CRYPTOGAMIC BOTANY PRINTED BY SPOTTISWOODE AND CO., NEW-STREET SQUARE LONDON A HANDBOOK OF CRYPTOGAMIC BOTANY BY ALFRED W. BENNETT, M.A., B.Sc, RL.S. LECTURER ON BOTANY AT ST THOMAS'S HOSPITAL AND GEORGE MURRAY, F.L.S. SENIOR ASSISTANT, DEPARTMENT OF BOTANY, BRITISH MUSEUM AND EXAMINER IN BOTANY, GLASGOW UNIVERSITY WITH 378 ILLUSTRATIONS LIBRARY NEW YORir BOTANICAL GARDEH LONDON LONGMANS, GREEN, AND CO. AND NEW YORK : 15 EAST 16"^ STREET 1889 All rights reseriied 34 BOTANli GARDI PREFACE. -•o*- In presenting to the botanical public this ' Handbook of Cryptogamic Botany,' the result of the labour of several years, the authors are deeply sensible of its inevitable defects. In traversing so wide a iield, it is im- possible that a single worker, or even two, can be practically acquainted with more than a comparatively small portion of it. It is necessary, therefore, to consult a literature, the extent of which, even for a single year, is appalling, and in which it is often difficult to distinguish between trustworthy and untrustworthy observations. The attempt has, notwith- standing, been made by the authors to acquaint themselves with the contents of every important publication of recent years bearing on Cryptogamic Botany, and issued in English, French, German, Italian, or Latin. It is beyond hope but that inaccuracies have crept in, or that observations which should have been noted have escaped attention. We shall be grateful to workers and writers who will inform us of any such inaccuracies or omissions, and especially to those who will kindly supply us, with a view to future editions, with copies of papers containing records of new and original observations or theories. Those relating to i. Vascular Cryptogams, Muscineae, Algse, and Schizophyceae should be r: directed to Mr. Bennett ; those relating to Fungi, Mycetozoa, and Schizo- . mycetes to ^Ir. ^Murray ; these being the portions of the work actually ^; written respectively by each of us, although we hold ourselves severally ^ responsible for the whole contents of the volume. ^ So rapidly are' facts accumulating, and new views of affinity being ^pmulgated, that it may" be necessary to change one's opinion on some ^ints even in the interval between the printing of the earlier and later S&ets of a volume like this ; and this must be held to account for any vi PREFACE slight discrepancies that may be apparent between the general scheme of classification contained in the Introduction, and the details as carried out in the work itself. We have also to acknowledge the permission given by the publishers of the following works for electros to be taken from the illustrations contained in them, viz. : — De Bary, ' Comp. Morph. und Biol, der Pilze, Mycetozoen, und Bacterien,' and 'Vorlesungen liber die Bacterien'; Sachs, ' Lehrbuch der Botanik ' ; Goebel, ' Grundziige der Systematik ' ; Luerssen, ' Die Kryptogamen ' ; Schenk, ' Handbuch der Botanik ' ; Zopf, 'Die Spaltpilze ' : Hauck, ' Die Meeresalgen ' ; Reinke, ' Lehrbuch der Botanik ' ; Thome, 'Lehrbuch der Botanik ' ; Le Maout et Decaisne, ' Traite General de Botanique ' ; Solms-Laubach, ' Einleitung in die Palaeophytologie.' Of the remaining illustrations, many have been taken from nature ; others have been copied from the illustrations of previous W'Orks, especi- ally from Cooke's ' British Freshwater Alg^ ' ; and for others we have to thank the courtesy of the Councils of the Royal and Linnean Societies, and the publishers of the 'Annals of Botany.' In those branches of Cryptogamic Botany which have not been the immediate object of our own researches, we have freely consulted experts in these several departments, and have received from all the greatest kindness and most valuable assistance. In particular we wish to express our obligations in this respect to Mr. W. Carruthers, Pres. L.S., F.R.S. ; Mr. J. G. Baker, F.R.S. ; Professor F. O. Bower, F.L.S. ; Dr. R. Braithwaite, F.L.S. ; Mr. E. M. Holmes, F.L.S. ; and Mr. G. C. Karop, F.R.M.S. ALFRED W. BENNETT, December, 1888. 6 Park Village East, London, N.W. GEORGE MURRAY, British Museum (Natural History), Cromwell Road, London, S.W. CONTENTS. -»<>♦- INTRODUCTION PAGE I FIRST SUBDIVISION : VASCULAR CRVPTOGAMS Heterosporous Vascular Cryptogams class i. rhizocarpe.^ ,, n. SELAGINELLACE.^ . IsospoROUs Vascular Cryptogams class iii. lycopodiace^ . ,, iv. filices .... v. ophioglossace.-e vi. equisetace.^ Fossil Vascular Cryptogams . ;5 lO 21 21 38 53 53 64 95 100 114 SECOND SUBDIVISION: MUSCINE.-E class VII. ,, VIII. MUSCI hepatic.^ Fossil Muscine/E 132 136 156 172 THIRD SUBDIVISION: CHARACE^ class IX. charace.e Fossil Charace.^ . ^73 173 183 FOURTH SUBDIVISION : ALGyE class X. FLORIDE.*: . ,, XI. confervoide.^ heterogamy ,, XII. FUCACE.'E ,, XIII, PHvEOSPORE.^ ,, XIV. CONJUGAT.^ . ,, XV. CONFERVOIDE^ ISOGAM.t ,, XVI. MULTINUCLEAT/E ,, XVII. CCENOBIE/E Fossil Alg.e • • • • 184 191 219 228 237 258 272 280 291 303 Vlll CONTENTS FIFTH SUBDIVISION: FrXC.I . GROUI' I. I'lIVCOMYCETKS , CLASS XVIII. OOMVCETES ,, XIX. ZYC.OMYCKTES GROUI' II. Sl'OROCARPE,+: CLASS XN. ASCOMYCETES XXI. UREDINE.'E XXII. HASIDIOMYCETES J5 SIXTH SUBDIVISION: MVCETOZOA CLASS XXIII. MYXOMYCETES XXIV. ACRASIE.^;: SEVENTH SUBDIVISION: PROTOPHVTA Group I. Schizophycee CLASS XXV. ,, XXVI. ,, XXVIL PROTOCOCCOIDE.i: DLA.TOMACE.-E . CYANOPHYCE.T. Group n. Schizomycetes CLASS xxvin. schizomycetes PAGE 305 323 323 335 353 353 383 388 401 401 405 407 408 409 419 426 449 449 Index 457 IJ ;e II, 1 „ II. 35 122, J 186, J ) 187, 187, 187, 190, 208, ! 209, ) 209, ) 213, ) 250, 280, ; 296, 3 311. ) 313. ) 319. 326, J 335, 5 , 343. . 381, Errata ine 22,y^;"oophore read oo^phyte ,, 22, /or sporophoie read sporophyte descripiion of fig. 94, for Haulea read Hazviea line ID, for CcENOBi.^t read 'C*- INTRODUCTION. No general handbook to Cryptogamic Botany has appeared in the EngHsh language since the Rev. M. J. Berkeley's in 1857. Since then this department of botanical science has gone through little less than a revolution. Not only has the number of known forms increased enormously, but additions of great importance have been made to our knowledge of structure by the use of the microscope, and to the genetic connection of different forms by the careful following out of the life- history of particular species. The present work is an attempt to bring within the reach of botanists, and of the public generally who are in- terested in the study of nature, an acquaintance with the present state of our knowledge in this branch of science. It is not intended to replace in any way the numerous excellent handbooks or monographs which exist of special families or groups. Its scope is quite different. Neglect- ing the minor differences by which genera, or in many cases even orders, are distinguished from one another, the aim of the authors has been to bring before the reader the main facts of structure, of develop- ment, and of hfe-history, which mark the larger groups, contrasting them with one another, and referring only to the broader lines of demarcation within those groups. It is hoped that the work will be found useful to the beginner as well as to the more advanced student. One great difficulty in our work has been to observe a due propor- tion in the space allotted to the different groups ; and this has been in- creased by the necessity for a very different mode of treatment in the higher and the lower forms. Of the Vascular Cryptogams — more nearly allied in many respects to Phanerogams than to the lower Cryptogams — ■ our knowledge is, with some exceptions, as minute and exhaustive as that B 2 INTRODUCTION' of Flowering Plants ; and it is improbable that any living forms remain to be discovered differing in any material point of structure from those already known. Here, therefore, we are able to discuss systems of classification which claim something like finality ; and the difficulty of the compiler of a handbook is the enormous amount and the minute detail of the material to his hand, from which he has to cull those por- tions which seem suitable for his object. In order not to extend this portion of the work beyond due limits, it has been necessary frequently to practise rigid compression — beyond, probably, what many of our readers specially interested in these groups would have desired. The same remarks apply, to a large extent, to the Muscineae. But in the Thallophytes, and especially in the lower Algae and Chlorophyllous Protophyta, the case is very different. From the extremely minute size of many of these, and the much smaller extent to which they have been studied, new forms are constantly being discovered, and important ad- ditions are yearly being made to our knowledge of their life-history and of their structure. It is highly probable that among these groups, as well as in some of the orders of Fungi, forms will yet be discovered which cannot be assigned to any type at present known, gaps in the life- history of many species will yet be filled up, and organisms hitherto placed in widely separated families \\\\\ ultimately be found to be phases in one cycle of development. We have therefore, in this branch of our subject, brought before our readers every fact of importance known to us which is vouched for by observers in whom we have confidence ; and the classification here submitted is a purely tentative one. In the Algae, the Fungi, and the Protophytes, we do not attempt an exhaustive enumeration of orders or families which shall include every known organism, but describe in detail only those types which are of greater importance, and of which our knowledge is more complete. Something must be said on the classification adopted. In the Vascular Cryptogams and in the Muscineae this proceeds on generally recognised lines, in which there is not much room for difference of opinion. But a very different treatment seemed necessary of the Thallophytes, and of the relationship to one another of the Algae and Fungi, and of the different orders within each of these groups. Here the systems pro- posed are almost as numerous as the original investigators, and it has been necessary to choose that which appeared to the authors to bring together those organisms which are most nearly related to one another. Whether these two familiar terms represent a natural bifurcation in the classification of the lower organisms, is a question which has been very variously answered by different observers and theorisers. About fifteen years ago a system of classification of the Thallophytes was pro- INTRODUCTION 3 posed, on authority entitled to the highest respect,^ which altogether abolished the bifurcation into Algae and Fungi. On this system the sole character made use of in their primary' classification was the mode of reproduction. First came the Protophyta, in which no sexual mode of reproduction is known, followed by three primary classes (in ascending order) — the Zygosporeae, Oosporeae, and Carposporeae — distinguished solely by the degree of complexity of the sexual process. Each of these four classes was then divided into a series containing chlorophyll and a series not containing chlorophyll, the former including the organisms hitherto known as Alg^e, the latter those hitherto known as Fungi. In support of this view it was urged, with great plausibility, that, reproduction being the most important event in the life-history of a plant, the mode in which this is brought about must become fixed in each group by heredity ; while such a subordinate character as the presence or absence of chlorophyll is seen, in the higher plants, to be entirely without importance in determining affinity. But a little consideration will show that it is unsafe to apply the same rule to more highly and to less highly organised forms. In the higher forms of life the mode of sexual reproduction becomes, in its main features, absolutely fixed ; and throughout the vast range of Angiosperms — as in the higher animals — there is entire uniformity in this respect in all important points ; while in external morphology, and in the mode in which they obtain their live- lihood, there is the greatest diversity, even within a narrow circle of affinity. In the animal kingdom we may point, as an illustration of this law, to the existence of such a family as the Cetacea among Mammalia; among flowering plants we have only to consider such phenomena as the occurrence of parasitism, insectivorous habits, or the suppression of chlorophyll, in individual genera dispersed through a large number of natural orders. Even in subsidiary characters connected with the pro- cess of reproduction there is not the uniformity that might have lieen expected. While such an apparently subordinate point as the number of cotyledons in the embyro is so constant as to give its name to primary divisions of Phanerogams, a character which might have been supposed to be much more important (but which, it is instructive to observe, is connected with the mode in which the germinating embryo receives its nutriment)— viz. the presence or absence of endosperm— is not always constant, even within narrow limits. The first necessity of a nascent organism is to live ; and hence it is not surprising to find that in the lower forms of life the one character which remains most constant within wide circles of affinity is the mode of life. In the course of development ' See Sachs's Text-book of Botany, 2nd English edition, p. 244. B 2 4 INTRODUCTION of the higher forms nature may be said to have tried a variety of experiments in the mode of reproduction ; on the whole there is a con- tinual advance, hut still by no means infrequent fallings back to simpler modes ; and unless this law of retrogression is taken into account, any system of classification must ho. pro tanto imperfect and misleading. If these considerations have any weight, it is not surprising that, although the system of classification of Thallophytes above alluded to has been adopted by a few authorities in this country and on the Continent, it has not met with general acceptance. The adoption of its leading principle, that '/;/ each class Fungi have diverged as ramifications from various types of A-lgae,' ' is seen to lead to such startling results as the collocation in the same class of Spirogyra and Mucor, of Volvox and Peronospora, of Callithamnion and Agaricus. It may, on the contrary, be safely asserted that several of the most important groups among Fungi (take, for example, the Uredine^ and the Basidiomycetes) display no traces of genetic affinity with any known class of Alg^ ; and if, on the other hand, we have forms like Saprolegnia and Chytridium among Fungi, or Leptothrix and Beggiatoa among Protophyta, which betray strong indi- cations of a degraded affinity with groups of Algas, this by no means contradicts the general law that Fungi as a class form an altogether independent series. . Retrogression may take the form of the suppression of either the vegetative or the reproductive organs ; and wherever you have one of these sets of organs displaying strong development, while the other set of organs is very feeble or altogether wanting, you have prima facie evidence of retrogression. Of this examples will be given in the sequel. ^^^hile, therefore, we adopt the Protophyta as a primary class, with the general limits proposed by Sachs, we have no hesitation in reverting to the time-honoured division of the higher Thallophyte^ into the two great groups of Algae and Fungi. The classification of Fungi adopted is that of de Bary, consisting of a main series (called the series of the Ascomycetes), composed as follows : (i) Peronosporeas (with Ancylisteae and Monoblepharis), (2) Sapro- legnieae, (3) Mucorini or Zygomycetes, (4) Entomophthoreae, (5) Ascomycetes, (6) Uredineae ; and of divergent groups as follows: (7) Chytridineae, (8) Protomyces and Ustilaginese, (9) Doubtful Ascomycetes (Saccharomyces, &c. ), (10) Basidiomycetes. • The groups 1-4 are Phycomycetes, and 7 and 8 of the second series go with them ; while 9 stands in relation to 5, and 10 to 6; and they are * Sachs's Text-book, p. 244, foot-note. IXTRODUCTION 5 so considered together in the linear series in which they come in the book. The Phycomycetes approach the Algs (Chlorophyceae) very nearly ; and the other groups of Fungi bear a relation to the Phycomy- cetes which seems to negative any supposition of their independent connection with algal forms. One other point had to be decided, whether to commence at the bottom or at the top of the series. Had our purpose been to construct theoretically a genealogical tree for the lower forms of vegetable life, the former course must necessarily have been pursued, and in the laboratory there is no doubt much to be said in favour of proceeding from the simple to the more complicated types. But to the general student, ' from the known to the unknown ' is a very sound principle. And, among flowerless plants, not only are the higher types far the best known to the ordinary observer, but they are also those about the life-history of which we have the greatest certainty of knowledge. We have been confirmed in our belief of the correctness of this decision by observmg that in the last edition of Huxley and Martin's ' Elementary Biology ' these authors have (in the zoological section) abandoned the ascending for the descending order. The question of terminology is one of the greatest stumbling-blocks to the student of cryptogamy. Not only are new terms being constantly introduced, many of them quite needlessly or from an erroneous idea of structure ; but some that are in continual everyday use are employed in different senses by different writers of repute. The first requisite in a terminology, after accuracy, is simplicity ; and to this end we have, wherever possible, used anglicised instead of Latin and Greek forms. Many of the terms which we employ throughout this volume — such as sporange^ archegone, antherid, coenobe^ sckrote, epiderm, &:c. — will probably be accepted at once ; and it seems strange that the awkward and un- couth foreign forms of these words should have held their ground so long. With others there will no doubt be greater hesitation ; but we hope to see all, or nearly all, of the anglicised forms we have used gradu- ally introduced into all English works on cryptogamic botany, and the same principle possibly extended in other cases where we have not ventured to apply it. A striking instance of the uncertainty which still surrounds crypto- gamic terminology is afforded by the various senses in which different writers use the everyday term ' spore.' Le Maout and Decaisne and Asa Gray speak of spores as ' the analogues of seeds ; ' Berkeley de- .scribes the unfertilised oospheres of Fucus as spores ; Vines includes under the term all reproductive cells produced either asexually or sexually ; while Sachs defines a spore as a reproductive cell produced 6 INTRODUCTION either directly or indirectly by an act of fertilisation, reserving the term ' gonidium ' for those which are produced without any previous act of impregnation. It is obvious that one practical defect of this last sug- gestion is that it may necessitate a perpetual change of terminology as our knowledge advances. Every fresh extension of the domain of sexual fecundation — and it is probable that many such will take place — will involve the removal of a fresh series of reproductive cells from the cate- gory of gonidia to that of spores, even though they may not be the immediate result of an act of fertilisation. Again, if the spores of ferns and mosses are the indirect result of impregnation, it is difficult to say why the term should not ultimately include all reproductive bodies whatever, except the spores of the ' apogamous ferns ' with which Farlow and de Bary have recently made us acquainted, and of other similar abnormal productions, which are certainly not the result of impreg- nation, direct or indirect. It seems a sounder principle — and is certainly more convenient to the student— to base a system of terminolog}' on facts which can be confirmed by actual observation, rather than on unproved hypotheses. We jDropose, therefore, as the basis of our terminology, to restore the term spore to what has been in the main hitherto its ordinary significa- tion, and to restrict its use to a7iy cell produced by ordinary processes of vegetation, and ?iot directly by a u?iion of sexual ele??ie7its, which becomes detached for the purpose of direct vegetative propagation. The spore may be the result of ordinary cell-division or of free-cell-formation. In certain cases {zoospore) its first stage is that of a naked primordial mass of protoplasm. In rare instances it is multicellular, breaking up into a number of cells {polyspore, composed of 7nerispores, or breaking up into sporids). The simple term spore will, for the sake of convenience, be retained in ^Nluscinese and Vascular Cryptogams ; but in the Thallophytes it will generally be used in the form of one of those compounds to which it so readily lends itself, expressive of the special character of the organ in the class in question. Thus, in the Protophyta we have chlamydo- spores \ in the Myxomycetes, sporangiospores ; in the SaprolegniecS and many Algae, zoospores ; in the Uredinese, teleutospores, cscidiospores, uredospores, and sporids ; in the Basidiomycetes, basidiospores ; in the Ascomycetes (including Lichenes), ascospores, poly spores, and merispores : in the Diatomaceae, auxospores ; in the CEdogoniaceas, androspores ; in the Florideae, tetraspores ; and others belonging to special groups. The cell in which the spores are formed will, in almost all cases, be called a spora?ige ; and this term will be compounded in the same way as spore. INTRODUCTION 7 In describing the heterosporous Vascular Crj^ptogams it is usual to speak of the spores which give rise to the female prothallium and those which give birth to antherozoids as ' macrospores ' and ' microspores ' respectively. The first of these terms is doubly objectionable : firstly, etymologically, the proper meaning of /j-aKpos being not 'large," but 'long ;' and secondly, from the close similarity in sound of the two terms, an inconvenience, especially in oral instruction, which every teacher must have experienced. Seeing that the correct and far preferable terms megaspore and microspore are used by Berkeley, Areschoug, Carpenter, and others, it is difficult to understand how ' macrospore ' can ever have got into general use ; and these terms, together with ?negaspora7ige and mtcrosporange, will be used in the following pages. For similar reasons megazoospore is always used instead of 'macrozoospore.' The male organs of fecundation are so uniform in their structure throughout Cryptogams that very little complication has found its way into their terminology. The cell or more complicated structure in which the male element is formed is uniformly known among Cormophytes as well as Thallophytes as an antherid : the fecundating bodies are almost mvariably naked masses of protoplasm, provided with vibratile cilia, endowed with apparently spontaneous motion, and bearing the appro- priate name of antherozoids or ' spermatozoids.' The former of these is perferable for two reasons ; from its etymological connection with antherid, and because the use of terms compounded from ' sperm' should, for reasons to be detailed presently, be avoided for male organs. In only two important groups, Florideae and Ascomycetes, are the fecundating bodies destitute of vibratile cilia and of spontaneous motion : in the former case they are still usually termed ' antherozoids ; ' in the latter ' spermatia,'and their receptacles ' spermogonia.' In order to mark the difference in structure from true antherozoids, it is proposed to designate these motionless bodies in both cdi?,es poHiftoids ; the term ' spermogone ' is altogether unnecessary, the organ being a true antherid. A satisfactory terminology of the y^w^/t? reproductive organs presents greater difficulties, from the much greater variety of structure, and the larger number of terms already in use. The limits we have placed to the use of the term ' spore ' and its compounds require the abandonment of ' oospore ' for the fertilised ovum or oosphere in its encysted state (enclosed in a cell- wall 1, anterior to its segmentation into the embryo ; and this is the most important change involved in the terminology of the present volume. In devisinu; a term which shall include all those bodies which are the immediate result of impregnation, it was necessary to take two points specially into account. Firstly, the term must be capable of 8 INTRODUCTION defence on etymological grounds ; and secondly, it must, like 'spore,' be suited for ready combination. After much consideration we have de- cided on adopting the syllable sperm. No doubt the objection will present itself that the Greek (nrepfjia, like the Latin ' semen,' while origi- nally meaning the ultimate product of fertilisation, came afterwards to signify the male factor in impregnation ; and hence, in zoology, terms derived from these roots are used for the male fertilising bodies. But the objection applies to a much smaller extent to phyto-terminology, and the use in the proposed sense of the syllable ' sperm ' is justified by the universal employment in phanerogamic botany of such terms as 'gymnosperm,' 'angiosperm,' 'endosperm,' and 'perisperm.' Of crypto- gamic terms, where the syllable is used in the reverse sense, 'sperm-cell,' for antherozoid or pollen-grain, has never come into general use in this country ; ' spermatozoid ' is easily replaced by ' antherozoid ; ' ' spermo- gonium ' is simply a peculiar form of antherid, and ' spermatium ' has already been referred to. Accepting this term as the least open to objection of any that could be proposed, it will be found to supply the basis of a symmetrical system of terminology, which will go far to redeem the confusion that at present meets the student at the outset of his re- searches. For the unfertilised female protoplasmic mass the term oosphere is already in general use ; and, though not all that could be desired, it is proposed to retain it. The entire female organ before fer- tilisation, whether unicellular or multicellular, is designated by a set of terms ending in gone., such as archegone and carpogone, again following existing analogy. The term reproduction itself is often far too vaguely employed by botanical writers. We propose to limit its use, in accordance with its etymology, to the production of a new individual, that is, to a process of impregnation ; all cases of non-sexual multiplication being described as propagation. The object of the writer of a handbook is to gather up and to collate material already existing, winnowing, to the best of his judgment, the wheat from the chaff. Except, therefore, where original observations may have been made by the compiler himself, it will contain nothing new. In compiling from the writings of the original observers it was thought best, as far as possible, to use their own words, and this will account for the frequent close resemblance in the following pages of the descriptions contained to those in such works asde Bary's 'Comparative Anatomy of the Phanerogams and Ferns,' the ' Comparative Morphology and Biology of the Fungi, Mycetozoa, and Bacteria,' by the same writer, the scheme of which has been mainly adopted in outline, and Goebel's ' Outlines of Classification and Special Morphology.' Admirable, on INTRODUCTION 9 the whole, as are the translations of these works by which the Clarendon Press has enriched English scientific literature, it is the original work rather than the translation that we have in all cases followed. We wish here to express the great obligation under which we lie to these writers, and to acknowledge the extent to which we have borrowed from them. In the chapter on Fossil Vascular Cryptogams we have, to a considerable extent, followed Graf zu Solms-Laubach's excellent ' Einleitung in die Palaeophytologie,' though with some modifications. To the description of each group or family we have appended a bibliography of the researches on which that description is founded ; these having again been consulted, wherever possible, in the original language. 10 FIRST SUBDIVISION. VASCULAR CRYPTOGAMS. The Vascular Cryptogams include all the highest forms of cryptogamic life, and constitute a well-marked group of plants intermediate between the Gymnosperms, or lowest division of Flowering Plants, and the lower or Cellular division of Flowerless Plants. From the former they differ mainly in the mode in which fertilisation is effected ; from the higher forms of the latter in the much greater differentiation of tissues. The term ' vascular ' Cryptogams is, however, strictly speaking, correct only to a limited degree. Although the arborescent and fruticose species display as well-marked a differentiation of their tissues as Flowering Plants, into epidermal tissue, ' vascular ' bundles, and fundamental tissue, and the bundles consist of distinct xylem and phloem (without any intermediate cambium, as in Gymnosperms), it is only rarely, as in that group of Flowering Plants, that the xylem is composed of vessels in the true sense of the term. The Vascular Cryptogams and the highest families of Cellular Cryptogams are distinguished from Flowering Plants by an obvious Alternation of Generations between Sexual Generation or Oophyte^ and Non-sexual Generation or Sporophyte. The former is a small and purely cellular structure, usually of very temporary duration, the purpose of which is to bear the sexual organs of reproduction, male antherids and female archegones, the structure of which is uniform in all essential characters throughout the class, and which are borne on a cellular ex- pansion, \hQ prothailium. This prothallium may be either monoecious or dioecious — that is, the male and female organs may be borne on the same or on different prothalHa. The act of fertilisation consists in the impregnation of an oosphere, a naked mass of protoplasm contained within the central cell oi the archegone, by one or more a?itherozoids, minute masses of protoplasm endowed with spontaneous motion by means of vibratile cilia, which escape from the cells of the antherid and penetrate to the central cell of the archegone. The immediate result of the impregnation of the oosphere is that it invests itself VASCULAR CRYPTOGAMS U with a cell-wall of cellulose, and thus becomes an oosperm, which develops into the embryo, and finally into the sporophyte, which is often of great size and extended length of hfe. It is this that is com- monly known in popular language as the Fern, Club-moss, (S:c. On it are produced, without any process of fertilisation, the spores, which are always single cells, protected by two or three coats, and giving rise on their part, when they germinate, to the oophyte. This is the cycle of development m the Isosporous families of Vascular Cryptogams. In the Heterosporous families there are produced (always on the same plant) two different kinds of spore, differing very greatly in size — larger ??iega- spores and smaller microspores. The former produce female prothallia, that is, those which bear archegones only ; the latter male prothallia, bearing antherids only, or even antherozoids, without the intervention of a male prothallium or antherid. The spores are always endogenous structures, produced by free-cell-formation within a spore-case or sporange, which again, in the heterosporous families, is a megasporange or a 77iicrosporange, according as it contains megaspores or microspores. The sporanges are often collected into groups known as sori, and these may again be enclosed within 's>-^^Q\2\Ci\-3cci^^x's>, sporocarps ox conceptacles. Various kinds of vegetative propagation, similar to those of Flowering Plants, also occur on both oophyte and sporophyte ; and in certain ex- ceptional cases either the oophore or the sporophore may be entirely suppressed, constituting the phenomena of apogamy and apospory re- spectively. These will be described especially under Ferns, where they are of the most common occurrence. It may be useful in this place to compare the structure of the organs of reproduction and the phenomena of impregnation in Vascular Cryptogams with those of Phanerogams, and to endeavour to trace the requisite homologies,^ although these cannot be fully understood with- out some knowledge of the details of structure described under the separate families. It has been usual to compare the pollen-grain of Phanerogams with the antherozoid of Vascular Cryptogams ; but this is not strictly accurate. The essence of the act of fecundation consists in the coalescence of the protoplasmic contents of an active (male) and of a passive (female) cell. The protoplasmic endoblast or cell-contents in each case must, therefore, be homologous ; that is, the antherozoid with the protoplasmic contents of the pollen-grain which, in Flowering Plants, is brought into contact with the embryonic vesicle by means of the poUen- ^ Hofmeister was the first to point out these homologies in his Vergleic/i. Uniers. iiber Keiimmgu.s.xi'. der hoheren Kiyptogamen (see the Ray Society's translation, On the Germination, cr'c., of the Higher Cr}>ptoga>nia, p. 438). They have since been traced out more completely by Hanstein, Celakovsky, and others. 12 VASCULAR CRYPTOGAMS tube ; or probably the more correct homology is that of the nucleus of the antherozoid with the 'generative' nucleus of the pollen-grain. The most important difference between Cryptogams and Phanerogams lies in the mode in which this contact between the male and female elements is brought about. In Flowering Plants it takes place by the penetration into the embryo-sac, through the micropyle of the ovule, of the extension of the inner coat of the pollen-grain known as the pollen-tube, excited into activity by the viscid secretion of the stigma. The pollen-grain has therefore in the first place to be conveyed from the anther to the stigma ; and the various parts of the flower of Flowering Plants are all more or less concerned, directly or indirectly, with arrangements for facilitating the conveyance of pollen. In Flowerless Plants, on the contrary, contact between the male and female elements is effected by the protoplasmic contents escaping from the male cells and coming directly into contact with the oosphere in consequence of an independent pow^r of motion imparted to these naked masses of protoplasm (antherozoids) by the vibratile cilia with which they are provided. This impregnation always takes place in water or moisture, and no external agency is needed to bring it about. Hence the absence from all Flowerless Plants of any conspicuous compound organ analogous to the flower of Phanerogams. The true homology of the pollen-grain of Phanerogams appears to be with the microspore of the heterosporous Vascular Cryptogams, notwith- standing the fact that the contents of the microspore break up into a number of antherozoids, each capable of impregnating an oosphere : while the pollen-grain, as a rule, emits only a single pollen-tube. Here, as in other phenomena, we are guided to the true homology by compar- ing the highest Cryptogams with the lowest Phanerogams, the Gymno- sperms, which form a connecting link between them and Angiosperms. In all Gymnosperms, as in some Angiosperms, the pollen-grain is divided into several cells, only one of which (very much larger than all the rest) emits a short pollen-tube. The large fertile cell in the pollen- grain of Gymnosperms corresponds to the larger fertile portion of the microspore of Selaginellaceae, to the entire contents of the microspore of Marsileacese, to the terminal cell of the germinating filament in Salviniaceae, and to the antherid of the isosporous Vascular Cryptogams. In Angiosperms the sterile cells of the pollen-grain of Gymnosperms appear to be sometimes entirely suppressed, and the pollen-grain becomes unicellular. The contents of the pollen-grain of Angiosperms, together with the intine or inner coating of the grain, are therefore homologous with the antherid of Cryptogams. Seeing that the motile antherozoids have to be conveyed to the oosphere through the medium of water, it is convenient for both antherid and archegone to be freely VASCULAR CRYPTOGAMS 13 exposed to the action of moisture at the time of maturit}*. Hence, in all the isosporous Vascular Cryptogams, by far the largest portion of the product of germination of the hermaphrodite spore is the cellular tissue or prothallium (reduced to a comparatively small size in the Lycopo- diace^e and Ophioglossaceae), on which are borne both the antherids and the archegones. In the heterosporous Salviniaceae the male prothallium is reduced to a simple unseptated germinating filament ; and in Marsileaceae it altogether disappears. In Selaginellace^ it takes the form of the small sterile cells at one extremity of the microspore ; in Gymno- sperms, of the sterile cells of the pollen-grain ; in Angiosperms it is almost entirely suppressed. The contents of the pollen-grain corre- II. III. Fig. I.— I., male catkin of Zaviia (Cycadeae). II. III., antheriferous scale and pollen-sacs. stl- Fig. 2. — Peltate scsle oi EquisetJim, with sporanges sg. (After Sachs.) sponding to the antherozoids, the pollen-grain itself becomes homologous with the microspore, the pollen-sac or anther-cell to the microsporange. Even in external appearance the pollen-sacs of Coniferce and Cycade^ bear a striking resemblance to the sporanges of some .Vascular Crypto- gams. The modes of formation of the pollen-grains within the pollen- sac and of spores within the sporange, from an original archespore, are identical in their main features. Turning now to the female organs of reproduction, we must trace the homology of these back from the product of the union of the two elements, which in all the higher plants, whether flowering or flowerless, may be termed the oosperm, developing later into the embryo. In 14 VASCULAR CRYPTOGAMS Flowering Plants this is the product of the action of the contents of the pollen-grain on the protoplasmic embryonic or germinal vesicles ; in the higher Flowerless Plants, of the action of the antherozoid on the oosphere, or protoplasmic contents of the central cell of the archegone. The naked masses of protoplasm known as the germinal vesicles (or perhaps rather that one only which is ultimately fecundated) are therefore un- questionably homologous with the naked mass of protoplasm known as the oosphere. In Vascular Cryptogams the central cell which contains the oosphere is a portion of an archegone which is borne on a prothallium resulting from the germination of a spore or of a megaspore, as the case may be. To understand the homologies with the higher Phanerogams we must again have recourse to the intermediate Gymnosperms. In Fig. 4.— Female prothallium of Mar- silca, with archegone a and oo- sphere o. (After Hanstein.) Fig. ■\. — Fertilisation of Abies (Coniferae). /, pollen-grains ; fs, pollen-tube ; e, embryo- sac ; c, secondary- embrj-o-sac or corpusculum. (X 60.) this class the female elements are not directly developed in the in- terior of the embryo-sac, but within certain chambers produced within the embryo-sac, the secondary embryo-sacs or ' corpuscula, the homo- logues of the central cell of the archegone. In connection with them there have been detected other structures comparable to the neck and the canal-cells of the archegone. The object of the peculiar structure of the archegone and the deliquescence of the canal-cells being to facili- tate the passage of the motile antherozoids to the oosphere, these are no longer wanted when impregnation is effected by means of a pollen- tube. The archegone (except the central cell) is therefore reduced to a rudimentary condition in Gymnosperms, and disappears altogether in Angiosperms, where the embryonic vesicles are produced directly within VASCULAR CRYPTOGAMS 15 the embryo-sac, the homologue of the megaspore. The nucellus of the ovule must then be regarded as corresponding to the megasporange ; but it is difficult to carry the homology further. In Filices and Lyco- podiace^e an hermaphrodite prothallium usually exposes both kinds of sexual organ to the action of moisture ; in Equisetaceae we find a normal differentiation into male and female prothallia, but produced from one kind of spore only ; in the heterosporous families the differentiation is carried back to the spores and sporanges, and the female prothallium is altogether a subordinate product, and never has any separate existence apart from the megaspore, within which it is more or less concealed, only that part which bears the archegones being exposed. In Angio- sperms it has been suggested that we have a rudiment of the female prothallium surv-iving in the peculiar ' antipodal cells ' found within the embryo-sac in certain natural orders ; but the homology is doubtful. In the Selaginellaceae we find also the rudiments of two other structures which characterise the ovule of Flowering Plants. The sterile tissue which occupies the lower part of the megaspore in this order is probably the first appearance of the endosperm i albumen) which is found in the seed of a large number of Flowering Plants : the purpose in both cases being the same, to provide the embryo with nutritive material during the early stages of its growth. In all Phanerogams the young embryo is borne on a longer or shorter pedicel of cellular structure, the suspensor or pro- embryo, which, again, we find for the first time in the same order of Cryptogams. In all the isosporous Vascular Cr}'ptogams the sexual generation or oophyte has an independent existence distinct from the spore which produced it ; while in the heterosporous families the prothallium recedes more and more into the background, existing only within tht; megaspore ; and at the same time the male organs or antherids become more rudi- mentary in structure. In Gymnosperms the female prothallium and the antherids (as distinct from the antherozoids) have become much reduced, and in Angiosperms have completely disappeared. A\'hile, therefore, in Characese alternation of generations disappears by the suppression of the non-sexual generation which bears the spores, in Phanerogams the same result is brought about by an exactly opposite process, the sup- pression of the sexual generation or prothallium with its antherids and archegones, and the coalescence of male and female elements takes place within the non-sexually produced embryo-sac of the ovule, which corresponds to the megaspore. The life-history and general structure of the various organs in Vascular Cryptogams may now be described more in detail. The immediate product of the germination of the spore or megaspore i6 VASCULAR CRYPTOGAMS is always 2, prothallium, which is usually a green plate of tissue lying flat on the soil, very commonly lobed or reniform in shape, sometimes microscopic, but often quite visible to the naked eye, from ^ to ^ an inch in diameter, and constituting, with its organs of reproduction, the oophore, oophyte, or sexual generation. The prothallium usually disappears as soon as the non-sexual generation has firmly rooted itself in the soil ; but in Gymnogramme (FiKces) it attains a larger size, and continues its existence for a considerable time, producing a succession of reproductive organs. The oophyte never becomes differentiated into stem and leaves, as in the Muscineae, nor does it contain any vascular tissue. It usually consists of only a single layer of cells filled with chlorophyll, except a marginal cushion, where there are several layers. Here it puts out into the soil numerous colourless elongated cells, the organs of attachment, or rhizoids.