second crosses with two others, of which one had its wings darkened from bluish to purple, while the third was a dilute form of the first. Corresponding to these were a red with lighter wings, a red with red wings, and a dilute form of the first. ‘Taking the purples as the example, the ratios in which the three kinds appear are purple with bluish wings, 9; purple with purple wings, 3; dilute purple, 4. If the Mendelian formule be correct, we have here a set of four groups in which the two last are not separated. The formula to meet the case 1s Purple with bluish wings. Purple with purple wings. Dilute purple. Dilute purple. 9 3 3 : I ag X a x Y y Y y Where X is carried the colour is dense; where « is carried it is dilute, and the densing factor is dominant to the diluting. Where Y appears the colour 1 Punnett, pp. 74, &c., and Bateson, pp. 93, &e. 420 Scientific Proceedings, Royal Dublin Society. is partially eliminated from the wings, and they are light ; where y appears it is not: only in the case of the third group, which is dilute, this elimination is not clearly visible. In the whole case there are thus three pairs of factors concerned, viz. : P, Purple and its recessive 7, red. D, Densing and its recessive d, diluting. H, Eliminating colour from the wings, and its recessive e, non-eliminating. Their second crosses will be as follows :— PDE = Dense purple with light wings 27 PD e = Dense purple with dark wings 9 Pd = Dilute purple with light wings 9 7: DE = Dense red with light wings 9 rd # = Dilute red with light wings 3 r De = Dense red with dark wings 3 Pd e = Dilute purple with dark wings 3 r d e = Dilute red with dark wings 1 Thus there ought to be eight groups; and it is very probable that only six were found because the dilute purples and reds with dark wings were not distinguishable by the eye from those with light wings. Several minor suggestions might be made: first, that factors may not drop out and leave none in their place, or—which is the same thing—come in without displacing others. In connection with sweet peas it has been suggested that the numerous cultivated varieties have arisen from the wild “by a process of continuous loss.” In the table above, the variety at the top (PDE) is the same in colour as the wild Sicilian form. It is suggested that one or more of the factors PD and # have dropped out and given us our cultivated varieties: for instance, that H dropped out of the wild Sicilian variety and gave us a purple variety with dark wings. That may be in part : it may be that H dropped out, but when it did so, another factor, in this case its recessive, e, took its place. A tendency has been manifested on the part of some workers, particularly in America, to take it for granted that every observable character must have an “absence.” It may be suggested now that there may be danger even in the narrower assumption that every character has an alternative. It is certainly wrong to assume that every dominant character can have only one recessive and every recessive only one dominant. It might also be suggested that the use of the words epistatic and hypostatic might be revised. ‘They are used to indicate the relative positions of the Witson— Unsound Mendelian Developments. 421 factors for groups in a set: factors which prevent others from manifesting their effects being regarded as higher or epistatic, and the concealed factors being regarded as lower or hypostatic. In the case of mice “ the determiner for grey” is spoken of as epistatic to that for black, and that for black as epistatic to the determiner for chocolate. There are, however, several determinants concerned in the production of each of these colours; and we can only express the relative positions of the alternative pairs of these determinants, for which purpose the words dominant and recessive are equally appropriate. 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OSMOTIC PRESSURES IN PLANTS. I.—Metuops or Exrractine Sap From PLant ORGANS. BY HENRY H. DIXON, Sc.D., F.R.S., UNIVERSITY PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN; AND W. R. G. ATKINS, M.A., A.L.C., ASSISTANT TO TUE PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN. [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price One Shilling. ( 2 LONE Roval Bublin Society. DOO FOUNDED, A.D. 1731. INCORPORATED, 1749. Tooaey EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. Witson— Unsound Mendelian Developments. 421 factors for groups in a set: factors which prevent others from manifesting their effects being regarded as higher or epistatic, and the concealed factors being regarded as lower or hypostatic. In the case of mice “ the determiner for grey’ is spoken of as epistatic to that for black, and that for black as epistatic to the determiner for chocolate. There are, however, several determinants concerned in the production of each of these colours; and we can only express the relative positions of the alternative pairs of these determinants, for which purpose the words dominant and recessive are equally appropriate. If, on the other hand, the words are used to indicate the relative positions of groups in a set, they can do so only partially. In the set 9XY:3Xy:37Y: 1 zy, the first group might be called epistatic to the other three, and the second and third groups each to the fourth; but how is the relationship of the two middle groups to each other to be indicated ? The writer of this paper is very deeply indebted to his colleague Dr. F. EK. Hackett, who was already interested in the mathematics of the subject, for many suggestions and criticisms. SCIENT. PROC. R.D.S., VOL, XIII., NO. XXVII, 3R [ oe 4 XXVIII. OSMOTIC PRESSURES IN PLANTS. I.—Mertnops or Extracting Sap From Pranr OrGAns. By HENRY H. DIXON, Sc.D., F-BS., University Professor of Botany, T'rinity College, Dublin; AND Wi sG. eAUDIKGIN'S Maan ACC Assistant to the Professor of Botany, Trinity College, Dublin. [Read Decemper 17,1912. Published Fezrvary 8, 1913.] In several recent researches on the freezing-points of the sap of plants it has been our practice (5,10, 11, 12, 13), and that of several other investigators (Sutherst, 21; Cavara, 6 and 7; Heald, 14; Nicolosi-Roncati, 19; Trinchieri, 20; Marie and Gatin, 15), to press the sap from the living untreated organ. ‘he sap so obtained has been regarded as a fairly average sample of the sap of the organ pressed. ‘This seemed a reasonable view to take, inasmuch as the pressures applied so completely crushed the cells of the tissues that the sap expressed contained large quantities of protoplasmic fragments, which in the case of green organs were particularly noticeable, owing to the presence of chlorophyll corpuscles embedded in them. It seemed allowable to assume that, where the component cells are so completely disintegrated as is indicated by this observation, all the sap of their vacuoles must be shed into the expressed fluid; or at least there would be no reason to suspect a difference in composition between the latter and the sap which remained behind in the organ, Fairly early in our work, however, we made observations which, in the light of subsequent work, might have borne a different interpretation. For example, when we exposed leaves to the vapour of chloroform, we found that the sap was pressed out with much greater ease, and its freezing-point was very much lower, than that of the sap coming from the untreated leaves. No. of Expt. Description of Sap. A 227 Pressed from untreated leaves on gathering, . : : ¢ 0:774° 229 Same sap as in 227 to which a few drops of chloroform had been added, | kept 24 hours, 0:962° 232 From leaves similar to those used in 227 after they had been 24 hours in the dark, 0-781° 233 From leaves similar to those used in 227 after they had been 24 hours in the dark and in chloroform vapour, 5 3 1-280° Dixon ann Arkins— Osmotic Pressures in Plants. 423 _ This may be illustrated by the experiments made on the sap of leaves of Hedera Heliz, shown in table above (p. 422). A comparison of experiment 227 with 229 shows the increase of the depression of freezing-point we may expect from the saturation of the sap with chloroform. Experiment 232is added by way of comparison to indicate the change in freezing-point which is experienced by the sap of untreated leaves when kept for twenty-four hours in the dark. The depression of the sap pressed from the chloroformed leaves is evidently much greater than can be assigned to the action of the chloroform on the sap, or to the spontaneous changes in the cells of the leaves, which appear in experiments 229 and 232 respectively. Another result which could be interpreted in the same sense was furnished by two experiments on the sap of leaves of Ilex Aquifolium. In these it was found that, if the leaves were killed by heat in a saturated atmosphere, they yielded a sap having a much greater depression of freezing-point than that pressed from similar leaves which had not been heated. Teese, | Description of Sap. | A | 430 Sap pressed from fresh leaves, . 0°667° 431 Sap from leaves heated to 97° C. for 80 minutes, 1:225° Again, we found that, if a weighed quantity of leaves be desiccated, reduced to powder, and again made up to the original weight with water, the sap pressed from the mass will have a much greater depression than that pressed from the fresh leaves without passing through this treatment. This point is borne out by the following experiments :— Hedera Helix. ee Description of Sap. A 434 From fresh leaves, 4 x 2 : : f f 0-728° 435 From similar leaves desiccated, . 5 : ; ; : 1:031° 436 From fresh half leaves, . : : : . 5 0°869° 437 From remaining halves desiccated, : : ‘ : F Leaf In experiments 436 and 437 the specific electrical conductivities of the saps at 0° C. were also determined, and were found to be respectively 0:00485 and 0:00623. This shows that the quantity of electrolytes in the sap pressed from the desiccated leaves has increased approximately proportionally with the other dissolved substances. ao BR2 424 Scientific Proceedings, Royal Dublin Society. These observations were made primarily with other objects in view. But even then the possibility that the sap pressed from the untreated leaves was not so concentrated as that remaining behind in them presented itself. However, it seemed more probable that the greater concentration of the sap derived from the chloroformed, heated, and desiccated leaves was attributable to changes due to the treatment in each case, and we deferred the investigation of the discrepancy to a later date. Recently a short paper of Marie and Gatin (15) directed our attention again to this point. These writers when investigating the cryoscopic value of the sap of alpine plants note that the sap expressed first from a plant-organ has a smaller depression of freezing-point than that pressed subsequently. They content themselves, however, with adding the successive samples together, and take the freezing-point of the mixture as the freezing-point of the sap of the plant. This progressive concentration of the sap pressed from plant-organs had been, we found, very convincingly established some years previously by André (1, 2, 3, and 4), who also showed by exhaustive chemical analysis of the plant organs which he examined that, while the concentration of the sap expressed by increasing pressures rose, the proportion of the constituents remained the same. The following experiments of our own illustrate this progressive concen- tration of successive pressings from the same leaves. The leaves experimented upon were made up into a pellet, wrapped in two folds of fine linen and pressed in the jaws of a vice. As the vice was screwed up five or six drops of sap were pressed out and caught in a capsule; then the vice was opened and the same leaves re-arranged and pressed again. The sap exuding on this occasion was collected and kept separate from the first sample: similarly a third sample was prepared. Successive pellets of leaves were dealt with in the same manner; and so, from the same set of leaves, three samples of sap were obtained. ‘These were called Ist, 2nd, and 8rd pressings. For each the depression of freezing-point A and, in some cases, the electrical conductivity C, were determined. ‘The latter measurements were always made at 0° C. Hedera Helix: leaves. | No. of Experiment. Ist Pressing. | 2nd Pressing. 3rd Pressing. ) [ Aa A C. A Cc. 458, 459, 460 0-998° 1:110° — 1:579° = i 462, 463, 464 0-694° 0°782° 0:00496 0°888° 0°00518 Drxon anp Arkins—Osmotic Pressures in Plants. 495 These figures show very plainly the increase of concentration in the later samples, and by inference the still higher concentration of the sap remaining behind in the pressed leaves. Hence, the concentration of the expressed sap may be expected, in all cases, to be less than the average concentration in the vacuoles of the tissues before the application of pressure. The explanation of the increasing concentration is not hard to find. When the pressure is first applied, almost pure water is extruded from the intact cells, for the protoplasmic membranes are sensibly semipermeable, permitting water to pass out under pressure, but resisting completely, or in part, the passage of dissolved substances. ven in the first pressing many of the cells are usually burst, and their sap passes out with, and is diluted by, the much more dilute sap coming from the uninjured cells. Subsequent pressings contain the sap of a larger proportion of burst cells, and those which are now burst have had their sap concentrated by the former application of pressure. Hence, later samples must be more concentrated.’ From this consideration it appears that the problem of obtaining an average sample of the sap of a plant-tissue by pressure resolves itself into the problem of rendering the cell-membranes permeable, so that the applica- tion of pressure will force out solvent and solutes alike. It goes without saying that the method adopted for rendering the membranes permeable must not itself alter the concentration of the sap. Exposure to toluene vapour first suggested itself as a means for rendering the protoplasm permeable. Owing to its extremely small solubility in water, it was hoped that it would not appreciably alter the freezing-point. By experiment it was found that A for water saturated with toluene is approximately 0°024°, so that the correction for its vapour going into solution would not be a serious one. To test the efficiency of toluene vapour in making the protoplasm permeable, a sample of leaves of Hedera Heliz was gathered; each leaf was halved, and two lots (A and B) were made, each containing a half of every leaf. These two lots were then kept under the same conditions of moisture and darkness in closed glass vessels, the only difference being that in the vessel enclosing lot A an open capsule containing cotton wool soaked in toluene was placed. 1The pressing out of sap by mechanical pressure from uninjured cells may be observed in an apparatus used by one of us (8) some years ago for the determination of the osmotic pressure of the cells of leaves. In this series of experiments leaf-bearing stems were sealed into a stout glass vessel, while their ends projected beyond its end and dipped into a capsule of water. By a suitable contrivance air was forced into the yessel, and when the gas-pressure within it attained a certain magnitude the wilting of the leaves was obseryed and fluid was pressed into the capsule from the branch. It was then possible, by relieving the pressure, to allow the leaves to recover their turgescence and reabsorb water from below. 426 Scientific Proceedings, Royal Dublin Society. After 48 hours the freezing-point and the electrical conductivity of the sap pressed from the two lots were examined. In order to see if the increasing concentration, which is characteristic of the sap pressed from untreated leaves, occurs in the case of the sap pressed from the leaves exposed to toluene vapour, the sap from this lot was divided into first, second, and third pressings. Hedera Helix: leaves. Lot A (exposed to toluene), 1st pressing, z 1-865° Piao z | 2nd pressing, : 1-875° 0:00521 3rd pressing, 6 1°856° 0:00560 | Lot B (control), a : : . 0:868° — These results show that, with an exposure to toluene vapour of 48 hours, the protoplasm has become permeable, and no longer tends to keep back the dissolved substances of the vacuoles. Of course, such prolonged exposure has the objection that during this process enzymes in the cells may considerably alter the nature of the dissolved Substances, and so lead to a change in the concentration and constitution of,the sap. Accordingly, experiments were made to determine if shorter exposures would be sufficient. By means of these experiments it was found that shorter exposures, e.g., 1-5 hours, caused a marked concentration of the sap expressed when compared with that from the same leaves untreated ; but much longer exposures were needed to render all the cells permeable, and so allow the sap obtained to be a fair sample of that of the uninjured leaf. The prolonga- tion of the exposure makes the method objectionable. Accordingly, it was abandoned as unsatisfactory. It occurred to us then that the protoplasmic membranes might be rendered permeable by exposure to low temperature; while, at the same time, the low temperature would have the effect of arresting changes taking place in the tissues experimented upon. ‘Through the kindness of Prof. W. H. Thompson we have been able to obtain ample supplies of liquid air from the Physiological Department, Trinity College, for this purpose. Tissues immersed in liquid air immediately become frozen hard. From the liquid air they were without delay transferred to, and enclosed in, a stoppered vessel to prevent the condensation of moisture on them from the atmosphere owing to their extreme cold. When they had assumed the temperature of the surroundings, they were pressed in the usual manner. It is generally found that alter this treatment comparatively small Dixon anp Arkins— Osmotic Pressures in Plants. 427 pressure is needed to obtain the sap, which flows easily from the tissues without requiring the disruption of the cells. At the same time the sap is much freer from the debris of broken cells than that from an untreated leaf. This sap, so far as our experiments have at present gone, has always given a greater depression to freezing-point and usually a higher conductivity than that from the same tissues untreated. Furthermore, these determinations differed from similar measurements made on sap of the same tissues exposed to toluene vapour. The results are tabulated here :— apo | Sap from | A C x 108 2 aa 472 Hedera Helix, leaves untreated, 0°767° 403 5:2 473 Same leaves frozen, 1:255° 605 4°8 476 Part of same sample 19 hours in toluene vapour, - | 1:444° 536 3:8 477 Hedera Helix, leaves frozen, . : : | 1:239° 558 405 | 478 Same leaves as 477 in toluene vapour 2 hours, : 5 0:°747° 422 5:6 483 Tlee Aquifolium, roots untreated, 0-531° 563 10°6 484 Same sample as 483 frozen, 0°682° 629 9:2 | 486 I, Aquifolium, leaves untreated, 0°651° 433 6°6 | 487 | Part of sample 486 frozen, 1:130° 619 54 494 | Iris germanica, rhizome untreated, 0°450° 128 2°8 495 i Same rhizome as 494 frozen, 0°825° 335 4:0 510 Pyrus Malus, fruit untreated, 1°507° 171 11 | ayn Same fruit as in 510 frozen, 1:919° 161 0-8 ! | 612 Citrus Aurantiwn, fruit untreated, 1:044° — — | 5138 Same fruit frozen, 1:206° 208 i1o%/ 518 Citrus Limonum, fruit untreated, 1:038° 291 2°8 519 Same fruit frozen, 1:089° 345 3:2 514 Solanum tuberosum, tuber untreated, . 0°523° 555 11:0 515 Same tuber frozen, 0°588° 583 9°9 516 Vitis vinifera, fruit untreated, 2°567° 132 0°5 517 Same fruit frozen, 3°185° 112 0:3 538 Chamaerops humilis, leaf untreated, 0°365° 298 8-1 539 Same leaf frozen, 1°529° 752 4-9 552 Chamaerops humilis, leaf untreated, 0:599° 508 8-5 554 Same leaf frozen, 1°517° 926 6-1 549 Beta vulgaris, root untreated, . 1:473° 570 3°9 551 Same root frozen, 1:761° 555 3-2 These results show conclusively that the concentration of the sap pressed 428 Scientific Proceedings, Royal Dublin Society. from the untreated tissues is seldom at all similar to the concentration of that obtained from the same tissues after freezing. It is hard to see how freezing could be supposed to alter the concentration of the sap, whereas, as we have already seen, it is certain that the sap pressed from living tissues may be considerably less concentrated than that which remains behind, and conse- quently less concentrated than that which was originally in the cells of the tissue before the pressure was applied. It is well known that chemical changes are arrested at such low temperatures as that of liquid air; however, it seemed just possible that changes might take-place in the proteids or in the protoplasm just as the cold was being applied, and that these changes might lead to an increase in the quantities of dissolved substances in the sap. d To set this doubt at rest we determined the freezing-points of the sap pressed from the untreated roots of Beta vulgaris and from the leaves (also untreated) of Chamaerops humilis before and after freezing in liquid air; also of the fluids of an egg and of bull’s blood under the same conditions. ‘These liquids were not cleared in any way of the matter suspended in them, so it is certain that they contained ample amounts of proteids and of protoplasm to test the point. The results were as follows :— rea = A C x 108 549 | Untreated sap of root of Beta, a 1:473° 570 550 | Same sap frozen in liquid air, i 1:474° 574 552 | Untreated sap of leaf of Chamaerops, 0°599° 508 553 | Same sap frozen in liquid air, . | 0-575° | 502 479 | White of egg untreated, 6 : 0:446° —_— 480 White of egg frozen in liquid air, . 0°445° _— 481 Bull’s blood untreated, : ; 0°616° — 482 | Bull’s blood frozen in liquid air, —. 0°584° — In no case was a greater depression detected after exposure to liquid air. The diminution in the depression observed in the experiments 553 and 482 appears to be due to the expulsion of dissolved gases. The frothing of the sap of Chamaerops on thawing after treatment with liquid air was very marked. This was not looked for in the case of the bull’s blood. Hence it appears that there is no reason to believe that the application of liquid air leads to a concentration in solutions in contact with proteids and protoplasm. Again, the sap extracted from plant-organs after exposure to liquid air does not cause plasmolysis of the cells in these organs. This was demonstrated Drxon anp ArKins— Osmotic Pressures in Plants. 429 both for the sap of the root of Beta and for the leaf sap of Chamaerops. In the case of the latter the demonstration is particularly convincing, Sap from the frozen leaf was found to have a depression of 1:517°, while the value of A for that of the untreated organ was 0°599°. Yet the former caused no plasmolysis in the cells of a section of the leaf mounted in it, even after twenty minutes. The difference in concentration indicated by these two freezing-points would of course rapidly produce plasmolysis. This clearly shows that no appreciable concentration has been effected by the treatment, and that the sap pressed from the untreated organ is not isotonic with that in the vacuoles of its cells. Of course the application of liquid air cannot stop changes taking place while the sap is being pressed, as is evidenced by the production of colour in the sap of many tissues during the process. That this coloration is in reality due to oxidation, in contradiction to our surmise put forward in a previous paper (10), may ke shown by the fact that a tissue which when untreated yields a coloured sap will give a colourless sap if injected with a small quantity of a solution of tannin before pressing. The tannin acts as an inhibitor of the oxidases present and checks the formation of the pigment. The cells treated with liquid air seem to be rendered completely permeable, This appears from the fact that the sap is so easily pressed from the tissues after the exposure, often without any disruption of the cells. Also the concentration of successive pressings from these frozen tissues remains sensibly the same, e.g.— Hedera Helix: leaves. No. of 7 Expt. — A | C x 10 473 Exposed to liquid air, Ist pressing, . | 1255 606 474 Fe 2nd pressing, . | 1°261 597 Hence we may assume that the sap so obtained isa fair sample of the sap of the uninjured tissues, It will be noticed that in most instances the difference in conductivity between the sap of organs treated with liquid air and that of those untreated is not so marked as the difference in freezing-point, Comparison of the C x 10° ratio for the pairs of experiments will make this clear. This perhaps may be largely attributed to the greater permeability of the protoplasm to electrolytes, so that the sap pressed from the untreated organs is relatively richer in them, The result, however, was not anticipated, as from André’s work (1, 2, 3) it appeared that the proportions of the solutes present in the sap were not altered SCIENT. PROC., R.D.S., VOU. KIII., NO. XXVIII. 3s ‘430 Scientific Proceedings, Royal Dublin Society. by their passage out of the organs under pressure. Hence it was to be expected that the ratio of the electrolytes would remain sensibly the same for the sap pressed from the living tissues and for that from tissues rendered ‘permeable by liquid air. The results for the rhizome of Jris germanica and for the fruit of ‘Citrus Limonum are exceptions, and may very probably be assigned to actual differences in the sap from two apparently similar portions of the same massive organ. It is also possible that part of this effect is due to the greater vaseasty of the sap-from the treated organ. These two factors probably also account for the anomalous fall in conduc- tivity noticed in the sap of the fruit Pyrus Malus and of Vitis vinifera obtained by means of liquid air. It is certain that a much less extreme cold than a of liquid air would render the protoplasm permeable (Maximow, 16, 17, 18); but where liquid air is available it has the advantage of being very rapid in its application, and reduces the chances of change in the sap toa minimum. We have made a few experiments with the object of finding out if the application of heat in a saturated atmosphere, or the exposure to chloroform vapour, might be used as a substitute for exposure to liquid air. First, with regard to the application of heat, a quantity of leaves of Ilex Aquifolium were divided down the midrib, and two samples, A and B, were formed, each containing half of every leaf used. -A was wrapped in moist bibulous paper, enclosed in a metal box, and placed for ten minutes in a water-oven at 95°C. ‘The half-leaves were then cooled on ice and pressed, the sap ee out easily. Sample B was immersed in liquid air, and then pressed.' The results of two pairs of comparative experiments were as follows Nos. 500 and 501 were made on leaves of the antepenultimate growths; while Nos. 502 and 508 were on leaves from the BrOaie enultimate growths.) Tiex Aquifolium: leaves, No. of . 5 Expt | a | C x 10° | 500 | Sample 4 from heated half-leaves, ~ 11622 | ‘677 501 Sample B from frozen half-leaves, ~. 1:244° 696 © 502 Sample 4 from heated half-leaves,. . 0°816° 504 | 503 Sample B trom frozen half-leaves, . 1°305° 844 From these results it is evident that ten minutes’ exposure to 95° is not sufficient to render the membranes permeable with certainty.’ Owing to the likelihood of serious changes taking place in the sap, it: moulds not es feasible to EOD the leaves for longer to so high a temperature...) - Dixon anv Arkins— Osmotic Pressures in Plants. 431 A similar objection was found to apply to the use of chloroform. For this test samples A and B were prepared in the same way as in the foregoing experiment. -4 was then exposed to the vapour of chloroform for thirty minutes, pressed, and to the sap obtained a few drops of chloroform were added to ensure saturation. ‘The freezing-point was then determined in the usual way, except that the control-tube of the apparatus was charged with distilled water, saturated with chloroform instead of with pure water. “his change was, of course, not made when working with sample B, which before passing had been immersed in liquid air. The conductivities were determined in the usual manner described in the paper which follows: Hedera Helix: leaves from S. aspect. No. of : | | : Expt. — A | © x 10 492 Sample 4, half-leayes exposed to chloroform, 1-063° 485 493 Sample 2, half-leaves exposed to liquid air, . 1°315° 562 Here again it appears that the exposure to chloroform vapour has not been sufficient, and it is evidently inadvisable to prolong the opportunity for spontaneous changes beyond thirty minutes. The realization that the fluid pressed from untreated tissues does not give a fair measure of the concentration of the sap in the vacuoles of the uninjured tissues must modify the estimates of the freezing-points and the osmotic pressures in the vacuoles of vegetable cells determined by ourselves and others on these juices. In every case we have as yet examined the estimate must be raised, and in some cases very considerably. This may be seen by reference to the table given above. The difference is exceptionally marked in the case of Chamaerops humilis. So far, however, as we have been able to check our previous results, we have found that the concentrations of the sap in the various organs of the same plant pressed after exposure to liquid air follow the same order as we found for the sap from the untreated organs, e.g.— Llex Aquifolium. Treated with _ = | Untreated" | liquid air. . Sap of roots, 5 : 0°670° 0°682° Ultimate leaves, : 0°738° pent 0720 Penult leaves, Z 0°882° 1:130° Antepenult leaves, . Ono 78 en *1°132° ° % . ~ a : c 1 The figures given in this column are the means obtained in these series of experiments recorded in a previous paper (Dixon and Atkins, 13). : 432 Scientific Proceedings, Royal Dublin Society. Similar differences have been established for the sap extracted by means of liquid air from the roots, rhizome, and leaves of Iris germanica. They, too, have been found to be in the same sense as the differences in the saps from the untreated organs. The same holds good in regard to those of the roots and leaves of Eucalyptus globulus. It was also observed that the sap of the leaves of Hedera Helix grown in a south aspect had a greater depression than that of leaves in a north aspect, quite irrespective of which of the two methods of extraction was employed in the pair of comparative experiments. Of course the absolute values were very different. These results and others are recorded in a subsequent paper. BrsriioGRrAPHy, 1. Anpr&, G.: Sur la composition des liquides qui circulent dans le végétal, Comptes Rendus, 1906, 142, p. 106. Sur la composition des sucs végétaux extraits des racines. Comptes Rendus, 1906, 143, p. 972. 3. Sur la composition des sucs végétaux extraits des tiges et des feuilles. Comptes Rendus, 1907, 144, p. 276. 4, Sur la migration des principes solubles dans le végétal. Comptes Rendus, 1907, 144, p. 383. . Arxins, W. R. G.: Cryoscopic Determinations of the Osmotic Pressures ofsome Plant Organs. Proc. Roy. Dubl. Soc., vol. xii (N. S.), No. 34, 1910, p. 463; and Notes from the School of Botany, ‘l'rinity College, Dublin, 1910, vol. ii, No. 2, p. 84. 6, Cavara, F.: Influenza di minime eccezionali di temperatura sulle piante dell’ Orto botanico di Cagliari. Bol. Soc, Bot. Italiana, 1901, p. 146. Risultati di una serie di ricerche crioscopiche sui vegetali. Con- tribuzioni alla biologia vegetale, iv, 1905, p. 1. . Drxon, H. H.: On the Osmotic Pressure in the Cells of Leaves. Proc. Roy. Irish Acad., vol. iv, ser. 3, 1896, p. 61; and Notes, Bot. Sch. T.C.D., vol. i, No. 2, p. 44. A. Thermo-electric Method of Cryoscopy. Proc. Roy. Dubl. Soe., vol. xiii (N. S.). No. 4, 1911, p. 49; and Notes, Bot. Sch. T.C.D., vol. ii, No. 8, p. 121. 10. Drxon, H. H., and W. R. G.-Arxins. On Osmotic Pressure in Plants. Proc. Roy. Dubl. Soc., vol. xii (N. S.), No. 25, 1910, p. 275; and Notes, Bot. Sch. ‘.C.D., vol. ti, No. 2, p. 47. or is) 12. 13. 14, Drxon anp AtTKiIns— Osmotic Pressures in Plants. 433 . Drxon, H. H., and W. R. G. Arxins. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. Proc. Roy. Dubl. Soc., vol. xiii (N. S.), No. 16, 1912, p. 219; and Notes Bot. Sch. T.C.D., vol. ii, No. 3, p. 99. Variations in the Osmotic Pressure of the Sap of Hedera Helix. Proc. Roy. Dubl. Soe., vol. xiii (N. 8.), No. 19, 1912, p. 239; and Notes, Bot. Sch. T.C.D., vol. ii, No. 3, p. 103. —— Variations in the Osmotic Pressure of the Sap of Ilex Aquifolium. Proc. Roy. Dubl. Soc., vol. xiii (N. S.), No. 18, 1912, p. 229; and Notes, Bot. Sch. T.C.D., vol. ii, No. 3, p. 111. Heap, F. Dz Forssr: The Hlectrical Conductivity of Plant Juices. Bot. Gaz., 1902, vol. xxxiv, and Science (N.8.), vol. xv, 1902, p. 457. . Manig, C. H., and C. L, Garin: Determinations cryoscopiques effectuées sur des sucs végétaux. 1912. . Maximow, N. A.: Chemische Schutzmittel der Pflanzen gegen Erfrieren, i, Ber. d. Deutsch. Bot. Gesell. xxx, 2, 1912, p. 52. 17, —— —— —— ii, ibid., xxx, 6, 1912, p, 293. 18, —— —— Ui, ibid., xxx, 8, 1912, p. 504. 19 20. . Nicotost-Roncati, F.: Ricerche su la conduttivita elettrica e la pressione osmotica nei vegetali. Bol. dell’ Orto bot. della reale Univ. di Napoli, 1909, Tomo ii, Fase, 2, p. 205. della Salpichroa rhomboidea (Miers). reale Univ. di Napoli, Tomo ii, p. 473. Bol. dell’ Trincuiert, G,: Su le variazioni della pressione osmotica negli organi Orto bot. della 21. Surnerst, W. F.: The Freezing-Point of Vegetable Saps and Juices. Chemical News, 1901, p. 234. SCIENT. PROC. R.D.5., VOL. XIII., NO. XXVILI. aa tees ; ei i We 4a Fie SDE REO EEA ESS) j; i rele A ees Uh Ph ped Ty he Weaken oe AVI HY ISPS GUNNS — 10. 11. 12. 13. 14. 15. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). |By T. Jonson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. . 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By James Witson, m.a., B.Sc. (December 18, 1912.) 1s. 6d. Osmotic Pressures in Plants. I.—Methods of Extracting Sap from Plant Organs. By Hryry H. Drxon, sc.p., F.R.s., and W. R. G. Arxins, m.A., A.1.c. (February 8, 19138.) Is. Osmotic Pressures in Plants. I1.—Cryoscopic and Conductivity Measurements on some Vegetable Saps. By Henry H. Drxon, sc.p., r.r.s., and W. R. G. ATKINS, M.A., Ac. (February 8, 1913.) 6d. DUBLIN: PRINTED AT THE UNIVERSITY PRESS BY PONSONBY AND GIBKS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 29. FEBRUARY, 1918. OSMOTIC PRESSURES IN PLANTS. IJ.—Cryoscoric anD Conpuctiviry MEASUREMENTS ON SOME VEGETABLE SAPs. BY HENRY H. DIXON, Sc.D., F.R.S., UNIVERSITY PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN ; AND W. R. G. ATKINS, M.A., A.LC., ASSISTANT TO TUE PROFESSOR OF BOTANY, TRINITY COLLEGE, DUBLIN. | Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBUIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price Sixpence. Roval Bublin Society. a a ee FOUNDED, A.D. 1731. INCORPORATED, 1749. ——S ES EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be get down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Lllustrations im a complete form, and ready for transmission of the Editor. 12. Dixon anp ArKins—Osmotic Pressures in Plants. 433 . Dixon, H. H., and W. R. G. Arxins. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. Proc. Roy. Dubl. Soe., vol. xiii (N. S.), No. 16, 1912, p. 219; and Notes Bot. Sch, I'.C.D., vol. ii, No. 3, p. 99. Variations in the Osmotic Pressure of the Sap of Hedera Helix, Proc. Roy. Dubl. Soc., vol. xiii (N. 8.), No. 19, 1912, p. 239; and Notes, Bot. Sch. T.C.D., vol. 11, No. 3, p. 108. - Variations in the Osmotic Pressure of the Sap of I/ex Aquifolium. Proe. Roy. Dubl. Soe., vol. xiii (N. S.), No. 18, 1912, p. 229; and Notes, Bot. Sch. T.C.D., vol. ii, No. 3, p. 111. . Heatp, F. De Foresr: The Electrical Conductivity of Plant Juices. Bot. Gaz., 1902, vol. xxxiv, and Science (N.8.), vol. xv, 1902, p. 457. sur des sucs végetaux. 1912. 5. Mariz, C. H., and C. L. Garin: Determinations cryoscopiques effectuées 16. Maximow, N. A.: Chemische Schutzmittel der Pflanzen gegen Hrfrieren, i, Ber. d. Deutsch. Bot. Gesell. xxx, 2, 1912, p. 52. 20. 21 —— —— —— ii, ibid, xxx, 6, 1912, p, 293. i, ibid., xxx, 8, 1912, p. 504. . Niconost-Roneatt, F.: Ricerche su la conduttivita elettrica e la pressione osmotica nei vegetali. Bol. dell’ Orto bot. della reale Univ. di Napoli, 1909, Tomo ii, Fase. 2, p. 206. della WSalpichroa rhomboidea (Miers), reale Univ. di Napoli, Tomo ii, p. 473. dell’ Orto bot. Trincutert, G.: Su le variazioni della pressione osmotica negli organi Bol. della . SutHerst, W. F.: The Freezing-Point of Vegetable Saps and Juices. Chemical News, 1901, p. 234. SCIENT. PROC, R.D.S., VOL. XIII., NO. XXVIII. poe] XXIX. OSMOTIC PRESSURES IN PLAN'S. II.—Cryoscoric and Conpbucriviry MerasurEMENTS ON SOME VEGETABLE SAPs. By HENRY H. DIXON, 8c. D., F.R.S., University Professor of Botany, ‘Trinity College, Dublin ; AND W. RR. G. ATKINS, M.A., A.C, Assistant to the Professor of Botany, Trinity College, Dublin. [Read Decemper 17,1912. Published Fesruany 8, 1913]. In the paper (6) preceding this one we have shown that the sap pressed from living untreated tissues does not give a true estimate of the concentration of that in the vacuoles of the cells of the organ before the application of pressure. Tn order to extract the sap from the cells without altering its concentration, it is necessary to render the protoplasmic membranes permeable. This we found might be effected by the application of liquid air, The discovery makes it clear that our former work and that of others who employed sap expressed from the living tissues for cryoscopic or electrical conductivity determinations require revision, and it becomes necessary to repeat our measurements of osmotic pressure, making use of sap pressed immediately after thawing from tissues frozen solid in liquid air. The first of these corrected observations are recorded in this and the preceding paper. The osmotic pressures tabulated were calculated from ireezing-points found by the thermo-electric method of eryoscopy described in earlier papers (1, 2). Specific electrical conductivities of the same saps were also measured. The object of this was to trace out what part of the total osmotic pressure of the sap was due to electrolytes, and how far such variations as were met with are due to changes in the electrolyte content. For the sake of comparison with the osmotic pressures, the conductivity measurements were made at 0° C also, Dixon anp Arrins—Osmotie Pressures in Plants. 435 It is needless to point out that there is no necessary connection between the osmotic pressure and the specific electrical conductivity, as the former depends on the total amount of solutes in the sap, and the latter on the amount of electrolytes alone. Determinations of the mean molecular weight of the sap solutes have been omitted, since, not only is the desiccation of the sap, which is necessary according to the usual method, very tedious, but also the presence of undetermined quantities of colloids leaves these estimates open to an error, which is probably only constant for each organ dealt with. Hence the electrical conductivities, although, as we shall see presently, open to another error, seemed more suitable for our present purpose. Measurements of the specific conductivity of plant juices have been made previously by other investigators, e.g., Heald (8) and Nicolosi-Roncati (9); the apparatus used in the present work differs in no essential respect from that used by Heald, viz., a Hamburger conductivity tube of 2-3 c.c. eapacity, a resistance box, a metre bridge with sliding contact, inductorium, and telephone. The whole was supplied to us by Messrs. F. Kohler, Leipzig. The constant of the tube was found by means of N/25 solution of potassium chloride. All measurements were made at 0° C, and according to the usual method described in Oswald’s Physico-Chemical Measurements, or Findlay’s Practical Physical Chemistry. The results are expressed as reciprocals of the resistances measured in ohms, not in Siemen’s units according to Hamburger’s custom (7). With regard to the values obtained for the conductivities of the saps, it must be pointed out that only those carried out on the same organ of each species are strictly comparable. Even here errors may be present. Such uncertainties are due to variations in the viscosity of the saps, owing to the various solutes and colloids which they contain. This is clearly brought out when comparative experiments are made on the conductivity of crude sap and of the same sap after filtering or centrifuging. In our determinations the saps used were first brought to conditions as uniform as possible, by filtering or centrifuging to remove the suspended matter. It may be noted that many saps gave a clear fluid when centrifuged, though they could not be easily filtered ; but, except in the case of very viscid saps, the difference in the conductivities after centrifuging and after filtering was found to be negligible. The centrifuge employed attained a speed of 9000 revolutions per minute, but even prolonged treatment at this speed failed to clear some pulpy juices. It was found that a speed of 3000-4000 revolutions per minute was quite ineffective where leaf-saps were dealt with. Heald’s observation of the close agreement of the conductivity of the sap 436 Scientific Proceedings, Royal Dublin Society. of an organ with the conductivity of the ash of the same organ dissolved in its proper volume of water appears to us to indicate that the error due to the presence of colloids is not in most cases serious. Thus it seems certain that, bearing these possible inaccuracies in mind, the conductivity measurements — give-a very fair picture of the changes going on in the electrolyte content during, for instance, the development of any organ, or over prolonged periods of its growth. Certain generalizations may also be obtained regarding the electrolyte content of various organs and plants. The results obtained up to the present on saps extracted from frozen organs are tabulated below and on the following page. Under A, P, and C are given the depressions of freezing-point in degrees centigrade, the osmotic pressures in atmospheres, and the specific conductivities, respectively. TABLE oF ReEsutts. Tee Description of Sample. | A | P C x 105 525 | Allium Cepa, bulb, Nov. 27, - 5 3 0-935 | 11-26 214 542 | Apium graveolens, base of etiolated leaves, Dec. 5, 1:302 15°66 1141 | aa Beta vulgaris, root, Nov. 26, - : 5 1-206 | 14°51 383 551 ¥ », Dec. 12, . : 1761 | 21-18 555 524 Brassica Rapa, white root, Nov. 27, - 1127. | 13°55 356 526 Cerasus Laurocerasus, leaves, Nov. 28, : 1522 | 18-31 321 527 Chamaerops humilis, mature leaf, Nov. 28, . 1-424 | 17-13 984 | 633 6 », leaf just expanded, Noy. 29, 1°598 19°22 977 | 534 aS ~,, leaf 2 years old, Nov. 29, 1:431 17°21 811 539 " ae a yee Go| ep | eo |) a 554 90 an 7" = Dec. 12, TS ol8225) 926 513 Citrus Aurantiun, fruit, Noy. 22, . 5 1:206 | 14°51 208 519 5, Limonum, ,, Nov. 25, 1:089 | 13°10 345 528 Cordyline australis, leat, Noy. 28, TG el 3 243 939 499 Lquisetum telmateia, rhizome, Noy. 16, 5 0:597 | 7:19 822 5382 Eucalyptus Globulus, mature horizontal leaves, : Noy. 29, 0-970 11°68 814 540 oF », roots 1-4 mm. dia., Dec. 5, 0°591 811 723 489 © Hedera Helix, \eaves N. aspect, Noy. 12, . 122395 5 14590) 545 530 53 bi ee Novi? 9 ane 1-289 | 15-o1 533 544 50 99 45 Dec. 9, : 1:171 14:09 596 474 y , S.aspect, Nov. 4, . | 1261 | 1617 | 507 | Dixon anp ArKins—Osmotic Pressures in Plants. 437. TABLE oF Resunrs—continued. Ne O: Description of Sample. | A | P © x 10° | xpt A Alege | 477 Hedera Helix, leaves 8. aspect, Nov. 4, | 1-239 14:90 5d8 | 490 i 55 a N@we I, ||. SOS) 15-74 556 493 ‘ ax 3 HCN GIRTIRT hoe 1°315 15-81 | 562 | 529 4 i ~ Nova29; | 1487 | 17-29 512 | 543 i ee a Dec. 9, | 1-989 | 15°51 ml || 520 Helianthus tuberosus, tuber, Noy. 26, 2 | 1-120 | 13°48 | 596 | | 485 Ilex Aquifoliwm, leaves, new ultimate, Nov. 8, | 1-072 | 12:89 | 428 487 a i penultimate, Nov. 8, | 1-130 13°60 | 619 488 99 » antepenultimate, Noy. 8, 1132) 13°62 731 501 a ean leaves, antepenultimate, Noy. 19, 1:244 15:08 696 503 ,», leaves, proantepenultimate, Noy. 19, 1:305 | 15°70 844 535 99 nA new ultimate, Dec. 4, 1:218 14°65 427 536 Ps 99 antepenultimate, Dec. 4, 1:259 15°14 730 484 ,», roots less than 3 mm. diam., Nov. 8, 0°682 | 8-21 629 504 Ree », 1mm, diam., Noy. 19, 0:635 “| 7-64 596 505 Reh 1-4 mm. diam., Nov. 19, 0°858 10°32 613 537 are 1-4mm. diam., Dec. 4, 0:862 10°38 603 498 Iris germanica, leaves, bases, Nov. 15, : 1-084 13°04 776 497 tt 3 green tops, Noy. 15, . 1-085 13°05 726 495 { “A rhizome, Noy. 15, : : 0°829 9:97 335 496 ss roots, Nov. 15, F : 0°764 9°20 786 522 Lycopersicum esculentum, fruit, Novy. 26, : 0-731 8°79 457 548 Monstera deliciosa, leaf, Dec. 10, 5 5 0°552 6°64 574 546 Musa sapientum, ,, Dec. 10, 6 : 0:785 9-44 308 546 Passiflora quadrangularis, leaf, Dec. 10, 0 1-162 13°98 706 531 | Pinus Laricio, leaves one year old, Noy. 80, . 1:289 15°50 848 541 | Pleris aquilina, rhizome, Dec. 5, . 3 0°929 11:18 807 611 | Pyrus Malus, fruit, Nov. 22, . : ‘i 1:919 23°18 161 547 | Saccharum officinarum, leaf, Dec. 10, . : 0-484 | 5°83 772 515 Solanum tuberosum, tuber, Nov. 22, . A 0°588 7:08 583 523 | Vaccinium Oxycoccus, fruit, Nov. 27, . 0 1°556 18-72 176 517 | Vitis vinifera, fruit, Noy. 25 E : 3°185 38°32 112 Discussion of Resuits. Our previous work on the determination of osmotic pressures in plant- organs was primarily undertaken to ascertain whether they are sufficient for 438 Scientific Proceedings, Royal Dublin Society. the requirements of the cohesion theory of the ascent of sap. Even then the values obtained were, in all cases, ample. Now, the newer and more accurate figures tabulated above show that our earlier estimates were too low, and hence that the actual osmotic pressures in the cells are much greater than that demanded by the theory. A survey of the table shows that the range of the osmotic pressures observed in the saps extracted by the liquid-air method is as large as that recorded by us and others for those obtained from the untreated organs. ‘he highest, so far observed, is that for the fruit of Vitis vinifera, viz., 38°32 atm. (A = 3:185°), and the lowest for the leaf of Saccharum officinarum, viz., 5°83 atm. (A = 0°588°). The following abstracts show in what plants the maxima and minima for the various organs have been found, and also record the values ascertained. Our previous determinations have, however, given us higher values in several instances. We now know that even these were underestimates. No. of | : | | P.in | Expt. Maximum. | A | TNn | d51 Root, Beta vulgaris, . : : 1:761° | 21°18 520 Rhizome or tuber, Helianthus tuberosus, | 1:120° | 13:48 | 533 Leaf, Chamaerops humilis, : Se elco9 Se | 19°22 | 917 Fruit, Vitis vinifera, . | 81852 | 38°32 | Tene | Minimum. A | 12 540 Root, Lucalyptus Globulus, : a ORG || Boil 515 Rhizome or tuber, Solanwm tuberosum, . 0°588° 7:08 547 Leaf, Saccharwin oficinarwn, x Y 0-484° 5°83 522 | Fruit, Lycopersiewm esculentum, . i 0°731° 8°79 Reference to the table of results will show that the leaves of Hedera Helix, taken from a north aspect, have on the average a smaller depression of freezing- point (1°238°, mean of three observations) than those taken from a south aspect (1°308°, mean of six observations). A similar difference had been found for the untreated leaves. Again, just as in the case of the untreated leaves of [lew Aquifolium, those frozen in liquid air showed a concentration of their sap with age. In the same way the general trend of the results obtained by the use of sap extracted by the old method (2, 3, 4, 5) has been confirmed by the observations made on that from organs treated with liquid air. Thus, it will be seen that in the same plant, e.g., Ziis germanica, the osmotic pressure in the root is less than that in the rhizome, while the pressure in the latter Dixon anp Atkins—Osmotic Pressures in Plants. 439 is less than that in the leaves. Of course, the actual figures obtained by the new method are higher than those obtained by the earlier one. It also appears that this gradation from below upwards may be, in some cases, extended, for we find that the finer roots of Ilex have a lower osmotic pressure than the thicker ones, and the bases of the leaves of Iris have a slightly lower pressure than the tops. With regard to the seasonal changes in Hedera, Ilex, and Syringa, studied in our former papers, we have not yet had time to measure the variations over any prolonged period, but so far as the present results go they confirm in a general way those obtained before. It is possible that the fluctuations in the yearly curve of pressures will be less irregular now that the uncertainty in the manner of extraction is removed. The specific conductivity measurements of the saps examined are of the same order as that of N/25 or 0°3 per cent. solution of potassium chloride. They range between 112 x 10° and 1141x10-°. With regard to the relative magni- tudes some very surprising results have been obtained. Fruits were found to have quite low values in spite of their known large content of malic, tartaric, or citrie acid. These, it is true, are not strongly disscciated acids, and evidently their effect is not nearly so marked as that of salts, organic and inorganic, - where they occur, for the salts of even very weak acids are strongly dissociated. Heald, as was noted before, found a remarkable parallelism between the conductivity of the sap and that of the dissolved ash from the same organ. This establishes the small influence of organic salts and acids on the conductivity, aud gives indirect evidence, as it seems to us, of the smallness of the error due to viscosity. The maxima and minima of the observed specifie conductivities for the sap of different organs appear from the following abstract :— No. of | ¢ : : ep | Maximum. | © x 10° | | 496 Root, Lris germanica, : ; 0 786 499 Rhizome or tuber, Egwisetwm telmateia, . $22 542 Leaf, Apiwm graveolens, . c . 1141 522 | Fruit, Lycopersicum esculentum, : 457 | nee | Minimum. C x 10° 524 Root, Brassica rapa, F : P 356 | 495 Rhizome or tuber, Tris germanica, c 335 546 Leaf, Musa sapientum, . : c 303 517 Fruit, Vitis vinifera, 2 : é 112 440 Scientific Proceedings, Royal Dublin Society. Various questions which are raised by the results of the new method of obtaining sap from vegetable tissues are at present being studied, and it is hoped that soon material will be at hand enabling us to deal with some of them. a BIBLIOGRAPHY. . Dixon, H. H.: A Thermo-Electric Method of Cryoscopy. Proc. Roy. Dubl. Soc., vol. xiii (N.S.), No. 4, 1911, p. 49; and Notes Bot. Sch. Trin. Coll., Dubl., vol. 11, No. 3, p. 121. . Dixon, H. H., and Avkins, W. R. G.: On Osmotic Pressures in Plants. Proe. Roy. Dubl. Soe., vol. xii (N.S.), No. 25,1910, p. 275; and Notes Bot. Seh. T.C.D., vol. ui, No. 2, p. 47. . —— —— Changesin the Osmotic Pressures of the Sap of Syringa vulgaris. Proce. Roy. Dubl. Soe., vol. xiii, No. 16, 1912, p. 219; and Notes Bot. Sch. T.C.D., vol. ii, No. 3, p. 99. Variations in the Osmotic Pressure of the Sap of Hedera Helix. Proc. Roy. Dubl. Soe., vol. xiii (N.S.), No. 19, 1912, p. 289; and Notes Bot. Sch. T.C.D., vol. 11, No. 3, p. 103. . —— —— Variations in the Osmotic Pressure of the Sap of Ilex Aquifolium. Proce. Roy. Dubl. Soe., vol. xiii (N.S.), No. 18, 1912, p- 229; and Notes Bot. Sch. T.C.D., vol. ii, No. 3, p. 111. Osmotic Pressures in Plants. I. Methods of Extracting Sap from Plant Organs. Proc. Roy. Dubl. Soe., vol. xiii (N.S.), No. 28, 1913, p. 422. . Hampureer: Osmotischen Druck and Ionenlehre. Wiesbaden, 1902. . Heatp, F. Dz Forest: The Electrical Conductivity of Plant Juices. Bot. Gaz., 1902, vol. xxxiv; and Science (N.S.), vol. xv, 1902, p. 457. . Nicotosi-Roncati, F.: Richerche su la conduttivita ellettrica e la pressione osmotica nei vegetali. Bol. dell’ Orto bot. della reale Univ. di Napoli, 1909, Tomo 11, Fase. 2, p. 473. 1. ri 10. 11. 12. 13. 14. 15. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Ivish Pteridosperm, Crossotheca Honinghausi, Kidston (Lyginodendron oldhamiwm, Williamson). [By T. Jonson, D.sc., F.L.S. (Plates I.