^ among which, or scattered over the whole of the under surface and margin, are the archegones and antherids. True vegetative budding takes place but rarely on the prothallium ; but it sometimes, in certain Filices, exhibits apogamy, the sporophore springing directly from it, without the intervention of the sexual organs. In some Lyco- podiaceae and in the Ophioglossaceae the prothallium is subterranean, destitute of chlorophyll, and cylindrical or tuberous. In the Hymeno- phyllaceae (Filices) it is often filiform. In the isosporous families the prothallium is most commonly monoecious, less often dioecious. In the heterosporous families it is far less fully developed. That which arises from a megaspore is very small, formed within the spore, and at no period maintains an independent existence ; while that developed within a microspore is still more rudimentary. The archegones of Avascular Cryptogams are produced on the pro- thallium, usually on the under side of the cushion. Each archegone consists of a swollen basal portion or venter, and a neck, usually composed of four longitudinal rows of cells ; the venter is buried in the tissue of the prothallium, the neck alone projecting above it. The arche- gone originates from a superficial cell of the prothallium, which divides by a tangential wall into an inner and an outer cell ; the latter then develops, by further divisions, into the four rows of cells constitut- ing the neck, which is, therefore, always comparatively short. The inner cell puts out a protuberance between the neck-cells, which is first of all separated as the fieck-canal-cell, and below it a small portion is again separated from the lower larger cell as the ventral canal-cell ; the ' These organs are frequently termed root-hairs ; but it is better to confine this term to the epidermal appendages (trichomes) of the roots of Phanerogams and of the sporophyte generation of Vascular Cr}'ptogams, between which and true rhizoids there is a functional rather than a morphological homology. VASCULAR CRYPTOGAMS j; lowermost portion of the lowest cell remains of a comparatively large size, and is the central cell containing the oosphere. When mature, the two canal-cells deliquesce into mucilage, which swells up considerably, drives apart the four apical lid-cells or stigfnatic cells of the neck, and is ejected ; an open canal being thus formed to allow the access of the antherozoids to the oosphere, which always takes place in moisture, the ejected mucilage assisting also in this process. The antherids ^.y^^^^dcc as roundish papillae on the margin, or dispersed over the under surface of the prothallium ; in some cases they are im- l)edded in its tissue. Each antherid consists of a comparatively small number of cells : when mature the cell-walls are ruptured under water, and from each escapes a swarming antherozoid. The antherozoids are spirally coiled threads of protoplasm, the body of which is formed from the nucleus of the mother-cell, with a number of fine vibratile cilia on the anterior coils. There is generally attached to each anthero- zoid, as it escapes from its mother-cell, a vesicle of protoplasm contain- ing starch-grains, formed out of the cytoplasm of the mother-cell, which, adhering to one of its posterior coils, is dragged along with it during its swarming, but becomes detached before its entry into the neck of the archegone. In the heterosporous families the antherid is of very simple structure, and is either produced directly within the microspore, or after the preliminary formation of a few cells, which must be regarded as a rudimentary prothallium. The form and size of the non-sexual generation or sporophyte \?ixy within very wide limits, from the filmy, moss-like Hymenophyllace^ (Filices) to the arborescent tree-ferns (Fihces), and must be described more in detail under the various families. It arises in the archegone, from the oosperm or fertilised oosphere. The first effect of impregnation is that the oosphere invests itself with a cell-wall of cellulose, thus becoming the oosperm, which then divides into a small number of undifferentiated cells, in which condition it is known as the e7nbryo. In the earliest subsequent divisions of the embryo may be recognised the rudiments of the first root, of the first leaf or cotyledon^ and of the apex of the stem ; while at the same time a lateral outgrowth termed tho^foot is formed at the bottom of the venter, and draws from the prothallium the first nourishment for the young plant. The venter at first grows vigorously, enveloping the embryo, until this latter finally protrudes free, leaving the foot still attached to it for some time as a nutritive organ. The primary root soon disappears, and in some Hymenophyl- lacese, and in Salvinia and Psilotum, is not followed by others : but in the great majority of cases other true roots succeed in acropetal suc- cession, and the prothallium then disappears. The cotyledon always c iS VASCULAR CRYPTOGAMS remains small ; the first stem bends upwards, and other leaves of a more complicated structure appear on it. The roots of Vascular Cryptogams usually arise in acropetal succession on the stem (in some ferns on the leaf-stalk), and branch either mono- podially or dichotomously. There is never one preponderating root continucas in a downward direction with the main stem corresponding to the tap-root in Flowering Plants. They are distinguished from the roots of Flowering Plants by the lateral roots springing, not from the procambium. l^ut from the innermost cortical layer of the mother-root. They are abundantly covered with root-hairs, trichomic formations by means of which the nutritive materials are absorbed from the soil. They possess a true root-cap. Salvinia (Rhizocarpeae) and Psilotum (Lycopodiace^) are altogether rootless, as also are a few Hymenophyl- laceae (FiHces), the function of roots being performed by underground branches of the stem. The degree of development of the ste7?i varies within very wide limits. In the tree-ferns it is of erect habit, and attains great height and consider- able thickness. In many herbaceous ferns the internodes of the erect stem are altogether suppressed, while the underground portion forms an elongated rhizome. In the existing Lycopodiaceae, and in some Sela- ginellaceae the very elongated creeping stem is mainly above ground ; in the rootless forms, like Psilotum, branches of the stem bending down into the soil perform the function of roots. In some paludose species belonging to the Rhizocarpeae the stem is almost entirely suppressed, and in Salvinia the whole plant floats on the surface of the water. The mode of branching is either monopodial or dichotomous ; the leaves do not usually produce buds and branches in their axils, as in Flowering Plants. In all the larger species the stem displays a distinct differentiation of tissues into the three systems, fundamental, epidermal, and 'vascular' or fascicular. The so-called vascular bundles are closed, like those of Mono- cotyledons— that is, they contain no foimative cambium ; and they are usually but not always concentric, the phloem portion surrounding the xylem portion in the form oi 2i phloe7n-sheath. Each bundle, or a group of bundles, is again very frequently surrounded by a single layer of strongly sclerenchymatous cells belonging to the fundamental tissue, the vascular bundle-sheath, where it encloses a single, or plerome-sheath, while it surrounds a group of bundles. The prevalent, though not the exclusive form of thickening in the xylem is that of scalariform tra- cheides : true vessels formed from the coalescence of cells are rare ; in the phloem sieve-tubes are of common occurrence. Potonie holds that there is no sharp differentiation between the xylem and phloem portions VASCULAR CRYPTOGAMS 19 of the 'vascular' bundles of Vascular Cryptogams, and prefers for them the terms hadrome and leptome respectively. According to Van Tieghem, the secondar}' tissues, like those of Flowering Plants, proceed normally from two concentric generating layers — an external one in the cortex, forming bark outwardly and secondary cortex inwardly, and an inner one in the central 'vascular 'cylinder intercalated in the liber and in the xylem of the primary ' vascular ' bundles, producing secondary liber outwardly and secondary xylem inwardly. The epiderm is in most cases abun- dantly provided with trichomic appendages of various kinds. The size and form of the leaves are extremely various. In Lycopo- dium, Selaginella, and some other genera, they are very small, unseg- mented, and lanceolate, not unlike those of mosses, and form a dense imbricated clothing to the stem ; in Psilotum they are altogether rudi- mentary : in the Equisetaceae they are reduced to divisions or teeth of a membranous sheath ; in Isoetes (Selaginellaceae), Pilularia (Rhizo- carpese), and Phylloglossum (Lycopodiacese), they are long, narrow, and awl-shaped. In some ferns the barren and fertile leaves differ from one another in appearance, and especially in the degree of division of the lamina. In Salvinia they are of two kinds, one floating on the surface of the water and entire, the other submerged, very finely divided, and performing the function of a root ; in AzoUa (Rhizocarpeae) they are floating and bilobed. In some genera of Filices and their allies the leaves are quite entire : in the Hymenophyllaceae they are very delicate, consisting of only a single layer of cells, and in the smaller species closely resemble those of the foliose Hepaticse ; while in most ferns they are of considerable (in the tree-ferns of gigantic) size, with well-marked petiole, rachis, and lamina, and distinguished by the great extent to which the lamina is divided. In most cases (except the Hymenophyl- laceae) they are abundantly provided with stomates. The tissue beneath the epiderm consists of a parenchymatous mesophyll containing abun- dance of chlorophyll, the portion of which adjacent to the upper epiderm is frequently developed as palisade-parenchyme. This meso- phyll is permeated by ' vascular ' bundles or veins, which branch off from the cauline bundles, and are distinguished, in the majority of ferns, bv their dichotomous mode of branchino;, in contrast to the reticulate anastomosing in Dicotyledons, and the parallel arrangement in most Monocotyledons. Among Gymnosperms a similar arrangement is pre- sented by Salisburia and Stangeria. The floral metamorphosis of the leaves of Flowering Plants does not occur in Vascular Cryptogams, nor their special agglomeration round the organs of reproduction as in mosses. The mature sJ>ora?ige, theca, or spore-case, is usually a roundish c 2 20 VASCULAR CRYPTOGAMS capsule borne on a stalk, of small size and simple structure. Its morpho- logical value varies greatly, and will be referred to more particularly under the separate families. In the majority of Filicesthe sporanges are trichomic structures, and are collected into groups or sori, which are always located in connection with a ' vascular ' bundle on the under side or margin of the leaf. In the Marattiaceae they spring from a hypo- dermal mass of tissue. In the Ophioglossaceae a segment of a leaf is transformed into sporanges. In Selaginella and Lycopodium they arise from the growing point of the stem above the axil of a leaf. In Psilotum they are sunk in the extremity of branchlets of a peculiar form. In the Salviniaceae they are enclosed in receptacles or sporocarps, which are themselves modifications of divisions of the leaf. The mode of formation of the spores closely corresponds to that of the pollen-grains in Flowering Plants. The spore-forming tissue can always be traced back to a single cell or a row or layer of cells, the archespore, which may be dis- tinguished at a very early period from the remaining cellular tissue by the nature of its contents. From this proceeds the sporogenous tissue^ which afterwards becomes the mother-cells of the spores by perfectly regular divisions, the details of which differ in the different families. This is surrounded by one or more layers of cells, the tapetal cells or tapete, and the whole is enclosed in the wall of the sporange, itself composed of one or more layers of cells. In the heterosporous families the distinction between megaspores and microspores is manifested only at a comparatively late period in their development. In the iso- sporous families the spores are always strictly unicellular, very commonly elliptical or reniform in shape. The coat ahvays consists of two separ- able layers — an outer cuticularised exospore, often elevated into warts or other prominences ; and an inner endospore, composed of cellulose, w^hich bursts through the exospore on germination, Y>^oducmgt\\Q ger?n-fila??ienf, which develops by cell-division into the prothallium. In the mega- spores of the heterosporous families these are further protected on the outside by a third separable, greatly hardened layer, the epispore. The mode in w^hich the spores escape from the sporange differs in the dif- ferent families. A purely vegetative mode of propagation by means of gemmae or bulbils borne on the sporophyte occurs especially in Filices and Equisetaceae ; on the oophyte vegetative propagation is less common. The classification of Vascular Cryptogams is attended with consider- able difficulty. None of the systems as yet produced have much claim to be regarded as natural ; and, until some doubtful points are cleared up connected with fossil forms which may be links between existing families, the primary distinction into Heterosporo2(s and Isosporous VASCULAR CRYPTOGAMS 21 Vascular Cryptogams is so convenient, that we have decided to adhere to it, v/ithout dogmatising as to its permanent retention. In the boundaries of the families, again, there is equal room for diversity of opinion. "Whether to retain the Psilotese under Lycopodiaceae, and the Isoete^e under Selaginellaceae, and whether to regard the true Fihces, the Marattiaceae, and the Ophioglossaceae as constituting one, two, or three classes, are points on which there is much to be said in favour of classifications different from that which we have decided to adopt. Literature. Thuret— (Zoospores and Antherids) Ann. Sc. Xat., vol. xiv., 1850, p. 214; and vol. xvi. , p. 5. Hofmeister— Germination, Development, and Fructification of the Higher Cr)-pto- gams, Ray Soc, 1862. Schacht — Die Spermatozoiden, Braunschweig, 1864. Dippel— (Fibrovasc. Bundles) Ber. Deutsch. Naturf. u, Aerzte, 1865. Nageli u. Leitgeb — (Root) Nageli's Beitr. z. wiss. Bot. , 1867. Kny — (Prothallium) Sitzber. Ges. Xaturf. Freunde, Berlin, 1868. Millardet— (Prothallium) 1869. Russow — Vergleich. Unters., Petersburg, 1872. Janczewski- (Archegone) Bot. Zeit., 1872, p. 418. Goebel - (Sporangia) Bot. Zeit., 1880 and 18S1. Sadebeck— Die Gefasskryptogamen, 1880. Prantl— Morphologic der Gefasskrypt., 1881. Van Tieghem — Bull. Soc. Bot. France, 1883, p. 169. Potonie — (Vase. Bundles) Jahrb. Bot. Gart. Berlin, 1883. Leitgeb- (Spores) Ber. Deutsch. Bot. GeselL, 1883, p. 246. Celakovsky — Pringsheim's Jahrb. f. wiss. Bot., xiv., 1884, p. 291. Bower — (Leaf) Proc. Roy. Soc, xxxvii., 1884, p. 61. Rabenhorst — Cr}-pt. Flora Deutschland, Vase. Crypt., by Luerssen, 1884-88. De Bar)'— Comparative Anatomy of Phanerogams and Ferns, 1884. Klein— (Dehiscence of Sporange) Bull. Soc. Bot. France, 1884, p. 292. Leclerc du Sablon — (Spores) Ann. Sc. Xat., vol. ii., 1885, p. 5. Campbell— (Antherozoids) Ber. Deutsch. Bot. Gesell., 1SS7, p. 120. Baker — Handbook to Fern Allies, 1887. HETEROSPOROUS VASCULAR CRVPTOGAMS. Class I. — Rhizocarpese, The Rhizocarpese or Hydropterideae constitute a class composed of only a small number of genera, none of which includes more than a few species. They grow submerged in or floating on water, and derive their name from the circumstance that the non-sexual organs of propagation are produced in the radicular region, or near the base of the leaves. 22 VASCULAR CRYPTOGAMS The spores are of two kinds, one of which is many hundred times larger than the other. The larger spores, or megaspores, produced in f/iegas/>oraNges, are female ; the smaller spores, or microspores, produced ^)^VinT>-^ Fig. 5. — Pihdaria glohdifera L., with Fig. 6. — Marsilea qjiadrifolia L., with fructlfi- fructification, natural size. (After cation, natural size, and fructification en- Luerssen.) larged. (After Luerssen.) in microsporanges, are male. The megaspore is not completely spherical, but has a distinct apical protuberance, which at the period of maturity is enveloped in a thick firm layer termed the epispore, formed by the RHIZOCARPE.-E 23 hardening of mucilage derived from the disorganisation and deliques- cence of a portion of the contents of the sporange. The female prothal- lium is formed within the apical papilla of the megaspore, and is exposed by the bursting of the enveloping epispore. It never completely frees itself from the megaspore, and is usually altogether destitute of chlorophyll. It bears one or more archegones, differing from one another in smaller points of structure in the different genera. The microspores do not give birth to a male prothallium, nor even to antherids, in the sense in which the terms are employed elsewhere in Fig. 7. — Salvinia nutans L. A and B natural size, the latter with two aerial leaves and sub- merged fertile leaves ; C, two sporocarps, slightly magnified and diagrammatic, one con- taining a few megasporanges, the other a large number of microsporanges ; D, section of empty sporocarp, slightly magnified. (After Luerssen.) Vascular Cryptogams ; the contents divide more or less directly into the parent-cells of the antherozoids, which, accompanied by peculiar vesicles attached to them, reach and impregnate the oosphere contained in the central cell of the archeerone. The external form of the sporophyte or non-sexual generation varies widely in the different genera. The growth of both stem and root is always the result of successive divisions from a single apical cell. The stem is extremely abbreviated in Salvinia (Schreb.) and Azolla (Lam. ) ; procumbent and creeping in Marsilea (L.) and Pilularia (L.). It is traversed VASCULAR CRYPTOGAMS V ■-^->"^^:iii,\v by closed concentric ' vascular 'bundles, each surrounded by its bundle- sheath, and the branching is always monopodial. The roots — except in Salvinia, which is rootless — are fil)rous, are furnished with a root-cap, and branch monopodially. The leaves also vary greatly in form. In Pilularia they are erect, cylindrical, and setiform : in Marsilea (L.) the lamina consists of several distinct leaflets at the extremity of a more or less elongated petiole. In both these genera the vernation is circinate. In Azolla the leaves are deeply bifid. Salvinia is remarkably hetero- i^hyllous. A\'hile the majority of the leaves retain an ordinary leaf-like habit, others develop into coriaceous scutiform structures, while others again divide into a number of capillary segments, which perform the function of roots, and at the same time bear the non-sexual propagating organs. The fructification is of a more complicated structure than in other classes of Vascular Cryptogams. In Salvinia it springs from the lower teeth of the submerged leaves ; in Azolla from the pendent section of the deeply bipartite leaf, or rather of one particular leaf: in Pilularia it stands beside and beneath the leaves ; in Marsilea (L.) on the under side of the petiole, or of the base of the leaf itself. The Rhizo- carpeae are always moncecious, the two kinds of sporange being produced on the same individual, and usually in close proximity. The structure and degree of complexity of the fructifi- cation differ in the different genera. The sporanges are always associated together in groups. Each of these groups, known as 2iSorus or sporocarp, is a closed capsule-like chamber, which is of epidermal or trichomic origin, its wall or indusitim^ often considerably hardened, being an extension of the epiderm. Each sporocarp is regarded by Celakovsky as the homologue of the integumented ovule of Flowering Plants. In the Salviniaceae the sporocarp is unilocular; in the Marsileacese it is plurilocular, and the wall indurated into a hard shell. Each sporocarp may contain sporanges of one kind only or of both kinds ; in the former case male and female sporocarps are often associated together in Fig. 8. — Salvhiia natans L. Young plant still attached to the prothal- lium/r, and megaspore^/. /^, scuti- form leaf ; / and //, first and second leaves ; L' and L" , later aerial, and 7t/, submerged leaf of the first whorl. (After Pringsheim, x 20.) RHIZOCARPE.^ 25 groups. The megasporanges are often considerably larger than the microsporanges. In the early stages of their development no difference is exhibited between the megasporanges and microsporanges. In both cases the sporange originates in a papilla placed on the placenta^ which divides first into an upper and a lower cell, the latter developing, by repeated transverse septation, into the pedicel, the former into the body of the sporange, and dividing ultimately into a large central tetrahedral archespore, surrounded by a layer which almost immediately breaks up into two layers of tapetal cells or mantle-layers. The archespore further divides into sixteen spore-mother-cells, and each of these into four special spore-cells arranged tetrahedrally. A difference is now mani- fested according as the sporange is to develop into a mega- or a micro- sporange. In the latter case each of the sixty-four cells develops into a microspore, while the tapetal cells become disorganised, and changed into the frothy mucilage which subsequently hardens and encloses the spores. In the former case only one of the sixty-four cells develops into a megaspore, growing rapidly at the expense of the others, and ultimately filling up the cavity of the sporange. The remaining sixty- three spore-cells, as well as the tapetal cells, become disorganised, and deliquesce into a frothy mucilage which envelops the ripe megaspore, ultimately hardening into the epispore, which splits to allow the emergence of the prothallium. In Azolla the mucilage of the microsporanges forms the peculiar massulcz which will be described later. A more detailed description requires the division of the Rhizocarpe^ into the two orders Salvhiiacece (Salvinia and Azolla) and Marsileacete (Marsilea and Pilularia), which are, perhaps, not in reality very nearly related to one another. Order i. — Salvixiace.e. The female prothallium of Salvinia is formed within the apical papilla of the megaspore. The protoplasm in this papilla appears to separate from that of the rest of the spore, and then breaks up by free-cell-formation into several portions, which remain for a time unclothed with cellulose ; subsequently they secrete cell-walls, and form a tissue, which breaks through the cell-wall of the papilla, and forces its way through the epi- spore, which splits into a three-lobed body. The prothallium, when it first emerges from the epispore, has a somewhat triangular form, with an elevated ridge along its median line, and two wing-like appendages, subsequently forced apart by the growth of the embryo, which hangs down on each side of the spore. It contains a considerable amount of 26 VASCULAR CRYPTOGAMS chlorophyll, but never loses its connection with the megaspore, even after the commencement of the germination of the sporophyte. The first archegone makes its appearance on the elevated dorsal ridge of the prothallium, and subsequently two others are formed, one on each side of the first. If one of these is fertilised no more archegones are pro- duced, and the prothallium ceases growing. But if no impregnation has taken place the prothallium continues to grow, and produces from one to three additional rows, each consisting of from three to seven archegones. In Azolla the prothallium has the form of a slightly convex disc, consisting, in its central part, of several layers of cells, at the margin of only one. A single archegone is first formed, near the centre of the prothallium. If this Fig. 9. — Sah'biia nataiis. Longitudinal section through megaspore and prothallium. a, wall of sporange ; b, epispore, formed of hardened mucilage ; c, coat of spore ; d, diaphragm separating prothallium from spore-cavity ; pr, prothallium ; ;;/, neck of archegone ; /, //, first two leaves of embryo ; s, scutiform leaf or cotyledon. (After Pringsheim, x 70.) Fig. 10. — Archegone of Salvinia fiaians in three stages, a, b, c, divisions in the neck-cells , d, neck-canal-cell ; e, oosphere ; /i, neck-cells. (After Pringsheim, x 150.) is fertilised, no others are formed ; if not, it is followed by a few others. The archegone of Salvinia is a nearly globular cavity, its venter being completely buried in the tissue of the prothallium. The central cell is at first somewhat elliptical, its axis lying obliquely to the surface of the prothallium. Its apex is at first covered by four cells belonging to the epiderm, arranged in the form of a cross. Each of these four neck-cells divides by transverse septa into a row of three cells, the four rows thus forming a short neck. The large central cell now elongates upwards and forces its way between the lowermost four cells of the neck, and its RHIZOCARPEyE 27 conical point becomes cut off by a septum, forming the neck-canal-cell. Below this a second very small portion of the central cell is again cut off to form the ventral canal-cell^ so that the canal now consists of two cells. These two cells become transformed into mucilage, which escapes by forcing apart the four apical or stigmafic cells, leaving an open canal In the meantime the protoplasm of the large basal portion of the central cell has become transformed by contraction into the oosphere. The archegone is now ready for impregnation, the antherozoids reaching the oosphere through a funnel-shaped depression in the epispore and the open canal. After fertilisation the canal again closes up by the expan- sion of the stigmatic cells. The archegone of Azolla resembles that of Salvinia in all essential points. The male prothallium of Salvinia is reduced to a mere rudiment. The microspores lie imbedded in a mass of hardened, granular, frothy mucilage, formed by the disorganisation of the tapetal cells. They do not escape from this mucilage, but the endospore of each develops into a tubular fila- ment which pierces through the muci- lage and the wall of the sporange. The extremity of this filament which projects outside the sporange is curved, and becomes cut off by a septum. The lower and larger of the two cells thus formed is regarded as a rudimentary prothallium ; the termi- nal cell, which again divides into two, as a rudimentary antherid. The protoplasm of each of the two antheridial cells divides into four, and each of these eight masses of protoplasm escapes as an antherozoid. Each antherozoid is a corkscrew- like coil of protoplasm, bearing vibratile cilia of great length at its broader extremity. To the same extremity is attached a vesicle, com- posed of a portion of the protoplasm of the antheridial cells which was not used up in the formation of the antherozoids, and which does not leave the antherozoid during the period of its 'swarming.'" The development of the multicellular embryo from the fertilised oosperm has been very carefully followed out in Salvinia. The first segmentation is by a nearly vertical wall (at right angles to the surface of the prothallium) into two somewhat unequal portions, each of which Fig. II. — Salvin'a nutans. A, micro- sporange, with microspore-tubes st. (x 100.) B, microspore-tube (x 200) with closed, C with empty antherid. D, antherozoids ( x 6co). (After Pringsheim.) 28 VASCULAR CRYPTOGAMS again divides by a septum nearly at right angles to the first one. Further divisions then take place. Out of the posterior of the first two segments (the one immediately beneath the mouth of the archegone) is formed the /^^/ of the young plant, by which it is attached to and derives its nutriment from the prothallium. From the anterior of these two seg- ments is derived a peculiar foliar structure, differing from all the subse- quent leaves, the cotyledon or saitifonn leaf, by the growth of which the terminal bud of the stem becomes directed downwards. No root what- ever is produced. Azolla is stated to have a second cotyledon. Both stem and root (in Azolla) are developed from a single apical cell, which is rounded in front and pointed below. The primary meristem-layers are differentiated, as in Flowering Plants, into plerome, periblem, and dermatogen. The mature sporophyte differs considerably in appearance in the two genera, but always floats on the surface of the water. The very short stem is erect or horizontal, and the branching of both stem and root (in Azolla) is monopodial. The root, stem, and leaf-stalk are each traversed by a single concentric ' vascular ' bundle of simple structure, containing spiral and annular tracheides. The leaves of Azolla are very crowded, and are placed in two rows on the dorsal side of the stem ; but in some species they have the appearance of standing in four rows. They are of delicate membranous texture, and are always deeply bifid, one lobe being submerged and the other floating. The floating lobe of each leaf has a remarkable cavity, covered by a double epidermal layer, with the excep- tion of a narrow orifice which opens into the cavity. This cavity is formed during the growth of the leaf by a more rapid growth of the epiderm than of the subjacent tissue, and is itself clothed with an epi- dermal layer. The cavities are frequently occupied by well-developed colonies of Nostoc-filaments. Salvinia is remarkably heterophyllous (see figs. 7, 8). The first leaf of the young plant is the scutifonji or peltate /f«/ already mentioned, which is produced near the base of the stem. It is coriaceous in texture and sagittate in form. Next are pro- duced, also singly, two ovsite aerial leaves. All the subsequent leaves are arranged in whorls of three, two of which are aerial, with flat, ovate, or orbicular lamina, floating on the surface of the water ; while the third ox submerged leaf dit once, branches into long slender filiform segments, which hang down into the water and perform the function of roots. The leaves of adjacent whorls are placed alternately, so that the mature plant has two rows of ventral submerged, and four rows of dorsal aerial leaves. Each leaf has a single definite apical cell in Salvinia, but not in Azolla. The leaves of both genera are furnished with stomates, which, according to Strasburger, differ considerably, both in structure and RHIZOCARPEJ£ 29 appearance, from those of Flowering Plants. Those of Salvinia are re- markably small, and are inserted about halfway up the epidermal cells, which are eight or nine times their height. Air-pores occur also in the submerged leaves. The very simple roots of Azolla are of endogenous origin. The root-cap originates from a single cell ; in A. Caroliniana (Willd.) the cap is eventually thrown off, leaving the root-tip naked. The sporanges are enclosed in unilocular sporocarps, formed two together or in larger numbers ; in Salvinia on the youngest teeth of the submerged leaves, in Azolla on the pendent submerged lobe of the deeply bifid leaves, and only on the lowermost leaf of each shoot. The leaf-segment which is destined to become fertile first of all develops into a columel or placenta^ to which the sporanges are" attached. An annular wall, the rudiment of the in- diisium^ then becomes elevated from the base of the columel, eventually overtops its apex, closes up, and thus forms the wall of the sporocarp. The sporocarp of Salviniaceae is therefore a metamorphosed portion of a leaf, and corresponds to a sorus in the Hymenophyllaceae (Filices), with the difference that in the latter the envelope remains open in the form of a cup, while in the former it closes completely over the sorus, as in Cyathea (Filices). The in- dusium is much more strongly developed than that of ferns, and completely envelops the sorus ; it consists of two layers of cells, the walls of which are, in Azolla, strongly lignified in the upper part. Each sporocarp contains one kind of sporange only ; but both kinds always occur on the same individual, and may even spring from the same metamorphosed leaf. In Salvinia the megasporanges are considerably larger than the microsporanges, and the number of the latter in a sporo- carp is greater (see fig. 7). In Azolla the number of microsporanges in a sporocarp is about forty, while the female sporocarps contain only a single megasporange, and consequently only a single megaspore, en- veloped first in the wall of the sporange, and then in the greatly hardened indusium. The microsporanges are nearly globular capsules, with long slender pedicels, the wall consisting, when mature, of a single layer of cells. The megasporanges are pear-shaped, with much shorter and Fig. 12. — Fertile shoot oi Azolla filicidoides Lam., with two female sporocarps, « ( x 27). (After Strasburger.) 30 VASCULAR CRYPTOGAMS stouter pedicels, and arise from the apex of the columel. In the forma- tion of the pedicels of the megasporanges longitudinal cell-division takes place, as well as transverse. The mode of formation of the spores within each kind of sporange has already been described in general terms, after the preliminary separation of a single external layer of cells which develops into the wall of the sporange. The sixty-four micro- spores appear to be disposed without any arrangement in the cavity of the microsporange. A large nucleus lies at the end of the megaspore which is nearest the apex of the sporange. Before fertilisation both kinds of sporange become detached from their pedicels, and are carried Fig. 13.— Massula of Azolla Caroliniana Willd. (X240). (After Strasburger.) up to the surface of the water in the spring by the surrounding masses of Algce. The epispore then splits above the apex of the megaspore into three lobes, between which the emerald-green prothallium forces itself, and impregnation is effected. In Azolla the epispore assumes a still more striking form. In the microsporanges it has the appearance of a large-celled tissue, and breaks up into two or more spherical masses called massulce, each of which envelops a number of microspores, and has a distinct coat. In some species, but not in all, the surface of these masses is covered v.-ith hair-like appendages, barbed at the apex, the glochids, by means of which, after emerging from the sporange, and when floating on the surface of the water, they attach themselves to the RHIZOCARPEAl 31 floating megaspores. The roundish megaspore, which does not nearly fill up the sporange, is completely covered by a very thick warty laver of hardened frothy mucilage, its epispore, which projects far above the apex, and separates, in its upper part, into either three or nine large pear-shaped masses of the same substance, terminating in a tuft of fine threads. These bodies constitute difloatitig apparatus for the megaspore, the fine threads floating on the surface of the water, and suspending beneath them the fioat-corpiiscles^ either three in number or more numerous, containing abundance of air-cavities, and the megaspores, to which the microspores are attached by their glochidiate processes. The two genera of Salviniaceae, Salvinia and Azolla, each include but a small number of species, all annual plants, widely distributed over the globe, especially in its warmer regions. Those of Azolla form green or red floating patches of considerable size, with the habit of a Junger- mannia. No economical application is known of either genus. Order 2. — Marsileace^e. The female prothallium attains here a much smaller degree of development than in the Salviniaceae. It arises within the apical papilla of the megaspore, the protoplasm of which breaks up into several cells, which remain for a time unclothed with cellulose, and only subsequently constitute a tissue containing a small quantity of chlorophyll. Even after this the prothaUium still remains for some time completely enclosed within the apical papilla of the megaspore, being covered by the epi- dermal layers of the apex of the spore itself, and shut off from the spore-cavity within and below by a diaphragiii which is attached to the internal coat of the spore. By the further growth of the prothallium the epidermal layers of the apical papilla are broken through, and the dorsal ridge of the prothallium projects into the fi/miel formed by the absence at this spot of the thick outer layers of the epispore. The diaphragm subsequently arches convexly, and the prothallium is pushed further outwards, but still lies as a hemispherical mass in the funnel- shaped opening. In those species which have hitherto been examined each prothallium produces only a single archegone. Even before the prothallium breaks through the megaspore, the large central cell may be recognised in it, covered only by four cells arranged in a cross, which form at the same time the apex of the prothallium. From these are developed the more or less projecting neck and the stigmatic cells of the archegone. As in Salviniaceae, a neck-canal-cell is separated from the central cell, which pushes up between the neck-cells, as well as a smaller ventral canal-cell ; 32 VASCULAR CRYPTOGAMS the lower and larger portion of the protoplasmic cell-contents contract- ing into an oosphere. If the archegone remains unfertilised the prothal- lium continues to grow into a comparatively large chlorophyllous structure with rhizoids. The male prothalliuni and antherids are reduced to a still more Fig. 14. — 31arsilea salvatrix L. Longi- tudinal section through megaspore, pro- thallium, and embryo. «;«, starch grains ; z, inner ccat ; ex, epispore ; c, space beneath diaphragm ; pt, prothal- lium ; zc7z, its rhizoids ; «, archegone ; /, foot ; TV, root of embryo ; b, coty- ledon ; si, mucilaginous envelope of megaspore. (After Goebel, x 60.) ^c^ « 0)^ :^%:-. Fig. 15. — Marsilea salvatrix. A, prothallium j>t, projecting from ruptured coat r of mega- spore ; si, layers of mucilage forming funnel, with antherozoids. B, vertical section of prothallium pt ; 0, oosphere ; a, stigmatic cells. (After Goebel, greatly magnified.) rudimentary condition than in the Salviniacese. The contents of the microspore divide into three cells, one of which (the prothallium) remains sterile, the other two constituting the antherid. The contents of each of these two cells again divide into sixteen antherozoid-mother- cells. From the nucleus of each of these is formed an antherozoid ; RHIZOCARPEyE 33 these bodies are therefore developed entirely within the microspore, while the microspores themselves are set free completely from the sporange. As in the Salviniaceae, the whole of the contents of the mother-cell is not used up in the formation of the antherozoid ; a por- tion remains behind in the form of a roundish turbid lump consisting of protoplasm and starch-grains, which gradually becomes clearer, and attaches itself, in the form of a vesicle, to the antherozoid, which in Pilularia becomes soon detached, but in Marsilea remains attached to the antherozoid during the greater portion of the period of ' swarming.' When the antherozoids are mature the exospore of the microspore bursts at its apex, and the endospore swells up into a hyaline bladder, Fig. i6. — Pihdaria globiilifera'L.. Longitudinal section of megaspore. a, coat of spore ; b, c, d. the three layers of the epispore. (After Luers- sen, magnified.) Fig. 17. — Marsilea salvatrix. Micro- spore discharging antherozoids. ex, exospore ; dl, endospore ; zz^ anthe- rozoids ;_j% their vesicles with starch- grains. (After Goebel, X350.) which finally bursts to allow of the escape of the antherozoids with their vesicles. In Pilularia the antherozoid consists of only four or five coils with a few vibratile cilia ; in Marsilea it is of considerable length, the shape of a corkscrew, and consists of twelve or thirteen coils, the vibra- tile cilia being also of great length. The antherozoids collect, in large numbers, in the funnel-shaped depression of the epispore of the mega- spore above the prothallium (see fig. 15), and force themselves, through the neck of the archegone, to its central cell. In its early stages the development of the oosperm or impregnated oosphere corresponds to that of Salviniaceae. After becoming invested with a cell-wall of cellulose, the first segmentations give rise to the 34 VASCULAR CRYPTOGAMS parent-cells of the first root, of the young stem, of the first leaf or cotyledon, and of the foot by which the young embryo is attached to the prothallium. In Marsilea a second cotyledon is formed from the fourth octant of the lower half of the embryo. The layer of tissue surrounding the central cell becomes double after impregnation ; a few grains of chlorophyll are formed in it, and its outer cells develop into long rhizoids, which are especially luxuriant if no fertilisation has taken place. The sporophyte of the Marsileaceas differs very widely in external form in the two genera ; but its internal structure agrees in its essential features with that of the Salviniaceae. The stem, root, and leaves all originate from a single apical cell, which always divides into three rows. The stem is procumbent on damp soil or at the bottom of stagnant water, and is traversed by a single central ' vascular ' cylinder filled with fundamental tissue, each bundle consisting of a central xylem with spiral or stalariform tracheides, surrounded by a phloem with large sieve-tubes and sieve-plates, and the whole enclosed in a brown sclerenchymatous bundle-sheath, composed of a single layer of cells with wavy lateral walls. A single ' vascular ' bundle traverses each root and leaf-stalk ; in the lamina of the leaf of Marsilea this branches into a dichotomous venation. The fundamental tissue abounds, in both genera, in large schizogenous intercellular cavities, as is usually the case with water- plants. Those of ^Marsilea form a complete intercommunicating system. In those of Pilularia are remarkable spiral hairs. The leaves develop basifugally, as in Salviniacese ; they are formed in two alternating rows . on the dorsal side of the stem ; but, as in Salviniaceae, it is not every segment of the stem that produces a leaf. In this respect the Rhizo- carpese agree with Filices, and differ from Equisetaceae and Muscineas. The leaves are circinate in vernation, resembling in this respect true ferns only. Tannin-sacs occur in the petiole. In Marsilea (see fig. 6) all the leaves except the first, which is filiform and destitute of a lamina, have a very long slender petiole and a four-lobed lamina ; they are larger when growing in water than on dry land. M. quadrifolia (L.) has stomates on both surfaces of the aerial, on the upper surface only of the floating leaves. The stomates are depressed in the tissue of the leaf by the growth of the adjoining epidermal cells over the guard-cells. The mesophyll of the aerial leaves is characterised by the presence of rows of sclerenchymatous cells. In Pilularia the petiole is elongated and quill- like, and entirely destitute of a lamina (fig. 5). T\\^ sporocarp or conceptacle of the Marsileaceae is an even more complicated structure than that of the Salviniaceae. In Pilularia it is a roundish, shortly-stalked capsule springing from the axil of a leaf-stalk RHIZOCARPE.E on the procumbent stem. According to Juranyi, each sporocarp is the result of the coalescence of two segments of bifid leaves. The wall of the sporocarp is very thick and hard, and consists of several layers of cells forming a sclerenchymatous tissue. It is divided by vertical walls into compartments, var)4ng from two to four in the different species. Each compartment has, at least in its young state, an opening at the apex, and is therefore not of endogenous origin, but rather a depression in the surface. In each compartment there is, on the side which forms its outside wall, a cushion-like placenta, formed from superficial cells, and resting on a ' vascular" bundle. To this placenta are attached a number of stalked sporanges of both kinds, constituting a sorus \ the megasporanges are chiefly below, and the microsporanges above. The remainder of each compart- ment is occupied by a delicate thin-walled parenchyme. When mature the sporocarp splits from the apex downwards into as many valves as it has compartments ; and each sporange dehisces by the expansion of the gelatinous mass resulting from the dissolu- tion of the tapetal cells. The sporocarps of ^larsilea are capsules with somewhat the shape of a bean, a longer or shorter pedicel, and a very hard sclerenchymatous wall. They spring, usually in clusters, from the petiole of an ordinary leaf. The pedicel runs along the dorsal edge of the sporocarp, and gives off lateral veins right and left which branch dichotomously and run to the ventral edge. The ripe sporocarp has a bilaterally symmetrical structure, and is divided by transverse walls into two rows of compart- ments, each of which has, when young, a narrow opening on the ventral side. Each compartment contains a single sorus, consisting of a few megasporanges in the centre, with a larger number of microsporanges on each side. As in Piiularia, a large portion of the cavity of each compart- ment is occupied by a succulent parenchyme. The development of the sporanges commences, in both genera, with the swelling up of some of the epidermal cells of the part which ultimately becomes the placenta. These cells divide several times D 2 Fig. i8. — Transverse section of sporocarp o{ Piiu- laria globuli/era. mi, microsporanges; ma, megasporanges ; e, wall of sporocarp ; g, paren- , chyme. (After Goebel, magnified.) 36 VASCULAR CRYPTOGAMS obliquely — not horizontally, as in Salviniacese — into three rows of seg- ments, until ultimately a convex septum cuts off a triangular apical cell, which at length becomes the tetrahedral archespore. From this is separated the mantle-layer of tapetal cells ; further divisions take place both in these and in the rows of cells of which the wall of the sporange is composed, and the archespore divides by successive bipartitions into sixteen spore-mother-cells, each of which produces four spores in the ordinary way. The pedicel of the sporange consists at first of three rows of cells, the number being subsequently increased by further longitudinal divisions. The tapetal cells become gradually disorganised, and form a granular mucilage, filling up the interstices between the mother-cells of the spores, which is subsequently employed in the production of the epispo?'e or gelatinous envelope of the spore. The differentiation of the two kinds of spore now commences. In the microsporanges all the sixty-four microspores reach maturity, each special mother-cell or rudi- mentary spore becoming invested, while still within the mother-cell, with its permanent cell-wall, while the walls of the sixteen mother-cells dis- appear. In the megasporanges, on the other hand, one of the four special mother-cells in each of the sixteen tetrads displays at first a greater vigour of growth than the other three. Of these sixteen sister- cells fifteen gradually become abortive, only one reaching maturity and developing into a perfect megaspore. During their development and disappearance all the rudimentary spores are furnished with spiny pro- tuberances, by which they are attached to one another. As the mega- spore increases in size its coat becomes hard and brown ; and it is ulti- mately invested by a gelatinous epispore consisting of three distinct layers (fig. i6). The innermost of these is a mucilaginous coat, which is often folded, and ultimately forms a papilla above the apex of the mature spore. Outside this is a thicker layer of a soft prismatic sub- stance, and external again to this a third still thicker but less clearly organised envelope. The two outer layers are wanting at the apex of the spore, where there is a funnel-shaped depression exposing the papilla belonging to the innermost layer of the epispore. Down this/////;/.?/ the antherozoids pass to impregnate the oosphere within the archegone pro- duced on the prothallium within the apical papilla of the megaspore. The processes by which both kinds of spore escape from the very hard shell of the sporocarp are very remarkable. In Pilularia globu- lifera (L.) the ripe sporocarp lies above or beneath the surface of the damp soil. It splits from its apex downwards into four valves, and exudes a tough hyaline mucilage derived from the parenchymatous tissue within each compartment. This mucilage accumulates on the ground ; and into it both kinds of spore escape after the rupture of the RHIZOCARPE.-E ^7 sporanges. Fertilisation takes place within the drop of mucilage, which then gradually disappears, and the impregnated megaspore lies on the damp ground, to which it becomes attached by the rhizoids put out from the prothallium until the first root of the embryo penetrates into the soil. In Marsilea the processes are somewhat similar. The exces- sively hard, almost stony, shell of the sporocarp gives way slightly at its ventral edge as it lies in water, and the water penetrates into the interior. This causes the suc- culent parenchymatous tissue in each compartment to swell up, and splits the shell along the whole of the ventral edge into two valves. Between these valves the contents are gradually forced out; the com- partments still remain closed, each enclosing a sorus, and are attached in two rows to the cartilaginous cushion or sorophore which ran along the ventral edge of the spo- rocarp, and which now becomes detached at one end, and ex- posed in the form of a string many times longer than the sporo- carp itself ; by the absorption of water it has increased enormously in size, to something like 200 times its original dimensions, and the sori are thus placed at a con- siderable distance from one an- other. Ultimately the walls of the sori or original compartments of the sporocarp disappear ; the walls of the sporanges burst, both kinds of spore escape, and fertilisation is effected on the damp soil. All the species of both genera of Marsileaceae are marsh or aquatic perennial plants, mostly natives of the warmer temperate and tropical countries. The number of species of Pilularia is small, of ^^larsilea about forty. The leaves of Marsilea, when growing in the air, display a sensitiveness to light, folding up in the evening and expanding in the morning, similar to those of many Leguminosae and other Flowering Fig. 19. — Sporocarp of Marsilea salvatrix. A, transverse section. B, swollen and bursting, sho.ving sorophore (x2i). C, sporocarp (natural size), with sorophore fully extended, and sori attached. D, section of sorus ( x 6) ; ids, indu- sium ; niik, microsporanges ; mak, megaspo- ranges. (After Hanstein.) 38 VASCULAR CRYPTOGAMS Plants. The sporocarps of M. Drummondii (Br.), and probably of some other species, are eaten- by the natives of Australia under the name of nardoo. Literature. Bischoff — Die Rhizocarpeen unci Lycopodiaceen, Nuremberg, 1S28. Mettenius— Beitr. zur Kenntniss cier Rhizocarpeen, 1846; Linntea, 1847, p. 260; and Beitr. zur Botanik, Heft I, 1853; Plantae Tinneanae. Meyen — Nov. Art. Acad. Caesar-Leopold., vol. xviii. , pt. i, p. 253. Hofmeister— Ueb. Keimung der Salvinia, Abhandl. Sachs. Gesell. Wis?. 1857, p. 665. Pringsheim— (Salvinia) Jahrb. f. wiss. Bot., vol. iii., 1863, p. 484. Hanstein— Ueb. eine neuhollandische Marsilia, Monber. Berl. Akad., 1862, p. 183 ; Befruchtung u. Entwickelung der Marsilia, Jahrb. f. wiss. Bot., vol. iv., 1865, p. 107 ; Pilularice generatio cum Marsilia comparata, Bonn, 1866. Braun— (Marsilia and Pilularia) :\Ionber. Akad. Wiss. Berlin, 1870, p. 653, and 1872, p. 668. Russow — Vergleich. Unters., Petersburg, 1872 ; and Hist. u. Entwick. d. Sporen- frucht V. Marsilia, Dorpat, 1877. Strasburger— Ueber Azolla, Jena, 1873. Juranyi — Ueb. d. Entwick. d. Sporangien u. Sporen v. Salvinia, Berlin, 1873 ; and (Pilularia) Sitzber. Ungar. Akad. Wiss., 1879 (see Bot. Centralbl., vol. i., 1881, p. 207). Berggren — (Azolla) Rev. Sc. Nat., 1 88 1, p. 21. Heinricher — (Sporesof Salvinia) Sitzber. Akad. Wiss. Wien, vol. Ixxxv., 1882, p. 494. Goebel — (Pilularia) Bot. Zeit., 1882, p. 771. Class II.— Selaginellaceas. This class is composed of two genera only, Selaginella (Spring) and Isoetes (L.), resembling one another in the general facts of their life- history, but differing widely in external appearance, and each consti- tutmg a monotypic order. We have, again, as in Rhizocarpeae, two kinds of spore; the megasporanges and microsporanges are of very similar appearance, and are produced in connection with the leaves. The female prothallium, produced within the megaspore, is a more completely endogenous structure than in any other class of Cryptogams, and is altogether destitute of chlorophyll. From the occurrence in both genera of a foliar structure known as the lignle, the term ' Ligulatae ' is sometimes given to the class ; but the character is unsatisfactory, and it will be best to treat the two orders Selaginellece and Isoctece sepa- rately. SELA GIXELLA CE^ 39 Order i. — Selaginelle-^. In the genus Selaginella, the sole representative of the order, the prothaUium appears to be already completely formed by the time the megaspore is mature, but occupies only the apical portion of the cavity of the spore ; the basal portion is siill filled by an undifferentiated mucilagi- nous protoplasm, which subsequently develops into a cellular tissue, the second- ai-y prothalluim^ or, as it is termed by some writers, the endosperjH. In some species, at least, this struc- ture is separated by a dia- phragm from the true pro- thallium. The prothallium always produces a number of archegones, sometimes as many as thirty, which arise in centrifugal succes- sion on the exposed portion of the prothallium, the one formed first being at the apex. The archegone ori- ginates by division of a superficial cell in a direction parallel to the surface ; the outer of these two then divides into four cells, and each of these again breaks up by tangential division into two. These form the 7ieckoi\\i^ archegone, which therefore consists of four rows, each composed of two cells. The lower of the two original cells becomes the venter of the archegone, and puts out a slender prolongation between the neck-cells, which is separated as the neck-cafial-ceil. Another very small portion is subsequently separated Fig. 20. — A — F, stages in the division of the microspore of Selaginella caulescens Spr. v, sterile cell ; G, antherozoid ( X 1400) ; H, vertical section of megaspore of S. Mar- tensii Spr. ;/, prothallium with three archegones ; end, en- dosperm ; e, exospore(x 165). (After Pfeffer.) 40 VASCULAR CRYPTOGAMS as the ventral canal-cell, and the protoplasm of the larger and lower portion rounds itself off into the oosphere. The two canal-cells then deliquesce into mucilage, leaving an open passage for the entrance of the antherozoids. The microspores, spherical orange or bright red bodies, remain in a dormant condition through the winter, and undergo further develop- ment in the spring. The contents then divide, first of all by a trans- verse wall of cellulose near one end into two cells of very unequal size. The smaller one of these does not divide further, and remains sterile ; it is regarded as the last degraded vestige of a male prothallium. The contents of the larger of the two cells, which may be regarded as an antherid, then break up into from four to eight primordial cells, and each of these divides again into four mother-cells of antherozoids ; but it is uncertain whether all the cells are fertile. The antherozoids are coiled up into a helix, and are furnished at the anterior end with two long fine cilia. The antherozoid is in all cases derived from the nucleus of the mother-cell ; a central vacuole, invested with a delicate membrane, often remains attached to its posterior end during ' sw^arming.' The ' swarming ' condition continues for about half to three-quarters of an hour. ^ M 6 Fig. 21. — Formation of embryo and suspensor in 5. Martensii, showing order of formation of dividing walls. (After Pfeffer.) In the formation of the embryo the first division of the oosperm differs from that in Rhizocarpese and in Fihces in taking place at right angles to the axis of the archegone. It is thus divided into two super- posed halves, from the lower of which is developed the embryo itself ; from the upper half a structure almost pecuhar to this order, consisting SELAGINELLACE^ 41 of a small number of large cells, known as the siispensor, or pro-embryo, from its apparent homology with the structure which goes by this name in Flowering Plants. By the elongation of the suspensor and the compression and absorption of the adjacent cells, the lower portion of the oosperm is forced into the endosperm, from which it appears to derive nutriment, dividing, both previously and subsequently, into a small-celled tissue. This tissue undergoes a large amount of differentia- tion before the embr}-o emerges from the megaspore, the rudiments of all the principal parts of the sporophyte making their appearance at this early stage. The mother-cell of the embryo divides into two by an oblique wall. From one of the two cells thus formed originate the stem and one of the coty/edons, from the other the foot and the other cotv- ledon. The rudimentary stem has a two-edged apical cell, from which segments are cut off alternately right and left. An inner mass of tissue soon becomes differentiated as the procambium of the axial ' vascular ' bundle, the peripheral tissue as dermatogen and periblem. The stem- bud, or plumule, with its first leaves (subsequent to the cotyledons), finally grows erect from the apex of the megaspore as the embr}'o increases in length. The formation of the first root begins later between the foot and the suspensor ; its apical cell is formed from an inner cell of the older segment ; the first layer of its root-cap originates from the splitting into two layers of the overlying dermatogen ; the later layers of the root-cap are formed from the apical cell of the root. The sporophyte differs greatly in appearance in the two orders. In Selaginella the stem is always slender, erect or procumbent, with distinct internodes, and lengthening rapidly by monopodial branching, which very often has a dichotomous appearance from the vigorous growth of the lateral branches. These lateral branches, with their ramifications, frequently develop in a single plane, giving the system the appearance of a compoundly pinnate leaf; all the branches and leaves displaying a distinctly dorsiventral character. The stem has an epiderm composed of elongated prosenchymatous cells, without stomates, but containing a considerable amount of chlorophyll in re- markably large grains. The fundamental tissue consists of elongated* thin-walled cells with oblique septa, fitting closely together without intercellular spaces, and endowed with the power of long-continu^ growth both in length and diameter. In the absence of small inter- cellular spaces the stem of Selaginella resembles that of mosses ; but, on the other hand, each 'vascular' bundle is surrounded by a large air-cavity, traversed by trabecules, rows of cells connecting the bundle with the surrounding fundamental tissue. The entire cortex has a tendency to become dark brown with age from partial'' sclerosis. AVhen 42 VASCULAR CRYPTOGAMS the cells of which these trabecules are composed are round, they form a loose spongy parenchyme surrounding the bundle, and sharply differ- entiated from the firm compact fundamental tissue. The stem has one or more cauline ' vascular ' bundles, which may be traced in the Fig. ^i.-Sela^inella {ncequalt/olia Spr. A, branch (natural size); B, microsporange ; C, megasporange (greatly magnified). procambial condition to the apex of the stem close beneath the apical cell and above the youngest leaves : the separate bundles which descend from the leaves (leaf-trace-bundles) only unite with the cauline ones at a later period. The bundles are usually ribbon-shaped, and are concen- SELA G I NELL A CE^ 43 trie and closed. In the centre is the xylem, consisting chiefly of scalari- form and reticulate tracheides ; this is completely surrounded by the Fig. 23.— Transverse section through leaf of 6". ina-qualifolia. ch, chlorophyll-bodies ; co, upper epiderm ; ett, lower epiderm ; sp, stomates ; /, air-cavity surrounding vascular bundle and traversed by trabecules. (After Goebel, magnified.) Fig. 24. — Transverse section of stem of ^. denticulata Lk. _ b, air-cavity surrounding ' vascular ' bundle. (After Goebel, magnified.) thin-walled phloem. The primary elements of the xylem, very narrow- spiral tracheides, are formed at the angles of the bundle, and from them 44 VASCULAR CRYPTOGAMS the development and lignification of the tracheides advance centripe- tally. The external layer of phloem is itself surrounded by two or three parenchymatous layers, constituting a bundle-sheath^ belonging to the fundamental tissue, but within the large air-cavity. The mode of apical growth varies in the different species. In some the apex of the stem is occupied, as in Isoetes, by a group of equivalent meris- matic cells ; while in others there are two co-ordinate apical cells side by side, or a single one, which may be two-sided or three-sided. The leaves are simple and unbranched, and are traversed by a single ' vas- cular' bundle. They are always of small size, re- sembling those of Lycopo- dium, awl-shaped and acu- minate, or ending in a delicate awn, and usually with a cordate base. The greater number of species are heterophyllous, the sterile leaves having two different forms ; those on the ventral or shaded side of the obliquely ascending stem are larger than those on the dorsal side exposed to the light. They are always in four rows, one dorsal and one ventral leaf forming a pair. On the upper side of the leaf near its base is the peculiar structure known as the ligule, from the presence of which the class has sometimes been called ' Ligulatae.' The fertile leaves are uniform in size, and differ somewhat in shape from the sterile, forming a compact square terminal spike. The sporange springs from the upper surface below the ligule. In some species the epiderm is alike on the two sides of the leaf ; in others it differs. The epidermal cells contain chlorophyll, as is the case in ferns, and frequently have beautifully serpentine lateral walls ; in some .species they are so greatly thickened that the cell-cavity disappears alto- FiG. 25. — S. inaqiialifolia; transverse section of stem ( X 150). (After Sachs.) SELAGINELLACE^ 45 gether. The chlorophyll, both in the epidermal cells and in the meso- phvll, is collected into large lumps, in which are grains of starch. Stomates occur in the under, rarely also in the upper surface. The mesophyll consists of a loose spongy parenchyme ; when the leaves are very small it is developed only as a single layer surrounding the central ' vascular ' bundle, and is altogether suppressed near the margins, where the upper and lower epiderm are in actual contact. True roots occur in all known species belonging to the order. In some species of Selaginella a structure known as the rhizophore inter- venes between the stem and the root. The rhizophores resemble roots in general appearance, but are destitute of a root-cap. They may spring either from the dorsal side of the stem only, near the base of a branch, bend round and then grow downwards, or two may spring from each fork, one on the dorsal, the other on the ventral side, the former of which usually remains undeveloped in the form of a small protuberance, while the latter grows to the normal size. Their origin is very near the grow- ing point, and they appear to be formed in the same way as the branches. Unlike the roots, they are exogenous structures. After apical growth has ceased, the end of the rhizophore, which is still very short, swells up into a spherical form : its cell-walls become thicker, and the first rudi- ments of the true root originate in the interior of the swelling, but do not break through the surface until the rhizophore has increased consi- derably in length by intercalary growth, and its swollen end has penetrated the soil, where its apical cells deliquesce into mucilage, through which the true roots reach the ground. In some species the rhizophores are frequently transformed into leafy shoots, which at first manifest some deviations from the normal structure of aerial shoots, but afterwards present the ordinary structure, and may even bear sporanges. The rhizophore is not, however, universal in Selaginella. In many species the roots spring directly from the lowest fork of the stem, and branch monopodially before they reach the ground. They originate, like those borne by the rhizophores, near the growing point. All the roots branch copiously, the planes of the successive branchings crossing one another at right angles. They have a single apical cell, but this soon ceases to give off segments, and the subsequent increase in length is chiefly due to intercalary growth. Both kinds of sporange are shortly stalked nearly spherical capsules (fig. 22), closely resembling those of Lycopodium in appearance and structure, except in their being heterosporous. They are collected into dense spikes at the extremity of somewhat metamorphosed leafy shoots. The lower portion of each spike in some species consists of megaspo- ranges, the upper portion of microsporanges, and the former may be 46 VASCULAR CRYPTOGAMS reduced to only one. Each fertile leaf or sporophyll subtends only a single sporange, which is borne on the stem above the leaf-axil. The sporanges are of considerable size in proportion to that of the leaf, and are formed from a group of superficial cells at the growing point of the stem. They make their first appearance as flat, afterwards spherical or club-shaped, swellings, completely covered by the epiderm, which A ^ ' il'W \ 1 subsequently forms, by tangential divisions, the wall of the sporange, composed of three layers. By subsequent growth the sporange Fig. 27.— Section of megasporange of ^. incpquali/olia, showing double wall of sporange, layer of tapetal cells, and mega- spores. (After Goebel, magnified.) comes to be placed in the axil or even on the base of the leaf. The ' vascular ' bundle of the leaf passes beneath the sporange without sending a branch into it. As in the other heterosporous families, the two kinds of sporange present no differentiation in their early stages. The archespore is the terminal hypodermal cell of an axial row. This divides into the sporogenous tissue surrounded by the layer of tapetal cells formed from the innermost of the layers of cells into which the wall of the sporange divides. In the megasporanges one of the spore-mother- cells grows more vigorously than the rest, which gradually abort. In this Fig. 26. — A^ fertile branch of 6". itK^qjiali- folia (half natural size). B, longitudinal section of upper part showing microspo- ranges and megasporanges. (After Goebel, magnified.) SELAGINELLACEyE 47 privileged cell are formed four spores, the number usually present in the mature megasporange. The microspores are formed in the same way as in the other heterosporous families. After falling out of the sporange they frequently adhere together in fours. The microspore has three coats — endospore^ exospore, and epispore — of which the inner- most is composed of cellulose. The coat of the megaspore is also treble, and the epispore is not unfrequently beautifully granulated and spiny. The dehiscence of both kinds of sporange is caused by the unequal contraction of the epidermal cells. The microsporanges are 2-valved, the megasporanges 3-4-valved. The genus Selaginella (Spring) includes above 300 species, spread over the whole globe, but most abundant in the tropics. Many species resemble Lycopodium very closely in habit, but are more moss-like, and the leaves generally more delicate ; in others the stem is erect, and they reach the magnitude of small shrubs. Several species are favourite objects of cultivation from the beautiful metallic lustre of the leaves. They are readily propagated non-sexually, a small fragment of the stem producing a new plant if kept warm and moist on loose earth, owing to the production of adventitious roots in the angle formed by the branch- ing of the ' vascular ' bundle of the leaf from that of the stem. No economical use is known of any species either of Selaginella or Isoetes. Order 2. — Isoete.e. In the single genus Isoetes the general phenomena of the life-history correspond to those of Selaginella, but with some important differences. Some weeks after the escape of the megaspore from the decaying mega- sporange its cavity becomes filled, by free-cell-formation, with a number of naked primordial cells, which gradually fill up the whole cavity of the endospore, and then become converted into a cellular tissue by the in- vestment of each with a cell-wall of its own. The endos])ore at the same time thickens, and separates into several layers with a finely granu- lar structure. The epispore, or outer layer of the coat of the megaspore, now splits at its apex by a three-rayed fissure, exposing the endospore, which also subsequently disappears, and a portion of the spherical pro- thallium is thus laid open. At its exposed apex appears the first arche- gone, which is followed by others if the first is not fertilised. The archegones resemble those of Selaginella, except that each of the rows which constitute the neck is composed of four instead of two cells. The microspores are yellowish grey, and of the form of the quadrant of a sphere. The antherozoids are very long, slender, and attenuated 48 VASCULAR CRYPTOGAMS at both ends, where they are provided with two tufts of very long ciha ; in some species they are remarkably large. Their period of ' swarming ' does not last more than about five minutes. The stem of Isoetes is distinguished by its extraordinarily restricted Fig. 28. — Isoetes lacustrh L. (natural size). growth in length, and the complete absence of branching, as well as by a remarkable secondary increase in thickness. It is completely covered by the bases of the leaves, leaving no part exposed. Its upper portion has the form of a shallow funnel, with the apex depressed in its centre. SELA GIN ELLA CE^ 49 The lonsf-continued increase in thickness which distin2;uishes this o;enus alone among Vascular Cryptogams — except possibly Botr^xhium (Filices) — is dependent on an internal layer of meristem which surrounds the axial 'vascular' cylinder, and continually produces new layers of paren- Fig. 29. — A, mega'^pore of Isoctes aciistris L. B, prothallium ; a, archegone (x about 50). (After Hofmeister.) chyme on the outside. This takes place especially in either two or three directions, so that a corresponding number of projecting masses of tissue are formed, which slowly die oif on the outside ; and between them lie the same number of furrows meeting on the ventral side of the stem, which has hence the appearance of a laterally elongated plate or ^ A Fig. 30. — /. lacicstris. A — D, microspore, showing stages in formation of antherid and antherozoids (X580). 7', sterile cell ; a — d, stages in formation of antherozoid (x 580) ; e,/, mature antherozoid (X700). (After Millardet.) disc. In these furrows are produced a large number of rows of roots in acropetal succession. In the stem is a single cauline axial bundle com- posed of short reticulate and spiral tracheides, surrounded by a rudi- mentary phloem without sieve-tubes. From this axial bundle there E so VASCULAR CRYPTOGAMS proceeds a branch into each leaf and one into the root. The layer of meristem which surrounds the axial bundle increases chiefly in the centrifugal direction, fresh layers thus formed replacing the outer ones, which continually die off. The secondary long-enduring increase in thickness of the stem is chiefly due to increase in thickness of the cortical tissue, though new xylem-elements are also produced. The mode of apical growth differs from that in most species of Selaginella. There is no single apical cell, the apex of the stem being occupied by a group of equivalent merismatic cells. Fig. 31. — Longitudinal section of stem of /. /«r7«2'r/5. h—P, leaves; r' — r"*, roots: the ligules are shaded (x 30). (After Hofmeister.) Fig. 32. — Longitudinal section through lower portion of leaf of /. /rtcwj^r/j (diagram- matic) L, ligule ; 7, indu- sium ; Sp, microsporange ; Tr, trabecules ; Gf, vascu- lar bundle of sporophyll. (After Goebel.) The leaves of Isoetes are very elongated, cylindrical, and quill-shaped, and are arranged in a complicated phyllotaxis on the very short stem. They are segmented into a basal portion, the sheath or giossopode, and an apical portion, the lamina. The sheath is nearly triangular in form with a very broad insertion, and does not completely embrace the stem. It is convex behind and concave in front, where it bears the sporange in a large depression known as tht fovea ; the margin of this depression rises in the form of a thin membranous outgrowth, the veil or indusium, which, in many species, extends above and beyond the sporange. Above SELA GIXEL LA CE.E 51 the fovea, and separated from it by a ridge called the saddle, is a smaller depression, thefoveola, the lower margin of which forms a lip-like struc- ture, the labium, and from its base rises a narrow membranous acuminate structure, the ligule, with a cordate base, and usually projecting above the foveola. The sheath passes above into the lamina, which is narrow and thick, almost cylindrical, but flattened in front, contains chlorophyll, and is traversed by four wide longitudinal air-cavities, segmented by transverse septa. A rosette of these fertile leaves or sporophyUs is pro- duced annually, but between these whorls are alternate whorls of phyl- lades, or imperfec; leaves, consisting, in the submerged species, of only a small lamina with no sheath, while in the terrestrial species they are reduced to mere scales. Stomates occur in the paludose and terrestrial, but not in the submerged species. Scattered spiral tracheides are found in the parenchymatous base of the leaf. The fundamental tissue, which Fig. 33. — Development of microsporange of /. laciestris. t, tapetal cells ; Tr, trabecules : the archespore and sporogenous cells derived from it are shaded. (After Goebel, magnified.) is not separated from the single ' vascular ' bundle by a bundle-sheath, has a strong tendency to become sclerenchymatous, especially beneath the epiderm and in the sheath. The very simple bundle which occurs in each leaf is stated by Russow to be collateral, the xylem and phloem lying side by side. The roots spring from the furrows of the stem, and resemble, in structure and mode of branching, those of Selaginella. There is no rhizophore. The sporanges of Isoetes do not make their appearance until the third year after germination. Each sporophyll bears only a single sporange, which is undoubtedly a product of the leaf, and is situated below the ligule in the fovea, to which it is attached by a narrow base. The outer leaves of the fertile rosette produce megasporanges only, the inner leaves microsporanges only. Both kinds of sporange originate from a group of cells at the base of the leaf The archespore is derived E 2 52 VASCULAR CRYPTOGAMS from a hypodermal layer of cells. In the formation of the microsporange the archespore-cells elongate in a direction at right angles to the surface, and divide by transverse walls. Some of these rows of cells are then arrested in their growth, lose their abundant protoplasm, and divide into elongated tabular cells constituting the trabecules, which cross the sporange from the dorsal to the ventral side. The remaining cells develop into the mother-cells of the microspores, an external layer having been previously separated as tapetal cells. In the development of the megasporange the processes are the same as far as regards the formation of the tapetal cells and the trabecules ; the mature sporange may contain either four or a much larger number of megaspores. The mode of development of the megaspores presents perhaps the closest analogy to that of the secondary embryo-sacs of Gymnosperms that occurs in any; order of Avascular Cr}'ptogams ; and the same remark applies to the formation of the microsporanges and pollen-sacs. Both kinds of sporange are indehiscent, the spores escaping only by the decay of the tissue. In both kinds of spore the epispore is frequently granulated, tuber- culate, or echinate ; and in some species there are two kinds of microspore differing from one another in this respect. One or two species of Isoetes display the phenomenon of apogamy in various degrees. In extreme cases the formation of the megasporange is arrested at a very early stage, and its place supplied by a vegetative shoot, which becomes detached and develops into an independent plant. The number of species of Isoetes is about fifty, the greater part inhabitants of the warmer portions of the globe. They somewhat resemble Pilularia in general habit. Some species are aquatic and entirely or partially submerged, other paludose, and a ver}' few terrestrial ; and they present corresponding differences in the structure of their tissue, presence of stomates, &c. Literature. Yon Mohl — (Stem of Isoetes) Linnaea, 1840, p. 181. Braun — Ueher Isoetes, Monber. Berlin Akad. Wiss. , 1S63. Hofmeister— Entwick. d. Isoetes lacustris, Abhandl. Sachs. Gesell. Wiss., 1865. Pfeffer — Entwick. d. Keims Selaginella, in Hanstein's Bot. Abhandl., iv. , 1 87 1. Tchistchakoff— (Isoetes) Xuov. Giorn. Bot. Ital., 1873, p. 207. Bruchmann — Wurzeln v. Lycopodium u. Isoetes, 1874. Hegelmaier — Bot. Zeit., 1874, p. 481. Goebel — (Apogamy of Isoetes) Bot. Zeit., 1879, p. i. Mer— (Sporange of Isoetes) Compt. Rend., xlii., 1881, p. 310; and Bull. Soc. Bot. France, 1 881, pp. 72, 109. Kienitz-Gerlofif— (Embryo of Isoetes) Bot. Zeit., 1881, pp. 761, 785. Vines— (Isoetes) Annals of Botany, vol. ii., 1888, p. 117. L YCOPODIA CE.-E 5 3 ISOSPOROUS VASCULAR CRYPTOGAMS. Class III.— Lycopodiaceae. The Lycopodiaceae are a comparatively small group of plants com- prised in only four genera, differing from one another greatly in habit, but agreeing in the prevalence of a dichotomous rather than of a mono- podial mode of branching in both stem and root, though this is by no means universal. Growth is effected by a group of equivalent cells in the growing point, never (except in Psilotum, Sw.) by a single apical cell. The leaves are always of small size and entirely undivided ; in Psilotum they are reduced to mere scales, and this genus is also entirely rootless ; while in Phylloglossum (Kze.) the underground stem is tuberous. The sporanges and spores are of one kind only ; the spore produces on germination (where this has been obser\-ed) a green or colourless pro- thallium, which carries on a much more independent existence than is the case in the heterosporous orders, and bears, in the cases which have been examined, both archegones and antherids. The position of the sporanges varies. In the Lycopodiese it corresponds to that of the Selaginellese, on the upper side of the base of the leaf, or they are crowded on special erect branches ; and here the sporanges are unilocu- lar ; while in the Psiloteae they are plurilocular, and are grouped on the main stem or on short lateral branches. Further details are best described under the heads of the two orders into which the Lycopodiacese may be divided. In the moncecious prothallium the Lycopodiaceas approach the Ophioglossaceae ; while in the structure of the sporophyte they display a remarkable resemblance to the heterosporous Selaginellaceae. Order i. — Lycopodie.e. In this order are included two genera of ver}' different habit : Lyco- podium (L.), with nearly 100 known species ; and Phylloglossum (Kze.), with only one. The form and appearance of the oophyte vary greatly even in the different species of the typical genus Lycopodium. The ger- mination of the spores of L. inundatum (L.) has been described as follows by de Bary : — The endospore bursts in the form of a nearly spnerical vesicle through the exospore, which splits into three valves ; the ger- minating filament which originates in this way then divides by a septum into a basal cell, which undergoes no further change, and a larger apical cell, which divides into two rows of segments ; each segment further divides by a tangential wall into an inner and an outer cell, so that 54 VASCULAR CRYPTOGAMS the young prothallium now consists of an axial row of four short ceUs, the basal and apical cells, and two lateral rows. The cells contain a few grains of chlorophyll. The formation of the sexual organs was not observed. The mature oophyte of L. annotinum (L.) presents several important differences. The prothallium is underground and of a yellowish-white colour, destitute of chlorophyll, and consists of a tuberous mass with cushion-like ridges on the upper side and a few small rhizoids. On its upper side and completely imbedded in the tissue are a number of antherids, consisting of cavities covered by one or more layers of cells, and containing a large number of mother-cells of antherozoids. The antherozoids themselves appear to be minute bodies consisting of only a few coils, and probably with two cilia. The archegones have not been actually observed, but are evidently borne on the same prothallium A B i^^*^^:^^^b3$^ minating in an antherid, or even to a single cell. Campbell has detected continuity of protoplasm in the cells of the prothaUium of Struthiopteris ger- manica (L.). In the Osmundacese the prothallium springs directly from the spore without any intermediate proto- neme, a plate of cells being formed on Fig. 43.— Under side of prothallium of germination by longitudinal and trans- Aneimia Phyllitidis Sw. sk, cushion, ^... , ^ ,. ■i- with archegones ;«, antherids aAdrhlzoids VCrSC dlVlSlOnS ; the firSt rhlZOld IS (X25). (After Bauke.) fomicd out of a postcrior ccll. The rib- bon-shaped prothallium of Osmunda (L.) is characterised by the presence of a midrib composed of several layers of cells running along its whole length. The arche- gones are produced on the under surface on this midrib ; the antherids either on the margin or on the under surface with the exception of the midrib. An approach towards a higher type of organisation is indicated by the tendency of the pro- thallium to become dioecious in the Osmundaceae, and in Struthiopteris (L.). All the spores from the same sporange sometimes produce male prothallia, i.e. such as bear antherids only, the jTjQ ..^ — Antherid of Adiantnm capilbis-Veneris L., in different stages. /, prothallium; a, antherid ; 5, antherozoids ; b, vesicle with starch-grains ( x 500). FILICES 67 archegones being produced later, and in smaller numbers, on female pro- thallia ; or the same prothallium may produce first antherids and sub- sequently archegones, when it may be termed proterandrous. This is remarkably the case also in Gymnogramme. In Cystopteris fragilis (Bernh.) (Polypodiace^e) Campbell states that there are two kinds of prothallium, a smaller male and a larger hermaphrodite. The prothal- lium of ferns is sometimes propagated vegetatively by the production of adventitious shoots from single marginal cells, which become detached and form independent prothallia. This takes place especially in Hymenophyllacece and in Osmunda, but occurs also in Polypodiaceae, Fig. 45. — Archegone o? Adiantum capillus-Veneris, in various stages. A,B, C, E, in longitudinal, D, in transverse section ; A, neck ; si, canal-cells converted into mucilage ; s, ventral canal-cell ; e, oosphere ; in E divided into a 2-celled embrj-o (x 800). (After Goebel.) abundantly in Gymnogramme (see Cramer, Denkschr. Schweiz. Naturf. Gesell., 1880). The prothallium of Yittaria (Sm.) produces peculiar stalked bulbils. The antherids of ferns are small papilliform projections on the under side or margin of the prothallium (very rarely on the upper side), produced among the rhizoids, and of similar origin, i.e. from a single superficial cell ; in the Hymenophyllaceae they are produced also on the protonemal filaments. The protuberance becomes separated by a septum from the parent superficial cell, and then sometimes divides at once into the parent-cells of the antherozoids. But more often the F 2 68 VASCULAR CRYPTOGAMS papilla divides first of all into a central cell surrounded by a single layer of peripheral cells. These last are barren, but contain chlorophyll ; while the central cell divides still further, each derivative nearly cubical cell then producing a flat spirally-coiled antherozoid contained within a vesicle, or ' special parent-cell.' In no case is the number of anthero- zoids produced by a single antherid very considerable. The function of the peripheral cells appears to be to absorb water violently when the antherid is mature, in consequence of which they swell up considerably and rupture the central cells, thus causing the escape of the parent-cells of the antherozoids. From each of these is then discharged, by the bursting of its delicate cell-wall, an antherozoid consisting of a flat band of proto- plasm coiled spirally three or four times, and bearing at its anterior end a number of fine cilia (fig. 44). To its posterior end. is frequently attached for a time a vesicle containing starch- grains, which is pro- bably the remains of the special parent- cell of the anthero- zoid. i\s in other Vascular Crypto- gams, the body of the antherozoid ap- pears to be formed from the nucleus of the mother-cell, the cilia from the cell-protoplasm. The archegones are produced on the under side of the cushion of the prothallium, but in much smaller numbers than the antherids. Like them, each archegone is derived from a single superficial cell, which at first bulges only slightly, and is first divided into three cells by two tangential walls. The lowermost of these three, or basal cell, divides further, and takes its share in the formation of the venter, or swollen part of the archegone, which is altogether imbedded in the prothallium. The outermost of the three cells develops into the neck-wall, or outer- most wall of the neck of the archegone, dividing at first into four cells, from which the four rows of cells which constitute the neck are formed by oblique septa. Since the neck grows more rapidly on the anterior side, i.e. the side nearest to the apex of the prothallium, and hence becomes convex on that side, the number of cells is also larger in the Fig. 46. — Archegone oi Pteris serrtdata L. at the moment of the expulsion of the mucilage (x 350). (After Strasburger.) FILICES 69 anterior rows of the neck, the usual number being six, while there are seldom more than four in the concave posterior side. From the middle one of the three primary cells arises the whole of the axial row of cells of the archegone, consisting of the ce?itral cell and the canal-cells. During the development of the neck this middle cell becomes pointed upwards, and forces itself between the neck-cells ; this pointed portion becomes divided off by a septum, and now forms the single ?ieck-canal- cell^ which lengthens as the neck lengthens. The large central cell now breaks up into an upper and smaller ventral canal-cell and a much larger lower cell, the protoplasmic contents of which subsequently become rounded off, and constitute the oosphere. According to Campbell, the ventral canal-cell is wanting in Struthiopteris germanica (L.). The walls of the canal-cells swell up and become converted into mucilage, and finally this thin mucilage, together with the protoplasm of the canal-cells, is expelled from the open neck. The antherozoids are retained by the mucilage, and collect in large numbers before the archegone ; a number of them force themselves into the canal of the neck, and of these some eventually reach the oosphere, and coalesce with it, entering it at a light-coloured spot near the neck, which is termed the receptive spot. After impregnation the neck closes up. It is very rare for more than one archegone to be fertilised on the same prothalhum, and the enormous majority of prothallia perish without producing any sporophyte generation. The ordinary course of the alternation of generations is occasionally interrupted by apogamy or by apospory, the suppression respectively of the oophyte or of the sporophyte generation. The former has been observed especially in Pteris serrulata (L. fil.), the laiter in particular varieties of Athyrium filix-foemina (Bernh.), and of Polystichum angulare(Willd.). In apogamy the non-sexual fern-plant springs directly from the prothallium without the intervention of a fertilised archegone. In apospory a pro- thallium is produced on the surface of the frond, either in the locality where the sorus would normally be found, or less often elsewhere, and may assume unusual forms, sometimes that of a solid cylindrical body, but bears normal archegones and antherids. Bower classifies the various forms of substitutionary or correlative growths connected with the suppression of the sporophyte generation under three heads, viz. — (i) simple prolification ; (2) sporophytic budding; (3) apospory. The first hardly occurs among ferns. The second is illustrated by the familiar formation of bulbils in species of Asplenium (L.). Cystopteris (Bernh.), &:c., in which the formation of the buds cannot be directly corre- lated with arrest of spore-formation. In apospory we get a more or less complete sporal arrest, but this may vary in degree. In some instances 70 VASCULAR CRYPTOGAMS the substitutionary growths which accompany the arrest of spore-forma- tion are restricted to the sporanges themselves. These are replaced by ' pseudo-bulbils ' of a pear-like form, presenting but little resemblance to ordinary prothallia, but demonstrating their oophytic character by pro- ducing antherids. In other examples the prothalloid growths are by no means restricted to the sporange ; they may either arise from the sorus itself, or may appear at points quite distinct from the sori, and even on fronds which bear no sori at all. There is here a distinct transition from 55^ Fig. 47. — Apogamous shoot of Pteris seyndata, on the under side ot the prothallium/ ; b, first leaf; z\ apex of stem ; iu, rudiment of first endogenous root ( x 80). (After de Barj-.) Fig. 48.— Prothalloid growth oi Poly- sticJnim annulare Willd. var. /?//- chcrri7)ta, originating from surface of frond ; arch, archegone ( x 10). (After Bower.) sporophyte to oophyte without the intervention of spores. Compara- tively little is known about the oophyte generation in the Hymeno- phyllacese, but it would appear as if apogamy were a very common, perhaps even normal occurrence in some species of Trichomanes (Sm.); and here the two phenomena have even been obsers-ed on the same indi- vidual, the oophyte and sporophyte generation succeeding one another without the production of either spores or sexual organs. The fertilised oosphere or oosperm becomes immediately invested FILICES 71 with a cell-wall of its own, and develops by cell-division into the ejuhyo, from which springs the young sporophyte, commonly known as the fern-plant. The first division-wall in the oosperm is always nearly vertical ; and two others follow, at right angles to it and to each other, dividing the oosperm into octants. From the anterior of the two original halves are derived the growing point of the sfe??i, and the cotyledon or first leaf; from the posterior half ihQfoothy which it is attached to the prothal- lium, and the first root. Until the differentiation of the first leaf and the fixed root, the embryo remains imbedded in the surrounding tissue of the prothallium, which grows with its growth. The primary root is always small ; in the Hymenophyllacese it disappears early, and in many Fig. 49. — Asplenium dcciissattnn ; adventitious bud, k, already rooting (natural size). Fig. 50. — Young sporophyte of Adiantiijn capilhis-Veneris still attached to prothallium / ; b, first leaf ; w', w", ist and 2nd root ; h, rhizoids of prothallium ( X 30). (After Goebel.) species of Trichomanes no subsequent roots are formed, their place being supplied by underground branches. The mature fern varies in size from that of the 'filmy ferns,' species of Hymenophyllum not above an inch in height, with delicate moss- like habit, to the stately ' tree-ferns ' of the Southern Hemisphere (Cyatheaceje and Dicksonia, L'Herit.), fifty or sixty feet in height. The stem is either ascending and vertical, or creeping on or beneath the surface of the soil, or occasionally scandent (Lygodium, Sw.), often very short with undeveloped internodes, and the leaves so crowded that fre- quently no portion of the stem — then often called a cmidex — remains exposed ; while in the creeping and climbing species the leaves are often 72 VASCULAR CRYPTOGAMS separated by long internodes. The ultimate roots are always adventi- tious ; that is, there is no predominant axial root which is a prolongation downwards of the main axis of the plant, as in many Dicotyledons and some Monocotyledons. They are usually very numerous, especially in tree-ferns, arising in acropetal succession, and completely clothing the lower part of the stem, or, where this is supj^ressed, the leaf-stalks, as in the case of the common ' male fern ' (Aspidium filix-mas, Sw.). The ultimate branches of the root are furnished with a root-cap as in Flower- ing Plants. The leaves, or, as they are more commonly called, ' fronds,' are invariably stalked, and are remarkable in many species, especially when they attain a large size, for the great extent to which subdivision of the lamina is carried ; in some tree-ferns they attain a length of from six to ten feet. In the filmy ferns they consist, as in Muscinese, of only a single layer of cells penetrated by distinct ' vascular' bundles. Stomates, similar in structure to those of Flowering Plants, occur abundantly both on the under side of the leaf and on the leaf-stalk, except in the Hymenophyllaceae. The leaves exhibit very little metamorphosis com- pared to those of Flowering Plants. Most usually all the leaves are alike in form and extent of division, and even nearly so in size ; but in some species only certain of the leaves, sporophylls, are fertile, and these then show a more or less well-marked difference from the barren leaves, as in our 'hard fern ' (Lomaria spicant, Desv.)and 'parsley fern '(Cr^-ptogramme crispa, R. Br.). In the ' elk's-horn fern ' (Platycerium alcicorne, Desv.), commonly grown in cultivation, the leaves are alternately broad thallus- like barren plates, closely applied to the surface on which the plant grows, and long erect dichotomously branched fertile leaves. The leaves (except the first, which spring from the prothallium) are circinate in vernation, both the principal rachis and the midrib of the pinnae (when the leaf is pinnate) being rolled up on their upper side — owing to the more rapid growth of the cells on the under than those on the upper surface — and only slowly unroll as the development of the leaf advances. The young leaves, and the rachis and petiole of mature leaves, are generally more or less completely clothed with pales or ramenta, flat brown scale-like trichomes or outgrowths of the epiderm. These are often glandular, and sometimes contain crystals of oxalate of lime. They serve as a protective mantle to the young stem and leaves, and also as a reservoir of moisture. Capitate, glandular, and other more ordinary kinds of hair are also of frequent occurrence. In the typical ferns the sporanges are also trichomic in their origin. They are collected into groups or sori (fig. 58), usually formed in connection with a 'vascular' bundle. In unilamellar leaves these sori are placed on the edge, in all others almost invariably on the under side of the leaf, especially of its FILICES 73 apical portion, and they then assume a great variety of shapes — circular, reniform, crescent-shaped, linear, or they are concealed beneath the revolute margin of the leaf The sorus may or may not be covered by a membrane called the indicshini, an outgrowth of the epiderm. In the Fig. 51. — Aspleninm AdianUim-nigrtnn L. ; rhizome with fronds sho\ving circinate vernation (natural size), a, under side of fertile pinnule (magnified). Cyatheaceae they assume the form of a cup ; in the Hymenophyllace^e they are situated at the extremity of a vein at the apex or margin of a pinna. In some instances, as in our native ' flowering " or ' royal fern ' (Osmunda regahs, L.), the sori completely consume, in the course of their 74 VASCULAR CRYPTOGAMS development, the parenchyme of the fertile (apical) part of the leaf, giving the appearance of a panicled or thyrsoid inflorescence. The s_f>orange is usually stalked, and has an elliptical form, or that of a battle- dore or racket-bat. The sides are commonly thin and membranous, and the sporange dehisces either longitudinally or transversely, generally from the elasticity of an anniihis or ring of brown thick-walled cells running along or across it. The position of this annulus, and its more or less complete development or entire absence, are useful characters in the subdivision of the class. In the Marattiacese the sporanges are of altogether different origin, being developed from hypodermal masses of cells ; and transitional forms occur between the two. The spores are minute, very commonly re- niform, or often nearly cubical, resembling pollen- grains in structure, usually furnished with two coats, an exospore and endospore, the latter of which is some- times double, and the former generally marked with papillae, reticulations, &:c. A more minute descrip- tion must now be given of the structure and peculi- arities of the various organs. The great distinguishing feature which characterises the development of the Fig. 52. -Diagram of tip of leaf of Ceratopteris thalic- StCUl of fcmS, aS COntraStCd (Af(l?Kn°T"' '^' "'^'''''^ "^' ' ^' ^''^^'^' ^°^^ °^ ^^^^' ^^'^^^ ^^^^ which occurs in all Flowering Plants (Gym- nosperms and Angiosperms), is the presence of a single apical cell^ from which the whole of the growing point or apical meristem origi- nates, and which may therefore be recognised as the parent-cell of the whole of the tissue subsequently formed. This apical cell is usually wedge-shaped in creeping stems with a bilateral structure, a three-sided pyramid in erect or ascending stems. The growing apex of the stem is frequently completely hidden in the youngest leaf-bud, but in other species there is a considerable intervening space. In some Hymenophyllaceae leafless prolongations of the stem assume the appearance and the function of roots. As contrasted with Flowering Plants, especially Exogens, the stem of ferns is characterised by the small extent to which it branches ; FILICES 75 and this is true not only of the erect columnar stem of tree-ferns, but also of the creeping or erect stem of smaller species. Axillary branch- ing is very rare, if it ever actually occurs ; the terminal branching is always dichotomous, never sympodial. The fundamental tissue of the stem and leaf-stalk consists, in many species, entirely of thin-walled parenchyme. In others, and especially in tree-ferns, portions of it undergo a change in the great thickening and brown colouring of the cell-walls, the cells becoming at the same time prosenchymatous. In this sderenchyine of the fundamental tis- sue the sclerosis may take place in Fig. 53. — Transverse section of 'vascular' bundle of Polypoducm leiorhizum Wall, p, fundamental tissue ; s, sclerenchj-matous sheath ; b, phloem ; hy xji-lem ( x 200). (After Luerssen.) pr Fig. 54. — Transverse section of stem of Pteris aquilina L. r, epiderm ; /, fun- damental tissue ; pr, sclerenchymatous sheath ; ig, vascular bundle; ag, outer network (somewhat magnified). individual isolated cells ; more often the cells so affected are united into con- spicuous bands or sheaths. In many Polypodiaceae and Osmundaceae the entire cortex assumes eventuallv a dark colour. In the common brake (Pteris aquilina, L.) two thick sclerenchymatous bands of this description lie between the inner and outer ' vascular ' bundles, while another continuous layer immediately underlies the epiderm. The firmness and sohdity of the stem of tree-ferns are mainly due to strongly developed sclerenchymatous cylinders which form complete sheaths surrounding the ' vascular ' bundles. The ' vascular ' bundles themselves are always closed or destitute of cambium ; in the stem, except in Osnmnda, and usually in the leaves, they are concentric^ consist- ing of a central xylem-portion entirely enveloped in a layer of phloem ; in the stem and leaves of Osmunda, and in the leaves of some other ferns, they are collateral^ the xylem and phloem portions lying side by 76 VASCULAR CRYPTOGAMS side. Besides a few narrow spiral tracheides, lying at definite points of the transverse section, the xylem consists mainly of scalarifor?)