-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorecr H. Peruysriver, B.sc., PH.D. (March, 1911.) 1s. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wiou1am Brown, B.se. (April 15, 1911). 1s. . A Thermo-Hlectric Method of Cryoscopy. By Henry H. Dixon, sc.p., F.x.s. (April 20, 1911). 1s. . A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wrouram J. Lyons, 8.a., a.R.c.sc. (Lonp.). (May 16,1911). 6d. 6. Radiant Matter. By Joun Jony, sc.p., r.r.s. (June 9, 1911.) 1s. . The Inheritance of Milk-Yield in Cattle. By James Wiuson, m.a., B.Sc. {June 12, 1911.) 1s. . Is Archeopteris a Pteridosperm? By T. Jounson, p.sc., r.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermakt, Stur, and of other Species of Archeopteris in Ireland. By T. Joayson, p.sc., ¥.u.s. (Plates VIL., VIII.) (June 28,!1911.) 1s. Award of the Boyle Medal to Proressor Joun JoLy, M.A., SC.D., F.R.S. (July, 1911.) 6d. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Joun Jony, sc.p., ¥.x.s., and Louis B. Smyrx, z.a. (Plate IX.) (August, 1911.) Is. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks., By E. A. Newsnn Arper, M.A, F.LS. F.G.S. (January, 1912.) 1s. Forbesia cancellata, gen. et sp. nov. (Sphenopteris, sp., Baily.) By T. JoHnson, D.sc., F.u.S. (Plates XIII. and XIV.) (January, 1912. 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Wiusov, M.A., B.SC, (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Portok, p.sc. (Plates XV. and XVI.) (February 21,1912.) 1s. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. SCIENTIFIC PROCKEDINGS—contnued. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris., By Henry H. Dixon, sc.p., ¥.r.s., and W. R. G. Arxins, M.A. (February 21,1912.) 6d. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, FR. (Plates XVII.-XIX.) (March 26, 1912.) 1s. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Dixon, sc.p., r.z.s., and W. R. G. Arxins, m.a., a.1.c. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Drxov, sc.p., F.n.s., and W. R. G. Arxins, m.a., a.t.c. (April 9,1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jounsoy, p.sc., r.u.s. (Plates XX. and XXI.) (April 12, 1912.) 1s. On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part IT.—lLead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By James H. Pornox, D.Sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s. The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Copper, and Lithium. By Genrvinve V. Morrow, A.R.C.Sc.1. (Plate XXIV.) (May 11,1912.) 1s. Award of the Boyle Medal to Sir Howarp Gruss, r¥.r.s., April 16, 1912. (May 18, 1912.) 6d. Notes on Dischidia rafflesiana, Wauu., ano Dischidia nummularia, Br. By A. F. G. Kerr, mp. (Plates XXV.-XXXI.) (September 30, 1912.) Qs. Recherches Expérimentales sur la Densité des Liquides en dessous de 0°. Par Jean Timmermans. (October 18, 1912.) 3s. Steady and Turbulent Motion in Gases. By Joun J. Downie, u.a. (Plates XXXII. and XXXII.) (November 16,1912.) 1s. 6d. Unsound Mendelian Developments, especially as regards the Presence and Absence Theory. By James Wison, m.a., B.Sc. (December 18, 1912.) 1s. 6d. Osmotic Pressures in Plants. I.—Methods of Extracting Sap from Plant Organs. By Hryry H. Drxon, sc.p., F.z.s., and W. R. G. Arxins, M.A., A.1.C. (February 9, 1918.) 1s. Osmotic Pressures in Plants. II.—Cryoscopic and Conductivity Measurements on some Vegetable Saps. By Henry H. Drxon, sc.p., F.r.s., and W. R. G. Arxins, M.A., A.c. (February 9, 1913.) 6d. DUBLIN: PRINTED AT THE UNIVERSIULY PRESS BY ’ONSONBY AND GIKKS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 30. FEBRUARY, 1918. A METHOD OF MICROSCOPIC MEASUREMENT. BY I, JOY, Seid, TRS, PROFESSOR OF GEOLOGY AND MINERALOGY IN THE UNIVERSITY OF DUBLIN. [Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBUIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. — Price Sixpence. | Roval Bublin Society. I ce FOUNDED, A.D. 17381. INCORPORATED, 1749. —~ EVENING SCIENTIFIC MEETINGS. Tar Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. ee | XOOK, | A METHOD OF MICROSCOPIC MEASUREMENT. 1B do MONG CDRS IMIR Professor of Geology and Mineraology in the University of Dublin. [Read December 17, 1912. Published Fesruary 7, 1913.] Recentiy having to measure the diameter of some small objects in a rock- slice, I was led to use the following method :— Two fine lines are drawn with a drawing-pen in indian ink on a piece of white paper. The lines meet at a point, and very slowly diverge. In this particular case the separa- tion of the lines was about 5 millimetres at a distance of 10 centimetres from the point of intersection. The camera-lucida is placed in position, and the image of the object under the microscope referred in the usual manner to the sheet of white paper. The paper is then shifted till the object appears to fit exactly between the lines. While still looking at the object a mark is made with a pencil across the lines just where the object is referred. An engraved scale, divided to 0°01 of a millimetre, is now substituted for the object, and a few—say, n—of the sub- divisions brought by the camera-lucida to fit—as before— between the lines. This point is marked on the paper as before. The diameter of the object is now found by measuring the distance d; from the intersection of the lines at which the first pencil-mark was made, and the distance d, at which the second pencil-mark wasmade. Thisis done simply by measure- ment with a millimetre scale. Then the diameter, z, of the object is evidently found from the proportion 37 33 Oh 2 Gh, This method is quicker and more accurate than endeavour- ing to draw the object by the use of the camera-lucida, and then measuring the drawing. It is, 1 found in my own case, more consistent in successive measurements than the micrometer eye-piece, and of course, the only apparatus required is the camera-lucida. SOIENT. PROO. R.D.S., VOL. XII., NO. XXX. 3U 442 Scientific Proceedings, Royal Dublin Society. The sensitiveness of the method is evidently controlled by the amount of divergence given to the lines. In the case of objects of sharp definition a small divergence may be used; in the case of objects of inferior definition it is better to use a larger angle of divergence. I venture to draw attention to the method, as I have nowhere seen it described, obvious as are its principles. IvEacuH Grouocican Lasoratory, TrinityCotiece, Dustin. — SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearine Irish Pteridosperm, Crossotheca Honinghausi, Kidston (Lyginodendron oldhamiwm, Williamson). |By T. Jounson, D.sc., F.L.s. (Plates I-III.) (March, 1911.) Is. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcr H. Prruysriner, B.sc., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wiu1am Brown, B.so. (April 15, 1911). 1s. A Thermo-Hlectric Method of Cryoscopy. By Hunry H. Dixon, so.p., F.r.s. (April 20, 1911). 1s. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. 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FEBRUARY, 1913 THE MELTING-POINTS OF SOME OF THE RARER MINERALS. BY ARNOLD L. FLETCHER, M.A., B.E., RESEARCH ASSISTANT TO THE PROFESSOR OF GEOLOGY AND MINERALOGY IN THE UNIVERSITY OF DUBLIN. [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRJETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price One Shilling. Roval Bublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749. HVENING SCIENTIFIC MEETINGS. Tue Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested +o forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Llustrations in a complete form, and ready for transmission of the Editor. “ey XXXII. THE MELTING-POINTS OF SOME OF THE RARER MINERALS. By ARNOLD L. FLETCHER, M.A., B.E., Research Assistant to the Professor of Geology and Mineralogy in the University of Dublin. [Read NovemBer 26, 1912. Published Fesruary 15, 1913.] A more accurate knowledge of the actual fusion-points of minerals is the more necessary when it is remembered that the scale of Von Kobell is not only inaccurately spaced, but out of order.’ The effect of judging by this method has been to assign, for example, to Augite, Titanite, and Vesuvianite melting-points in the scale of fusibilities of 3, or about 1320° C., whereas their temperatures of fusion (Cusack”) corrected are approximately 1240° C., 1180° C., and 1080° C. respectively. Again, many minerals regarded as infusible BB fuse in reality in the neighbourhood of 1800° C., i.e. below Almandite, No. 3 in the scale, which melts at about 1315°C. Such examples could be multiplied. The determination of the melting-points of minerals as one of the uses of the meldometer has been emphasized, and the fusion-points and behaviour under high temperatures of some minerals recorded in the original paper.® The subjective method of the determination of melting-point by direct observation under the microscope of the rounding or flowing of minute particles has been used by other observers,* though usually under somewhat different conditions from those under which the present determinations were made, and the resistance of a platinum wire has also been used as a measure of its temperature.° 1 Joly, Proc. Roy. Irish Acad. 3rd Series, yol. ii, 1891, p. 29, e¢ seg. 2 Cusack, Proc. Roy. Irish Acad., 3rd Series, vol. ivy, 1897, p. 408. 3 Joly, ibid., p. 48. 4 Doelter, Zeit. Elektrochem, vol. xii, 1906, p. 617, e¢ seg. Marius van Ledden Hulsebosch, Zeit. Anal. Chem. 1897, xxxvi, p. 685. Douglas, Quart. Journ. Geol. Soc., vol. xii, 1907, p. 145. 5 Burgess and Holt, Proc. Roy. Soc., vol. Ixxiv, 1904, pp. 285-295. SCIENT. PROC. R.D.S., VOL. XIII., NO. XXXI. 3X 444 Scientific Proceedings, Royal Dublin Society. ‘The principle of the following method has been described by Prof. Joly in his original paper.! The accompanying illustrations slaty the latest design of the instrument :— Fig. 2.—Diagram of the essential parts of the Joly Meldometer. (Reproduced by permission of the Cambridge Scientific Instrument Company. ) The platinum ribbon, which is conveniently from 2mm. to 4mm. in breadth, is held between the forceps CC (fig. 2), which allow it to lie accurately 1 Loc. cit. Frercrnr—The Melting-Points of some of the Rarer Minerals. 445 along the axis of a tubular draught-shield #. A slight tension is exerted on the forceps by the spring at D, sufficient to keep the ribbon taut without producing permanent extension at unduly low temperatures. One forceps is produced in a flexible arm G, which by completing an auxiliary circuit at the point P of a graduated micrometer screw H serves to record the extension, and hence the temperature of the strip. A small electro-magnet 7 indicates by an arm, which enters the field of vision through a slot in the tube of the microscope, the precise moment at which the auxiliary circuit is complete and contact made. The great advantage of this method of temperature measurement is that, by following up the flexible extension of the forceps with the micrometer screw, the temperature at the exact moment required is recorded; and sudden small changes in the temperature, brought about by draughts or small variations in the resistance, are very easily remedied by a rapid motion of the screw-head. The needle of the electro-magnet is dead beat, and therefore facilitates rapid and accurate measurement. A particle of the substance to be examined is put near the centre of the platinum, and observed by the low-power microscope shown, which has a motion parallel to the strip. Curve of Thermal Extension of Platinum Ribbon. With regard to the curve of thermal extension upon which the temperatures are determined by interpolation (fig. 3), the points were decided only from the results of the most consistent experiments. It is not necessary to plot a fresh curve for each new platinum ribbon as it is usually found that they are coincident from one ribbon to another, when care is taken to cut each fresh strip after the exact pattern of the standard on which the curve was originally determined. On using a new ribbon it was found sufficient for tle purpose of verification to re-determine two points by melting, say potassium carbonate and metallic palladium. ‘The curve reproduced shows the increase in the coefficient of expansion with temperature, and the evenness of its slope is some additional assurance of its accuracy. It was not considered necessary in these experiments to make allowances for diurnal differences in the temperature of the laboratory. The standard determinations should be made upon purified substances ; ordinary laboratory chemicals will be found to give fusion points differing from those of the purified samples. The following substances of guaranteed purity were used in determining 3x 2 Extension. 446 Scientific Proceedings, Royal Dublin Society. the standard curve. For the lithium silicate I am indebted to Messrs. A. L. Day and R. B. Sosman of the Geophysical Laboratory at Washington :— Melting- Point in Substance. Degas Gein ante Authority. Potassium nitrate (c) 345 Kaye and Laby. Barium nitrate 575 Kaye and Laby. Silver sulphate (c) 660 Kaye and Laby. Sodium chloride 801 Harker. Silver 960 Day and Sosman. Gold 1062 Day and Sosman. Potassium sulphate 1070 Kaye and laby. Lithium silicate 1201 Day and Sosman. Nickel 1452 Day and Sosman. Cobalt 1490 Day and Sosman. Palladium 1549 Day and Sosman. : © Pt (approx), 300 500 700 900 00 1300 1500 1700 Fig. 3. Degrees Centigrade. Fiercurr—The Melting-Points of some of the Rurer Minerals. 447 There is some difficulty in obtaining a suitable substance the melting-- point of which lies between that of lithium silicate (1201°C.) and metallic palladium (1549° C.) for the verification of this important region of the curve of extension, the oxidation of metallic nickel at high temperatures in air rendering this substance unsuitable under ordinary conditions. A close approximation to its melting-point was made by heating the nickel in an atmosphere of CO, obtained by passing a very slow current of this gas from a wide nozzle along the draught guard. Behaviour of Substances on the Meldometer. Change of colour before melting :—Colour-changes which are best observed with the naked eye are conveniently seen on platinum, using a small heap of fine powder. The rapidity with which the ribbon may be heated or cooled renders more obvious slight changes in tint, which might be imperceptible with slower temperature-variations. ‘his characteristic is especially useful in dealing with the colour-changes of minerals in borax or microcosmic salt beads. Chemical changes :—Oxidation, reduction, and combination with the heated platinum support, are frequently observed on heating minerals. Nickel and cobalt are examples of substances giving misleading indications owing to oxidation. ‘These elements do not show distinct signs of fusion below the melting-point of platinum, when they appear to liquefy. The solidified mass shows under the microscope bright green crystals of nickel oxide, resting in pits or hollows in the platinum, the surface of which is scooped out to receive them. In reality the nickel, without showing signs of fusion, has oxidized; and as the melting-point of planum is reached, the metallic support sheltered under the nickel particle, and _ possibly contaminated with nickel, liquefies, the observed fusion being due to platinum, and not to nickel. Cobalt behaves similarly, and yields the black oxide usually without preliminary fusion. The numerous stages at which melting occurs with copper or its oxides complicate the exact interpretation in this case. On heating cupric oxide, numerous particles fuse at about 1045°C., and the edges of larger specks are observed to melt in red streams. ‘The red stream of cuprous oxide probably represents the halo described by Mr. Cusack,! and involves partial reduction. Further fusions take place at temperatures between 1065° C0. and 1180°C. when the mass of cupric oxide melts; when cold, the border of red around the 1 Loe. cit. 448 Scientific Proceedings, Royal Dublin Society. black oxide is visible. If copper be heated, some particles melt at the fusion- point of cuprous oxide, and at the same time molten oxides may be seen flowing from smaller specks, representing partial oxidation; and, as the temperature rises, the copper may be observed to melt suddenly, and to become coated with a film of black oxide which rapidly liquefies. The true melting-point of copper cannot be obtained in this manner, owing to the formation and mutual solution of cuprous oxide and copper to form Cu — Cu,0 alloys with melting-points at temperatures below that at which copper melts.! Swiface-tension effects:—Melted copper oxide shows remarkable surface- tension effects with change of temperature; the edges of the fusion darting about in every direction in streamers which attach the platinum, leaving arborescent patterns visible in the cold. These effects are seen to a less extent with other substances and with some minerals. Brightness and Emissivity :—Some powders e.g., cassiterite and monazite, approximate in colour to the hot ribbon so as to be rendered nearly invisible’ when it is difficult to perceive indications of melting. Other substances, e.g., palladium, while difficult to see before melting, flash into view on assuming the molten condition, and so facilitate accurate measurement. The loss of emission-power which often occurs when a bright fusion is further heated is described in the table (p. 450) as “loss of body.” Glowing :—When certain sulphides are heated quickly to a temperature of about 700° C., the rapid oxidation which occurs causes incandescence. This does not occur with a slow rate of heating of over a few seconds’ duration, as when the powder is heated in a crucible, nor yet in the absence of free oxygen. Such glowing was observed in some earthy uraninites; and when such particles are spread through a powder they may be seen as individual momentary flashes of light. The melting-point :—Some substances such as silver melt “ easily,”’ that is, relatively large particles flash into the molten condition with obvious indications of the change. Others which melt ‘‘ with difficulty ” assume the fluid state, even with small particles, so slowly as to defy accurate observation. In these cases the iridescence of the liquid may be the first indication that melting has occurred. Such bodies show no rounding of the corners which may represent either softening or free melting of extreme angles and edges. The fusion may, as the temperature rises, flow more freely, or collect 1This phenomenon has been observed with nickel (Day, Sosman, and Allen, Amer. Jour. Sci., [4], vol. xxix, 1910, p. 137), where it was found that a sharp change in the melting-curve was obtained at a point 10°C. below the true melting-point of nickel in an atmosphere of hydrogen, and which may represent the formation of a Ni — NiO eutectic. FietcHer— The Melting-Points of some of the Rarer Minerals. 449 like oil, refusing to flow, depending upon prevailing conditions of surface- tension. In few of the minerals examined was the melting-point definite; that is to say, nearly all showed longer or shorter periods of fusion before complete liquefaction. The smallness of the particles ensures comparative freedom from errors due to conductivity, and renders unnecessary considerations of the latent heat of fusion. ‘lhe delicacy of the method reveals the lack of sharpness in the melting of complex minerals. It isimportant, as other observers have shown, to use only the finest powder, as experience shows that comparatively large particles of moderate fusibility may melt only on their undersides, and show no change under the microscope at high temperatures. With substances revealing more sharply defined optical changes, the temperatures may be obtained accurate to within one or two degrees. The following results are probably correct to 20°C. above or below ; approximations as close as was considered were required. Colour-change in glasses :—An interesting colour-change is to be observed in the glasses from certain minerals, especially tantalites. Melted tantalite, which is a glass, presents when cold varying shades of yellow according to the thickness of the enamel. When heated, this darkens in intensity to an extent depending on the specimen, and sometimes to opacity. When cooled slowly, the melt retains the darker colour-shade. On heating, however, to a certain temperature—usually a bright red—and suddenly cooling, the original lighter yellow tint is obtained. ‘his change may apparently take place indefinitely in the same glass. Production of sublimates:—In many cases the appearance has been described of a growing ring, often molten, collecting round particles at temperatures near their melting-points. Its first appearance is heralded by . a single speck, situated at some distance from the particle, which is rapidly joined by others as the temperature is raised until a definite peripheral ring is formed. This has also been observed with elements such as nickel and cobalt, the former furnishing a ring at about 1460°C.—its melting-point—which grows outwards and eventually disappears, and may be the deposition of a heavy vapour or sublimate on the cooler parts of the ribbon away from the particle. Reactions with fluxes:—With the meldometer substances may be con- veniently examined in presence of fluxes, and as only minute quantities need be used, colour tints are observable with smaller amounts than are necessary for an ordinary borax bead. Delicate tints are the more easily detected since rays reaching the observer have passed twice through the enamel by reflection 450 Scientific Proceedings, Royal Dublin Society. from the platinum. Enamels may be readily obtained in oxidizing and reducing atmospheres, and the colours produced examined at any temperature under progressive conditions of saturation from the centre to the point at which the colour fades away. Uraninite, for example, dissolves in a drop of microcosmic salt in air, yielding a greenish yellow-glass with tints varying from light yellow to deep orange when hot, from colourless to yellow when cold. In sodium carbonate uraninite powder disintegrates in a distinctive manner, producing finally a slag of mottled yellows and browns which remain unchanged on heating. ‘TABLE. (Temperatures in Degrees Centigrade.) FrvoripeEs. Vétrocerite (Finbo, Sweden) :—infusible below 1570. Vitrocerite (Finbo, Sweden, 1691)! :—infusible below 1510. ORTHOSILICATES. Zircon [Cyrtolite], (North Carolina):—Reddens blue litmus paper. Decomposes, yielding a sublimate at 1160, but does not flow freely below 1560. Thorite (loc. unknown) :—shows signs of melting at 1270 and flowing at 1420. Thorite [Orangite| (Arendal, Norway) :—is difficult to distinguish, probably fuses at 1255 and loses body, but does not flow freely below 1590. Thorite [ Uranothorite| (Risor, Norway) :—is difficult to distinguish. Melts at 1270, but does not flow freely below 1450. Gadolinite (Arendal, Norway):—reddens litmus paper, lightens in colour, and sometimes yields a white sublimate. Possibly melts at 1395, and certainly at 1450, showing iridescence and sublimation. The fusion, which first spreads over the platinum support in a meshwork, finally collects into globules. ; Risorite (Risor, Norway) :—softens and finally flows slowly at about 1720. Allanite (Saetersdalen, Norway):—reddens blue litmus. Softens and becomes bright below 1220, fuses at 1255 to a brown glass and flows readily with iridescence. The fusion shows on heating the colour- changes previously described. 1 Some of the specimens examined are from among those which have been described and identified by Prof. Apjohn in the ‘‘ Catalogue of the simple minerals in the systematic collection of Trinity College, Dublin,”’ to which the numbers refer. FrercHEr— The Melting-Points of some of the Rarer Minerals. 401 Allanite (Virginia, U.S.A.):—flows slowly at 1265 and freely at 1280. Allanite (Arendal, Norway) :—melts at about 1220, flows slowly at 1255 and readily at 1290. SUBSILICATKS. Cerite (K6ping, Norway):—becomes round and melts below 1370, but does not flow below 1600. ‘The glass is botryoidal and dark brown on thin edges. : Cerite (Bastniis, Sweden) :—possibly softens at 1230 and melts fairly easily at 1850 to a pale yellow glass, which darkens to opacity on heating to redness. TITANO-SILICATES. Titanite (Norway, 1744):—yreddens litmus and yields a white sublimate. Softens and melts readily to a rich brown glass at 1250, flowing at 1315 with iridescence. The fusion shows slight colour-changes on heating. Keithawite (Kragero, Norway) :—reddens blue litmus paper. Melts, showing sublimation, to a pale yellow glass at about 1110 and flows with iridescence. The fusion darkens slightly on heating. Niopares ann TANTALATES. Pyrochiore (Russia) :—yields a white sublimate. The powder, which is difficult to distinguish, shows sublimation in rings at about 1220, partially melts and flows very readily at 1340, and the remaining nucleus at 1425. ‘The fusion shows surface-tension effects and iridescence. Fergusonite (Ytterby, Sweden) :—Yields traces of a sublimate, whitens, and turns blue litmus red. Possibly softens at 1300, melts to a dark yellow glass, and flows with difficulty at 1510. Fergusonite (Norway) :—Softens at 1330, and flows freely at 1485. Columbite (Moss, Norway) :—powder turns brown on heating and reddens litmus. Melts at 1510 with iridescence, but does not flow freely. Segregates at 1400 into drops, showing surface-tension effects ; finally disappears. ‘The glass, which is brown on thin edges, tends to crystallize in radiate and sheaf-like needles on cooling. Columbite—(Warwick, New Jersey, 1763):—powder reddens and yields a vapour affecting blue litmus. Softens without flowing at 1500. Columbite (Arendal, Norway) :—melts, but does not flow freely at 1350. Wiikite (Impilati, Finland) :—possibly softens at 1250, and slowly melts at about 1885. SCIENT. PROC. R.D.S., VOL, XIII., NO. XXXI, ‘ 3 Y 452 Scientific Proceedings, Royal Dublin Society. Tantalite (Broddbo, Sweden, 1765) :—possibly rounds at 1240 and melts fairly easily at 1315, but less easily than the specimen from Copenhagen. The glass shows typically the colour-changes described. Tantalite (Finbo, Finmark, 1767):—turns grey on heating, and reddens litmus. Possibly rounds with signs of sublimation at 1290, and flows in iridescent films at about 1450. Tantalite (Middletown, Connecticut, 1764) :—shows signs of rounding with sublimation at about 1250, melts at 1340, and flows very freely with iridescence at 1410. Fusion tends to acicular crystallization on cooling. Tantalite (Kimito, Finland) :—fuses to a black glass at about 1470, which shows incipient crystallization on cooling. Tantalite (Copenhagen, 1766) :—reddens litmus, and melts easily at about 1210 to a glass which shows colour-change on heating. Vttrotantalite (Ytterby, Sweden) :—reddens blue litmus paper, whitens and shows signs of sublimation at about 1255. Melts with iridescence and flows at 1375. Yttrotantalite (Ytterby, Sweden, 1771) :—reddens blue litmus paper, whitens and shows signs of sublimation. Melts with iridescence and flows at 1315. Vttrotantalite (Finbo, Sweden, 1769) :—-reddens blue litmus, and whitens at about 13800. Melts with iridescence and flows at 1430. Samarskite (Mitchell Co. Carolina) :—powder, which is easily distinguishable, possibly softens, melts and flows easily at 1300 in iridescent streams showing surface-tension effects. The fusion shows incipient erystalliza- tion. Samarskite (Arendal, Norway) :—powder, which is bright on the hot ribbon, softens possibly at about 1830, and flows at 1360. FTielmite (Kerarfvet, Sweden):—signs of rounding in smallest particles at about 1340, melts and flows freely at 1435. Aeschynite (Hitteroe, Norway) :—reddens litmus paper, and yields a white sublimate, softens visibly at about 1270 with signs of sublimation, melts to a slag, and flows with difficulty at 1415, more easily at higher temperatures. Aeschynite (Saetersdalen, Norway) :—powder turns dark yellow on heating, and reddens litmus paper. Possibly fuses at 1305, and flows with difficulty at 1500. The glass shows the above-mentioned colour-changes. Aeschynite (IImengebirge, Ural) :—softens at 1245, and flows freely at 1420. Polymignite (Fredericksvarn, Norway) :—turns yellow, reddens blue litmus, and yields a white sublimate. Probably softens below 1400, but does not flow below 1550. ‘The fusion segregates into globules. Fiurcuer— The Melting-Points of some of the Rarer Minerals. 453 Euxenite (Saetersdalen, Norway) :—turns yellow, reddens blue litmus, and yields a white sublimate. Softens at about 1375, melts, and flows with iridescence at 1460. ‘The fusion shows surface-tension phenomena and incipient crystallization on cooling. Polycrase (Hitteroe, Norway) :—powder reddens blue litmus paper, and yields a white sublimate. Melts indistinguishably below 1420, and flows with iridescence at about 1560; the fusion coalesces into drops on cooling. PHOSPHATES AND ARSENATES. Monazite (Moss, Norway) :—reddens blue litmus paper, and shows signs of sublimation. Melting-point difficult to obtain. Particles “lose body ” at 1140, flow with iridescence at 1305, and eventually coalesce. Monazite (Arendal, Norway) :—melting unsatisfactory. Fuses with difficulty at about 1140, and flows at 1480. Monazite [ Turnerite], (Grisons, Switzerland) :—is infusible below 1480. Torbernite (Portugal) :—is easily distinguished on the ribbon, and yields a white sublimate. Melts below 1120, flows freely at 1330, and loses body. Torbernite (Marienbad, Bohemia) :—softens and flows at 1125. Torbernite (Joachimsthal, Bohemia):—softens and flows at 1125. Torbernite (Spain) :—softens and flows at 1125. Torbernite (loc. unknown) :—rounds possibly at 1050, and melts sharply at 1125, to a brown glass. Zeunerite (Schneeberg, Saxony) :—reddens litmus, and yields a white sublimate. Softens at about 1025, and melts rapidly with intumescence to a brown glass at 1080 without flowing. Shows signs of sublimation, and flows easily with intumescence at 1470. The fusion eventually becomes indistinguishable. Autunite (Sabugal, Portugal) :—darkens on heating, and melts sharply at 1110, flowing freely at 1255 with iridescence. The fusion shows surface- tension phenomena, coalesces at 1420, loses body, and solidifies to a slag. Autunite (Greenmont, U.S.A.) :—darkens temporarily on heating, and melts with intumescence at 1045, becoming bright. Flows with iridescence at about 1170, and solidifies to a brown glass, light yellow in thin section, darkening on heating. Autunite (Bohemia) :—softens and melts sharply at 1170. Walpurgite (Saxony) :—melts to a brown glass, and yields a white sublimate at 910. The fusion, which shows iridescence, coalesces into drops which finally lose body. By 2 4h4 Scientific Proceedings, Royal Dublin Society. URANATES. Uraninite (Sayda, Saxony) :—possibly softens at about 1220, flows slowly at about 1265, and rapidly at 1380. Uraninite (Johanngeorgenstadt, Bohemia) :—softens and melts with loss of ‘body at 1200, flows slowly with iridescence at 1330, and freely at 1440. Broggerite (Raade, Norway) :—turns brown at about 1170, yielding a white sublimate with a dull yellow centre. Softens in the neighbourhood of 1320, fuses to a brown glass, but does not flow freely up to 1480. Gummite (North Carolina):—reddens litmus paper at high temperatures. turning dark red-brown and partly regaining original colour on cooling. Appears bright upon the hot ribbon. Fuses at 1280, coalesces into drops, and solidifies to a dark brown glass. Gummite (Johanngeorgenstadt, Bohemia, 1814) :—small particles lose body and melt at 1300, larger ones fairly rapidly at 1490. Uranosphaerite (Sabugal, Portugal) :—reddens blue litmus. Melting difficult to observe. Small particles lose body at 1170 and larger particles melt with iridescence at 1320. Thorianite (alle, Ceylon) :—infusible below 1660. Uranochaleite (Bohemia) :—shows signs of sublimation, and possibly softens at 970; melts at intervals between 1110 and 1170 with decomposition, showing surface-tension effects. The fusion attacks the platinum. Zippeite (Schneeberg, Saxony) :—reddens blue litmus, is bright upon the hot ribbon, but, on heating, gradually loses body, and at 1250 partially disappears, leaving a fusion segregated in colourless drops. Uraconite (Schneeberg, Saxony) :—gradual rounding of the edges of smaller particles at 1050; flowing at 1070. Uraconite (Joachimsthal, Bohemia) :—glows on the ribbon, yielding a white sublimate at 1110, and reddening litmus. Melts to a brown glass, presenting incipient crystallization on cooling, and flows with iridescence, showing surface-tension effects. Recent advances in high-temperature measurement with the accompanying improvement in the accuracy of the standard temperatures render inaccurate results obtained in relation to old standards. iS Fiercurr—The Melting-Points of some of the Rarer Minerals. 445 The following represent the results obtained by Cusack! in 1897, corrected approximately to the standard temperatures quoted above :— SILICATES. Temperatures in degrees Centigrade. Br-SiicatTEs. Actinolite (green) Diallage A 1338 A 1314 B 1332 B 1850 C 1322 C 1328 D 1825 D 1334 E 1820 Tremolite Augite A 1273 A 1238 B 1269 B 1249 C 1237 Hornblende Spodumene A 1237 1223 B 1246 C 1250 Diopside Bronzite A 1237 1345 B 1242 Wollastonite C 1245 A 12538 B 1258 Unt-Sinicarrs. Olivine Meionite A 1428 1331 B 1413 Nepheline C 1422 A 1120 (Softens 1392) B 1109 Garnet (Almandite) Sodalite A 1314 A 1183 B 1318 18} alee C 1813 Leucite 1348 * Loc. cit. 456 Scientific Proceedings, Royal Dublin Society. Unt-SinicatEs—continued. Vesuvianite Adularia A 1074 A 1218 B 1085 B 1214 Epidote Albite A 1004 222; B 1026 Microcline. Goisite 1219 1045 Labradorite Dioptase A 1285 1221 B73 Axinite 1045 Sus-SILicaTEs. Tourmalines Titanite A 1068 A 1192 B 1062 B 1177 C 1118 Staurolite D 1152 1165 E 1063 Andalusite Cyanite 1259 1140 OXIDEs. Cuprite 1212 Brookite 1610 Zincite 1310 Uraninite 1288 Cassiterite 1177 Quartz 1475 Rutile 1610 (softens 1456) PHOSPHATES. Vivianite 1164 Apatite A 1271 B 1277 SULPHIDES. Galena 77 Iron Pyrites 692 (approx.) Zinchlende 1099 Marcasite 692 (approz.) Molybdenite 1235 Firrcurr— The Melting- Points of some of the Rurer Minerals. 4107 On the same basis the original figures obtained by Professor Joly would be for Von Kobell’s scale— Stibnite 530 Orthoclase 1225 Natrolite 1015 Bronzite (Diallage) 13850 Almandite 13815 Quartz 1480 (softens 1460) Actinolite 1346 and for the felspars— Adularia 1225 Microcline 1225 Oligoclase 1270 Labradorite 1280 Sanidine 1190 Albite 1225 Determination of Temperatures of Fusion on the Meldometer. The conditions pointed out by other observers which modify or determine the point of fusion of a mineral may be supposed to have been operative in these experiments. The most important of such conditions are the rate of fusion of the substance, and its purity. Joly,! Day, and others have shown that the time element is very largely operative in modifying the fusion temperatures of even pure substances. ‘These observers! have shown that in addition to the melting-temperature interval of impure substances there is a melting-time interval during which the substance, if left for a sufficient length of time, will fuse completely.? The determination of the lower temperature limit of such an interval may be impossible, and melting points therefore only approximate “on account of the sluggishness ” of the melting process. Fusion points, and especially those determined on the meldometer, hence represent “‘ the tempera- tures at which the change is rapid enough to be observable within a reasonable length of time.” Mixtures and solid solutions (covering the case of minerals) will not have melting-points but melting-intervals with definite temperature limits in which the substance will remain partially melted in equilibrium. In the present work no attempt was made to assign the limits of the melting-interval, as these must vary with composition, and hence with locality. They probably lie closer to the upper limit of the interval than to the lower. 1 Joly, Congrés Géologique Internationale, 1900. Comptes rendus, 1900, p. 689; also Sci. Proc. Roy. Dubl. Soe., vol. ix, 1900, p. 298. 0 2 Amer. Jour. Sci. (4), vol. xxxi, 1911, p. 185. See also Wegscheider (Chem. Zeit, 1905, vol. xxix, 1224), who points out that unless tempera- ture rise be rapid the melting-point obtained may be that of the mineral and its decomposition products. Cusack observed that witha sufficiently rapid rise of temperature certain minerals can be made to fuse before decomposing. 458 Scientific Proceedings, Royal-Dublin Society. The meldometer therefore, owing to the rapidity of its temperature-rise, should indicate higher fusion-points with minerals than those yielded by other methods, whereas the contrary is found to be the case, and moreover, the discrepancy in this direction should be accentuated owing to “the cohesion of some minerals at high temperatures which may permit of the liquefaction of a crystal without visible optical change.” The foregoing considerations have led various workers to somewhat discordant results. Doelter’s later investigations’ on some minerals which do not show much retardation in temperature-rise, and hence, according to him, are best treated subjectively, are in accordance with those obtained for the same minerals by Joly and Cusack (loc. cit.). ‘The conclusions of these observers are at variance with those of the workers in the Geophysical Laboratory at Washington, obtained by a non-subjective method, and supported in four cases by the meldometer.* These results are arranged in the following table® :— Jory.! Cusack.! Dorttrr. Day and orHEers. Dovetas. Albite 1225) 1222 1180-1215 1200° 1840 Oligoclase 1270 —— 1160-1240 1340 1367 1185-1275 nat. ra i 279 Labradorite 1280 1279 (mean) tee aes a 1477 1463 3 1255-13840 nat. H Anorthite —_ —— 1275-1350 ard. 1550 1532 Quartz 1480 1475 (melts) —— 1625 — Wollastonite —— 1255 (mean) 1220° 1540 — Diopside —— 1241 (mean) 1391 — It will be seen that the data of Joly and Cusack are in good agreement, and the results of Cusack on seventeen other minerals are so close to those of Doelter as to suggest that the corrections applied by the latter to some other minerals between 1902 and 1908 would bring them into complete harmony. In order to compare the above results with those presented in this paper, a number of experiments were carried out by me on the meldometer, using the foregoing minerals, and the figures of Cusack were substantiated. ‘The wide temperature-interval between, say, melting Palladium (1549) and Wollastonite 1 Zeit. Elektrochem., vol. xii, 1906, p. 617. 2 Douglas, Quart. Journ. Geol. Soc., vol. lxiii, 1907, p. 145. 3 See also Day and Allen, Amer. Jour. Sci. (4) vol. x, 1905. 4 Corrected approximately to recently published standards. > Rapid fusion. § Taschenb. Min. Mitth. vol. xxi, 1902, pp. 23-30. FiercHer—The Melting-Points of some of the Rarer Minerals, 459 as obtained by this method, placed side by side upon the meldometer ribbon and heated together, is evident. These wide differences are limited to certain specific cases of minerals, and melting-point standards obtained in a similar manner have agreed in producing an even slope in the foregoing curve of extension, fig, 8, p, 446. It is possible that the cause may be sought for in crystallographic changes (rather than in differences in purity) occurring only under certain conditions of observation, which might lead to varying results by methods so diverse as those used by different observers. I beg to record my thanks to Professor Joly for permitting me to continue his work on the meldometer. TyzacuH Gxotocicat Lasoratory, Trinity Coutece, Dusuin. November 26th, 1912. SOIRNT. PROC. 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THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 32. FEBRUARY, 1913. A REFINED METHOD OF OBTAINING SUBLIMATES. BY ARNOLD L. FLETCHER, M.A., B.E., RESEARCH ASSISTANT TO THE PROFESSOR OF GEOLOGY AND MINERALOGY IN THE UNIVERSITY OF DUBLIN. | Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIBTY, LEINSTER HOUSE, DUBLIN, WILLIAMS AND NORGATE, 14, HENRIETTA SYREET, COVENT GARDEN, LONDON, W.C. 1913. Price Sixpence. ( a JUL 7 19s Roval Dublin Soctety. a FOUNDED, A.D. 17381. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready tor transmission of the [ditor. Frercanrr—The Melting-Points of some of the Rarer Minerals. 459 as obtained by this method, placed side by side upon the meldometer ribbon and heated together, is evident. These wide differences are limited to certain specific cases of minerals, and melting-point standards obtained in a similar manner have agreed in producing an even slope in the foregoing curve of extension, fig. 3, p. 446. It is possible that the cause may be sought for in crystallographic changes (rather than in differences in purity) occurring only under certain conditions of observation, which might lead to varying results by methods so diverse as those used by different observers. I beg to record my thanks to Professor Joly for permitting me to continue his work on the meldometer. TygacH GronocicaL Laporatory, Trinity Cottecr, Dusuin. November 26th, 1912. SOIFNT. PROG. R.D.S., VOL. XIII., NO. XXXI 3 Zz L 40 J XXXII. A REFINED METHOD OF OBTAINING SUBLIMATES. By ARNOLD L. FLETCHER, M.A., B.E., Research Assistant to the Professor of Geology and Mineralogy in the University of Dublin. [Read Novemner 26, 1912. Published Fepruary 17, 1913. ] Tue facilities presented by the meldometer in the investigation of minerals by means of their sublimates and in general pyro-chemistry were pointed out by Professor Joly in 1891,1 and more recently reference has been made to the volatile deposits yielded by certain minerals at high temperatures.” The present communication, which is of a preliminary nature, shows that a modification of this mode of examination is likely to prove a valuable addition to the processes generally employed in qualitative chemical analysis. Apparatus and Procedure. As it is not generally necessary in this work to determine temperatures, the following simple and cheap apparatus may be employed.® COVER PLATE SUBLIMATION CHAMBER ~ The sublimation chamber‘ is a cylindrical, wooden or porcelain box 5-6 ems. in diameter, and 3 cms. in height, with walls about 1 cm. in thickness. The forceps FF", connected through the walls with the screws SS’, are hinged at about 1 cm. from the internal face, and are of sufficient length to 1 Joly, Proc. Roy. Irish Acad., 3rd Ser., vol. ii, 1891, pp. 44-48. 2 Fletcher, Scient. Proc. Roy. Dub. Soc., vol. xiii, No. xxxi, February, 1913, p. 443. 3 An instrument, which it is hoped to test shortly, somewhat on the lines of the one deseribed above, has been devised for obtaining the boiling-points in vacuo of the refractory elements up to the temperature of the carbon arc. 4 An annular chamber for obtaining sublimates on the meldometer ribbon in absence of free oxygen was described by Joly, idid., pp. 41 and 47. Frietcurr—A Refined Method of obtaining Sublimates. 461 reach nearly to the top of the box when bent at right angles at the hinge. The forceps are provided with milled-head screws MM’. ‘The hinges permit of the use of varying lengths of carbon rod, placed at any distance from either cover-plate, and, in the case of carbon, allow for expansion. ‘They are easily manipulated, and simplify frequent changes of the carbon rod. The sublimation chamber, which is closed above and below by cover-plates of convenient size, is fitted with inlet and outlet tubes, so that the heating process may be carried out in any desired atmosphere. The cover- plates may consist of glass, clear or opaque silica, biscuit ware, plaster of Paris, or even white paper, and may be raised if necessary by circular washers. A glass cover-plate is conveniently cooled by a drop of water on its upper surface. This apparatus, which, with the possible exception of the forceps, can be readily constructed in the workshop, is sufficiently inexpensive to warrant its general use by students. In general practice in this work a carbon rod was long since substituted for the platinum ribbon of the meldometer, as platinum was found very unsatis- factory, both on account of the ease with which it is attacked at high temperatures, and owing to the limited temperature range consequent upon its use. The powerful reducing action of the carbon at high temperatures is also a sufficient advantage to recommend it as the most suitable substance both in mineral work and in general chemical analysis. Small are carbons - of the requisite diameter can easily be obtained, or a small cored carbon are rod having a diameter of 6 or 7 mm., with a soit core of 2 mm. diameter, may be filed or sand-papered down on each side until after the core has appeared.t The flat rod thus produced is easily broken along its axis to form two flat carbon strips, having a cross-section about 2 mm. square, which, having been freed from all traces of the core material, are broken into convenient 3-cm. lengths. As it is desirable to localize the heat, a length of about half a cm. of the strip is reduced by a file to a very small cross-section, in which a small hole is bored to hold the powder, and when this part burns through, a fresh rod is substituted. ‘This procedure is economical, and prevents undue generation of heat within the sublimation chamber. It is possible to raise the reduced portion of one of these strips, which has a resistance at red heat of about half an ohm per cm., to nearly the temperature of the carbon are—about 3,600° C.—with a current of less than 20 amperes. At very high temperatures the strip slowly burns through. For lower temperatures one may use the stamped graphite core of a lead- pencil. ‘This at high temperatures buckles and yields a white sublimate. 1 The special carbons used in these experiments, haying a cross-section 2 mm. square, can be obtained from the ‘* Le Carbone Company,’’ London, E.C. 3822 462 Scientifie Proceedings, Royal Dublin Society. It has a resistance of under an ohm per cm., and is fused by ‘a current of about 11 amperes. It is occasionally more convenient to use platinum.’ A spool of ribbon 2 metres in length and 2 millimetres in breadth (No. 0440, Johnson and Matthey) can be obtained for 35s., and the short length of such ribbon required in a sublimation chamber of the foregoing dimensions is in- expensive, and, in the absence of substances corroding platinum, may be used repeatedly. If a ribbon be used, it must be twisted into a horizontal position after clamping between the forceps. A convenient resistance is necessary to ensure suitable temperature control of the strip. If desired, an approximation to the temperature of the strip could be obtained by observation of the heated carbon through different thicknesses of neutral tinted glass. When an opaque cover plate is used, the deposition of the sublimate may be watched in a mirror placed underneath the rod. Many of the effects obtained by this procedure are also produced in ordinary blowpipe practice, but it is possible by this method to obtain many effects which are not possible with the blowpipe, and, owing to the ease and rapidity with which these tests may be executed, the electrical method is more trustworthy, and at the same time more comprehensive than the older blowpipe process. A small heap of the powdered substance is placed upon the flattened surface of the carbon support, with the upper cover-plate in position. A slow stream of dry gas from an automatic generator is admitted if it is desired to examine the substance in an atmosphere other than air. Although not always necessary, a continuous current of gas through the sublimation chamber is sometimes advantageous for the purpose of transporting heavy sublimates, and for preventing the formation by diffusion of explosive mixtures. An explosion, however, in a sublimation chamber of the above dimensions is not serious unless the upper cover-plate is fastened down. The temperature of the strip is now raised at any desired rate, the substance being observed meanwhile through tinted glass. If a mixture or alloy is being examined, it may be necessary to raise the temperature slowly, and to stop at any certain point to effect a partial separation of the constituents, leaving a certain residue for further examination in a second experiment. The deposit on the cover-plate may be subjected to further wet or dry tests. With high temperatures, and when it is desired to subsequently heat the plate, transparent or opaque silica is the best substance; and where colours in transmitted light are to be examined, glass is preferrable. For showing mere traces of colour, white biscuit ware (which confers great richness upon the coloured deposits) should be used. 1 Joly, Proc. Roy. Irish Acad., 8rd ser., vol. ii, 1891. FLercHEr 463 The following table represents the sublimates which have so far been obtained in air. The first column shows the colours which prevail when the cover-plate is held close to the carbon; the second, when it is held at a short distance away. ‘The first are produced close to, the second farther from, the substance; and hence at intermediate distances “eyes” are produced showing rings of colours with different stages of oxidation from the centre outward. Similar eyes are produced by mixtures, the least refractory constituents tending to spread. Swirling currents tend to mix the colours. The tints described below are those which are observed upon glass or transparent silica by reflected light. Different tints are produced upon both glazed and unglazed porcelain, and in transmitted light. TABLE. Showing sublimates obtained in air upon glass or transparent silica. Natural Wlenent The coyer-plate is held The cover-plate is held at some Families. : close to the substance. distance from the substance. Copper, . Dark green or red, Yellow to red-yellow. I. Silver, Grey- white, Dull grey, black, some pink. Gold, Violet to purple, Violet to purple. ( Glucinum Corkum); Dark, White. Magnesiurn, Dark, White. Inte Zine, Dark, White. | Cadmium, Dark, Red-brown. (Mercury, Grey-w hite, Grey -white. Aluminium, Dark, White. III. Indium, . Dark, Cream-white, some pale yellow. Thallium, Dark, Red and white. { Titanium, White, White. | Zirconium, Dark, 2 Cream-white. IV { Cerium, . Dark brown, White. : Silicon, . Red-brown to orange, Yellow-white to white. | Tin, Brown, White. (Lead, Dark, Yellow to light yellow. ( Vanadium, Brown-black, Yellow-green. | Columbium (Niobium), Dark, White. Vv { Tantalum, Dark, White. : Arsenic, . Dark, White. | Antimony, Dark, White. ( Bismuth, Dark, Yellow. Chromium, Dark, Dull green. [stotyhaeni, : Dark, Yellow-white. VI d Tungsten, Dark, White. : Uranium Dark, Dark. | Selenium, Dark red, Red. | Tellurium, Dark, White and brown-white. \l. Manganese, Dark, Light Brown. (Iron, Dark, Dark brown-black. Cobalt, Dark, Dark. VIII. Nickel, Dark, Dark. Ruthenium, Dark, Dull grey. Platinum, Dark, Dark. 464 Scientific Proceedings, Royal Dublin Society. Lodine Test. The series of tests to be described, which are essentially those obtained by Dr. Haanel! using hydriodic acid, are carried out with iodine alone in the following manner :— Iodine is sublimed upon the cover-plate. This is inverted over the substance, which is caused to sublime directly upon the existing deposit of iodine. The contact of the hot vapour with the iodine in a condition of sublimation is sufficient in many cases to produce the iodide which appears when the ascending column of vapour meets the iodine, and is accompanied by a rapid colour-transformation. The following table shows the colours of deposits which have so far been obtained by sublimation in an atmosphere of sulphuretted hydrogen, and on the iodine-plate described. ‘ Substance. In sulphuretted hydrogen ” On the iodine plate.