! tracheides, i.e. of tracheides with bordered pits which usually have the appearance of transverse clefts, their ends being mostly obliquely trun- cate or fusiform and pointed. True vessels occur but rarely in ferns ; e.g. in Pteris aquilina and in the rhizome of x\thyrium filix-foemina, where they are also scalariform. Between the tracheides lie narrow thin-walled cells which contain starch in winter. In the phloem, in addition to narrow parenchymatous cells, are sieve-tubes with well- developed sieve-plates, but forming true callus only in a small number of cases ; and at the circumference narrow bast-like thick-wall prosen- chyme. Each individual bundle is usually immediately enclosed in a single distinct layer of narrower cells, the vascular biindle-sheath or endoderm ; this layer, which probably originates from the fundamental tissue, displays a strong tendency for its walls to become brown and suberised. In very young stems and those which permanently remain very slender, as in many Hymenophyllaceae, there is a single axial bundle. But in stouter stems and leaf-stalks the central bundle is re- placed by a network of anastomosing bundles, presenting, in typical cases, a cylinder of considerable diameter, by which the fundamental tissue is separated into an outer cortical dcnd an inner medullary Y>orX.ion ; but isolated scattered bundles also arise in addition. The principal bundles which constitute this cylindrical network mostly have the form of broad plates with the margins curved outwards, each surrounded by its thick firm brown sclerenchyme-sheath ; they usually present the appearance of an interrupted ring near the periphery, but in Osmun- dacese the ring is more continuous. From the margins of these cauline bundles spring the more slender filiform bundles which pass into the leaves, the number of openings in the meshes of the cauline 'vascular' cylinder corresponding to that of the leaves. In the leaf-stalk the bundles may either run separately or may coalesce into plates. Ter- letzki (Pringsheim's Jahrb., 1884, P- 45 2) has detected continuity of protoplasm between the cells in the parenchyme of the rhizome in several species of fern ; the intercellular spaces also contain protoplasm which is in connection with that of the cells. In the aquatic genus Ceratopteris the stem contains large air-cavities. Elongated tannin-sacs occur in the parenchyme of the stem and leaf-stalk of many ferns, especially in the neighbourhood of the ' vascular ' bundles. Gum- and mucilage-cells are also of frequent occurrence. Incrustations of cal- cium carbonate are not infrequent on the leaves. Round stalked glands occur in the fundamental tissue of the stem and leaves of Aspidium filix-mas. FILICES 77 The leaves of ferns stand either in two rows on the stem, or less often in a single dorsal row, or the phyllotaxis is more complicated and spiral ; they are never opposite or whorled. Each leaf originates from a superficial cell of the growing point distinguished by a stronger swell- ing of its outer cell-wall. The petiole is the first part of the leaf formed ; the lamina then begins to appear at its apex, and itself develops from the base to the apex. In many ferns the leaves of the mature plant are characterised by the extraordinary slowness of their development. In old plants of Pteris aquihna the formation of the leaf commences fullv two vears before it bea;ins to unfold : at the com- mencement of the second year only the leaf-stalk is as yet in existence ; during the summer of the second year the lamina begins to develop at the apex of the rod-like petiole, and may be found hidden beneath the long hairs in the form of a minute disc. It then begins to bend down- wards at its apex, and continues for a time in a pendent condition. It is only in the spring of the third year that the elongation of the leaf- stalk forces the lamina above the surface of the soil, and that the latter begins to unfold. In Aspidium filix-mas the development is almost as slow. The basifugal development of the lamina itseK is also extremely slow in many ferns, the lower portions having long been fully formed while the apex is still unfolding. In several genera, as Gleichenia (Sm.) and Mertensia (Willd.), a periodical interruption occurs of the apical growth, this intermittent development even extending over several years. In Lygodium the primary pinnas remain unfolded after the formation of a pair of pinnae of the second order, while the rachis of the leaf grows without limit and resembles a twming stem, climbing in some cases to the height of fifty or one hundred feet, the pinn^ themselves presenting the appearance of leaves. In the anomalous Ceratopteris thalictroides, which grows in water, the ultimate segments of the leaves are swollen up in a pod-like manner. Goebel has shown (Ann. Jard. Bot. Buiten- zorg, vii., 1887) that in the heterophyllous ferns, such as Platycerium alcicorne and several species of Polypodium (L.), one form of leaf is specially adapted, directly or indirectly, for the supply of nutriment to the plant, and is sometimes furnished with special aquiferous tissue. The stipular structures of the Marattiacese are quite peculiar among Vascular Cryptogams. The leaves of ferns not unfrequently display a tendency to branch dichotomously at the apex, but in other cases the branching appears to be monopodial. The leaf-stalk has frequently the power of producing adventitious leaf-buds (see fig. 49). In Struthiopteris germanica these develop into long underground stolons covered with scale-leaves, which at length rise above the surface, and besr at their apex a rosette of ordinary leaves. Nephrolepis (Sch.) is also furnished 78 VASCULAR CRYPTOGAMS with remarkable stolons, the extremities of which swell up into tubers ; but it is uncertain whether they belong to the stem or the root. In other cases adventitious leaf-buds are borne on the upper surface of the lamina or in the axils of the leaves. In Woodwardia radicans (Sm.) and some other species, the long drooping leaves may root in the soil and put up new shoots. The veins in the leaves of the great majority of ferns do not anastomose, but divide repeatedly dichotomously. Their ' vascular ' bundles differ, in some cases, from those of the stem in being collateral, the xylem facing the upper, the phloem the under surface of the leaf. With the exception of some species of Trichomanes, all ferns have true roots, characterised, like those of Vascular Cryptogams generally, and of Flowering Plants, by the presence of a true root-cap, composed of several layers of cells, and by the tendency of the epidermal cells to develop into long unsegrnented filaments or root-hairs, by which the nutriment is absorbed from the soil. These proceed in acropetal suc- cession from the creeping underground stem or rhizome, or, where the stem is erect, ver}- short, and densely covered with leaves, from the leaf- stalks. In tree-ferns the lower part of the erect stem is densely covered with a thick felt-like envelope of slender roots, which give a broad base to the stem. Like the stem, the tissue of the root develops from a single apical cell. The branching is always monopodial. The lateral rootlets arise in acropetal succession on the outside of the primary ' vascular ' bundle. The root is traversed by a single axial cylinder formed by the coalescence of ' vascular ' bundles. The epiderm of the leaves of those ferns which are not unilamellar differs in no essential respect from that of Flowering Plants, but its cells contain a larger quantity of chlorophyll. The epiderm of the under side only is abundantly provided with stomates, which are usually of quite the ordinary structure. In some cases, as Aneimia (Sw.), they present the peculiar appearance of the two guard-cells being entirely enclosed within a single epidermal cell. Those of Kaulfussia (Bl.) (^Nlarattiacese) are ver}^ large, and of peculiar structure. The sporanges of ferns are rounded, ovoid, or pear-shaped capsules, seated on long stalks in the Polypodiaceae and Cyatheaceae, sessile in the other orders. When mature, the wall of the capsule consists, except in the Marattiace^e, of a single layer of cells, a particular row of which, running longitudinally, transversely, or obliquely round the capsule, usually undergoes special development, and is known as the annulus ; but the annulus may be entirely wanting, as in the ]\Iarat- tiaceae, or its place may be taken by the special development of an apical or lateral group of cells, as in the Osmundace^. Where there is FILICES 79 an annulus the sporange dehisces by a fissure at right angles to it ; in the r^klarattiaceae it opens by an apical pore. The dehiscence is due to unequal contraction in drying of the unequally thickened portions of the cell-walls of the annulus. On one side of the sporange of a considerable number of ferns are two, three, or four cells of peculiar form, with lignified cell -walls, the lip-cells^ between which the dehis- cence always begins, and which ap- pear to guide its direction. These cells together are sometimes called the ' stomium.' Among the spo- on Fig. 55. — Sporange o{ Aspiduan filix- jnas, showing annulus an, lip-cells Ic, and paraphyse attached to stalk. (After Kiindig, greatly magnified.) ranges are frequently slender seg- mented filaments, or paraphyses. T -n 1 J ■ i.u ■ Fig. 56. — Development of sporange of Asfile- In some Polypodiacese there is a ,„v/;a^ Trichoma^ies l.. ^, archesporef r, single (rarely more than one) out- annulus (x 550). (After Goebei.) growth from the stalk of the sporange, resembling a capitate hair, and sometimes septated internally. It is regarded as a paraphyse, and may probably be an undeveloped sporange. The entire sorus may be covered by the recurved margin of the leaf, or by a true i}idusmm belonging to the epiderm, or by a false indusium, consisting of an outgrowth of the hypodermal tissue, composed of several layers of cells. In Enterosora (Bak.), from. British Guiana (Polypodiacege), the sporanges spring from the base of spherical chambers in the under surface of the 8o VASCULAR CRYPTOGAMS leaf, which open only by a narrow slit. Although the sori usually originate on the veins of a leaf, and only on the under side of the lamina, this is not always the case. In Olfersia they spring from both surfaces of the lamina by the side of the midrib ; and in this and other species of Acrostiche^ from the mesophyll as well as the veins. In the HymenophyllaceK they are enclosed in a cup-like indusium, and are attached to the apex of the veins, which projects beyond the margin of the leaf The spot on the fertile vein which bears a sorus is known as the placenta or receptacle. In the Polypodiace^, and probably also in the Cyatheace^, each sporange originates from a single epidermal cell, which swells up considerably, and is cut off from the rest of the leaf by a septum. This mother-cell of the sporange subsequently divides by another septum into a basal cell which develops into the pedicel, and an apical cell which becomes the capsule. The pedicel usually consists ultimately of three rows of cells produced by longitudinal and transverse divisions. The nearly hemispherical mother-cell of the capsule first divides, by four successive oblique walls, into four parietal and a nearly cubical central cell, the archespore. In the parietal cells further divisions follow at right angles to the surface ; while from the archespore are formed four tabular segments parallel to the parietal cells, which again divide by walls vertical to the surface into one or two layers of tapetal or mantle-cells^ constituting together the tapete. The row of cells in the wall of the sporange which constitute the annulus are the result of divisions at right angles to the surface of the sporange ; their outer walls bulge out and project above the surface. The tapetal cells ultimately disappear, and the whole of the space within the wall of the capsule is occupied by a fluid, in which float the mother-cells of the spores formed by successive bipartitions of the archespore, and nor- mally sixteen in number in the Polypodiaceae and Schizaeaceae. In these families the formation of the spores takes place in the following way. Each of the sixteen spore-mother-cells divides into four by two succes- sive bipartitions of the protoplasmic contents, preceded by correspond- ing divisions of the nuclei. Sixty-four spores are thus normally formed in each sporange. They then invest themselves with a cell- wall, which is usually double, consisting of an inner coat, or endospore, generally but not always composed of cellulose, and sometimes itself consisting of two layers, and an outer brown cuticularised exospore, provided with ridges, papillae, warts, or other elevations. Leitgeb states that in Osmunda and some other genera there is no true endospore ; while in Onoclea (L.), according to Campbell, there are three coats. The spores of the Osmundaceae and Hymenophyllaceas contain chlorophyll. Another mode of spore-formation, more analogous to what takes place FILICES 8 1 in the formation of the pollen of Flowering Plants, occurs sometimes in the two orders just named, and invariably in the Cyatheacese, Osmun- daceas, and Hymenophyllace^. Each spore-mother-cell divides at once by cell-walls of cellulose into four compartments, sometimes called ' special mother-cells ' ; within each of these compartments the spores become invested with their permanent cell-walls, both the walls of the original mother-cells and their septa being then absorbed. The spores formed in this way have a rounded cubical shape, while those produced in the mode first described are bilateral, and very commonly kidney- shaped. In the Schizgeaceae and Osmundacese the sporanges are not strictly trichomic in their origin, being formed, before the differentiation oi the epiderm, each from a single cell, which may be regarded as the rudiment of a leaf-branch. In both these orders the number of spores produced in a sporange is much larger than in the Polypodiace^ ; in this and in other respects they manifest an approximation to the Marat- tiacese and Ophioglossaceae. The sporanges of ^Marattiaceas are alto- gether endogenous in their origin, being developed from an internal mass of tissue, and are destitute of an annulus. On the dehiscence of the normal sporange the spores are at first attached to the annulus, and are detached and thrown to a distance by its sudden return to its original position. The spores of many Polypodiaceae retain their vitality and power of germination for a long period, and require a longer or shorter period of rest before germination ; those of the Hymenophylla- ceae, on the other hand, often begin to germinate while still enclosed in the sporange. In Scolopendrium (Sm.), according to Beck (Verhandl. Zool.-Bot. Ges. Wien, 1879), the exospore does not burst, but decays at the spot where the germinating filament emerges. The non-sexual propagation of ferns takes place chiefly by means of the adventitious buds already described, which appear on the lamina or petiole of the leaf (fig. 49). As a normal phenomenon it is, however, con- fined to a small number of species known in cultivation as viviparous or bulbiferous ferns, such as Asplenium bulbiferum (Forst.) and Cvstopteris bulbifera (Bernh.). The occasional vegetative propagation of the prothallium has also been already described. Ferns are distributed over the whole globe, from the equator to the arctic zone ; and, from the ease of their culture and the beautv of their forms, are favourite objects of cultivation. They are most abundant in moist warm climates, and hence enter largely into the composition of all insular floras. In the tropics a large number of species are epiphytic ; and it is only there, and in the islands of the Southern Hemisphere, that they attain the size of tree-ferns. One or two species are annual, and a single one, Ceratopteris thalictroides, is aquatic, while a very few have a G / 82 VASCULAR CRYPTOGAMS climbing habit. The number of species which are at the present time apphed to any economical purpose is extremely small. The common brake, Pteris aquilina, is largely used throughout Northern Europe for forage purposes, and for the stuffing of rough beds and pillows. The so- called ' male fern,' Aspidium fiUx-mas, has a very ancient repute as a vermifuge, and is still occasionally employed for that purpose, as also are several other species to a less extent in different parts of the globe, either for a similar purpose or as astringents and mucilages. In several species, especially tropical, the stem contains sufficient starch to be esculent. The number of known species of ferns is at present estimated at about 3,000, but it is constantly and rapidly increasing. They are arranged in a comparatively small number of genera, the limits of which are often extremely difficult to define. Literature. iSIettenius — Filices Hort. Bot. Lipsiensis, 1856. Hofmeister — Abhandl. Sachs. Gesell. Wiss. , vol. v., 1857 ; and Pringsheim's Jahrb. wiss. Bot., 1863, p. 278. Wigand — Botanische Untersuchungen, 1854. Newman — History of British Ferns, 4th ed., 1865. Reess — (Sporange) Pringsheim's Jahrb. wiss. Bot., 1867, p. 217. Strasburger— (Fertilisation) ibid., 1 869, p. 390. Kny— (Antherid) Monber. Akad. ^Yiss. Berlin, 1869, p. 416 ; and Pringsheim's Jahrb. wiss. Bot., 1869, p. i. Plooker and Baker— Synopsis Filicum, 1868. Goebel — (Prothallimn of Gymnogramme) Bot. Zeit., 1877, pp. 671 et seq. \Yeiss— (Bundle-sheath) Flora, 1880, p. 119. Cramer — (Fertilisation) Denkschr. Schweiz. Naturf. Gesell., 1880. Haberlandt — (Vascular Bundles) Sitzber. Akad. Wiss. Wien, Ixxxiv. , 1881, p. 121. Lachmann— (Root-organs) Compt. Rend,, xcviii., 18S4, p. 833 ; and ci., 1885, p. 592. Klein— Bot. Zeit., 1884, pp. 577 et seq. Schmidt— (Dehiscence of Sporange) Flora, 1885, pp. 451, 471, and 1887, pp. 177, 202 ; and Ber. Deutsch. Bot. Ges., 1886, p. 396. Campbell- (ProthalHum) Bot. Gazette, 1885, p. 355. Thomte— (Leaf-stalk) Pringsheim's Jahrb. wiss. Bot., 1886, p. 99, Goebeler— (Pales) Flora, 1886, pp. 451 et seq. Gardiner and Ito— (Mucilage-cells) Ann. of Bot., i., 1887, p. 27. Campbell — (Struthiopteris germanica) Mem. Boston Soc. Nat. Hist., 1887, p. 17. Klindig — (Sporange) Hedwigia, 1888, p. I. The following classification of the Filices into families or orders follows partly the plan proposed by Mettenius, partly that adopted in Hooker and Baker's ' Synopsis Filicum.' It must, however, be distinctly borne in mind that the divisions are of very unequal value. The first three are closely allied to one another ; the Hymenophyllaceae show con- FILICES U siderably greater divergence ; the affinity of Osmundacese and Schiz^eaceae with the typical ferns is more remote ; while the Marattiaceae exhibit so many points of divergence that some high authorities have removed them altogether from the FiHces. Order i. — Polypodiace.^. This order includes by far the largest number of genera and species, and may be regarded as the typical family of ferns. The sporanges arise out of single epidermal cells, and have usually long pedicels ; they Fig. 57. — Ahophila aculeata Klotzsch, a tree-fern (reduced). have an incomplete vertical annulus, and consequently dehisce trans- versely. The sori vary greatly in size and form, and usually consist of a large number of sporanges. They are seated on the under side of the divided or undivided leaf, upon the veins ; much less often (Acrostichese) also on the upper surface or in connection with the mesophyll ; they are usually covered by an indusium in the Asplenieae, Aspidieae, and Davallicce, but not in the Acrostichese or Polypodieae. In the great majority of species all the leaves are ultimately fertile; but in some genera (Gymnogramme (Desv.), Lomaria (Willd.), Platycerium (Desv.), &C.) G 2 84 VASCULAR CRYPTOGAMS there are" species with liarren and fertile leaves, differing from one another in habit and in degree of segmentation ; in other heterophyllous Fig. 58.— Sori of Polypodiaceae (variously magnified), a, b, Adiantutjz ; c, Lindsaya ; d, e, Blechnuni ; f,g, Cystopte7-is ; h. i, Davallia ; k, /, Cheilanthes ; w, n, Pteris ; 0, p, IVoodivardia ; g, Scolopen- driuin; r,s, Asplenintn; t, Aspidhan ; n,v, IVoodsia ; w, Gymnogiamiite ; x, z, Polypoduan. (After Luerssen.) ferns (species of Polypodium) both forms of leaf are fertile. A few of the Polypodieas are arborescent '^Dicksonia L'Herit.). FTLICES 85 Principal genera : — Adiantum (L.), Cheilanthes (Sw.), PellEea (Link), Pteris (L.), Lomaria (Willd.), Blechnum (L.), Woodwardia (Sm.), Doodia (R. Br.), Asplenium (L.), Scolopendrium (Sm.), Aspidium (Sw.), Xephro- dium(Rich.), Lastrea(Presl), Xephrolepis (Sch.), Polypodium(L.), Notho- cljena (R. Br.), Gymnogramme (Desv.), Hermonitis (L.), Vittaria (Sm.), Acrostichum (L.), Platycerium (Desv.), Onoclea (L.), Woodsia (R. Br.), Ceterach (Adans.), Dicksonia (L'Herit.), Davallia (Sm.), Cystopteris (Bernh.), Lindsaya (Dry). ■i///*'j- Order 2. — Cyatheace.e. This order is not distinguished from the Polypodiaceae by any very clear hnes of demarcation. The sporanges are epidermal and shortly stalked ; they have a complete oblique eccentric annulus. The sori are seated on a receptacle or placenta which often projects consider- ably ; they are naked, or are more often enclosed in a cup-shaped indusium or ' involucre,' which some- times forms a closed cup opening by a transverse fissure ; the sporanges are densely crowded in the sorus. The greater number of the tree-ferns belong to this family (fig. 57). The leaves are often ver}' large (five to ten feet in length), and usually compoundly pinnate, forming a rosette at the summit of the columnar unbranched arborescent stem, which is densely covered with aerial roots, especially in its lower portion, and is marked in a diamond pattern by the scars of fallen leaves. In some species, in addition to the ordinary cylinder of ' vascular ' bundles, there are a number of accessory bundles distributed through the medulla and cortex, forming a delicate open network. Crystals of calcium oxalate are not uncommon in the epidermal cells. Principal genera : — Cyathea (Sm.), Hemitelia (Br.), Alsophila (R. Br.). Fig. 59. — Sorus of O'^M^"^, with open indusium (mag- nified). Order J' ■Gleicheniace.e. The sporanges are epidermal and sessile, with a broad complete transverse annulus running nearly hori- zontally, and hence with vertical dehiscence. The sori are naked, on the under side of ordinary leaves, and usually consist of only three or four sporanges. The stem is a slender creeping rhizome ; the leaves are usually very large, and with peculiar buds or ' innovations ' on the lamina. Principal gefiera : — Gleichenia (Sm.), Mertensia (Willd.). Fig. 60, — Sporange of Gleichenia (magnified). 86 VASCULAR CRYPTOGAMS Order 4.— Hvmknophvllace^e. The oophyte generation is known l)ut in a very few species of HymenophyllacecT Where it has been observed (some species of Hymeno})hyllum and Trichomanes) it differs from that of other ferns, and IS usually filiform, closely resembling the protoneme of a moss, but somewhat coarser. Antherids appear to be produced at the middle of these filaments, and archegones at their extremity. But apogamy is much more common in the Hymenophyllace?e than in any other family of ferns, and it is doubtful whether it does not even occur regularly in some species. Bulbils or gemmae are produced abundantly on the pro- thallium, consisting of a small number of cells, and borne on pedicels or sterigmas. They germinate with extreme slowness. In Trichomanes pyxidiferum (L.) the prothallium is frequently an aposporous growth, derived from imperfect arrested sporanges, or even from cells of the placenta. The archegones are borne on peculiar structures, known as archegoniophores^ mas- sive outgrowths of the prothal- lium, each archegoniophore bear- ing either a single archegone or several. The archegoniophore is usually a multicellular structure, Fig. 61.— Archegoniophore of Trichomanes pyxi- and the VCntCrS of the archcgOnCS diferjivi L., bearing five archegones, ar. of • i -s i i • • • r-r^ different ages (x 175). (After Bower.) are Ullbedded m itS tlSSUC. 1. alatum (Sw\) is habitually apo- gamous, and is possibly never reproduced sexually. Aposporous pro- thallia spring in great numbers from all parts of the frond, often quite independent of the sori, and are more flattened and ribbon-like in struc- ture than those of most Hymenophyllaceae. They produce large numbers of stalked gemmae. Archegones have never been observed in this species, and the antherids are imperfect, and apparently functionless The spores are multicellular before germination. The archegones differ from those of other ferns in having a perfectly straight neck. The sporanges have a complete horizontal or oblique annulus (incomplete in Loxsoma, R. Br.), and hence dehisce by a vertical fissure. They are borne on a prolongation of the fertile vein, the cohwiel, which projects beyond the margin of the leaf, and is enclosed in the cup-shaped indusium. The columel or placenta elongates by intercalary growth, and the sporanges are produced on it in a spiral line in basifugal succes- FILICES 87 sion. In Hymenophyllum (L.) and Trichomanes (Sm.) the sporanges are sessile and biconvex, and are attached to the columel by one of their convex faces ; the annulus, projecting in the form of a cushion, separates the two convexities, and is usually oblique, dividing the circumference into two unequal portions : in Loxsoma they are pear-shaped and dis- tinctly stalked. Para- physes occur only in a few species of Hymeno- phyllum. The meso- phyll of the leaf consists, in the two larger genera, of onlv a single laver of cells, and the leaves have hence a filmv and Fig. 63. — H yincnophylhmi •, spo- ranges exposed (niagnified). moss -like appearance ; but in Loxsoma there are several layers of cells, and the leaf is then provided with stomates. The stem is generally creeping and mostly very slender, and is pene- trated by a single axial Fig. 62. — Hymenophylhan tnnhridgense (natural size). 'vaSCUlar' bundle. ]Many species of Trichomanes are rootless ; and the stem is then densely clothed with root-hairs, and slender ramifications of the stem assume the appearance and function of true roots. Even the ordinary branches of the stem have often been long formed before their leaves emerge from a rudimentary condition. In some species of Trichomanes the fructifica- tion is confined to special fertile leaves. The Hymenophyllace^e include but three genera, of which Loxsoma comprises a single species only, of creeping habit, native of New 88 VASCULAR CRYPTOGAMS (X I2o). Zealand ; Hymenophyl- lum and Trichomanes nearly loo species each, exceedingly delicate and graceful ferns, growing mostly on the trunks of trees and damp rocks, often within reach of the spray of waterfalls, in the moister and warmer parts of the globe. The smaller species of Hymenophyl- lum are known as ' filmy ferns.' The Hymeno- phyllacese may be re- . . J , „. , „ garded as the simplest Fig. 64,.— a, germinating spore and prothallmm of Hyiizcno- » '• j>hyllnm\ B, C, D, stages in development of prothallium andarcprobably the oldeSt (After Luerssen.) ^ ^^ r r j family of ferns, and pos- sibly form a connecting link be- tween the Muscinese and the Vas- \ cular Cryptogams. Literature. Mettenius — Ueber die Hymenophyl- laceen, 1864. Janczewski and Rostafinski — (Prothal- lium) Mem. Soc. Nat. Sc. Cher- bourg, xix., 1875. Goebel— (Germination) Ann. Jard. Bot. Buitenzorg, vii., 1887, p. 57. Prantl— Untersuchungen zur Morpho- logic der(^efasskryptogamen, Heft I. Bower — Annals of Botany, vol. i., 1887, pp. 183 and 269. Order 5. — Osmundace^e. The prothaUium of the Os- mundacese is characterised by its strong tendency to propagate itself vegetatively, by means of adventi- tious shoots, and is commonly dioecious, springing directly from Fig. 65.-Prothaiiium of Osmunda the spore. It is usually ribbon- regaiis L. a, antherids ; w, ghapcd, with a wcll- defined midrib rhizoids; 7', growing point. (After ^'■'- r^ J Goebel.) FILICES 89 The sessile or shortly stalked, roundish, but unsymmetrical sporanges are not strictly epidermal in their origin. They bear on one side of their apex a modified annulus in the form of a group of cells of peculiar form, and dehisce vertically on the other side. Todea (Willd.) presents no difference between the fertile and sterile leaves ; while in Osmunda(L.)the fructification has the appearance of a con- tinuous or interrupted panicle, Fig. 67. — Mucilage-gland from Osiminda r^^a//^ (magnified). (After Gardiner.) from the entire absorption of the mesophyll of the fertile part of the leaf. In some species of Todea the leaf con- sists of only a single layer of cells. In Osmunda there are Fig. 68. — Sporange of Osimmda (magnified). abundant mucilage-cells at the base of the leaf-stalk. The ' vascular ' bundles of the stem are collateral, as con- trasted with the concentric bundles of typical ferns, and their course bears more resemblance to that in Gymnosperms and in Dicotyledons. In the structure of the leaves, and in the structure and development of the growing point, Osmundaceae exhibit a transitional condition between the typical ferns Fig. 66. — Osmunda regalis L. (natural size). Portion of frond 90 VASCULAR CRYPTOGAMS and the Marattiacece. The young leaves (in Osmunda cinnamomea, L., and Todea superba, Col.) present the remarkable peculiarity of their apex being occupied by a well-marked triangular-conical apical cell. The family includes only a very small number of species, comprised in the two genera Osmunda (L.) and Todea (Willd.). Osmunda regalis (L.), growing in bogs, with remarkably coriaceous leaves, is our ' royal fern ' or ' flowering fern.' Literature. Bower — Proc. Roy. Soc, xxxvii., 1884, p. 42; and Quart. Journ. Micr. Sc. , 1885, p. 75. Gardiner and Ito — Annals of Botany, vol. i., 1887, p. 27. Order 6. — Schiz^ace^e. The ovoid or pear-shaped sessile spo- ranges are not strictly epidermal in their origin. The apex of the sporange is occu- pied by a cap-like zone of cells of peculiar form, and the dehiscence is vertical. In the genera Aneimia (Sw.) and Schizaea (Sm.) the fertile leaves have the paniculate appearance of an Osmunda. In Schizaea and Lygodium (Sw.) the sporanges are seated in two rows on the under side of very narrow pinnae ; and in Lygodium each sporange is enclosed in a pocket-shaped indusium. In Aneimia the two lowermost pinnae form a long-stalked panicle, from which the meso- phyll has disappeared. In Aneimia and Lygodium the sporanges spring originally from the margin of the leaf, but are eventu- ally placed in the course of development on its under side. In Mohria (Sw.) they are placed on the back of the leaf, and are con- cealed by its recurved margin. The differ- entiation of tissues, both in the mesophyll of the leaf and in the 'vascular' bundles, is very slight. The stem is in general but feebly developed, and seldom branches ; the leaf-stalk is penetrated by only a single ' vascular ' bundle. The peculiar position of the stomates in some species of Aneimia has already been described. Fig. 69.- -Lygodhim pah7iaUivi Sw. (reduced). FILICES 91 The family of Schizaeace^e comprises a small number of species, in- cluded in five genera, of which Mohria(Sw.)and Trochopteris (Gardn.)are monotypic. Aneimia (Sw.) and Schizaea (Sm.) resemble the Osmundaceae in their paniculate appearance. All the species of Lygodium (Sw.) pre- sent the appearance of climbing stems, from the peculiar structure and mode of growth of the leaves already described. The family is confined to the warmer parts of the globe. Literature. Prantl — Untersuchungen zur Morphologic der Gefasski^'ptogamen, Heft 2, iSSi ; also in Engler's Jahrb. i88i, p. 297. Order 7. — Marattiace^. The Marattiaceae differ more widely from the typical ferns than any of the families hitherto described, and are by many authorities separated from them into a distinct class. But the point of divergence most relied on, the endogenous origin of the sporanges, has lost much of its signifi- cance since it has been known that the Osmundaceae and Schiz^aceae present connecting links in this respect. The aerial flat prothallium, the circinate vernation and general structure of the leaf, and the ultimate structure of the sori, present so many points of contact with the other orders of Filices, that it seems most desirable at present to retain them as an aberrant order of the class. The prothallium, the development of which is very slow, is a dark green elliptical or heart-shaped plate of tissue, lying on the surface of the soil, consisting of one or more layers of cells, and with a projecting hemispherical cushion on the under side. Its development has been followed out in Marattia (Sm. ) and Angiopteris (Hoffm.). Chlorophyll is formed in the spore as soon as it begins to germinate. The exospore bursts, and the first cell of the prothallium projects as a papilla between the two lobes. After a considerable time the first division takes place at right angles to the direction of growth, and the first rhizoid is formed. Further divisions follow rapidly, and the prothallium soon becomes a cellular tissue, and is distinguished from that of typical ferns by its deep green colour and by its moderately thick cuticle. One of the cells first formed becomes an apical cell, from which fresh cells are formed until the prothallium has assumed its ultimate cordate form. The antherids make their appearance, after a period of some months, on both sides of the prothallium, but especially on the ventral cushion. Their structure differs in some respects from that of typical ferns. From a single superficial cell are produced a central cell, two upper cells, and a triangular stigmatic cell, which is thrown off when the antherid is 92 VASCULAR CRYPTOGAMS mature. Within the central cell are produced from twenty to two hundred antherozoids, each in its own mother-cell. Both antherids and arche- gones are deeply sunk in the tissue of the prothallium. The archegones, only the uppermost part of the neck of which appears above the surface, are formed on the ventral cushion, very rarely on the upper side of the prothallium. Their development presents no very special features. The sporophyte generation has, when mature, the habit and appear- ance of an ordinary fern. The stem is usually erect and short, with tuberous base, never attaining a greater height than from one to two feet ; less often (Kaulfussia, Bl.) a creeping underground rhizome. It resembles the stem of Ophioglossaceae and Isoeteae in never branching ; that of true ferns in being densely covered, when erect, with leaves as well as with roots, so that no portion is left exposed. The growing point has a single apical cell, and is concealed in a terminal rosette of large leaves. The fundamental tissue is everywhere traversed by long rows of tannin-cells ; and lysigenous mucilage-cells abound in the petioles and in the parenchyme of the pith and cortex of the stem ; they anasto- mose freely, and are continuous from the stem into the roots. The sclerenchymatous tissue, so characteristic of the parenchyme of the stem of typical ferns, is but feebly developed, or is alto- gether wanting, in the Marattiaceae. The ' vascu- ^, ^ „ ^ lar' bundles are concentric, and resemble those r IG. 70. — Base of leaf-stalk of Marattia cut through, st, of truc fcms. A Central xylcm, composcd of widc stipule; c, commissure; v, ^ -r ^ ■ ^ • i i 1 1 anterior, k, posterior wing scalaritomi tracheides, IS surrounded by the (natural size). (After Sachs.) phloem; the bundle-shcath IS Wanting in the bundles belonging to the stem and leaves, but is present in those of the root. The bundles bend from the stem into the leaves in the ordinary way. The stem and rachis of the leaves are not covered with pales, as in true ferns, nor are they completely glabrous, as in the Ophioglossaceae. The leaves are thick, coriaceous, and very large, attaining in some species a length of from five to ten feet. They have a long and very stout petiole, which is channelled on the upper side ; the lamina unfolds very slowly, and is either simply or doubly pinnate, less often palmate or digitate. They are furnished at their base with appendages peculiar 10 the Marattiaceae among Vascular Cryptogams, the stipules or auricles. While still in the bud the leaves are rolled up in a circinate manner, and are entirely enveloped in the large stipules until the lamina unfolds. The pair of stipules belonging to each petiole form an anterior and a posterior chamber, separated from one another by a longitudinal wall termed the commissure. In the posterior chamber is the rolled-up leaf FILICES 93 to which the stipules belong, the two posterior wings of the stipule being folded together behind it ; while the chamber formed by the anterior wings encloses all the younger leaves. The stipules remain succulent, not merely as long as the leaves last, but even after the lamina has fallen off; and adventitious buds are not unfrequent upon them. The leaf-stalk is articulated immediately above the stipule ; the leaf always becomes detached at this articulation by a smooth scar, leaving behind the base of the leaf-stalk with its succulent stipules. The primary and secondary pinnae are attached to their respective rachis by similar articulations ; and at each articulation is tx. piclvimis or cushion, containing collenchymatous tissue. In the mesophyll of the leaf occur, in all the genera, outgrowths of the cell-walls bounding the intercellular spaces and projecting into them. Where the intercellular spaces are small these outgrowths have the form of humps and cones : in larger spaces they elongate into long slender filaments which present a super- ficial resemblance to the hyphas of Fungi, but are quite solid, and consist of cuticularised cellulose. Thev are found also less abundantlv in the leaf-stalk, stem, and root. Layers and bundles of sclerenchyme occur in the mesophyll, but are only feebly developed and of a light colour. The leaves of Kaulfussia are characterised by the presence of remarkably large stomates on the under side, formed in the ordinary way, but dis- tinguished by the great size of the orifice, and by the guard-cells forming a narrow ring, and being surrounded by two or three layers of epidermal cells, which are also arranged in a ring. There are only two semicir- cular guard-cells, and the structure of these organs is ver}' different from that of the stomates of Marchantia, to which they bear a superficial resemblance. Lenticels occur in the leaf-stalk of many species. Spherocrystals have been found in the mesophyll and leaf-stalk of Marattia cicutaefolia (Kaulf.) and Angiopteris evecta (Hoffm.). The roots arise endoo;enouslv from immediatelv beneath the s;rowin2; point of the stem. They strike obliquely downwards through the succulent parenchyme of the stem, penetrating the network of the ' vascular 'bundles, with which thev mav easilv be confounded, and srene- rally emerging from a leaf-stalk. They are of a lighter colour, greater thickness, and more delicate texture than those of true ferns, approach- ing those of Ophioglossaceae. After entering the soil they branch copiously and apparently monopodially. The sporanges are produced in large numbers on the under side of ordinary leaves, each being developed, not from a single cell, but from a group of cells. They are situated on the veins, and usually form two rows of sori, which cover the lateral veins either for their whole length or only near the margin of the leaf ; in Kaulfussia they are placed on 94 VASCULAR CRYPTOGAMS fine anastomosing branches between the lateral veins. The placenta or receptacle on which each sorus is seated is a cushion-like outgrowth of the vein. The sporanges are altogether destitute of an annulus ; the wall always consists of several layers of cells. In Angiopteris the sporanges which make up a sorus are quite distinct, ovoid, and sessile, and dehisce by a vertical fissure on the inner side. In all the other genera they are more or less confluent, and the entire boat-shaped sorus is then known as a synange ; but each sporange still dehisces separately by a vertical slit on its inner side ; or, in Dan^a, by an apical pore. The coalescence is most complete in Kaulfussia, where the circular sorus has the appearance of a plurilocular basin. The sorus is usually surrounded by flat lobed hairs of epidermal origin, forming a kind of Fig. 71. — A, under side o{\&2S o{ Amiopteris caudata ; B, o{ Marattia ; i'. sori ; C, sorus of Marattia cut through, showing open sporanges. (After Goebel.) involucre. The true indusium is sometimes altogether wanting. The sporanges originate from the tissue of the leaf itself. The placenta is first formed as a cushion-like outgrowth of the fertile vein, partly from the epiderm, partly from the subjacent tissue. On this originate, in Angiopteris, the separate sporanges as papillae, each composed of a number of cells. In Marattia, however, while the two rows of sporanges are distinct, those of each row are confluent from the first, but each has its own archespore. The primary mother-cells of the spores are formed at an early period within the archespore. The spores are formed in fours within their parent-cells, and resemble in general character those of typical ferns. Two different forms of spore sometimes occur in the same species, but they present no difference on FILICES 95 germination. The wall of the spore is composed of three layers ; the surface is covered by minute wart-like spines. Vegetative propagation takes place with great facility in some species of this family. In ^Nlarattia cicutaefolia the leaves, or even the stipules, have only to be cut into small pieces, and placed in damp soil or in a bottle, when a number of adventitious buds will be developed in con- nection with the ' vascular ' bundles. The Marattiace^e comprise only a very small number of species, almost entirely confined to the tropics, and included in the four genera Angiopteris (Hoffm.), Marattia (Sm.), Dan^ea (Sw^), and Kaulfussia(Bl.). With the exception of the stipules, and the great thickness of the leaves, they have quite the habit of ordinary ferns. Literature. De Vriese and Harting — Monographic des Marattiacees, 1853. Mettenius — Ueber den Bau von Angiopteris, 1863. Luerssen — Mittheil. aus dem Gesammtgebiete der Bot., vol. i., Heft 3, 1872; and Bot. Zeit., 1872, p. 768 ; and 1873, pp. 624 and 641. Riissow — Vergleichende Untersuchungen, 1872, p. 185. Holle— Bot. Zeit., 1875, P- 215. Jonkman — Bot. Zeit., 1878, p. 129; and Archives Xeerland., 1S80. Schenk— Ber. Deutsch. Bot. Gesell., 1S86, p. Z(i. Class v.— Ophioglossaceae. This small but very well-defined group, although popularly included with the Filices under the common denomination of ferns, differs from them in several important points of structure, in some of which a con- necting link is furnished by the Marattiacese. The prothallium is under- ground and destitute of chlorophyll, exhibiting a similarity to that of Lycopodiaceae rather than to that of true ferns. The stem rarely at- tains more than a few inches in height, and usually does not branch ; it is remarkable for its slowness in growth. It contains no sclerenchy- matous layers. The leaves are not circinate in vernation, and the petiole is furnished at the base with lateral outgrowths, which have been compared to the stipules of Marattiacese. The venation is dicho- tomous or reticulate, and generally inconspicuous. The sporanges are completely endogenous in their origin, and are never borne on the under side of the green leaf, but on a separate branch of the leaf, altogether destitute of green parenchyme, and form a compound 'fructification,' resembling in appearance a spike or panicle : there is no annulus. The 96 VASCULAR CRYPTOGAMS ' vascular ' bundles of the stem are collateral ; the primitive elements of the xylem are usually scalariform tracheides. The oophyte generation has been observed in only a few species. In Fig. j2.