® Copper, Dark greenish-black, White. Silver, Black, Pale yellow. Gold, — Yellow-brown. Zine, . White, . ; White. Cadmium, Fine yellow, . White. Mercury, Black, Fe Scarlet and bright yellow, showing green on standing. Indium, Red-brown, . Yellow. Thallium, Black to ash- brown, Deep orange-brown. Tin, Black and yellow, Orange-brown. Lead, Blue-black, Deep yellow. Arsenic, . Deep red and yellow ; Deep yellow. Antimony, . Deep brick red, Deep orange-red. Bismuth, Brown and black, Chocolate-brown. Selenium, Red, B Black. Tellurium, Black, Chocolate-brown. It is found that the colours of deposits produced by these methods are of a greater richness and delicacy than those obtained in the wet way, and slight differences in tint are more surely observed. To obtain these deposits in sufficient quantities for examination, a few milligrams of the substance are usually sufficient. LHxperiments have been made which show that the place of the iodine may be assumed by other substances, and further tests introduced. 1 Dr. Haanel, Trans. Roy. Soc., Canada, vol. 1, 1883, Sec. 3, p. 65. * Sometimes produced by sublimation on to a deposit of sulphur. * Many of these are more easily obtained in absence of free oxygen. This reaction also is sometimes effected by subliming the iodine on to the existing sublimate of the substance under examination. FietcHer—A Refined Method of obtaining Sublimates. 465 Comparative Standards. It is possible in this method to keep more or less permanent records of the tests which may serve as comparative standards. The initial brightness of most of the deposits is transitory, the colour fading more rapidly in moist atmospheres. Sublimates, however, may be hermetically sealed by surrounding with a ridge of seccotine, upon which a plate of glass is pressed in presence of nitrogen or carbon dioxide. Limits of Sensibility. The delicacy of this method in detecting the presence of very minute quantities of volatile impurities in solution, and the limits to which the detection could be thus carried under the most favourable circumstances, are evident in the following experiments. ‘he results show the limiting amounts of known substances in solution which can be detected. It is possible that, with substances yielding the more intense colours with the iodine-plate, it will be possible to identify very small quantities of substances in solution. A small quantity of solution of the substance is transferred to the platinum ribbon support from a capillary pipette. The ribbon is heated gently to evaporate the water, when the substance can often be seen asa dull stain on the bright surface of the platinum. A glass cover-plate is polished and placed over and very close to the ribbon, which is rapidly heated to whiteness, and allowed to cool. When the sublimate is very thin indeed, it is at this stage nearly invisible, and may be demonstrated either by moistening with the breath or polishing with asoft cloth, when the deposit which is invisible by transmitted light will become visible by reflected light against a dark background. By this method it is possible to detect the presence in a drop of solution of 4:5 x 107 gram of lead nitrate, or therefore of 2°8 x 10 gram of metallic lead, and assuming all the lead to have been deposited as white oxide, the sublimate would contain about 3 x 107 gram of lead oxide. ‘The deposit was not uniform in thickness, but thinned off indefinitely at the edges, occupying an area of about 7 sq. mm., and the average thickness therefore could not have exceeded 46 x 10-7 cm.—a thickness of less than one-tenth that of the thinnest gold-leaf. In a similar manner it is possible to distinguish easily the sublimate obtained from a small drop (00009 c.c.) of a solution of arsenic in dilute 466 Scientific Proceedings, Royal Dublin Society. nitric acid. This quantity of solution contained about 2°4 x 107 gram of arsenic. If it be assumed that this was all sublimed as arsenious oxide, the sublimate must have consisted of about 3 x 107% gram of matter, and was deposited to an average thickness of about 2 x 10®cm. While it would be impossible to identify deposits in such vanishingly small amounts, yet in a sublimate from about 10° gram of arsenic in ‘solution, the “ pupil” of un- oxidized arsenic in the centre was just visible. The foregoing process would be an excellent method of obtaining a thin film of matter in a high state of purity. Summary. 1. The method of analysis described above possesses a range of action enormously superior to that attained by the blowpipe, and limited only by the volatility of the carbon, and hence is capable of revealing effects impossible to obtain in blowpipe work. 2. It is possible to examine the effect of heat upon substances in different atmospheres, sublimates being formed with the same facility in these atmospheres as they are in air. ‘These processes would be by ordinary laboratory methods very laborious, if not impossible. A mineral powder may in the course of a few minutes be strongly heated in hydrogen, oxygen, sulphuretted hydrogen, hydrogen chloride, nitrogen, or other atmosphere, with the deposition of various distinctive sublimates. 3. Mixtures or alloys, such as brass, or even steel, may be dealt with to a certain extent by means of fractional volatilization, the deposits produced being removed on separate cover-glasses. Even when no attempt is made at fractionation, sublimates tend to become automatically separated; those of greatest volatility sublime first, being seen through a glass cover-plate, whilst the more refractory substances sublime last, and are seen under the plate. Very small quantities of impurities in metals have been thus detected, the cadmium present in commercial zine being easily distinguishable. 4. Experiments being made under conditions of cleanliness and with small chance of loss, tests may be carried out on smaller quantities of material than would be otherwise possible. Iveacu GronocioaL Laporatory, Triity Cottece, Dusiin, 26th November, 1912. ilo Lo 10. 11. 12. 18. 14. 15. SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Ivish Pteridosperm, Crossotheca Héninghausi, [Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, D.sc., F.L.S. (Plates I-III.) (March, 1911.) 1s. . 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(Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Joanson, p.sc.,F.u.s. (Plates VII., VIII.) (June 28, 1911.) 1s. Award of the Boyle Medal to Prorsssor Joan Joty, M.a., sc.D., F.R.s. (July, 1911.) 6d. On the Amount of Radium Hmanation in the Soil and its Escape into the Atmosphere. By Joun Jony, sc.p., F.x.s., and.Lovurs B. Suyrx, s.a. (Plate IX.) (August, 1911.) Is. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks.. By }E. A. Newent ARseR, M.A, F.LS. F.G.s. (January 1912.) 1s. Forbesia cancellata, gen. eb sp. nov. (Sphenopteris, sp., Baily.) By T. Jonnson, D.sc., F.u.s. (Plates XITJ. and XIV.) (January, 1912. 1s. The Inheritance of the Dun Coat-Colour in Horses. By James Winson, M.a., B.SC. (January, 1912.) 1s. On the Vacuum Tube: Spectra of the Vapours of some Metals and Metallic Chlorides. Part I—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Pontos, p.sc. (Plates XV. and XVI.) (February 21,1912.) 1s. 16. We 18. 19: 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32, SCIENTIFIC PROCEEDINGS—continued. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris., By Henry H. Dixon, sc.p., r.r.s., and W.R. G. Arnins, m.a. (February 21,1912.) 6d. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, rr.s. (Plates XVIL—-XIX.) (March 26, 1912.) 1s, Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Drxon, sc.p., ¥.r.s., and W. R. G. Atkins, m.a., a.t.c. (April 9, 1912.) 6d. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Drxov, sc.p., F.n.s., and W. R. G. Arxins, m.a., atc. (April 9, 1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jounson, p.sc., F.u.s. (Plates XX. and XXI.) (April 12, 1912.) Is. On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part IJ.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By James H. Porto, D.Sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s, The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Copper. and Lithium. By Gunyrvizve VY. Morrow, A.R.C.Sc.1. (Plate XXIV.) (May 11,1912.) 1s. Award of the Boyle Medal to Sir Howarp Gruss, F.p.s., April 16, 1912. (May 18, 1912.) 6d. Notes on Dischidia rafflesiana, Wauu., anv Dischidia nummularia, Br. By A. F. G. Kerr, m.p. (Plates XXV.-XXXI.) (September 30, 1912.) 2s, Recherches Expérimentales sur la Densité des Liquides en dessous de 0°. Par Jean Tummermans, (October 18, 1912.) 3s. Steady and Turbulent Motion in Gases. By Joun J, Dowzine, ua. (Plates XXXII. and XXXIIL.) (November 16,1912.) 1s. 6d. Unsound Mendelian Developments, especially as regards the Presence and Absence Theory. By Jamus Witson, u.a., B.sc. (December 18, 1912.) 1s. 6d. Osmotic Pressures in Plants. I.—Methods of Extracting Sap from Plant Organs. By Henry H. Dixon, sc.p., F.r.s., and W. R. G, ATKINS, M,A., 4.1.0, (February 8, 1913.) 1s. Osmotic Pressures in Plants. II.—Cryoscopic and Conductivity Measurements on some Vegetable Saps. By Henry H. Drxon, sc.p., ¥.x.s., and W, R. G. ATKINS, M.A., A.I.c. (February 8, 1913.) 6d. A Method of Microscopic Measurement. By J. Jouy, sc.p., F.R.s. (February 7, 19138.) 6d. The Melting-Points of some of the Rarer Minerals. By Arnotp , Fiurrcuer, M.A, B.E. (February 15,1913.) 1s. A Refined Method of obtaining Sublimates. By Arnoxp L. FLercuer, u.a., BE. (February 17,1913.) 6d. DUBLIN: PRINTED AT THE UNIVERSUtY PRESS BY PONSONBY AND GIKBS, THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 33. FEBRUARY, 1918. ON THE GERMINATION OF THE SEEDS OF SOME DICOTYLEDONS. BY J. ADAMS, M.A. (CanrTas.). (PLATE XXXIV.) | Authors alone are responsible for all opinions expressed in their Communications. | DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price One Shilling and Sixpence. Koval Wublin Society. FOUNDED, A.D. 1781. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be get down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the [ditor. foes] XXXII. ON THE GERMINATION OF THE SEEDS OF SOME DICOTYLEDONS. By J. ADAMS, M.A. (Cantab.). (PLrare XXXIV.) [Read December 17, 1912; Published Fesrvary 21, 1913.] Wuew seeds ripen they are usually carried some distance from the parent plant by the agency of water, wind, or animals. If they fall in a suitable habitat, some of them will, after a longer or shorter interval, germinate. One of the objects of the present investigation was to discover how long the seeds of a particular species lie dormant in the ground before germination. The ideal method of procedure would be to collect the seeds when ripe and to bury them at once in the soil, selecting a habitat as similar as possible to that in which the parent plant was growing. Needless to say, this ideal was not in many cases realized. While most ‘“ Floras” of the British Isles give full particulars of the time of flowering of the different species, I am not acquainted with any that give the dates of ripening of the seed. In the case of common plants little inconvenience need result from this dearth of knowledge. ‘he particular species of plant can be easily examined from time to time and observations made on the rate of the ripening of the seeds. But in the case of a rare species much time may be spent in collecting ripe seeds for purposes of experiment. For example, three different journeys had to be made to a point eight miles from Dublin, in order to obtain seeds of Rubia peregrina. Another difficulty is, that some species very rarely produce seeds. In 1910 I succeeded for the first time in getting a few seeds of the Common Bindweed (Convolvulus sepium). In 1911 I secured an abundance of seeds of this species; but whether this abundance was the result of the unusually warm summer, Iam unable tosay. Knuth, in his “ Handbook of Flower Pollination,” 1906-9, states that the large Bindweed seldom fruits in localities where the Hawk Moth (Sphinw Convolvuli, Linn.) is absent. Only once have I succeeded in getting what looked like sound seeds of such a common plant as Meadow Sweet (Spirea ulmaria, Linn.), but these were not tested in order to discover whether they were really viable. I have not so far been able to SCIENT, PROC, R.D.S., VOL. XIII., NO. XXXIII. 4a 468 Scientifie Proceedings, Royal Dublin Society. obtain seeds of the Rose Bay (Epilobium angustifolium, Linn.), although it is so commonly grown in gardens. It will therefore be seen that it was not always possible to obtain seeds for experiment that were ripened in the preceding season. In every case I have given (in brackets), as far as known, the year in which the seeds were ripened. In a few cases the age was uncertain, as the packets were not dated at the time of collection, these having been collected as specimens of the seed and not with a view to germination. In very few instances, however, were the seeds more than five years old. The number of seeds of each species experimented on varied greatly, depending on the number of seeds in my possession and the difficulty of obtaining them. Where the seeds were counted the number sown usually varied between five and fifty. In one case as few as two were sown and in another as many as 250. In many cases, however, where the seeds were small or abundant the number was not counted. It may safely be assumed in such cases that the number of seeds sown at least exceeded ten. The date of sowing the seed and the date of germination (where this occurred) are given in each case. By germination is meant that the young plant had actually appeared above ground or that the cotyledons were fully expanded. The time required for germination depended largely on the time of year at which the seeds were sown and on the species under consideration, varying from one or two weeks to a year and a half. In some cases seedlings of various species were found growing wild in their natural surroundings. ‘The date of germination of such self-sown plants is given. In the absence, however, of definite information relative to the time of ripening of the seeds we can only measure within rough limits the actual time during which they have been lying in the soil. Indeed in some cases it is safe to assume that not one but two seasons intervened between the time of their ripening and germination. In the majority of cases, the seeds were sown in flower-pots in the open air. During the summer months, in order to lessen the work of watering them, they were sunk in the soil almost up to the rim of the pot.. In a considerable number of instances, however, the seeds were sown in the open ground. A better supply of moisture is maintained in the latter case, but it is difficult to be certain of the actual limits within which the seeds were sown and, if the label happen to become displaced, impossible. : In a very considerable number of cases the seeds failed to germinate within the period of observation. Doubtless, if some of them had been given longer time, they would probably have germinated. But in other cases, such as that of oak, the seeds were dug up at the end of the time of observation Apams—On the Germination of the Seeds of some Dicotyledons. 469 and were found to have become rotten. As the seeds were those of the previous season, it is difficult to understand their failure to germinate. Possibly the fact that they were not sown till January may have something to do with it. Another object of the investigation was to obtain specimens of the seedlings. he chief source of information on this subject is Lubbock’s large work ‘“‘ A Contribution to our Knowledge of Seedlings,” two vols., 1892. More recently, H. Coupin, in ‘“‘ Les Graines Expliquées,” 1909, gives descrip- tions of the germination of a number of economic plants. In the case, however, of a large number of our native species nothing is known of their germiaation. The present paper contains descriptions of 158 species that are not enumerated in Lubbock’s treatise. Altogether observations were made on 278 species belonging to 190 genera, and 58 families of Dicotyledons- With a few exceptions, all the species enumerated are natives of the British Isles. The exotic species are:—Plum, Peach, Almond, Virginian Prune, Pear, Grape-Vine, Orange, Lemon, and Fig. The foliowing species may germinate in the same year in which the seeds are ripened, and therefore normally pass the winter in the seedling stage :— Arenaria verna, Lychnis dioica, L. Githago, Bellis perennis, Leontodon nudicaulis, Taraxacum officinale, Tussilago Farfara, Salvia Verbenaca, Lotus corniculatus Vicia Oracca, Reseda Luteola, Caucalis nodosa. There seems to be little doubt that this list could be greatly extended by future observation. Subterranean cotyledons occur in the following:—Lathyrus, Vicia, Rhamnus Frangula, Almond, Peach, Virginian Prune, Rubia peregrina, and Lemon. It is noteworthy that, in some species of the genera Prunus and Rhamuus, the cotyledons remain below, while in other, species they come above ground. Seedlings of Yellow Rattle were allowed to grow in order to determine whether they could develop without obtaining nourishment from the roots of other plants. In all cases, however, they failed to grow to maturity. Previous attempts to germinate the seeds of this species resulted in failure. It is essential for their germination that the seeds be buried in soil as soon as they are scattered from the parent plant. It is well known that Leguminous plants produce a certain number of “ hard” seeds, that is, seeds which remain impermeable to water for a long time, and while in this condition they do not germinate. ‘he largest percentage of these “hard” seeds that [ have observed in any one species was in the case of Vicia sepium. Out of one lot of twenty seeds planted in October none had germinated after nine months. Another lot of seeds was sown in July; after six months one had germinated, and five months later 4a2 470 Scientific Proceedings, Royal Dublin Society. another had germinated. On examining the soil the seeds were found to be as hard as when they were planted. A. thin slice was cut off the seed- coat, and the seeds were replaced in the soil. After a month seven had germinated, and three weeks later eight more had germinated. Water could not pass through the seed-coat until part of the impermeable layer had been removed. The seeds of stone-fruits do not usually germinate until the hard protective covering has decayed in the soil. Ii it germinated sooner, the radicle would be unable to force its way through the enclosing envelope. In order to determine whether the delayed germination is inherent, the hard stone was removed in the case of some seeds of Hawthorn and Sloe, and the seed only planted. It was found, however, that removal of the hard enclosure imprisoning the seed did not in any way facilitate the process of germination. Considerable differences were exhibited in the size of the cotyledons of the same species, doubtless depending largely on the particular spot where the seed fell or was planted. In a dry situation the parts of the plant would be more stunted than would be the case if the seed germinated in a moister soil or in the shade of other plants. The measurement of cotyledons was as far as possible made after the first ordinary leaf had expanded. Some species showed irregularities in the number of cotyledons. Three were found in Anthriscus sylvestris, Capsella Bursa Pastoris, Carlina vulgaris, Euphorbia exigua, Prunus Persica, Rhamnus catharticus, Sambucus nigra. A specimen of Mercurialis annua had the cotyledons united nearly to the tip, while a seedling of Sycamore had one of the two cotyledons cleft almost to the base. In the subjoined list the classification adopted is that of Engler, and the families are grouped for convenience of reference in alphabetical order. ‘The genera of each family and the species belonging to each genus are also arranged alphabetically. AQUIFOLIACER. Ilex Aquifolium Linn.—Seeds (1910) planted on 14th July, 1911. None had germinated on 25th July, 1912; on 10th October, 1912, none had germinated. Seedlings were found at Lucan on 12th June, 1911. BETULACER. Alnus rotundifolia Miller.—Seeds (1910) planted on 18th April, 1911. None had germinated on 8th June, 1912. Betula alba Linn.—Seedlings found in peat bog at Edenderry, King’s County, on 19th July, 1906. Apams—On the Germination of the Seeds of some Dicotyledons. 471 Corylus Avellana Linn.—Fourteen seeds (presumably 1910) were planted on 15th March, 1911, the shell having been previously removed. On 19th July, 1911, one had germinated and was about 14 inches above ground. On 28th October, 1911, no more had germinated. Seven seeds (presumably 1910) were freed from the shell and planted on Ist July, 1911. On 28th October, 1911, none had germinated. BoraGINacez. Cynoglossum officinale Linn.—Cotyledons petiolate, spatulate, glabrous, rather fleshy, with entire margin. Length, including petiole, 832 mm., breadth 14 mm. Lycopsis arvensis Linn.—Seedlings obtained in Co. Dublin on 13th May, 1911. Cotyledons broadly lanceolate to spatulate, tapering at the base, entire, obtuse, hispid, somewhat fleshy, 214mm. by 83mm. First leaf crisped, hispid. CaLLITRICHACEE Callitriche verna Linn.—Seeds (1910) planted on 19th April, 1911. None had germinated on 28th October, 1911. CAMPANULACES. Campanula Trachelium Linn.—Seeds (1910) planted on 19th April, 1911. On 24th June, 1911, two had germinated, and on 14th July, 1911, another had germinated. On 14th October, 1911, no more had germinated. Cotyledons shortly petiolate, broadly ovate or oblong, obtuse, entire, glabrous, 3-34 mm. by 14mm. First leaf subrotund, serrate or crenate, hispid. Lobelia Dortmanna Linn.—Seeds (1909) planted on 6th May, 1911. On14th October, 1911, none had germinated. CAPRIFOLIACER. Lonicera Periclymenum Linn.—Seeds (1910) planted on 29th September, 1910. On 1st April. 1911, eighteen had germinated. Cotyledons almost sessile, broadly elliptical, with prominent veins, glabrous, entire, with a very shallow notch at the tip, 53 mm. by 33-4 mm. Sambucus nigra Linn.—Seeds (1910) planted on 29th es 1910. On 29th April, 1911, several had germinated. Viburnum Opulus Linn.—Six seeds (1910) were planted on 29th September, 1910, and nineteen more on 3rd October, 1910. On 8th June, 1912, none had germinated. 472 Scientific Proceedings, Royal Dublin Society. CanrYOPHYLLACE&®. Arenaria serpyliifolia Linn.—Seeds (1910) planted on 14th July, 1911. On 28th July, 1911, several had germinated. Cotyledons petiolate, blade ovate—oblong, entire, obtuse or pointed, glabrous. Petiole 13-24 mm. long, blade 21-3 mm. by 1-11 mm. A. trinervia Linn.—Seeds (1909 probably) planted on 6th May, 1911. On 24th June, 1911, three had germinated, and on 14th July, 1911, two more had germinated. Cotyledons petiolate, blade lanceolate, entire, pointed, glabrous. Petiole 4-6 mm. long, blade 6-7 mm. by 3-33 mm. A. verna Linn.—Seeds (1910) planted on 6th October, 1910. On 19th November, 1910, some seeds had germinated. On 19th November, 1911, another had germinated. Cotyledons sessile, linear, entire, obtuse, glabrous, 33 mm. by 3 mm. Cerastium arvense Linn.—Seeds (1910) planted on 6th May, 1911. On 38rd June, 1911, five had germinated, and on 19th June, 1911, another had germinated. C. vulgatum Linn.—Seedlings found in Co, Dublin on 28rd October, 1910. Cotyledons broadly lanceolate, tapering to the base, entire, pointed, glabrous, 3 mm. by 2-1 mm. Lychnis dioica Linn.—Seeds (1910) planted on 6th October, 1910. On 19th November, 1910, some seeds had germinated. On 4th March, 1911, many seeds had germinated. Cotyledons ovate-elliptical, tapering at the base, entire, obtuse, glabrous, 8-9 mm. by 23-3mm. First leaves hairy. L. Githago Scop.—Ten seeds (1910) planted on 6th October, 1910. On 7th December, 1910, these had germinated and had formed several leaves. Silene acaulis Linn.—Seeds (1910) planted on 6th May, 1911. On 19th June, 1911, several had germinated. Cotyledons oblanceolate, tapering to the base, rather fleshy, 8 mm. by 13 mm. S. amoena Huds.—Seeds (1910) planted on 22nd June, 1911. On 14th July, 1911, several had germinated. Seedlings were found at Dalkey on 6th May, 1910. Cotyledons lanceolate-elliptical, tapering at the base, somewhat fleshy, entire, obtuse, glabrous, 8-ll mm. by 2-3mm. First leaves hispid on the margin. S. latifolia Rendle and Britten.—Seeds (1910) planted on 12th July, 1911. On 16th September, 1911, one had germinated, and on 28th October, 1911, another had germinated. ApamMs— On the Germination of the Seeds of some Dicotyledons. 473 Spergularia rubra (Linn.).—Cotyledons sessile, fleshy, oblong, entire, obtuse, glabrous, 73 mm. by 2 mm, Stellaria media Villars.—Seedlings found in Co. Dublin on 21st July, 1911. Cotyledons petiolate witha few bristles at the base, bladelanceolate, entire, acute, glabrous. Petiole 33-9 mm., blade 43-9 mm. by 24-4 mm. S. palustris Retzius. Seeds (1909 probably) planted on 6th May, 1911. On 28th October, 1911, none had germinated. CELASTRACER. Euonymus europeus Linn.—Seeds (1909) planted on 19th April, 1910. On 13th May, 1911, some had germinated. CHENOPODIACES. Atriplex laciniata Linn.—Seedlings found in Co. Dublin on 26th May, 1911. Cotyledons somewhat fleshy, sessile, oblong, entire, obtuse, glabrous, with prominent midrib, 22 mm. by 5 mm. Hypocotyl red. First leaves opposite, petiolate, with subrotund blade which is almost entire and frosted on the surface. A. littoralis Linn.—Seeds (1910) planted on 20th April, 1911. On 28th October, 1911, none had germinated. A. patula Linn.—Seeds (1910) planted on 18th April, 1911. On 28rd September, 1911, none had germinated. A different lot of seeds (1910) was planted on 12th July, 1911. On 28th October, 1911, none had germinated. Beta maritima Linn.—Seedlings found at Dalkey on 6th May, 1910. Cotyle- dons shortly petiolate, blade lanceolate, entire, obtuse, glabrous. Petiole 4mm. long, blade 10-13 mm. by 2-33 mm. Chenopodium rubrum Linn.—Seeds (1910) planted on 20th April, 1911. On 23rd September, 1911, none had germinated. Salicornia ewropea Linn.—Seedlings obtained in Co. Dublin on 24th May, 1912. Cotyledons sessile, united at the base, clasping the stem, deltoid, very fleshy, obtuse, glabrous, 23-34 mm. by 23-33 mm. Salsola Kali Linn.—Seeds (1910) planted on 18th April, 1911. On 18th July, 1911, only one had germinated, and some more seeds were sown. On 28rd September, 1911, no more had germinated. Cotyledons fleshy, slightly connate at the base, linear, entire, some- what obtuse, glabrous, 12 mm. by 14 mm. Sueda maritima Dumort.Seeds (1910) planted on 6th October, 1910. On 183th May, 1911, several had germinated. Cotyledons fleshy, oblong— linear, scarcely tapering at the base, entire, pointed, glabrous, 8 mm. by 143mm. First leaf linear, with minute hairs. 474 Scientific Proceedings, Royal Dublin Society. CompPosira. Arctium Lappa Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Seedlings found in Co. Dublin on 8th April, 1910, and 6th May, 1910. Cotyledons spatulate, tapering at the base, united below, entire, glabrous, 19-35 mm. by 6-12 mm. Artemisia Absinthiwm Linn.—Seeds (1910) planted on 19th April, 1911. On 28th October, 1911, none had germinated. A. vulgaris Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Cotyledons sessile, broadly elliptical, entire, obtuse, glabrous, 25-4mm. by 13-2 mm. First leaf hairy. Aster Tripolium Linn.—Seedlings found in Co. Dublin on 8th April, 1910. Cotyledons fleshy, almost sessile, broadly lanceolate, tapering at the base, entire, obtuse, glabrous, 9-10 mm. by 4 mm. Bellis perennis Linn.—Seeds (1911) planted on 14th July, 1911. On 16th September, 1911, many had germinated. Cardwus crispus Linn.—Seeds (1910) planted on 20th April, 1911. On 24th June, 1911, several had germinated. Cotyledons spatulate, entire, glabrous, 104-123 mm, by 6-7 mm. First leaf hairy. C. pyenocephalus Linn.—Seeds (1910) planted on 12th July, 1911. On 26th July, 1911, twelve had germinated, the first ordinary leaf being visible. Cotyledons shortly petiolate, blade subrotund—oblong, entire, slightly notched at the tip, glabrous, 13mm. by8 mm. First leaf hairy, with spiny margin. Carlina vulgaris Linn.—Twenty-five seeds (1910) planted on 5th October, 1910. On 1st April, 1911, several had germinated. Cotyledons almost sessile, elliptical, entire, obtuse, giabrous, 4-43 mm. by 2-3mm. First leaf cottony. Centaurea nigra Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Cotyledons obovate—subrotund, tapering to the base, entire, obtuse, glabrous, 9mm. by 33-4 mm. C. Scabiosa Linn.—'wenty-five seeds (1909 probably) planted on 18th October, 1910. On 29th April, 1911, several had germinated. Cotyledons spatulate, gradually tapering to the base, entire, glabrous, with evident midrib, 20-23mm. by 5-54mm. First leaf lanceolate, hairy. Chrysanthemum Leucanthemum Linn.—Cotyledons spatulate, entire, 4mm. oy 2mm. Apvams—On the Germination of the Seeds of some Dicotyledons. 475 C. segetum Linn.—Seeds (1910) planted on 18th April, 1911. On 28rd September, 1911, none had germinated. Cnicus arvensis Hoffm.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Cotyledons spatulate, entire, 12mm. by 5 mm. C. lanceolatus Hofitm.—Seedlings obtained at Murrough of Wicklow on 18th May, 1910. Cotyledons obovate, tapering to the base, entire, obtuse, glabrous, 11-15mm. by 4-73mm. First leaf simple, obovate, hairy, with spiny margin. C. pratensis Willd.—Ten seeds (1910) planted on 5th October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 11th November, 1911, none had germinated. Crepis paludosa Moench.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Erigeron acre Linn.—Seeds (1910) planted on 3rd October, 1910. On 28rd September, 1911, none had germinated. Eupatorium cannabinum Linn.—Seeds (1910) planted on 12th July, 1911, On 28th October, 1911, none had germinated. Hieracium boreale Eries.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Hypochoeris glabra Linn.—Seeds (1910) planted on 19th April, 1911. On 13th May, 1911, several had germinated. Cotyledons narrowly spatulate, tapering to the base, entire, obtuse, glabrous, with evident midrib at the base, 11mm. by 23-3mm. First leaf simple, hairy. H. radicata Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Cotyledons oblong-obovate, tapering to the base, entire, obtuse, glabrous, 13 mm. by 3-4 mm. Inula crithmoides Linn.—Seeds (age uncertain) planted on 6th May, 1911. On 14th October, 1911, none had germinated. I. salicina Linn.—Seeds (1909 probably) planted on 6th May, 1911. On 14th October, 1911, none had germinated. Lactuca muralis Gaertner.—Twenty seeds (1909 probably) planted on 17th October, 1910. On 28rd September, 1911, none had germinated. Lupsana communis Linn.—Seeds (1910) planted on 12th July, 1911. On 16th September, 1911, several had germinated. Seedlings obtained in Co. Dublin on 24th May, 1911, and 11th July, 1911. Cotyledons petiolate, blade broadly elliptical to spatulate, entire, SCIENT. PROC. R.D.S., VOL. XIII., NO. XXXIII. 4 B 476 Scientific Proceedings, Royal Dublin Society. obtuse, glabrous. Petiole 4mm. long, blade 4-5mm, by 33-4 mm. First leaf simple, petiolate, hairy, with subrotund, distantly serrate blade. Leontodon autumnalis Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Cotyledons 12mm. by 1}mm., with a long petiole, and oblong, entire, obtuse, glabrous blade. L, nudicaulis Sol.—Seeds (1910) planted on 6th October, 1910. Several had germinated on 19th November, 1910. Cotyledons lanceolate, tapering to the base, obtuse, entire, glabrous, 9-llmm. by 2mm. First leaf hairy. Matricaria Chamomilla Linn.—Seeds (1910) planted on 19th April, 1911. On 28th October, 1911, none had germinated. M. inodora Linn.—Seedlings found at Dalkey on 6th May, 1910. Cotyledons somewhat fleshy, obovate, tapering towards the base, glabrous, 34-5 mm. by 2-23 mm. First leaf pinnately lobed. Senecio erucifolius Linn.—Seeds (1910) planted on 8th October, 1910. On 27th May, 1911, two had germinated. More seeds were sown on 13th July, 1911, and on 2nd October, 1911, five of these had germinated. S. sylvaticus Linn.—Seeds (1910) planted on 10th October, 1910. On 27th May, 1911, three had germinated. On 23rd September, 1911, no more had germinated. Cotyledons elliptical, tapering at the base, entire, rounded at the tip, glabrous, 73-10 mm. by 2-33mm. First leaf hairy, distantly serrate. Solidago Virgaurew Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Sonchus arvensis Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. S. oleraceus Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Seedlings found at Greystones on 4th June, 1906. Cotyledons, 43-63 mm. by 24-34 mm., shortly petiolate, blade ovate to orbicular, entire, obtuse, sianoae First leaf petiolate, blade orbicular, dentate, hairy. Taraxaeum officinate Weber.—Seeds (1910) planted on 18th April, 1911. On 23rd September, 1911, none had germinated. Cotyledons oblong, entire, glabrous, obtuse or slightly notched: tapering to the base, 8-11 mm. by 383 mm, Apams—On the Germination of the Seeds of some Dicotyledons. 477 Tragopogon pratensis Lainn.—Twenty seeds (1910) planted on 5th October, 1910. On 1st April, 1911, nineteen had germinated. Cotyledons linear, scarcely tapering at the base, pointed, entire glabrous, united at the base, with one prominent vein, 44-47 mm. by 13mm. First leaf slightly broader than the cotyledons, with three prominent veins. Lussilago Faurfara Linn.—Seeds (1911) planted on 10th June, 1911. On 26th July, 1911, four had germinated. CoNVOLVULACEA, Convolwulus sepium Linn.—'len seeds (1911) planted on 13th March, 1912. On 18th April, 1912, five had germinated, and on 8th May, 1912, two more had germinated. CorNACER. Cornus sanguinea Linn.—Five seeds (1910) planted on 19th April, 1911. On 8th June, 1912, one had germinated. Cotyledons shortly petiolate, blade broadly elliptical, obtuse, entire, glabrous. Petiole 1mm. long, blade 7mm. by 5mm. CRASSULACES. Ootyledon Umbilicus- Veneris Linn.—Seeds (age unknown) planted on 18th October, 1910. On 14th October, 1911, several had germinated. Cotyledons petiolate, blade somewhat peltate, fleshy, rotundate, entire, obtuse, glabrous. Petiole 1mm. long, blade 1}mm. by 14mm. First leaf peltate. Sedum roseum Scopoli.—Seeds (age uncertain) planted on 6th May, 1911. On 14th October, 1911, none had germinated. S. Velephium Linn.—Seeds (1919) planted on 20th April, 1911. On 28th October, 1911, none had germinated. CRUCIFERZ. Alliaria oficinalis Andrz.—Twenty-five seeds (1910) planted on 6th October, 1910. On 4th March, 1911, fourteen had germinated, and on Ist April, 1911, five more had germinated. Cotyledons with long petiole, blade oblong or linear, truncate, or slightly notched at the tip. Petiole 10mm. long, blade 9mm. by 33 mm. First leaf slightly hairy. 4 478 Scientific Proceedings, Royal Dublin Society. Arabis Thaliana Linn.-—Seeds (age uncertain) planted on 15th July, 1911. On 16th September, 1911, several had germinated, and had produced several leaves. Cotyledons petiolate, blade ovate-subrotund, entire, obtuse, glabrous. Petiole 1 mm. long, blade 2mm. by 13 mm. First leaf simple, entire, hairy. Barbarea vulgaris Br.—Seeds (1910) planted on 12th July, 1911. On 16th September, 1911, several had germinated. Cotyledons petiolate, blade subrotund, entire, glabrous, faintly notched. Petiole 24-5 mm., blade 3mm. by 14-23 mm. Brassica arvensis Ktze.—Seedlings found on 8th April, 1910, in County Dubhn. Cotyledous petiolate, blade obreniform, entire, glabrous. Petiole 6-9 mm. long, blade 6-8 mm. by 8-103 mm. First leaf simple, hairy. Capsella Bursa-pastoris Medic.—Seeds (1911) planted on 21st July, 1911. On 28th July, 1911, several had germinated. More seeds were sown on 16th September, 1911, and on 14th October, 1911, these had germinated. Cardamine hirsuta Linn.—Seeds (1910) planted on 18th April, 1911. On 24th June, 1911, four had germinated. Cochlearia officinalis Linn.—Seedlings found in Co. Dublin, on 8th April, 1910, and 24th October, 1911. Cotyledons petiolate, blade rather fleshy, rotund, entire, slightly notched at base and apex. Petiole 4-7 mm. long, blade 23-53 mm. by 3+53 mm. Lepidium heterophyllum Benth.—Seeds (1910) planted on 26th April, 1911. On 28th October, 1911, several had germinated. Some more seeds were planted on 12th July, 1911, and ‘on 28th July, 1911, several had germinated. Cotyledons petiolate, blade oblong-obovate, tapering into the petiole, entire, obtuse, glabrous. Petiole 2mm., blade 6 mm. by 3-4mm. Radicula Nasturtiwn-aquaticum Rendle and Britten.—Seeds (1910) planted on 22nd June, 1911. On 8th May, 1912, one had germinated. R. palustris Moench.—Seeds (1910) planted on 18th April, 1911. On 24th June, 1911, one had germinated. On 28th October, 1911, no more had germinated. Cotyledons petiolate, blade subrotund, faintly notched at the tip, entire, glabrous. Petiole 3mm. long, blade 33mm. by 23mm, First leaf simple, second leaf lyrate. Sisymbrium officinale Scop.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Apams—On the Germination of the Seeds of some Dicotyledons. 479 S. Sophia Linn.—Seeds (age uncertain) planted on 15th July, 1911. On 14th October, 1911, two had germinated. Thiaspi arvense Linn.—Fifty seeds (age uncertain) planted on 22nd October, 1910. On 23rd September, 1911, none had germinated. Dipsacacem. Dipsacus Fullonum Linn —Seeds (1910) planted on 18th April, 1911. On 28th October, 1911, several had germinated and had formed a number of leaves. Scabiosa arvensis, Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. S. succisa Linn.—Seeds (1910) planted on 8th October, 1910. On 29th April, 1911, several had germinated. Cotyledons oblong-elliptical, tapering at the base, obtuse, entire, glabrous, 74mm. by 3mm. First leaf petiolate, blade rotundate, hairy. EXMPETRACER. Empetrum nigrum Linn.—Seeds (age uncertain) planted on 22nd October, 1910. On 8rd June, 1912, none had germinated. ERIcAcrEs. Arbutus Unedo Linn.—Seeds (1910) planted on 19th April, 1911. On 8th June, 1912, none had germinated. Dabeocia cantabrica Rendle and Britten.—Seeds (1909) planted on 19th October, 1910. On 28th October, 1911, none had germinated. More seeds (1910) were planted on 12th July, 1911. On 28th October, 1911, none had germinated. Erica cinerea Linn.—Seeds (1910) planted on 22nd June, 1911. On 28th October, 1911, none had germinated. Vaccinium Myrtillus Linn.—Seedlings obtained at Lough Bray, Co. Wicklow, on 7th June, 1912. Cotyledons sessile, oblong to slightly obovate or elliptical, obtuse, entire, glabrous, 24-3 mm. by 14 mm. HuPHORBIACE®. Euphorbia exigua, Linn.—Seeds (1910) planted on 18th April, 1911. On 27th May, 1911, one had germinated. More seeds were sown on 13th July, 1911. On 25th July, 1911, nine had germinated. 480 Scientific Proceedings, Royal Dublin Society. &. Paraltias Linn.—Ten seeds (1910) planted on 3rd October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 16th September, 1911, one had germinated. Seedlings obtained in Co. Dublin on 26th July, 1909, and 29th April, 1910. Cotyledons fleshy, sessile, elliptical to oblong, entire, obtuse, glaucous, 8 mm. by 2-23 mm. FAaGAcres. Fagus sylvatica Linn.—Seedlings found at Lucan on 22nd April, 1910, with the cotyledons just emerging from the seed. Quercus Robur Linn.—Hight seeds (1911) planted on 27th January, 1912. On 10th October, 1912, none had germinated. Tho seeds had decayed in the soil. GENTIANACER. Blackstonia perfoliata Hudson.—Seeds (1910) planted on 5th October, 1910. On 18th July, 1911, none had germinated, and more seeds were sown. On 6th January, 1912, some had germinated. On 3rd June, 1912, no more had germinated. Cotyledons subrotund-deltoid, scarcely petiolate, obtuse, entire, glabrous, 1 mm. by 3? mm. Centaurion umbellatum Gilib—Seeds (1910) planted on 19th October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 26th July, 1911, five had germinated. Cotyledons lanceolate-elliptical, tapering to the base, entire, obtuse, glabrous, 13-2 mm. by 2 mm. Gentiana Amarella Linn.—Seeds (1910) planted on 3rd October, 1910. On 27th May, 1911, four had germinated. On 183th July, 1911, more seeds were sown. On 28th October, 1911, no more had germinated. Cotyledons shortly petiolate, elliptical to oblong, entire, obtuse, glabrous, 2mm. by 1 mm. GERANIACER. Erodium cicutarium L’Heéritier.—Seedlings obtained on 25th October, 1911, in Co, Dublin. Cotyledons petiolate, petiole and blade hairy, blade 3-lobed, obtuse, cordate at the base, slightly asymmetrical. Petiole 11 mm. long. Blade 5mm. by 4mm. First leaf pinnately lobed, hairy. E. maritimum L’ Heéritier.—Seedlings found in Co. Dublin on 8th June, 1910, and 14th September, 1910. Avams—On the Germination of the Seeds of some Dicotyledons. 481 Cotyledons petiolate, blade subrotund, with cordate base, entire margin and rounded apex, hairy or almost glabrous. Petiole 83-3 mm. long, blade 3mm. by 23-3 mm. First leaf trifid. E. moschatum JV Heéritier.—Seeds (1910) planted on 19th April, 1911. On 28th October, 1911, none had germinated. Geranium dissectum Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. Cotyledons petiolate, petiole hairy, blade reniform, scarcely notched at the tip. Petiole 10mm. long, blade 4mm. by 6mm. G. lucidum Linn.—Seeds (1910) planted on 10th October, 1910. On 23rd September, 1911, none had germinated. G. pusillum Linn.—Seeds (1910) planted on 19th April, 1911. On 27th May, 1911, three had germinated, and had formed several leaves, the cotyledons being withered. G. pyrenaicum N. L. Burman.—Seeds (1910) planted on 20th April, 1911. On 13th May, 1911, several had germinated. Cotyledons petiolate, blade asymmetrical, reniform, sightly mucronate. Both petiole and blade are covered with small hairs. Petiole 11-12 mm, long, blade 6 mm. long by 8 mm. wide. First leaf hairy, palmately lobed. G. Robertianum Linn.—Seeds (1910) planted on 14th July, 1911. On 28th July, 1911, several had germinated. Cotyledons petiolate, blade reniform, slightly asymmetrical, notched at the tip but not mucronate, otherwise entire, with hairs on petiole and blade. Hypocotyl hairy. Petiole 16-17 mm. long, blade 4-5 mm. by 63-9 mm. First leaf divided. G. sylvaticum Linn.—Seeds (1910) planted on 20th April, 1911. On 19th July, 1911, one had germinated, and on 26th July, 1911, two more had germinated. Cotyledons petiolate, blade reniform, asymmetrical, veined, with a sinus and mucro at the tip, otherwise entire. Hypocotyl, petiole, and blade hairy. Blade 53mm. by 10-11 mm. GUTTIFERA. Hypericum hirsutum Linn.—Seeds (age uncertain) planted on Ldth July, 1911. On 11th November, 1911, none had germinated. HA. perforatum Linn.—Seeds (1910) planted on 22nd June, 1911. On 14th July, 1911, several had germinated. Cotyledons shortly petiolate, blade ovate, glabrous, entire, obtuse or slightly notched, with a few dark spots like those on the first leaves. Petiole 15 mm., blade 4mm. by 2mm, 482 Scientific Proceedings, Royal Dublin Society. H. quadrangulum Linn.—Seeds (1910) planted on 8th October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 6th January, 1912, several had germinated. On 8th May, 1912, another had germinated ; and on 8th June, 1912, four more had germinated. Cotyledons elliptical, tapering at the base, scarcely petiolate, obtuse, entire, glabrous, 1-14 mm. by }mm. HiIpPurRIDACcE am, Aippuris vulgaris Linn.—Seeds (1910) planted on 19th April, 1911. On 11th November, 1911, none had germinated. LABIATA. Ballota nigra Viinn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Galeopsis Tetrahit Linn.—Hight seeds (1910) planted on 10th October, 1910. On 23rd September, 1911, none had germinated. Lamium anplexicaule Linn.—Seeds (1910) planted on 18th April, 1911. On 13th July, 1911, none had germinated, and more seeds were sown. On 28th October, 1911, none had germinated. Seedlings found in Co. Dublin on 27th May, 1911. Cotyledons petiolate, blade subrotund, cordate at the base, slightly mucronate, otherwise entire, glabrous. Petiole 7-9 mm. long, blade 4-5 mm. by 34-4mm. First leaves petiolate, hairy, with rotundate, serrate blade. L. purpureum Linn.—Seedlings obtained in Co. Dublin on 10th September, 1910, and at Murrough of Wicklow on 13th May, 1910. Cotyledons petiolate, blade orbicular, cordate at the base, with entire or lightly wavy margin, glabrous. Petiole 7-9 mm. long, hairy, blade 43-7 mm. by 43-7 mm. First leaves orbicular crenate. Origanum vulgare Linn.—Seeds (age uncertain) planted on 15th July, 1911. On 28th October, 1911, none had germinated. Prunella vulgaris Linn.—Seeds (1910) planted on 12th July, 1911. On 14th October, 1911, two had germinated. Cotyledons petiolate, blade subrotund, entire, obtuse, glabrous. Petiole hairy, 2 mm. long, blade 3mm. by 3mm. Salvia Verbenaca Linn.—Seeds (1910) planted on 6th October, 1910. On 19th November, 1910, many had germinated. Cotyledons petiolate, blade subreniform-rotundate, entire, obtuse, glabrous. Petiole hairy, 6mm. long, blade 5 mm, by 6¢ mm. Apams— On the Germination of the Seeds of some Dicotyledons. 488 Teucrium Scorodonia Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, one had germinated, and had produced several leaves. On 9th December, 1911, two more had germinated. Cotyledons petiolate, blade broadly ovate to subrotund, entire, obtuse, glabrous. Hypocotyl hairy. Petiole hairy,2mm.long. Blade 3mm, by 3mm. First leaves broadly ovate, crenate. LEeGuMINOS”®. Anthyllis Vulneraria, Vinn.—Twenty seeds (1910) planted on 8th October, 1910. On Ist April, 1911, eight had germinated. Cytisus scoparius Link.—Twenty-five seeds (1910) were planted on 5th October, 1910. On Ist April, 1911, twelve had germinated. Cotyledons almost sessile, elliptical, entire, obtuse, glabrous, with rather prominent veins, 7-8 mm. by 3-33 mm. First leaf ternate, hairy. Lathyrus montanus Bernh.—Five seeds (1910) planted on 5th October, 1910. On 15th July, 1911, none had germinated, and more seeds were sown. On 28th October, 1911, three had germinated. Cotyledons subterranean, first three leaves simple, fourth and fifth binate. L. pratensis Linn.--'l'wenty-five seeds (1910) plauted on 8th October, 1910. On 8th April, 1911, two had germinated, and on 13th May, 1911, two more had germinated. Cotyledons subterranean. First leaf simple. ‘Two shoots frequently come above ground from one seed. Lotus corniculatus Linn.—Seeds (1910) planted on 8th October, 1910. On 19th November, 1910, many had germinated. Cotyledons almost oblong, tapering slightly at the base, entire, glabrous, obtuse, 45mm. by 2mm. First leaf ternate. L. wliginosus Schkuhr.—Seeds (1910) planted on 20th April, 1911. On 19th June, 1911, one had germinated, and on 14th July, 1911, three more had germinated. Cotyledons resembling those of Z. corniculatus. Petiole 1 mm. long, blade 35 mm. by 13 mm. Medicayo lupulina Linn.—Seeds (1910) planted on 8th October, 1910. On 24th June, 1911, four had germinated. Cotyledons nearly sessile, oblong, entire, obtuse, glabrous, 73 mm. by 2mm. First leaf simple, hairy. SCIENT, PROC. R.D.S., VOL, XIII., NO. XXXIII. 4c 484 Scientific Proceedings, Royal Dublin Society. Ononis repens Linn.—Twenty seeds (1910) planted on 8th October, 1910. On 13th May, 1911,two had germinated, Seedlings found at Portrane on 29th April, 1910. Cotyledons broadly elliptical to suborbicular, tapering to the base, obtuse, entire, somewhat fleshy, hairy, 8-9 mm. by 5mm. First leaf simple, hairy, with adnate stipules and a joint between the petiole and blade. Trifolium pratense Linn.—Cotyledons petiolate, blade broadly elliptical to oblong, obtuse, entire, glabrous. Petiole 4-6 mm. long, blade 5-6 mm. by 34-4mm. First leaf simple, hairy, stipulate, second leaf ternate. T. procumbens \inn.—Cotyledons petiolate, blade oblong, entire, obtuse, glabrous. Petiole 14 mm. long, blade 2mm. by 1mm. First leaf simple. T. repens Linn.—Cotyledons petiolate, blade oblong, tapering slightly to the base, obtuse, entire, glabrous. Petiole 2}-3 mm. long, blade 33 mm. by 13-2mm. First leaf simple, second leaf ternate. Ulex ewropeus Linn.—'l'wenty-five seeds (1910) planted on 8th October, 1910, On 4th March, 1911, one had germinated, and on 26th July, 1911, six more had germinated. More seeds (1910) were planted on 26th A pril, 1911. On 26th July, 1911, four had germinated, and on 28th October, 1911, five more had germinated. First leaves usually ternate, sometimes bilobed. Occasionally all the leaves are simple. U. nanus Forster.—Ten seeds (age uncertain) planted on 19th July, 1911. On 16th September, 1911, two had germinated, and on 28th October, 1911, six more had germinated. Cotyledons subsessile, oblong-ovate, entire, obtuse, glabrous, 8 mm. by 5mm. First leaves hairy, usually ternate. Vicia Oracca Linn.—'l'wenty seeds (1910) planted on 6th October, 1910. On 26th December, 1910, five had germinated, and on 29th April, 1911, three more had germinated. Cotyledons subterranean. First leaves simple, subulate, 15 mm. long, with broad base. ‘lwo shoots frequently come above ground from one seed. V. sepium Linn.—'wenty seeds (1910) pianted on 8th October, 1910. On 18th July, 1911, none had germinated, and more seeds were sown. On 6th January, 1912, one had germinated. On 8th June, 1912, another had germinated. The seeds were then removed, scraped, and replanted. On 6th July, 1912, seven had germinated, and on 24th July, 1912, eight more had germinated. Cotyledons subterranean. First two leaves simple, Apams—On the Germination of the Seeds of some Dicotyledons. 485 V. sywatica Linn.—Twenty seeds (1908) planted on 22nd October, 1910. On 23rd September, 1911, none had germinated. LENTIBULARIACES. Pinguicula vulgaris Linn.—Seeds (1910) planted on 28th July, 1911. On 3rd June, 1912, none had germinated. LInacez. Linum catharticum Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Radiola linoides Roth.—Seeds (1909) planted on 6th May, 1911. On 14th October, 1911, none had germinated. LyYTHRACER. Lythrum Satearia Linn,—Seeds (1910) planted on 18th April, 1911. On 13th July, 1911, none had germinated, and more seeds were sown. On 28th October, 1911, none had germinated. Peplis Portula Linn.—Seeds (1909) planted on 6th May, 1911. On 14th October, 1911, none had germinated. Matvacra, Lavatera arborea Linn.—Twenty-five seeds (age uncertain) planted on 17th October, 1910. On 23rd September, 1911, none had germinated. Matva sylvestris Linn.—Seeds (1910) planted on srd October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 28th July, 1911, some had germinated, and on 28th October, 1911, nine more had germinated. Cotyledons petiolate, blade cordate, entire, glabrous, obtuse, palmately veined. Petiole 10 mm. long, blade 6-7 mm. by 7-8 mm. Moracez. Ficus Carica Linn.—Seeds (1911) planted on 4th May, 1912. On 25th July, 1912, many had germinated. Cotyledons shortly petiolate, blade subrotund, faintly notched at the tip, entire, glabrous, with the veins apparent on the under side. Petiole 1-13 mm. long, blade 5-63 mm. by 4-5 mm. Myricace. Myrica Gale Linn.—Seeds (age uncertain) planted on 14th July, 1911. On 8th June, 1912, none had germinated. 402 486 Scientific Proceedings, Royal Dublin Society. NyYMPH#ACER. Nymphea lutea Linn.—Seeds (age uncertain) planted on 15th July, 1911. On 3rd June, 1912, none had germinated. OLEACER. Fraximus excelsior Linn.—Seeds (1910) planted on 7th December, 1910. On 8th June, 1912, one was germinating, but had not yet come above ground. Seedlings found at Lucan on 22nd April, 1910. Ligustrum vulgare Linn.—Seeds (1910) planted on 22nd October, 1910. On 19th June, 1911, three had germinated, and on 8th July, 1911, three more had germinated. Cotyledons with short petiole, blade broadly elliptical, veined, entire, obtuse, glabrous. Petiole 1 mm. long, blade 9-14 mm. by 64-73 mm. ONAGRACER. Circaea lutetiana Linn.—Seeds (1911) planted on 27th January, 1912. On 8th June, 1912, three had germinated and had formed several leaves, the cotyledons being withered. Cotyledons green, petiolate. Epilobium montanum Linn.—Seedlings found in Co. Dublin on 14th September, 1910. Cotyledons shortly petiolate, blade subrotund to spatulate, entire, glabrous. Length, including petiole, 34-6 mm.; breadth 2-3 mm. Adventitious roots come off very early above the cotyledons. OROBANCHACES. Orobanche Hedere Duby.—-Seeds (age uncertain) planted on 22nd October, 1910. On 28th October, 1911, none had germinated. OXALIDACER. Oxalis Acetosella Linn.—Seedlings found at Lough Bray, Co. Wicklow, on 3rd June, 1910. Cotyledons suborbicular, notched at the tip, entire, glabrous, shortly petiolate. Petiole 13 mm. long, blade 7 mm. by 54 mm. PAPAVERACEE. Corydalis claviculata DC.