—Oj>hiogloss2aji vnl^atnm L. A, p'ant (natural size) ; B, portion of sporophyll (magnified). Ophioglossum (pedunculosum, Desv.) it has at first the form of a small round parenchymatous tuber, entirely buried in the soil and destitute of chlorophyll, from which is subsequently developed a cylindrical vermiform shoot, which grows erect by means of a single apical cell, OPHIO GL OSS A CE^ 97 and very rarely branches, and then but sh'ghtly. The apex of this shoot finally appears above ground, develops chlorophyll, becomes lobed, and ceases to grow. Whan fully developed, the prothalliwn consists of an ^ axial bundle of elongated cells surrounded by shorter parenchymatous cells : its upper surface is clothed with rhizoids. Its length sometimes amounts to as much as two inches, though generally it is much shorter ; its breadth is always very small. In Botrychium (Lunaria, Sw.) the prothallium is a minute light brown or yel- lowish white ovoid mass of firm cellular tissue, subter- ^^ ranean and destitute of chlorophyll, and producing V rhizoids ft-om all sides. In both genera the prothallium ^ is monoecious, _) The archegor?es, antherids, and antherozoids do not > differ materiallv in structure from those of Filices. ftM Fig. 74. — Longitudinal section of prothallium o{ Botrychium Lunaria^ showing archegones and antherids (x 50). (After Hofmeister.; Neither archegones nor antherids are limited in their production to any particular part of the prothallium. In Botrychium (Sw.) the antherids are cavities in the tissue chiefly of the upper side of the prothallium, and the archegones are produced in their immediate vicinity; in Ophioglossum (T.. ) they project slightly above the surface. Before opening to discharge the anthero- zoids, they are covered by a few epidermal layers of cells. The mode of formation of the antherozoids resembles that of Marattiaceae. Their mother-cells originate from repeated divisions of one or two cells of the inner tissue lying beneath these layers. They are Lunaria Sw. (nat. comparatively large, and escape through a narrow open- ing in the layers of cells which originally covered the antherid. The archegone consists of a venter containing the central cell, and a neck composed of four vertical rows, each consisting of two or more cells, and only slightly projecting above the surface. The H X. Fig. 73. — Botrychium 98 VASCULAR CRYPTOGAMS venter is completely imbedded in the prothallium, its wall being de- veloped out of the tissue of the latter. The course of development of the embryo and rudimentary sporo phyte has not yet been followed out in a sufficient number of instances to warrant a general description ; in those in which it has at present been observed it appears to present some discrepancies. The short stem is erect and entirely glabrous, often with a swollen tuberous base ; only in Helminthostachys (Kaulf.) is there a creeping underground rhizome. In only a very few exceptional cases does it branch. The flattened apex of the stem consists of an irregular meristem derived from a single pyramidal apical cell. The fundamental tissue of the stem consists of short nearly cylindrical thin-walled succulent cells, which are longer in the leaf- stalk, interspersed with large intercellular spaces. It exhibits a striking difference from the corresponding tissue of true ferns in the entire absence of sclerenchymatous layers. It is separated by the ' vascular ' cylinder into a cortical and a medullary parenchyme. It has an epiderm well provided with stomates, and exhibits sometimes a remarkable development of layers of cork. The ' vascular ' bundles form (in Ophio- glossum vulgatum, L.) a hollow^ cylindrical network, from each mesh of which is sent out a leaf-trace. The whole of the tissue which fills up the meshes is frequently transformed into scalariform tracheides, so that considerable lengths of the stem then contain a continuous hollow cylinder of lignified tissue. The bundles of the stem are collateral, the xylem occupying the axial, the phloem the peripheral side ; and the structure is the same in Botrychium (Lunaria). Those of the leaf-stalk are four to eight in number, arranged in a circle and separated by fun- damental tissue. In Ophioglossum they are collateral, the axial portion consisting of narrow reticulate tracheides, the peripheral portion of a broad band of phloem, containing sieve-tubes ; while in Botrychium they are concentric, consisting of a broad band of scalariform or reticulate tracheides surrounded by a thick layer of phloem. There is no bundle- sheath in Ophioglossum, and only a rudimentary one in Botrychium. The roots of Ophioglossacese are remarkable from the slight develop- ment of the root-cap, and the absence of root-hairs. They spring from the short stem in the midst of the leaf-insertions, and rarely branch, then always monopodially. Like the stem, they originate from a single pyramidal apical cell. The roots of Ophioglossum give rise to adven- titious buds. The leaves are always very few in number, often only one on each stem, and the number is uniform in the same species. They are re- markable for the slowness of their growth, which extends, in Botrychium Lunaria, over five years, the leaf only rising above the surface of the OPHIOGLOSSA CE.E 99 soil at the commencement of the fifth year ; where there are several leaves, the points of origin of those of successive years have a spiral phyllotaxis. They are quite simple and entire, simply pinnate, or twice or thrice pinnate. There is always a long petiole, which is furnished with a ligular or sheath-like outgrowth on each side ; and the coalescence of these appendages forms a hollow chamber within which the leaf is developed, similarly to what takes place in Marattiaceas. They are never circinate in vernation. They are of coriaceous texture, and are always quite glabrous, and possess a well-defined epiderm furnished with stomates on both surfaces, and in immediate contact with the mesophyll, without any intermediate hypodermal layers. The mesophyll is large-celled and spongy, with large intercellular spaces. The 'vascular' bundles are Ijut feebly deve- loped ; they anastomose in Ophioglossum, but only dichotomise in Botrvchium and Helminthostachvs. In most species all the leaves are fertile ; but in Rhi- FlG. 76. — Ophioglos- siitnvtdgattan. Por- tion of sporophyll with closed spo- ranges, s \ g, ^ vas- cular ' bundle ( x 10). Fig. 75. — Botrychium Liinaria. Portion of sporophyll with open sporanges (magnified). (After Luersseu.) zoglossum (Presl) (a section of Ophioglossum) there are both barren and fertile leaves. The leaf divides at an early period into two branches — an outer branch which is sterile, and which alone develops chlorophyl- lous parenchyme ; and an inner fertile branch, the sporo- phyll^ which springs either from the base or middle of the lamina or from the leaf-stalk. This branch never has any green parenchyme except in Helmintho- stachys. The sporanges resemble in their origin and mode of formation those of Marattiaceae. They are not formed from a single cell, but from a group of cells in the substance of the sporophyll which are differentiated from the surrounding tissue. The terminal cell of the axial row beneath the epiderm is the archespore from which all the spores are formed : it is surrounded by the layers of mantle-cells constituting the tapete, which are formed out of the epidermal cell immediately above the archespore, and which ultimately disappear. The wall of the sporange, consisting of several layers of cells, is developed from the epiderm, and contains stomates. Strasburger regards each sporange as corresponding homologically to an entire sorus in the Filices — being, in fact, a meta- H 2 job VASCULAR CRYPTOGAMS morphosed portion of a leaf. They are buried, in an early stage, in parenchyme, which ultimately becomes entirely absorbed, and which is traversed by ' vascular ' bundles anastomosing into long meshes. The sporanges require an entire year for their complete development. They have no annulus, and dehisce vertically from unequal tension of the epidermal and hypodermal lavers of cells. In the formation of the spores each mother-cell divides into four ' special mother-cells,' with very thin cell-walls ; the protoplasm in each of these becomes invested with a new and firmer cell-wall, and the spores are thus completely formed, and are ultimately set free by the absorption of the walls both of the special mother-cells and of the original spore-mother-cells. The spores are nearly cubical ; the exospore is strongly cuticularised, and is furnished with prominent knobs and ridge. Vegetative propagation is known to take place only by means of adventitious buds produced on the roots. The Ophioglossace^e include only a ver}^ small number of species, comprised in the genera Ophioglossum (L,), Botn'chium (Sw.), and Helminthostachys (Kaulf.), spread over the whole globe. They are small plants, dying down each year, only a few species attaining the height of more than a foot, with a single or only a very few coriaceous leaves, and a conspicuous ' fructification,' which is simple and spicate in Ophio- glossum and Helminthostachys, branched and paniculate in Botrychium. They are of no known economic value. They are represented in our English flora by the ' adder's-tongue ' (Ophioglossum vulgatum, L.) and ' mooftwort ' (Botrychium Lunaria, Sw.). Literature. Mettenius — Filices Hcrt. Bot. Lipsiensis, 1856. Hofmeister — Abhandl. Sachs. Gesell. ^Yissenschaften, 1S57. Holle— Bot. Zeit., 1875, pp. 241 et seq. Prantl — Ber. Deutsch. Bot. Gesell., 1S83, pp. 155 and 348 ; and Jahrb. Bot. Gart. Berlin, 1SS4. Class VI. — Equisetacese. The Equisetaceae or Horsetails are a very small group of plants, con- sisting only of a small number of species, arranged in a single genus, of remarkably uniform and peculiar habit. The aerial stems, which are invariably erect or ascending, arise from a creeping underground rhizome, and are characterised by their perfect multilateral symmetry and verticil- late branching. The ascending stem is always elongated and slender, fluted with longitudinal furrows and ridges, and is remarkable for the EQUISETACE^ 101 Fig. 77. — Equisctum syl-'aticmn L. a, non-chlorophj-llous fertile branch : b, chlorophyllous fertile branch ; c, barren branch (reduced). I02 VASCULAR CRYPTOGAMS tendency dis])layed by the epidermal cells to deposit silica in their cell- walls. It is always divided into ver}' distinct nodes and internodes, and is furnished at the nodes with modified foliar organs of a membranous character, the leaf-sheaths^ the margin of which is split into a number of teeth. The tissue of the internodes is permeated by large intercellular air- canals. At the nodes the stem (except in some species the fertile stem) gives out a whorl of symmetrically arranged branches, which almost precisely resemble the main stem except in their smaller size and simpler structure, consisting of internodes and nodes furnished with leaf-sheaths ; but these secondary branches do not usually again branch. The stem and root increase in length by means of a single large pyramidal apical cell, which produces three rows of segments. The ' vascular ' bundles of the stem are but feebly developed, and contain but little xylem. Both stem and branches perform the function of leaves, contain chlorophyll, and are provided with stomates. The sporanges are never borne on the branches or leaves, but are collected into spicate or catkin-like ' fructifi- cations,' borne at the extremity either of ordinar}^ vegetative stems, or of special fertile stems which resemble the ordinary stems in structure, but contain no chlorophyll and do not branch. The sporanges spring from the inner side of the peltate scales of which these ' fructifications ' are composed : they dehisce by a longitudinal fissure, but have no annulus like those of ferns. The spores are distinguished from those of all other Vascular Cryptogams by being enclosed in four distinct coats, the outer- most of which ultimately breaks up into four ribbon-shaped strips, and detaches itself from the spore except at the point of junction of these strips, which are termed elaters. The elaters are remarkably hygroscopic, absorbing or giving off water with every change in the moisture of the sur- rounding atmosphere. In consequence of this they are constantly altering their shape, and imparting a somewhat rapid motion to the spores, thus assisting in their dissemination. On germinating the spore gives rise to a strap-shaped prothallium, which has an independent power of growth, and is usually dioecious. The antherids and archegones differ in no essential point from those of other Vascular Cryptogams. Male and female prothallia are generally produced in close proximity to one another, so that impregnation is readily effected through the agency of moisture. The oophyte generation of Equisetum (L.) springs directly from the spore, which contains chlorophyll. On germinating the spore throws off its outer coats, and changes its form from spherical to pear-shaped. The contents, still clothed in the thin endospore, then divide by a wall, the direction of which is not constant, into two cells of unequal size ; accord- ing to Stahl the direction of this division depends on the direction of the rays of light. From the smaller of these two cells the chlorophyll EQUISETACE^ 103 rapidly disappears entirely ; it undergoes no further division, but elongates rapidly into a long hyaline rhizoid. The larger of the two primary cells, which still contains abundance of chlorophyll, divides further by walls, at first in two directions only, into a multicellular plate which increases rapidly by apical growth, and soon branches in one plane. A difference is now set up between the develop- ment of the male and female pro- thallia. The former remain com.- paratively small and narrow, and the cell-division continues in the Fig. 78. — A, male prothallium of Eqtdsetrijn arvense L. ; a, antherids ( x 200). (After Hof- meister.) B — jET, antherozoids of ^. niaxii)iiim Lam. in different stages of development (X1200). (After Schacht.) two directions only : they consist, therefore, permanently of only a single layer of cells, and display but little lobing. Their colour is yellowish green. The female pro- thallia, on the other hand, grow to a considerably larger size, as nmch as half an inch in length, are of a deeper green colour, and at an early period form a number of lobes at their anterior portion, which consist of masses of merismatic tissue, cell- division taking place in the tangential as well as the other two directions ; they branch also in the same plane much more abundantly than the male prothallia. The formation of female or male prothallia appears to depend Fig. 79. — Vertical section of lobe of female pro- thallium of E. art'ense. a, archegones ; //, rhizoids ( x 600). (After Goebel.) ro4 VASCULAR CRYPTOGAMS on the greater or less supply of nutriment. The antherids make their appearance about five weeks after germination, the archegones not till much later. The antherids arise at the extremity or margin of the male prothallia. They are first separated off as papillae by a tangential wall ; further divisions then arise, by which they are divided into a large central cell and a single layer of much smaller peripheral 'mantle-cells.' The contents of the central cell then divide into the mother-cells of the antherozoids. These escape, still enclosed in the delicate wall of the 'special mother-cell,' by the separation from one another, through the action of water, of the apical cells of the mantle-layer ; the expulsion often takes place with considerable force, and is due to the swelling up of the walls of the mother-cells; sometimes they emerge still all united together into a ball. The antherozoids are much more numerous than in ferns ; probably several hundreds are formed in each antherid ; they are also much larger, being the largest in any class of Cryptogams. Each anthero- zoid (see fig. 78) is a thread of pro- toplasm, gradually narrowing from the posterior to the anterior end, where it is coiled spirally, and bears a tuft of very long delicate vibratile cilia. The posterior portion is widened into a thin membranous fin-like expansion, by the undula- tions of which its motion through the water is greatly assisted, and may continue for many hours. To the posterior portion of the antherozoid is also frequently attached for a time a minute bladder containing starch, which is regarded by some as the wall of the special mother-cell, by others as a vesicle contained in it. The body of the antherozoid appears to be formed from the nucleus of the mother-cell, its cilia from the cell-protoplasm. The archegones are formed on the under (shaded) side of the thick lobed portions of the female prothallia, a lobe being usually situated immediately beneath an archegone, and assisting in its impregnation by retaining water. By the continued growth of the subjacent tissue they are ultimately pushed on to the upper surface, and hence the direction of growth of the archegone is the opposite of that of ferns. Otherwise Fig. 80. — Portion of female prothallium of E. sylvaticum, with projecting archegone, ar. (Alter Buchtien, greatly magnified.) EQUISETACE.iZ 105 the mode of development and structure of the archegones of Equisetum differ in no essential respect from those of other Vascular Cryptogams. The basal cell is wanting, and the neck-canal-cell does not extend the whole length of the neck. The lower portion of the neck and the venter remain completely imbedded in the tissue of the prothallium, while the outermost or stigmatic cells of the neck lengthen greatly, and ultimately bend outwards, giving to the archegone, when ready for impregnation, the appearance of a miniature four-armed anchor. Although the prothallium of Equisetum is normally dioecious, it is not very uncommon to find a few archegones on male, and a few antherids on female prothallia. The abnormal sexual organs then generally make their appearance later than the normal ones. The mode of formation of the embryo from the impregnated oosperm is essentially the same as in other classes of Vascular Cryptogams. The first division-wall is vertical to the axis of the archegone, and therefore parallel to the surface of the prothallium ; by subsequent walls a division takes place into octants. Of the four quadrants of the upper half, one gives birth to the rudimentary stem^ with a triangular pyramidal apical cell, while from the three others proceed two cotyledons^ which at a very early period unite in their growth with the first leaf which proceeds from the apex of the stem. From the lower quadrants of the octant are formed the /oof and the first roof. The first few stems of the sporophyte generation are successively thicker, and with a larger number of teeth in their leaf-sheaths, until ultimately mature stems are produced from perennial underground rhizomes. The stem of Equisetum always consists of very distinct more or less elongated internodes, which are hollow, but are closed above and below at the nodes by transverse septa or diaphragms. The cortex of each internode is continued upwards above its upper node into a leaf-sheath., which embraces the base of the next internode above, and is split at its margin into teeth., varying from three or four to a considerable number. From each tooth of the leaf-sheath a ' vascular ' bundle descends verti- cally as far as the next node. The teeth at each node always alternate in position with those of the leaf-sheaths belonging to the nodes next above and next below it, and each descending bundle branches at the node into two short diverging arms, each with its own xylem and phloem, by means of which it unites with the two adjacent bundles of the next internode below, where they descend into it from the sheath-teeth in which they originate. In addition to the large central cavity in the axis of each internode, the cortical tissue contains a number of much smaller cavities running vertically through the internode, the lacimce or valle- cular canals^ which alternate with the * vascular ' bundles, and are there- io6 VASCULAR CRYPTOGAMS fore intermediate between the sheath-teeth ; these canals are of lysi- genous origin — that is, they result from the disappearance of masses of cells. Each bundle also contains a longitudinal air-cavity, or carinal cafial (sometimes called the ' essential air- cavity '). The outline of the stem always shows a number of alternate ridges and furrows ; the ridges correspond to (or are on the same radii as) the ' vascular ' bundles, the furrows to the cortical lacunae. This general description applies equally to the primary vegetative stems, the fertile unbranched stems, and the underground rhizomes ; the branches of the barren stems have no axial cavity or cortical lacunae. In those species where the fer- tile differ in structure from the barren shoots, this appears to result from an arrest of development of the latter. The difference consists essentially in the absence of chloroph3'll, the suppression of branching, and the absence of sto- mates, as well as in the greater develop- ment of the leaf-sheaths. It is possible to induce artificially the fertile shoots of E. arvense (L.) to put out green branches from the lower internodes, chlorophyll being also formed in the main stem. The branches always spring from within the leaf-sheath at its base, each branch in the space between two teeth ; they therefore correspond in number to the ' vascular ' bundles of the stem, and are always arranged in a whorl. The same description applies to the roots. The number of leaf-teeth and bundles is always smaller on the secondary than on the pri- mary axes, and these, as a rule, do not again produce branches. In some species even the primary stem never branches. The whorl in which the branches stand is, however, not a true, but a false whorl — that is, the phyllotaxis originally shows a regular spiral one-third divergence ; but by subsequent unequal growth the insertions Fig. 8i. — E. viaxiinum. ^, portion of stem (natural size). ?', i' , internodes ; h, central cavity ; /, cortical lacunae ; 6", leaf-sheath ; a, a' . a", branches. B, longitudinal section of rhizome ( X 2). K, transverse diaphragm ; h, h, cavities; g, 'vascular' bundle; /, cortical lacunae ; S, leaf-sheath. C, transverse section of rhizome. D, union of ' vascular' bundles of two in- ternodes, /, I ; K, node. {B — D, diagrammatic.) EQUISETACE^ 107 come ultimately to stand on a level. On the rhizomes the ridges and furrows of the outer surface are generally less well marked, and the axial cavity of the internode is sometimes wanting ; but the vallecular and carinal canals are always present, and play an important part in the diffusion of air through the tissue. The aerial stems, both barren and fertile, are usually completely formed in miniature during the preceding year within the underground bud, and their rapid growth after they appear above the soil is mainly due to the great elongation of the internodal cells. The ascending stem and all other aerial parts of the plant are always entirely destitute of hairs ; while the rhizomes and the underground leaf-sheaths are frequently covered with a felt of root- hairs. The firmness and strength of the slender aerial stem are not due, as in ferns, to the ' vascular ' bundles, but mainly to the siliceous epiderm and the firm hypodermal tissue. The epiderm, consisting of a single layer of elongated cells, is provided with stomates in the green, leafy, aerial stem, but not usually in the colourless fertile stem, or in the rhizomes. In most species of Equisetum the stomates lie in one or more longitudinal rows in the furrows of the stem only ; but in E. arvense, according to Miss E. A. Southworth ('American Naturalist,' 1884, p. 1 041), also on the ridges. Stomates also occur en the leaf- sheaths. The stomates either have their orifice on a level with the surface {Equiseta phafieropora) or considerably depressed below it {Equiseta cryptopora) ; in the latter case they frequently do not open directly into the surrounding air, but are situated in the hypodermal tissue, beneath a ' false stomate,' or pore in the epiderm. The stomates (fig. 82) differ from those of other classes of vascular plants in being formed of two pairs instead of a single pair of guard-cells. Strasburger (Beitr. zur Entwickelungsgesch. der Spaltoffnungen, in Pringsheim's Jahrb., vol. v., p. 297) terms the lower pair ' subsidiary cells ' of the true stomate. All the cells of the epiderm, even the guard-cells of the stomates, have their outer walls or cuticle strongly silicified ; and these deposits of silica frequently project above the surface in the form of fine granules, bosses, rosettes, rings, transverse bands, teeth, or spines. On the guard-cells they usually have the form of ridges radiating from the orifice. Beneath the epiderm, except on the deciduous fertile stems, bundles or layers of firm thick-walled cells generally constitute a sclerenchymatous hypoder?nal tissue, which is especially developed in the elevated ridges of the aerial internodes. On the underground stems both epiderm and hypoderm frequently assume a beautiful brown-red colour. In addition to silica, analysis of the ash of Equisetacese (Dieulafaitj ' Compt. Rend.,' vol. c, 1885, p. 284) shows the presence io8 VASCULAR CRYPTOGAMS of a large amount of sulphates, and the total absence of alkaline carbon- ates. A large portion of the parenchymatous fundamental tissue is desti- tute of chlorophyll ; it is only in the vegetative aerial shoots that there is any considerable development of chlorophyllous tissue, and then it is usually situated in the furrows beneath the stomates. The ' vascular ' bundles of Equisetum are collateral, and are much less strongly lignified than those of ferns. They lie in a circle between the medulla and the cortex, between and somewhat within the cortical canals, and necessarily run parallel to one another. As will be seen from the description given above, each bundle is the result of the coalescence of two branches, one of which originates in the leaf-sheath, while the other develops in the Fig. 82. — Stomate of ^. hyeviatel^. (x 390). A, front view ; B, transverse section of stem, showing side view ; C, siliceous residuum after maceration. (After de Barj-.) internode itself, from above downwards. At the angle where the two arms meet, the formation of tracheides begins in each ; the lower end of each bundle unites by two lateral branches with the two next bundles, one on each side, of the next lower internode ; and the bundles are therefore of the description known as ' common.' Their course re- sembles more that of the bundles of most Dicotyledons and Conifers than that of ferns. Each bundle is traversed longitudinally on its axial side by a carinal canal, occupying the place of the first tracheides, which have become absorbed ; right and left of this, in the mature bundle, are reticulate, annular, and scalariform tracheides ; on the outside is the phloem-portion of the bundle, consisting of a few wide EQUISETACEyE 109 sieve-tubes and narrow cambiform cells. In most species {e.g. E. ar- vense) a general bundle-sheath, or plerome-sheath, consisting of a single layer of cells, encloses the entire circle of bundles, as in most Flowering Plants ; while in others (E. limosum, L., and littorale, Kuhlw.) each individual bundle is enclosed in a separate special bundle-sheath, as in ferns. In the colourless fertile shoots they bend out into the pedicels of the peltate scales of the ' fructification,' as they do into the leaf-sheaths. The growth of the stem takes place through the activity of a single large pyramidal apical cell with an inverted triangular base. There is no other group of plants which exhibits such a well-defined single apical cell or exclusively apical growth. Normally the terminal bud never branches, branching taking place solely by lateral buds produced at the nodes. It was formerly thought that the Equisetaceae display the only known example of lateral branching being due to the formation of endogenous buds ; but recent researches have shown (in E. arvense) that these lateral bud^ are not of endogenous origin, but originate from a single superficial cell of the growing point of the stem in the ordinary way. The segments resulting from the first divisions of the apical cell lie in three straight rows, and are arranged in a spiral divergence of one- third. The ?'oots are produced in whorls at the nodes of the underground stem, in direct connection with lateral buds, or, under favourable con- ditions, at the nodes of the aerial stems. They are furnished with a root-cap, increase by the segmentation of a single apical cell, and are penetrated by an axial ' vascular ' bundle surrounded by a large air- cavity formed by the coalescence of intercellular spaces owing to the absorption of intermediate cells. The weak bundle, in which the tracheides are but feebly developed, is concentric, with the xylem in the centre. The secondary or lateral roots, which arise in acropetal succes- sion on the primary root, differ in their origin from those of ferns and other Avascular Cryptogams. In these latter it is the innermost layer of cells belonging to the fundamental cortical tissue immediately surround- ing the axial ' vascular ' bundle that becomes differentiated into the ■ bundle-sheath or endodermal layer, within which lies the pericambium of the bundle itself ; and the lateral roots originate from the innermost layer of the cortex separated by the pericambium from the bundle. In the roots of Equisetaceae the pericambium is wanting, and its place is to a certain extent supplied by the innermost cortical layer, from which the lateral roots spring, and therefore in close contact with the periphery of the axial bundle. The bundle-sheath itself is, in the Equisetacese, formed from the row of cortical cells next to the innermost row, and not from the mnermost row itself, as in other Vascular Cryptogams. no VASCULAR CRYPTOGAMS The sporan^^cs of the Equisetacens are collected into terminal spicate ' fructifications ' of a cone-like or catkin-like character, resembling nothing else among existing Vascular Cryptogams. These are borne at the extremity either of the ordinary green vegetative stems, whether branched (E. palustre, L.) or unbranched (E. hyemale, L.), or of special fertile stems (E. arvense, pratense, Ehrh., maximum. Lam.), which are then always simple, even when the barren stems are branched, and are usually stouter, nearly or quite desti- tute of chlorophyll, and with much larger leaf-sheaths and coarser teeth. As already mentioned, these can be artificially converted into vegetative stems ; and occasionally deciduous fructifications are borne at the extre- mity of the ordinary green branched stems, in species which normally pro- duce special fertile stems (E. arvense). The sporanges are not, like those of typical Filices, trichomic or epidermal in their origin ; their development closely resembles that in the Marat- tiaceae. They are endogenous out- growths of peculiarly metamorphosed leaves, the peltate scales or sporophylls, arranged, like the branches, in whorls. Intermediate between these and the uppermost whorl of ordinary leaf- sheaths there is (in E. maximum) a whorl of barren but more or less modified leaf-sheaths, forming a small annular girdle, the involucre or ati- 7iulus. The whorls of sporangiferous scales, of which a number are formed above this involucre, make their first appearance as similar annular girdles, projecting but slightly from the stem, but gradually forming a hemi- spherical cushion. This cushion finally breaks up into a number of plates, the surface of which is parallel to that of the stem ; and these, by mutual pressure, become polygonal and usually hexagonal ; each plate or disc is attached to the stem by a slender pedicel at right angles both to its surface and to that of the stem. On the inner surface of these Fig. 83. — A, upper part of fertile stem of E. inaxinuc7ii (natural size); b, leaf-sheath; a. annulus ; x, sporophylls and their stalks. B, sporophylls ( x 6) ; sg, spo- ranges. (After Goebel.) EQUISETACEyE m discs are developed the sporanges, from five to ten on each disc, arising at first as small multicellular projections. The archespore is the terminal cell of a hypodermal row on the under side of the sporophvll, the sporogenous tissue resulting from its division. The mantle-cells are formed in the same way as in Ophioglossaces, but are not so sharply defined. The mother-cells of the spores are connected together in groups of fours or eights, and float freely in the fluid which fills the spo- range. The mode of formation of the spores affords an exceedingly good illustration of the production, by free-cell-formation, of new cells within a mother-cell. When division is about to take place, the proto- plasm first becomes perfectly clear, the nucleus disappears, and a number of granules arrange themselves in the form of a disc. The protoplasm then again becomes turbid, with the exception of two clear spots, one on each side of the disc, which are the rudiments of the fresh nuclei. These, however, after a time again disappear, and their place is taken by four smaller nuclei, each of which is surrounded by a number of the granules which formed a portion of the original disc. Round these nuclei the cell-protoplasm begins now to collect into four separate masses, which gradually become globular ; and these are the special mother-cells of the spores after each has become invested with a ver}- delicate coat of cellulose. This process, which has a remarkable analogy to the formation of the pollen in Flowering Plants, especiallv in Coniferge, does not vary in any essential point from that in the other orders of Vascular Cr\'ptogams ; but it has been followed out with the greatest minuteness and success in Equisetum (limosum, L. ). The mature sporange dehisces by a longitudinal fissure on its inner side facing the sporophyll. The mechanism of the bursting is similar to that of the anther of Flowering Plants, and results from the unequal contraction of lignified and of non-lignified portions of the wall, which is furnished with annular or spiral thickenings to its cell-walls. The various coats of the spores are formed while still within the mother-cell. The first formed is the outermost, a non-cuticularised coat capable of swelHng, which becomes gradually detached, and finally splits into two bands, the elaters, which remain attached to the spore only at one point, in the centre of each, where they meet, while the distal ends of each are dilated into a flattened spathulate form. When the spore escapes from the sporange the four elaters are stretched out nearly straight : when moistened they roll up, owing to their unequal lignification, covering up the spore almost entirely, as they did at first before becoming detached. The second coat is more or less cuticularised, and on germination also raises itself in folds from the innermost coat, which is closely applied to the contents of the spore, and is again differentiated into an outer 112 VASCULAR CRYPTOGAMS granular cuticiilariscd exospore^ and an inner endospore, composed of unchanged cellulose. So strong is the hygroscopic property of the elaters, that, even if lightly breathed on, the spores of Equisetum are seen under the microscope to be inactive motion, from constant changes in the humidity of the air. The spores contain chlorophyll, and, in consequence, retain their vitality only for a very few days, and germinate in a few hours after being placed in favourable conditions. In this respect they show a striking contrast to those of ferns. Fig. 84. — Stages in the development of spore of E. liniosuin ( x 8oo). i and t\ outer coat from which the elaters are formed ; 2, 3, inner coats. (After Goebel.) Fig. 85. — Spore with elaters extended (magnified). Fig. 86.—^. Ihunsum T. Rhizome and tubers. The only mode of vegetative propagation known in the Equisetace^ is by the production of tubers on the rhizomes and on the underground portions of the erect stems ; they are peculiarly modified internodes, filled with starch and other food-materials, and may remain dormant for years. The buds, especially those produced at the lower nodes of the erect stem, also have the power of retaining their vitality for a considerable period in a rudimentary condition ; and, Avhen they vegetate, develop into branches of great vigour. Tomaschek (' Oesterr. Bot. Zeitschr.,' 1881, p. 245) induced prothallia of Equisetum to hibernate by growing them EQUISETACE.^ 113 in a warm situation, in which condition they attained a large amount of independence, and propagated freely by budding. The number of known species of Equisetum, commonly known as ' horsetails,' does not exceed 20 or 25 ; they are most numerous in the temperate regions, decreasing in number both towards the pole and the equator, and are very rare in the Southern Hemisphere. The stem is always very slender, and seldom exceeds two or three feet in height, though E. giganteum (L.) reaches 20 to 40 feei in the tropics, with a climbing habit. Most of the species prefer loose sandy or gravelly soil in damp situations ; several grow in marshes or standing water. The erect stems are mostly annual, but in a few species they endure for several years ; while the rhizome is always perennial, and frequently attains great size both in depth and in lateral extension. The species are all remarkably similar in habit, differing chiefly in the presence or absence of special fertile stems, the position of the stomates, and the degree of branching ; but the classification of the species into two dis- tinct groups of ' homophyadic ' and 'heterophyadic ' is not a natural one. Each species is also characterised by a special arrangement of the ' vascular ' bundles, and of the air-cavities as seen in a transverse section of the stem. In external form, but not in internal structure, they call to mind Ephedra among Gymnosperms, and Casuarina among Angio- sperms. The large amount of silex deposited in the epiderm renders several species, especially E. hyemale, useful for scouring purposes, and they are popularly known under the name of 'Dutch rushes.' Literature, Cramer — in Xageli u. Cramer's Pflanzenphys. Unters. , vol. iii., 1S55. Sanio — (Epiderm and Stomates) Linncea, 1857-8, p. 385. Duval-Jouve — Hist. Nat. des Equisetum, 1864. Rees — (Apex of stem) Pringsheim's Jahrb. wiss. Bot., 1867, p. 209. Milde — Monographia Equisetorum, 1867. Pfitzer — (Bundle-sheath) Pringsheim's Jahrb. wiss. Bot., 1 867, p. 297. Famintzin— (Buds) Bull. Acad. Sc. St. Petersburg, vol. ix., 1876. Campbell— (Prothallium) Amer. Natural., 1883, p. 10. Leclerc du Sablon — (Sporange) Bull. Soc. Bot. France, 1884, p. 292; and Ann. Sc. Nat. (Bot.), vol. ii., 1885, p. 5. Goebel— (Fertile shoots) Ber. Deutsch. Bot. Gesell., 18S6, p. 184. Buchtien— (Oophyte) Uhlworm and Haenlein's Biblioth. Bot., Heft 8, 1S87. 114 VASCULAR CRYPTOGAyTS Fossil Vascular Cryptogams. Fossil remains or impressions of plants are found in all the stratified geological formations from the Upper Silurian to the latest. Of the Thallophytes that must certainly have existed in the seas from which the oldest fossiliferous strata were deposited, the traces are, as might be expected, few and doubtful ; and it is certain that many markings that have been claimed under this category do not belong to the vegetable kingdom at all. The remains of Vascular Cryptogams make their first appearance in the Upper Silurian, and are remarkably abundant in the Devonian and Carboniferous formations. During these periods the arborescent vegetation of the globe consisted entirely of Vascular Cr}^ptogams and Gymnosperms, no remains that can be referred with certainty to Angiosperms being known earlier than the Permian forma- tion. The structure and mode of reproduction in Avascular Cryptogams seem to have been remarkably uniform from the earliest times to the present. The remains found in the fossil state belong, of course, ex- clusively to the sporophyte generation; but these indicate not only that nearly every class of Vascular Cryptogams now in existence was represented in the Carboniferous period, but also that none of the primeval forms of vegetable life at present discovered presented charac- ters differing ver\' widely from existing types. Fossil Rhizocarpe.?:. The fossil remains that can be referred, with any degree of cer- tainty, to the Rhizocarpese are very scanty. A few leaves found here and there have been described by their discoverers, under the names Marsilidium(Schenk)and Sphenoglossum (Emm.), as representing genera nearly allied to Marsilea ; and capsules presenting an external resem- blance to the sporocarps of Pilularia and Marsilea have been found in the Eocene. The Salviniace^ are represented with much more certainty in the Miocene, impressions of leaves found in various beds belonging to that series being indistinguishable from those of Salvinia. More doubt attends the identification of fructifications referred to this order. Strasburger and Solms-Laubach think it possible that certain minute echinate bodies found in calcareous nodules in the Carboniferous, described under the names Traquairia(Carruth.), Zygosporites{Will.), and Sporocarpon (Will.), the first of which is regarded by its discoverer as a FOSSIL VASCULAR CRYPTOGAMS II Radiolarian Rhizopod, may be massulae of Azolla. Sir W. Dawson (Bull. Chicago Acad. Sc, 1886, p. 105) refers organs of fructification ob- tained from the Devonian ( = Erian) in Canada and the northern United States — and previously described, under the name Sporangites (Daws.), as sporangia of LycopodiaccEe — to a genus nearly allied to Salvinia, which he calls Protosalvinia ; but, inasmuch as they are borne on Lepidoden- dron scales, this explanation is inadmissible. Sir W. Dawson believes the megaspores of Rhizocarpe^ to be the chief cause of the highly bituminous character of the shales in which these bodies are found. Fossil Selagixellace.e. Remains of arborescent vegetation more or less nearly allied to the typical Selaginellace^ of the present day occur in extraordinary abun- dance in the older fossiliferous strata. Of these the most abundant and best known families are the Lepidodendreas and the Sigillariese. Of the Lepidodexdre.c the stems are known as Lepidodendron, 2ind the fructification occasionallv found in or2:anic connection with the Fig. 87. — A, B, C, portions of surface of stem of different species oi Lepidodendron (natural size) ; D, single cushion (magnified). (After Sclms-Laubach.) branches, as Lepidostrohus. The fructification is distinctly heterosporous ; and although, in a large number of Lepidostrobus cones, microspores only have been detected, this is unquestionably either because the portion con- taining the megaspores has not been preser\-ed, or possibly because the megasporanges and microsporanges may have been distributed in distinct fructifications — a degree of differentiation unknown in any existing form. The remains of a large number of species of Lepidode?idron occur in the coal measures. They were trees, with stems up to ninety feet in height and two feet in diameter, covered with the diamond-shaped scars of fallen leaves. These scars, together with a portion of the leaf-stalk^ remaining behind in the form of a cushion, occupied the whole surface of the stem. Wherever the internal structure has been preser^-ed, a- I 2 ii6 VASCULAR CRYPTOGAMS central 'vascular' cylinder can be detected, consisting of scalariform tracheides. There is distinct evidence of a secondary growth in thick- ness. The branching was always dichotomous. The leaves were very similar to those of Lycopodium, and were penetrated by a single ' vascular ' bundle. The fructifications known as Lepidostrobiis are cone-like structures, not unlike fir-cones in appearance, consisting of densely packed sporo- phylls. On the upper side of each leaf is a single sporange, often of considerable size. The cones themselves vary in size from that of a hazel-nut to one and a half feet in length. It is seldom that the remains are in a sutificiently perfect condition for the structure of the spores to / ; Fig. 88. — A, transverse section of cone oi Lepidostrobiis BrowniiSchlm-p . ; B, longitudinal section (after R. Brown) ; C. diagrammatic longitudinal section of portion of cone of L. orjiatjis Hook. (after Hooker) ; D, upper surface of sporophyll {Le^idophylliijn). (All from Solms-Laubach.) be made out with certainty ; but in several examples both kinds occur. Where one kind only has at present been detected, it is, in most cases, the microspore, the megaspores being probably in the lower part of the fructification, which has not been preserved or examined. In the mega- spores the exospore has three ridges ; there are numerous spores in each sporange. The microspores of L. dabadianus (Schpr.) are connected together in groups of four ; while in L. Brownei (Schpr.) they are in threes. ]More or less nearly allied to Lepidodendron are a number of other arborescent genera, among the more striking of which are Ulodendron (Stbg.), Bothrodendron (L. and H.), and Lepidophloios (Stbg.), all from the coal measures. FOSSIL VASCULAR CRYPTOGAMS 117 B Although the genus Sigillaria is still placed by some writers among Gymnosperms, its true place is undoubtedly near to Lepidodendron in the order Selaginellacese ; the structure of the stem presents no important difference from that of Lepido- dendron, while the fructification known as Sigillariostrobus bears a remarkable resemblance to Lepidostrobus. The remains of various species of Sigil- laria occur in enormous quantities in the coal measures ; and they constituted one of the predominant forms of vegetation of the period. The stems rivalled va height and thickness those of Lepidoden- dron, and were covered, like them, with the scars of fallen leaves in linear series. They were simple or dichotomously branched. The scars are circular, ovate, or hexagonal from mutual compression. In the section known as Leiodermaria the cushions which occur in other forms are wanting, and the scars stand out at a considerable distance from one another on the smooth surface of the stem. The leaves, which are occasionally found still attached to the branches, were narrow, linear, and sedge-like, up to as much as one and a half feet in length, with a projecting midrib. According to Van Tieghem the stem of Sigillaria differs from that of the Lepidodendre^, and indeed from that of all other Vascular Cryptogams, in the leaf-trace bundles being ' diploxy- lous ' — that is, in the central cylinder having an external secondary and centrifugal as well as an internal primary and centripetal xylem. Renault regards the Rhytidolepida, or Sigillariae with stem exhibiting raised cushions as well as scars, as Cryptogamic ; the LeioderinariecE^ or smooth- stemmed Sigillariae, as Gymnospermic ; but this view is not supported by a careful examination of the structure. . . '^kjm c Fig. 89- — A, B, C, portions of surface of stem of different species oi Sigillaria; D, Leioderj7iaria. (After Solms-Laubach. } ii8 VASCULAR CRYPTOGAMS Sigillariostrobus, the