—Five seeds (1910) planted on 3rd October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 28th October, 1911, none had germinated. Seedlings obtained at Powerscourt on 1st May, 1912. Cotyledons petiolate, blade lanceolate, entire, pointed, glabrous, with several veins. Petiole 35 mm. long, blade 5 mm. by 14 mm. First leat petiolate with two leaflets, second leaf petiolate with three leaflets. Avams—On the Germination of the Seeds of some Dicotyledons. 487 Fumaria officinalis Benth.—Seedlings found at the Murrough of Wicklow on 15th May, 1910. Cotyledons sword-shaped, tapering at the base, glabrous, entire, 30 mm. by 24 mm. First leaf divided. Glaucium flavum Crantz.—Seedlings found at the Murrough of Wicklow on 13th May, 1910. Cotyledons shortly petiolate, blade ovate-lanceolate, obtuse, entire, glabrous. Petiole 14 mm. long, blade 5-7 mm. by 1-2 mm. First leaf spatulate or trifid with a few scattered hairs. Second leaf trifid. Meconopsis cambrica Viguier.—Seeds (1910) planted on 6th October, 1910. On 8th April, 1911, several had germinated. Papaver dubium Linn.—Seedlings found in Co. Dublin on 17th July, 1911. Cotyledons sessile, oblong, entire, obtuse, glabrous, 4-5 mm. by 3 mm. P. Rhoeas Linn.—Seeds (1910) planted on 22nd June, 1911. On 14th October, 1911, several had germinated. Cotyledons subsessile, linear—oblong, entire, obtuse, glabrous, 2 mm. by 4mm. First leaf simple. PLANTAGINACE®. Plantago lanceolata Linn.—Seedlings obtained at Grey Abbey, Co. Down, on 26th August, 1910. i Cotyledons linear, entire, glabrous, 12-22 mm .by $-3 mm. P. niajor Linn.—Seeds (1910) planted on 12th July, 1911 On 28th October, 1911, none had germinated. P. maritima Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. PLUMBAGINACE. Limonium vulgare Mailler.—Seeds (1910) planted on 22nd June, 1911. On 28th October, 1911, none had germinated. Statice maritima Miller.—Seeds (1910) planted on 8th October, 1910. On Ist April, 1911, six had germinated. Cotyledons oblong, tapering slightly to the base, entire, obtuse, glabrous, 8mm. by 13 mm. POLYGALACES. Polygaia vulgaris Linn.—Ten seeds (1910) planted on 3rd October, 1910. On 27th May, 1911, one had germinated. On 12th July, 1911, more seeds were planted, and on 28th October, 1911, two had germinated. Cotyledons shortly oblong, tapering into the short petiole, obtuse, entire, glabrous, 44-6 mm. by 24-4mm. First leaf lanceolate. 488 Scientific Proceedings, Royal Dublin Society. PoLyGonacEeZ. Oxyria digyna Hill.—Seeds (1909) planted on 6th May, 1911. On 3rd June, 1911, several had germinated, and had produced one or two leaves. Cotyledons petiolate, blade rather fleshy, ovate-lanceolate, sharply marked off from the petiole, entire, obtuse, glabrous. Petiole 53 mm. long, blade 7mm. by 34mm. Polygonum aviculare Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. P. Convolvulus Linn.—Cotyledons shortly petiolate, oblong, glabrous, 17-22 mm. by 3 mm. P. Hydropiper Linn.—Seeds (age uncertain) planted on 14th July, 1911. On 28th October, 1911, none had germinated. P. lapathifolium Linn.—Seeds (1910) planted on 19th April, 1911. On 7th May, 1911, one had germinated. On 28th October, 1911, no more had germinated. Cotyledons lanceolate, tapering at the base, obtuse, entire, with short seattered bristles, 12mm. by 3mm. First leaf narrowly lanceolate, acute, tapering at the base into the short petiole, with the stipules forming an ochrea. P. Persicaria Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated. On 16th September, 1911, two more had germinated. Cotyledons shortly petiolate, obovate—oblong, obtuse, entire, glabrous, 6-7 mm. by 23-3 mm. Rumex Acetosella Linn.—Seeds (1910) planted on 12th’July, 1911. On 28th July, 1911, several had germinated. On 16th September, 1911, some more had germinated. Seedlings found at Carrickmines on 15th April, 1910. Cotyledons narrowly spatulate or lanceolate, tapering at the base, obtuse, entire, glabrous, 6-10 mm. by 14-21 mm. First leaf spatulate. R. crispus Linn.—Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, several had germinated, and on 16th September, 1911, many had germinated. Cotyledons petiolate, blade elliptical, entire, obtuse, glabrous. Petiole 2-3 mm. long, blade 9mm. by 23-3 mm. R. maritimus Linn.—Seeds (1910) planted on 19th April, 1911. On 28th October, 1911, none had germinated. Apams— On the Germination of the Seeds of some Dicotyledons. 489 R. pulcher Linn.—Seeds (1910) planted on 20th April, 1911. On 26th July, 1911, five had germinated. Cotyledons petiolate, blade oblong, scarcely symmetrical, entire, obtuse, glabrous. Petiole 7 mm. long, blade 9 mm. by 23-33 mm. PRIMULACER. Anagallis arvensis Linn.—Seeds (1910) planted on 10th October, 1910. On 27th May, 1911, some had germinated, and had formed several leaves. Glaux maritima Linn.—Seeds (1909 probably) planted on 6th May, 1911. On 28th July, 1911, several had germinated. Cotyledons lanceolate, tapering at the base, entire, subacute, glabrous, 5-54 mm. by 1 mm. Lysimachia vulgaris Linn.—Seeds (1910) planted on 22nd June, 1911. On 28th October, 1911, none had germinated. Primula veris Linn.—Seeds (1910) planted on 10th October, 1910. On 4th March, 1911, many had germinated. Cotyledons shortly petiolate, blade ovate, entire, obtuse, with one vein, downy. Petiole 2-3mm. long, blade 4 mm. by 2-24mm. First leaf downy, slightly crenate. Samolus Valerandi Linn.—Seeds (1910) planted on 5th October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 8th June, 1912, several had germinated. Cotyledons elliptical, tapering at the base, obtuse, entire, glabrous, 1-14 mm. by } mm. RANUNCULACER. Anemone nemorosa Linn.—Seeds (1910) planted on 18th April, 1911. On 28th October, 1911, none had germinated. Aquilegia vulgaris Linn.—Thirty-three seeds (1909) planted on 18th October, . 1910. On 23rd September. 1911, none had germinated. Ranunculus bulbosus Linn.—Seedlings obtained in Co. Dublin on 14th September, 1910. Cotyledons with long petioles slightly united at the base, blade subrotund, entire, glabrous, three-veined. Petiole 9-14 mm. long, blade 7-8 mm. by 54mm. R. Lingua Linn.—Seeds (1909) planted on 6th May, 1911. On 14th July, 1911, several had germinated. Cotyledons petiolate, blade subrotund or shortly oblong, entire, slightly notched at the tip, glabrous. Petiole 4-5 mm., blade 74-8 mm. by 55mm. First leaf broadly ovate, crenate. R. sceleratus Linn.—Seeds (age uncertain) planted on 6th May, 1911. On 14th October, 1911, none had germinated. 490 Scientific Proceedings, Royal Dublin Society. Thalictrum fiacum Linn.—Seeds (age uncertain) planted on 15th July, 1911. On 28th October, 1911, one had germinated. On 11th November, 1911, no more had germinated. Cotyledons lanceolate, tapering into the petiole, entire, obtuse, glabrous, 8mm. by 1}mm. First leaf petiolate, ternate. T. minus Linn.—Seeds (1909) planted on 6th May, 1911. On 14th October, 1911, none had germinated. RESEDACER. Reseda Luteola Linn.—Seeds (1910) planted on 3rd October, 1910. On 19th November, 1910, some had germinated. RHAMNACES. Ihamnus catharticus Linn.—Seedlings obtained at Lough Ree on 16th July, 1910. Cotyledons shortly petiolate, obreniform, entire, glabrous. Petiole 2mm. long, blade 12-14 mm. by 15-18 mm. R. Frangula Linn.—Seeds (1910) planted on 22nd June, 1911. On 28th July, 1911, one had germinated, and on 8th June, 1912, another had germinated, Cotyledons subterranean. First leaves small, narrow, later ones crenate-serrate. RosacEZs. Agrimonia Eupatoria Linn.—Twenty seeds (1910) planted on 8th October, 1910. On 29th April, 1911, several had germinated. Hypocotyl and cotyledons hairy. Cotyledons petiolate, blade fleshy, shortly oblong, slightly notched or truncate at the tip, notched at the base, otherwise entire. Petiole 7 mm. long, blade 43-53 mm. by 4-43 mm. First leaf simple, petiolate, hairy, with serrate margin. Orategus Oxyacantha Linn.—Ten seeds (1910) planted on 29th September, 1910. On 2nd April, 1912, six had germinated. Some seeds (1910) were freed from the stone and planted on 26th April, 1911. On 8th June, 1912, none had germinated. Dryas octopetala Linn.—Seeds (age uncertain) planted on 19th October, 1910, On 28th October, 1911, none had germinated. Geum rivale Linn.—Seeds (1910) planted on 19th April, 1911. On 11th November, 1911, none had germinated. G. urbanum Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Cotyledons petiolate, blade entire, obtuse, ovate, glabrous, Petiole 23 mm. long, blade 53 mm. by 33 mm. Apams—On the Germination of the Seeds of some Dicotyledons. 491 Potentilla erecta Hampe.—Seedlings found at L. Bray, Co. Wicklow, on 7th June, 1911. Cotyledons shortly petiolate, blade subrotund, entire, obtuse, glabrous. Petiole 1-1} mm. long, blade 23-3} mm. by 24-3 mm. First leaf simple, serrate. P. reptans \.inn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. P. sterilis Garcke.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Poterium Sanguisorba Linn.—Seeds (1910) planted on n 14th July, 1911. On 8th May, 1912, eight had germinated, Prunus Amygdalus Stokes.—Six seeds (age uncertain) planted on 15th March, 1911. On 22nd June, 1911, one had germinated, and was 6 inches above ground. On 28th October, 1911, no more had germinated. Five seeds were planted on 26th June, 1911. On 18th July, 1911, one had germinated. On 14th October, 1911, no more had germinated. Twelve seeds were planted on 2nd April, 1912. On 6th July, 1912, one had germinated. Cotyledons in all cases subterranean. P. domestica Linn.—Seeds (1911) of Greengage planted on 22nd July, 1911, On 18th April, 1912, four had germinated. Cotyledons come above ground and resemble those of P. spinosa. P. Persica Stokes.—Hight seeds (1911) planted on 7th October, 1911. On 18th April, 1912, one had germinated, and on 3rd June, 1912, another had germinated. Cotyledons subterranean. P. serotina Ehrhart—Twenty seeds (1911) planted on 7th October, 1911, On 18th April, 1912, five had germinated. Cotyledons subterranean. P. spinosa Linn.—Ten seeds (1910) planted on 3rd October, 1910. On 2nd April, 1912, one had germinated, and on 13th April, 1912, another had germinated. Seeds (1910) freed from stone were planted on 26th April, 1911. On 2nd April, 1912, one had germinated. On 10th October, 1912, no more had germinated. Cotyledons fleshy, spatulate, shortly petiolate, entire, glabrous, 11 mm. by 5mm. First leaf simple, serrate, stipulate. Pyrus Aria Khrhart.—Seeds (1909 probably), planted on 6th May, 1911. On 8th June, 1912, none had germinated. P. Aucuparia Ehrhart.—Six seeds (1910) planted on 29th September, 1910, On 8th June, 1912, none had germinated. Seedlings obtained at Lough Bray, Co. Wicklow, on 7th June, 1912. SCIENT, PROC. R.D.S., VOL. XIII., NO. XXXITI. 4D 492 Scientific Proceedings, Royal Dublin Society. P. communis Linn.—Twenty-four seeds (1911) planted on 2nd April, 1912. On 25th July, 1912, one had germinated, and was 33 inches above ground. On 10th October, 1912, no more had germinated. Cotyledons similar to those of Apple. P. Malus Linn.-—Seeds (1910) planted on 8th March, 1911. On 8th May several had germinated. Seeds (1910) pianted on 10th June, 1911, had germinated on 13th July, 1911. 250 seeds (1911) planted on 2nd April, 1912. Ou 10th October, 1912, none had gorminated. Rosa arvensis Hudson.—Seeds (1910) planted on 14th July, 1911. Ou 2nd April, 1912, several had germinated. On 8th May, 1912, twenty-eight had germinated. Cotyledons shortly petiolate, blade oblong, obtuse, entire, with capitate hairs on the margin, A few capitate hairs occur also on the petiole and hypocotyl. Petiole 2 mm. long, blade 7 mm. by 35mm. First leaf simple or ternate, serrate. R. canina VLinn.—Seeds (1910) planted on 14th July, 1911. On 2nd April, 1912, some had germinated. On 9th May, 1912, twelve had germinated. Cotyledons petiolate, blade oblong-elliptical, obtuse, entire. Capitate hairs occur on the hypocotyl, petiole, and margin of blade. Petiole 3mm. long, blade 8mm. by 5mm. First leaf ternate. R. villosa Linn.—Fifty seeds (1910) planted on 29th September, 1910. On 13th April, 1912, four had germinated, and on the 8th May, 1912, five more had germinated. Cotyledons petiolate, blade oblong, obtuse, entire. The hypocotyl, petiole, and margin of blade are covered with capitate hairs. Petiole 4 mm. long, blade 7mm. by 4mm. First leaf simple or three-lobed. Rubus fruticosus Linn.—Seeds (1910) planted on 29th September, 1910. On 29th April, 1911, serveral had germinated. Seeds of Blackberry taken from the excreta of birds were planted on 8rd October, 1910. On 27th May, 1911, two had germinated, and on 14th July, 1911, twelve more had germinated. Cotyledous shortly petiolate, blade oblong to subtrotund, obtuse, entire. peatneroe bairs occur on the hypocotyl, petiole, and blade. Petiole 13-23 mm. long, blade 8-44mm. by 14-85 mm. First leaf simple, petiolate, with subrotund, serrate blade. R. ideus Linn.—Seeds (1910) planted on 29th September, 1910. On 8th May, 1911, many had germinated. Seeds of Raspberry that were just ripe were aplanced on 6th July, 1911. On 8th May, 1912, four had germinated. Cotyledons petiolate, blade oblong, entire, obtuse. Hypocotyl and Apams— On the Germination of the Seeds of some Dicotyledons. 498 cotyledons sparsely hairy. Petiole 1mm. long, blade 4mm. by 2mm. First leaf simple, hairy, petiolate, cordate, with serrate margin. R. sazatilis Linv.—T' wo seeds (1907).planted on 6th May, 1911. On 14th October, 1911, none had germinated. RuBIACEs. Asperula eynanchica Linn.—Seeds (1910) planted on 19th April, 1911. On 28th October, 1911, none had germinated. Galium Aparine Linn.—Seeds (1910) planted on 26th April, 1911. On 26th May, 1911, many had germinated, and had produced the first leaves. G. boreale Linn.—Seeds (1909) planted on 6th May, 1911. On 8th July, 1911, one had germinated, and on 14th July, 1911, another had germinated. On 14th October, 1911, no more had germinated. Cotyledons shortly petiolate, blade subrotund-ovate, almost obtuse entire, glabrous. Petiole 2mm. long, blade 3-4mm. by 24-3 mm. First leaves in whorls of four, two of these being much larger than the other two. G. erectwn Huds.—Seeds (1910) planted on 19th April, 1911. On 19th June, 1911, one had germinated. On 28th October, 1911, no more had germinated. Cotyledons petiolate, blade ovate, entire, obtuse, glabrous. Petiole 3mm. long, blade 7 mm. by 44 mm. G. Mollugo Linn.—Seeds (1910) planted on 19th April, 1911. On 14th July, 1911, one had germinated. On 28th October, 1911, no more had germinated. First leaves of seedling in whorls of four, all of the same size. G. verum Linn.—Seeds (1910) planted on 12th July, 1911. On 16th September, 1911, many had germinated. Cotyledons petiolate, blade oblong, slightly notched at the tip, entire, glabrous. Petiole 1-1} mm. long, blade 5mm. by 2-25mm. First leaves in whorls of four. Rubia peregrina Linn.—Ten seeds (1909) planted on 17th October, 1910. On 13th May, 1911, one had germinated, and on 20th June, 1911, another had germinated. On 23rd September, 1911, no more had germinated. Cotyledons subterranean. First leaves in whorls of four, two being larger than the other two. Sherardia arvensis Linn.—Seeds (1910) planted on 18th April, 1911. On 27th May, 1911, three had germinated. On 13th July, 1911, two more had germinated, and more seeds were sown. On 26th July, 1911, many had germinated. 4p2 494 Scientific Proceedings, Royal Dublin Society, Rutacex. Citrus Aurantium Linn.—Twenty seeds (1911) planted on 4th May, 1912. On 22nd July, 1912, one had germinated. C. Medica Linn., var. Limonum.—'Ten seeds (1911) planted on 4th May, 1912. On 22nd July, 1912, three had germinated. Cotyledons subterranean. SALICACEH. Salix Caprea Linn.—Seeds collected on Ist June, 1911, were planted on 10th June, 1911. On 8th June, 1912, none had germinated. S. vininalis Linn.—Seeds (1910) planted on 20th April, 1911. On 3rd June, 1912, none had germinated. Seeds collected on 19th May, 1911, were planted on 10th June. On 8th June, 1912, none had germinated. SAXIFRAGACER. Parnassia palustris Linn.—Seeds (1910) planted on 6th October, 1910. On 13th July, 1911, none had germinated, and more seeds were sown. On 28th October, 1911, none had germinated. Ribes Grossularia Linn.—Cotyledons shortly petiolate, blade elliptical, entire, with thickened apex, glabrous. Petiole 2-3 mm. long, blade 5 mm. by 23-34 mm. First leaf simple, petiolate, deeply toothed, with bristly hairs. Saxifraga rosacea Moench..—Seeds (1910) planted on 22nd June, 1911. On 6th January, 1912, one had germinated. On 8rd June, 1912, no more had germinated. S. Geum Linn.—Seeds (1910) planted on 19th April, 1911. On 28th October, 1911, none had germinated. S. stellaris Linn.—Seeds (age uncertain) planted on 6th May, 1911. On 14th October, 1911, none had germinated. S. Tridactylites Linn.—Seeds (age uncertain) planted on 15th July, 1911. On 28th October, 1911, none had germinated. ScroPHULARIACE. Bartsia Odontites Huds.—Seeds (1910) planted on 3rd October, 1910. On 8th April, 1911, several had germinated. On 8th November, 1911, no more had germinated. Cotyledons subrotund or shortly oblong, sessile, entire, glabrous, 14-13 mm. by 7-1 mm. Digitalis purpurea Linn.—Seedlings found in Co. Dublin on 14th July, 1911. Cotyledons shortly petiolate, blade ovate-rotundate or rhomboid, obtuse, entire, nearly glabrous. Petiole and hypocotyl hairy. Length, including petiole, 34-5 mm.; breadth 24-34 mm. Apvams— On the Germination of the Seeds of some Dicotyledons. 495 Euphrasia officinalis Linn.—Seeds (1910) planted on 8rd October, 1910. On 8th April, 1911, several had germinated. On 8th November, 1911, no more had germinated. Cotyledons subrotund, sessile, entire, glabrous, 1-1} mm. by 2-2 mm. ’ Lathraea Squamaria Linn.—Seeds (1909 probably) planted on 17th October, 1910. On 23rd September, 1911, none had germinated. Melampyrum pratense Linn.—Cotyledons persistent until the flowers appear, obovate-spatulate, tapering to the base, entire, obtuse, glabrous, 20-44 mm. by 5-9 mm. Pedicularis palustris Linn.—Seeds (1910) planted on 3rd October, 1910. On 19th June, 1911, none had germinated. On 13th July, 1911, one had germinated, and more seeds were sown. On 6th November, 1911, no more had germinated. Cotyledons shortly petiolate, blade shortly oblong, slightly indented at the tip, entire, glabrous. Petiole 1 mm. long, blade 34 mm. by 2mm. Rhinanthus Crista-Galli Linn.—Forty seeds (1910) planted on 3rd October, 1910. On ist April, 1911, seventeen had germinated, and ten of these were removed. On 27th May, 1911, five only survived, and these were pale and sickly-looking. On 19th June, 1911, all had died down. On 8th November, 1911, no more had germinated. Cotyledons almost sessile, elliptical, entire, obtuse, glabrous, 44 mm. by 3mm. First pair of leaves crenate, hairy. Scrophularia aquatica Linn.—Seeds (1909) planted on 15th July, 1911. On 28th July, 1911, some had germinated. Cotyledons petiolate, blade deltoid-subrotund, entire, obtuse, glabrous. Petiole 24 mm. long, blade 24 mm. by 3 mm. Veronica Beccabunga Linn.—Seeds (1910) planted on 14th July, 1911. On drd June, 1912, none had germinated. V. montana Linn.—Cotyledons petiolate, blade rotundate, entire, obtuse, glabrous. Petiole 14-2 mm. long, blade 443-5 mm. by 4-44 mm. V. scutellata Linn.—Seeds (1910) planted on 14th July, 1911. On 28th October, 1911, none had germinated. SoLANACEZ. Hyoscyamus wiger Linn.—Seeds (age uncertain) planted on 15th July, 1911. On 28th October, 1911, none had germinated. Solanum Dulcamara Linn.—Seeds (1910) planted on 3rd October, 1910. On 29th April, 1910, several had germinated. 496 Scientific Proceedings, Royal Dublin Society UnMACcE®. Uimus glabra, Huds.—Cotyledons shortly petiolate, blade broadly obovate, notched at the base, with pointed auricles, entire, truncate or slightly indented at the tip, hairy. Petiole and hypocotyl hairy. Petiole 13-3 mm. long, blade 73-9 mm. by 6-7 mm. Cotyledons green on upper, whitish on under surface. First leaf lanceolate, serrate, hairy. UMBELLIFERS. Ajgopodium Podagraria Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Aithusa Cynapium Linn.—Twenty-five seeds (1910) planted on 8th October, 1910. On Ist April, 1911, eleven had germinated. On 29th April, 1911, no more had germinated. Cotyledons lanceolate, tapering to the base, glabrous, entire, 124 mm. by 2-24 mm. First leaf palmately lobed. Angelica sylvestris Linn.—Seeds (1910) planted on 22nd June, 1911. On 28th July, 1911, some had germinated. On 28th October, 1911, no more had germinated. Cotyledons linear-lanceolate, tapering at the base, entire, pointed, glabrous, one-nerved, 19mm. by 1} mm. Anthriscus sylvestris Hoffm.—Twenty-five seeds (1910) planted on 8th October, 1910. On 4th March, 1911, twenty-one had germinated. Cotyledons linear-lanceolate, tapering to the base, entire, glabrous, 382-385 mm. by 2-24 mm. First leaf divided, with scattered hairs. Apium nodifiorum H. G. Reichb.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, three had germinated. On 8th November, 1911, another had germinated. Cotyledons elliptical-lanceolate, tapering at the base, obtuse, entire, glabrous, 7-74 mm. by 1-14 mm. First leaf simple, broadly ovate, crenate. Caucalis nodosa Scop.—Seeds (1910) planted on 10th October, 1910. On 19th November, 1910, several had germinated, and on 26th December, 1910, the first leaf had developed. Cotyledons linear, tapering at the base, entire, glabrous, 12-18 mm. by 14-14 mm. First leaf divided with scattered hairs. Cherophyllum temulum Linn.—Seeds (1910) planted on 20th April, 1911. On 3rd June, 1911, five had germinated. Cotyledons linear-lanceolate, tapering to the base, entire, glabrous, acute 47 mm. by 34mm. First leaf divided, hairy. ApamMs—On the Germination of the Seeds of some Dicotyledons. 497 Conium maculatum Linn.—Seeds (1910) planted on 18th April, 1911. On 27th May, 1911, several had germinated, and had formed the first leaf. Seedlings found at Murrough of Wicklow on 18th May, 1910. Cotyledons with long petiole, blade lanceolate, entire, glabrous, obtuse, with prominent veins. Petiole 7-15 mm. long, blade 6-12 mm. by 2-44 mm. First leaf ternately or biternately divided. Crithnum maritinum Linn.—Twenty-five seeds (1909) planted on 18th October, 1910. On 23rd September, 1911, none had germinated. Daucus Carota Linn. Seeds (1910) planted on 12th July, 1911. On 28th July, 1911, some had germinated. On 16th September, 1911, many had germinated. Seedlings found at Murrough of Wicklow on 13th May, 1910. Cotyledons linear-oblong, tapering to the base, pointed, entire, glabrous, 16-24mm. by 1-2mm. First leaf divided, hairy. Eryngium maritimum Linn.—Seeds (1910) planted on 18th April, 1911. On 13th July, 1911, none had germinated, and more seeds were sown. On 28th October, 1911, none had germinated. Seedlings found at Malahide on 24th May, 1912. Cotyledons petiolate, slightly connate at the base, blade oblong- lanceolate, subacute, entire, somewhat fleshy, but with evident midrib and lateral veins. Petiole 5mm. long, blade 15mm. by 4mm. First leaf petiolate, simple, blade subrotund, serrato-spinose. Haloscias scoticum Fries.—Twenty seeds (1909) planted on 17th October, 1910. On 28rd September, 1911, none had germinated. Heracleum Sphondylium Linn.~-Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. On dth April, 1912, many had germinated. Seedlings found at Dalkey on 6th May, 1910. Cotyledons petiolate, blade oblong to subelliptical, obtuse, entire, glabrous, with three veins proceeding from the base. Petiole 6-10 mm. long, blade 63-8 mm. by 2-5}mm. First leaf simple, petiolate, reniform to cordate, hairy, with serrate or crenate margin. Hydrocotyle culqaris Linn.—Seeds (age uncertain) planted on 15th July, 1911. On 28th October, 1911, none had germinated. Oenanthe aquatica Poir.—Seeds (age uncertain) planted on 14th July, 1911. On 16th September, 1911, two had germinated. On 28th October, 1911, no more had germinated. Cotyledons petiolate, narrowly lanceolate, entire, glabrous, pointed. | Petiole 3-5 mm. long, blade 8-10mm. by 2mm, First leaf three-lobed. O. crocata Linn.—Seedlings found in Co. Wicklow on 19th July, 1910. Cotyledons oblanceolate, obtuse, glabrous, with entire margin, tapering gradually to the base, 29 mm. by 3 mm, 498 Scientific Proceedings, Royal Dublin Society. O. fistulosa Linn.—Seeds (1910) planted on 20th April, 1911. On 3rd June, 1911, three had germinated. On 26th July, 1911, eight more had germinated. é Cotyledons narrowly lanceolate, tapering into the petiole, entire, glabrous, apiculate at the tip, 213-22 mm. by 2-24 mm. First leaf divided. O. Lachenalii C. C. Gmelin.—Seeds (age uncertain) planted on 14th July, 1911. On 2nd October, 1911, two had germinated. On 3rd June, 1912, no more had germinated. : Cotyledons petiolate, blade lanceolate, entire, glabrous, pointed. Length, including petiole, 1lmm.; breadth 2mm. First leaf ternate, the middle lobe being sometimes trifid. Pimpinella major Huds.—Seeds (age uncertain) planted on 14th July, 1911. On 28th October, 1911, none had germinated. P. Saxifraga Linn.—Seeds (1910) planted on 12th July, 1911. On 28th October, 1911, none had germinated. Sanicula ewropea Linn.—Seeds (1911) planted on 27th January, 1912. On 8th June, 1912, none had germinated. Smyrnium Olusatrum Linn.—Seedlings tound in Co. Dublin on 8th April, 1910, Cotyledons with long petiole, united at the base, blade nearly orbicular, entire, glabrous. Petiole 50 mm. long, blade 22 mm. by 17-22 mm. First leaf ternate. Urricacem. Urtica dioica Linn.—Seeds (1910) planted on 8th October, 1910. On 13th May, 1911, several had germinated. VALERIANACER. Valerianella dentata Pollich.Seeds (1910) planted on 18th April, 1911. On 27th May, 1911, several had germinated and had formed the first leaf. Cotyledons shortly petiolate, blade rotundate, slightly emarginate, entire, glabrous. Petiole 3 mm. long, blade 5 mm. by 4-45 mm. First leaves elliptical with short petiole. ‘VIOLACER. Viola canina Linn.—Cotyledons petiolate, blade oblong, entire, truncate, glabrous, three-veined, Petiole 3 mm. long, blade 5-6 mm. by 3-3} mm. First leaf rotundate, hairy, crenate. V. hirta Linn.—Ten seeds (1910) planted on 3rd October, 1910. On 138th May, 1911, two had germinated. On 12th July, 1911, more seeds were sown. On 28th October, 1911, no more had germinated. Cotyledons spatulate, tapering to the base, entire, obtuse, glabrous, 7-8 mm. by 2-34 mm. First leaf hairy. V. palustris Linn.—Seeds (age uncertain) planted on 14th July, 1911. On 28th October, 1911, none had germinated, Aviams—On the Germination of the Seeds of some Dicotyledons. 499 Vivacea. Vitis vinifera Linn.—'l'wenty-five seeds (1911) planted on 2nd April, 1912. On 25th July, 1912, fourteen had germinated, and had formed several leaves. Cotyledons petiolate, blade ovate, entire, pointed, glabrous, five- veined. Petiole 3-8 min. long, blade 20-24 mm. by 11-17 mm. EXPLANATION OF THE FiIGuREs. The cotyledons only are shown, and they have not been drawn to any particular seale. The actual dimensions are given in the description of each species :— 1. Cynoglossum officinale. OY, Chisime ceonentive, ep bycopsisiarvensis: 28. Lotus corniculatus. 3. Lonicera Periclymenum . 29, Ononis repens. 4. Lychnis dioica. 50. Malva sylvestris. d= Spergularial rubra: 31. Epilobinm montanum. 5a.Transverse section of same. 32. Corydalis claviculata. 6. Atriplex laciniata. 33. Statice maritima. 7. Salicornia europaea. $4, Polygala vulgaris. 7a. Transverse section of same. 35. Polygonum lapathifolium. 8. Suada maritima. SOE Pienulieoria: 9, Carlina vulgaris. 37. Rhamuus catharticus, 10. Centaurea Scabiosa. 38. Argrimonia Hupatoria. 11. Chrysanthemum Leucanthe- SORIC Cui uLbanun: nN 40. Rubus fruticosus. 12. Cnicus arvensis. 41. Bartsia Odoutites. 13. Hypocheeris glabra. 42. Digitalis purpurea. 14, Lapsana communis. 43. Euphrasia officinalis. 15. Leontodon nudicaulis, 44. Melampyrum pratense. 16. Senecio sylvaticus. 45. Khinanthus Crista-Galli. 17. Sonchus oleraceus. 46. Veronica montana. 18. Tragopogon pratensis. 47. Ulmus glabra. 19. Alliaria officinalis. AQ, Zinn Crmerstiveen, 20, Brassica arvensis. 49. Anthriscus sylvestris. 21. Scabiosa suceisa. 50. Conium maculatum. 22. Gentiana Amarella. Pie Cancale nodGaa: 23. Erodium cicutarium. ROM Valentanalinn dentin 24, Geranium pyrenaicum. 5 Waal Gann, 25. Geraniuin ltobertianum. a, WA Indian. 26. Lamium amplexicaule. SCIENT. PROC. R.D.S., VOL. XIII., NO. XXXIII, 45 SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XXXIV. 8 1 9 17 24 19 20 25 28 29 23 27 18 26 36 31 37 38 30 34 35 46 33 32 42 45 47 48 39 41 Q 49 43 52 44 50 51 53 54 SHAPE OF COTYLEDONS. ra SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamium, Williamson). By T. Jonson, pD.sc., ¥.L.S. Plates I-III.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorez H. Peruysrives, _B.sc., PH.D. (March, 1911.) 1s. Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Wrturam Brown, B.so. (April 15, 1911). 1s. A Thermo-Electric Methed of Cryoscopy. By Henry H. Drxon, sc.p., F.R.s. (April 20, 1911). Is. A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wittram J. Lyons, B.a., a.R.c.sc. (Lonp.). (May 16,1911). 6d. 6. Radiant Matter. By Joun Jony, sc.p., r.x.s. (June 9,1911.) 1s. 10. ail. 12. 13. 14. 15. 16. The Inheritance of Milk-Yield in Cattle. By James Wiuson, m.a., B.SC. (June 12, 1911.) 1s. . Is Archeopteris a Pteridosperm? By T. Jounson, p.sc., F.u.s. (Plates IV.-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, aud of other Species of Archzopteris in Ireland. By T. Jouvson, D.sc., ¥.u.s. (Plates VII., VIII.) (June 28, 1911.) Is. Award of the Boyle Medal to Proressor Joan Jony, M.a., Sc.D., F.R.S. - (July, 1911.) 64d. On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Joun Jouy, sc.p., F.x.s., and Louis B. Smyru, B.a. (Plate IX.) (August, 1911.) Is. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By EH. A. Newern ARBER, M.A, F.L.S. F.G.s. (January UN) As. : Forbesia cancellata, gen. et sp. nov. (Sphenopteris, sp., Baily.) By T. Jounson, p.sc,, F.u.s. (Plates XIII. and XIV.) (January, 1912. 1s. The Inheritance of the Dun Coat-Colour in Horses. By Jamms Winson, M.A., B.SC. (January, 1912.) 1s. On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zinc, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By James H. Pottox, p.sc. (Plates XV. and XVI.) (February 21, 1912.) 1s. Changes in the Osmotic Pressure of the Sap.of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, sc.p., F.r.s., and W.R. G. Arxins, u.A. (February 21, 1912.) 6d. 17. 18. 19. 20. 21. 22. 23. 24, 25. 26. 27. 28. 29. 30. 31. 32. 33. SCIENTIFIC PROCEEDINGS—continued. Improvements in Equatorial Telescope Mountings. By Sr Howarp Gruss, rps. (Plates XVIL—-XIX.) (March 26, 1912.) Is. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Dixon, so.p., r.z.s., and W, R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 64d. ois Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Heyry H. Dixon, sc.p., F.n.s., and W. R. G. Atkins, m.a., A.1.c. (April 9, 1912.) 6d. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jonnson, p.so., F.u.s. (Plates XX. and XXI.) (April 12, 1912.) 1s. On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part {J.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By James H. Portor, D.Sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s. The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Copper, and Lithium. By Grnrvirve V. Morrow, A.R.C.Sc.1. (Plate XXIV.) (May 11, 1912.) Is. Award of the Boyle Medal to Sim Howarp Gruss, F.r.s., April 16, 1912. (May 18, 1912.) 6d. Notes on Dischidia rafflesiana, Watu., anv Dischidia nummularia, Br. By A. F. G. Kerr, m.p. (Plates XXV.-XXXI.) (September 30, 1912.) 2s. Recherches Expérimentales sur la Densité des Liquides en dessous de 0°. Par Jean Timmermans. (October 18, 1912.) 3s. Steady and Turbulent Motion in Gases. By Jeuy J. Dowsine, ua. (Plates XXXII. and XXXIII.) (November 16,1912.) 1s. 6d. Unsound Mendelian Developments, especially as regards the Presence and Absence Theory. By James Witson, m.a., B.Sc. (December 18, 1912.) 1s. 6d. Osmotic Pressures in Plants. I.—Methods of Extracting Sap from Plant Organs. By Hryry H. Drxoy, sc.d., F.R.s., and W. R. G. Arxins, M.a., A.1.C. (February 8, 1913.) 1s. Osmotic Pressures in Plants. II.—Cryoscopic and Conductivity Measurements on some Vegetable Saps. By Henry H. Drxon, sc.p., r.n.s., and W. R. G. Arxins, M.A., Arc. (February 8, 1913.) 6d. A Method of Microscopic Measurement. By J. Joty, sc.p., r.z.s. (February 7, 1913.) 6d. The Melting-Points of some of the Rarer Minerals. By Arnorp L. Funrcunr, M.A., BE. (February 15, 1918.) Is. A Refined Method of obtaining Sublimates. By Arnotp L. Firrcuer, ™.a., pe. (February 17,1913.) 6d. On the Germination of the Seeds of some Dicotyledons. By J. Apams, ma. (Cantab.). (Plate XXXIV.) (February 21,1918.) 1s. 6d. DUBLIN: PRINTKD AT THE UNIVERSULY PRESS KY PONSONKY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (W.8.), No. 34. MARCH, 1913. ON BOTHRODENDRON (CYCLOSTIGIMA) KILTORKENSE, Haughton, sp. BY T. JOHNSON, D.Sc., F.LS., PROFESSOR OF BOTANY IN THE ROYAL COLLEGE OF SCIENCE FOR IRELAND. (PLATES XXXV.—XLI.) [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price Two Shillings. Roval Bublin Society. FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Jlustrations in a complete form, and ready for transmission of the [Wditor. _ Avams— On the Germination of the Seeds of some Dicotyledons. 499 VITACER. Vitis vinifera Linn.—Twenty-five seeds (1911) planted on 2nd April, 1912. On 25th July, 1912, fourteen had germinated, and had formed several leaves. Cotyledons petiolate, blade ovate, entire, pointed, glabrous, five- veined. Petiole 3-8 mm. long, blade 20-24 mm. by 11-17 mm. EXPLANATION OF THE FIGURES. The cotyledons only are shown, and they have not been drawn to any particular scale. species :— _ . Cynoglossum officinale. . Lycopsis arvensis. . Lonicera Periclymenum. . Lychnis dioica. . Spergularia rubra. 5a. Transverse section of same. 6. Atriplex laciniata. 7. Salicornia europea. 7a. Transverse section of same. 8. Sueeda maritima. . Carlina vulgaris. . Centaurea Scabiosa. . Chrysanthemum Leucanthe- mum. Or BR Oo bo . Cnicus arvensis. . Hypocheris glabra. . Lapsana communis. . Leontodon nudicaulis. . Senecio sylvaticus. . Sonchus oleraceus. . Tragopogon pratensis. . Alliaria officinalis. S . Brassica arvensis. rary . Scabiosa succisa. . Gentiana Amarella. . Erodium cicutarium. He OS bo . Geranium pyrenaicum. . Geranium Robertianum. . Lamium amplexicaule. Do hw WH Ww bw bv bo OD Or The actual dimensions are given in the description of each . Cytisus scoparius. . Lotus corniculatus. . Ononis repens. 30. Malva sylvestris. 49 SOIENT. PROC. R.D.S,, VOL. XII., NO. XXXIII. 31. Epilobium montanum. . Corydalis claviculata. 3, Statice maritima. . Polygala vulgaris. . Polygonum lapathifolium. }. Primula veris. . Rhamuus catharticus. . Argrimonia EHupatoria. 39. . Rubus fruticosus. . Bartsia Odontites. 42. . Euphrasia officinalis. Geum urbanum. Digitalis purpurea. . Melampyrum pratense. . Rhinanthus Crista-Galli. . Veronica montana. . Ulmus glabra. . Adthusa Cynapium. . Anthriscus sylvestris. . Conium maculatum. . Caucalis nodosa. . Valerianella dentata. . Viola canina. . Viola hirta. 4m f 500 ] XXXIV. ON BOTHRODENDRON (CYCLOSTIGMA) KILTCRKENSE, Haughton sp. By IT. JOHNSON, D.Sc, F.LS., Professor of Botany in the Royal College of Science for Ireland. (Pirates XXXV.-XLI.) [Read Decemper 17, 1912. Published Marcu 20, 1913.] In the course of a revision of the fossil plants present in the Botanical Division in the National Museum, Dublin, I have had an opportunity of noting the gaps in our knowledge of those land-plants which, at any rate in Britain, are the earliest of which, we have any definite botanical idea. I refer to the well-known Upper Devonian beds of Kiltorcan Hill, Co. Kilkenny, where, in 1851, the officers of the Geological Survey brought to light deposits of fossil plants and animals, which have made the name of Kiltorcan well known in paleontological circles. The Department of Agriculture and Technical Instruction for Ireland authorized me some years ago to make a further exploration of these beds. It was not until July of this year (1912) that I was able to spend a week with a collector and two quarrymen in excavating some tons of rock, and in examining closely on both sides each slab as removed. So rich are the rocks that it was, as the quarryman’ Davis said (as we examined and split open the slabs, showing what the local people called ‘the drawings on the stone’), ‘like turning over the leaves of a picture-book.”’ It is worthy of note that not a single fresh-water mussel-shell Anodonta Jukesit was seen, and only a few isolated fish-scales.” Fragments of foliage 1 Road-mending is the fate of the quarry, unless steps are taken to preserve it asa ‘‘ Nature- monument.’’ * The following note taken from ‘‘ Nature’’ (24th October, 1912, p. 227) deserves quotation here :— ‘Much interest was aroused last March by the discovery of typical Upper Old Red Sandstone, with fish-remains, beneath the neighbourhood of London. Mr. E. Proctor, of the Imperial College of Science, exhibited to the Geological Society characteristic fragments of Holoptychius and Bothriolepis, which he had obtained from a depth of between 1100 and 1200 feet in a boring at Southall. He has lately presented these specimens to the British Museum (Natural History), where they are now to be seen among the fossil fishes.’’ Jounson— On Bothrodendron ( Cyclostigma) kiltorkense. 501 of Sphenopteris Hookeri occurred. ‘The most important find was the stem of Archeopteris (1), previously known only by its isolated sterile and fertile fronds. he object of the present paper is to present, in as complete a form as impressions will allow, an account of the ancient club-moss Bothrodendron (Cyclostigma) hiltorkense, Haught. sp. (2). I shall first give an account of what has been learned of this species since its unearthing in 1851, and then of the additions to our knowledge of it as revealed by an examination of the specimens in the Dublin Museum and elsewhere, and of the collections made last summer. At the outset I should like to acknowledge my indebtedness to Professor Cole, Director of the Geological Survey of Ireland, Professor Joly, F.R.s., Professor of Geology, Trinity College, Dublin, Dr. Smith Woodward, rF.r.s., British Museum (Natural History), and to Sir A. Geikie, ¥.r.s., Director of the Geological Survey of Great Britain, for the ready facilities 1 have received in examining the Kiltorcan specimens in the collections under their respective charges. There was such a difference of opinion amongst the early Victorian palzontologists as to the age of the beds in which the fossil plants of Kiltorcan and other parts of Ireland were found that it was decided to send a set of numbered specimens with drawings to M. Brongniart of Paris as a recognized authority. The specimens were sent in December, 1856; the reply was received by Dr. (later Sir) R. Griffith, of the Geological Survey, in February, ‘1857, and read before both the Royal Geological Society of Treland (3) and the Royal Dublin Society (4). A duplicate numbered set of specimens was retained in Dublin, and the remains of this set, with the numbers still attached in some cases, are now preserved under my charge in the Botanical Division of the National Museum, Dublin. M. Brongniart’s views are of particular interest in their bearing on Bothrodendron. He wrote at length on three specimens—3, 15, 19-—which I can readily recognize from his excellent descriptions were Bothrodendron. He knew, he wrote, nothing like this fossil, and did not venture to name even a family for its reception. Further study of more material of it was necessary—a remark Brongniart repeats of other specimens. He could not on the material sent decide the age of the beds. The plants were, he concluded, specifically distinct from, but generically like those of, the Carboniferous beds, thus agreeing with the few Devonian plants then known. There is no record of any further interchange of views or despatch of specimens, but two years later, in 1859, Dr. Haughton pubiished an illustrated account (2) of certain Kiltorcan club-moss specimens. He assigned them to a new genus Cyclostigma with three species—C. kiltorkense, C. minutum, and C. Griffithit. The genus was founded on the presence of alternating whorls of distant leaf- 4n2 502 Scientific Proceedings, Royal Dublin Society. sears, in each of which a central bundle scar was observed—features which Brongniart, in his descriptive letter, had already noted. The three species named are in reality, it is now generally agreed, parts of one and the same species Bothrodendron (Cyclostigma) kiltorkense. Brongniart had, in his published report, proposed the name without description of Lepidodendron Griffithi for one Kiltorcan specimen. This specimen, whose existence has been questioned (5), is fortunately preserved with its original label and number—14—in the Botanical Division, National Museum, Dublin, and is simply the terminal forking leafy shoot of B. kiltorkense (Plate XXXV, fig. 1). The illustrations accompanying Haughton’s paper as drawn do not give in detail the characters of tho leaf-scars. Examination of the drawings shows that his artist made a rough sketch of the general surface-markings of the stem, and superadded the sketches of the leaf-scars without indicating the central leaf-bundle scar which Brongniart and Haughton mention in their descriptive accounts. This explanation is necessary to prevent fellow- workers, when making their deductions, from attaching too much importance to the drawings of the now unascertainable type specimens of B. hiltorkense (5). (See, e.g., O. Heer, Foss. Flora d. Baren-Insel, p. 43.) An interesting feature in this connection is the fact that Haughton had already, in 1858, figured B. kiltorkense, and recorded it from eight different localities of Ireland, but not from Kiltorcan itself,” as Sigil/aria dichotoma (6). The leaf-scars are drawn without the—at this time—unobserved bundle-scar. One specimen so named is preserved in the Geological Survey Museum in Jermyn Street, where this summer Dr. G. L. Kitchin, the curator, and Mr, Allen gave me every facility for the examination of the Museum’s abundant Kiltorcan material, some of which was actually collected by Edward Forbes himself, and the Survey’s fossil collector, Gibbs. The specimen in question shows on one side scraps of stems with typical Bothrodendron leaf-scars. On the other side of the slab there is a large but poorly preserved impression of a fluted stem, with here and there Ulodendroid suggestions. The earliest illustration of Bothrodendron I have been able to find occurs in Rhode’s “ Beitrage zur Pflanzenkunde der Vorwelt,” a work published in 1820, and containing an illustrated account of the fossil plants of Silesia (7). ‘The names C. Grifithii and L. Grifithii had no known connection with one another when first given. ‘They are now known to be synonyms for B. hiltorkense. * C. minutum had already, Haughton mentioned, been figured in Lyell’s Manual (5th ed., p. 418), and in the Journal of the Geol. Soc., Dublin (vol. vi, p. 285), as Lepidodendron minutum. Jounson— On Bothrodendron ( Cyclostigma) hiltorkense. 508 Rhode’s drawing shows (op. cit., pl. v, figs. 4 and 5) a large piece of flattened stem, with the leaf-scars indicated in one part, and in another, where the carbonaceous incrustation has disappeared, the deeper-seated Knorria-stage. The illustration is more correct than the interpretation of it. Rhode shows the parichnos streaks, but describes them as the impressions made by the linear leaves themselves pressed against the stem surface. Rhode’s publication is noteworthy in that not a single fossil he describes in it isnamed. Bothrodendron is a “‘schuppenartige Pflanze.” J. B. Jukes, tho Director of the Geological Survey of Ireland, had also had Bothrodendron before him, and in 1855 made a sketch of an exposed bed of plants in the Old Red Sandstone in a quarry at Tallowbridge near Waterford. This sketch appears (as fig. 3, p. 17) in the Explanations to Sheets 176 and 177 (1861) of the Geological Survey of Ireland, and shows clearly that his “large linear plants” (5 feet long, and 4 to 5 inches wide) were really Bothrodendron (8). Fie. 1.—Piece of stem of Lycopodites pinastroides showing leaf-scars. (Copy.) In the course of his reply Brongniart suggested comparison of the Kiltorcan plants with those from the beds of Saalfeld in Thiringen, since they were regarded as Devonian. Richter and Unger had, he stated at the time he wrote, given a list only of those plants, accompanied by the statement that they were nearly all new to science. It is interesting now to read the detailed illustrated account which appeared in the Transactions of the Vienna Academy of Sciences in 1856 (9). Unger was responsible for the botanical part of the report on the Saalfeld discoveries. Richter collected the specimens, drew them, and sent his drawings to Unger, who drew his descriptions and conclusions from Richter’s drawings without, in many cases, ever seeing the original specimens. One plant so described is called Lycopodites pinastroides, R. and U., text-figure 1 (op. cit., pl. x, fig. 9). As ‘The name Lepidodendron owes its origin to a similar mistake. 504 Scientific Proceedings, Royal Dublin Society. the reproduction of Unger’s figure shows, the specimen is a small piece of a stem, with slightly projecting distant leaf-scars alternating with one another, and forming spirally ascending ‘whorls’ or parastichies. I was much struck by the similarity of the figure to the appearance presented by a young stem of Bothrodendron kiltorkense, as I had seen it in Irish specimens, and also in a specimen from Bear Island I owe to the kindness of Professor Nathorst. This similarity is strikingly indicated in Nathorst’s own figure (pl. xl, fig. 10) of such a stem, text-figure 2. The likeness is not lessened by comparison of the enlarged leaf-scars. Tio me it seemed that Lycopodites pinastroides, R. and U., was in reality a twig of Bothrodendron, and that Brongniart was justified when he suggested the Saalfeld beds' might throw Fia. 2.—Piece of stem of Bothrodendron kiltorkense from Bear Island, for comparison with text-figure 1. (After Nathorst.) light on the Kiltorean ones. ‘The Saalfeld material has been recently re- investigated by Count Solms-Laubach (11) under difficulties which he graphically describes. Solms-Laubach leaves L. pinastroides, except for an added query, as he finds it, saying that though he had the advantage of examining the type-specimen preserved in Berlin, he could not express any definite opinion on its characters or affinities. I cannot but think that an examination of a series of specimens of Bothrodendron would satisfy him of the identity of the two. I feel convinced that L. pinastroides is a fragment of Bothrodendron; and I am encouraged in this view by the fact that B. minutifolium was once described and figured as Lycopodites selaginoides 1 Zimmermann (Potonié: Die Silur-Flora, p. 168) places the Saalfeld deposits in the Lower Culm formation. Jounson— On Bothrodendron ( Cyclostigma) kiltorkense. 505 Roehl (in 1869), and later as Lycopodites lycopodioides, Feistmantel. That Solms-Laubach did not at one time attach the importance to Bothrodendron it deserves is evident from the following abstract from his pioneer work— Introduction to Palesophytology (12) (p. 293) :— “Other remains resembling Stigmaria from the Devonian formation have been described under the names Cyclostigma, Bothrodendron, and Arthrostigma, but they are only known in impressions, and are therefore of small importance to the botanist . . . Heer, who had specimens from Bear Island before him, declares that Haughton’s figures are bad [Brongniart called them beautiful], and figures a quincuncial position of the scars exactly like that of Stigmarie; and this is found in an Ivish specimen which I saw in the Museum at Breslau. . .” W. H. Baily had, in his reports (13) to the British Association (Norwich Meeting, 1868; Hxeter Meeting, 1869), called attention to the discovery at Kaltorean of forms which he identified with Sagenaria Veltheimiana as distinct from Haughton’s Cyclostigma. In 1873, in a paper entitled “ Additional Notes on the Fossil Flora of Ireland,’ he partly corrected (14) this wrong identification, and stated that Schimper had in 1870-72 (15) named the specimens he sent him from Kiltorcan Knorria Batlyana. Schimper includes under this name “? Cyclostigma minuta, Haughton” (Nat. Hist. Review, vol. vii, 1859, p. 209), and “ Knorria Veltheimiana, Baily MS., and Mem. of Geol. Survey, Ireland, 1864, p. 22.” Baily, who was the Irish Geological Survey’s Paleontologist for many years, published the best connected account of his Kiltorcan Club-moss in the Journal of the Royal Geological Society of Ireland (14) (vol. iii, new series ; vol. xiii, 1870-73), in which, on plate vi, he gives a series of figures indicative of an attempt at restoration. Baily accepts Schimper’s name of Knorria Bailyana, and states his objections to the opinion of Carruthers that Haughton’s genus Cyclostigma! was founded (as Haughton himself, it is curious to learn, admitted to Carruthers) on insufficient evidence. Carruthers, who held the view that the Kiltorean deposits were Devonian, considered that the material did not show the three recorded genera Lepido- dendron, Cyclostigma, and Knorria with four species, but one genus only and one species—Lepidodendron Grifithii of Brongniart, which was really of the nature of a nomen nudum. My own conclusions are in agreement with Carruthers, viz. that there is only one genus with one species of Club-moss represented, though it is not, as he thought, a Lepidodendron. 1 The name Cyclostigma had, as appears from the Index Kewensis, been already used several times before Haughton’s application of it :—in 1842 for one of the Aponacez ; in 1853 for Croton, and, as Potonié points out (in 1839), for a section of the genus Gentiana. 506 Scientific Proceedings, Royal Dublin Society. . The Kiltorcan beds had aroused increased interest owing to the startling discovery of O. Heer, made in 1870 from the examination of material gathered in 1868, that certain fossil-beds in Bear Island (74°N.) were contemporaneous with the Kiltorcan beds, and contained plants and animals identical! with them. Heer concluded, erroneously, that the beds in both localities represented a stage which he called the Ursa stage, intercalated between the Devonian and the Lower Carboniferous. His contribution to the subject is mainly valuable for the evidence he produces in support of his now accepted views of the contemporaneity and similarity of flora (and fauna) of the beds of these two (and other) widely separated localities. He adds little or nothing to the knowledge of the structure of the fossil plants themselves. Much of his subject-matter underwent a much-needed revision at the hands of Nathorst in 1894, and still more in 1902. In 1886 Kidston pointed out for the first time (16) that the leaf-scars of Bothrodendron kiltorkense showed the three scars which are typical of a Lepidophyte. This observation was confirmed by Nathorst in material from Kiltorcan and from Bear Island; and I have frequently seen the three scars Fig. 3. Fig.'4. Fic. 3.—Fully formed leaf-scar of Bothrodendron kiltorkense, showing the usual lepidophyte characters. Fie. 4.—Leaf-scar on young stem of Bothrodendron kiltorkense. in Irish specimens (Plate XX XVII, fig. 4). B. hiltorkense differs from other Lepidophytes, and even from other species of Bothrodendron (e.g., B. puncta- tum, B. minutifolium, B. wickianum) in the obscurity or almost general absence of indications of a ligular scar. I have spent considerable time in examining many specimens, and in the majority of cases have seen nothing that could be described as clearly indicative of the ligular scars. In some cases, and particularly in one well-preserved specimen in the Geological Museum of Trinity College, Dublin, I have seen leaf-scars as figured (figs. 3 and 4). It seems justifiable to regard the scar indicated as the ligular scar. Generally speaking, however, the leaf-scar is not accompanied by any reliable sign of the presence of a ligular scar; and it is possible that B. hiltorkense, unlike B. mundum, is eligulate like Lycopodium. Many of the specimens of Kiltorcan are beautifully preserved. The plants grew perhaps where they 1 Heer states that Geinitz first called his attention to the identity of the Bothrodendrons of Kiltorcan and Bear Island. Jounson—On Bothrodendron (Cyclostigma) kiltorkense. 507 are now found fossilized (autochtonous)! and did not suffer damage, as specimens carried long distances would (allochtonous). Stratigraphical. Special interest attaches to the important paper on Bothrodendron written by Potonié in 1901 (17), partly because this writer’s views, if accepted, would minimize the value of the superabundance of Bothrodendron remains as con- elusive evidence of the Devonian age of the beds containing them, and partly because the species described at length by Potonié—Cyclostigma hercynium, Weiss—shows a striking parallelism in most of its features, as far as they are known,’ to Bothrodendron hiltorkense. Oyclostigma hereynium occurs in the Tanner Grauwacke of the Harz Mountains. These are strata which are regarded by German geologists as Silurian. In the course of his description of the specimens of C. kiltorkense from Bear Island, Heer points out the closeness of affinity of Roemer’s specimen of Sagenaria, from the Harz beds of Lautenberg, to C. hiltorkense. These same specimens are now included by Potonié in the species C. hercynium, Weiss, so closely allied to, if not identical with, C. kiltorkense. As Heer placed C. kiltorkense in the Ursa stage above the Devonian beds, he would hardly have been prepared to admit that Roemer’s Sagenaria (C. hercyniwm, Weiss) was Silurian. The recent work of Dr. Marie Stopes (18) shows that the Gaspé beds in Eastern Canada, yielding C. densifolium, &c.,° and assigned by Dawson (19) to the Silurian epoch, are, as long suspected, in reality Devonian. It is difficult to accept the view that the Bothodendron flora, which in all those other parts of the world where it occurs predominantly is a typical Devonian, one should be in the Harz Mountains a Silurian one. In no other part of the world do Silurian rocks, recognized as such, yield Bothrodendron remains. The difficulty is not lessened by the fact that the beds grouped as Devonian in the Harz Mountains are almost devoid of plant-remains. The meagre scraps—several of which are figured by Potonié and are Bothrodendron-like—are mostly too poorly preserved for recognition. Hyen in the Mid-Devonian Flora of Bohemia (Barande’s Silurian H-h) there are no distinct Bothrodendron forms, though certain young Lepidophyte shoots probably belong to Bothro- dendron. There seems no objection, for the present, however, to follow Potonié for correlation purposes, in grouping all the fossil plants found in the Silurian and Devonian rocks together as Pre-Culmian, so little do true t As used by Potonié. 2 C. hercynium, Weiss, is still known only in the stage with one central scar (leaf-bundle scar in the leaf-scar. 3 C. densifolium, Daws. has been described as a badly preserved specimen of B. hiltorkense. SCIENT. PROC. R.D.S., VOL. XIII., NO. XXXIV. 4P ‘ 508 Scientific Proceedings, Royal Dublin Society. Silurian land-plants of ascertainable characters normally enter into the earliest flora. It is not inconceivable that the Devonian beds are pre-eminently rich in Bothrodendron, because this genus has in them reached its maximum development, having begun in the earlier Silurian epoch. It is known to be waningly represented by several species in the Middle, and by only one species—B. sparsifolium—in the Upper Coal Measures. Calamitoid Characters. There is one interesting feature observable in the impressions of older stems, especially of Bothrodendron kiltorkense, which deserves more than passing notice. This feature is illustrated in the photographs (Plate XXX VIII, figs. 1-4). Fig. 2 represents a piece of stem 80 em. long and 10 cm. broad, which, at first glance, might be mistaken for a Calamite. It is not simply that the surface of the stem possesses a longitudinally striate epidermis; the stem is strongly fluted or grooved (fig. 3), revealing a marked structural feature. In some small pieces of stem (Plate XX XV, figs. 4 and 5) evidently stripped of the cortex the ridging is so pronounced and Equisetaceous that I felt sure, until I noticed the distant lcaf-scars in the Knorria-stage, that the specimens were part of the Calamite. Heevr’s figure (‘I'f. x, fig. 8: Flora d. Baren-Insel) of the young stem of his Calamites radiatus is evidently made from a specimen in the same stage and state as this Kiltorcan material. The illustration (Plate XXXVIII, fig. 3), which represents a small piece of Plate XX XVIII, fig. 2 enlarged, shows, in addition to the continuous straight vertical grooving, a transverse zonation which corresponds in position with the leaf-scars when these occur in horizontal whorls, and suggests the presence of nodal diaphragms (Plate XX XVIII, fig. 5). The magnification of the fluted surface shows that the leaf-scars occur independently of the vertical ridges, sometimes on the ridges, at other places in the grooves between them. The fluting is observable in flattened stems 12 inches wide, with typical leaf-scars still clearly recogniz- able on the epidermal surface of the stem—a sign apparently, as in Lepido- dendron, of absence of periderm, owing to the adaptation of the epidermis to the increase in girth of the stem. It is to be seen, too, along with transverse zonation in comparatively young stems, 1 em. wide, apparently in certain conditions of preservation, e.g. in the stem figured (Plate XXXYV, fig. 3) in which the leaf-scars are still close together. A striking difference is observable in this stem in the arrangement of the leaf-scars. Those on the right-hand side are arranged in a zone-like manner; and this part of the stem is transversely ridged or zoned. On the left-hand side the leaf-scars are less zonately arranged, wider apart, and appear to be assuming the quin- cuncial position. Running down the centre of the impression is a faint Jounson—On Bothrodendron ( Cyclostigma) kiltorkense. 509 ridge suggestive of a central vascular axis in the living stem. (One would naturally assume from comparison with other Lepidophytes that the stem of B. kiltorkense would possess a central vascular axis—a protostele at least. Rhode and Haughton speak of such an axis, and roughly indicate it in their drawings. In several pieces of stems the broken end shows traces of carbonized remains in the hollow cylinder, though in one of the best-preserved pieces (Plate XLI, fig. 2) there is no sign of such an axial strand. The stem appears in this section as hollow as an internode of Equisetum. The fact that the Bothrodendron stems are found nearly always in a flattened state (sometimes like sheets of paper) lends support to the view that the stem was hollow or occupied by soft perishable tissue. It is possible that the specimen (Plate XX XV, fig. 3) illustrates a difference of illumination of the two sides of the stem. ‘The photograph shows clearly that the difference occurs, whatever the physiological cause may be. ‘This specimen should be compared with the older one (Plate XX XV, fig. 2), which shows closely approximated leaf-scars in the upper part and separating ones in the lower thicker part of the stem- impression—a clear illustration of the increasing distance between the scars, which accompanies and is caused by the extension of the surface as the stem enlarges. It was failure to recognize the ribbed stem as found in Bothrodendron which led Heer to place such specimens in his Calamites radiatus, now known as Aszerocalamites scrobiculatus, and in part as Psewdobornia ursind, Nath. Potonié devotes some attention to the description and explana- tion of calamitoid characters in his Cyclostigma hercynium. These characters are very like those in Bothrodendron hiltorkense, but by no means so pronounced ; and Potonié expressly mentions, apparently to avoid the possibility of con- fusion with the Equisetaces, that naturally in it horizontal zonation does not occur. ‘he photographs show that it does occur in B. kiltorkense. The figures give a good idea of the general character of the ribbed features, and show, too, that Potonié’s explanation is not sufficient to account for the appearance. Plate XX XVIII, fig. 2, shows that the ribbed feature is not confined to the Knorria-stage, as Potonié supposes, but is clearly marked in stems with cortex and epidermis preserved. In the specimen the finer sculpturing of the stem is evident, and the leaf-scars showing the typical condition with three scars are readily observable. Potonié states—and I agree with him—that in the Knorria-stage the petrified parichnos-strand of the leaf rests in contact with that of the leaf immediately above or below it, and that thus more or less straight ridges arise. The strand in some cases is not equally prominent throughout its length, and in consequence the ribs, though straight, may not be so regular or continuous as those of a Calamite, especially of an Asterocalumite, in which the vertical ridges coincide from internode to 4r2 510 Scientific Proceedings, Royal Dublin Society. internode. It appears from the Kiltorcan material as if there must also be present internal sclerotic bands or stereom-lamelle, possibly in connection with the vascular bundle and parichnos-strands, and possibly capable of being added to as the plant ages, because the ribbing is often more pronounced in older stems in which the leaf-scars are still clearly recognizable. I have seen it very well developed in steths 12 inches in diameter, and 7 or 8 feet long. In the specimen figured the ribs are 3°3 mm. in width. The apparent absence of a pronounced cylinder of secondary wood may be correlated with the marked deciduous character of the foliage. Though conducting tissue may not be much required, strengthening bands of sclerotic tissue would be for a stem 20-25 feet long, 10-12 inches wide, and much branched. The ribs in B. kiltorkense might arise, like the zone of prosenchymatous tissue in Lepidodendron, as the plant aged, from formative tissue in the cortex. Potonié regards the calamitoid condition as indicative of a special state of preservation of the Knorria-stage. I go further than this, and regard the ribbed and zoned condition as a natural feature of the Bothrodendron stem. It is possible that the fluting of the stem in Bothrodendron, with its early deciduous leaves, is a physiological adaptation comparable to that found in a recent EKquisetum, with its inconspicuous leaf-sheaths, where the stem by its adaptation of structure functionally replaces, to a large extent, the leaves. One can picture a Bothrodendron in its swampy habitat, with its terminal tufts of long subulate leaves, and grooved, dull-green, pseudo-jointed stems suggestive of our much smaller Hguwisetwm sylvaticum in its boggy mountain glen. The marked intervals between the leaf-scars in the older stem is, it is generally agreed, explicable by the extension of the stem-surface in the enlarging shoot. The younger stems show the leaf-scars in close contact before expansion begins; and this closeness of the scars is illustrated in the modern Lycopodium throughout its thin stem. ‘hus we seem to have a modern representative (Lycopodium) of an ancient group, throughout its life in the condition passed through in its early stages by one of the most ancient members of the group (Bothrodendron). Just as in metabolism there is marked reversibility of physiological processes, so here we apparently have reversibility of evolution. The most recent member of the group represents in its permanency a stage passed through in its ontogeny by one of the earliest members ; thus the phylogeny of the Lepidophytes is not recapitulated in the ontogeny of its latest representative. The group has now retrograded to its earliest type; the intervening stages have been tried, found wanting, and now lie buried in the rocks. Bothrodendron itself dies out in the Upper Carboniferous. ‘Thus in an undoubted Lepidophyte we have those clearly Jounson—On Bothrodendron ( Cyclostigma) kiltorkense. 511 marked external features, as the photograph shows, which are usually associated with a Calamite. Although the Sphenophyllales and Pseudoborniales are found in the Devonian rocks, the genus Asterocalamites, the earliest of the Equisetaceze or Calamarie, the other group of the Articulate, is not found, according to Potonié, in rocks (records notwithstanding) earlier than the Culm or lowest Carboniferous. Bothrodendron is the earliest of the Lepidophytes, and in its calamitoid characters brings us nearer to the ancestral group of Pteridophytes common to the Lepidophyta and Articulate, to a group suggested by Scott (20) in the course of his description of the complex cone of Cheirostrobus. Nathorst, writing in 1894 (and in 1902, op. cit., p. 33), regrets that neither the modes of branching, the cones, leaves, nor roots of such an important genus as Bothrodendron are known, since it is from it perhaps that Lepidcdendron and Sigillaria are derived, he states. Knorria Stage. One of the most important features of Potonié’s account of C. hereynium is the description and identification of the numerous Knorria species of eariier publications as states of preservation of C. hercynium. Knorriais a decorticated stem showing the petrified parichnos-strand of various forms indicated by the specific names employed. In the strand towards its upper end there may be often found a groove or slit representing the leaf-bundle scar surrounded by the parichnos-strand. This is well seen in Knorria acicularis. In this connection the Kiltorcan stem figured (Plate XLI, figs. 1 and 2) is of interest. It is clearly in the Knorria acicularis stage. The epidermis and cortex have disappeared, and the more or less fusiform petrified parichnos-strand is evident, with the characteristic slit-like bundle-scar enclosed at the upper end. (Compare Potoniée’s fig. 28, p. 63: Die Silur-Flora.) The comparison strengthens the impression that 0. hercyniwm differs little, as far as known, if at all, from B. kiltorkense. Even the Knorria Selloi stage (Potonié, fig. 20, p. 45) of C. hercynium occurs in Kiltorcan material (Plate XX XVIII, fig. 3). As Knorria stages are in some deposits the only ones found, their strati- graphical value is naturally increased by their correct identification with known species of recognized genera. It is the more necessary to mention them here, as Heer emphasizes the absence of a Knorria stage in Cyclostigma as a feature of distinction of this genus from Lepidodendron. There are several Knorria specimens of Bothrodendron kiltorkense from Co. Cork in the Collections of the Geological Survey of Ireland. One of these (“ Knorria: Carboniferous Slate, Cork, west of Shehybeg Mountain’’) is a petrification showing a typical Knoriia Selloi stage. The parichnos-strands are broad and truncate. Another specimen (4974, from the Old Red Sand- . 512 Scientific Proceedings, Royal Dublin Society. stone, Tracarta, Cork) is labelled K. Bailyana, and shows what may be called the ‘‘ Bergeria”’ stage of B. kiltorkense. The stem, 1 cm. wide, shows both horizontal zonation coinciding with the whorls of leaves and the longitudinal grooving. In this specimen the grooving and ridging are not continuous in the vertical direction. If one’s attention were limited to this case, one would say that the longitudinal ridges are simply the petrified parichnos-strands. Ulodendroid Condition. (Plate XI, fig. 3.) Bothrodendron kiltorkense presents many illustrations of the puzzling structures—circular or elliptical depressions on the stem—regarded when first seen as distinctive of a genus, Ulodendron, but now recognized as a feature found in many Lepidophytes. The Ulodendron scar is well known in B. punctatum, with which the small cone of B. mundum, as described by Watson (21), has been associated. In Lepidodendron, Sigillaria, and B. punctatum the scars occur in two opposite rows, often in the form of deep pits with an excentrie umbilicus. In B. kiltorkense they show no such regularity of arrangement (I have seen one case only of two such scars in a vertical row), being moreover generally so inconspicuous as to have been hitherto overlooked. Heer expressly states that Bothrodendron hiltorkense does not show Ulodendron scars. The general surface of this scar is often much the same in appearance as that of the surrounding stem, except for the umbilicus, which is not markedly excentric, and looks like the scar left by the rupture of a vascular strand. The Ulodendroid field, which may be 1:3 cm. wide, is limited by a slight circular or sub-circular depression, and sometimes shows a similar inner concentric marking, i.e. one of smaller diameter. The whole scar suggests that a structure was attached here by a very narrow vascular base, that it was cylindrical in form, and, increasing with age in diameter, pressed with its base against the stem surface. The fact that almost the whole field, except for the point of attachment, may be like that of the surrounding stem-surface supports the view that the Ulodendroid scar in B. kiltorkense represents an appendicular organ with a very narrow point of attachment. There is some danger of being misled in the desire to secure uniformity of interpretation of the cause of the Ulodendroid scar. Just as the view that the scar was characteristic of a particular genus was shown to be untenable, so the idea that all Ulodendroid scars are of the same nature seems un- warranted. Any appendicular organ of importance must leave a scar which will be more pronounced the deeper-seated the origin of the organ. Watson seems to me to give (22) an acceptable explanation of the ordinary Uloden- Jounson—On Bothrodendron ( Cyclostigma) kiltorkense. 513 droid scars he figures when he assigns them to the wounds left by the falling off of a branch. Confirmation of the general correctness of this view was supplied by M. Renier (23), who found, in a split slab of rock, astem of B. punctatum with a Ulodendroid scar on one thus exposed surface, and on the corresponding surface a dichotomously dividing branch whose proximal end fitted exactly into and coincided with the scar on the parent stem. Kidston seems to have misinterpreted (24) inadvertently! this note of Renier as supporting the explanation he and others had offered that the scars represent the points of attachment of cones—an explanation amplified now by the suggestion that the cones were not sessile but seated on a short deciduous axis. I can find nothing in Renier’s account to suggest that he regarded the lateral branching shoot as either deciduous or fertile. Heexpressly states that the branch, after running 10cm. in the rock, bifurcates, and that one branch so formed runs 20cm., and appears to dichotomize again. He further mentions Lepidodendron selaginoides, Carr., and L. Hickii, Wats., as two species in which branches are known to occur in two opposite rows. Menier regards the depth of the depression as a sign of the degree of decay of the soft tissues surrounding the vascular tissue represented by the umbilicus. It would appear as if the severing of the branches, whether natural or artificial, was not accompanied by that healing of the wound which occurs under similar conditions to-day. Bothrodendron as a type would not compete under equal conditions against on-coming plants with wound-healing powers. Though Renier’s explanation may hold good in general for B. kiltorkense too, its scars are so shallow and irregularly placed that it is possible that in some of the older stems they represent the points of attachment of stray Stigmarian appendages. Their area is the same, and the umbilicus is not dissimilar to that on the Stigmarian axis. The slab numbered ‘‘2” in the series sent to M. Brongniart is of special interest. In addition to Archewopteris hibernica, Forbes sp., and the Archeopteris Tschermaki, Stur, I have already recorded, it shows fragments of the stem and groups of megaspores of B. kiltorkense, and also on this stem the curious creeping thread-like bodies which Nathorst, believing them to be possibly epiphytic alge, named, from specimens he saw on the stems of Bothrodendron in Bear Island, Codonophyton epiphyticum. In the Kiltorcan specimen they are generally more or less closely associated with the leaf-scars. Foliage. Although stems of Bothrodendron kiltorkense have been found in fair quantity and in all stages in Ireland and elsewhere, there is no record as yet 1 A reviewer of Renier’s research, in ‘‘ Paleobotanische Zeitschrift ’’ (I. s. 80), throws doubt on Renier’s conclusions owing to the inadequacy of his illustrations. 514 Scientific Proceedings, Royal Dublin Society. of the occurrence of stems with foliage leaves' attached. It is thus evident that the leaves were deciduous at an unusually early age of the shoot. Fortunately the specimen already mentioned, and named by Brongniart Lepidodendron Griffithi, and other specimens (e.g. Plate XX XV, fig. 1) furnish the missing evidence, and show how distinct the foliage of B. kiltorkense is from that of other species, such as B. punctatum and B. minutifodium, in which attached, more or less lanceolate, Lycopodium-like leaves have long been known. The foliage leaf of B. kiltorkense, as Plate XXXVI, fig. 1, shows, occurs singly in horizontal or obliquely ascending whorls of 10-20 members, and forms apical tufts. It is a linear-subulate leaf, 12-15 cm. long, with a single central vascular bundle running throughout its length. It tapers gradually from the point of attachment, where it is 1 mm. wide, to its apex, and shows no specialized basal portion. It is, on the whole, such a leaf as one would expect, judging from the characters of the fertile leaf, and assuming that in such a primitive type of plant the fertile and sterile leaves would differ but little from one another in general form. The fact that B. kiltorkense is one of the earliest of the Lepidophytes seems to indicate that the small lanceolate leaf of B. punctatum, a much later species, is derived from the long narrow leaf of B. hiltorkense, and persists to-day in the genus Lycopodium. A Lepidodendron with leaves a metre long has been recorded (25). If the leaf is a mere appendicular outgrowth of the axis, arising at first as a slight proliferation of it, B. kiltorkense should show, one would expect, a small inconspicuous leaf instead of the pronounced elongated one described. It is worthy of note that the leaves of Cyclostigma hercynium of the Harz Mountains, as shown, have the same shape as those of B. kiltorkense, but are only one-half or one- third of their length. But for this, I should be inclined to agree with Nathorst, who sees nothing to distinguish Potonié’s C. hercynium from B. kiltorkense. It is possible that the leaves of C. hereynium, figured by Potonié, have their free ends buried in the stone (op. cit., p. 39, fig. 16), and in consequence do not show their full length. Stigmaria Stage. One of the commonest Carboniferous fossils is Stigmaria ficoides, now known to be the rhizome or underground stem of Sigillaria and also of Lepidodendron. As Bothrodendron is so closely allied to these two genera, one might naturally expect it to have a more or less similar Stigmaria- stage. Is there any evidence of this? 1 In Kidston’s pithy account of B. kiltorkense (‘ Guide,”’ 1886) leaves are described; whether found attached or not is not stated. Jounson—On Bothrodendron (Cyelostigma) kiltorkense. 515 Potonié (Die Silur-Flora) gives a detailed and well-illustrated account of Dechenia Roemeriana, and concludes (I think justifiably) that Dechenia is a Stigmaria and the underground organ of Cyclostigma hercynium. His figures show the Knorria-stage of the leaf-scars, attributed to Bothrodendron or Cyclostigma, and in the same petrification the characteristic scars of the Stigmaria appendages. Perfect proof of the correctness of his view would be furnished if the Dechenia showed the surface-markings and leaf-scars of Bothrodendron. As at present known the Knorria-stage may, as Nathorst says, equally well belong to another Lepidophyte. Nathorst cannot accept Potonie’s identification of Dechenia with its Stigmaria features as part of Bothrodendron, but sees in a forking specimen he himself figures (op. cit, Tf. 10, figs. 4 and 5) the probable rhizome of Bothrodendron. His figures show a bifurcated axis covered with leaf-scars which occur on cushions slightly raised and directed towards the free ends of the arms. Further, the surface of the whole axis, it is noted, is marked by a slight longitudinal striation. I can see nothing special in the specimen as illustrated to support the view that it is the rhizome of Bothrodendron. Nathorst thinks that Stigmaria is itself so peculiar, if not enigmatical, a morphological organ, that variation in Bothrodendron from the normal seen in other Lepidophytes need not surprise one. Nathorst states that if the forked axis he figures is not rhizomatous, then the majority of the stems figured in various publications are drawn upside down. It is curious to note that Nathorst himself seems to make this possible error. His illustration—Tf. 14, fig. 5—shows a small piece of stem in which the leaf-scars are identical in character with those on the unforked part of his rhizomatus axis, in Tf. 10, fig. 4. My opinion is that the former shows the leaf-scars in the right position, and that his supposed rhizome is simply part of an ordinary aérial dichotomizing shoot. Nathorst’s illustrations of B. kiltorkense are the most ample and satisfactory hitherto published, but in the lithographic ones the leaf-scar illustrations leave something to be desired in definiteness)s My own expe- rience, based on the examination of leaf-bearing and other shoots, is that the leaf-scar, when on a leaf-cushion or not, is limited on its lower side by a more or less well-defined rim or ridge which is continued upwards to complete a round or somewhat oval border beyond which it runs out into a sloping surface (Plate XX XVII, fig. 4). The ligular scars, if admitted as such, may occur where this inclined surface joins the leaf-scar proper, so that the incline may be included as part of the leaf-field or (when projecting) leaf- cushion. In some cases where the impression or cast is not the outer carbonaceous surface of the shoot, but the shoot surface as seen from within, or even its counterpart, impress or “mould,” on the stone, the leaf-scar SCIENT. PROC, R.D.S., VOL. XIIL., NO. XXXIV. 4G 516 Scientific Proceedings, Royal Dublin Society. appears as a depression, and the apical slope is inclined upwards from the upper edge of the depression. This flap-like ledge beyond the upper limit proper of the leaf-scar I have found a very reliable guide in ascertaining which is the upper end of isolated pieces of stem (Plate XXXVII, figs. 2 and 38). The specimen illustrated (Plate XXXVI, fig. 2) from Kiltorcan is strikingly like the one from Bear Island described by Nathorst, and regarded by him as rhizomatous. It is a piece of bifurcating stem in which the dichotomy is not absolute, as the branch seen to the right is thinner, and the left one shows an overtopping tendency. Its more distant leaf-scars are in spiral or oblique whorls, i.e. parastichies, not in horizontal, “alternating ” whorls, as in the left branch. Further, the longitudinal striation observable in the parent stem is continued into the left branch, but is almost absent from the right one. The right-hand branch runs as a core through the stone, so that at its broken end one can see apparent suggestions of a central axial strand of tissue of unrecognizable nature, and also the lower surface (seen from within) of the cortex of the branch. Another argument used by Nathorst against the Stigmarian connate f is the rarity of Stigmaria in the Bear Island deposits compared with the frequency of Bothrodendron remains. Most of the Stigmarias were collected in 1868, when the botanical importance of the beds could not be fully realized by the explorers. Nathorst, in 1898, got one or two specimens only, and Andersson, in 1899, none at all. Now, Nathorst twice mentions that his visit to the Bothrodendron locality was compulsorily short, and that Andersson’s specimens of Bothrodendron were nearly all pieces of young stems. ‘The absence of Stigmaria in the later collections is thus explicable. Stigmaria represents the basal part of a whole plant, and is naturally less frequently met with than the numerous aérial branches. It is worth recalling here that Baily assigns a Stigmaria-stage, in his plan of restoration, to Knorria Bailyana without giving his reasons for the association. In my examination of the Museum material I had seen evidence indicating the organic connection of Stigmaria with Bothrodendron, and kept a look-out for further proof in the quarry work I did at Kiltorcan. I have now several specimens in which the same fossil shows clearly at one end the true Stigmaria scars, and at the other end, in continuous connection with the Stigmaria, a stem impression which shows the usual surface-markings and some scattered leaf-scars of Bothro- dendron. These specimens show that Bothrodendron has a normal under- ground Stigmaria-stage. During the week’s work we got innumerable pieces of stem, but only a few specimens of Stigmaria, and at one particular part of the quarry. In keeping with this, too, we found only one or two Jounson—On Bothrodendron (Cyclostigma) kiltorkense. 517 really large stems close to the Stigmaria specimens. At no time did I find anything suggestive of the presence of Lepidodendron itself in the Kiltorcan deposits; and I have concluded, though negative conclusions are dangerous, from this experience, and from the detailed examination of various collec- tions, that this genus does not occur there. I also look with suspicion on many statements in print to the effect that a Lepidodendron occurs in a Devonian deposit. The young branches of this genus as recorded are, in all probability, Bothrodendron. Did one not know the appearance presented by older stems of Bothrodendron, the young stems would be certainly referred to Lepido- dendron. In this way I explain many records of the occurrence of Lepidodendron in Devonian beds. ‘There can be no doubt of the presence of the genus in cases where specimens show the typical Lepidodendron leaf- cushions—e.g., L. Veltheimit and L. Volkmanianum (Bear Island). It is often worthy of note that in these species the leaf-cushions are small, and sugges- tive of Bothrodendron connection (Donetz Becken). ‘lhe Knorrias recorded are probably often &. acicularis—i.e., Bothrodendron impressions, deprived of the outer cortex, and showing the deeper-seated fusiform parichnos strands. The specimens of Bothrodendron in the Geological Museum in Jermyn Street are of special interest. One specimen (Number 26288), labelled “ Cyclostigma kiltorkense? Roots?” is very instructive. It shows the connecting region between the aérial part of the stem with its leaf-scars and the surface sculpturing of a true Bothrodendron and the subterranean part which is in the Stigmaria condition (Plate XXXIX). Another specimen (Number 26237), in the Museum Stores, labelled “‘ Stigmaria,” shows typical Bothrodendron leaf-scars.: These two specimens are clear confirmation of the conclusion I had arrived at from field-work and from the examination of other specimens, that Bothrodendron bifureates at the base of its stem once or twice to form sub- aerial Stigmaria branches which have their surfaces covered with scars, representative of the points of attachment of the appendages. It is interesting to note in this connection that F. EH. Weiss (26) has recently described a Stigmaria which differs in structure somewhat from that of the common Stigmaria ficoides. It is, too, regarded as probably the subterranean organ of that Bothrodendron mundum whose Selaginella-like strobilus has been described by Watson. It is unfortunate that the Irish beds contain only impressions of Bothrodendron. 1 A drawing of this specimen was made by my son Gerald, a medical student, without assistance, and the leaf—scars drawn were at once recognized by Dr. Kitchin as those of Bothrodendron. 462 518 Scientific Proceedings, Royal Dublin Society. Stigmaria Appendages. As the illustrations show (Plate XL, figs. 4 and 5), the Stigmaria appendages in Bothrodendron are well developed. In the one figured they are, as far as traceable, 24 cm. long and as much as 2 cm. wide. Running through the appendage is a single vascular strand. Unlike Stigmarian appendages generally, which, according to Potonié, very rarely branch, these appendages branch several times, but not apparently dichotomously, and they become more root-like in their finer ramifications. The impressions show the continuity of the axial strands in parent and lateral appendages. The appearance of the appendage suggests a bulky soft tissue surrounding an axial strand, indicative of an organ growing in a swamp. It is of interest to note that the appendage branches show a constricted base of attachment. Though “ Stigmaria” is rare in the Devonian rocks, it is described as one ~ of the commonest fossils in the Carboniferous epoch. Its anatomical structure and that of its appendages have been fully worked out. The text-books by Scott and by Seward give fully illustrated accounts. The ‘Stigmaria ” axis, with its bifureation, is regarded as more comparable to the rhizophore of a Selaginella than to a rhizome. The appendages, though formed, it appears, exogenously, are roots functionally and structurally. The monarch vascular strand is normally central, but becomes excentric owing to the breaking down of the loose lacunar tissue forming the greater part of the bulk of the appendage. Strobilus. The little already known of the cones or strobili of different species of Bothrodendron reveals considerable variety of structure and arrangement, with heterospory, so far as the cones are known, as a character in common. B. mundum as described by Watson shows a diminutive cone. The fertile axis bears a small number of spirally arranged sporophylls, not radially elongated. ach sporophyll carries on its upper side either a spherical megasporangium or a microsporangium, and inserted above this a short evascular ligule. he cone is astonishingly like that of Selaginella. B. minutifolium, on the other hand, possesses a long, narrow, cylindrical, terminal cone with radially elongated sporangia, described by Zeiller as Lepidostrobus Olryi. ‘The statement that B. punctatum possesses short, blunt, lateral cones terminating deciduous shoots arranged in two opposite rows on the older branches, as figured by Kidston in his restoration of the species, needs confirmation in view of Renier’s discoveries that the two rows of Ulodendroid scars are vegetative and not reproductive in origin. Jounson —On Bothrodendron ( Cyclostigma) kiltorkense. 519 B. kiltorkense.—Though absolute proof has been hitherto lacking, it has been generally agreed that the cones described by Schimper from Kiltorcan material sent to him by Baily, as Lepidostrobus, Bailyana, are really the cones of B. kiltorkense. Schimper himself suggested the possibility that the cones of Lepidostrobus were part of Baily’s Knorria. The specimens figured in this paper should remove any remaining doubt. The foliage leaves clearly indicate the closest affinity with the fertile ones. The cone of B. kiltorkense (Plate XLI, fig. 3) is short, terminal, and obconical in shape. Its broad axis carries a large number of whorls of closely crowded sporophylls. It appears from the illustration (Plate XLI, fig. 4) thnt the axis of the cone was either hollow or contained tissue which has disappeared in the course of fossilization. In the space enclosed by the cylindrical axis there is a thin, irregularly shaped, carbonized body. Its nature is not obvious. Fortunately there is a specimen, broken in the stone in such a way as to show part of the cone in longitudinal section. The hollow axis with the peculiarly shaped body in it is again observable, but more interesting is the presence of a carbonized partition stretching across the space from one side to the other of the axis of the cone, and suggesting the presence of a diaphragm and vascular strand. I have already called attention to the hollow cylindrical (crushed) axis of the stem, and suggested that the transverse zonation or ridging seen in certain stems, both young and old, may be due to the presence of nodal diaphragms. It looks as if the cone might also have a hollow axis similarly separated into superposed compartments by diaphragms placed at short intervals from one another with a slender central axial vascular strand, often lost or displaced in course of fossilization, in both kinds of stems. It is worth noting here that a little secondary thickening has been observed in B. mundwm, but nothing of the kind in its vegetative stem or in that of any other Bothrodendron. The numerous impressions in the slabs show the sporophylls from many points of view, and from these a good idea of their general characters can be obtained (Plate XLI, figs. 3-8). ‘The sporophyll, traversed throughout its length by a single vascular bundle attained a length of 20 em. or more, and was differentiated into a thick spatulate or sub-obtriangular fertile base, 16 mm. long, 1-1:5 mm. broad at the point of attachment, and 3-5 mm. at its upper end, and a long, narrow awl-shaped appendage or upper part, 2mm. wide at its point of connection with the distal end of the fertile base. These two parts do not lie in one plane, but are generally set at an angle to one another in such a way that the free end of the sporophyll in the cone was directed out- wards as well as upwards. ‘The fertile base shows a median groove on the 520 Scientific Proceedings, Royal Dublin Society. under or abaxial side, and a pronounced ridge on its upper side, probably fitting into the groove on the under side of the sporophyll immediately above it in the cone. On either side of this ridge there is a line or slight groove (parichnos-continuation ?). Deprived of its fertile proximal end the sporophyll appears similar to an ordinary foliage leaf. It is on the upper or adaxial side of the megasporophyll that the megaspores are borne. They are 1 mm. in diameter and rounded or, as sometimes seen, pyriform bodies. Schimper’s figure of the sporophyll of Z. Batlyana shows numerous megaspores each with a triradiate mark, indicative of an origin by division of the megaspore mother- cell into four spores. As the drawing was made ad naturam, and as it is stated that all the megaspores showed the mark, I must content myself by stating that, though one may safely assume that tetrad divisions took place, Ihave found nothing comparable to Schimper’s figure in the very many sporophylls I have examined. Occasionally the spores have appeared arranged as if with a common origin. ‘They are found more or less in two rows on each side of the midrib, from ten to twenty in number in each sporophyll.. Detached ones are not uncommon in the rock, as well as rounded depressions in the sporophyll, showing their seat of origin. They all show a thick carbonaceous coat—the spore-wall—occasionally seen broken through and revealing an enclosed cavity. The presence of so many megaspores in the one megasporangium in B. kiltorkense is interesting, and adds to the likeness first noted by Schimper of the Kiltorcan sporophyll to that of Isoétes. An additional feature deserves mention. I have frequently noticed at the point of union of the fertile base with the sterile lamina on the upper side a distinct carbonaceous plate, semi- lunar in shape. In some cases the plate is absent, but its extent is indicated by an impression limited by a curved ridge on the sterile part of the sporophyll, above the spore-bearing base. I take this to be the ligule coming, as in Isoétes, between the sporangium and the sterile distal part of the sporophyll. I have attempted in the accompanying figure (text-figure 5, p. 521) a restoration of a female sporophyll (cp. Plate XI, figs. 6, 7,8). I had decided to omit this suggestion of the possible presence of a ligule when I saw that Heer states that every sporophyll of B. kiltorkense appears to have possessed an oval papilla or flap lying between the fertile base and the sterile bristle-like appendage (op. cit., Tf. xi). I give a figure (text-figure 6) of the appearance presented by one mega- spore, and feel emboldened to do so owing to the discovery by R. C. McLean (2'7) of the presence in the megaspore of B. mundum of a prothallus projecting in a manner not unlike that in the germinating megaspore of a Pilularia ora Jounson—On Bothrodendron (Cyclostigma) kiltorkense. 521 ligulate Lycopod. (My drawing was obtained in a way which I have frequently found helpful in the study of fossil plant impressions. A photograph was taken in this instance of the megaspore as magnified several diameters, and projected on to the lantern screen. A piece of drawing paper was placed on the wall-screen; and the picture falling on it was traced, under criticism from several of the more advanced students. The drawing was 21 x 9:5 em.) Fie. 5.—Diagrammatic restoration of megasporophyll of Bothrodendron hiltorkense. Nothing of course of structural value was made out; but the apical body as seen was suggestive of a projecting prothallus. The sketch was made some two years ago, and seems to be an anticipatory confirmation, as far as an impression can be, of McLean’s interesting discovery made from his section of a petrified sprouting megaspore, with a protruding apical prothallus. Fic. 6.—Megaspore of Bothrodendron kiltorkense, apparently germinating and showing projecting gametophyte. Magnified. Incidentally it may be noted that the presence of megaspores, 1 mm. in diameter in the Upper Devonian, strengthens the view that the Pteridosperms lived in the Devonian epoch. 522 Scientific Proceedings, Royal Dublin Society, Hitherto one kind of sporophyll only—the female one—has been identified and described. There is no difficulty in recognizing, especially with a lens, the ripe megasporophyll, as the megaspores stand out well (Plate XLI, fig. 7). Some of the sporophylls, however, both in the cone and when isolated, show a smooth surface in the thick basal part. They are not megasporophylls which have shed their megaspores, as these leave a pit behind. They may be immature megasporophylls or young male or microsporophylls. There are, in addition, sporophylls in which the basal part shows a wrinkled or rugose surface (Plate XLI, fig. 6), whether natural or due to shrinkage I cannot say. Such sporophylls with puckered base suggested themselves as the missing microsporophylls. I played on some of them with the blowpipe, saw them Fia. 7.—Microphotograph of microspore of Bothrodendron hiltorkense. Magnified. Microspore spherical, wall finely punctate, 0:05 mm. in diameter. (Field disfigured by particles of rock.) glow as the carbonaceous matter was burnt, on cooling removed the remainder, crushed it in an agate mortar, and treated it with Schulze’s macerating mixture, followed by ammonia, to remove any ulmic acid present, and then, after heating, examined the resulting material microscopically. Many rounded bodies, some with a triradiate mark, were seen; and I feel justified in concluding that they are the microspores obtained from the micro- sporangium. If my conclusion is justified, the apical strobilus of B. kiltorkense may be described as heterosporous, consisting of an axis carrying whorls of megasporophylls and of microsporophylls. I leave the question of the distri- bution of the sporophylls in the cone an open one at present, being content to record the general agreement, in the possession of a heterosporous cone, of B. kiltorkense with B. mundum and certain other Lepidophytes. Schimper suggested the desirability of a search for the male spores in the Irish material, and Heer speaks of minute black granules he saw in Bear Island material as, in all likelihood, microspores. B. kiltorkense is thus the earliest illustration of heterospory yet known. Distribution. In his “ Fossil Botany ” (vol. ii, p. 257) Seward gives a generalized account of the distribution in time and space of Bothrodendron kiltorkense and of species more or less identical with it. It seems clear from the records that the Jounson—On Bothrodendron ( Cyclostigma) kiltorkense. 528 B. kiltorkense type of Club-moss was prevalent in the Devonian and to a less extent in the Lower Carboniferous epochs wherever there was a land habitat suitable for it in the world. Systematic Position of Bothrodendron. The Bothrodendracee have been regarded as a small group, intermediate between the Lepidodendracez and the Sigillariacesw, while F. H. Weiss placed Bothrodendron under Sigillaria as a subgenus. Kidston, the latest writer on Bothrodendron, sees features in it found partly in Lepidodendron and partly in Sigillaria. He regards it in consequence as a connecting link between these two genera, with additional characters of its own. The records of the rocks show that Bothrodendron is at its maximum development in the Devonian epoch, Lepidodendron in the Lower Coal Measures, Sigillaria in the Middle Coal Measures. In the Pre-Culmian beds, yielding Bothrodendron in Ireland, and in the Harz Mountains and else- where, Lepidodendron is either absent or sparingly represented. McLean also concludes from the examination of the prothallus of B. mundum that Bothrodendron is more primitive than lLepidodendron. The general evidence seems to me to favour the view that Bothrodendron is an earlier type than Lepidodendron, which, with Sigillaria, are types derivable from Bothrodendron, i.e., that Bothrodendron, though heterosporous, is the earliest and most primitive of the Lepidophytes. The young shoots of Bothrodendron are so much like those of Lepidodendron that records based on them, unsupported by stem-impressions showing typical leaf-cushions, are unreliable. Summary. In Bothrodendron kiltorkense the stem attained a length of 8 metres and a breadth of 30 centimetres or more (24 feet long and 1 foot broad). It branched frequently and dichotomously, and carried leaves which formed apical tufts. ‘The leaf was long, linear-subulate, and early deciduous. A single median bundle runs the whole length of each leaf. The leaves are clearly arranged in whorls at first, but become distant and quincuncially arranged in older stems, owing to unequal extension of the stem surface. The leaf-scars are always small, and, papillate at first, become flush with the stem surface later on, or even a little sunk below it. Sometimes, however, the papille are quite pronounced in older stems. The leaf-scar, in a well-preserved stem, shows the nsual lepidophyte scars, specks, or cicatricules, but the ligular scar is difficult, often impossible, to observe with certainty. The shape of the leaf-scar changes with age. In the young shoot it is circular-triangular, with the apex directed upwards, and in older shoots sub- SCIENT. PROC. R.D.S., VOL. XIII., NO. XXXIV. 45 524 Scientific Proceedings, Royal Dublin Society. circular in outline, with a projecting ring-like border, pronounced below and passing off upwards into a sloping ledge, which may be regarded as part of the leaf-field cushion. The stem surface of B. kiltorkense shows a finely and longitudinally striate epidermis. The direction of these stria is disturbed by the leaf-scar’s position. In addition the stem may show a marked fluting or ribbing which is connected with the parichnos and bundle-strands, but possibly also with internal sclerotic bands. The calamitoid appearance of such stems is increased by the presence of horizontal or transverse ridges or zones which are, unlike the longitudinal ridges, coincident with the surface leaf-scars, and suggestive of nodal diaphragms. B. kiltorkense bifurcated at its base to form the Stigmaria rhizomatous stage carrying numerous branching vascular root-like appendages. ‘The cone is terminal, and carried on its broad (hollow ?) axis numerous whorls of sporophylls, of which the megasporophylls are the ones at present best known. Lach bore on its enlarged basal part some twenty more or less rounded megaspores, 1 mm. in diameter. Certain sporophylls with thick irregularly rugose surfaces appear to be the male sporophylls, the microspores being 0°5 mm. in diameter. Bothrodendron offers marked calamitoid features, which show it to be nearer the common ancestral type of the Lepidophyta and Equisetacese (Articulate) than either Lepidodendron or Sigillaria. BIBLIOGRAPHY. 1. Fores, E.: On the Fossils of the Yellow Sandstone of the South of Ire- land. British Association Report, London, 1853 (Belfast Meeting, 1852), p. 43. Further references are given in my paper, “Is Archzopteris a Pteridosperm?” Scient. Proc. Roy. Dublin Soe. (N.S.), vol. xiui, 1911. 2. Haventon, S.: On Cyclostigma, ... Plates XIV-XVII., Journal Roy. Dublin Soc. vol. ii, 1859, p. 407. Haughton’s paper appeared also in the Annals and Magazine of Natural History (vol. v, 3rd series), but without the illustrations. 3. GrirFitH, R., and A. Bronentart: Journ. Geol. Soc, Dublin, vol. vii, 1857, p. 287. 4, —— —— Journ. Roy. Dublin Soe. vol. i, 1858, p. 313. 5. Heer, O.: 1. Quart. Journ. Geol. Soc. vol. xxviii, 1852. 2. Fossile- Flora d. Baren-Insel, 1871. 10. ite Jounson—On Bothrodendron (Cyclostigma) kiltorkense. 525 . Haventon, 8.: Journ. Geol. Soc., Dublin, vol. vi, p. 227, 1855. . Ruopsg, J. G.: Beitrage zur Pflanzenkunde der Vorwelt, 1820. . Jukes, J. B.: Explan. to Sheets 176 and 177 (1861) of the Geological Survey of Ireland, fig. 3, p. 17. . Ricurer, R., und F. Unesr: Beitrige zur Paliontologie des Thiiringer- Waldes., Teil ii, Schiefer u. Sandsteinflora (Denks. d. Kais. Akad. d. Wissensch. Mathem.-Naturw. Klasse, Bd. xi-xii, 1856), p. 178, Taf. x., fie. 9, 10. Naruorst, A. G.: 1. Zur Oberdevon. Flora d. Baren-Insel. Kéngl. Svenska Vet.-Akad. Handl. Stockholm, mit 14 Tafeln, Bd. xxxvi, No. 3, 1902. 2. Zur Palsoz. Flora d Arkt. Zone. Kéngl. Svenska Vet.-Akad. Handl., mit 16 Tafeln. Bd. xxvi, No. 4, 1894. Sorms-Lavusacu, H. Graf zu: Ueber die seinerzeit von Unger beschrie- benen strukturbietenden Pflanzenreste des Unterculm von Saalfeld in Thiringen, K6nigl. Preuss. Geolog. Landesanstalt. N.F. Bd. X1X-xxili, 1895-97, s. 21. Fossil Botany, being an Introduction to Paleophytology, p. 298. Clarendon Press, Oxford, 1891. . Batty, W. H.: British Association Reports (1869 and 1870). Addit. Notes on the Fossil Flora of Ireland. Journ. Roy. Geol. Soc. Ireland, vol. iii (new series), 1870-73, p. 48. . ScuimprrR, W. P.: Traité de Paléontologie Végétale, 1869-74. . Kinston, R.: Catalogue of Palsozoic Plants. (Department Geol. and Palzont., British Museum, Nat. Hist. 1886, p. 236.) . Poronizt, H.: Die Silur- u. die Culm-Flora d. Harzes u. d. Magde- burgischen, s. 32 et seq. (Abhandl. d. K6nigl. Preuss. Geolog. Landesanstalt, N.F., Heft 36, 1901). . Stopes, Dr. Mariz: British Association Meeting, 1912, Dundee (Geolo- gical Section Abstracts). . Dawson, J. W.: The Fossil Plants of the Devonian and Upper Silurian Formations of Canada. Geol. Surv. Canada, Montreal, 1871-72. . Scorr, D. H.: 1.On Cheirostrobus. Phil. Trans. R. Soc., vol. clxxxix (B), 1897. 2. Studies in fossil Botany, 2nd edit., vol. i, 1908, p. 123, . Watson, D. M.: Bothrostrobus. Memoirs and Proceedings Manchester Lit. and Phil. Soe., vol. lii, 1908. . Renier, A.: L’origine raméale d. cicatrices ulodendroides. (Comptes Rendus de l’Acad. des Sc., 1908.) . Kinston, R.: Les Végétaux Houillers recueillis dans le Hainaut Belge. Notes addit. (p. 267). (Mém. du Musée Royal d’Hist. Nat. de Belgique, t. iv, 1909.) 526 Scientific Proceedings, Royal Dublin Society. 25. ZeiviER, R.: Eléments de Paléobotanique, 1900. 26. Weiss, F. E.: A Stigmaria with Centripetal Wood. Annals of Botany, vol. xxii. 27. McLean, R. C.: Two Fossil Prothalli from the Lower Carboniferous Measures. New Phytologist, vol. xi, 1912. (Plates v and vi.) 28. Sewarp, A. C.: Fossil Plants, vol. ii, p. 257. University Press, Cam- bridge, 1910. EXPLANATION OF PLATES. (The illustrations are from photographs taken mostly by Mr. T. Price.) PLATE XXXV. aT Portion of a stem, slightly enlarged, of Bothrodendron kiltorkense, showing attached foliage. The specimen illustrated is part of the Lepidodendron Griffithii of Bronguiart’s letter to Dr. Griffith. (The Botanical Division, National Museum, Dublin.) 