fructification of Sigillaria, is extremely rare. It was a cone resembling Lepidostrobus, with the sporanges placed singly on the base of the sporophylls. The sporophylls are broadly lanceolate and apiculate. Only one kind of spore has at present been discovered, the megaspores, but it may be regarded as certain that these were asso- ciated with a second and smaller kind. The fossils known as Stigmaria are the roots of Sigillaria, the two having been not unfrequently found in connection with one another. They occur in the Devonian and Carboniferous formations. Fragments have been found from twenty to thirty feet or more in length (S. ficoides, Brongn.), cylindrical and unbranched, or the branching always dichoto- mous, the two branches running in a nearly parallel direction. The surface is smooth, with numerous shallow saucer-like depressions, the scars of the rootlets, some of which are still very commonly found attached to the primary root. The Stigmarise obviously lengthened Fig. 90. — Stigmaria ficoides Brongn. with rootlets. (After Solms-Laubach.) exclusively by apical growth. Transverse section shows a hollo^y ' vascular ' cylinder, broken by meshes for the passage of the bundles of the rootlets, and consisting of scalariform tracheides wath a central parenchymatous tissue or ' medulla.' In the rootlets the single central bundle consists of a few scalariform tracheides, which leave the cylinder as a triangular bundle, but become circular in the rootlets. Under the term Lycopodites are included a number of fossil forms, the fructification of which is either entirely unknown, or is not in a suf- ficiently well-preserved state for definite determination. Some of the leafy stems ought possibly to be referred to Coniferse ; others, with leaves of one kind only, perhaps belong to Lycopodiaceae ; while others, with leaves of tw^o different kinds, are Selaginellacese. From beds near the bottom of the Carboniferous series there is a species with thick club-shaped terminal fructification, bearing a striking resemblance to Tycopodium Phlegmaria (Lycopodites Stockii, Kidst.). Ftiiophyton FOSSIL VASCULAR CRYPTOGAMS 119 (Daws.), from the Devonian and Carboniferous formations of Scotland and North iVmerica, should also be included here. The only fossils that can be referred with any degree of certainty to the Isoeteae are those comprised in the genus Iso'ctites (Schmp.), from the Miocene, which is scarcely distinguishable from existing Isoetes. More doubt rests on the true place of Solenites (L. and H.), from the Jurassic, which has been referred with equal probability to Gymnosperms. Of fossil Psilotese the remains are few and uncertain. To this family has been referred Fsilophyton (Daws.) ; but the fructification is very Fig. 91, — Bases of stem oi Sigillaria, with Stigviaria roots attached. (After Solms-Laubach. aberrant from the existing Psiloteae, consisting of a pair of pod-like capsules at the end of special branches. Fossil Filices. The remains of ferns — or more commonly the impressions of the leaves — are found in all fossiliferous strata from the Devonian on- wards. Great difficulty is presented in the classification of fossil ferns by the small fragments in which they are usually found, anything like an entire plant, or even a number of fronds attached to an aerial stem I20 VASCULAR CRYPTOGAMS or rhizome, being extremely rare. The great majority of species appear to have been herbaceous ; or at all events the stems of tree-ferns are not of very common occur- rence, even in the coal measures. And although the fructification has frequently been met with, the vast ma- jority of the leaves of which the remains or the impres- sions have been preserved are barren. The only avail- able system of classification of the greater number of fossil ferns is based on the mode of venation, on which character a number of families have been founded by Brongniart ; but it is doubtful whether this has any great value as a natural system of classifica- tion. A form of heterophylly different from anything which occurs among existing ferns is found in a few species from the Carboniferous formation, where, in addition to the normal pinnae of the frond, themselves again pinnate, im- perfect pinnae of much smaller size and simpler structure are intercalated between them. These imperfect pinn^, known as aphlehice, were described as distinct species before their true character was known. Thus Rhacophyllum adnascens (L. and H.) is the aphlebia of Sphenopteris crenata (L. and H.) ; while various so-called species of Cyclopteris are abnormal pinnae springing from the rachis below the normal pinnae of Neuropteris. On the whole, the leaves of ferns belonging to the Carboniferous period bear a striking resemblance to those of our own day ; in many cases they might belong to living genera. The remains of the fructification of fossil ferns that have come down to us lead us to believe that the existing orders of Filices may have been represented in the earlier geological periods ; and none have as yet been Fig. 92. — ApMehia, from the Carboniferous formation. I, Sphenopteris crenctta L. and H. ; 2, 3, Rhaco- ■hhylltun adnascens L. and H. (After Schimper.) FOSSIL VASCULAR CRYPTOGAMS 121 discovered that cannot be referred to some existing type. The preva- lent forms appear to have been the Polypodiacege, HymenophyllaceEe, and Marattiacefe ; this last order having been apparently much more widely distributed and more abundant in the earher periods than it is now. The HYMENOPHYLLACEyE may possibly have been one of the earliest differentiated types. In Palaeopteris hibernica (Schmp.) (Cyclopteris ;. — A, frond of Palceopteris hibernica Schmp. (restored) (-^-6) ; B, pinnule (somewhat mag.) ; ■tile pinna (nat. size) ; D, two cup-shaped indusia attached to the filiform midrib (mag.) ; E, Fig. Q3. sporanges of a hymenophyllaceous fern from the coal measures (mag.). (After Carruthers.) hibernica, Forbes), specimens have been found in which all the lower pinnae are fertile. The pinnule was reduced to a midrib supporting the slender stalks of the bilabiate cup-shaped indusia ; and the stalk is con- tinued into the indusium, to which the sessile sporanges are attached. The texture of the frond was not membranaceous, like that of most exist- ing Hymenophyllaceae, but was more like that of Loxsoma. On the rachis between the pinnae are seated single large decurrent pinnules. I '*2 VASCULAR CRYPTOGAMS The edges of the pinnules are sh'ghtly serrate from the numerous dicho- tomising veins ; the lower part of the stipe is clothed with scales. Spo- ranges with the characteristic oblique annulus of the Hymenophyllacese have also been found in the coal measures by Carruthers ('Geol. Mag.,' Feb. 1872). Remains which can be referred with certainty to the MARATTIACE.E are not unfre- quent. In Scolecopteris (Stur) we have a true synange ; the separate sporanges, arranged on a common elevated re- ceptacle, are linear-ovate with a long free apex, and open by a fissure on the inner side without any trace of an an- nulus. In Asterotheca (Presl) the circular sorus usually con- sists of six exannulate spo- ranges closely adnate to one another, the sori are sessile, and are arranged in a single row on each side of the mid- rib of the pinna. In Renaultia (Stur) a group of cells occurs in the outer wall of the spo- range similar to that in Angi- opteris, w^hich may be the rudiment of an annulus. Seftenbergia (Cord.) presents important differences. The sporanges are not collected into sori, but are scattered along the veins of the third order ; each sporange has at its apex a cap-like annulus. It appears to be a connecting link between the Marattiacese and Schizaeaceee. Other types of Marattiaceae are presented by Danasites (Gopp.) and Botryopteris (Ren.). The remaining types of ferns of the Devonian and Carboniferous, .and especially those of more recent periods, present the greatest resem- FiG. 94. — Fructifications of fossil Marattiaceae. A, Seftenbergia ophidermatica ; B, Haiilea Miltoni ; C, Oligocarpia Lindseeoides ; D, Scolecopteris poly- inorpha ; E, Asterotheca Sternbergii, (After Solms- Laubach.) FOSSIL VASCULAR CRYPTOGAMS I2S blance to Polypodiace^ and Cyatheace.^ among existing forms. No fructification resembling that of Osmundacese has at present been dis- covered ; but Osmiindites (Carruth.), from the Lower Eocene, has been referred to that order by its discoverer from the pecuharities of the structure of the stem. The Ophioglossaceas are still unrepresented in palaeophytology. The internal structure of the stem and leaf-stalk of most fossil ferns, ?^^'^?R^ ^ rS:W.ii^ '.1,---- ;,C^.. ■J >'^--^'>^ v'3''" "^■c^ 'rl '-^' Fig. 95. — Section of Stemniatopteris Cord, invested ^vith rooX.s= Psaronius Cord. (From a specimen in the British Museum.) where this can be determined, differs in no important respect from that of living forms. We find the same interrupted ring of 'vascular' bundles, which may be either concentric or collateral, the xylem con- sisting largely of scalariform tracheides, the same layers of sclerenchyme both in connection with the bundles and beneath the epiderm ; evident indications of gum-passages have even been detected. But though this is by far the most common type of structure, a second is displayed in a few rare examples, in which the arrangement of the ' vascular ' elements 124 VASCULAR CRYPTOGAMS may be compared to that in the stem of Monocotyledons, as the ordinary arrangement may be to that in the first year in the stem of Dicotyledons. In Stemmatopteris (Cord.) (including Psaronius, Cord., and Zippea, Cord.), from the Bath coal-field, the circumference of the stem is com- posed of a continuous envelope of sclerenchymatous tissue, within which are perpendicular tracts of ' vascular ' tissue not penetrated by meshes. Between these tracts the leaves were given off in perpendicular series, the large single leaf-bundles coming right out from the central paren- chyme, in which they existed as well-formed bundles, filling up more or less completely the central cavity (see fig. 95). There is therefore no closed cylinder with central ' medulla ' as in ordinary ferns. By some authors it has been proposed to establish the fern-stems which display this character as a separate group under the name Psaronieae, but there is every reason to identify the stem of Stemmatopteris insignis (Cord.) with the fronds of Pecopteris arborescens (Schl), which bear fructi- fication indistinguishable from that of Cyathea ; and, this character being the more important, the genus must be placed under Cyathe- aceiE. Fossil Equisetace^. Remains of the genus Equisetites, evidently very nearly allied to Equisetum. if not identical with it, are found in greater or less abun- dance in various strata from the Carboniferous to the Tertiary, attaining their maximum development in the Trias. The stems of these fossil horsetails are from one and a half to six inches in diameter, and may have attained a height of from twenty-five to thirty-five feet. They are cylin- drical, and are marked with alternate ridges and furrows. At the nodes are tubular leaf-sheaths split at the margin into numerous short teeth, each of which terminates in an elongated bristle ; in some species the number of these teeth appears to have amounted to as many as one hundred. The nodal diaphragms are clearly seen in E. arenaceus (Brongn.), the remains of which occur in extraordinary abundance in the Upper Trias ; and, in some species at least, the furrows and ridges of each internode are alternate respectively with those of the internodes next above and next below. Remains of rhizomes have been found closely resembling in structure those of Equisetum. Nearly allied to Equise- tites are the genera Schizoneura (Schmp.) and Phyllotheca (Brongn.); the latter differing from the type in its spreading sheath-teeth, and in the ridges and furrows of adjacent internodes not being alternate. The fructification of Equisetites has only been found in a very imperfect con- dition. That of Phyllotheca bears a close resemblance to the cone- FOSSIL VASCULAR CRYPTOGAMS 125 like sporangiferous spikes of Equisetum. It contained spores of one kind only. The group of Calamarie.e — including the stems known as Cala- mites and CaIamode?idron, and the fruit known as CaIa?nostachys — have been separated by some authorities from the Equisetaceae on the ground of their alleged heterospory, but without sufficient warrant from the facts of their structure as actually observed. The remains of Calamites occur in immense quantities in the Car- boniferous strata ; apparently they constituted one of the most im- portant features of the vegetation of that period, disappearing after the Permian. The stems were fre- quently of gigantic dimensions com- pared with our existing Equisetums, attaining a height of thirty feet and a diameter of four inches or more. They consist of a hollow central cavity, with a cylinder of tracheides in wedge-shaped bundles, separated at their origin by parenchyme, and alternating at the nodes, where there is a diaphragm or ' phragma.' The leaves, which spring in whorls from each node, do not, as in Equi- setites, coalesce laterally into sheaths surroundino; the stem. Thev are narrow and acicular, with a single prominent midrib. At the nodes are occasionally seen saucer-shaped depressions, the scars of the lateral branches, which are sometimes found attached to the primary axis. The growth of the stem is characterised by a considerable secondary increase in thickness ; and, since this phenomenon was formerly un- known among living Vascular Cryptogams, it has induced some authori- ties to transfer those examples where it occurs, under the name of Calamodendrese, to Gymnosperms ; but this has been rendered un- necessary from the fact that a secondary growth in thickness occurs also in Lepidodendron and Sigillaria, as well as in Isoetes; and is further contradicted by the fact that fructification of an evidently cr}-ptogamic character has been found in organic connection with stems Fig. 96. — A, Phyllotheca eqtdsetiformis ; B, fructification of Phyllotheca. (After Solms- Laubach.) 126 VASCULAR CRYPTOGAMS which must be referred to the same group. To the same family as Calamites belong probably Astromyelon (Will), and at least some species of Arthropitys (Gopp.). The degree of identity in structure of Calanifldendron with Calamites is a point on which the best authorities are not yet in agreement. To the genus Calamitina (Weiss) (Asterophyllites, Ren., Calamocladus, Schmp.) belong a number of calamite stems found with the leaves still in connection with them. These are of very peculiar form, consisting of an ovatedanceolate basal portion, thickened and marked by a central furrow, and a narrowly-lanceolate acuminate apical portion ; the basal Fig. 97.— Stems of Calamites. (After Weiss.) portion alone being very frequently preserved. The leaves do not coalesce laterally into sheaths ; on falling off they leave behind whorls of round or ovate scars. Bornia (Brongn.) (Archaeocalamites, Stur) is an older fossil occurring in the Devonian formation, differing from the more recent forms in the broad flat longitudinal ribs on the stem not alternating in adjacent internodes. In Annularia (Brongn.), which occurs only in the Carboniferous formation, the leaves are linear-lanceolate, and are penetrated by a single ' vascular ' bundle ; those of each whorl are united laterally in their basal portion into a shallow saucer-shaped cup, through which the stem FOSSIL VASCULAR CRYPTOGAMS 127 passes, and from the margin of which spring the hnear-lanceolate free portions of the leaves. Annularia has been regarded by some writers as an herbaceous aquatic plant ; but there is little doubt that it is the branches and foliage of Calamites. The fructification of the Calamariese, described under the name Calamostachys — with which must be identified Volkmannia (Stbg.) and Fig. 98. — Leaves o{ C alaniiiina. (After Weiss.) tn ft ; IP-^'tSS- \-;.."^ t ^^ ^ 4 IP I ( '\ Fig. 99. — Archcpocalamites radiatus Stur. (After Stur.) Bruckmannia (Stbg.) — has not unfrequently been found in organic con- nection with the stem. Each cylindrical cone-like fructification consists of a number of whorls of sporophylls, but differs from that of Equisetum or of Equisetites in the fertile whorls alternating, in each spike, with barren whorls consisting of a large number of lanceolate acute leaves, free or more or less connate at the base ; the free portions completely covcr the next upper fertile whorl and the base of the barren whorl I2S VASCULAR CRYPTOGAMS above that ; thus giving a remarkable superficial resemblance to a fir- cone. The sporophylls of each whorl are not united with one another ; they resemble those of Equisetum in their peltate form, and each bears on its under side four sporanges. It is very rarely that the spores are preserved in sufficient perfection for their structure to be made out with certainty. The statement that they are of two kinds, megaspores and microspores, rests on insufficient evidence. Carruthers believes that he has detected in a few cases an outer separable membrane which would Fig. ioo. — A, Fructification of Cingjilaria typica; B, portion of a barren and of a fertile whorl C, upper surface of lertile whorl. (After Weiss.) unroll itself in the form of elaters. In Palseostachys (Weiss) the spo- rophylls stand in the axils of the barren leaves. The fructification of Ciiigularia (Weiss) has a very remarkable appearance, from the alternate barren and fertile whorls standing out nearly at right angles to the axis ; the leaves of the barren whorls are connate for about half their length ; the sporophylls are also united in each whorl into a horizontal plate, divided at the margin into truncate lobes ; from the under side of this plate the sporanges hang vertically in radial rows. The remains of Cingularia fructifications are found in large numbers in the coal FOSSIL VASCULAR CRYPTOGAMS 129 measures. Very little is known of their stem, which appears, however, to have resembled that of the Calamariese. More doubt rests on the affinity with the Equisetaceae of the group of Sphexophylle.e. The remains of Sphenophylluin (Brongn.) are found in abundance in the Carboniferous formation, but do not come down to more recent times than the Lower Permian. The stem is divided into distinct nodes and inter- nodes, the latter usually marked with conspicuous ridges and furrows, which are not alternate in adja- cent internodes, but pass continuously throuu;h the nodes. At the swollen nodes are whorls of leaves, with occasional axillary branches. Each whorl ap- pears to consist always of six leaves or of some mul- tiple of six. They are ses- sile, and obcuneate from a narrow base, sometimes denticulate and bifid at the apex, but are not in any Each leaf contains a number of simple or dichotomous 'vascular' bundles. In the centre of the stem is a triangular bundle com- posed of scalariform tra- cheides, to which some authorities add spiral tra- cheides and others with bordered pits ; the bundle passes through the node without material change. This is often surrounded by some layers of secondary wood ; the greater part of the stem, on transverse section, is occupied by a small-celled parenchyme. The fructification of Sphenophyllum consists of cylindrical cone- like spikes resembling those of Calamites. It is composed of whorls degree connate Fig. ioi. — i, 2, Fructification and branch of Asterophyl- lites; 3, 4, fructification and branch oi Anmdaria; 5, 6, fructification and branch of Sphenophyllum. (After Carruthers.) 130 VASCULAR CRYPTOGAMS of sporophylls without any intermediate barren whorls ; the separate leaves are often saccate, the narrow^ apices ascending and covering in an imbricate fashion the bases of the next upper whorl. The position of the sporanges differs materially from that of the other Equisetaceae. They are comparatively large bodies, lenticular, from i to 2*5 mm. in diameter, solitary and sessile in the saccate hollow on the upper surface of the base of the sporophyll. The solid remains have not yet been found in a sufficiently perfect condition for the structure of the spores to be determined with any degree of certainty, but no sufficient evidence of heterospory has been presented. From the form and position of the sporanges the Sphenophyllese are placed by some writers under Selaginellaceae ; but in the general appear- ance and structure of the vegetative organs they approach so nearly to the Calamariese that it seems best at present to place them here until we are better acquainted with the details of the fructification. Stur has recently described and figured specimens with leaves of Asterophyllites at the base, Sphenophyllum-leaves higher up, and terminating in a fructi- fication. Literature of Fossil Vascular Cryptogams. Sternberg — Flora der Vorwelt, 1821-1838. Brongniart— Hist, des Vegetaux Fossiles, 1820-1840; (Sigillaria, Stigmaria, and Lepidodendron) Arch. Mus. d'Hist. Nat., 1839. Lindley and Hutton — Fossil Flora of Great Britain, 1833-1837. Witham — Internal Structure of Fossil Vegetables, 1833. Goppert— Systema Filicum Fossilium, 1826 ; Gattungen der fossilen Pflanzen, 1841. Unger — Genera et Species Plantarum Fossilium, 1840. Corda — Beitr. zur Flora der Vorwelt, 1845. Hooker^ Vegetation of Carboniferous Period, in Mem. Geol. Survey, 1847. Brown — Triptosporites, in Linn. Soc. Trans., 1 85 1. Geinitz — Steinkohlenformation in Sachsen, 1855. Ludwig — Calamiten-Friichte Palaeontographia, 186 1. Goldenberg — Flora Saraepontana, 1862. Binney — Fossil Carboniferous Plants, Palceont. Soc, 1 868-1 875. Schimper — Paleontologie vegetale, 1 869- 1 874. Weiss — Fossile Flora der Steinkohlenformation, &c., 1869 ; Beitr. zur fossilen Flora, T876-1884. Carruthers — (Ulodendron and Bothrodendron) Monthly Micr, Journ., 1870; (Lycopo- diaceae) 1869; (Calamites) Seemann's Journ. Bot., 1867. Dawson— Fossil Plants of Upper Silurian and Devonian of Canada, 1871-18S2 ; Geological Hist, of Plants, 1888. De Saporta — Paleontologie Francaise, 1873. Grand'Eury— Flora Carbonifere du Dpt. de la Loire, &c., 1877. FOSSIL VASCULAR CRYPTOGAMS 131 Renault — Cours de Bot. fossile, vols, i.-iii., 1881-1883. Williamson— Organisation of Plants of the Coal Measures, Phil. Trans. 1871-1888 ; (Stigmaria) PalKont. Soc, 1887. Kidston — (Lepidodendron, Sigillaria, &c.) Ann. and Mag. Nat. Hist., 1885. Lesquereux — Coal Flora of Carboniferous Formation of Pennsylvania, &c., 1884. Stur — Carbonflora der Schatzlarenschichter, 1885 ; Culmflora, 1877-1883. Van Tieghem— Bull. Soc. Bot. France, 1883, p. 169. Zeiller — Ann. Sc. Nat. (Bot.), 1884; (Sigillaria) do., 1884, p. 256. Zittel — Handbuch der Palceontologie, 1879-1885. Solms-Laubach — Einleitung in die Palaeophytologie, 1887 (for which see very copious bibliography). Schenk — Die fossilen Pflanzenreste, in Schenk's Handb. der Botanik, vol. iv. , 1888. K 2 132 MUSCINE^ SECOND SUBDIVISION. MUSCINEyE. The line of demarcation between the Vascular Cryptogams and the plants immediately below them in the scale of organisation, the Muscinese, is a very sharp one, and their genetic relationship to one another presents considerable difficulties. The lower type of structure is, however, chiefly manifested in the vegetative organs. The mode of sexual reproduction which occurs throughout this group corresponds in its most important features with that in Vascular Cryptogams ; and we have here also a division of the life-history of the plants into a sporo- phyte and an oophyte generation, a true alternation of generations, although the phenomenon differs in one important point from that which we have seen in Vascular Cryptogams, viz. in almost the whole of the vegetative system belonging to the oophyte instead of to the sporophyte generation. To this we have already seen an approach in Gymnogramme (p. 65). The vegetative system is invariably of small size, and almost entirely destitute of vascular bundles and of all other strengthening tissues. Within the group the boundary line is crossed between Cormo- phytes and Thallophytes ; and in the lower orders we entirely lose the differentiation of the vegetative organs into cauline and appendicular organs — in other words, into stem and leaves ; the entire vegetative system consisting of an undifferentiated thallus. The mature plant is almost invariably terrestrial in habit, and is attached to the substratum by rhizoids. The appendicular organs, when present, are minute leaves, which never contain true vascular bundles, and usually consist cf only a single layer of cells. We find, however, the first stage towards the epidermal and fibrovascular structures characteristic of the leaves of vascular plants, in a distinct midrib and edging of elongated cells with somewhat thicker cell-walls overlappmg one another at the extremities, and partially or altogether destitute of chlorophyll. In one group (Sphagnaceae) the leaves are composed of cells of two different kinds, small cells containing chlorophyll interspersed among much larger empty cells. The leaves, being usually unilamellar, cannot, of course, be pro- MUSCIXE.^ 133 vided with stomates, though these are frequently present on the organs of propagation ; while one group of thalloid forms (Marchantiaceae) possess stomates of remarkable and complicated structure. The vegeta- tive propagation of the ^luscinece takes place in several ways : ist, by inficvation, i.e. by a process of renewal at the apex, while the oldest parts die off behind ; 2nd, by means of gemmae, stolons, or detached buds ; and 3rd, by the non-sexual production of a thallus or protoneme, a process which will be described presently. The facility of these various modes of vegetative multiplication gives rise to the tufted or caespitose habit of many species. Notwithstanding the variety in the development of the vegetative structure, the sexual organs of ^^luscinece are remarkably uniform in their main features. The male and female organs are termed respec- tively, as in Vascular Cryptogams, antherids and archegoiies. The mature antherid is a spherical, ellipsoidal, or club-shaped body, with a longer or shorter stalk, the outer layer of its cells forming an enclosing wall, while each of the small and numerous crowded cells in the interior develops an antherozoid. These bodies are spirally-coiled threads of protoplasm, thicker at the posterior end, and tapering to a fine point at the anterior end, where they are furnished with two long fine cilia, the vibrations of which set them in constant motion ; they are set free by the rupture of the wall of the antherid at its apex. The archegones, when in a condition capable of impregnation, are flask-shaped bodies bulging from a narrow base, and produced above into a long ?ieck. The swollen or ventral portion, the venter., encloses one cell much larger than the rest, the central cell^ from the larger and lower portion of which is developed, after its separation by a horizontal septum, the germ-cell or oosphere. Above this central cell is an axial row of cells termed the canal-cells^ passing through the narrow portion or neck of the archegone, and continued as far as the apical cells, stigmatic cells, or lid-cells, which form what is called the stigma. These canal-cells are transformed before impregnation into mucilage, which finally swells up and forces apart the four stigmatic cells, an open canal being thus formed, through which the antherozoids reach the oosphere. Notwith- standing the general uniformity in structure of the sexual organs of the Muscineae, their origin varies greatly. They may originate, in the thalloid forms, below the growing apex, from the superficial cells of the thallus, or on special metamorphosed branches ; in the foliose forms both antherids and archegones may be formed from the apical cell of the shoot, or from segments of it ; and in this case they may take the place of leaves, of lateral shoots, or even of hairs. According to Leitgeb, the order of evolution from the lower to the higher forms of 134 MUSCINE^E Muscineae is indicated by the position of the sexual organs on the vegetative shoots ; as these organs approach nearer and nearer to the apex, the shoot gradually loses its vegetative character, and becomes differentiated into a special fertile branch. The sexual organs are frequently surrounded by crowded and slightly modified foliar structures, the whole arrangement having then some resemblance to the flower of Phanerogams. Thus, in the thalloid forms, the antherids and archegones are commonly borne on umbrella- shaped outgrowths of the thallus which are not inaptly termed respec- tively male and female inflorescences. In the foliose forms they are frequently arranged at the extremities or laterally on branches, and closely surrounded by small leaves constituting the perichcefe or perianth, reminding one of the bracts, or even of the calyx, of Flowering Plants, the whole structure forming an hermaphrodite, monoecious, or dioecious ' flower.' They are often accompanied by barren, hair-like cells, termed paraphyses. The first result of the impregnation of the oosphere by an anthero- zoid is the formation of an ovoid e7nhryo by repeated cell-divisions ; this continues to grow at its apex, and finally develops into the fructification here known distinctively as the sporogone, the ultimate form of which varies greatly in the different fiimilies. In its most perfect form the sporogone is differentiated externally into a slender stalk or sefa, which penetrates into the base of the archegone, or even into the underlying tissue, and a spore-capsule, called indifferently the sporange, theca, or 7irn. Along with the spores the spore-capsule some- times contains (in the Hepaticse) elongated cells thickened by a single or double spiral band known as elaters, which assist in the dissemination of the spores. The mature sporange is, in the highest forms, sur- mounted by a cap or calypte?', which becomes completely detached at its base, while the mature lower portion of the archegone encloses the base of the seta in the form of a sheath or vagitie ; in the lower forms the spore-capsule always remains enclosed in the calypter. The spores of the Muscineae are always formed in fours within the spore-7nother- cells, which latter are produced within the cavity of the sporange by free cell-formation, from a special layer or layers of cells known as the archespore. When ripe they have a double cell-wall, the outermost layer or exospore being provided with small excrescences, and the inner layer or endospore bursting through it on germination. The contents consist of protoplasm, chlorophyll-grains, starch, and oil. The thalloid or leafy plant (as the case may be) does not, as a rule, arise immediately from the germinating spore, but, in all the higher forms, only after the previous formation of a colourless confervoid or MUSCINE^E 1.35 filamentous structure, the prothallus or protoneme, on which the leafy plant containing chlorophyll arises as a lateral shoot. The MuscinecC present, therefore, an illustration of the phenomenon of alternation of generations ; the sexual generation which intervenes between germina- tion and impregnation, or oophyte, consisting of the protoneme (when present), the leafy (or thalloid) plant, together with the sexual organs ; the non-sexual generation intervening between impregnation and ger- mination, or sporophyte, consisting of the sporogone only with its spores. The Muscine^ are divided into two well-marked families, the Musci or Mosses, and Hepaticce or Liverworts. In the ^vlusci the immediate result of the germination of the spore is always a protoneme consisting of branched rows of green or colourless cells, and often growing for a considerable time independently, even after it has produced leafy stems by lateral budding. The vegetative structure is always cormophytic, and consists of a filiform stem furnished with two, three, or four rows of leaves, not exhibiting any distinct bilateral structure, and branching monopodially, never dichotomously. The sporogone is only for a time enclosed in the calypter, which is usually eventually ruptured below, the lower portion developing into the vagine^ while the upper part is elevated above the apex of the sporogone in the form of a cap. The spore- mother-cells are produced from one or more special layers of tissue within the sporange, the archespore, while the axial mass develops into a solid cohimel. The uppermost portion of the wall of the sporange forms a lid or operacle, which usually becomes detached from the lower portion, to which the term theca or sporange specially belongs, to allow the escape of the spores. The outermost layer of cells of the wall of the sporange is more or less completely differentiated into an epiderm, which is frequently penetrated by stomates. When the opercule is removed, the rim of the sporange is either quite smooth, when it is termed gymtiostomous, or the edge is furnished with delicate hair-like appendages, constituting the peristome, arranged in a single row or fre- quently in two, when they are called respectively teeth and citia, the former constituting the outer, the latter the inner row. The number of both teeth and cilia is always a multiple of four, or more correctly speak- ing, a ' power ' of two. In the Hepaticae the protoneme is either scantily developed or is altogether suppressed. The rest of the sexual generation consists either of a flat dichotomously branched thallus or thalloid stem, or of a slender stalk furnished with two or three rows of leaves. In the division into Foliose and Thalloid or Frondose forms, the Hepatic^e therefore present the transition from Cormophytes to Thallophytes. The mode of growth is always distinctly bilateral ; the thalloid forms cling 136 MUSCINE.E closely to the ground or to some other substratum ; and even in the foliose forms there is a well-marked tendency to the differentiation of an upper or dorsal and an under or ventral surface. The non-sexual generation or sporogone remains surrounded by the calypter until the spores are ripe ; the calypter is usually at length ruptured at the apex, and remains at the base of the sporogone as an open sheath, while the sporange projects above its apex to allow the escape of the spores. The mother-cells of the spores are either developed from the whole of the archespore, or, in most families, some of the cells develop into elaters ; there is no columel. Literature. Hofmeister — On the Germination, Development, and Fructification of the Higher Cryptogamia, Ray. Soc, 1862. Leclerc du Sablon., Ann. So. Xat., 18S5, p. 126; and Bull. Soc, Bot. FrancCj 1885, pp. 30 and 187. Goebel — Die Muscineen, in Schenk's Handbuch der Botanik, vol. ii., 1882. Class VII.— Musci. The germinating spore of Mosses gives rise to a prothallium which is always in the typical families of a filamentous conferva-like character, and is hence known as the protoneme. On this is produced the leafy plant with differentiated stem and leaves by lateral budding. These together, therefore, constitute the sexual generation or oophyte, which terminates in the production of the sexual organs. From the fertilised oosphere proceeds the sporogone^ which comprises in itself the non-sexual generation or sporophyte. The protoneme first originates, in typical mosses (Bryacese), as a tubular bulging of the endospore or inner coat of the spore, divisions taking place in it in the transverse direction only. It has an unlimited power of apical growth, and often branches copiously, forming a dense felt of considerable size above or below the surface of the soil, in the former case densely filled with chlorophyll. The protoneme usually disappears altogether after the appearance on it of the leafy plant ; but in some cases, especially in the Phascaceae, it remains vigorous even after the formation of the sporogone. In the Sphagnaceae the proto- neme consists of a flat plate of cells ; while in the Andreseaceae cell- divisiori begins to take place within the spore, the resulting prothallium consisting of a small cellular tissue. The buds which develop into the ^JUSCI f37 leafy stems appear never or very seldom to arise at the apex of a primary filament of the protoneme, but always as lateral branches. Mosses display a certain amount of differentiation of tissues. The apical cell of the stem is, except in Fissidens (Hedw.), a three-sided Fig. I02. — Catharinea {^Atrichuvi) 7indttlata W. and M. (magnified). (After Schimper.) pyramid. The primary meristem of the stem, "situated beneath the growing point, which develops into the permanent tissue, usually becomes differentiated into an inner and a peripheral mass ; the latter, although 138 MUSCINE/E not strongly defined, partaking of an epidermal character \ the bright red or yellow cell-walls are considerably thicker than those of the central thin- walled large-celled fundamental tissue. In some genera a further differen- tiation takes place of the axial portion of the central cylinder into a rudimentary ' vascular ' bundle with thicker cell-walls ; similar rudimen- tary bundles being also formed in the pedicel of the sporogone. Both the partially lignified and the thin-walled cells have simple pits in their cell-walls ; these are found in all families of mosses, and are especially abundant in the midrib of the leaves. Some species of Sphagnum (L.) have rudimentary sieve-plates. The central bundle in the stem of Mnium, Polytrichum (L.), and other genera, has been shown by Haberlandt not to possess any of the strengthening functions of a true vascular bundle, but Fig. 103. — A, germinating spore of Funaria hygrometrica L. (x 550) ; J, exospore ; tu, rhizoid ; v, vacuole. B, portion of protoneme (x 90); K, rudiment ot leafy axis ; w, rhizoid. (After Goebel.) to be constructed for the purpose of the conduction of water. Its cells con- tain nothing but a watery fluid, without starch-grains, oil, or protoplasm. In genera which have no such central bundle, like Dicranum (Hedw.) and Leucobryum (Hpe.), the epidermal tissue of the stem and branches, with its perforated cells, forms a similar capillary apparatus. In the more highly developed mosses, Haberlandt notes the following dis- tinct tissues : — (i) an epidermal tissue, sometimes developing trichomic structures; (2) a mechanical system, consisting of elongated cells with thickened walls ; (3) an absorbing system, most strongly displayed in the rhizoids— also at the base of the sporange ; (4) an assimilating system, often composed of palisade-cells, in the leaves or in the sporange; (5) a conducting system, consisting of the rudimentary ' vascular ' bundles; MUSCI 139 ^. yi u ""J (6) a reserve-system, usually represented by the aquiferous tissue; (7) a secreting system, developed typically in the sporange. No special secretory or excretory organs have been detected in mosses. The leaves of mosses originate as broad papillose bulgings of a cell of the stem which becomes cut off by a septum. They are always of small size, sessile, and vary in shape from extremely narrow to broadly lanceolate or almost orbicular. The tissue of the greater part of the leaf usually consists of only a single layer of cells, all of which contain chlorophyll, except in the Sphagnaceae and in Leucobryum, where the cells are of two different kinds, one large and empty, the other very small and chlorophyllous, thus giving the leaf a very light yellow-green colour. In most mosses the marginal cells of the leaf, and a row extending through the middle of the leaf from the base to the apex, are much smaller, and are disposed in several layers, though still thin-walled, thus consti- tuting the rudiments of an epiderm and midrib. The midrib may even extend beyond the apex of the leaf as an awn or bristle. The leaves are usually crowded, especially in the neighbourhood of the sexual reproductive organs. Their phyllotaxis is spiral, or more rarely distichous. The branch- ing of the stem of mosses is apparently neither dichotomous nor axillary ; the number of lateral shoots is always much smaller than that of the leaves. When the primary shoot produces a so-called ' flower ' at its apex, a lateral shoot situated beneath it not unfrequently displays a more vigorous growth of a monopodial character, and is then termed an innovation, Prolification, or the prolongation of a shoot by the continued growth of the bud within and above the male ' flower,' is a common phenomenon in Polytrichum. Nearly leafless shoots or stolons are sometimes formed beneath or on the surface of the ground, arising finally as erect leafy stems. In most mosses large numbers of rhizoids are formed on the under side of the stem, often clothing it completely with a reddish brown felt (see fig. 102). They differ from the protoneme in their tendency to grow downwards, and in not usually containing chlorophyll ; but there is no sharp distinction between the two, each possessing the power of pro- ducing branches indistinguishable from those of the other. w Fig. 104. — Polytrichu7n coinviune L. ; pro- liferous male plant (slightly magnified). I40 Mi'SCINE.E The non-sexual propagation of mosses takes place in a variety of ^vays, the first step being, in nearly all cases, the production of a colour- less filament of the nature of a protoneme. This protonemal branch, like the true protoneme which springs from a spore, may produce by lateral budding a number of leafy shoots. Protonemal branches of this kind are in some genera (such as Mnium, L., Barbula, Hedw., and Phascum, L.) produced in large num- bers simply by turning over a tuft of moss on the soil. In this state they frequently hibernate, the portion above the soil disappearing entirely. In some mosses the leaves produce a protoneme simply by the growth of particular cells into segmented fila- ments ; and this may even take place with detached leaves if kept moist. The seta or stalk of the sporogone has a special tendency to produce protonemes when in contact with damp soil. Rhizoids also may give rise to gemmse or leaf-buds, whether above or beneath the surface of the soil. Gemmce of a more complicated structure occur in a few species, as Aulacom- nion androgynum (Schw.) (Bower, 'Journ. Linn. Soc.,' 1884, XX., p. 465), and Tetra- phis pellucida (Hedw.), being stalked fusiform or lenticular multicellular bodies. In the latter species they are enveloped in an elegant cup or cupule, composed of a number of leaves, out of which they eventually fall, and then put forth protonemal filaments, which give rise first to a flat prothallus resembling that of a fern, and then to a leaf-bud. Gemmae are produced in a variety of situations, as at the apex of a leaf and on the rhizoids. The sexual organs of mosses are very commonly enveloped in closely crowded leaves which have undergone a certain amount of modification, Fig. to^.—A, young plant of Barbula, in ; h, rhizoid, producing protonemes /, and underground gemma k ( X 20). B, the same gemma ( x 300). (After Goebel.) MUSCI 141 and the entire structure is sometimes — from analogy with the corre- sponding structure in Flowering Plants — called the flower. Such a flower may either be hermaphrodite, including both antherids and archegones, or unisexual, and the species may then be monoecious or dioecious. The female and the hermaphrodite flowers are not dissimilar in appearance, while that of the male flowers is altogether different. Fig. 106. — Funaria hygromettica; longitudinal section through male inflorescence; a, young an- therid ; b, nearly mature antherid ; c, paraphyses ; d, e, perigonal leaves ( x 300). (After Goebel.) In the hermaphrodite flowers the archegones usually occupy the central position, corresponding to the pistil in Flowering Plants, the antherids being arranged in an encircling spiral; while the whole is enveloped in a rosette of small leaves termed iht perichcste or perianth. The entire structure resembles externally arrelongated closed bud. Only a single archegone in each flower is usually fertilised or arrives at maturity. The female resemble the hermaphrodite flowers in every respect except 142 B A Fig. 107. — Polytrichujii co7n7nitne. A. B, mature plants with sporo- gone ; C, male plant (nat. size). MUSCLXE.E that the antherids are suppressed. The male flowers present much greater variety in form and appearance ; the male perianth or peri- gone is usually composed of broader, shorter, and thicker leaves, which sometimes sheath at the base, and are not unfrequently red. The flowers themselves are ovoid, globular, or discoid ; the antherids usually stand in the axils of metamorphosed leaves. Both male and female flowers are provided with barren segmented filaments or paraphyses. In the male flowers the paraphyses are fili- form, club-shaped, or spathulate, and termi- nate in several rows of cells ; in the female flowers they are simple filiform bodies com- posed of a single row of cells. Their function appears to be to keep the archegones moist until they have been fertilised by the anthe- rozoids. The first antherid appears to be a terminal structure, being developed out of the apical cell of a branch. An hermaphrodite flower is probably derived from two independent shoots, the female shoot being formed im- mediately beneath the male organs. The mature antherid is a stalked club-shaped, or less often spherical sac, with a wall com- posed of only a single layer of cells. In the Sphagnacefe it opens by longitudinal de- hiscence ; in the other orders by an apical slit through which the antherozoids, still enclosed in their mother-cells, are discharged as a thick mucilaginous mass, being imbedded in a jelly which is expelled in jets when the an- therid bursts, but which is soluble in water. The antherozoids then escape from their mother-cell walls, and swim about as filiform bodies, furnished at the anterior end with two slender vibratile cilia, and containing a number of starchy granules. The male in- florescence of Polytrichum exhibits a re- markable tendency to prolification (see fig. MUSCI 143 104). The archegone has somewhat the form of a very long-necked flask. The wall of the venter or ventral portion, which is ovoid and supported on a short stalk, consists of two layers of cells, while the elongated neck, which is often somewhat twisted, is composed of from four to six rows in a single layer. The interior of the venter consists of a single large cell, the central cell, which divides into two by a horizontal septum ; the lower segment contains the oosphere, and the upper segment becomes the ventral canal-cell, while the neck is penetrated by a single axial row of ■ ^ -i:. J Fig. 108. — A, anther'id of^ Fiinaria hygroinetrica, discharging anthe- rozoids, « (x 350). B, anthero- zoid of Polytrichnm ; b, still enclosed in mother-cell ; c, free (x 800). Fig. 109. — Ftinaria hygrometrica. A. longitudinal section through female inflorescence ; a, arche- gones ; b, perichaetial leaves (x 100). B^ arche- gone ( X 500) ; b, venter and central cell ; h, neck ; VI, opening of canal. C, openmg of neck (more highly magnifiedX with stigmatic cells forced open. cells which deliquesce into mucilage before impregnation. An open canal is thus left, through which the antherozoids penetrate to the oosphere ; the terminal stigmatic or lid-cells of each row of the neck, constituting together the stigma, being forced apart by the exudation of the mucilage. The first archegones are formed from apical cells of shoots. 