2. Portion of the stem, showing more or less closely crowded leaf-scars in upper part in whorls and more distant spirally arranged leaf-scars in lower part (3). Compare the lower part with the stem surface in fig. 1. (Geological Museum, Trinity College, Dublin). 8. Surface of stem showing zonation. ‘The leaf-scars on the left are less zonately arranged. The stem-surface is like that in the upper half of fig. 2, slightly enlarged (¢). It appears to illustrate Heer’s interpretation of Haughton’s C. minutwm. (Geological Museum, Trinity College, Dublin.) : 4 and 5. Calamitoid impressions of stems in Knorria-stage. The upper end of fig. 5 on the right gives some indication of the spirally arranged leaf-scars (4). (Geol. Sury. Ireland Collections). PLATE XXXVI. Fig. 1. This impression of Bothrodendron kiltorkense shows that the stem divided dichotomously, and bore apical tufts of long subulate deciduous foliage leaves. The right-hand prong shows the stem-surface with almost horizontal whorls of leaf-scars (£). (See fig. 1, Pl. XXXVII.) (Geol. Surv. Ireland Collections.) 2. An older forked stem, prongs unequal in thickness. In addition to the leaf- scars the longitudinal striation is observable (2). (Geol. Surv. Ireland Collections.) (This figure is numbered ‘8 ”’ in error.) Jounson— On Bothrodendron ( Cyclostigma) kiltorkense. 527 PLATE XXXVII. Fig. 1. Bothrodendron kilkortense.—This is a magnified view of the stem-surface of fig. 1, Pl. XXXVI. (4). The whorls of leaf-scars stand out well. The bases of the attached leaves are recognizable on the left. 2. A stem-surface showing projecting (somewhat Halonia-like) leaf-scars (2). . The stem-surface with depressed leaf-scars (4). 4. A single leaf-scar with surrounding stem-surface enlarged (2°). The three scars or cicatricules representing the vascular bundle (central scar) and the parichnos (right and left) are distinctly observable. The sub- circular leaf-scar has a projecting border. On the lower border there is a sear possibly connected with the parichnos-strands. It is a matter of conjecture whether there is a ligular scar or not observable. 5. Knorria acicularis stage of stem. Natural size. 6. Branching stem, suggestive somewhat of a drooping habit. Leaf-scargs in various stages (#). (Geol. Sury. Ireland Collections.) (Se) es PLATE XXXYVIII. ig. 1 and 2 show two stems, at first sight, quite unlike Bothrodendron. In fig. 1 the longitudinal fluting is more pronounced than the transverse zonation, though this is observable in places (+). (Geol. Surv. Ireland Collections.) Fig. 2 shows a markedly calamitoid stem. The longitudinal grooving is accompanied by the zonation which coincides with the leaf-scars, and suggests nodal diaphragms (4). (Botanical Division, National Museum, Dublin.) 3. A piece of stem-surface in fig. 2 enlarged. The ridges and furrows with typical leaf-scars of Bothrodendron are evident. The relation of the leaf- scar to the ridge varies, being at one place on it, at another in the groove (4°). . 4. Knorria Selloi stage of B. kiltorkense, showing the truncated apical ends of the leaf-strands, and the fluted surface of the petrification. (Royal College of Science, Dublin, Collections.) 5. Stem of B. kiltorkense, showing the horizontal zonation, coincident with the whorls of leaf-scars, (Trinity College, Dublin, Geological Museum.) PLATE XXXIX. Fig. 1. Basal part of the stem of Bothrodendron kiltorkense with surface sculpturing passing into the Stigmaria ficoides bifurcating rhizome, covered with appendage scars (3). (Geological Survey Museum, London.—Number 26,238.) SCIENT. PROC. R.D.S., VOL. XIII., NO. XXXIV. AI 528 Scientific Proceedings, Royal Dublin Society. PLATE XL. 1. A broken piece of stem of Bothrodendron kiltorkense. The lower half shows parts of several whorls of leaf-scars seen from without. The dark upper part is the cortical surface of the stem, with leaf-scars seen from within. It is probable that this is the type specimen of Haughton’s Cyclostigma Grifithi. Haughton was Professor of Geology in Trinity College, Dublin, at the time he gave specific names to his Cyclostigmas; but he does not appear to have labelled his specimens. Slightly enlarged (¢). (Cp. this fig. 1 with his fig. 3, Pl. xiv, Journ. Roy. Dubl. Soc., vol. ii.) (Geological Museum, Trinity College, Dublin.) 2. A piece of stem-surface, showing well-marked leaf-scars in whorls (3). (Botanical Laboratory, Royal College of Science, Dublin.) 8. A piece of stem-surface, showing distant leaf-scars, and one ulodendroid scar below (¢). (Geol. Sury. Ireland Collections.) 4 and 5. Branching appendages of the Stigmaria stage, showing the axial vascular strand ($) (Geol. Surv. Ireland Collections.) PLATE XLI. Fig. 1. A piece of stem of Bothrodendron kiltorkense in the Knorria acicularis stage (t). (Cf, fig. 28, p. 63, in Potonié’s “ Die Silur-Flora.”) Geological Museum, Trinity College, Dublin. 2. End view of the same stem, showing a crushed hollow cylinder (+). 3. Cone or strobilus of Bothrodendron kiltorkense (Lepidostrobus Bailyanus, Schimper) (4). (Geol. Sury. Ireland Collections.) 4. Cone of same broken across, showing the whorls of sporophylls (4), and hollow axis. 5. Three isolated megasporophylls, showing the fertile spatulate base, and the long sterile lamina (+). (Geol. Sury. Ireland Collections.) 6. A group of 10-12 fertile sporophyll bases only, mostly male apparently (2). (Royal College of Science, Dublin, Collections.) 7. A few megasporophylls (;). The megaspores (1 mm. in diameter) are observable. The sterile lamina does not lie in the same plane as the fertile base, but is joined to it at an angle(?). (Royal College of Science, Dublin, Collections.) 8. The four megasporophylls show more clearly still the obliquity of the sterile distal to the fertile proximal part of the sporophyll (2). (Royal College of Science, Dublin, Collections.) SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XXXV. SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. PLATE XXXVI. SCIENT. PROC. R. DUB c | , ay 5 fi p, PLATE XXXVIII. SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. pyaar ee pen ie rb XIXXX FLVId TIX “IOA “S'N “OOS NITANd “U -OONd “LNAIOS SCIENT. PROC. R. 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THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 36. MARCH, 1913. ON PURE CULTURES OF PHYTOPHTHORA INFESTANS DE BARY, AND THE DEVELOP- MENT OF OOSPORES. BY GEORGE H. PETHYBRIDGE, Pu.D., B.Sc., ECONOMIC BOTANIST TO THE DEPARTMENT OF AGRICULTURE AND TECHNICAL INSTRUCTION FOR IRELAND 5 AND PAUL A. MURPHY, A,R.C.Sc.1. (PLATES XLV, XLVI.) [Authors alone are responsible for all opinions expressed in their Communications. } . DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price One Shilling and Sixpence. Roval Bublin Society. Oe FOUNDED, A.D. 1731. INCORPORATED, 1749. OOOO EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can. be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Ilustrations in a complete form, and ready for transmission of the [ditor. PuraysripgE— On the Rotting of Potato Tubers. 565 Figs 18. 19. 20. 21, 22. 23. 24, 25. 26. 27. A ripe oospore within the oogonium. The details of the base of the oogonium ; antheridium and hyphae are only approximately indicated. Living material. x 625. The sexual organs showing a terminal antheridium and an oogonium derived from a terminal incept. The beaded edge of the broken top of the antheri- dium is well marked. Living material. x 425. The same as fig. 19, two days later, showing an early stage in the formation of the spore. Living material. x 425. Conidia showing sympodial development. Drawn after treatment with I in KI. x 625. P. infestans, showing the funnel-shaped base of the oogonium within the antheridium. The upper part of the funnel is obscured by the presence of portions of the browned oat-agar-medium adhering to the antheridium. These also adhered to some extent to the spherical part of the oogonium, but did not obscure it, and have been omitted in the drawing. Living material. x 365. Sexual organs of P. Phaseoli from living material in Lima Bean Agar, showing clearly the course followed by the developing oogonial incept. x 865. Sexual organs of Coleman’s P. omnivora var. Arecae, from his plate 18, fig. 8. x 835. P. Syringae Kleb. Sexual organs developed within the tissues of sterile carrot. The base or stalk of the oogoninm is not within the antheridium. Living material. x 365. P. Cactorum Schroet. Sexual organs developed in a cover-glass film of carrot extract gelatine. The antheridium an is partially covered by a portion of the hypha bearing the oogonium. The contents of the antheridium at this stage had become very reduced in amount and degenerated, and for the sake of clearness are omitted from the drawing. Living material. x 865. Sexual organs of P. Fagi developing in {cover-glass film of carrot extract gelatine, drawn just before fertilization occurs, and showing the lateral penetration of the oogonium by an outgrowth from the antheridium. Living material, x 365. SCIENT, PROC. R.D.S., VOI. XIII., NO. XXXV, 4p f 566 XXXVI. ON PURE CULTURES OF PHYTOPHTHORA INFESTANS DE BARY, AND THE DEVELOPMENT OF OOSPORKS. By GEORGE H. PETHYBRIDGH, Pu. D., B.Sc., Economic Botanist to the Department of Agriculture and Technical Instruction for Ireland ; AND PAUL A. MURPHY, A.R.O.Se.1. PLATES XLV, XLVI. [Read Ferrvany 25. Published Marca 26, 1913.] J. InrropuctTory. In endeavouring to ascertain the life-history of any parasitic organism, two ways of approaching the subject present themselves. The first, and perhaps the one hitherto most frequently employed, is to obtain the details from the parasite as it grows upon its host. The second is to grow it in pure culture as a saprophyte on a suitable artificial medium, if such can be found, and study its development under such conditions. It is, of course, both theoretically possible, and it has been found to be the case in some instances, that under artificial conditions the parasite may not develop all the stages in its life-history ; but it is also equally possible that under these very conditions the organism may show stages in its cycle of development which are not produced during its career as a parasite. Hence the advantage of approaching the problem by both of the available avenues. In the case of Phytophthora infestans, the parasitic fungus which causes the potato blight, the application of the first method of study has failed so far to reveal with certainty any stage in which sexual organs are produced, although many of its allies amongst the Peronosporaceae have been shown to possess such organs. It is true that certain observers have laid claim to the PerayBripGe AnD MurpHy—On Phytophthora infestans. 567 discovery of such structures in P. infestans when growing on the potato, notably Worthington G. Smith! and Smorawski.’ It would serve no useful purpose to refer in detail in the present paper to the controversy raised by Smith’s publications ; suffice it to say that his views, owing largely to the critical observations of de Bary, did not meet with anything like general acceptance. Smorawski’s work also can scarcely be said to be convincing ; and the bodies described and figured by him as sexual organs do not at all closely resemble the real ones obtained in pure cultures. One of us spent a considerable amount of time a few years ago in searching for possible oospores of P. infestans in the blighted portions of potato-plants. Bodies were found frequently which might have been such structures; but prolonged attempts at causing them to germinate met with absolutely no success; consequently their true nature remained undetermined. Although only failure has to be recorded as regards the search for oospores along this line up to the present, success has been attained, as will be seen, with pure cultures on certain media. That Phytophthora infestans, exquisite parasite though it is often regarded to be, is capable of being grown on a dead substratum has long been known. Possibly Brefeld® was the first to record its growth as a saprophyte when he wrote, in 1883: “Unter den Peronosporeen habe ich mich auf den am meisten wichtigen und characteristischen Pilz der Kartoffelkrankheit be- schrankt.—Die Peronospora infestans wuchs in kiimstlicher Ernahrung wie Unkraut, fast so iippig, wie sie auf den Kartoffeln wachst.” Von Tubeuf states:‘ ‘‘ Phytophthora infestans is more easily reared as a saprophyte [than Exoascus], and occurs in nature as such; hence it approaches somewhat towards the hemi-saprophytes.” Matruchot and Molliard°’ claim to have been the first to grow this fungus in pure culture, both on living and non-living substrata, although Hecke® 1 A general account of Worthington Smith’s observations is to be found in his book, ‘‘ Diseases of Field and Garden Crops,’’ London, 1884, particularly in chapterxxxvi. Various earlier articles on the subject were contributed to The Gardeners’ Chronicle (and to the Monthly Microscopical Journal, yol. xiv, p. 110, and yol. xvi, p. 120) by this author in 1875 and 1876; while photographs of the supposed oogonia and antheridia are to be found in Quart. Journ. Micros. Science, yol. xy, N.S., 1875, p- 360. 2 Smorawski, J.—Zur Entwickelungsgeschichte der Phytophthora infestans (Montagne) de By. Tnaug. Diss. Berlin, 1890. 3 Brefeld, O.—Untersuch. aus dem Gesammtgebiet der Mykologie. Heft v. Leipzig, 1883, p. 9. 4 Von Tubeuf, K., and Wm. G. Smith.— ‘‘ Diseases of Plants induced by Cryptogamic Parasites,”” London, 1897, p. 7. 5 Matruchot, L., et Molliard, M.—Sur la culture pure du Phytophthora infestans de Bary, agent de la maladie de la pomme de terre. Bull. Soc. Mycol. de France, T. xvi, 1900, p. 209. 6 Hecke, L.—Untersuchungen iiber Phytophthora infestans de By. als Ursache der Kartoffel- krankheit. Journal fiir Landwirtschaft, Band 46, Heft ii, 1898, p. 104. 4p2 568 Scientific Proceedings, Royal Dublin Society. stated a couple of years previously that he had grown the fungus saprophy- tically, both on gelatine and in liquid media. The two French savants say : “On a déja observé dans la nature le Phytophthora infestans vivant en saprophyte ; mais a notre connaissance, personne n’est jamais arrivé a en obtenir de cultures pures, ni sur le vivant, ni sur les milieux artificiels. Tout ce qu’on sait sur le développement de cette Péronosporée résulte d’observa- tions faites sur les plantes attaquées ou d’inoculations pratiquées dans les conditions d’aseptie insuffisante.” It would be interesting to know by whom the fact mentioned by these two sets of authors, and apparently acquiesced in later by Brefeld, that this fungus can grow in nature as a saprophyte, was recorded. We have been unable to find any original statement of this kind; but if it isa fact (which is doubtful), it might have an important bearing on the question of the recrudescence of the disease year after year. In the paper just cited Matruchot and Molliard reported that they had succeeded in cultivating the fungus free from contamination with any other micro-organisms, on pieces of living potato-tubers; but as to the non-living media on which they obtained pure cultures they are silent. Conidiophores (and presumably conidia) were produced on both kinds of media. In a further paper,' published in 1903, these authors reported that they had succeeded in getting pure, conidia-bearing cultures of the fungus on living pieces of the fruits of the vegetable marrow (Cucurbita Pepo) and the Spanish melon (Melon d’Hspagne). Pure cultures were also raised on cooked pieces of vegetable marrow, Spanish melon, pear, and turnip, although on the last two the growth was only poor. Conidia were produced on these media or on some of them, but not so abundantly as on the living ones, and their number grew less and less, so that ultimately their production ceased, and the mycelium itself became enfeebled. The fungus also grew on vegetable marrow broth, and produced abundant conidia; but when this was rendered solid by the addition of agar, fewer of these bodies developed. Appreciable growth was also produced in a three per cent. solution of glucose in water. On none of these media was there any development of sexual spores or of chlamydospores. No growth was obtained on cooked potato, or on cooked tomato and various other fruits and roots. Brefeld,’ in 1908, gives fuller details of the nutritive solution in which he had found such good growth to take place. It was prepared by cutting young potato-tubers into thin slices, drying them quickly, and then extracting * Matruchot, L. et Molliard, M.—Sur le Phytophthora infestans. Annales Mycologici, vol. i, No. 6, 1908, p. 540. * Brefeld, O., doc. cit., Band 14, 1908, p. 41. Prruysripce anp Murpay—On Phytophthora infestans. 569 them with cold water. The filtered and sterilized extract, to which a small quantity of beer-wort was added, proved itself an excellent medium, in which copious mycelium was developed as well as conidiophores which were, as regards size, but little behind those found on the potato plant itself. Brefeld found no signs of oospores, and he says!:—“In dem Pilz der Kartoffelkrankheit, Phytophora infestans, liegt ein sicher erwiesener Fall vor, bei welchem Oosporen nicht zur Ausbildung kommen und nur die Conidientrager auf der Oberflache der befallenen, hier schnell absterbenden Pflanzenteile beobachtet werden konnen.... Die Oosporen liessen sich bis jetzt in diesen Kulturen mit Nahrlésungen auch nicht erzielen, wohl aber konnen wir nach der leichten Ernahrung des Pilzes in Nahrlésungen mit allem Grunde annehmen, dass der Pilz von seiner Uberwinterung in don Kartoffelknollen saprophytisch in der Erde weiter wiichst, tiber die Oberflache der Erde kommt und von hier aus in seinen Conidientragern die Hrzeugung der Kartoffelkrankheit in dem oberirdischen Krautig der Nahrpflanze, immer erst in vorgeriickter Zeit, etwa im August, bewirkt.” Meanwhile the question of pure cultures of the fungus in artificial media had been taken up in the United States of America, and Clinton,’ in 1906, reported that he had obtained such cultures in vigorous condition on plugs of living potato and on sterilized corn-meal and water, whilst less satisfac- tory growths were developed on agar-media containing potato- and pumpkin- juice respectively. In all some twenty-five to thirty media were experimented with by Clinton; but in no case were any sexual organs discovered, although in one instance some peculiar swollen bodies were observed which were suggestive of immature oospores. Further results were published by Clinton® in 1909, and, in particular, he found that the fungus grew readily and pro- duced abundant conidia on an agar-medium prepared from the juice of Lima beans (Phaseolus dunatus). In no case, however, were any sexual organs observed. Studies in the cultivation of the fungus had also been carried out by Jones.s In an abstract of a paper read before the the Botanical Society of America, in December, 1908, some of the principal results are briefly stated. The media employed were similar in character to those used by Matruchot and Molliard, and by Clinton. In some of these media oogonia-like bodies were obtained frequently ; in others, they were developed but sparingly. 1 Loe. cit., p. 116. 2 Clinton, G. P.—Downy Mildew, or Blight, Phytephthora infestans (Mont.) de B., of Potatoes. Rep. Connecticut Agric. Exp. Station for 1905. 1906, p. 304. 3 Clinton, G. P.—*‘ Artificial Cultures of Phytophthora, with special reference to Oospores.”’ Rep. Conn. Agric. Exp. Sta., for 1907-8. 1909, p. 891. 4 Jones, L. R., and N. J. Giddings.—Studies of the Potato Fungus, Phytophthora infestans. Science, N. S8., vol. xxix, 1909, p. 271. 570 Scientific Proceedings, Royal Dublin Society. In 1909! and 1910? Jones gave further particulars of his pure cultures of the fungus which he had grown continuously for four years. Oogonia-like bodies were found in cultures on raw potato, in potato gelatine and on Lima bean agar. In some cases apparently fully developed resting-spores were discovered in his cultures, but no traces of real antheridia were found. The spores are described as having a thick spiny brown outer wall with densely granular contents. They resembled in a general way the oospores of other Perono- sporaceae, and bodies similar to them were also seen in potato foliage which had. been destroyed by the blight fungus.* The first announcement of the production in pure cultures of undoubted oospores was made by Clinton in 1911, in an article in which the previous literature on the subject is summarized, while full details of the media used and of the results obtained were published later in the same year.’ Out of about seventy-five media experimented with three are mentioned as having given specially good results, viz., Lima bean-juice agar, a “combination medium” made up from Lima beans, oats, peanuts, potato, sweet corn, wheat, and agar, and lastly oat-juice agar, which is stated to have stood alone so far as the production of oospores is concerned. On it antheridia, oogonia, and oospores were developed ; and in the paper quoted these are fully illustrated and described. It will, we think, at once be conceded that corroboration by other workers of such interesting and important results was highly desirable, and, seeing that we enjoyed particular facilities for work on P. infestans owing to the establishment by the Department of Agriculture and Technical Instruction for Treland of a temporary station in the west of Ireland (where the potato blight is particularly prevalent) for special investigations into the various diseases to which the potato is subject, we commenced early in the summer of 1911 the study of the development of this fungus in pure cultures. Over twenty media or modifications of media have been experimented with, and many hundredsof cultures have been studied during an uninterrupted period of some eighteen months. True oogonia, antheridia, and undoubted 1 Jones, L. R.—<‘‘ Resting-Spores of the Potato Fungus Phytophthora infestans.’ Science, N.S., vol. xxx, 1909, p. 813. 2 Jones, L. R., and A. B. Lutman.—‘‘ Further studies of Phytophthora infestans.’’ Science, N.S., vol. xxxi, 1910, p. 752. 3 Since the above was written we have received a fuller description of Jones’s work contained in a paper entitled, ‘‘ Investigations of the Potato Fungus Phytophthora infestans,’’ by L. R. Jones, N. J. Giddings, and B. F. Lutman, and published in 1912 by the Bureau of Plant Industry, U.S. Department of Agriculture, Washington. 4 Clinton, G. P.—“ Oospores of Potato Blight.’”’ Science, N.S., vol. xxxiii, 1911, p. 744. 5 Clinton, G. P.—‘ Oospores of Potato Blight, Phytophthora infestans.” Rep. Conn. Agric. Exp. Sta. for 1909-1910. 1911, p. 753. PETHYBRIDGE AND MurpHy—On Phytophthora infestans, 571 oospores have been found on one of these media—a modification of Clinton’s oat-juice agar; and further than this the study of a new species of Phytoph- thora,' which produces a new and characteristic type of rot in the potato tuber, carried on simultaneously with the cultures of P. infestans, has enabled us to throw very considerable light upon the mode of development of these organs in the latter fungus. Hence Clinton’s results are both fully corroborated and substantially am plified. II. Nores on 'EcHNIQue. The cultures were obtained in the first instance from affected foliage. On keeping this in the laboratory for a day or two under suitable conditions, plenty of aerial mycelium, bearing conidia, is developed. In some cases conidia were allowed to fall on to the surface of a suitable artificial medium in Petri dishes; and not infrequently a pure culture could be obtained by removing a small portion of the mycelium developing from a single conidium to a suitable sterile medium. The important thing is to have the infective material as freshly grown as possible, since under these conditions there is less chance of the presence of the spores of other organisms, such as Fusarium, &e. In other cases pure cultures have been obtained by lightly touching fresh aerial conidia-bearing mycelium with a sterile, moistened platinum loop and transference to a suitable slant in a test-tube. Of course, some of the cultures obtained in this way are impure, but with care a comarsleval le proportion of them can be obtained pure from the start. Another method employed was to prepare, under as strictly aseptic conditions as possible, blocks of living potato-tuber tissue and infect them from the original material. Phytophthora infestans develops fairly rapidly on the living potato, and by this means the presence of common saprophytic fungi, such as Penicillium, Mucor, &c., can be avoided. Since the fungus does not develop very rapidly on the artificial media used, it was soon found that Petri dishes were entirely unsuited for the prolonged cultures necessary ; consequently nearly all our cultures were carried out on slants in test-tubes, or, if liquids were being used, in shallow layers in small flasks. In removing portions of cultures from tubes, steel lancet-pointed needles were used which were kept standing in strong alcohol. Immediately before being used they were removed and the spirit on themignited. By this means the 1A full account of this new species (P. erythroseptica) will be found in Scient. Proc. Roy. Dublin Soc., N.S., yol. xiii, No. xxxv, 1913, p. 529. 572 Scientific Proceedings, Royal Dublin Society. needles were sterilized without becoming unduly heated, and without suffering from the corrosion which follows from the frequent strong heating of a steel needle in a flame. Platinum needles are, of course, much too flexible for this work. The oogonia being of a distinct brown tinge were easily discernible in the media under a low-power dissecting microscope, although they are just beyond the limit of vision by the unaided eye. In examining them, small portions of the media containing them were removed; and, as a general rule, each individual oogonium or oogonium and its adhering antheridium was dissected out of the medium under the dissecting microscope, mounted in a drop of water and covered with a cover-slip. Excess of water, if any, was removed by means of blotting-paper, and the preparation was then irrigated with a drop of a 24 per cent. solution of caustic soda. This tended not only to clear up somewhat any small opaque portions of still adhering medium, but to some extent cleared away the rather deep-brown colouring-matter in and around the oogonium. When the clearing process had gone far enough, the soda was neutralized by irrigating the preparation with a drop of weak acetic acid solution. If the clearing was allowed to go too far, and particularly if no spore was present in the oogonium, the latter was frequently apt to swell up and burst. - More or less successful attempts were made in our earlier preparations to obtain the oogonia free from the semi-opaque starchy medium (oat-agar), in which alone they developed, by a process of digestion of the latter with malt- extract. This plan did not, however, offer any special advantages; and the method described of first mechanically dissecting away under the microscope the greater part of the medium from around the oogonium proved itself, with a little practice, to be in the end the simplest and most satisfactory. It is perhaps unnecessary to add that the strictest control was exercised over the cultures, both by microscopic examination and by control cultures to obtain and to keep them pure; and there is no room for doubt but that the sexual organs described do belong to Phytophthora infestans, and to no other fungus. III. Purr Cuirurres on Mepis in wHich no SEXUAL ORGANS WERE FOUND. (1) Growth on sterile, raw Potato.—It is commonly but erroneously supposed that P. infestans produces a more or less soft wet rot in potato tubers. As a matter of fact, however, tubers when infected with this fungus, whether naturally or artificially, remain hard and firm, showing the well- known and characteristic dark and sunken areas on the skin, unless the PETHyBRIDGE AND MurpHy—On Phytophthora infestans. 573 attack is followed by that of another, or of other organisms, when the subsequent fate of the tuber will depend upon the nature of these secondary organisms, and upon the conditions under which the tuber is kept. In reality, therefore, the rot produced in a tuber by this fungus is essentially a form of dry-rot. In practice it is not an easy matter to grow the fungus in a whole tuber in such a way that one can be absolutely sure that the growth will remain pure all the time. Our methods of procedure with whole tubers, and the results, have been as follows :—Clean, healthy tubers, with unblemished skins, were selected and carefully washed in running water, a soft brush being used. They were steeped for a period in a dilute solution of either formalin or mercuric chloride, and then dried. Inoculation was made with a small portion of mycelium, generally bearing conidia, from a pure culture of the fungus on an artificial medium, through a shallow stab into the skin of the tubers. ‘The tubers were then allowed to stand in a covered glass dish, sometimes on a piece of moistened filter-paper, sometimes without this, at room-temperature. Asa rule, in from five to seven days, a somewhat dark, sunken area is formed around the original point of inoculation; aerial mycelium, bearing conidia, may or may not develop at the inoculation-wound. This dark, sunken area gradually extends; and in the course of four weeks or so the greater part of the skin of the whole tuber may have become similarly affected; on the other hand, in some cases, after the lapse of a similar period, the diseased area may be much smaller. Inoculated tubers lose some of their water more quickly than control tubers, treated similarly (i.e. stabbed, but with a sterile needle),do. This water tends to condense and to collect on the lower surface of the tuber between it and the bottom of the glass dish. When this is the case or when the inoculated tuber has been placed on moistened filter-paper at the outset, the lower part of the tuber becomes affected more rapidly than the upper. Experiences of this kind and others which have been encountered lead us to believe that the skin of a potato must not be looked upon as a mere physical membrane impervious to water, for its properties, with regard to the passage of water both inwards and outwards, appear to be radically altered when the living cells adjacent to it become killed. This idea is supported by the experiments of Stoward,! who found that certain chemical substances in solution pass much more readily into a tuber through the skin over dead portions of tissue 1 Stoward, F.—‘‘The Effect of certain Chemical Substances on the Vitality of the Buds of Potato Tubers, and their Disinfectiye Action on Potato Blight (Phytophthora infestans).’’ Proc, Roy. Soc. Victoria, vol. xxiv (New Series), Pt. 2, 1912. SCIENT. PROC., R.D.S,, VOL. XIII., NO. XXXVI. 4Q 574 Scientific Proceedings, Royal Dublin Society. than over still living areas. ‘The diseased areas on the surface of an inocu- lated tuber are distinctly harder to the touch than the still healthy areas, and they are also tougher when cut with a knife. As a rule, the darkening of the skin precedes its sinking in. On cutting open such inoculated tubers the tissues show the mottled brown or rusty markings so characteristic of the attacks of the fungus, as seen in naturally affected tubers. The extent of the browning depends largely on the time which has elapsed since inoculation took place, but perhaps also to some extent upon the individuality of the tuber.’ It is commonly supposed that this brown discolouration of the dead tissue is the result of the action of the fungus in question; but Matruchot and Molliard maintain that this is not the case. They state that aseptically obtained cylinders cut from the tissues of tubers and artificially inoculated with P. infestans remain for an indefinite period white and firm, retaining the same aspect as non-inoculated controls, and simply drying up like tlie latter do. We have paid considerable attention to this question of the browning of affected tissue, and find that it does occur in pure cultures of the fungus on cylinders of raw potato-tissue prepared aseptically; and we cannot but conclude that the browning is due to the action of the fungus, as is generally believed. One of our critical experiments on this point deserves to be described in detail. ‘Twelve cylinders of living tissue were prepared under as strictly aseptic conditions as possible, and were transferred with the greatest possible pre- cautions to sterile test-tubes. These were then kept for a period of ten days at room (summer) temperature, when close scrutiny showed that nine of them were sterile, whilst the other three had become contaminated. Hach of these nine cylinders was then inoculated from a pure culture of P. infestans. At the time of using this culture it was subjected to microscopic and also cultural control,’ to make sure that it was what it purported to be—namely, a pure culture. The nine inoculated cylinders produced a good growth of the fungus and they became typically browned, as we have observed in other pure cultures. 1 Experiments carried out by one of us since this paper was written show that different varieties of potatoes differ considerably in their reaction towards the fungus. In a variety like ‘“‘ Shamrock,” which in the field is practically immune to the blight both as regards foliage and tubers, the tubers rot much more slowly when inoculated with P. infestans than do those of a variety such as ‘‘ British Queen,’’ which possesses no marked resistance to the disease. * Practically all of the common moulds, as well as species of Fusarium, &c., will develop on wort-gelatine, as will also the majority of ordinary bacteria. P. infestans makes absolutely no growth on this medium. Portions from the pure culture when placed upon wort-gelatine slants produced absolutely no growth ; the slants remained absolutely sterile. The microscope revealed no foreign organisms in the culture. Hence we concluded that it was pure. Peruysripce anp MurpHy—On Phytophthora infestans. 575 After the lapse of periods of time varying from nine to twenty days small portions of the browned tissue were removed from eight of the tubes and transferred as carefully as possible to slants of wort-gelatine. This was no easy matter, since, as mentioned above, the diseased tissue becomes very tough, and to cut off small portions from the affected cylinders situated in the bottoms of test-tubes without at the same time running considerable risk of contamination presents some difficulties. In two cases Penicillium, in another an unidentified mould, and in a fourth bacteria developed on the wort- gelatine slants. We have every reason for believing that these contamina- tions arose during the process of transference, for in the remaining four cases the wort-gelatine slants remained absolutely sterile. Finally, the remaining portions of the eight affected cylinders were removed and subjected to microscopical examination, when absolutely uo bacteria and no fungus other than P. infestans could be discovered. A somewhat similar experiment was carried out on whole tubers. These were washed, disinfected, dried, and inoculated with the pure culture. After about three weeks the tubers were cut open under strictly aseptic conditions, when the browned, diseased areas were found as usual. Small portions of this browned tissue were removed and planted on one oat-agar and three wort-gelatine slants. The three latter remained absolutely sterile, while on the oat agar P. infestans developed in characteristic fashion, but no other organism of any kind was present. If therefore there is an organism which is associated with P. infestans in causing the brown discolouration, it does not grow either on wort-gelatine or on oat agar; and since the pure culture originally used had been obtained from a long series of periodical transferences from oat agar to oat agar, it is practically impossible to believe that any such organism could have been present; and we are forced to the conclusion that P. infestans is alone responsible for the well-known browning. Jones found, as stated above, that oogonia-like bodies were formed in his pure cultures on raw potato. We have never seen them on this medium ; but it must be admitted that our search for them here has up to the present not been so prolonged or so thorough as has been the case with other media. A pure culture on Lima bean agar, which Professor Jones was good enough to send us early in 1911, contained the fungus in active growth and ina normal condition of virulence ; but microscopic examination of this particular culture failed to reveal the presence of any bodies suggestive of sexual organs in it. (2) Growth in raw Potato-jwice—Six medium-sized tubers were well washed, peeled, chipped into small portions, and then well squeezed through 4Q2 576 Scientifie Proceedings, Royal Dublin Society. a potato-masher. About 80 ¢.c. of juice were thus obtained, to which was added an equivalent quantitity of water. This was allowed to stand over night in a tall cylinder, when the starch-grains and other suspended solid matter became sedimented. ‘he supernatant liquid was siphoned off and filtered through a Chamberland filter into a sterile flask, the sterile juice being then distributed into sterile flasks. A portion of the unfiltered (non- sterile) juice was also transferred to a sterile flask. Ten flasks were inoculated from a pure culture of P. infestans, and were allowed to stand at room- temperature for a considerable period, while side by side with them stood similar uninoculated flasks containing the juice as controls. During this time, somewhat to our surprise, the fungus made little or no apparent growth in any of the flasks. The experiment was repeated at a later date, flasks containing the filtered (sterile).and unfiltered juice being inoculated with both conidia and small portions of mycelium from a pure culture. No growth whatever occurred in the unfiltered juice, possibly because it rapidly underwent putrefactive decomposition at the hands of bacteria. The filtered juice remained sterile, but where inoculated with conidia no growth occurred. When mycelium from a pure culture, however, was placed in the filtered juice, it not only remained alive for about three weeks, but increased in amount to a small extent. This freshly developed mycelium frequently presented curious deformities in structure some of which are illustrated in figs. 1, 2, and 3, Plate XLVI. We do not consider these structures as being attempts at the formation of sexual organs; but in many instances they certainly would seem to be malformed or abortive conidia,! their condition being due in all probability to the fact of their being submerged ina liquid, and not produced, as is normally the case with P. infestans, in the air. Our experience as well as that of other workers, such as Himmelbaur, seems to show that the produc- tion of hyphae, with abnormal growth, is more or less common in several species of Phytophthora when cultivated on artificial substrata. (3) Growth in Potato-juice Agar and Potato-juice Gelatine—The potato-juice is prepared in the cold as above, and then boiled and filtered. It is stiffened by the addition of 10 per cent. to 12 per cent. of gelatine or 1°25 per cent. of agar. The juice is naturally slightly acid, and the addition of gelatine renders the medium still more acid. In some cases the acidity of the gelatine was neutralized before use—in others not. On these media growth certainly takes place, and conidia are to some ‘Some of the structures figured by Jones as occurring in potato-gelatine cultures would also seem to be susceptible of a similar interpretation. PrrHyBripGE AND MurrpHy—On Phytophthora infestans. 577 extent produced ; in some cases they were observed submerged in the medium. But, on the whole, growth is decidedly poor, and no signs of oogonia or antheridia were observed. (4) Growth on Potato-jwice-wort Agar and Gelatine-—These media were prepared similarly to the foregoing except that an amount of beer-wort equivalent to the amount of potato-juice was added. Growth is very similar in these two media. For the first week or so the mycelium develops and remains submerged; then aerial mycelium arises and afew conidia are borne. No sexual organs were observed, but in the agar medium swollen hyphae were quite abundant, which appeared as if they might be the early stages of oogonia, but they were never observed to develop into these bodies. The fungus remains alive in the agar medium for many months. (5) Growth on “ Salep”’ Agar.—Salep is a preparation made from the dried roots of certain orchids. It was used by Bernard’ in his work on the fungi living in the roots of orchids, and subsequently by Klebahn? and Himmelbaur,’ for the culture of certain species of Phytophthora. We first endeavoured to make up an agar medium containing this substance in accordance with the recipe given by the last-named worker, but found that it would not set solid when cold. On leaving out the tartaric acid and the inorganic salts, which seemed superfluous when ordinary tap-water was used, a medium was obtained which set satisfactorily. _ On this medium P. infestans makes slow and somewhat scanty growth. A fair amount of aerial mycelium is developed, on which a considerable abundance of conidia occurs, whilst there is also a fairly good development of submerged mycelium, which ultimately permeates the whole of the medium. No signs of sexual organs were observed in the cultures in this medium. (6) Growth on Lima Bean Agar, filtered and unfiltered —This medium was prepared in accordance with the directions given by Clinton, but instead of straining finally through cheese-cloth as recommended,‘ we filtered through Chardin’s Agar filter-paper. We also used this medium without any final filtering or straining. Considerable care is necessary in making the un- filtered medium in order to avoid frothing up during subsequent sterilization. On the unfiltered medium P. infestans grows quite luxuriantly, little less so indeed than on the Quaker-Oat agar medium presently to be described. 1 Bernard, N.—Rey. Gén. de Bot., xvi, 1904, p. 408. 2 Klebahn, H.—‘‘ Krankheiten des Flieders,”’ Berlin, 1909. p. 37. 3 Himmelbaur, W.—Zur Kenntnis der Phytophthoreen. Jahrb. d. Hamburg. Wiss. Anstalten, 28. Beiheft 3, 1910, p, 43. 4 Conn. Ag. Ex. Sta. Rep., 1907-8, p. 898. 578 Scientific Proceedings, Royal Dublin Society. The aerial mycelium, bearing a prolific crop of conidia, clothes the whole surface of the slant with a dense growth, whilst submerged mycelium permeates the whole of the substratum. The fungus does not remain alive on this medium for so long a period, however, as on Quaker-Oat agar. On the filtered medium the growth is still good, but considerably less luxuriant than on the same medium unfiltered. Some thirty or forty cultures were made on these two media, but they did not extend over a period of many months. Both Jones and Clinton found immature sexual organs on Lima Bean agar, but they were not to be found in any of our cultures. (7) Growth in Oat-extract Agar.—This medium was prepared from 200 grams of very finely ground Quaker Oats, extracted with 1,000 c.c. of cold tap-water. The powdered oats were allowed to stand covered with the water in a corked flask for about five days, a few drops of chloroform having been added to prevent decomposition. Subsequently the whole was well shaken up for some hours on a shaking machine, and then allowed to stand. After sedimentation, the supernatant liquid (about 650 cc.) was siphoned off and heated in the inner part of a double saucepan until the whole of the chloroform was driven off, and 2 per cent. agar was added. The medium was somewhat turbid, but was not filtered. On subsequent sterilization in the autoclave a curdy precipitate was formed, which settled down as a more or less flocculent mass at the bottom of the tubes. P. infestans grows very well on this medium, and soon covers the surface of the slant with a thick felt of aerial mycelium, on which conidia are developed in abundance. The mycelium also makes extensive submerged development. On the whole the growth here is but little less than on Quaker-Oat agar, but no sexual organs were ever seen. This medium, although slightly turbid, is in thin layers, sufficiently transparent to admit of use with advantage for growing certain species of Phytophthora, either in Petri dishes or in films on the lower surface of a cover-glass in a moist chamber. (8) Other Media.—No growth whatever took place on the following media:—Cooked potato ; sterilized bread, carrot and potato-stalks ; potato-stalk extract-agar; wort-gelatine; wort-agar; beef-broth-peptone-gelatine and -agar. TY. Purr Cuntrurrs on Mepia IN wHicH SEXUAL ORGANS ARE FORMED. (1) Clinton’s Oat-juice Agar.—The following is the method given by Clinton for preparing this medium :—“ Fifty grams of ground oats, such as are ordinarily fed to horses, are stirred into about 300 to 350 cc. of water, and steam from an autoclave, by means of glass- and rubber-tubing connected Pretnypriper AnD Murpuy—On Phytophthora infestans. 579 with the stopcock, is run into this in a covered dish for half an hour. This cooks the material without burning, and at a uniform temperature. The coarse sediment of the oats is then strained off through an ordinary fine wire strainer, and 10 grams agar is added to the liquid, which is again treated to the steam for half an hour to melt the agar thoroughly. Some water passes over with the steam during these cookings, so that what little, if any, is needed to bring it up to the required 500 e.c., is added after the whole is drained into a graduated cylinder. After the added water is uniformly distributed by repouring, the medium is placed in the test-tubes, and these are sterilized in the autoclave for fifteen minutes under 7 to 10 lbs. pressure.’ We followed these directions closely, except that steam was not generated from an autoclave, but from a glass flask, and it was passed into the mixture in the first instance for rather less than the half hour, since with the oats we used there was a tendency for the medium to become too stiff to be poured easily if steamed for this length of time. We also found that the half hour’s steaming after addition of the agar was not sufficient to dissolve the whole of it thoroughly ; but by keeping the mixture well stirred during pouring into tubes it could be distributed fairly uniformly through them, and subsequent sterilization completed its solution. When this medium is inoculated with conidia, the early growth of mycelium is confined to its surface, but in due time aerial mycelium becomes visible to the unaidedeye. ‘he period which elapses before this occurs varies from three to nine days, the usual interval being from five to seven days. If Petri dishes are used, the whole surface becomes covered with a thick growth of mycelium in about a week after it has become visible to the naked eye, at room-temperature. On slants in test-tubes during a similar period a fairly dense felt of mycelium is also formed, which completely fills the space available in the tube for some considerable distance up the slant. Conidia are produced in large numbers; and the fungus remains alive in a tube of this medium for several months. Oogonia were also observed, but only sparingly; out of about 150 cultures carried out on it during a period of seven months these bodies were only abundantly present in one case. No antheridia were developed in any of our cultures on this medium; but, in spite of their absence, apparently normal thick-walled oospores were developed in some cases. (See tigs. 5 and 6, Plate XLV.) There are certain disadvantages connected with this medium which caused us to give up its use in favour of the one next to be described. It was trouble- some to prepare and difficult to pour in a clean fashion into tubes. Its most serious drawback, however, was that certain starch-containing cells in which the grains had become swollen during cooking and sterilization, but not 580 Scientific Proceedings, Royal Dublin Society. sufficiently so as to cause the cells themselves to burst, remained distributed here and there throughout the medium. These cells were about the same size as the oogonia; and since their walls were also brown, it was impossible to distinguish them from the oogonia without the use of the compound micro- scope. Hence when looking over culture-tubes for the presence of oogonia with a pocket-lens, the presence of these bodies was the cause of considerable inconvenience. Ground Quaker-Oats Agar.—This is the medium which has given us the best results; it is prepared as follows :— Thirty grams of Quaker Oats! are ground in a small hand-mill, with adjustable frictional surfaces, to as fine a powder as possible. This is then stirred into 500 c.c. of cold water (rain-water or soft water), and placed in the inner vessel of a double saucepan, cold water being placed in the outer. The saucepan is then warmed up; and in from ten to fifteen minutes the oatmeal and water form a rather thin gruel. At this stage 10 grams of strip agar, cut into small pieces, are added, and the heating is continued until the latter has become completely dissolved, the latter process being facilitated by constant stirring. ‘The medium thus prepared is free from lumps, and can easily be poured into test-tubes which are then sterilized in the autoclave, slanted, and allowed to cool. No water is added to make up for the small quantity lost during the cooking process. If the Quaker Oats are not ground fine before using, the medium will be lumpy and stiff. The annoying brown cells, present in our preparations of oats, according to Clinton’s method, are entirely absent in this medium. The growth of P. infestans on this medium is similar to that on Clinton’s oat-juice agar, but somewhat moreluxuriant. The aerial mycelium is more copious, and conidia are formed in very great abundance. Conidiophores which have produced ten conidia on the same hypha are not uncommon, and one was observed which had borne thirteen without becoming branched. Oogonia were borne by the fungus on this medium in far greater abundance than on Clinton’s oat-juice agar. Out of seventy-seven of our earlier cultures on it only eleven failed to produce any, and thirty-four of the remainder produced them very abundantly. Antheridia have been found on this medium as well as oogonia, but up to the present in only three cultures of one and the same series, although, in all probability, they will continue to develop more abundantly as time progresses. 1 Qnaker Oats is a proprietary article of food made in Canada by the Quaker Oats Company for Quaker Oats, Limited, London. It appears to consist of partially cooked, crushed oat caryopses, without the pales. PrTHYBRIDGE AND MurpHy—On Phytophthora infestans. 581 The oogonia are found embedded in the medium mainly along a U-shaped course following the outline of the surface of the slant, and distant a few millimetres from its edge. The apex of the slant is usually free from oogonia. Since they are closely pressed against the glass, as a rule, they can be seen readily with a pocket-lens. They have also been found elsewhere, such as on the surface of the slant, and even on the aerial mycelium, but in smaller numbers. Again and again they have been found in contact with a solid body in the medium, most frequently a small portion of the aleurone layer of the grain which has escaped grinding. This fact, and their abundance in contact with the walls of the tube, seem to suggest that possibly some mechanical obstacle to the forward progress of a hypha may act as a stimulus to oogonia formation ; but this may, perhaps, be only a coincidence. Submerged mycelium does not appear to penetrate far into that portion of the medium at the bottom of the tube, which does not constitute part of the actual slant. : A photograph showing some of the oogonia, as seen under the low power of the microscope, embedded in the medium is reproduced in fig. 3, Plate XLV. V. Genzerat Account oF THE DEVELOPMENT AND STRUCTURE OF THE SEXUAL ORGANS. (1) Influence of Medium, Time, and IUumination on Development of Oogonia.— From a considerably greater number of preliminary isolations, and after much useful experience had been gained in the successful handling of them, nine pure cultures were selected as starting-points, and from them, by continual transfers at suitable intervals, nine series of cultures were kept going and were submitted to extremely close macro- and microscopical observation for many months. ‘he isolations were all made from Clifden material ; and we have no reason to suppose that the nine series of cultures represent so many different “strains”? of the fungus. In all of the nine, oogonia were produced; and in one series antheridia were associated with many of the oogonia. It seems probable that the formation of antheridia is merely a matter of time; and that on prolonged culture these bodies will also appear in cultures of the remaining eight series. Speaking broadly, we have found that when a culture has once commenced to form sexual organs, it continues to do so in the subsequent transfers without intermission ; and although the relative abundance of these bodies may vary somewhat in the successive cultures, as a rule, the subsequent SOIENT. PROC., R.D.S., VOL, XII., NO. XXXVI, 4R 582 Scientifie Proceedings, Royal Dublin Society. transfers from cultures rich in oogonia become themselves, in due time, also well provided with them. It was found that oogonia developed sooner, more abundantly, and with greater regularity on Quaker-Oat agar than on Clinton’s oat-juice agar. Thus six out of the nine series produced oogonia on Clinton’s medium, only one of them abundantly, and the other five somewhat spasmodically ; but when the nine were transferred to the Quaker-Oat medium, oogonia soon began to be produced in all of them, and in most of them quite plentifully. As regards the time taken for oogonia to make their first appearance, it would appear that continued culture on the oat-medium, with several transfers to fresh tubes, is desirable before these bodies develop, at least in any quantity. In the case of the series M.7, oogonia were first found, and in abundance, about one month from the start of the pure culture, and in the second transfer. In the case of series C. 1, about ten days later. In the case of the other members of the nine series, a few-showed some oogonia, and the others none over a period of about six months, during which they were being grown, with transfers at suitable intervals, on Clinton’s Oat agar. Oogonia first began to appear in relative abundance and with constancy when the transfers were made on to our own Quaker-Oat medium at the end of February, 1912. When a small piece of a culture in which oogonia have already developed is transferred to a fresh tube, the time taken for oogonia to develop in the new culture varies considerably. ‘The shortest time observed by us has been six days, but it is frequently very much longer than this. On two occasions sets of parallel cultures were made with a view of ascertaining whether the oogonia would develop better in total darkness than under the alternating conditions of diffused daylight and the darkness.of night. The results showed in both cases that the oogonia developed more rapidly and more abundantly in total darkness. (2) Development of Oogonia and Oospores in the absence of Antheridia, ?.e., parthenogenetically.—The oogonia arise, as a rule, as terminal swellings on fairly stout lateral hyphae ; but they may also arise laterally on a hypha. (See fig. 7, Plate XLVI.) The contents consist at first of finely granular protoplasm, without oil-drops, similar to that found in the general mycelium. As the terminal portion of the hypha proceeds to swell, its contents become more dense (see fig. 4, Plate XLVI); eventually oil-drops appear; and its wall, which becomes the wall of the oogonium, becomes brown in colour, thus hiding from view to a great extent the subsequent changes undergone by the contents. Prruysripcr anp Murpay—On Phytophthora infestans. 583 This reddish-brown colouring matter is a very characteristic feature of the oogonium ; and in addition to staining the wall of the oogonium itself, it diffuses out into and stains the surrounding medium. In this way the thickness of the wall becomes considerably exaggerated in appearance. When the colouring matter is removed, or at any rate is rendered less dense by treatment with alkali, it is seen that the wall is in reality not very thick, although it is distinctly thicker than the walls of the ordinary hyphae, and its double line of contour is readily made out. (See fig. 6, Plate XLVI.) Clinton describes the oogonium wall as becoming thickened by the deposition on the outside of the original coat of a more or less irregular, thick, reddish- brown coat. We regard this deposit as being part of the medium which has become stained by diffusion. As a result of branching two oogonia, and in some cases even three, are borne on one lateral hypha. (See fig. 5, Plate XLVI) The oogonia are distinctly brittle, and slight pressure on the cover-glass suffices to break them open and liberate the contents or the spore if present. Figs. 5 and 6, Plate XLV, are from photographs showing such crushed oogonia. As regards shape the majority of oogonia are pyriform, but a few were observed which were almost spherical (see fig. 4, Plate XLV); and all stages were observed between forms which were practically spherical and those which were distinctly pear-shaped or even so much elongated as to be almost club-shaped. The oosphere and oospore occupy, as a rule, only the terminal swollen portion of the oogonium, although one or two cases were observed where the spores themselves were somewhat pyriform. Fig. 7, Plate XLVI, illustrates one of these. A septum is, in most cases, formed at the base of the oogonium, shutting off its contents from the hypha which bears it. Sometimes, however, this septum is absent, as is shown in fig. 6, Plate XLVI. _ Eyen in the absence of antheridia, apparently normal, thick-walled oospores are produced in the oogonia, which can be discerned after treatment with alkali, or by applying judicious pressure to the cover-glass. Out of 258 oogonia specially examined one by one for the purpose, 87, or roughly one-third, contained oospores with more or less thick walls. The average transverse diameter of the oogonia was found to be 38x, and it varied between the limits of 3lu and 46u. These measurements agree fairly closely with those given by Clinton for the oogonia which developed in his cultures. The oogonium wall is smooth, or at the most shows some occasional irregularities, and cannot be described assculptured. Its outline is of course 4R2 584 Screntific Proceedings, Royal Dublin Society. rather obscured by the brown stain which, as previously stated, diffuses from it into the surrounding medium. The oospores are spherical bodies (with the exception of a few more or less pear-shaped ones which have occasionally been seen) with a thick, colourless, smooth, hyaline wall. Apparently the whole of the protoplasm in the oogonium does not go to form the oosphere and subsequent oospore, for what appear to be remaining portions of it occur between the wall of the spore and that of the oogonium. ‘The diameter of the oospores varies from 28u to 34u, the average diameter being found to be about 30u. The thick- ness of the walls of the oospores measures from 2-3, but is slightly greater (4) when antheridia are present. The spores are filled with colourless, densely granular protoplasm, especially towards the periphery; the central portion is much clearer and more transparent, and the contents thus resemble those described and figured by de Bary for the oospores of other members of the Peronosporaceae. A few attempts have been made to germinate the oospores in hanging drops ; but so far they have met with no success. (3) Production of Oogonia and Oospores in the presence of Antheridia.— Although the oogonia and oospores described above were produced in abundance and with great regularity for many months, the most careful and prolonged search failed for a long time to disclose the presence of antheridia. It was not until a period of some fifteen or sixteen months had elapsed that the presence of anthoridia was observed, and even then only in the cultures of one series (M. 7), which had been all along one of the most robust and prolific as regards the production of oogonia and oospores parthenogenetically. Meanwhile, one of us had been studying for a couple of years the development of a new species of Phytophthora (P. erythroseptica), which causes a serious rot of potato tubers, temporarily designated as “ doubtful” rot. Owing to the knowledge gained by the study of this organism, a detailed description of which will be published simultaneously with this paper,’ we were in a position to understand at once by analogy the course of events in the development of the antheridia, oogonia, and oospores of P. infestans. Our attempts to get P. infestans to form its sexual organs on Quaker-Oat agar in cover-glass film cultures in a moist chamber met with no success, and consequently the stages 1 No spores were observed resembling in any degree the resting spores with protuberances on their walls figured by Jones, and recalling Artotrogus hydnosporus. * See Journal Department Agric. and Tech. Instruction for Ireland, vol. xii, 1912, p. 357. 5 Pethybridge, G. H.—‘‘On a form of Rot in the Potato tuber caused by a new species of Phytophthora, haying a method of sexual reproduction hitherto undescribed.’’ Scient. Proc. Roy. Dublin Soc., N.S., vol. xiii, No. 85. 1918. Prrnysripce anp Murpuy—0On Phytophthora infestans. 585 of development were not actually observed in the case of this fungus; but the final state of affairs which results is as follows :—The antheridia are sub- spherical or oval structures borne on the tips of hyphae, or apparently in some cases as sessile lateral outgrowths on them. The oogonia are pear-shaped struc- tures, and are borne on different hyphae from those carrying the antheridia. The oospore is contained within the spherical portion of the oogonium, the lower, tapering, or funnel-shaped portion of which is actually within, and is surrounded by the antheridium. Hence the oogonium appears at first sight to be a spherical structure, sessile on the summit of the antheridium; but in reality it is pyriform; and its lower portion, which is within the antheridium, is continued out through the base or side of the latter, at which point it is continuous with the mycelium. Asa rule, when an antheridium is present, there appears to be no transverse septum at the base of the oogonium where it joins the hypha which bears it. An oogonium, containing an oospore, with its lower portion within the antheridium, is shown in the photograph reproduced in fig. 7, Plate XLV. In this case the hyphae bearing the antheridium and the oogonium respectively were removed during the dissection of the structure from the medium; but figs. 11 and 12, Plate XLVI, will illustrate more fully the connexion of the oogonia and antheridia, with their respective hyphae. The course of events in P. infestans is in all probability similar to that in P. erythroseptica, in which the antheridium is formed first, as a lateral or terminal structure on the younger portions of the mycelium. The incept of the oogonium develops on a separate hypha, and enters the antheridium either at or near its base. This “oogonial incept,” the top of which is sometimes slightly swollen, remains within the antheridium possibly for some little time—and perhaps fertilization may occur at this period—but gradually grows up through it, and finally breaks out through the top of the antheridium, when it swells out and produces the oogonium proper (i.e. the portion in which the oosphere is ultimately rounded off) in a comparatively short space of time. An oosphere becomes rounded off from a portion of the protoplasmic contents of the oogonium; and from it a thick-walled oospore, similar to that formed in other Peronosporaceae, is developed. This method of development of the sexual organs is very unusual, and necessitates a revision of the genus Phytophthora. A discussion on this point will be found in the paper on P. erythroseptica just alluded to. VI. GenrrAL ConcLusIons. ‘The results obtained by us confirm the work of Clinton, and show that in pure cultures in certain artificial media, Phytophthora infestans does form 586 Scientific Proceedings, Royal Dublin Society. sexually produced spores or oospores. Whether, however, these spores are, strictly speaking, formed sexually or not—that is, whether an actual process of fertilization oceurs or not—cannot be decided at present. In the absence of antheridia, Clinton found that the oogonia did not do more than develop oospheres; but we have found in at least one-third of the cases examined that under such circumstances, both in Clinton’s medium and in our own Quaker-Oat agar, oospores were produced ; and we look upon such spores as having been formed parthenogenetically. These spores resemble those formed when antheridia are present, except that in many cases their walls appear to be slightly less thickened. Even when antheridia are present it is difficult to see how the oosphere can be fertilized, for it is completely shut off from the antheridium by the funnel-shaped base of the oogonium, and no signs of a fertilization track have been observed. It is of course possible that a union of the male and female elements may occur soon after the entrance of the oogonial incept into the interior of the antheridium ; but if fertilization occurs at this stage, it occurs before the formation of the oosphere, which would represent an unusual state of affairs. Clinton was not able to trace the points of origin of the oogonia and antheridia, but states that they seem to arise on separate hyphae. Our observations show that this is actually the case, and moreover they explain Clinton’s difficulty in finding antheridia, except such as were in contact with oogonia which were already well on in their development. Clinton states that the antheridia observed by him often show the superimposed “ oogonial thread”; but we find that this structure, which is in reality the lower part of the oogonium itself, is actually within the antheridium, and not superimposed upon it. Whether the fungus produces oospores in the potato-plant or not is a question which will have to be settled by further research. As stated before, we (as well as other workers) have found thick-walled spores in the tissues of various parts of the potato-plant, which have been destroyed by P. infestans which may possibly have been such bodies, although as a rule they appear to be smaller than the spores obtained in pure cultures. Many of them, too, have been seen to be surrounded by a kind of halo of brownish material which may possibly be the remains of the oogonium wall. If such bodies are produced in the potato-plant, they would doubtless find their way ultimately to the soil, and probably play an important part in keeping the fungus alive over the winter, and in causing infection of the potato-crop during the following season. PErnyBRIDGE AND MurpHy—On Phytophthora infestans. 587 EXPLANATION OF PLATES. All drawings were made with the help of a camera lucida under a Leitz micro- scope with objective 9 and ocular 2, giving a magnification of approximately 730 diameters, and are reproduced reduced to about two-thirds of the original size, viz. 486 diameters. Our thanks are due to Mr. H. A. Lafferty for the drawings (made under our supervision) of figs. 1, 2, 3, 11, and 12. The contents of the spores in figs. 7, 8,9, and 10 are necessarily somewhat diagramatically represented. The reproductions of photographs in Plate XLV are from the original, untouched negatives. PLATE XLY. Fig. 1. Pure culture of P. infestans on Quaker-Oat agar (to which some lamp- black was added previous to sterilization in order to increase the contrast between the fungus and the medium), showing eight days’ growth at room-temperature. Conidia were abundant. (Reduced.) Fig. 2. Pure cultures of P. infestans on Oat agar slants in test-tubes. (Reduced.) Fig. 8. Oogonia as seen embedded in the Quaker-Oat agar medium under low power of microscope (Leitz Objective 3, Ocular 2). Fig. 4. A young spherical oogonium (with oosphere faintly visible) grown on Clinton’s Oat-juice agar. x 625. Fig. 5. A spherical oogonium (touching a hair from the Oat), after gentle pressure on the cover-glass has caused it to burst, showing the parthenogenetically formed oospore within. Grown on Clinton’s Oat-juice agar. x 875. Fig. 6. A pyriform oogonium burst open, with the liberated oospore. Grown on Clinton’s Oat-juice agar. x 875. Oogonium and antheridium of P. infestans grown on Quaker Oat Agar. The oogonium contains a ripe oospore which nearly fills it; and the less dense central portion of its contents is faintly discernible. The funnel- shaped base of the oogonium within the antheridium is clearly visible ; but the hyphae bearing the antheridium and oogonium are not present in this instance, having been broken away, in all probability, during the preparation of the specimen. x 730. Fig. =I PLATE XLVI. Figs. 1, 2, 8. Abnormalities or deformities seen in mycelium growing submerged in potato-juice sterilized by filtration through a Berkefeld candle. They are probably to be regarded as abortive conidial growths. Scientific Proceedings, Royal Dublin Society. . An early stage in the development of an oogonium; no antheridium is present. (Quaker-Oat agar.) . A “twin’’- oogonium in which two oospores would probably have been formed. A distinct wall separating the oogonium from the hypha which bears it is present in this case. (Quaker-Oat agar.) . An oogonium containing a young, parthenogenetically formed oospore. The lower limit of the wall of the oogonium is clearly seen, but there is no septum closing off the oogonium from the hypha which bears it. (Quaker-Oat agar.) . An oogonium borne laterally on a hypha and containing a young pear- shaped oospore, formed parthenogenetically. (Quaker-Oat agar.) . An oogonium (containing a practically ripe oospore) with its lower portion within an antheridium. The hyphae at the base of the antheridium are probably the oogonial and antheridial hyphae; but it was impos- sible in the preparation to determine this with absolute certainty. og =Oogonium, os=oospore, an=antheridium. (Quaker-Oat agar.) . An oogonium (with a practically ripe oospore) with its antheridium. The antheridium is probably a terminal structure borne on the hypha a; the funnel-shaped lower portion of the oogonium, within the antheridium, is probably continuous with the hypha o (at the back) ; but the connection could not be made out with absolute certainty. (Quaker-Oat agayr.) . 10. An oogonium (with a practically ripe oospore) with its lower portion within the antheridium, which is a sessile structure on the hypha aa. The hypha bearing the oogonium was broken off during the removal of the adhering medium. (Quaker-Oat agar.) Figs. 11 and 12. Oogonium, oospore, and antheridium. The irregularities in the oogonium wall are indicated by shading (except over the oospore). In fig. 11 the antheridium is probably a lateral outgrowth of a hypha, the end of which is seen at a, the other portion of it being absent. o is the hypha which bears the oogonium, and it was definitely traced into the antheridium and seen to be continuous with the funnel-shaped base of the oogonium. In fig. 12, the antheridium is a terminal structure, borne on the hypha a; and its contents are represented somewhat contracted away from its walls. o is the hypha bearing the oogonium ; its passage into the antheridium and continuation as the funnel-shaped base of the oogonium were clearly discernible. m is a small portion of adhering medium. (Quaker-Oat agar.) F SCIENT. PROC. R. DUBLIN SOGC., N.S., VOL. XIII. : PLATE XLV. London Stereoscopic Co. imp, OOSPORES OF PHYTOPHTHORA INFESTANS, DE BARY. SCIENT. PROG. R. DUBLIN SOC, N.S., VOL. XIII. PLATE XLVI. OosporEs OF PHYTOPHTHORA INFESTANS DE BARY. Mo bo SCIENTIFIC PROCEEDINGS. VOLUME XIII. A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, (Kidston (Lyginodendron oldhamium, Williamson). By . JoHNson, D.SC., F.L.S. Plates I.-ILI.) (March, 1911.) Is. . 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Part I1.—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jamus H. Powtox, p.sc. (Plates XV. and XVI.) (February 21,1912.) 1s. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, sc.d., ¥.B.s., and W.R. G. Arxins, m.A. (February 21, 1912.) 6d. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. SCIENTIFIC PROCEEDINGS—continued. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss rs. (Plates XVIL-XIX.) (March 26, 1912.) 1s. ‘ Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Hexry H. Dixon, sc.p., r.r.s., and W. R. G. Arxins, m.a., atc. (April 9 1912.) 6d. z Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Drxon, sc.D., F.B.8., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. Heterangium hibernicum, sp. Nov. : A Seed-bearing Heterangium from County Cork. By T. Jounson, p.sc., F.u.s. (Plates XX. and XXI.) 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On the Rotting of Potato Tubers by a new species of Phytophthora haying a method of Sexual Reproduction hitherto undescribed. By Guorce H. PrrHYBRIDGE, PH.D., B.Sc. (Plates XLIL—XLIV.) (March 26, 1913.) 2s. 6d. . On Pure Cultures of Phytophthora infestans De Bary, and the Development. of Oospores. By Grorcz H. PurnypripGE, PH.D., B.SC., and Paun A. Murpny, a.r.c.sct. (Plates XLV, XLVI.) (March 26, 1913.) 1s. 6d. DUBLIN! PRINTKD AT THE UNIVERSULY PRESS BY PONSONBY AND GIBBS. THE SCIENTIFIC PROCEEDINGS OF THE ROYAL DUBLIN SOCIETY. Vol. XIII. (N.S.), No. 37. } MARCH, 1913. INTER-ALTERNATIVE AS OPPOSED TO COUPLED MENDELIAN FACTORS: A SOLUTION OF THE AGOUTI-BLACK COLOUR IN RABBITS. BY JAMES WILSON, M.A., B.Sc., PROFESSOR OF AGRICULTURE IN THE ROYAL COLLEGE OF SCIENCE, DUBLIN. {Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBUIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. —— Price Sixpence. Roval Dublin Soctety. FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tur Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten Jays prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. ease XXXVII. INTER-ALTERNATIVE AS OPPOSED TO COUPLED MENDELIAN FACTORS: A SOLUTION OF THE AGOUTI- BLACK COLOUR IN RABBITS. By JAMES WILSON, M.A., BSc., Professor of Agriculture in the Royal College of Science, Dublin. [Read Frsruany 25. Published Marcu 27, 1913.] In the November number of the Journal of Genetics Professor Punnett deals with that portion of his experiments specially concerned with the agouti-black colour found in rabbits, and gives his solution of the problem. He finds three dominant factors in operation, and; as required by the “‘ presence and absence ” theory, their three “absences.” Then it has to be assumed that two of the three dominant factors are coupled. The purpose of the present paper is to bring forward another solution, in which neither coupling nor the “presence and absence” theory need be assumed—the only assumption necessary being that three of the five factors in the case are inter-alternatives: that is, that any one of three can mate with either of the other two in the same way as the red, black, and white colours found in cattle can mate any one with either of the other two, or as any one of the colours in horses can mate with any of the others. The colours in the case are agouti, black, yellow, tortoise, and agouti- black. The Himalayan parents used were apparently white, with black “points,” but they were really black rabbits lacking colour excepting on the parts covered by the “points,” for their progeny from whole-coloured rabbits were whole-coloured, and their peculiar markings were inherited by their grandchildren and other descendants in a way to show that they are recessive to whole colour. ‘The Himalayans were never sorted out and counted as regards their true colours, and these added to the other numbers. Usually, however, the other numbers were large enough without them. SCJENT. PROC., R.D.S,, VOL. XIII., NO. XXXVII. 4s 590 Scientific Proceedings, Royal Dublin Society. When ordinary F'1 agouti rabbits were mated with themselves, their progeny were agouti, black, yellow, and tortoise, in the ratio 9:3:3:1.1 This shows that there are at least two pairs of factors operating, and, representing them meantime by “ unknown” symbols, we can set down the colours and their factors thus :— Agouti. Black. Yellow. Tortoise. X X a x VY y 4 y 9 : 3 3 i 1 Agouti results with the concurrence of X and Y, black with X and y, yellow with x and Y, and tortoise with # and y. This finding is confirmed elsewhere in the experiments thus :— (1) When tortoise was mated with tortoise, tortoises only were produced.? (2) When heterozygous yellow was mated with tortoise, only yellows and tortoises were produced.* When heterozygous yellow was mated with itself, only yellows and tortoises were produced.’ : (3) When pure black (Himalayan) was mated with tortoise, the first crosses were all black,® and the second black and tortoise in the ratio 3: 1.° When pure black was mated with heterozygous yellow, blacks and agoutis were produced in the ratio 1 : 1.7 (4) When heterozygous black was mated with tortoise, blacks and tortoises were produced in the ratio 1: 1.8 When heterozygous black was mated with pure black, blacks only were produced.® But from one mating of black and heterozygous yellow there resulted a black male (No. 28), which bred in an extraordinary manner. Had his oh a pep should have thrown blacks and tortoises from ordinary F'1 blacks in the ratio 3:1; instead of which he threw agoutis, blacks, yellows, tortoises, and agouti-black—a new colour—in the ratio 1:4: 1:1:1,!° while, from tortoises, he should have thrown blacks and tortoises in the ratio 1 : 1: instead of which he threw, from a single doe, three blacks, one yellow, and two tortoises." From these results we can at once infer part of the constitution of this black rabbit. Since he threw tortoises from ordinary /'1 black and tortoise, constitution been what is usually expected from such parents, viz. 1 Journal of Genetics, vol. ii, 1912, p. 224. 2 Ibid. p. 228. 3 Ibid. p. 223. 4 Ibid. pp. 223 and 229. 5 Ibid. p. 223. © Ibid. p. 224. 7 [bid. p. 223. 8 Ibid, p. 224. ® Tbid. p. 224. 10 Tbid. p, 226. 1! Tbid. p, 234. Witson—Agouti-black Colour in Rabbits. 591 he contained both # and y; and, since he threw agoutis and yellows from ordinary /'1 black, he also contained Y. So far, therefore, his constitution — 2. was yy As to the remainder, there are two alternatives—(1) That, in X’s usual place, he carried another factor, say X’, which had the effect of making him black in spite of the presence of Y; and (2) that, in addition to X and its recessive, he carried this new factor X’ and its recessive. In the former case his constitution was a ; In the latter Ya. The first of these hypotheses Vy involves the assumption that x can have more than one alternative, the latter that the rabbits to which the new factor was introduced were already carrying its recessive x’ homozygously. Consider meantime the first of these hypotheses, viz., that the constitution of No. 28 was “A “ He was the progeny of a black Himalayan dam and a heterozygous yellow sire. An agouti was produced at the same mating. The constitutions of such parents are ordinarily ay and Fy The new factor ” must have come to No. 28 from his dam, because, had his sire carried it, he could not have been yellow, and since the dam produced an agouti at the same mating, she must also have carried 1, and her constitution yy We have now to find whether our hypothetical constitution for No. 28, eXeET, ? Vy’ shall discover the constitution of agouti-black. No. 28 was mated with two different constitutions, viz., 7 y (bortoise) and ae (F1 black). With the so far as the present question is concerned was therefore viz. is in accordance with experimental results; and, in doing so, we former he should have produced four different constitutions; with the latter eight. With the former the progeny should have split into two groups as regards the Xes, and these again each into two more as regards the Ys; while with the latter the progeny should have split into four groups as regards the Yes, and these again each into two more as regards the Ys. Let us write down thetwo sets of constitutions so produced with their correspond- ing colours. We shall find two constitutions not met with so far, viz., yy y and - op and we have no difficulty in inferring that the latter is that of a black rabbit, for, since X’ can make No. 28, which contains Y, black, much 1 Journal of Genetics, vol. ii, p. 225. 482 592 Scientific Proceedings, Royal Dublin Society. more can it make yi corresponding to the other new constitution. No. 28 mated with tortoise should give a ‘ black. As yet we have no means of naming the colour Niles XC @ Bite Le Vy YY Vey) yy black. black. yellow. tortoise. No. 28 mated with #1 black should give xX’ X XC IG X' x X’ x iG xX “a x ow Vy yy Vy yy Vy yy Vy yy black. black. black. agouti. black. yellow. tortoise. Thus, from the first of these matings there should result blacks, yellows, and tortoises in the ratio 2: 1:1, while from the latter there should result an unknown colour, agoutis, blacks, yellows, and tortoises in the ratio 1:1:4:1:1. These expectations are in accordance with the experimental Yesults. It is true there was only one mating of No. 28 and tortoise, from which the progeny were 3 black, 1 yellow, and 2 tortoise—small in numbers, though of the kinds expected—but there were 21 matings with #1 black, and the progeny were agouti-black 34, agouti 36, black 113, yellow 28, and tortoise 30; that is, these colours in the ratio 1:1:4:1: 1 approximately. The other colours being all in accordance with expectation, it is now a fair inference that the unknown colour is agouti-black, and that its constitution is me = Let us proceed upon this hypothesis. To prove it we shall have to prove that the constitutions depending upon it are accompanied in the experiments by the colours they ought to bear; and, since only constitutions containing X’ are involved, we may for convenience set down all those into which this factor can enter together with their corresponding colours. We shall have to assume meantime that x * is also agouti-black. This assumption is justified on the ground that Y acts similarly, whether homozygous or heterozygous. The constitutions in question are XX GX OX GTP AON X'X X'X NOR Cp Na. Ke FV EY SUH IY Wey WY YO Vo My Black. Black. Black. Agouti-black. Agouti-black. Black. Black. Black. Black, Witson—Agouti-black Colour in Rabbits. 593 If these ‘combinations were all bred and identified, a number of crucial experiments could be made. If the two groups homozygous for two factors were mated with pure agouti, the progeny would all be agouti-black ; and if the five groups heterozygous for one pair were mated with pure agouti or pure ordinary black—with agouti when the group contained y y, and with black when it contained Y Y or Y y—half the progeny would be agouti-black, while the other half would be black in one case and agouti in four. But Professor Punnett’s experiments were necessarily confined to such groups as appeared early among the descendants of No. 28’s dam, namely, to the two groups heterozygous for two pairs of factors, i.e. r (No. 28) and oe (the first agouti-blacks). The experiments with the second group were the more satisfactory; and we shall consider them first. a a agouti-black, was mated with three different kinds: (1) with itself, (2) with heterozygous yellow, and (3) with tortoise. Mated with itself, the progeny should split into three groups so far as the Jes are concerned, viz., XX’, X’X, and XX, and the middle group should be as numerous as the other two together. Hach of these should split again in a similar manner as regards the Ys. Thus there should be nine groups in all, which we shall set down in tabular form so as to show their constitutions, the expected colours, and the relative number of individuals expected in each. Constitutions. Expected colours. Relative numbers expected, XO IE WE IY black 1 X'’X' Vy black 2 XOX OY) black 1 XE IX ME IY agouti-black 2 XIX Vy agouti-black zt xX’ Xyy black 2 XGXa aa agouti 1 XX Vy agouti 2 XXyy black 1 Thus there ought to be 7 blacks: 6 agouti-blacks: 3 agoutis. The expectation is in accordance with the experimental results.’ Mated with heterozygous yellow, Toy the progeny of - e should split 1 Journal of Genetics, vol. ii, p. 231. 594 Scientific Proceedings, Royal Dublin Society. into two groups as regards the Jes, and these again into two others as regards the Ys, thus :— Constitutions. Expected colours. Relative numbers expected. XO BIT VC black 1 Xa Vy black 2 Xexyy black 1 pXGra YGoYa agouti 1 DCB agouti 2 Kuy y black il Thus there should be 5 blacks: 3 agoutis. he expectation is again in accordance with the experimental results.' Mated with tortoise, te the progeny of = ze should split into two groups as regards the Xes, and these again into two others as regards the Ys, thus :— Constitutions. Expected colours. Relative numbers expected. XG evan black 1 xXinyy black 1 Xa Vy agouti 1 Xayy black 1 Thus there ought to be 3 blacks: 1 agouti. Again, the expectations are in accordance with the experimental results.” It will be well to set down these three experiments in tabular form, so as to compare the expected with the actual results :— Results of mating agouti-black with :— (1) Agouti-black.? (2) Heterozygous-yellow.* (3) Tortoise.’ s} g oo ca‘ “‘ ee) = Relative Wetaal Relative Weewal Relative Netual numbers = ererilis numbers eee numbers Seaciye expected. r expected. . expected. 2 Agouti 3 39 3 33 1 15 Black 7 107 5 69 3 51 Agouti-black 6 74 — — — — As already mentioned, the results got by mating the other group heterozygous for two pairs of factors, 2) (like No. 28), are less satisfactory, for the reasons that this group was not always clearly distinguished from its 1 Journal of Genetics, vol. ii, p. 282. * bid. p. 232. * Ibid. p. 281. 4 Ibid. p. 282. © Ibid. p. 282. Witson—Agouti-black Colour in Rabbits. 595 neighbour black groups, that the total number of matings was small, and that the true colours of the Himalayans were not identified and counted—an important matter when the numbers are small. Yet a fair comparison can be made between the expected and the experimental results. Since the group = j was not clearly separated from its black neighbours, we must see which other groups were mated alongside it. When the other heterozygous group agouti-black, was mated with heterozygous yellow, blacks and agoutis were produced in the ratio 5:3. The blacks so produced XO IC UES IGG JI WO DP produced in this way was mated with chocolate,? whose constitution so far as were , in the proportion 1:2:1:1.1 A set of blacks this experiment is concerned is ee should produce agoutis and agouti-blacks in equal proportions, the second From this mating the first group, ae yy —which is the other group heterozygous for two pairs of factors—should produce blacks, agoutis, and agouti-blacks in the ratio 2:1: 1; the last two groups should produce blacks only; and the relative proportions of the parents producing progeny in these three groupings should be 1:2:2. The experimental results are® :— Numbers of Parents. Progeny Produced. Black. Agouti. Agouti-black. 3 — 13 9? 4 12 3 3 6 47 — == Thus, although x j was not separated from its neighbours in this mating, the experimental results are approximately as they should have been had = and its neighbours been bred in the usual way and produced in the usual proportion. But another mating was made with a similar set of blacks, excepting that ~ those capable of producing blacks only from chocolate were eliminated. The groups mated were, therefore, ae and ae and the numbers in the former should have been to those in the latter in the ratio 1:2. They were mated with heterozygous yellow. The former group should have produced ! See top of previous page, ? Journal of Genetics, vol. ii, p. 283. 3 Ibid. p. 233. 596 Scientific Proceedings, Royal Dublin Society. blacks and yellows in equal numbers, the latter blacks, yellows, and tortoises in the ratio 2:1:1. The experimental results are! :— Numbers of Parents. | Progeny produced. oO Black. Yellow. Tortoise. 3 5 8 ao 4 10 8 7 The experiments are again in close accordance with the expected results. These same two black groups were also mated with tortoise and orange (whose constitution as regards this experiment is rvyy). From this mating only yellows and tortoises should result. It happened so in the experiments.? The figures for each kind are not given. Thus our hypothesis that the constitution of No. 28 is yy has been tested six times—three by agouti-black matings and three by matings with what have been called agouti-bearing blacks; and, since at every test the hypothetical and the experimental results have been in accordance, it may reasonably be claimed that the hypothesis is sound. It follows, of course, If further x that the constitution of the original agouti-blacks is % ri experiments were thought necessary, the following might be suggested :— AW AE : 5 eC (a) If i ; were mated with pure agouti, rae the progeny should all be agouti-blacks, i.e. wa (b) If fae = were mated with pure black, ae “, the progeny again should all be agouti-blacks. _ (c) If, however, these two blacks homozygous for 1 and y on the one e hand, and for X’ and Y on the other, have not yet been found, the agouti-black which is homozygous for Y (X’'X YJ) and has been found® should be mated with itself. he progeny should be 1 black : 2 agouti-black : 1 agouti,, -£ y vs < VGve that is, 1 ae if 9 2 a ie il as The constitutions of the blacks and agouti-blacks could be tested readily. The suggestion may now be permitted that it is next to impossible to identify the functions of the factors operating in this case. ‘The functions of the two recessives cannot be named. When they concur, tortoise is produced, but other factors may be operating at the same time. Even if not, the effects of w and y could not be told, since they cannot be separated. Nor can much 1 Journal of Genetics, vol. ii, p. 233. 2 Ibid. p. 284. 3 That is the first group in table ix, Journal of Genetics, vol. ii, p. 233. Witson—A gouti-black Colour in Rabbits. O97 more be said with regard to X’, X, and Y. It might be suggested that X’ and X have each a blackening effect, and that Y has a lightening or yellowing ; but if the blackening effect of X’ produces a black rabbit when concurrent with the yellowing effect of Y, why does the further addition of the blackening effect of X make the previously black rabbit lighter or yellower? Hvery suggestion thought of is met with this anomaly in one form or another ; and eventually appeal may have to be made to the physiological chemist. Our solution being thus presumably sound, we must now consider how it differs from Professor Punnett’s. His assumption is that there are three dominant factors and their ‘‘ absences” operating in the case, and that one called D cannot enter a gamete unless accompanied by another called £. His hypothesis is as follows :— “Tn the set of experiments into which ¢ 28 and his descendants enter we are dealing essentially with three separate factors : “ 4, the ‘agouti’ factor which turns black into agouti, and tortoise into yellow. “ #,a factor for the extension of the melanic pigment which turns yellow into agouti and tortoise into black. “ D, a factor of which the effect is to produce a deepening in the melanic pigment. “The effect produced by D depends (1) upon whether this factor is present in a homozygous or in a heterozygous condition, and (2) upon whether the animal is homozygous or heterozygous for #. The addition of one dose of D to an agouti which is homozygous for # turns it into an agouti-black, while the addition of a second dose results in a full black. If however the agouti is heterozygous for #, the addition of either one or two doses of D produces the same visible effect, viz., a full black. The presence of Din a black makes no difference to the appearance of the animal.”? With regard to this hypothesis two remarks may he made. According to it, the following constitutions correspond to the colours set down above them :— Agouti-black. Full black. Full black. Full black. AA or Aa AA or Aa AA or Aa AA or Aa EE EE Ee Ee Dd DD Dd DD The first remark is that this solution also meets with the anomaly met with in the new solution when considering whether the functions of the 1 Journal or Genetics, vol ii, p. 227. SCIENT. PROG. R.D.S., VOL. XIII., NO. XXXVII. 417 598 Scientific Proceedings, Royal Dublin Society. factors could be defined ; for if # be an extension of the melanic pigment, and D a deepening, why should the first of the above constitutions, with a double dose of E, be only agouti-black, while the third, with only a single dose, is full black ? The second remark is: If the factors D and # are coupled—that is, if D cannot enter a gamete unless accompanied by H—how is the second dose of D to enter a constitution heterozygous for # ? We can compare the two assumptions if we set down side by side all the possible coustitutions containing 1” on the one hand, and the corresponding constitutions containing D coupled with # on the other; and we can make the comparison clearer by surrounding the coupled factors with parallel lines, thus :— BX XIN a PAU EN) AAG BOI BE XO AEB ROD OK SD la ap nt asl AN ORC) due ah TL UT he Vie Yay a [Dd Da [D| Die ID| iD a EB /E\|E| |z| E lnc Bike Aa aa AA Aa aa AA Aa aa a black. black. agouti-black. agouti-black. black. black. black, black. On examining the above scheme we see that, since the coupled factors act really as a single factor, the most essential difference between the two assumptions is that one requires two recessives while the other requires three. If it could be determined whether there are two or three recessives operating in the case, it would be determined at the same time which of the two assumptions is the more reasonable. But the question as to how the colours dealt with so far and several others not yet mentioned are constituted can be carried still farther from information supplied by Professor Punnett when he compares what he calls the &lack series—the one so far dealt with here—with another series which he calls the chocolate. When considering the difficulty of identifying the functions of the several factors, we pointed out that other factors might be operating at the same time. And this is really the case. Professor Punnett’s tabular comparison of the two series shows that there is a factor “for black” in agouti, black, yellow, and tortoise, while its recessive isin the chocolate series, i.e. in cinnamon, chocolate, dilute cinnamon, and orange. He symbolizes these factors by B and 0; but, since it is safer to use “ unknown ” symbols, we shall call them Zand s. ‘These factors—1’ being inoperative—and the colours to which they belong now combine to form a set in which there are three pairs of factors operating and eight colours produced. ‘We shall set down first of all the names given to the colours by Witson—Agouti-black Colour in Rabbits. 599 Professor Punnett, but as Z and s show themselves apparently to bring about densing and diluting, we shall suggest that the name dilute cinnamon be changed to dilute yellow. Constitutions. Names already given. Names suggested. Black Series. Koren Sonics XXYVVZZ agouti. agouti. AAC IEW 8 8 cinnamon. cinnamon, i.e. dilute agouti. AX yyZZ black. black. x «xYYVZZ_ yellow. yellow. “x «exyyZZ tortoise. tortoise. GB ewig & dilute cinnamon. dilute yellow. AXy y 2 8 chocolate. chocolate, i.e. dilute black. LLY YS s orange. orange, ie. dilute tortoise. We may now set down the constitutions and the colours resulting from the introduction of XY’. We need do this for the heterozygous form only, since, when 1’ is homozygous in a constitution, the colour is black. Constitutions. Colours. X’X VY ZZ agouti-black. X’XYYVee dilute agouti-black. X’X y yZZ_ biack. AC MMW GG ‘EXD X’xy yZZ diack. Non Vo Ves) 3) black. xX’Xy ys s black. X' a y y 2 3 black. Thus, since there are at least seven factors carried by the experimental rabbits, the decision as to whether the assumption of coupling or that of a factor having more than one alternative is the more reasonable depends upon finding whether there are four or three recessives operating in the foregoing series of colours when YX’ is included. The writer’s attention was drawn to this case by his colleague Dr. F. E. Hackett, with whom he has had the advantage of discussing it on more than one occasion. 1. 16, 17. SCIENTIFIC: PROCEEDINGS. VOLUME XIII. 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FENTON (Rio Gatiecos, ARGENTINA). [ COMMUNICATED BY PROFESSOR GRENVILLE A. J. COLE, M.R.1.A., F.G.S. | (PLATE XLVII.) [Authors alone are responsible for all opinions expressed in their Communications. } DUBLIN: PUBLISHED BY THE ROYAL DUBLIN SOCIETY, LEINSTER HOUSE, DUBLIN. WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price Sixpence. 18 vLo — Acoma Institoy~ =) a Koval Wublin Zociety. eee FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tue Scientific Meetings of the Society are held alternately at 4.30 p.m. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Editor. Witson—Agouti-black Colour in Rabbits. 599 Professor Punnett, but as Z and s show themselves apparently to bring about densing and diluting, we shall suggest that the name dilute cinnamon be changed to dilute yellow. Constitutions. Names already given. Names suggested. Black Series. Koren Series. AXXVVZZ agouti. agouti. ACAE YS cinnamon. cinnamon, ie. dilute agouti. XX yy ZZ black. black. 2xYVZZ yellow. yellow. zx exyyZZ_ tortoise. tortoise. OW WB B dilute cinnamon. dilute yellow. AXy y 2s chocolate. chocolate, i.e. dilute black. “2nY Ys 8 orange. orange, i.e. dilute tortoise. We may now set down the constitutions and the colours resulting from the introduction of X’. We need do this for the heterozygous form only, since, when 4” is homozygous in a constitution, the colour is black. Constitutions. Colours. A’X VY ZZ _ agouti-black. X’XVYVss dilute agouti-black. X’XyyZZ diack. X’x YVZZ black. A’'xy yZZ black. X’x VV 3-2 Diack. A’ Xy ys 3 black. AX’x2x y y 3s black. Thus, since there are at least seven factors carried by the experimental rabbits, the decision as to whether the assumption of coupling or that of a factor having more than one alternative is the more reasonable depends upon finding whether there are four or three recessives operating in the foregoing series of colours when 4” is included. The writer’s attention was drawn to this case by his colleague Dr. F. E. Hackett, with whom he has had the advantage of discussing it on more thar one occasion. SCIENT, PROC. R.D.S., VOL. XIII., NO. XXXVII. 4u [ 600 ] XXX VIII. NOTES ON RECENT PAMPA AND OTHER FORMATIONS IN PATAGONIA. By E. G. FENTON (Rio Gallegos, Argentina). [ COMMUNICATED BY PROFESSOR GRENVILLE A. J. COLE, M.R.I.A., F.G.S. ] (Prarze XLVIL.) [Read Ferruany 25. Published May 15, 1913.] On the plains of southern Patagonia, between the chain of the “ Cordillera ” (tail of the Andes) and the Atlantic Ocean, there are to be found many points of great interest to the geologist, especially with regard to the late Tertiary and Quaternary formations. The present paper is an amplification of various notes taken by the writer during the many journeys which he has made through the district of Rio Gallegos, Argentine Republic, in the course of five years of medical practice. It is hoped that they may usefully supplement the work already done on glacial phenomena in 8. America,! since the conclusions are the result of independent observations in the field. To the westward, west by south, and west by north of the town of Gallegos, there is a large district of over 100 miles in extent, in which the pampa is more or less buried under vast sheets of basaltic lava, the latter rising here and there extensively over the plains to form cones and craters. The basalt in many places exhibits such a rugged and serrated appearance, aud shows such little weathering, that one would, on superficial examination, be inclined to think that it was not more than a century or two old; yet, as will be seen in the sequel, it must have been poured out at a very remote period, so far as the history of the human race is concerned. The next feature of interest on going over the “pampas” is the number of deep-river beds and cafiadones which are met with. ‘The river-beds vary in breadth from half a mile to perhaps three miles, and have been cut down below the level of the surrounding pampas to depths varying from a few hundred to over a thousand feet. ‘he sides of these river-valleys are more 1 See, for instance, G. Steinmann, “ Uber Diluyium in Siid-Amerika,’’ Monatsber. deutsch. geol, Gesell., 1906, Nr. 8/10, Frnron—Lecent Pampa and other Formations in Patagonia. 601 or less abrupt; and the land rises to the level of the pampas, often in a series of well-marked terraces. From the top of the last terrace on one side to the corresponding one on the opposite side is in some places as much as fifteen to twenty miles in extent; in others it is not more than one to two miles. In Plate XLVII, fig. 1, which represents the middle reaches of the Gallegos River, it will be noticed that the action which operated in cutting out these river-valleys and cafiadones was not only capable of wearing down the ordinary pampa formation, which consists to a large extent of shingle and clay, but was capable also of cutting its way through considerable thicknesses of hard basalt. In this photograph the telegraph posts are seen standing in the bed of the river-valley, which in the place shown is upwards of two miles wide. A is the opposite bank lower down where the river-valley curves round to the right: it is a table of basalt lyimg on pampa formation, and is about 400 feet above the river. JB is part of a volcanic cone, the side of which has been cut away and swept clean, leaving practically no fragments; it is better seen in fig. 2. It abuts directly on to the river-valley, where its continuity ends abruptly, and it shows all the evidences of comparatively recent activity, so far as the serrated summit is concerned; yet the sides and base show that some considerable action took place at no very distant date which caused them to be swept so clean. It is impossible to conceive that when the river was already in its present position, a great outburst of volcanic activity could have occurred without pouring a huge sheet of lava down the river-valley. No such lava-sheet, however, exists; while, on the other hand, the rich soil of the valley extends right to the base of this cone; it is to be presumed, therefore, that the valley has been cut down since the outpouring of the lava. In point C the phenomena are more striking than in point B, for here we have a gigantic table of supra-pampean basalt upwards of 1000 feet high, rising abruptly and steeply from the level valley below, and terminating at the top in a sheer precipice of about 300 feet of solid volcanic rock. Under point D in fig. 1 is a deep caiiadon or gorge, down which a small river known as the Gallegos Chico runs. This cafiadon is a narrow deep cutting, the sides of which are more or less precipitous: it runs between tables C and H, which are overlain by supra-pampean basalt. From its appearance the basalt would seem to have been continuous at one time over D. Tables C and E extend up to over 1000 feet at the back, so that the action which cut down the Gallegos Chico gorge through hundreds of feet of solid basalt, almost as hard as iron, must have been a very considerable one, especially when we note that this all probably took place since Middle Quaternary times. Not only here, but right through this part of Patagonia, are to be found 4u2 602 Scientifie Proceedings, Royal Dublin Society. abundant deep cafiadones and river-valleys, the sides of which are steep and crowned with sheer cliffs of basalt. In fact, in every place there is evidence of powerful erosion having taken place during comparatively recent times, so far as geological history is concerned. Now, on going down these rivers and cafiadones one very pregnant fact is noticed, that is, that no basaltic boulders of any considerable size are found to have travelled far from the parent tables. In fact, when one goes more than two or three miles, one never comes across a piece of basalt larger than can be lifted in one hand. This fact would lead one to believe that whatever action cut down these cafiadones, &c., it was not a large glacial one. If there was any glacial action, as I hope presently to show, it was of a mild kind, which, although it may have had some cutting power, had no very great transporting influence. The accompanying figure represents the River Gallegos a little further down. SS oe 8 tf = eet” Toa ee Denudation of volcanic masses in the Rio Gallegos Valley. [From a photograph by the author.