144 MUSCINEAL The impregnated oosphere, or oosperjji^ develops into an embryo, from which is derived the sporogone within the ventral portion of the archegone. After investing itself with a cell-wall, it divides by a number of longitudinal, radial, and transverse septa. At an early period in typical mosses the young elongated sporogone ruptures transversely the wall of the venter, the lower part of which forms a sheathing protection to its base, and is termed the vagine, while the upper part becomes elevated in the form of a cap or calypter. In the Sphagnace^ the sporo- gone attains almost perfect development before the rupture of the archegone ; in other mosses the various portions of which the sporange is composed are diffe- rentiated only at a later date. The sporange is at first filled with fluid contents, the greater part of which is the archespore. •v iy w jj 1 - v^ »- T-\ K Fig. iio. — Funaria hygrometrica. A, young plant with young sporogone. B, mature plant with mature sporogone ; s, seta ; y, sporange ; c, cah-pter (natural size). C, longitudinal section of sporange (greatly magnified) ; d. opercule ; a, annulus ; />, peristome ; c, columel ; s, arche- spore ; /i, air-cavities. (After Goebel.) Fig. III.— Mouth of sporange of Fonfi- nalis antepyretica L., with peristome ; ap, teeth; ip, cilia (x 50). (After Schimper.) developing into the mother-cells of the spores, from each of which are produced four spores by free-cell formation after preliminary indica- tion of bipartition. The withered neck of the archegone, which has assumed a deep reddish brown colour, may often be recognised for some time surmounting the apex of the calypter. The mature sporogone consists of a pedicel or seta — which is usually of considerable length, the lower portion ox foot being enclosed within the vagine, but is short in Sphagnum and some other genera — and the sporange or spore-capsule surmounted by the calypter, while the base of the seta is surrounded by the sheath-like vagine. The wall of the sporange is composed of several layers of cells, the outermost of which has a distinctly epidermal cha- racter, and is sometimes perforated by stomates with imperfect guard-cells. MUSCI 145 While the greater part of the internal tissue is used up in the formation of the spores, the axial portion always remains unchanged in the form of a solid columel. There are no elaters. Leitgeb regards the sporogone of all mosses (including Sphagnaceae) as consisting, in its earliest stage of development, of an inner mass of cells, the endothecium, distinctly separated from the peripheral mass, or auiphifhecium. In Sphagnaceae the archespore is formed from the latter, in the other orders from the former portion. Among the typical mosses he again distinguishes three types, viz. ; — (i) The Archidnifn-iyT^e : the spore-forming and sterile cells are intermingled in the endothecium ; the spore-sac is separated from the wall of the capsule by a bell-shaped cavity ; (2) the Andreaa-i\^& : the endothecium is differentiated into the archespore and the columel, which does not penetrate the former ; the innermost layer of the amphithecium becomes the spore-sac, which is not separated from the wall of the capsule by any cavity ; (3) the Bryum-tyY>Q : the endothecium is differ- entiated as in the last case, but the columel penetrates the spore-sac, which is separated from the wall of the capsule by a cylindrical cavity. In all true mosses the sporogone is developed by means of a two-edged apical cell. The ripe spores are roundish or cubical, with a thin, finely granulated yellowish, brownish, or purple cuticularised exospore, and an endospore of cellulose, and contain protoplasm, chlorophyll, and oil. The number cf spores in a capsule varies from sixteen (Archidium, Brid.) to an immense quantity, and their size also varies inversely. Several cases of hybridism have been recorded in mosses. Mosses are found in all climates, from the coldest to the hottest ; they are most abundant in temperate regions and in damp situations, clothing old walls, the trunks of trees, &c. A few grow in stagiiant, and one genus (Fontinalis, L.) in running water. Some species a;-e sapro- phytes. They are of scarcely any economical value, but are of great importance in nature in the formation of soil. Literature. Bruch & Schimper — Bryologia Europjea, 1S36-1865. Schimper — Recherches anatom. et physiol. sur les Mousses, 1848. Wilson— Bryologia Britannica, 1855. Hofmeister — Pringsheim's Jahrb. wiss. Bot., 1863, p. 259. Unger — Sitzber. Akad. Wiss. Wien, xliii. , 1861, p. 497, Lorentz — Moosstudien, 1864; Pringsheim's Jahrb. wiss. Bot., 1867, p. 363; Flora, 1867. Berkeley — Handbook of British Mosses, 1863. Leitgeb — Sitzber. Akad. Wiss. Wien, 1 868, 1869. Nageli — Pflanzenphys, Untersuch., Heft i. p. 75. Janczewski — (Archegonium) Bot. Zeit., 1S72, pp. 377 et seq. Stahl— Bot. Zeit., 1876, p. 689. Kienitz-GerlofF— (Sporange) Bot. Zeit., 1S78, pp. 33 and 49. L 146 MUSCINE^ Braithwaite— The British Moss-Flora, 1880-1887. L'Abbe Hy— Bull. Soc. Bot. France, 1880, p. 106 ; Ann. Sc. Nat., xviii., 188 )., p. 105. Goebel — Flora, 1882, p. 323. Firtsch— Ber. Deutsch. Bot. Gesell., 1883, p. 83. Satter— Ber. Deutsch. Bot. Gesell., 1 884, p. 13. Haberlandt — Ber. Deutsch. Bot. Gesell., 1883, p. 263 ; and Pring=heim's Jahrb. wiss. Bot., 18S6, p. 359. Magdeburg — Die Laubmooskapsel als Assimilations-Organ, 1886. Vaizey— (Sporogone) Ann. of Bot., i., 1887, p. 73. Limpricht — Die Laubmoose, in Rabenhorst's Crypt. -Flora Deutschland, 1885-1888. The Musci are classified under four orders, as follows. The Sphag- naceae exhibit much more important peculiarities than the other three orders, and are ranked by some writers of authority as a distinct class. Order i. — Bryace^. This order includes the vast majority of the genera of mosses, and all the more familiar forms except the bog-mosses. The sporanges or * fruits ' form objects of great beauty in the autumn and winter, their usual period of maturit}', fertilisation taking place in the spring or early summer. In some species the sporogone requires more than a year for its full development. The sporogone consists of a sporange which is always surmounted by a calypter, easily removed by the wind ; beneath this is the opercule, which becomes detached, either alone or together with the anmilus, a circular layer of hygrometric epidermal cells bet^veen the opercule and the edge of the capsule ; the whole elevated on a longer or shorter stalk or sefa, which is inserted at its lower end in the vagine. The portion of the seta concealed in the vagine is known as the 7^(9/, and acts as a kind of root, all the food-material needed for the development of the sporogone being absorbed through it. The central strand of tissue in the seta of the Polytrichacese consists, according to Vaizey, of two portions — a leptophloem or rudimentary phloem, in which the storing up and conduction of the food-material takes place ; and a leptoxyleni or rudimentar}^ xylem, which serves for the conduction of the transpiration-current to the lower portion of the sporange furnished with stomates. In the Polytrichacese, in addition to the opercule, a horizontal layer of cells termed the epiphragtn remains attached to the points of the teeth of which the peristome is composed, and covers the mouth of the sporange after the removal of the opercule. The sporange is penetrated by a complete axial columel. The spores are formed by free-cell formation in fours within spore-mother-cells^ themselves derived from a single primordial layer, the archespore ; the walls of the spore- mother-cells finally deliquesce, leaving the spores floating in a fluid MUSCI 147 which for a time fills the spore-sac^ composed of two or three layers of barren cells immediately enclosing the mass of spores. Between the spore-sac and the wall of the mature sporange is an annular air-cavity, tra- versed horizontally by rows of chloro- phyllous cells, the trabeades. The opercule is simply a piece of the epi- derm of the sporange. In most genera a portion of the wall of the sporange, situated near the base of the columel, consists of an assimilating system composed of spongy or palisade- parenchyme, containing chlorophyll, and marked by the presence of sto- mates. If the detachment of the oper- cule leaves the mouth of the sporange with a smooth edge, it is said to be^';;^- nosto7nous, as in Pottia (Ehrh.). More often the mouth of the open sporange is furnished with hair- or tooth-like appendages, arranged in one or two rows, constituting the peristome. The single row of these appendages, or the outer row if there are two, are called teeth, the inner row cilia. In some genera the cilia are furnished with lateral processes uniting them with one another, or they are replaced bv a lattice-work of longitudinal or trans- verse ridges termed the e?idostome. The inner and outer layers of both teeth and cilia differ from one another in their hygroscopic capacity: hence, as the moisture of the air varies, they bend inwards and outwards, or some- times coil spirally round one another (Barbula, Hedw.). The peristome has a very beautiful appearance under the microscope, and its structure furnishes useful characters for the discrimination of the genera. In most genera the teeth and cilia are not composed of cells, but of pieces of thickened cell-wall which become detached from a Fig. 112. — A, longitudinal section of spo- range of Pofytrichujn pilifcrum Schreb. ( X 15). B, transverse section( x 5 ■. iv, wail of sporange ; cii, opercule ; c, columel ; /, peristome ; ep, epiphragm ; a, annulus ; i, air-spaces traversed b}- trabecules ; s, spore-sac : ap. apophyse ; st, seta. (After Lantzius-Beninga.) L 2 148 MUSCINE^ layer of cells beneath the epiderm ; but in Polytrichum the teeth are composed of bundles of thickened prosenchymatous cells. The exterior peristome may have two distinct forms. Either the teeth have a double outer and a single inner series of plates {Diplolepidce)^ or the exterior series is simple {Aplolepidce\ and then the inner series is nearly always double. The Aplolepidae never have a double peristome ; and in the Diplolepid^ the inner peristome is occasionally wanting in particular families or genera. In much the larger number of genera {Arthrodontece) the teeth are septated by transverse walls ] in a much smaller number Fig. 113. — Hypnutn populeum Sw. (natural size). Fig. 114. — Tetraphis pelhicida Hedw. a (slightly magnified), with open sporange ; b, ditto with gemma ; c, sporange with calypter (greatly magnified) ; d, open sporange, showing - . peristome. Fig. 115. — Bryuvi argenteum L. Fig. 116, — Splachnum am- (natural size). ptdlaceuni L. (natural size). (^Nematodontece) the transverse septa are wanting. The cilia, when present, are usually shorter and less developed than the teeth ; they are also composed of two layers of plates, often marked on the surface by a beautiful network ; their divisions correspond to those of the teeth. The number of both teeth and cilia is always a multiple of 4, the most common numbers being 8, 16, 32, and 64. The most perfect type of peristome is seen in the Encalyptese, from which all the less perfect forms are, according to Philibert, derived by degradation. In addition to the presence of an epiphragm, the genus Polytrichum presents the peculiarity, in most species, of the seta being swollen beneath the spo- range, forming an annular cushion known as the apophyse (see fig. 112). MUSCI 149 In most Bryaceas the tissue of the leaf is nearly homogeneous, with the exception of the margin and an elementary midrib composed of elongated prosenchymatous cells; but in Leucobryum (Hpe.) the small chloro- B A V, c Fig. 117. — Sporange o^ Poly trichuni commune, showing epiphragm. A , covered by calypter ; B, with calj"pter removed ; C, with opercule removed (magnified). Fig. 1 1 3.— Sporange of Hypnnm populcum, showing peristome (magnified). phyllous cells interlace among large empty cells with circular orifices in their walls, as in Sphagnum, The very numerous genera of Bryaceaeare further classified as under. Acrocarpi. — Fructification produced at the extremity of the branches. Ilhistrative ge?iera : — Weissia (Hedw.), Dicranum (Hedw.), Leucobryum (Hpe.), Pottia (Ehrh.), Tortula (Hedw.), Bartramia (Hedw.), Encal\'pta (Schreb.), Fissidens (Hedw.), Grimmia (Ehrh.), Or- thotrichum (Hedw.), Zygodon (H. «S: T.), Tetraphis (Hedw.), Buxbaumia (Hall.), Polytri- chum (Dill.;, Aulacomnion (Schw.), Br>-um (H. & T.), INInium (B. & S.), Funaria (Schreb.), Splachnum (B. ^ S.), Tayloria (Hook.), Barbula (Hedw.), Ceratodon (Brid.). Pleurocarpi. — Fructification lateral, not at the extremity of the prin- cipal branches. Illustrative genera : — Hedwigia (Ehrh.), Fontinalis (L.), Hookeria (Sm.), Hypnum (Dill.), Leucodon (Schw.), Neckera (Hed^-.). Fig. 119. — Peristome ot A trichu7>i undulaUnn (magnified). Fig. 120, — Peristome ot Cinclidijun stygium (magnified . Literature (in addition to the papers already quoted). Philibert— (Peristome) Rev. Bryol., 1884-1S88. Vaizey— (Polytrichace^) Journ. Linn. Soc, xxiv. (iS8S,\ p. 162. ISO MUSCINEjE Order 2. — Phascace^. In the small order of Phascace^e the roundish sporange dehisces neither by the detachment of an opercule nor by longitudinal slits, but decays to allow of the escape of the spores ; the calypter is ruptured laterally without being raised up as a cap ; the columel is sometimes wanting. According to Leitgeb, Archidium (Brid.) resembles the Hepatic£e more closely than the Bryaceas in the processes which lead to the formation of the spores, especially in the differ- entiation of the archespore into spore-mother-cells which are Fig. 121. — Ephejueru'n se-rratutn Hampe ; mature plant with persistent protoneme (magnified). (After Luerssen.) Fig. 122. — Plettridhivi sitbulatuni Rabenh. sporange (magnified). (After Luerssen. irregularly interspersed among cells that remain sterile. The spore- mother-cells do not number more than from one to seven in each spo- range ; in each of them four spores are formed tetrahedrally. The Phascaceae are caespitose in their habit ; the protoneme persists until the maturity of the sporogone. Principal genera : — Phascum (L.), Archidium (Brid.), Ephemerum (Hpe.), Pleuridium (Brid.). Literature. Leitgeb— Sitzber. Akad. AViss. Wien, i88o, p. 447. Miiller— Pringsheim's Jahrb. wiss. Bot., 1867, p. 237. Order 3. — Andre^eace^e. The Andreaeaceas constitute a small order of mosses, comprising the single genus Andreaea (Ehrh.), characterised by the absence of an oper- cule to the sporange, which opens by four, or very rarely eight, longi- tudinal slits, not reaching either to the base or the apex of the capsule. MUSCI 1^1 The calypter is elevated, as in the Bryace^e, on the summit of the ripe sporogone in the form of a cap ; there is a short seta buried in the vagine, and the whole sporogone is elevated on a stalk or pseiidopode, as in the SphagnacecT. At the base of the sporange is an enlarged apophyse. The structure of the sporange differs from that of ,1 ;!/,- the Bryacese in the columel not penetrating the archespore, and in the absence of a cavity be- tween the spore-sac and the wall of the sporange. The con- tents of the spore divide, while still within the exospore, into four or more cells. As in Sphag- num, the oosphere is always enveloped in a hyaline mass of mucilage in which the anthero- zoids imbed themselves. The Andreseaceje are also caespitose in their habit, and are natives of cold or mountainous Fig. 124. — A. alpestris Schmp. ; dehiscent spo- range and apophj^se (magnified). regions. Fig. 123. — AndrecFa alpestris Schmp. (X 5). Literature. Kiihn — Entwickelungsgeschichte der Andregeaceen, 1870. Waldner— Bot. Zeit., 1879, P- 595 J and Entwick. d. Sporogone v. Andreaea, 1887. Order 4. — Sphagnace.f. The bog-mosses form a large portion of the vegetation of bogs and swamps, and are characterised by the spongy structure of the whole plant, the light yellowish green colour of the leaves, and the bright red globular spore-capsules. The protoneme is much less developed than in typical mosses ; and when the spore germinates on dry ground a flat prothalliiDn intervenes between it and the leafy stem. The stem branches abundantly, giving a cjespitose appearance to the whole plant ; and imiovations^ produced below the apex after the ripening of the fructification, become detached by the decay of the lower part of the stem, and carry on an independent existence. The leaves are lanceolate and apiculate, usually arranged in a f phyllotaxis, larger than in other mosses, and of a peculiar structure of their own. As the leaf develops, 152 MUSCINEAL the single layer of cells of which it is composed becomes differentiated into cells of two distinct kinds. A comparatively small number, of a lozenge-shaped form, grow to a large size and lose the whole of their con- tents, while their walls are provided with spiral thickening-bands, and fre- quently display a large circular orifice opening from one cell into the next. A much larger number of cells remain permanently of a very small size, are very narrow in proportion to their length, and, being filled with protoplasm and chlorophyll, constitute the whole of the nutritive tissue of the leaf. These nutritive cells form a kind of network ramifying among the large empty cells ; but, as their total area is small com- pared with these latter, the entire leaf has, to the naked eye, a semi-trans- parent very light yellow-green appear- ance. The tissue of the stem consists of cells of three distinct kinds. In the centre is a cylinder of thin-walled elongated colourless parenchymatous cells j this is enveloped in a layer of dotted prosenchymatous cells, the walls Fig \-z-- 3- — Sphagnum acictifoliutJi Ehrh. A , megaspore ; B, microspore ; C, proto- neme, with/r, rudiments of voung plants (magnined). (After Schimpe'r.) Fig. 126. — Flat prothallium of 5". acutifoliiim, with j-oung leafy stems (x 120). (After Schimper.) of which are thicker and of a brown colour : while outside all is an epidermal layer of large thin-walled empty cells, sometimes with spiral MUSCI 153 thickenings and circular orifices, similar to those of the leaves. These serve as caj^illary tubes, through which the water of the bogs in which these mosses grow is raised, and the whole plant is in consequence always saturated with water like a sponge. 7? '^ Fig. 127.—^, portion of surface of leaf of 6". acittifolium. cl, small chlorophyllous cells ; f, large empty cells ; /, orifices in these cells. B, transverse section (magnified). Fig. 128. — Transverse section of stem of ^. (ywi^//i7//z«;^ Dill, x, inner cells with colourless wall ; r, outer layer of cells ; ee, peripheral laj-ers of cells with orifices, / ( x 900). (Aft r Luerssen.) 154 MUSCINE.-E In their organs of reproduction, and especially in the structure of the sporogone, the Sphagnaceae exhibit some divergences from the typical mosses. Some species are dioecious, and the ' flowers ' of the moncecious species are never hermaphrodite, the male and female organs being always distributed on different branches. The male branches are distinguished by their densely crowded leaves, which are often of a bright red colour, giving a catkin-like appearance to the branch. On removing these the antherids are found near the middle of the branch. They are minute nearly globular or elliptical bodies, elevated on a slender stalk, and dehiscing by longitudinal fission into valves. The an- therozoids are spiral bodies with many coils, and two large flagellate cilia at the posterior end. The arche- gones are formed towards ^lyt the extremity of the female • branches, are accompanied by paraphyses, and are enveloped by perichaetial leaves. They resemble in all essential points those of other mosses. On impreg- nation the oosperm divides by a horizontal septum into two cells, the sporogone ori- ginating from the upper cell only. The nearly spherical usually bright red sporange differs from that of other mosses in being completely enclosed within the venter almost till maturity. It is, in most species, elevated on a long slender pedicel, the pseudopode, which must not be confounded morphologically with the seta of other mosses, being a prolongation of the axis below the vagine. The lower portion of the sporogone is widened out into a broad disc-like foot, resembling in appearance the apophyse of Polytrichace^e, which is seated on the top of the pseudopode, and enclosed in the vagine. The calypter, when finally ruptured, is not elevated in the form of a cap, but remains attached as a Fig. 129. — 5'. acjitifoliuni. a, antheridial branches ; b, leaves of primary' siem ; ch, perichaetial leaves with sporogones(x 5). (After Schimper.) MUSCI 53 frill to the base of the sporange, which dehisces by a transverse slit near the apex, detaching a strongly convex opercule. There is no peristome nor annulus. A portion of the contents of the sporange remains un- differentiated in the form of a low columel not reaching to the apex. The remainder is converted into spores, which differ from those of other mosses in being of two kinds, megaspores and microspores (see fig. 125). According to Warnstorf (' Hedwigia,' 1886, p. 89 ; and ' Verhandl. Bot. % • » ♦ t • Fig. 130.— i". acutifoluini. A, male branch, with leaves removed to expose antherids, a (magnified). B, antherid (more highly magnified) dehiscing. C, antherozoid (still more magnified). (After Schimper.) Fig. 131. — --i) 6". acutifoliuvi, section of female inflorescence ; ar, archegones ; ch, perichaetial leaves. B, longitudinal section of sporogone, sg ; ar, archegone ; c, calj^Jter ; sg" , foot ; v, vagine ; ps, pseudopode. C, S. squarrosum Pers. ; sg, sporogone ; d, opercule ; c, ruptured calypter ; qs, pseudopode ; ch, perichaetial leaves (magni- fied), (After Schimper.) Verein,' Brandenburg, 1886, p. 181), these two kinds of spore are found either in the same or in different sporanges ; the diameter of the former varies between 30 and 33 mm., that of the latter between 12 and 18 mm. The megaspore is by far the most common form, and its germination only has at present been observed. AVarnstorf suggests that the two kinds are sexually differentiated, the megaspores giving rise to a female, the micro- spores toamaleprothallium, as in the Heterosporous Vascular Cryptogams. 156 MUSCINEyE All the species of the single genus Sphagnum (L.) grow in bogs and swamps, often covering enormous tracts of ground, and entering largely into the composition of peat. The best authorities differ widely as to the number of species; the most divergent forms are distinguished by well-marked characters, but these merge into one another by a com- plete series of connecting links. Literature. Schimper — Entwickelungsgeschichte der Torfmoose, 185S. Waldner — Bot. Zeit., 1879, p. 595 ; and Entwickelung d. Sporogone v. Andreaea u. Sphagnum, 1S87. Braithwaite — Sphagnace^e of Europe and North America, 1880. Warnstorf — Die Europ. Torfmoose, 1881 ; and Flora, 1SS4. Limpricht — Bot. Centralbl., x. , 1882, p. 214. Roll— Flora, 1886. Class VIII.— Hepaticae. The Hepaticae or Liverworts are small elegant plants, usually of a bright green colour, which are especially abundant on damp ground or rocks, or by the sides of streams ; a few species are aquatic. Some of the genera bear a considerable external resemblance to lichens, others to mosses. Their vegetative structure is either an undifferentiated thallus, or consists of a distinctly differentiated stem and leaves, in both cases attached to the soil by rhizoids. The former are known as the Thalloid or Fro7idose, the latter as the Foliose Hepaticce. The transition marks the passage from the upper of the two great divisions of the vegetable kingdom, the Cormophytes, to the lower division, or Thallophytes : but intermediate forms occur in the genera Fossombronia (Rad.) and Blasia (Mich.). Even the foliose forms have no true vascular tissue, and no true roots, the functions of which are performed by the rhizoids. Both sections have, except in Riella (Mont.) and Haplomitrium (N. ab E.), a distinct bilateral or dorsiventral structure ; the free side which faces the light is differently organised from that which faces and often clings to the substratum, and which is not exposed to light. The mode of branching in the thalloid forms is dichotomous, and the growing region of the shoot commonly lies in an apical depression formed by the more rapid growth of the cells lying right and left of the apical cell, which has a form allied to wedge-shaped. The filiform stem of the foliose forms, on the other hand, ends in a bud with a more or less prominent cone of growth, and the apical cell is a three-sided pyramid. The leaves of the foliose forms always consist of only a single layer of cells, without even a rudi- mentary midrib ; while the stem sometimes contains the first rudiments HEP A TICyE 157 '•^ f^ ^ ^"t^\ of vascular bundles in the form of cambium-strings, and is furnished with a slightly differentiated epidermal layer. In the thalloid forms the thallus is composed of a more or less thick plate of tissue, which in one order, the Marchantiacese, possesses on the upper side a strongly developed epiderm, provided with stomates of very peculiar form, unlike anything that occurs elsewhere in the vegetable kingdom. The first result of the germination of the spore is either a filiform protoneme, a flat plate of cells, or a mass of tissue ; but the differentia- tion of the protoneme from the sexual genera- tion is not so well marked as in the IMusci. The non-sexual propagation of the Hepaticce takes place either by innovation^ i.e. by the continual dying away of the stem behind, or by j^enwKB, which exhibit a high degree of development. In the thalloid genera Marchantia (L.), Lunularia (Mich.), and Blasia, these gemmae are found in peculiar outgrowths of the upper surface of the thallus known as cupules, which are cup-shaped in Marchantia (see fig. 150), crescent-shaped in Lunularia, flask-shaped in Blasia. From the base of these cupules there spring hair-like papillae, the apical cells of which divide re- peatedly in both directions, and constitute the gemmae. In some of the foliose genera, e.g. Madotheca (Dum.), the gemmae are formed out of cells belonging to the margin of the leaf, and simply detach themselves. Vochting states that in Lunularia, and Marchantia also, isolated masses of cells possess the power of regenera- tion or development into new individuals, to whatever part of the thallus they may have be- longed. Shoots resembling a normal thallus spring from the pedicel of the inflorescence of Marchantia polymorpha (L.) when lying pros- trate on the soil. The locality of the sexual organs of reproduction, antherids and archegones, varies in the different orders. In one genus, Anthoceros (Mich.), they are endogenous, or originate in the tissue of the thallus itself ; in the remaining thalloid forms they are produced on the upper side of the thallus ; and in the ]\Iarchantiaceae on special vertical out- growths, some of which bear antherids on their upper, others archegones mm K^ >"^*> ^^■r. " \J .... \>i - Fig. 132. — yungcrmantiia nemorosa L. (x lo). 158 MUSCINE/E on their under side ; these male and female i?iflorescences^ as they are termed, may be either monoecious or dioecious. In the foliose orders there is a great variety in their locality and mode of origin. The antherid originates as a papilliform swelling of a super- ficial cell, from which it is marked off by a septum. When mature it is seated on a pedicel or stalk, and consists of an external layer of cells containing chlorophyll, which encloses the mother-cells of the antherozoids. The antherid dehisces by longitudinal fissures into valves, and the mother-cells themselves escape into the sur- rounding moisture, into which each discharges an antherozoid. The antherozoids are slender threads of protoplasm, with from one to three spiral coils, and are provided at the anterior end with two long and very slender cilia, by means of which they ' swarm ' in the water with a rotating motion. The archegone also first makes its appearance as a papillose out- growth of a superficial cell, which then becomes separated in the same manner. After this mother- cell has divided several times longitudinally, the central one of Fig. xii.—Gottschea appendiculata N. ab E. (magnified). the cells thus formed divides transversely into an upper stigmatic or lid-cell and a lower cell. Two layers are subsequently formed, the upper of which becomes the neck of the archegone, the lower its ventral HEPATIC AH 159 portion, or venter. The lowermost cell of this ventral portion, now known as the ce?ifral cell^ increases considerably in size, and divides by a transverse septum into a lower and larger portion, which encloses the oosphere, and an upper and smaller portion, the ventral ca?ial-ceIL In the meantime the upper layer of cells increases in length by the formation of a number of fresh cells, the neck-canal-cells. The ventral portion of the archegone becomes eventually enclosed in a wall, and by the deliquescence of the neck-canal-cells an open channel is formed down to the oosphere. In addition to the perichaete, the archegones are frequently surrounded by a circular wall originating as an out- growth of the thallus, and known as the perigyne or involucre. The result of the impregnation of the oosphere by one or more antherozoids is the production of the embryo, from which is derived the sporogone, which alone constitutes the sporophyte, or non-sexual genera- tion. It is formed entirely from the ventral portion of the archegone. Its external form and internal structure vary greatly in the different groups : as is also the case with the course of cell-divisions in its forma- tion. Ultimately the wall of the spore-capsule becomes differentiated from the archespore, or layer of tissue which develops into the mother- cells of the spores and elaters when these latter organs are present. There is usually no solid axis or columel. The cells which develop into elaters cease early to divide transversely, and thus remain long, while the rest of the cells round themselves off, and become mother-cells of spores. The mature elaters (fig. 159) have in their wall an elongated single or double spiral band, the twisting and untwisting of which on the absorption and giving off of moisture helps to disseminate the spores. Leclerc du Sablon finds the sporogone of the typical Hepa- ticae to be composed, at a very early stage, of sixty-four cells, each of which subsequently divides into four. These cells now elongate in the direction of the axis of the sporogone, and then become differentiated into two kinds. In the one kind the nucleus undergoes repeated bipartitions, and these give rise to the spore-mother-cells ; in the other kind the nucleus does not divide, and the protoplasm forms spiral granulations ; these become the elaters. Rarely (as in Riella) they are replaced by barren cells filled with food-material for the nutrition of the growing spores. The two kinds of cell are equal in number, each alternating with the other. The degree of complexity of the sporogone in the different orders of Hepaticae corresponds in the main to the degree of development of the vegetative organs. In the Jungermanniaceae it bursts longitudinally into four valves, and the walls are composed of two lavers of cells furnished with 'ornaments,' or elevated markings of various patterns ; in the Anthoceroteas it splits longitudinally into two valves ; i6o MUSCINE.'E in the Ricciaccc^ and Marchantiaceae it bursts irregularly, and the wall is composed of a single layer of cells without ornaments, or nearly so. The spores also vary considerably in the different orders. In many Jungermanniaceas the spore has only a single cuticularised membrane, which is entirely used up in the formation of the germinating filament. In most genera the wall is composed of two distinct separable layers, the exospore and endospore ; while in Sphaerocarpus (Mich.), Corsinia (Radd.), and some others there is a third outer layer, often beautifully sculptured, which is derived from the membrane of the special mother- cells of the spores. This layer is called by Leitgeb the periniiau. AVarnstorf (Verhandl. Bot. Ver. Brandenburg, 1886, p. 181) finds in Blyttia (Endl.) two kinds of spore, larger and smaller, which he believes to produce female and male plants respectively. In Sphaerocarpus the spores are combined into tetrads. When the spore germinates, the endospore breaks through both exospore and perinium, when the latter is present, and protrudes as the first rhizoid. Literature. Bischofif— Nov. Act. Acad. Leop. Car., 1835. Gottsche— /(^/^., 1838. Gottsche, Lindenberg u. Esenbeck — Synopsis Ilepaticarum, 1844. Kny — Pringsheim's Jahrb. wiss. Bot., 1865, p. 64. Leitgeb — Bot. Zeit., i87i,p. 557, and 1872, p. 33 ; r^Iittheil. naturw. Ver. Steiermark, 1872 ; Unters. liber die Lebermoose, 1874-1881; and Ber. Deutsch, Bot. Gesell., 1883, p. 246. Janczewski — (Archegone) Bot. Zeit., 1872, p. 372 et seq. Carrington— British Hepaticae, 1874. Kenitz-Gerloff — Bot. Zeit., 1875, pp. 777 et seq. Vochting — Pringsheim's Jahrb. wiss. Bot., 1885, p. 367. Satter — Sitzber. Akad. Wiss. Wien, 1882. Leclerc du Sablon — (Antherozoids) Comptes rendus, cvi., 18S8, p. '^'](>. Liverworts are distributed throughout the entire globe, growing mostly in moist situations. Many tropical species are epiphytic on the leaves of Flowering Plants or ferns. They are of no economic importance. They are classified under five orders, of which the first includes both foliose and thalloid, the remaining four almost entirely thalloid, forms. Order i. — Juxgermanxiace.e. In this, much the largest order of the class, are included genera with every variety of vegetative development, from an undifferentiated thallus to a slender filiform stem, with sessile leaves seated either in two rows on the upper side, or in three rows, two of them on the upper, and the third, the a?nphigasters, smaller and adpressed to the under side. The thalloid HEP A TIC.-E i6r forms have, except in Haplomitrium, a bilateral structure resembling that of the Marchantiace^ : rhizoids and rudimentary foliar structures are formed on the under, the sexual organs on the upper side. In the foliose forms the leaves, always very small, are frequently bisected or bilobed, the lower lobe or auricle being the smaller one. and amplexicaul or concave. Goebel states that in Java many of the Jungermanniaceae are epiphvtic, and that in these the auricle is frequently hollowed out into the shape of a pouch or pitcher, serving as a receptacle for water (fig. 140). In some species of Physiotium (X. ab E.) this receptacle is prolonged into the so-called "tubular organ.' The leaves of the foUose Fig. 135. — Fossonihronia pnsilla'S. . ab E., male plant, a, natural size ; b, magnified. Fig. 134. — Calypogeia Trichomanis Cord, (magnified). species consist of a single layer of cells without even the rudiments of vascular bundles. There are species which form a connecting link between the foliose and the thalloid Jungermanniace^. The mode of branching varies greatly, but growth always takes place by means of a three-sided pyramidal apical cell. As respects the sexual organs, some species are monoecious, others dioecious. In the foliose genera they are usually formed at the apex of the primary shoots or of special small fertile branches, which have often an endogenous origin on the ventral side. These constitute the acro- gynous section of the order, which includes all the foliose genera except Haplomitrium. In the thalloid genera, or anacrogy-nous section, they M l62 MUSCINE.E appear on the dorsal surface of the shoot, at some distance from the apex ; while in the acrogynous forms they are formed in close proximity to the apical cell. In Radula (Dum.) the entire female inflorescence, com- posed of a number of archegones enclosed in a perigyne, is developed from the apical cell of a shoot, and from its youngest three segments. Neither archegones nor antherids are elevated on receptacles, as in the Mar- chantiaceae. The antherids usually occur Fig. 136. — Pellia- epiphylla Cord., male plant, a, natural size ; b, magnified. Fig. 137. — Radjila coijzpla- nata Dum. Plant with closed and open sporange (X 2). Fig. 138. — Jtingermnnnia barbata Schreb. Under side of leaves with ciliated amphigasters (magnified). singly or in groups in the axils of the leaves. In Pellia (Radd.) the an- therids are imbedded in the thallus, the archegones appearing in large numbers at the apex of the shoot. In the Geocalycese {e.g. Calypogeia, Radd.) the female branches are so hollowed out that the archegones are ir. Fig. 139. — I. Under side of stem of Fncliania Tajuarisci Dum., with true leaves and amphi- gasters (magnified). II. Leaf of F. dilatata (more magnified). Fig. 140. — Auricle of Frnllauia. sp. (mag- nified). (After Goebel.) sunk in a deep pitcher-shaped hollow or tube, within which the spo- rogone is subsequently formed. In other genera they are concealed by the nearest leaves. The modified leaves which thus enclose a group of archegones, or of both archegones and antherids, constitute the perichcete., HEP A TIC.-E 163 each archegone being, in addition, usually surrounded by a distinct mem- branous envelope, the perianth ox perigyne. In the formation of the sporogone, the fertilised oosphere first divides by a wall at right angles to the axis of the archegone. Only the upper of the two cells thus formed — that is, the one that faces the neck of the archegone — undergoes further divisions ; it becomes the apical cell of the sporogone, and sometimes again divides transversely once or twice before a longitudinal wall makes its appearance in it ; the two cells thus formed finally divide into four apical cells arranged as octants of a hemi- sphere. The basal portion of the growing archegone swells out and penetrates down into the tissue of the stem, forming the valine. Fig. 141. — Sexual organs of R adicla complatiata. ar^ archegone ; an^ an- therid ; b, leaf, (After HofmeLter.) Fig. 142. — Jungerviann'a bicuspidata L. Longi- tudinal section of immature sporogone, sg ; ar, calypter ; ar" , unfertilised archegones ; /, base of perigyne ; st, stem ; b, leaf. (After Hofmeister.) After frequent divisions have taken place, the wall of the spore-capsule becomes differentiated from the inner tissue, out of which are developed the spores and elaters. There is no columel. By rapid extension of the hitherto short pedicel, the calypter is ruptured at the apex, and the globular sporogone, containing the already ripe spores, becomes elevated. The inner of the two layers of which the wall of the sporogone is com- posed has become absorbed before the ripening of the spores ; the single layer of cells which still remains is ruptured at the apex, and splits into four (rarely more) longitudinal valves, which separate suddenly in the form of a star, carrying with them at the same time the elaters, and thus bringing about the dispersion of the spores. The mature elaters are M 2 164 MUSCINE.-E long fusiform thin-walled cells, marked internally by from one to three brown spiral bands, but more complicated in structure in the foliose than in the thalloid genera. Illustrative genera. — Foliose : Radula (Dum.), Jungermannia (L.), IvCJeunia (G. & L.), Frullania (Radd.), Madotheca (Dum.), Mastigo- bryum (N. ab E.), Calypogeia (Radd.), Lepidozia (Dum.), Plagiochila (Dum.), Geocalyx (N. ab E.), Chiloscyphos (Cord.), Gymnomitrium (N. ab E.), Lophocolea (Dum.). Thalloid', Metzgeria (Cord.), Aneura (Dum.), Fossombronia (Radd.), Pellia (Radd.), Blasia (Mich.). Literature. Leitgeb — Bot. Zeit., 1871, p 556 ; and Abhandl. Bot. Ver. Brandenburg, 1880, p. 58. Gottsche — Abhandl. Gesell. Naturf. Hamburg, 1880, p. 39. Goebel — (Epiphytic Species) Ann. Jard. Bot. Buiienzorg, vi., 1887, p. 21. Order 2. — Monocleace.^. This small order appears to occupy an intermediate position be- tween the Jungermanniaceae and the Anthocerote^e. The vegetative structure is either thalloid or foliose. The elongated sporange dehisces longitudinally, and contains elaters, but has no columel. Principal genus \ — Monoclea (Hook.). Fig. 144. — Anthoceros la^vhY,., male plant (natural size). Fig. \d,2,.—Mono:lea ForstcnYiQ(^. (magnified). Fig. 145. -A. Icez'is. a, dehiscent sporange (X 2). Order 3. — Anthocerote^. The vegetative structure consists of a flat ribbon-like thallus, the irregular dichotomous ramifications of which form a circular disc composed of one or more layers of cells, each cell containing only a HEPATIC.-E 165 single chlorophyll-corpuscle. The antherids and archegones arise endogenously on the upper side of the thallus, apparently without any definite arrangement, and are not protected by a perigyne. The mature sporogone is an elongated dehiscent two-valved pod, provided with stomates, which forces its way through a mass of tissue overarching the archegone, and is known as the involucre. "Within the sporange is, in most genera, a solid axial co/umel ; the wall consists of four or five layers of cells ; the rest of the contents, developed from the archespore, becoming the mother-cells of the spores and elaters. Except in some species of Anthoceros (L.) the elaters are of simpler structure than in the other Hepaticce, having no spiral bands. Anthoceros possesses peculiar cavities on the under side of the thallus, opening by slits or fissures, which are regarded by some authors as stomates, by others as mucilage- receptacles. Filaments of Xostoc, which have found their way into these cavities through the slits, cause peculiar changes in them, and have been mistaken for endogenous gemmae. The genus Anthoceros is of much interest from the fact that the sporophyte-generation shows a greater vegetative energy than is usually the case with Muscincce ; growth continues at the base of the sporange, and new spores are formed there after those at the apical portion are already mature. Principal genus \ — Anthoceros (L.). Literature. Leitgeb — Die Anthoceroteen, 1S79. Order 4. — Ricciace.e. The Ricciaceae are regarded by Leitgeb as forming a connecting link between the Jungermanniaceae and the ^larchantiaceas ; but in some re- spects they are simpler in their structure than either of these orders. The thallus is usually flat, and branches dichotomously ; it floats on water or roots in the soil. In Riella (Mont.) it is submerged and erect, and has the appearance of a ring forming a continuous spiral round an axial stem. It is always destitute of stomates, but is provided with internal air- cavities, and with rudimentary foliar organs among the rhizoids. The antherids and archegones are not, as in the Anthoceroteae, endogenous, but are developed from young superficial cells of the upper surface, which grow into papilla and become overarched, in the course of their development, by the surrounding tissue. Both antherids and archegones are enclosed in an involucre formed in this wav ; the antherids are sessile, the involucre sometimes constituting an elevated neck above them. In Riccia (L.) the archegones are ultimately buried in the 1 66 muscinea: thallus; while in Oxymitra (Bisch.) they are raised above the surface. The sporange is a thin-walled spherical capsule, occasionally produced under water, entirely filled with spores without true elaters or columel, and, with its calypter, depressed in the thallus. It is much less differ- entiated in its structure than in the other orders. In all the genera except Riccia and Oxymitra the elaters are represented by sterile Cells among the spore-mother-cells. The spo- range bursts irregularly when ripe, but the spores are only set free by the decay of the •r-<^::J v>a:li^ Fig. 147. — Sphcerocarpjis terrestris Sm. Frond and archegone (magnified). (',/ Fig. z\6.—Riel/a helicophyila Mont, (magnified) Fig. 148. — Riccia glauca L. A, section of apical region of frond, ar, archegone ; c, oosphere ( x 50). B, immature sporogone, sg\ ar, neck of archegone (x 300). (After Hof- meister.) surroundmg tissue of the thallus. The spores of Sphaerocarpus (Mich.) and Corsinia (Radd.) have a beautifully sculptured extine. Riella is altogether dioecious, and perfects its fructification beneath the water. Principal genera : — Riccia (L.), Duriaea (Bor.), Oxymitra (Bisch.), Riella (Mont.), Sphaerocarpus (Mich.), Corsinia (Radd.)- Literature. Kny— Pringsheim's Jahrb. wiss. Bot., 1866, p. 364. Leitgeb — Die Riccieen, 1879. HEP A TICyE 1 67 Order 5. — Marchaxtiace.^. The thallus is flat and ribbon-shaped, and usually branches dicho- tomously from two apical cells; it is frequently furnished with a well- '■** re':! '^ Fig. 149. — Marchantia folymorpha L. Male plant (natural size). Fig. I re- marked distinct -M. polymorpha. Male inflorescence and cupule (magnified). Fig. 151. — ISI. pclyvtorpha. Female inflo- rescence (magnified). Fig. 152. — Fcgatella conicn Cord. Male plant (natural size). midrib, and is coriaceous in texture. It is composed of three layers of cells, viz.: — (i) the air-chamber-layer to which the i68 MUSCINE^ stomates belong; (2) a close tissue containing but little chlorophyll, and with the cell-walls pitted or reticulately thickened, without intercellular spaces but sometimes containing mucilage-receptacles ; and (3) a ventral Fig. 153. — A, transverse section through middle portion of thallus of M. polyjnor^ha (x 30); B, through marginal portion (more highly magnified), p, colourless layer without intercellular spaces o, epiderm of upper side ; chl, chlorophyllous layer ; sp, stomate ; s, partition-walls between air- chambers ; 21, lower epiderm ; h, rhizoids b, leaf -like lamellae. (After Goebel.) Fig. 154. — Portion of young receptacle of M. polymorpha. A, vertical section; S', partition-wall separating air-chamber from chlorophyllous cells ; g, mucilage-cell. B, C, young stomate ; po, pore. (After Goebel.) epidermal layer, from which spring rhizoids and leaf-like lamellae. The mucilage-passages are especially developed in Fegatella (Radd.) and HEP A TIC^ 169 Preissia (Cord.), and the thallusof the latter genus has also rudimentary vascular bundles. The stomates which penetrate the epidermal layer of the upper surface of the thallus into the air-chamber-layer are of a struc- FiG. 155. — A, B, C, young shoot oiM. poly- inorpha (slightly magnified) with cupules ; w^ apical region. D. portion of epiderm (more highly magnified), sp, stomate. Fig. 156.