} Point A is the remains of a volcanic cone which has been cut down in the middle, and falls sheer into the river. B is the river-valley, and point C is a volcanic table consisting of basaltic rock, poured out in the first instance probably by A, with which it was originally continuous. The gap between A and C is about half a mile, and the summit of A would be about 800 feet above the river. The volcanic table C is more or less elliptical in shape; looking at it from above, it is cut clean down sharply on both sides, and is bounded on the Funton—Recent Pampa and other Formations in Patagonia. 603 northern side by the Gallegos River, and on the southern by a cafiadon (D), known as the Cafiadon of the Buitreras, which is about a quarter of a mile broad, and which separates C from a high basaltic table H, extending away indefinitely to the south. It was on the floor of this cafiadon, bounding the south side by table C, that the writer first came across typically striated stones, showing that ice-action had been at work. The striated stones were large fragments of basaltic rock up to a yard or more in length; they lay on the bottom of the cafiadon D, and exhibited well-marked striation, all the striz running parallel with the line of the cafiadon. Nothing of the nature of terminal moraines could be seen at the outlet of this cafiadon, which appears extraordinary, unless they have long since been buried under recent pampa dust. Now, although, as we have said, there are not terminal moraines opposite the end of cafiadon D in Plate XLVIL, fig. 3, nor in fact in any place between that and the mouth of the Gallegos River, some forty miles away, yet there are numerous large erratic boulders to be found in certain parts of the pampas. On leaving the lower reaches of the River Gallegos, and travelling to the south over the pampas in the direction of the straits of Magellan, when one has gone about ten miles on the road, large solitary stones begin to appear, some of these weighing many tons, and all of them lying right on the surface of the pampa. They are not basaltic, but more of a granitic or schistose nature, and are, as a rule, well rounded, showing that they have been exposed to the weather for long periods ; they seem to extend indefinitely towards the south. Right through the region where these large erratics are found there are numerous traces of volcanic outbursts, such as are seen in Plate XLVII, fig. 3, which shows a lava-flow over the surface of the pampa, coming from a crater at the back. Now, no basaltic erratics are found in any portion of the pampa, which shows that the volcanic outbursts must have occurred since the period when the large erratics were transported to their present positions. ‘These erratics, as I have said, are found all the way down to the Straits of Magellan ; they are not found to the north of the lower reaches of the Gallegos River, nor do they reach that river near its mouth. On the other hand, when one goes further west about seventy miles, these same large erratics are found across the river to the north, and on the highest summits of the pampas and hills, and even reach as far north as the upper portion of the River Coyle. These erratics are also found congregated in numbers in the valley of the River Gallegos further to the west, and down to seventy miles from the mouth, and give the appearance of having been brought together there by ice; but it is more likely that they simply rolled into their present position in the valley from the high pampas on either side as the valley was cut down, since 604 Scientific Proceedings, Royal Dublin Society. they are found on the sides and summits of the hills on either side up to over 1000 feet above the sea-level, just as well as in the valley, except that in the latter situation they are congregated more closely. Tn all the parts of the country visited by the writer, to the north of a line presently to be mentioned, no large erratics are found on the surface of the pampa, although there are abundant outpourings of volcanic matter right away to the north of the Santa Cruz River. On drawing a line through southern Patagonia on the Argentine side, from a point on the Atlantic coast about twelve miles north of the 52nd parallel of latitude, due west to a point about twelve miles to the eastward of the 71st meridian west of Greenwich, and then curving slightly to the northward, one would more or less mark the northern limit of the large erratic boulders. Boulders are found to the north of this line, but they are all small and more or less rounded. Now, from the facts before us the writer would suggest that we have evidence of two post-pampean Ice Periods in southern Patagonia—one large or general and one small or local. The large or general occurred first and was part of a huge glaciation extending from the south or south-west. It occurred after the pampas were formed, since we find everywhere the huge boulders lying on the surface. Its northern range was limited by the line which I have mentioned, and it may have been an extension to the north of the great Antarctic Ice Barrier, carrying boulders with it from the continent that lies around the south polar regions. These boulders may also have been carried by floating ice, but this hypothesis would necessitate great sub- mergence, as some of the boulders which the writer has seen are as large as a small house, and must weigh almost hundreds of tons, and the icebergs which carried them would have had to be of colossal dimensions. Moreover, another point is that the largest boulders are often found on the highest portions of the pampa, in places up to two thousand feet above the sea-level. Accepting the hypothesis of a great Ice Period, we come to the question of its time, and the writer suggests that it was probably of late Pliocene or early Pleistocene Age, his reason being as follows:—Mr. J. B. Hatcher has pointed out that there is a gradual dip from north to south in the formations of southern Patagonia along the east or Atlantic border. Now, about Cape Fairweather is a considerably worn marine formation which would seem to be of Pliocene origin, as it les unconformably on the Santa Cruz formation, which is terrestrial, and has been provisionally classed as Miocene. This would place the Pampa formation to the south, the dip still continuing, either in late Pliocene or Pleistocene, and it is on the surface of this formation that the great boulders are found. Frnton—Recent Pampa and other Formations in Pacagonia. 605 When the great ice-sheet had receded and the climate had assumed a milder type, there occurred a prolonged period of great volcanic activity, and there were in places several outpourings having considerable periods between them. There are in some places hundreds of feet of accumulated debris between the successive sheets of basalt, and also in some places the basalt has a much more aged and worn appearance than in others. Hence the out- pourings probably lasted for many thousands of years. Then occurred a period of slow upheaval, more marked towards the west, with great accumu- lation of snow and ice on the high ground, melting, however, as it reached the plains and forming large and rapid rivers with considerable eroding power. In some places small glaciers descended into the river valleys for a certain distance, as is shown by the occurrence of the striated basalt boulders mentioned on p. 603; but none of them reached as far as the Atlantic coast. The ice action in this case was small and limited: it extended from the high lands to the west towards the Atlantic, it was purely local, and was probably not part of a general Ice Period. This condition must have lasted for a very long time, if we estimate it in thousands of years, as we have seen that it was sufficient to cut a river-valley two miles wide through hundreds of feet of hard basalt and upwards of a thousand feet of Pampa formation. In turn there followed a period of subsidence and quiescence, when the snow re- ceded to the tops of the mountains and the pampas were left bare and dry. The subsidence continued until a good part of the southern pampas of the continent were under the sea, but only for a short while, after which elevation began again, and is still going on. As evidence of recent subsidence under the sea a number of salt lakes are found all over the pampas, and a consider- able amount of salt is found in the soil everywhere on the surface. It is well known that where water stands for any length of time in superficial wells it becomes perceptibly salt. Recent sea-shells have also been found in the bed of some of the cafiadones to a height of hundreds of feet above the sea-level. In the Gallegos River, slightly above the town, the bed-rock of the surrounding Santa Cruz formation appears on the surface over extensive areas at low water, washed and swept clean of mud. Now, if the river-bed were sinking, we should expect to find nothing but mud, sand, and shingle all over from side to side; but if it were rising, we should expect to find such mud and shingle in most places swept off to sea, and the rock becoming eroded away. ‘he latter is exactly what is found. Also, the small island in San Julian Bay, where Drake was supposed to have executed some of his mutineers about 300 years ago, which was then only a few feet above sea- level, is still at about the same level, notwithstanding the constant planing down action it is subjected to by the strong winds which blow there, These 606 Scientific Proceedings, Royal Dublin Society. and many other facts go to show that there is a slow upheaval going on at present. So then, to sum up, we have evidence in the region we are dealing with of a sequence of events as follows during late Tertiary and Quaternary times :— 1. A period, probably late Pliocene, when the superficial pampa deposits were formed. These deposits consist to a large extent of fine shingle, clays, and sands, and the climate of the period must have been of a nature unfavourable to life, as the writer has never known of any fossils, either marine or terrestrial, having been found in the superficial pampas of the district in question. 2. A period of great glaciation, when an ice-sheet came from the south or south-west, carrying large granite boulders, and depositing them on the surface of the aforementioned pampa formation, even on the tops of the highest hills. 3. Recession of the ice-sheet and outburst of volcanic activity ; large lava sheets were poured cut; periods of quiescence and subsequent outpourings lasted a long time. 4. Period of elevation with local minor glaciation; extension of ice and snow down from the Cordillera in the west into the plains; considerable erosion of basaltic and pampean formations. 5. Period of subsidence for a short time; the sea encroached on lower pampas. 6. A period of elevation, which is still going on. Now all these subsidences and elevations must have been very gradual, and must have extended over prolonged periods, since in all the formations observed by the writer in this district, even right up to the outpourings of lava, the strata exhibit wonderfully even horizontality, and show practically no evidence of curving or distortion. This evenness is as well marked in the Santa Cruz formation, which is supposed to be of Miocene age, as in the most recent rocks. ‘To conclude, I would suggest that the evidence which I have brought forward tends to prove that the great or general Ice Period which deposited the large erratic boulders on the top of the pampa must have occurred at a very remote period, probably many hundreds of thousands of years ago. 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WILLIAMS AND NORGATE, 14, HENRIETTA STREET, COVENT GARDEN, LONDON, W.C. 1913. Price One Shilling and Sixpence. Koval Dublin Society. SOO ® FOUNDED, A.D. 1731. INCORPORATED, 1749. EVENING SCIENTIFIC MEETINGS. Tue Scientific Meetings of the Society are held alternately at 4.30 pem. and 8 p.m. on the third Tuesday of every month of the Session (November to June). Authors desiring to read Papers before the Society are requested to forward their Communications to the Registrar of the Royal Dublin Society at least ten days prior to each Meeting, as no Paper can be set down for reading until examined and approved by the Science Committee. The copyright of Papers read becomes the property of the Society, and such as are considered suitable for the purpose will be printed with the least possible delay. Authors are requested to hand in their MS. and necessary Illustrations in a complete form, and ready for transmission of the Kditor. G07. XX XIX. ON THE INFLUENCE OF SELF-INDUCTION ON THE SPARK SPECTRA OF CERTAIN NON-METALLIC ELEMENTS. By GENEVIEVE V. MORROW, A.R.C.Sc.1. [COMMUNICATED BY JAMES H. POLLOK, D.sC.] (PLates XLVIIL-LL.) [Read June 25, 1912.! Published May 19, 1913.] Tuer spark spectra of the metallic elements have been obtained under a great variety of conditions, and the wave-lengths of the ultimate lines have been determined with accuracy; but we have not a suflicient knowledge of the lines that arise from the non-metallic elements when small quantities of these are present in the atmosphere surrounding the electrodes at the time of sparking, and for analytical purposes it is very important that this should be known. In sparking substances it is sometimes desirable to use a self-induction coil and sometimes not, so that it is important to know also the effect of self-induction on the development of the lines due to the substance present in the atmosphere surrounding the electrodes. ' Tn the present investigation I have endeavoured to obtain the spectra of some of these elements under atmospheric pressure, and whilst so doing have studied the changes caused by introducing a self-induction coil into the secondary circuit. The effect caused on the spark spectra of the metallic elements by introducing a self-induction coil into the secondary circuit was first studied by Schuster and Hemsalech,? and they found that self-induction removed the air-lines from spectra. Their explanation of this phenomenon was that the air-lines were caused by the initial discharge when the spark-gap contained no metallic vapour. Subsequently the discharge passed through the vapourized metal which had diffused away from the electrodes. On inserting the self-induction coil the discharge passed more slowly, the air did not become sufficiently heated to yield its spectrum, and the discharge 1 The publication of this paper was unayoidably postponed.—J. H. P. 2 Phil. Trans. Roy. Soc., 1900, vol. cxciii., Ser. A., p. 189. SCIENT. PROC, R.D.S., VOL. XI, NO. XXXIX. 4x 608 Scientific Proceedings, Royal Dublin Society. was carried across by the vapourized metal. Schenk’ investigated the appearance of the spark by a rapidly rotating mirror. The first discharge showed a brilliant white line on the mirror followed by a few weaker ones. The lines, which were seen to be curved, Schenk showed to be due to metallic vapour and the first brilliant white flash was proved to be due to the air. This white line did not show in the mirror when the self-induction coil was in the circuit. The apparatus used in the present investigation consisted of a spectrograph, designed by Sir Walter N. Hartley,? an App’s coil, condenser, and a Hemsalech self-induction coil, all of which are described in my paper on “The ultimate lines of the vacuum-tube spectra of manganese, lead, copper, and lithium.”® In order to obtain the spectra of the gaseous non-metallic elements, a small quartz tube was used (fig. 1, Plate XLVIII) fitted with rubber corks through which passed glass tubes enclosing platinum connexions, sealed into the glass with blue enamel in the usual manner, and to these were attached the electrodes, the spark-gap being usually about a quarter of an inch. The electrodes used were either of gold or carbon, the carbon electrodes being cut from a piece of Acheson graphite. The electrodes were first sparked in air with the condenser and Hemsalech self-induction coil in circuit, and the spectrum so obtained photographed. Then the gas whose spectrum was required was passed through the tube, having been thoroughly purified and dried, and a photograph of the spectrum taken with the condenser and Hemsalech coil in circuit. The current of gas was passed continuously through the tube, so that the products which might be formed by combination with the electrodes would be swept away. Another photograph was then taken of the spectrum of the gas without self-induction. ‘Thus there were obtained three photographs with each pair of electrodes, 7.e.— (a) Gold electrodes in air with self-induction, (OD) = 5 in the gas with self-induction, Ore 4 in the gas without self-induction. (a) Carbon electrodes in air with self-induction, @) 6 5 in the gas with self-induction, (c) a " in the gas without self-induction ; so that on each photographic plate there were six photographs, three with each pair of electrodes. This arrangement of the photographs was very 1 Astrophys. Journ., 1901, vol. xiv., p. 116. 2 Scient. Trans. Roy. Dub. Soc., 1882, vol. i., pp. 231-238. See also Scient. Proc. Roy. Dub. Soe., vol. iii., 1881, p. 93. 3 Scient. Proc. Roy. Dub. Soc., 1912, vol. xiii., pp. 269-287. Morrow— On the Influence of Self-Induction, §c. 609 convenient for comparing the effects produced by the different electrodes, and for observing by inspection which lines were due to the gaseous element. In order to obtain the spectra of the non-metallic elements which are liquid or solid at ordinary temperature, a small quartz flask was used as shown in fig. 2, Plate XLVIII. A wide glass tube passed through a rubber cork in the mouth of the flask, and through it the platinum connexions entered insulated by glass capillary tubing, and these were passed through the wide tube in the rubber cork and held in position by a plug of cotton wool or asbestos. As before, a photograph was taken of the electrodes in air. Then the substance whose spectrum was required was put into the flask, and vapourized by heating it with a Bunsen flame, taking care that nothing condensed on the side of the quartz bulb which might interfere with the image of the spark on the slit of the spectrograph. When the flask was filled with vapour, the spark was passed, and photographs taken with and without the self-induction coil. Gold and carbon electrodes were used in each case, and six photographs obtained on one plate as before. The lines shown by each element examined are tabulated at the end of the paper, and the effect of introducing self-induction is indicated by the change of intensity of the line. The strongest lines are marked ‘10,’ and the scale of intensities diminishes to ‘1,’ Ii a line has been looked for and not found, it is marked ‘0.’ Nebulous lines are marked ‘n.’; discontinuous lines ‘d.’; sharp lines ‘s.’ The more important photographs are reproduced in the plates. In all I examined the spectra given by sparking both gold and carbon electrodes, with and without self-induction, in nitrogen, oxygen, hydrogen, chlorine, bromine, iodine, sulphur, phosphorus, boron trichloride, silicon tetrachloride, sulphur dioxide, sulphuretted hydrogen, carbon dioxide, carbon monoxide, and hydrochloric acid. An examination of the spectra showed that when electrodes are sparked in an atmosphere of any kind the principal lines of the line spectra of the elements present in the atmosphere are obtained, and as a general rule with greatest intensity when self-induction is not introduced. In the case of compounds, only the line spectra of the component elements are seen, and the band spectra of the compounds are not seen except in the case of cyanogen, as is already known. In the case of hydrogen, the only electropositive gas examined, the effect of self-induction is to intensify and sharpen the hydrogen lines, and to remove, or almost entirely remove, the lines of gold or carbon, whereas, in the case of electro-negative gases such as oxygen and nitrogen, the effect of self-induction is to remove or almost 4x2 610 Scien tific Proceedings, Royal Dublin Society. entirely remove the spectra of these gases, the gold and carbon alone showing. With elements such as chlorine, bromine, and iodine, the effects of self-induction are not so pronounced. In the case of carbon the effects of self-induction are very pronounced and remarkable. First, with self- induction, the three bands attributed to cyanogen are seen clearly defined in almost any atmosphere except hydrogen, but without self-induction only the one band at ’ 38836 is seen, and it is also seen in any atmosphere except hydrogen. Adopting the theory of Schuster and Hemsalech, that the current is conveyed across the gap at first by the air when there is no self-induction, I conclude that under these conditions the temperature is too high for cyanogen to be formed by the carbon electrodes and any trace of nitrogen present. If this be so, the band which remains when self-induction is absent is probably due to carbon, and not to cyanogen. ; In the tables of wave-lengths the values given are those generally accepted, and are taken for the most part from Watt’s Index, Eder and Valenta’s, or Exner and MHaschek’s Tables. New wave-lengths were measured between known gold lines, and their wave-lengths determined by an interpolation curve. NITROGEN. Nitrogen was prepared from ammonium chloride and sodium nitrite, and was purified and dried by means of potassium hydrate and sulphuric acid. A great number of nitrogen lines show when there is no self-induction, but on inserting the Hemsalech coil most of these lines disappear, and those which remain are not so strong as before. The three cyanogen bands, d 4216:1, 3883-6, 435905, show very strongly with self-induction and carbon electrodes, but one band A 8885°6 alone remains when no self- induction is used. ‘This band is probably due to carbon and not to cyanogen at all. Schuster and Hemsalech showed that the introduction of self-induction reduced the temperature of the spark, and that when no self-induction was present the initial discharge of the current was conveyed across the spark- gap by the intervening air. Adopting this view, it would appear that with no self-induction the temperature was too high for cyanogen to be formed by the carbon electrodes and the surrounding nitrogen, and consequently the cyanogen bands do not appear in the spectrum, and the band d 3883°6 is, therefore, due to carbon. In the spectrum with gold electrodes the carbon lines show; no doubt this is due to a trace of carbon or hydrocarbons in the flask. Morrow— On the Influence of Sel/-Induction, Sc. Principal Lines of Nitrogen. 611 Intensity. | Intensity. Wave-length. | Waye-length. Without With | Without With S.1. Sere Sato ie rtsbtle = | 6603 8 | 6 4432-6 dn. 2 6480 5 4 4375-0 5n. 3 6172 | 3 0 4241-9 Bn 0 5942 4236-7 5n 0 5933 Ss 4228-5 5n 0 5929 4d 3 | 4216-1 = 10 5686 4 = 41972 = 9 5679 10 3 4181-5 cN. | = 8 5585 6 0 4177-7 = 7 5496 5 0 4165-4 ox i 5454 4 0 4041-4 6n. 3 5180 7 2 3995°3 10 4 5045-7 5 3 3956-2 6 1 5002-7 10 5 3883-6 10 10 4803-6 5 0 3871°5 8 8 4788° 4n. 0 3861°9 oN: 7 7 4780°1 4n. 4 3855°1 6 6 4643 Tn 3 3590-5 sa 8 4630°8 7 3 3586-0 ee = 7 4601-5 Tn. 3 | 3437-4 10 4 4552°6 dn. 4 3367-4 4 4531-0 5 4 3168-7 7d. 2 4511°8 4 3 | 2408-8 2d. 0 4447-2 6 4 CHLORINE. Chlorine was prepared from manganese dioxide and hydrochloric acid. The gas was washed by being allowed to bubble through water, and dried by pumice moistened with sulphuric acid, and sulphuric acid alone. The spark-gap had to be made much narrower so that the current would pass, as it would not do so when the electrodes were placed the usual distance apart. Many chlorine lines show in the spectrum, and 612 Scientific Proceedings, Royal Dublin Society. they are chiefly confined to the green region. The introduction of self- induction causes the lines to become sharper and more distinct, and in some cases they are intensified, which is the opposite effect to that produced with oxygen and nitrogen. The rays between A 3533 and A 3230 are absorbed; no lines show in this region when gold electrodes are used. With carbon electrodes the absorption is not so extensive. Three fairly strong lines \ 5140-0, \ 5099°0, and A5072°8 appear with self-induction when both gold and carbon electrodes are used; the line 5140°0 disappears without self-induction, but the others remain. ‘These lines must be due to chlorine, but no record of their measurements can be found. Some lines of chlorine between \ 6093 and X 5580, which show using gold electrodes, are not seen with carbon. The clearest and most complete spectrum of chlorine is obtained by using gold electrodes with self-induction present. All these chlorine lines showed in the spectrum of hydrochloric acid together with the lines of hydrogen. Principal Lines of Chlorine. Intensity. Intensity. Wave-length. Wave-length. Without Wit Without With 8.1. 8.1. Sad Ss. 6093 6 4n. 4572°8 5 3 5937 2 2 4371-7 5 3 5785 3 4d. 4343'8 6 5 5672 3n. 5 4307°6 4 3 5580 3 6 n. 4291:9 2 2 5460 | 4209-9 3 3n. ) 5 n. 5n 5448 $ 4133-2 9 5 5423 6 6 3916°8 5 5 5392 5 5 3871°5 3 n. 4n. 5225} 3861-0 8 n. 4 8 10 5208 3851°6 6 n. 4 4917°8 3 3 3845-7 5n. 4 4896-9 7n. Tn. 3833°5 4n. 4 4819°6 | 3829-5 4n. 4 10 n. 10 n. 4810-1 J 3820-4 4n. 4 4740°5 4 3 3622°7 3n. 4n. Morrow— On the Influence of Self-Induction, Sc. 613 Bromine. When there was much bromine vapour present, it was extremely difficult to make the current pass between the electrodes; it flashed across between the capillary tubes and the sides of the flask. A number of bromine lines were obtained in the spectrum, several showing in the ultra-violet region which had not been measured before. There was an absorption of the rays between 15700 and \ 3740. This absorption is nearer the visible region than that obtained with chlorine. Self-induction sharpens the principal lines, but has also the effect of causing many others to become discontinuous. When carbon was sparked in the vapour, there must have been some liquid condensed on the side of the flask, as only a very small part of the spectrum shows in the photograph. Principal Lines of Bromine. Intensity. | Intensity. Wave-length. | Without | with || Wave-length. | without | With Shi 8.1. 8.1. S.I. 3540°7 4 4a. || 2968-3 6 n. 5d. 3529-5 4 4 | 2925-8 6 | Bak 3518-1 4 4d. 2900°3 4 4d. 3506°5 4 4 2891°5 6 n. 6 3446-3 2 2 2872:0 4 3 3437°5 1 1 2767-3 3 2d. 3416-8 6 n. 6s 2745-0 3 2d. 3396-9 2 eee 2714-0 3 2 3354-0 4 4d. 2659-0 6 4 3336-9 6 n. 4d 2594-0 4n. s. 3322-0 3 3 2557-2 6n. $ 3237-0 2 0 2541-7 6n. 8. 3168-5 3 3d. 2522'1 7 n. 5s. 3148-5 3 2 2489°3 3n 2 3117-5 3 3 24655 3n 0 3074:8 5n. 4d. 2395-1 a ti eelen 0 3057-2 2 2 23930 | 2n. 0 3020°8 4 4 2369-0) none 4 8. 2971°8 6 n. dn 2386°9 4n. 4s. IopINnE. _ The spectrum of iodine shows twenty-six lines in the ultra-violet region. These have not been observed before, as the previous measurements extend 614 Scientific Proceedings, Royal Dublin Society. only to’ 3600. The effect of self-induction is to eliminate some lines altogether, and to cause others to become discontinuous. The absorption band is in the visible region, so that with chlorine, bromine, and iodine the absorption seems to move along the spectrum towards the red end with increase in the atomic weight of the element examined. Principal Lines of Iodine. Intensity. | Intensity. Wave: length: i )rvithont i: i ilswitht) | Wave teneth. | rtnene llcwathen Sia, eos | STG S.1. : 3302-9 3 On ye allmaosses 6 3d. 3288-8 5 0 3037-4 4 0 3274-7 4 a | 9953-3 6 1 3153°2 2 2d. | 2789-9 1 0 3116-6 2 2 2730-0 3 2d. 3102°7 2 2d. 2712°3 3 2d. 3091-0 2 2d. 2616-5 1 1d. 3087°9 5 2 2615-0 1 0 3081°5 3 2 | 2611-3 1 14. 3078-2 2 2 | 2598-7 4 3d. 3072°8 2 2 | 2583-0 6 4d. 3068-0 2 0 2566°1 Bn. 2d. 3064:8 2 0 2564-0 4 1d. Hyprocen. Hydrogen was prepared from zine and sulphuric acid. In order to purify the gas, it was passed through tubes containing :— (1.) Pumice moistened with lead acetate solution, to remove sulphuretted hydrogen. (2.) Pumice moistened with silver sulphate to remove arsenic or phosphorus. (3.) Solid potassium hydroxide, to remove sulphur dioxide. (4.) Pumice moistened with sulphuric acid, (5.) Sulphuric acid alone, to remove Inoibure: Hydrogen was the only non-metallic element examined by Schuster and Hemsalech. They noticed that if there were enough self-induction the hydrogen lines could be obtained almost as sharp as those of the vacuum tube spectra of that element. In my photographs self-induction makes the lines sharper, but at the same time it causes the elimination of the lines due to the electrodes. This is especially so. when gold is sparked in Morrow— On the Influence of Self-Induction, &c. 615 hydrogen, when none of the gold lines appears at all, demonstrating the fact that the hydrogen and not the vapour of the electrodes conveys the current across the spark-gap. Hydrogen being electropositive evidently acts in this case like the metals, the opposite effect being observed with electronegative elements. There are five hydrogen lines seen in the photographs, all of which are broad and nebulous, and three of these are exceedingly strong. The so-called cyanogen band A 38888, which remains in the spectra when carbon is sparked without self-induction in nitrogen and in the other non- metallic elements, has disappeared in the case of hydrogen. But considering the facility with which hydrogen carries the current to the complete elimi- nation of the lines due to the metallic electrodes, it does not seem remarkable that this band, which in my belief is due to carbon, has disappeared. Principal Lines of Hydrogen. Intensity. Intensity. Wave-length. | Without |) with || W@ve-length. Without. | with s. 1. 8.1. Sh il, SI. 6563 10 n. 10s. 4101°8 ans 5.n. 4861°5¢ 10 n. 9s. 3970°2 4n. 3n. 4340°7 9n. 8 OXYGEN. Oxygen was obtained by heating potassium permanganate. The gas was purified and dried by being passed through water, tubes containing solid caustic potash, pumice moistened with sulphuric acid, and then finally bubbled through sulphuric acid. Many lines due to oxygen show in the spectrum, but a great number of these disappear or are considerably weakened by the introduction of the self-induction coil. With both carbon and gold electrodes some lines show in the spectra which must be due to oxygen, although no record of their measurements has been found. There are gold lines whose wave-lengths correspond with these, but there being no gold present in the carbon used it seems as if these so-called gold lines had been wrongly identified, and that they were really due to the oxygen of the air in which the gold had been sparked. These lines are 4 2982:9; A 2382:5; X 2365:0; A 2852:7; d 2300:°6. These all occur with no self-induction, and in some cases faintly with self-induction.* 1 Compare Hartley and Adeney’s ‘‘Measurements of the Waye-lengths of Lines of High Refrangibility in the Spectra of Elementary Substances.’’ Phil. Trans. Roy. Soc., 1884, p. 63. DURA" SCIENT. PROC. R.D.S., VOL. XIII., NO, XXXIX. 4y 616 Scientific Proceedings, Royal Dublin Society. A line \ 3470°8 appears strongly with both gold and carbon in oxygen without self-induction. Exner and Haschek have a line \ 3471°1 of intensity 1 in their tables of oxygen, but mark it NP As there is only a very faint indication of this line when carbon and gold are sparked in air, it would seem that it is not a nitrogen line, and must be due to oxygen. The ultimate lines of manganese, X 2801°3, 2798°5, and X 2795:3, show in the spectra, owing to a trace of this element being carried over by the oxygen, notwithstanding the large number of absorption-tubes used. Principal Lines of Oxygen. Intensity. | Intensity. Wave-length. Wave-length. | Without With | Without With 8.1. 8.1. | §.1. Sale 4705°5 10 5d. || 3919-2 10 0 4676°3 4 4d. 3912:2 6 0 4661°8 4 0 3882°5 6 0 4661-0 10 6d. 3864-7 5 0 4641-9 10 0 8851°5 3 0 4638:9 10 0 3824°2 3n. 0 4596°3 10 0 | 3760'0 8 0 4591°1 10 0 3749°7 8 3 4466°5 6 0 3727°5 8 3 4415°1 8 6 37129 7 0 4367:0 6 8 3471°1 8 0 4348-5 8 6d. 3408°4 Tn. 0 4187'8 9 0 3390°4 8 0 4169°6 4 0 3377°3 8 0 4155:2 6 2d 3139-4 bn 0 4143-2 5 0 3135°3 5n 0 4119°7 7 4 2982°2 6n. 0 4093-1 4 0 2478°7 5d 0 4085-4 4 0 2445°5 6 0 407671 — 0 2433°6 6 0 4072-4 10 n. 0 2418°7 3 0 4070-0 —_— 0 2382°5 2d. 0 8973-4 7 0 2365°0 4 0 3954°5 6 0 2352°6 4 0 3945:2 6 0 2300°6 1 0 Morrow— On the Influence of Self-Induction, &c. 617 SuLPuurR. Some sulphur was placed in the small quartz flask and vapourized. Then the current was passed, and the spectrum photographed. Many lines appear which are chiefly in the visible region, but there are some as far as \3356°5. Self-induction causes all the sulphur lines to disappear when sulphur-vapour is used. Sulphur dioxide and sulphuretted eter both show all the lines obtained with sulphur alone, and with sulphur dioxide a fairly strong line 14486 appears, which is not seen with sulphur. The current did not pass easily when the atmosphere was sulphur dioxide, but the sulphur lines come out very strongly in the photograph, together with oxygen lines. A few sulphur lines still show when self-induction is introduced with sulphur dioxide, though these lines are not seen with sulphur alone. The current passed easily with sulphuretted hydrogen, but the sulphur lines do not show so strongly as with sulphur dioxide; the hydrogen lines are more prominent. The hydrogen apparently conveyed the current easily across the spark-gap as it did with pure hydrogen, to the exclusion of a great part of the sulphur. Principal Lines of Sulphur. Intensity. | Intensity. Wave-length. = Wave-length. Without With : Without With 8.1. Sralp | fio! 8.1. 5640°3 2 0 4095°3 i) 0 6454-0 3 0 4076°0 i) 0 5433-0 3 0 4072°2 - 5 0 5345°8 2 0 3983°6 3 0 5320°8 2 0 3848°8 6 0 4811-9 2 0 3727°5 4 0 4486-0 ia 3* 8717°9 3 0 4415-0 5 0 3669-1 2 0 4349°5 5 3* 3662°1 2d. 0 4294°5 4 3* 3596'1 3 0 4253°7 3 0 3067°4 2 0 4189-9 3 2* 349774 6 0 4174°5 aon! 3* 3471°0 2n. 0 4162°8 4n 4* 3390°3 3 0 4153-2 4n 4% 3387°2 3 0 4145°2 4n 4* 3370°5 4 0 4119-4 5 0 3356°5 2n. 0 * Seen with SOQz2 only. = K bo 618 Scientific Proceedings, Royal Dublin Society. PHOSPHORUS. It was extremely difficult to obtain a spectrum of phosphorus owing to the vigour with which this element attacked the apparatus. A piece of phosphorus about the size of a pea was placed in the quartz flask and the current passed for some time. At first the phosphorus caught fire and burned until apparently all the oxygen in the flask had been used up. Then on heating the flask gently the phosphorus vapourized, but very soon the glass capillary tubes surrounding the electrode connexions were attacked and broken, which resulted in the spark passing across between the platinum connexions, not between the electrodes. Then quartz tubing was used for insulating the wires, the ends being closed with plaster of Paris. When the current had passed for a short time, the platinum wires round the electrodes were attacked and broken. It was found that iron was not affected, and so it was substituted for the platinum. But before any photographs of the spectrum could be taken, some phosphorus had formed a red deposit on the side of the flask, which deposit was supposed to be red phosphorus. But it would not vapourize again, even when made red-hot with a flame from a Mecker burner, but turned black. This deposit prevented the image of the spark from being focussed on the slit of the spectrograph. The phosphorus had evidently attacked the quartz, as nothing would remove the black substance except hydrofluoric acid, which of course removed a coating of quartz at the same time, but if cautiously used is exceedingly convenient for cleaning the tube. This shows the extremely vigorous manner in which phosphorus attacks quartz and platinum. The gold electrodes were apparently unaffected. The spectrum of phosphorus was eventually obtained by sparking the electrodes in phosphoretted hydrogen prepared from caustic potash and phosphorus. Some phosphorus was deposited on the quartz tube, but by keeping one side of the tube heated all the time it remained transparent. The spectrum obtained showed some hydrogen lines, but only four lines due to phosphorus, which consist of two pairs which are very characteristic, and are situated in the extreme ultra-violet. . A most peculiar violet light was emitted when the phosphorus vapour was being sparked. Morrow— On the Influence of Self-Induction, &c. 619 Principal Lines of Phosphorus. Intensity. Intensity. | Waye-length. Wave-length. |— Withont With Without With Sale Sale 8.1. Seple 2504-7 6 6 2535°5 8 | 8 2553-2 7 7 2534-0 6 | 6 _l Boron. The boron spectrum was obtained by vapourizing boron trichloride. The spark emitted a brilliant white light during the passage of the current. Only four lines of boron are seen in the photograph, but many lines of silicon and chlorine. This may have been due either to silicon in the boron trichloride or to the boron attacking the quartz flask. The introduction of self-induction has evidently no effect on the boron spectrum. Principal Lines of Boron. Intensity. Intensity. Wave-length. |——__—__————_|| Wave-length. Without With Without With 8. I. 8.1 8.1. Sa 3451°3 10 10 3496°8 8 8 3497°7 8 8 2267-0 2 2 | SILICON. Silicon tetrachloride was placed in the quartz flask, and heated very gently. ‘The electrodes were then sparked in the vapour, and a photograph taken of the spectrum. There was a very brilliant white light emitted by the spark during the passage of the current. Twenty lines, apparently due to silicon, appear, and some of these are most characteristic and easily recognized. Of ‘course chlorine lines are also seen, but these may be easily detected by simply superposing a plate of the chlorine spectrum on that of silicon tetrachloride. Self-induction has apparently no effect on the spectrum of silicon. 620 Scientific Proceedings, Royal Dublin Society. Principal Lines of Silicon. Intensity. Intensity. Wave-length. Wave-length. | Without With Without With Sox Cure 8.1. 8. I. oi 4131-0 | 25286 7 7 10 10 | 4128-2 | 2524-2 | 7 7 3905°8 10 10 2519°3 6 6 3862'8 Sn 8n 25162 W 7 3856°2 8n 8n 2514-4 7 7 2987°7 6 6 2507-0 7 tf 2881-7 10 10 2452°2 4 4 2631°4 7 aan? 2443-0 4 4 2568'8 2 lente 2438-9 4 4 2541°9 5 ka 2435°2 6 6 2533-2 4 sens 2216'8 2 2 | PLATE XLVIII. SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. “ ~~ Pinos j RNID: POUT AA, RAPA FOR DO CUMING: OO nn Ny WAG SCIENT. PROC. Carbon ” | ” ' Gold »” | Gold | (RIE t rie eon mp pe \ ” = el - a Carbon Ta Te » SeaereNfas ot Gold » i} Carbon bie tl Gold i ” Hetoeallh ei i » are ie ip a. Carbon a a » Fl Tr : | PATI R. DUBLIN SOC., N.S., VOL. XIII. a (Or rTre ¢ Sait HYDROGEN. Tmo as! Pees cated BROMINE. | Eh tie NER | IODINE. || PEM NT | Pee TT PLATE XLIX. SCIENT. PROC. R. DUBLIN SOC., N.S., VOL. XIII. Carbon ! i NITROGEN. TT ae gaat eo iba Ps lpn OT RST TTT TT TTT TI TY ie TE l (ETE | | Ll |e ; | OXYGEN. i ! | TEE an ET | | | TSI | LT eS Ey | ihn aa ST 3 | SULPHUR. ee | | | a a aa | Ta! | ae) ee PHOSPHORETTED HYDROGEN. PLATE L. SCIENT . PROC. R. DUBLIN SOC., N.S., VOL. XIII. BORON TRICHLORIDE. Mae 0), el 2 a 1 PERNT torpor teTe NY A a ss sell ie | TT poamafo|perveres amen | 1 br 1pemmapemtpeesres | oy ' | SILICON TETRACHLORIDE. | SSSA EA Gene TT 111 mmemarandare frmrnt presamtesenovee toil sf ' 111 frsomamapranjenr hacrp—ond a TU a ee \ yrmese remains) CARBON DIOXIDE. Te Tt SSE a i dpa ela Hl) |__|; 8 6 A nF TIE T Ewe | | | | SIT ron Ht Fy “ SULPHUR DIOXIDE wih \ tL. |e PEATE, LI: Ge 621 ) INDEX TO VOLUME XIII. Adams (J.). On the Germination of the Seeds of some Dicotyledons, 467. Amount of Radium Emanation in the Soil andits Escape into the Atmosphere (Joty and Smyrn), 148. Arber (. A. Newell). Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks; Part I.—The Lower Carboniferous (Carboniferous Limestone) Flora of the Ballycastle Coalfield, County Antrim, 162. Award of the Boyle Medal to Professor John Joly, M.A,, SC.D., F.R.S., April 25, 1911, 142. to Sir Howard Grubb, r.r.s., April 16, 1912, 288. Bothodendron (Cyclostiegma) kiltorkense, Haughton, sp. (Jonson), 500. Boyle Medal, see under Award. Brown (W.). Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected tothe Influence of Longitudinal Magnetic Fields, 28. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris (Drxon and ATKINS), 219. Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers (PETHYBRIDGE), 12. Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks (ARBrR), 162. SOIENT. PROO. R.D.S., VOL. XIII., INDEX. Dixon (Henry H.). A Thermo-Electric Method of Cryoscopy, 49. Dixon (Henry H.) and W. R. G. ATxKINs. Changes in the Osmotie Pressure of the Sap of the Developing Leaves of Syrnga vulgaris, 219. Osmotic Pressure in Plants. I.— Methods of Extracting Sap from Plant Organs, 422. Osmotic Pressure in Plants. II.— Cryoscopic and Conductivity Measure- ments on some Vegetable Saps, 434. Variations in the Osmotic Pressure of the Sap of Ilex Aquifolium, 229. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera Helix, 239. Dowling (John J.). Steady and Turbulent Motion in Gases, 378. Fenton (E. G.). Notes on Recent Pampa and other Formations in Patagonia, 600. Fletcher (Arnold L.). The Melting Points of some of the Rarer Minerals, 443. A Refined Method of obtaining Sublimates, 460. Forbesia cancellata, gen. et sp. nov. (Sphenopteris sp., Baily) (JoHnson), 177. Germination of the Seeds of Some Dicoty- ledons (ADAMS), 467. Grubb (Sir Howard). Improvements in Kquatorial Telescope Mountings, 223. Heterangium hibernicum, sp. novy.; A Seed-bearing Heterangium from County Cork (Jonson), 247. 4z Pe 4\S0 NOV 22 1918 “¢ “ nian /nstit,s / \\ 622 Index. Improvements in Equatorial Telescope Mountings (GrueB), 223. Inheritance of the Dun Coat-Colour in Horses (Winson), 184. Inheritance of Milk-Yield in Cattle (Witson), 89. Inter-Alternative as opposed to Coupled Mendelian Factors: A Solution of the Agouti-Black Colour in Rabbits (Witson), 589. IsArcheopteris a Pteridosperm? (JOHNSON), 114. Johnson (T.). Forbesiu cancellata, gen. et sp. noy. (Spenopteris, sp., BamEY), 177. Heterangium Hibernicum, sp. noy. : A Seed-bearing Heterangium from Co, Cork, 247. ——— Is Archeopteris a Pteridosperm ? 114. The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland, 137. — On Bothrodendron (Cyclostiyma) kiltorkense, Haughton, sp., 500. — A Seed-bearing Irish Pteridosperm, Crossotheca Héninghaust, Kidston (Lyginodendron oldhamium, William- son), 1. Joly (John). A Method of Microscopic Measurement, 441. Radiant Matter, 73. Joly (John) and Louis B. Smyru. On the Amount of Radium Emanation from the Soil and its Escape into the Atmosphere, 148. Kerr (A. F. G.). Notes on Dischidia raffesiana, WALL, AND Dischidia num- mularia, Br., 293. Lyons (William J.). A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g, Wax, in passing through its Fusion Stage, 63. Mechanical Stress Magnetisation of Nickel (Part II.), and the Subsidence of Tor- sional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields (Browy), 28. Melting-Points of some of the Rarer Minerals (FLErcHER), 445, Method of Exact Determination of the Continuous Change in Absolute Density of a substance, e.g. Wax, in passing through its Fusion Stage (Lyons), 63. Method of Microscopic Measurement (Jony), 441. Morrow (Genevieve V.) On the Influence of Self-Induction on the Spark Spectra ot Certain Non-Metallic Elements, 607. The Ultimate Lines of the Vacuum- tube Spectra of Manganese, Lead, Copper, and Lithium, 269. Notes on Dischidia rafflesiana, WALL, and Dischidia nummularia, Br. (Kerr), 293. Occurrence of Archeopeteris Tschermaki, Stur, and of other Species of Archeop- teris in Ireland (Jounson), 137. Osmotic Pressures in Plants. I.— Methods of Extracting Sap from Plant Organs (Dixon and Arxkins), 422. II.—Cryoscopie and Conductivity Measurements on some Vegetable Saps (Drxon and Axis), 434, Pethybridge (G. H.). Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers, 12. On the Rotting of Potato Tubers by a new species of Phytophthora having a method of Sexual Reproduction hitherto undescribed, 529. Pethybridge (G. H.) and Paul A. Murphy. On Pure Cultures of Phytophthora in- JSestans De Bary, and the Development of Oospores, 566. Pollok (James H.). On the Vacuum- Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I— Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Anti- mony, and Aluminium, 202. -——— On the Vacuum-tube Spectra of some Metals and Metallic Chlorides. Part I1.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium, 253. Index. 625 Pure Cultures of Phytophthora infestans De Bary, and the Development of Oospores (PETHYBRIDGE and MurpHy), 566. Radiant Matter (Joy), 73. Recherches Expérimentales sur la Densité des Liquides en dessous de 0° (TmmeEr- MANS), 310. Retined Method of obtaining Sublimates (FrercHer), 460. Rotting of Potato Tubers by a new species of Phytophthora haying a method of Sexual Reproduction hitherto unde- scribed (PETHYBRIDGE), 529. Seed-bearing Irish Pteridosperm, (rosso- theca Hininghaust, Kidston (Lyginoden- dron oldhamium, Williamson) (Jonn- son), 7. Steady and Turbulent Motion in Gases (Dowtine), 375. Thermo-Electric Method of Cryoscopy (Drxon), 49. Timmermans (Jean). Recherches Wxpéri- mentales sur la Densité des Liquides en dessous de 0°, 310. Ultimate lines of the Vacuum-tube Spectra of Manganese, Lead, Copper, and Lithium (Morrow), 269. Unsound Mendelian Developments, especi- ally as regards the Presence and Absence Theory (Winson), 399. Vacuum-tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part 1.—Cadmium, Zine, Thallium, Mercury, ‘Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium (PotLox), 202. Vacuum-tube Spectra of some Metals and Metallic Chlorides. Part II.—Lead, Iron, Manganese, Nickel, Cobalt, Chro- mium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium (Potton), 253. Variations in the Osmotic Pressure of the Sap of Ilex Agquifolium (Dixon and ATKINS), 229. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera Helix (Drxon and Arxins), 239. Wilson (James). The Inheritance of the Dun Coat-Colour in Horses, 184. The Inheritance of Milk-Yield in Cattle, 89. Inter-Alternative as opposed to coupled Mendelian factors: A Solution of the Agouti-black Colour in Rabbits, 589. Unsound Mendelian Developments, especially as regards the Presence and Absence Theory, 399. END OF VOLUME XIII. = 16. 17. 18. SCIENTIFIC PROCEEDINGS. VOLUME XIII. . A Seed-Bearing Irish Pteridosperm, Crossotheca Héninghausi, Kidston (Lyginodendron oldhamiuwm, Williamson). By T. JoHNson, D.so., F.L.S. (Plates I.-IIT.) (March, 1911.) 1s. . Considerations and Experiments on the supposed Infection of the Potato Crop with the Blight Fungus (Phytophthora infestans) by means of Mycelium derived directly from the planted Tubers. By Grorcz H. Petuysripes, B.SC., PH.D. (March, 1911.) 1s. . Mechanical Stress and Magnetisation of Nickel (Part II.), and the Subsidence of Torsional Oscillations in Nickel and Iron Wires when subjected to the Influence of Longitudinal Magnetic Fields. By Witu1am Brown, 8.so. (April 15, 1911). 1s. . A Thermo-Electric Methed of Cryoscopy. By Henry H. Dixon, sc.p., F.R.s. (April 20, 1911). 1s. . A Method of Exact Determination of the Continuous Change in Absolute Density of a Substance, e.g. Wax, in passing through its Fusion Stage. By Wiou1am J. Lyons, B.a., a.R.c.sc. (LonpD.). (May 16,1911). Gd. . Radiant Matter. By Joan Jony, sc.p., r.R.s. (June 9,1911.) 1s. . The Inheritance of Milk-Yield in Cattle. By James Wiuson, m.a., B.SC. (June 12, 1911.) 1s. . Is Archeopteris a Pteridosperm? By T. Jounson, D.so., F.L.s. (Plates IV.—-VI.) (June 28, 1911.) 1s. 6d. . The Occurrence of Archeopteris Tschermaki, Stur, and of other Species of Archeopteris in Ireland. By T. Jonson, D.sc., F.u.s. (Plates VII. and VIII.) (June 28, 1911.) 1s. . Award of the Boyle Medal to Proressorn Jonn Jouy, M.A., SO.D., F.R.S. (July, 1911.) 6d. . On the Amount of Radium Emanation in the Soil and its Escape into the Atmosphere. By Joun Joty, sc.p., F.x.s., and Louis B. Smyrx, B.a. (Plate IX.) (August, 1911.) 1s. . Contributions to our Knowledge of the Floras of the Irish Carboniferous Rocks. By E. A. Newert ARBeErR, M.A., F.L.S., F.G.S. (Plates X.-XII.) (January, 1912.) 1s. . Forbesia cancellata, gen. et sp. noy. (Sphenopteris, sp., Baily.) By T. Jounson, D.sc., F.u.s. (Plates XIII. and XIV.) (January, 1912.) 1s. . The Inheritance of the Dun Coat-Colour in Horses. By James Winson, M.a., B.Sc. (January, 1912.) 1s. . On the Vacuum Tube Spectra of the Vapours of some Metals and Metallic Chlorides. Part I.—Cadmium, Zine, Thallium, Mercury, Tin, Bismuth, Copper, Arsenic, Antimony, and Aluminium. By Jamus H. Poxtokg, D.so. (Plates XV. and XVI.) (February 21,1912.) Is. Changes in the Osmotic Pressure of the Sap of the Developing Leaves of Syringa vulgaris. By Henry H. Dixon, sc.p., r.z.s., and W.R. G. Atkins, u.A. (February 21,1912.) 6d. Improvements in Equatorial Telescope Mountings. By Sm Howarp Gruss, F.R.S.. (Plates XVII.—XIX.) (March 26,1912.) 1s. Variations in the Osmotic Pressure of the Sap of Ilex aquifolium. By Henry H. Dixon, sc.p., r.n.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. VV AZ2ZAF LEK SCIENTIFIC PROCEEDINGS—continued, 19. Variations in the Osmotic Pressure of the Sap of the Leaves of Hedera helix. By Henry H. Drxoy, sc.p., F.r.s., and W. R. G. Arxins, m.a., a.t.c. (April 9, 1912.) 6d. 20. Heterangium hibernicum, sp. nov.: A Seed-bearing Heterangium from County Cork. By T. Jounson, p.sc., F.u.s. (Plates XX. and XXI.) (April 12, 1912.) 1s. 21, On the Vacuum Tube Spectra of some Metals and Metallic Chlorides. Part IJ.—Lead, Iron, Manganese, Nickel, Cobalt, Chromium, Barium, Calcium, Strontium, Magnesium, Potassium, Sodium, and Lithium. By Jars H. Portox, p.sc. (Plates XXII. and XXIII.) (May 7, 1912.) 1s. 22. The Ultimate Lines of the Vacuum-tube Spectra of Manganese, Lead, Copper, and Lithium. By Gunrvirve V. Morrow, a.x.c.sc.1. (Plate XXIV.) (May 11, 1912.) 1s. 23. Award of the Boyle Medal to Sir Howarp Gruss, r.r.s., April 16, 1912. (May 18, 1912.) 6d. 24. Notes on Dischidia rafflesiana, Watu., anv Dischidia nummularia, Br. By A. F. G. Kerr, up. (Plates XXV.-XXXI.) (September 30, 1912.) Qs. 25. Recherches Expérimentales sur la Densité des Liquides en dessous de 0°. Par Jean Timmermans. (October 18, 1912.) 3s. 26. Steady and Turbulent Motion in Gases. By Joun J. Downe, mua. (Plates XXXII. and XXXIII.) (November 16,1912.) 1s. 6d. 27. Unsound Mendelian Developments, especially as regards the Presence and Absence Theory. By James Witson, m.a., B.sc. (December 18, 1912.5 1s. 6d. 28. Osmotic Pressures in Plants. I.—Methods of Extracting Sap from Plant Organs. By Hrwry H. Drxoy, se.d., F.r.s., and W. R. G. Arxins, M.a., A.1.c. (February 8, 1913.) 1s. 29. Osmotic Pressures in Plants. IJ.—Cryoscopic and Conductivity Measurements on some Vegetable Saps. By Henry H. Dixon, sc.p., F.r.s., and W. R. G. ATKINS, M.A., a.t.c. (February 8, 1913.) 6d. 30. A Method of Microscopic Measurement. By J. Joty, sc.p., ¥.z.s. (February 7, 1918.) 6d. 81. The Melting-Points of some of the Rarer Minerals. By Arnoup L. Furtcusr, M.A., BE. (February 15, 1913.) 1s. 82. A Refined Method of obtaining Sublimates. By Arnotp L. Furtcner, .a., B.E. (February 17,1913.) 6d. 88. On the Germination of the Seeds of some Dicotyledons. 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