— Female inflorescence of M. foly- inorpha seen from the under side, sr, radiat- ing branches ; f, sporogone. (After Goebel.) ture quite peculiar to this order. Each stomate is formed, according to Leitgeb, by the simple separation of four or more superficial cells, and the subsequent segmentation of these in a direction parallel to the surface. Fig. 157. — A, male plant of M. polymorpha. B, longitudinal section through inflorescence, ha o, 0, openings to antheridial cavities, a. C, nearly ripe antherid. Z>. two antherozoids (x See). (After Goebel.) They are situated in the centre of plates of a rhombic form, consisting of portions of the epidermal layer which overarch large air-cavities. From the base and sides of these air-cavities spring chlorophyllous cells 170 MUSCINE^ in rows directed upwards, but not actually reaching the epidermal layer of cells through which the stomates penetrate ; while beneath them is the non-chlorophyllous layer, consisting of cells longest in the hori- zontal direction without intercellular spaces. Each stomate has a number ^__ of guard-cells formed by radial cell-divisions. The details in the structure of the stomates differ in the different genera. Leitgeb describes them as of two kinds, simple and canali- culate. The former are epidermal pores situated immediately above the air- chambers ; the latter, which occur in Marchantia and Preissia, have the ap- pearance of canals exca- vated in the surface of the thallus. Some of the rhi- zoids of Marchantia are characterised by singular internal thickenings to the cell-wall. The peculiar non- sexual organs of propagation of ^Marchantia, Lunularia (Mich.), and other genera, known as cupules^ have already been described (figs. 150, 155). A peculiar non- sexual mode of propagation by means of gemmae occurs in Fegatella (Radd.). The sexual reproductive organs of the Marchanti- aceae are, in most of the genera, borne on erect branches of the thallus of a peculiar umbrella-like form, which have been variously termed receptacles^ discs ^ and inflorescences. They may be male, female, or bisexual ; and, when unisexual, the species may be monoecious or dioecious. In Fegatella the male inflorescences are oval discs sessile upon the thallus (fig. 152). The inflorescence is generally regarded Fig. 158. — Development of archegone of M. polymorpha (x 300). / — F", before, VI — VIII, afcer fertilisation, e, central cell with oosphere ; f, young embrj-o ; si, lowest cell of axile row ; pp, perigyne. IX, immature sporogone in venter of archegone (x 30); a, neck of archegone ; st, stalk of sporange which contains young spores and elaters. (After Goebel.) HEP A TIC.-E 171 as a transformed thalloid axis. The antherids spring from superficial cells of these branches which are depressed in hollows on the upper surface of the disc, and become overarched by the surrounding tissue. With the exception of one section, the Targioniese, in which they occur at the apex of ordinary shoots, the archegones are borne on the under surface of the female discs, which are always stalked, while the male discs may be either stalked or sessile. The archegones are variously surrounded by invohiC7'es or perigynes. Leitgeb describes the sexual organs as being at first distributed over the surface of the thallus, and becoming subsequently collected into groups or inflorescences, which have at first a dorsal position, but become con- stantly pushed towards the apex. The mature sporange is usually shortly stalked, and contains elafers, which radiate from the centre towards the circumference. It has no central columel. It either dehisces at the apex with numerous teeth, or is four-lobed, or the upper portion becomes detached by an annular fissure as an opercule. The elaters are well developed, and are furnished with several spiral bands, but do not usually appear to take any part in the expulsion of the spores from the sporange. The thallus of many ]\Iarchantiaces displays remarkable hygroscopic properties, which have their seat in the 'mechanical' layer, i.e. the layer of closely packed cells containing but little chlorophyll, which underlies the air-containing assimilating layer. On desiccation this layer contracts greatly, so that the epidermal layer with its stomates is completely pro- tected from further evaporation by the recurved ventral surface covered with brown or violet scales. In this condition the dried -up thallus may retain its vitality for a very long period. The cells of the mechanical layer are frequently occupied by colonies of Xostoc. Illustrative genera : — Marchantia (L.), Targionia (L.), Fegatella Fig. 159. — A, piece of elater of M. ^ofyjfiorpka (magnified). ^', a por- tion more highly magnified. B, pitted cell of thallus. C, D, rhizoids %vith internal thickenines. (Radd.), Reboulia (Radd.), Fimbriaria (X. ab E.), Dumortiera (X. E.), Plagiochasma (L. &: L.), Preissia (Cord.), Lunularia (Mich.). ab 172 MUSCINEyE Literature. Mirbel — Mem. Acad. Sc. , xii., 1835. Strasburger — Pringsheim's Jahrb. wiss, Bot., 1870, p. 409. Vogt— Bot. Zeit., 1879, pp. 729 and 745. Goebel— Arb. Bot. Inst. Wiirzburg, 1S80, p. 529. Leitgeb— Sitzber. Akad. Wiss. Wien, 18S0, pp. 40 and 123; and Die Marchantieen, 1881. Prescher — (jNIucilage-receptacles) Sitzber. Akad. Wiss. Wien, 1882. Mattirolo — (Hygroscopic Properties) Malpighia, ii. 18S8, p. 181. FOSSIL MUSCINE.^. No remains have been found earlier than the Tertiary formations which appear to belong to Muscine?e. Here and in the Quaternary beds remains or impressions occur which have been referred to various families of Musci and Hepaticse, including leaves of a single species of Sphagnum and a single moss- capsule. The leaves of Jungermanniaceae are not uncommonly found enclosed in amber. 173 THIRD SUBDIVISION AND CLASS IX. CHARACEyE. The true position of this small group in a natural system of classifi- cation has been a subject of much controversy. By some writers of high authority it is regarded as occupying the highest place among green Algge. On the other hand, although without any lignification of their tissue, the Charace^e display, in the structure of their vegetative organs, a distinctly higher type of structure than the Thallophytes, in the distinct differentiation of the plant into a primary axis or stem, and secondary axes or branches ; but the branches are similar in structure to the primary stem. They are, in fact, Cormophytes rather than Thallophytes ; and it seems best to retain them as a distinct subdivision intermediate between the Muscinese and the highest Algge. The plant is acrogenous, growing by means of an apical cell contained in an apical bud ; the main stem has indefinite apical growth, the branches increasing by definite apical growth. The branches and the organs of sexual reproduction grow in the axils of other lateral organs of more simple structure, which are usually termed leaves ; those that subtend the reproductive organs being by some writers described as bracts or bracteoles. In all the Characeae these appendicular organs spring in whorls from well-defined nodes of the primary stem, imparting the pecu- liar habit to the plants by which they are distinguished from nearly all other Cryptogams. Each internode consists, in the Nitelleae, of a single very large cell extending along its whole length, and many times longer than broad. In the majority of the Chareae this internodal cell is invested by a layer of similar elongated cells of much snialler diameter arranged spirally round it, collectively known as the cortex, and giving the stem the appearance of being spirally striated. Each node consists, in the corticated species, of a single layer or plate of small cells from which the cortex is derived. From the nodes spring the whorls of branches and their subtending leaves. The branches are altogether similar in structure to the primary axis. The leaves have also, in the Chareae, a simple cortical layer, with the exception of the apex, where 174 CHA RACEME \ the large terminal cell is exposed. In addition to the leaves there spring, from the basal nodes of some species of Chara (L.), other leaf- like structures known as stipules^ one, two, or three in connection with each leaf. The stipular cells are always undivided by septa, and arise as papillae on the cortical cells. The cortex of the stem and branches is de- veloped out of the nodal plate of cells ; the upward and downward prolongations from the nodes usually meeting about the middle of each internode, where they dovetail into one another. These cortical internodal cells do not, however, like the axial cells, remain entire ; they divide, both transversely and longitudinally, into three parallel rows of cells, the central row of each series being somewhat elevated into a ridge. The mode and extent of development of the cortical cells vary according to the species. The number of leaves in a whorl is usually from four to ten. At the lower part of the main stem the internodes are shorter, and from the nodes spring rhizoids or rooting filaments which serve to fix the plant in the soil, con- sisting of long hyaline nearly undi- vided tubes, which grow obliquely downwards, and lengthen only at their apex. The rhizoids are always trichomic, springing from superficial cells. The nearly hemispherical apical cell of the terminal bud of the stem first divides by a trans- verse wall into a new. apical cell and a disc-shaped segment-cell. Each segment then again divides by a wall parallel to the first ; the lowest of these does not again divide, but develops into the axial internodal cell, while the upper one undergoes vertical division, and be- comes a node. Each successive whorl on the main stem alternates with those immediately above and below it, so that the oldest leaves of a :-^/i v^l^ Fig. i6o. — Chara fragilis Desv. (natural size). Fig. i6i. — Fertile branch of C./zzV- pida L. (mag- nified). CHARACEjE /3 whorl, which subtend the branches, are arranged in a spiral line running- round the stem; but this is not the case with the branches or secondary axes, where the members of contiguous whorls are superposed. The CharaccEe exhibit in an especially clear and beautiful manner the phenomenon oi cydosis, or rotation of the protoplasm (see fig. 163). The best objects for observation are the large internodal cells of Nitella (Ag.), the apical cells in the leaves of Chara, or some of those belonging to the reproductive organs, especially to the ' manubria.' The cell first of all develops vacuoles in its protoplasm, which coalesce into a single 4£k^ Fig. 162. — Longitudinal section through bud of C.fragilis, showing apical cell, t, and segments, g, b. A, cells empty. B, with cell-contents, granular protoplasm, chlorophyll-grains, and vacuoles. C, with cell-contents contracted by iodine ( X 500). (After Sachs.) large sap-cavity. The outermost thin parietal layer of protoplasm, in which are imbedded most of the grains of chlorophyll, remains motion- less; within this motionless lining is a thick layer of protoplasm, in which a regular current gradually sets up, up one side of the cell and down the other; the boundary between the two currents being marked by hyaline bands entirely destitute of chlorophyll, the neutral zones, in which no movement is visible. The direction of the rotating movement in each cell stands in a definite relation to that of all the other cells of the plant. From time to time the movement ceases, and then begins again in the oppo- site direction. Before the rotation commences the cell-nucleus has 176 CHARACE^ usually broken up into a number of fragments. The current is most rapid next to the stationary parietal layer, and becomes gradually slower towards the interior. As the cell grows the rotating protoplasm becomes differentiated into a watery and a less watery denser portion, the former having the appearance of a hyaline cell-sap, in which the latter floats in the form of larger or smaller roundish lumps. Since these denser bodies are passively swept along by the clear rotating protoplasm, the appear- ance is presented as if the cell-sap caused the rotation. Together with the denser lumps of protoplasm of less regular form, there are also a number of globular masses carried along in the current, which are covered with delicate protoplasmic spines or cilia ; their nature and function are involved in obscurity. Owing to the large size of the cells and the distinct differentiation of the nucleus, the internodal cells of the main axis of Chara and Nitella, as well as the apical cells of the leaves, have been largely used for fol- lowing the complicated processes connected with cell-division and the division of the nucleus. Schmitz describes the process as one of 'direct division of the nucleus,' Treub and Strasburger as one of 'fragmenta- tion ; ' Johow differs in some respects from all previous observers ; Cagnieul (Bull. Soc. Bot. France, 1884, p. 211) finds the process espe- ciallv easv to follow in the mother-cells of the antherozoids. Schaar- Schmidt (Bot. Centralblatt, vol. xxii., 1885, p. i) describes peculiar cell- wall thickenings and grains of 'cellulin' in Chara hispida (L.). The Charace^ do not produce spores, i.e. single non -sexual pro- pagative cells ; but are multiplied non-sexually in three different ways, the nodes being always the place of origin of the propagative cells, (i) Chiefly in Lychnothamnus stelliger (A.Br.), but also in C. hispida, C. aspera (Willd.), and Lamprothamnus alopecuroides (A.Br.), structures called (5?///>'/7i" or 'amylum-stars' are formed, agglomerations of cells deve- loped round the larger internodal cells at the level of the nodes ; they are of beautiful regularity, and are densely filled ^vith starch and other food- materials. On germinating they appear to produce at first other bulbils, and from these a new plant. (2) Chara fragilis and other species produce, on old hibernating or on cut nodes, in the axils of the leaves, peculiar branches known as gynmopodal shoots., which differ from the ordinary branches in the partial or entire absence of the cortex in the lowest internode and in the first whorl of leaves. The cortical branches which descend from the first node become detached, bend upwards, and pro- pagate themselves. (3) Also on C. fragilis, Pringsheim describes the occurrence of 'pro-embryonic,' or more properly oi prothalloid branches. These also spring from the nodes of the main axis, but differ essentially from the ordinary branches, presenting a similar structure to the pro- CHAR AC E^ 177 thallium or 'pro-embryo ' which proceeds from the germinating oosperm. No mode of vegetative propagation is known in the other genera. The sexual reproductive organs of the Characeae, the male antherids and the female archegones, are visible to the naked eye as minute orange- red globes and elliptical green bodies springing from the nodes in the axils of leaves or bracts. The antherids are glo- bular bodies, of a bright red colour when mature, from ^ to I mm. in dia- meter, morphologically the terminal cell of a leaf or lateral leaflet. The moderately thick wall of the antherid is made up of eight flat disc-shaped cells called shields, four of which, situated round the distal pole of the l)all. are tri- angular, while the four situated round the base are four-sided. On their inner face there lies a layer of chlorophyll- grains, which eventuallv turn red, while the outer face is clear and trans- parent ; the walls of these cells are folded in- wards at the edge where they meet. From the centre of the inner face of each shield a cylin- drical cell, termed a handle or inaniibrhun, projects inwards nearly to the centre of the globe. The antherid is supported on a short flask-shaped /^'^/V^/-*:^//, which also projects into the interior between the four lower four-sided shields. At the free end of each of the eight manubria is a roundish hyaline cell, the head-cell or capitidum. These twenty-five cells— viz. the eight shields, eight manubria, eight capitula, and the pedicel-cell — constitute the Fig. ibi. — Nitella Jlexilis Ag. A, nearly- ripe antherid sub- tended by two bracts showing direction of protoplasm-cunents, and neutral zone. i. ^, manubrium, with capitulum, secondary capitula, and whip-like filaments. C — F, antheiidial filaments, showing formation of antherozoids. G, antherozoids (C— 6^ x 550). (After Sachs.) 178 CHARACE^ framewoik of the antherid. Each capitulum bears six smaller cells, or secondary capiiula ; and from each of these grow four long whip- shaped filaments, bent into a number of coils and filling up the interior of the globe. The manubrium, capitulum, secondary capitula, and whip-shaped filaments, bear a resemblance to a many-thonged whip. The number of these filaments in an antherid amounts to nearly 200, and each filament is divided by transverse septa into from 100 to 200 small disc-shaped cells. The protoplasm in each of these antheridial cells becomes gradually transformed into an antherozoid strongly re- sembling the corresponding organ in xVIuscineae rather than in Thallo- FiG. 164. — A. portion of branch o\ C . fragilis ; a, antherid ; 6", archegone ; c, crown; ^', j3", bracts ( X 50). B, a young antherid ; ^"A", young archegone ( x 350). 'After Sachs.) phytes. It is a slender thread of protoplasm coiled spirally like a cork- screw, somewhat thickened at the posterior end, and bearing at its pointed anterior end two long fine cilia. The number of antherozoids in an antherid is, as will be seen, from 20,000 to 40,000. When ripe, the eight shields fall apart, and the antherozoids escape from their mother-cells, and move about rapidly in the water by means of their vibratile cilia. This appears generally to take place in the morning, the antherozoids swarming about for some hours till the evening. CHARACE.-E 179 The Charace^e are either moncecious or dioecious. In the former case the male and female organs are formed in close juxtaposition on the same node, the archegone being somewhat below the antherid in Xitella, above it or by its side in Chara. The archegones, like the antherids, are metamorphosed leaves. When ready for fertilisation, the archegone has a longer or shorter ovoid form, and is borne on a short pedicel-cell. In the interior is an axial row of cells enveloped by five tubes, which are at first straight, but are afterwards coiled spirally round the axial row. The lowest portion of each of these tubes is an elongated unsegmented cell; while at the upper part one or two very small cells are segmented off. In Xitella each of the terminal cells again di- vides into two by a vertical septum. The five terminal cells of Chara and the ten terminal cells of Nitella are not twisted, and form together the crown. When the archegone is ready for impregnation these crown- cells separate from one another, forming the neck., and leaving an open passage down to the axial row. This apical cavity is, how- ever, verv nearlv closed below by a diaphragm formed by the projecting inwards of the five neck-cells, through which there is only a very narrow opening for the entrance of the anther- ozoids. The apical cell of the axial row is much larger than the rest, and is the female or germ-cell, corresponding to the central cell in the archegone of the higher Cryptogams. It is filled with protoplasm, oil-drops, and starch-grains; its apical portion, the apical papilla, or receptive spot, containing only hyaline protoplasm. Between the apical cell and the pedicel-cell of the archegone, there is in Chara only a single cell, in Nitella a group of cells, the ' Wendungszellen.' Before fertilisation the crown is a compact s.tructure covering the apical cavity ; but when the archegone is ready for impregnation a small aperture is formed in its N 2 Fig. 165. — A, fertile branch ot Xitella Jlexilis (natural sLze) ; i, internode ; b, branches. B, upper portion of fertile leaf, b ; K, node ; nb, bracts ; 6", young archegone. C, older leaf with two bracts ; rt, antherid ; S, spermocarp. D, half-mature sper- mocarp (highly magnified). (After Sachs.) i8o CHARACE/E centre, through which the antherozoids force their way, and finally enter the apical cell by the deliquescence of the upper portion of its cell-wall, and coalesce with the apical papilla. The whole contents of the apical cell may be regarded as the oosphere. Impregnation causes at first very little external change in the structure of the female organ. The protoplasm of the oosphere, now invested with a cell-wall and transformed into an oosperm^ gives place to starchy or oily matter ; the walls of the enveloping tubes which lie next it in- crease in thickness and hardness, and the oosperm thus becomes invested in a hard black shell or pericarp. The structure thus formed, the so- called ' fruit ' or sper??wcarp of the Characeae ultimately becomes de- tached, falls into the mud at the bottom of the water, and there germinates in the next spring. When the spermocarp germinates, the oosperm first divides inta Fig. 167. — Calcareous spermocarp of C. hispida (magnified). Fig. 166. — A-D, stages in development of archegone o{ K.Jlexilis. b, apex of fertile leaf; x, ' Wendungszellen ; ' K, crown (x 300). (After Sachs.) three cells, a large basal and two apical cells, the former apparently serving the purpose of supplying with nutriment the young plant which proceeds from the latter ; and these three cells may be said together to constitute the embryo. From one of the two apical cells proceeds a long hyaline unseptated filament, commonly called the primary root, by means of which the young plant is attached to the soil. The other of the two apical cells develops into a hypha-like filament, consisting at first of a single row of cells with limited apical growth, and called by some writers the 'pro-embryo,' or more correctly \\\q prothalliiun. In this prothallium are developed two primary 7iodes at considerable distance from one another, and separated by a very long internode. From the lower of these two primary nodes there springs a whorl of rhizoids, which soon CHARACE.E i8i usurp the functions of the primary root. The upper of the two nodes is still at some distance from the apex of the prothalHum, this apical portion above the upper node consisting of a few much shorter cells. From this upper node is developed the new plant. It is divided by longitudinal septa into two inner and six or eight peripheral cells. The peripheral cells ultimately become rudimentary leaves, which do not, however, form a true whorl. In the midst of them appears a bud, or growing point, developed from one of the inner cells, from which springs the new stem, in a direction nearly at right angles to that of the prothallium. At present the formation of the prothallium has been observed only in the genus Chara. A remarkable instance of parthenogenesis has been recorded in Chara crinita (Wallr.). The species is dioecious, and male plants are extremely rare. On the female plants the oospheres develop into oosperms without apparently any possibility of their having been impregnated ; and the spermo- carps thus formed germinate in the ordinary way. The Characeae consist of only a compara- tively small number of species, but some of them very abundant, growing submerged in deep or in shallow, in stagnant or in running, or occasionally in brackish water. Several species are grown with great facility in fresh-water aquaria, where they multiply very rapidly. The presence of certain species may be detected by the fcetid odour of sulphuretted hydrogen given off when decaying. Phipson (Compt. Rend., Ixxxiv., 1879, pp. 316, 1078) attributes this odour to the presence of a special substance which he calls characin. The typical genus Chara is distinguished by its power of extracting calcium carbonate from the water in which it grows, the whole plant becoming thus covered with a calcareous incrustation, which frequently renders it difficult to make out the structure. Hence the family has acquired the popular names of 'brittle- worts' and 'stoneworts.' Nitella translucens (Ag.) sometimes forms enormous mat-like masses at the bottom of ponds. The systematic position of the Characeas has been a matter of much Fig. 168. — Germination of C. fragilis. sp, spermocarp ; «'', first root ; i, first inter- node of prothallium ; d, first node ; iv" , rhizoids ; q, second elongated inter- node ot prothallium ; g, second node with first whorl of leaves ; j>l, apical por- tion of prothallium (x 4). (After Pringsheim.) 1 82 CHAR ACE /E controversy. In habit and in general appearance they resemble the Algae, among which they are placed by the majority of writers. But in some important points of structure they differ so widely from all known families of Algje, that a true estimate of their relationships appears to require their location in a distinct subdivision by themselves. With the exception of the Fucaceae and the Conjugatae, the Characeae stand alone among the larger groups of Cryptogams in the entire absence of true spores. Seeing that the oosperm germinates directly in the soil, the embryo which results from its first divisions developing directly into the new plant, there is no 'alternation of generations ' in any accurate sense of the term. From those classes where a true alternation of generations attains its fullest development, the Muscineae and Vascular Cryptogams, the Characeae differ in the complete suppression of the sporophyte- generation ; while Phanerogams (at all events those Angiosperms which are destitute of endosperm) deviate, on the other hand, in the suppres- sion of the oophyte-generation. In the investment of the oosperm with a lignified pericarp directly without any previous breaking up into carpospores, the Characeae again differ essentially from all classes of Algae. The Characeae are divided into two orders, viz. — • 1. Chares. — Stem and branches usually corticated and calcareous; leaves usually with one or two stipules at their base ; antherids usually solitary on each node; crown always five-celled; pericarp often cal- careous. Geiiera : Chara (L.), Lamprothamnus (A. Br.), Lychnothamnus (Leon.). 2. NiTELLE.t. — Stem and branches not corticated nor calcareous; leaves without stipules ; archegones often clustered ; crown always ten- celled; pericarp not calcareous. Genera: Nitella (Ag.), Tolypella (A. Br.). Literature. Goppert and Cohn — Bot. Zeit. , 1849, pp. 665 et seq. Braun— Monber. Berlin Akad. Wiss., 1852, p. 220 ; and 1853, p. 45 ; and (Partheno- genesis) Abhandl. Berl. Akad. Wiss., 1856, p. 337. Thuret — Ann. Sc. Nat., xvi., 1 851, p. 18. Montagne— Ann. Sc. Nat., xviii., 1852, p. 65. Nageli — Beitrage zur wiss. Bot., ii. , i860, p. 61. Pringsheim — Jahrb. wiss. Bot., 1863, p. 294. Braun — Conspectus systematicus Characearum europoearum, 1867 ; and Abhandl. Berlin Akad. Wiss., 1882. De Bary — Monber. Berlin Akad. Wiss., 1871, p. 227 ; and Bot. Zeit., 1875, pp. 377 et seq. Bennett — Journ. of Bot., 1878, p. 202. Groves — Journ. of Bot., 1880, p. 97. CHARACE^ 183 Miiller— Bull. Soc. Bot. Geneve, 1881. Johovv — Bot. Zeit., 1881, pp. J2() et seq. Nordstedt— Hedwigia, 1888, p. 181. Allen — Characece of America, 1888. FOSSIL CHARACE.^. In various strata, commencing with the Cretaceous, remains known as gyroliths are found, sometimes in great abundance, which appear to be the petrified pericarp of the spermocarp of Charace^e. Upwards of forty species have been described, some of them closely resembling existing forms. 1 84 ALG.'E FOURTH SUBDIVISION. ALG^. The degree of affinity between the small group of Characeae and the very large group of Algae is, as has already been mentioned, a point on which the best authorities are not agreed. But, in passing from one to the other, we finally cross the line which separates the Cormo- phytes from the Thallophytes. From this point we have to do exclu- sively with plants whose vegetative organs are in no sense differentiated into axial and appendicular, and which further contain no true vessels and no woody tissue. On their lower limit there is no sharp line of demarcation between the Algae and the chlorophyllous Protophyta, but the consideration of Algse as a group by themselves, distinct from Fungi, we regard not only as convenient, but as also most in accordance with their probable affinities. Within the limits above mentioned, the degree of complexity in the structure of Algae is very various, and the different types will be best described under the separate families. In their vegetative structure we may recognise three types : the elaboration in the development of a single cell, the loose association of cells into a family or coenobe, and the close aggregation of cells into a filament or a thallus. To the latter belong all the higher families, and in some of these we see indications of the various kinds of tissue found in vascular plants. The higher forms, consisting of a well-developed thallus of large size, in which the cells are associated with one another in all three directions, are almost exclusively marine, and include the whole of the organisms popularly known as seaweeds. In the larger forms the plant is attached to the substratum — a rock, stone, or other large alga — by a root-like organ of attachment known as the disc. The attachment is, however, always superficial, and the organ takes no part in the absorption of nourish- ment for the plant. The organ may result from the repeated division of a single cell, or it may be more complicated, being formed out of the termination of the downward growth of cortical rows of cells. In nearly all fresh-water Algs the single cell, the ccenobe, or the filament is en- ALG.-E 185 closed in a more or less strongly developed gelatinous sheath. The greater number of families exhibit both a sexual and a non-sexual mode of reproduction, though in some cases one or the other mode has not yet been detected. In the great majority of families the non-sexual propagating bodies are motile cells or zoospores^ minute masses of proto- plasm formed singly from the whole contents of a cell by rejuvenescence, or more often in large numbers by free-cell formation, destitute of a true cellulose membrane, but containing protoplasm and a contractile vacuole, and provided with two or sometimes a larger number (rarely only one) of vibratile cilia, by means of which they move about actively for a time, then come to rest, excrete a cellulose membrane, and de- velop into a new plant. In one class only, the Florideae, are the zoo- spores replaced by non-motile tetraspores ; in the Conjugatae and Fucaceae they are altogether wanting. The simplest form of sexual reproduction is that of co?ij ligation^ or the coalescence of two compara- tively undifferentiated masses of protoplasm. These masses of proto- plasm may be either the contents of stationary cells, which are nearly or quite alike, as in the Conjugatae, or they may be motile ciliated bodies indistinguishable from zoospores — zoogametes — or they may be -distinguished from the true zoospores by their smaller size. From the conjugation of zoogametes there is a gradual transition through intermediate stages to a true sexual process, the impregnation of a stationary oosphere by a motile antherozoid, usually much smaller than the oosphere, the result being the production of an oosperm by the encysting of the oosphere in a coat of cellulose. In the higher families the oospheres and antherozoids are formed in special cells or organs, known as oogones and antherids respectively. In the Florideae the process displays very great complication ; the structure in which the ■oosphere is formed is known as the carpogo?ie ; the fertilised oosphere is the carposper?n, which often breaks up into carpospores. In this class also the antherozoids are replaced by motionless protoplasmic bodies k:nown 2.'s> pollinoids. Multiplication by the simpleyfi-j-/(?/2 of individuals, by the detachment of gevimce, or buds, and by the encysting of special ■cells or masses of cells into cysts ^ also occur. In the green Alg^e (Confervoideae heterogamae and isogamce and ConjugatJe) single non- motile cells which become detached for the purpose of propagation are termed by AMlle akifietes when they are formed without rejuvenescence, aplanospores when formed by rejuvenescence. The former occur in Trentepohlia (Mart.), Conferva (L.), and Ulothrix (Ktz.), as well as in the Nostocaceae and Rivulariacese, the latter in the Confervaceae. The two kinds pass into one another, and akinetes into vegetative cells, by in- sensible gradations. 1 86 ALGyE Any classification of Algae which attempts to follow the lines of affinity- in other words, any natural system of classification — must be based on a consideration of both the vegetative and the reproductive organs. All the families of Algse appear undoubtedly to have sprung from the PROTOCOCCOiDEyE, and their further development has taken place in three directions — the perfection and differentiation of the in- dividual cell, the association of cells into coenobes, and cell-division. The production of coenobes may be supposed to start from such formji as Botryococcus among Protococcacece ; the first step in the develop- ment of the CoENOBiyE being the Sorastrece, including Sorastrum, Coelastrum, and Selenastrum, motile colonies of non-ciliated cells, with no known production of zoospores. The series attains a much higher development in the FandorinecE^ including Pandorina, Gonium, and Stephanosphcera, where reproduction is effected by the conjugation of zoogametes. Simple organisms like Chlamydomonas and Chlamydo- coccus, consisting merely of conjugating zoogametes, are possibly retro- gressions from the higher forms, though they may also be stages in a direct ascent from Protococcus. Eudorina, with a rudimentary differ- entiation of antherozoids and oospheres, unquestionably indicates the line of development of Volvox, in which this differentiation is more strongly developed. In Volvox we have the culmination of the attempt of nature to evolve higher organisms out of coenobes. Hydrodictyon is probably an aberrant member of this group, and ihe. Pediastrere are more or less nearlv related to them. From the Eretiwbice the fuller development of the individual cell has advanced a further stage in the Multinucleate, composed of the SiphoiiodadacecE and Siphonece, and characterised by each individual consisting of an enormously developed cell, often ramifying greatly and attaining gigantic dimensions, and possessing several, often a very con- siderable number, of nuclei. In the Siphonocladacese the only known mode of reproduction is by the conjugation of zoogametes ; and Botrydium displays a distinct affinity with Botrydina among the Eremobise. The Siphoneae or Coeloblastse, represented by Vaucheria, are a higher development of the same series, in which true sexual organs, oogones and antherids, are formed in addition to non-sexual zoospores ; and in this genus culminates the striving after a higher development in the elaboration of a single cell. A rudimentary cell-division is exhibited in the Nostochi7tece among Protophytes, but accompanied by other conditions which prevented its full success there. Where cell-division originated in the Protococcoideae is not clear, probably in the Eremobias ; we find it already fully developed in the Confervoide.^ isogam.^, the members of which consist of a ALG^ 187 single unbranched or branched filament of cells, the only known modes of multiplication being the conjugation of zoogametes and the direct ger- mination of larger zoospores. In the lowest two classes, the Chroolepidece and UIofrichacecF, embracing a very small number of genera, the filament is usually unbranched : in the two higher, the Confervacece and Pitho- phoracece^ further vegetative activit}- is displayed in the copious branching : and in the former we have an indication of afhnitv with the Multi- nucleatae in an occasional plurality of nuclei. The exact course of evolution from the isogamous Confervoidese is obscure, but it would appear to have taken place in three distinct lines. The first of these, which evidently came to an abrupt conclusion, is the CoNjUGAT.E, consisting of the Zygnemacece, Mesocarpece. and Desmidiece^ a well-marked and sharply differentiated group with no near affinities. The first two orders, consisting of unbranched filamentous forms, are probably derived directly from the Confervoide^, although the change in the mode of reproduction is very abrupt. The production of zoospores is entirely suppressed, and they are reproduced solely by the conjuga- tion of cells belonging to the same or to different individuals. The Desmidiese must then be regarded as a group adapted, by a certain amount of retrogression in both vegetative and reproductive characters, to life in shallow water ; and derived, through such filamentous genera as Desmidium and Hvalotheca, from Zvsrnemacese with lateral con- jugation. By some writers the Diatomaceae are associated with the Desmidiese ; our reasons for placing them among the Protophyta will be given hereafter. The mode of reproduction by conjugation attains its climax in the Mesocarpe^. The second line of descent is that of the brown seaweeds. In the Ph.eospore.^ we have every shade of transition in the mode of repro- duction from isogamous to heterogamous. The typical Phaeosporeae, such as Punctaria and Ectocarpus, are characterised by the possession of two kinds of zoosporange, unilocular and multilocular. The zoospores produced in these two kinds of zoosporange present no difference in size or form ; but those from the unilocular sporanges appear in all cases to germinate directly, while those produced in the multilocular sporanges are sometimes zoogametes with sexual functions. In some families one or the other kind of zoosporange is suppressed. In the Ectocarpacece and some other genera we have a mode of reproduction closely resembling that in the isogamous Confervoideae, except in the greater differentiation of the cells which become zoosporanges, a conjugation of zoogametes which are to all appearance exactly alike, though a slight differentiation is exhibited in the fact of one of them coming to rest and partially losing its cilia before conjugation takes place. In the Ciitkriacece the differ- i88 ALGAL entiation is more complete ; the male and female swarm-cells are pro- duced either on the same or on different individuals ; the female are much larger than the male, and come perfectly to rest, entirely losing their cilia before being impregnated by the former. In the Diciyotaceie the differentiation is carried still further, and the female reproductive bodies are from the first motionless oospheres not provided with cilia. Several families of Phasosporeas exhibit reduction or degradation of the vegetative structure ; and among these we are disposed to place the small group of Syngeneticce, consisting of but two genera, Hydrurus and Chromophyton, which resemble one another in but few^ points except the possession of a brown endochrome. In the former genus the pro- pagative bodies are reduced to non-ciliated masses of brown protoplasm, which germinate directly without impregnation ; in the latter the vegeta- tive structure is almost entirely suppressed ; the propagative bodies are uniciliated masses of protoplasm of two kinds, but without any observed process of conjugation. The step from the Dictyotaceae to the Fucace^ is an easy one. In the highest type of brown seaweeds, such as Fucus or Durvillsea, with their typical heterogamous or ' oogamous ' reproduction, consisting in the impregnation of a comparatively large oosphere by a number of minute antherozoids, we have the highest attainment of this series of development. The third line of descent from isogamous Confervoideae is a much more direct one, to the CoxFERVOiDEyE HEXEROGAMiE, including the three orders Sphceropleacece, CEdogoniacece, and Coleochcetacece. In the first of these, which comprises only a single species, we have a distinct differentiation of the male and female reproductive cells, the latter having now become permanently quiescent ; but still a strong reminiscence of the Confervacese in the multinucleated cells. The CEdogoniaceae exhibit a distinct advance in vegetative structure, and still more in the cells which contain the male and female reproductive bodies being, for the first time in this series, differentiated into antherids and oogones respectively. Between the CEdogoniaceae and the Coleochaetaceae we have an evident connecting link in Bulbochaete ; but the typical genus Coleochste presents a singular reduction of the non-reproductive portion of the thallus from a filament to a single plate of cells. The mode of sexual reproduction has now attained a much higher degree of complexity. The oogone is surmounted by a tubular appendage, the trichogyne, through which the motile antherozoids find their way to the oosphere in order to impregnate it. The fertilised carpogone, as it is now called, then becomes invested by a cortical layer of ccils, forming the complex body known as the sporocarp. The Coleochaetaceae lead up directly to the highest type of structure attained by Algae, the Floride.e or red seaweeds, a well-defined and ALG.-E 189 natural group, though exhibiting remarkable variety in the degree of development of the sexual organs. So striking is the resemblance in the mode of impregnation in the most highly developed genera of Floridese, such as Callithamnion, Dudresnaya, or Corallina, to that in Coleochgete, that it is scarcely possible to doubt the direct descent of one from the other ; the chief difference is in the replacement of motile antherozoids by pollinoids which have no active power of motion. The process of fertilisation is the most intricate which occurs among Thallo- phytes, and presents a remarkable forecast, so to speak, of the mode afterwards elaborated in Flowering Plants, though only after a very long interval, comprising the entire evolution of the Muscinese and Vascular Cryptogams. With the loss of motility of the male reproductive cells is also correlated a corresponding loss of motility of the non-sexual reproductive cells or tetraspores. In the higher families of the Florideae we have also the highest development of the organs of assimilation found among Thallophytes. If the view is correct that the higher Florideae are derived directly from the Coleochgetaceae, it follows that we must regard all the less highly developed famihes of this group as retrogres- sions from the parent type ; and this view appears to offer the most probable explanation of the true position of some aberrant forms. In the Helminthocladiace(^ and Squamariacece the degeneration is exhibited solely in the less perfect development of their thallus or vegetative structure. In the Lejnaneacece this is accompanied also bv a simpler structure of the sexual organs. But here, as well as in Batrachospermum, we have the first rudimentary appearance of a phenomenon resembling that known as 'alternation of generations,' which plays so important a part in the Vascular Cryptogams, and which may possibly indicate the genesis of the Muscineae. In the Porphyracece. we find a reduction of the thallus to a simple filament or plate of cells, accompanied by only a rudi- mentary development of both carpogones and trichogynes, and a limited reversion to motility in the tetraspores. Regarding the Porphyraceae as exhibiting retrogression from the more complicated Floride^, rather than as the lowest member of an ascending series, it is difficult to resist the conclusion that the UlvacecB are derived from the Porphyraceae b}" further retrogression, displayed in the entire suppression of antherids and oogones, and a reversion to the primitive conjugation of zoogametes. In their vegetative structure the Ulvaceae differ widely from the isogamous Confervoidese, with which they are usually associated, while the close resemblance between Ulva and Porphyra is obvious. In the Florideae- the Algce attain their highest type of development. By far the larger number of Algae grow entirely immersed in water^ running or stagnant, fresh, brackish, or salt ; some float on the surface without any attachment ; others are found on moist soil, among moss. iQo ALG.E &:c. The whole of the marine vegetation of the globe, with the excep- tion of a very small number of species of Flowering Plants, belongs either to the Algae or to the chlorophyllous Protophytes. I'hey vary in size from the microscopic Desmidieae and Pediastreae to that of shrubs or trees in the case especially of some genera of Laminariaceae and Fucaceae ; and in these classes, as well as in the Florideae, we find a rudimentary differentiation, not only of tissues, but of organs, which leads the way to the much more complete development in the higher classes of the vegetable kingdom. Fresh-water Algae are, with very few exceptions (species of Bangia, Hildenbrandtia, Lithoderma, Hydrurus, &c.), green. Among marine Algae there are many genera of green sea- weeds, belonging chiefly to the families Confervaceae, Siphonocladaceae, and Ulvaceas ; but these mostly grow in shallow water. As regards all organisms growing in deep seas, it appears to be essential to them that the green colour of the chorophyll should be masked by a coloured pigment, red in the case of the Floride^, brown in those of the Phceosporeae and Fucaceae ; the nature of these pigments will be dis- cussed under the separate families. A few of the smaller species, belonging to the Coleochaetaceae, Chordariaceae, and Squamariaceae, grow attached to stones, larger Alg^e, or other marine objects, as flat ■discs, gelatinous cushions, or calcareous incrustations, and the deposition of lime takes place to a much larger extent in the corallines. The propor- tion of ash to the organic constituents is much larger in marine than in land or fresh-water plants, seaweeds having the power of extracting from the salt water large quantities of the soluble salts contained in it. The larger species of Fucaceae and Laminariaceae are largely used in the north of Europe for manuring the land and for foddering cattle ; and in former times the manufacture from their ashes of kelp and barilla was an important industry. They are also an important commercial source of iodine. From the quantity of gelatine contained in their thallus, some species of Ulvaceae, Porphyraceae, Fucaceae, and Laminariaceae are also occasionally used as articles of food or for medicinal purposes. Literature. Greville — Algae, in Scottish Cryptogamic Flora, 1823-28 ; Algae Britannicas, 1830. Kiitzing — Phycologia generalis, 1843 ; Tabulae Phycologicre, 1845-69 ; and Species Algarum, 1849. Harvey — Phycologia Britannica, 1846-51 ; Nereis Australis, 1847-49 ; British Marine Algae, 1849; Nereis Boreali- Americana, 1851-58; Phycologia Australica, 1858-63. Hassall — British tresh-water Algte, 1S45. Nageli — Die neuern Algensysteme, 1847. Agardh— Species, Genera, et Ordines Algarum, 1848-80 ; Till Algernes Systematik, 1872-87. Thuret— Antheridies des Cryptogames, 1851 ; Zoospores des Algues, 185 1 ; and Etudes Phycologiques, 1878. ALGjE 191 Landsborough - Popular Hist, of British Seaweeds, 1 85 1. Pringsheim — Ueber Befruchtung u. Keimung der Algen, 1855. Gray — British Seaweeds, 1867. Wood — Fresh-water Algje of North America, 1873. Bornet & Thuret — Notes Algologiques, 1876-80. Falkenberg — Die Algen, in Schenk's Handbuch der Botanik, vol. ii., 1881. Hauck — Die Meeresalgen, in Rabenhorst'sKryptogamen-Flora Deutschland, 1883-85. Schmitz — Die Chromatophoren der Algen, 1882 ; andjourn. Micr. Soc. , 1883, p. 405. Cooke — British Fresh-water Algje, 1884. Gay— Bull. Soc. Bot. France, 1886, Sess. Extraord., p. 21. Bennett— Journ. Linn. Soc, xxiv. , 1S87, p. 49. AVolle — Fresh-water Algse of the United States, 1887. Wille — (Resting-spores) Pringsheim \s Jahrb. wiss. Bot., 1887, p. 492. Stroemfelt — (Attachment-disc; Bot. Centralbl., xxxiii., 1888, pp. 381 & 395. Class X. — Florideae. This large family — known also as Rhodosporcce and Rhodospermeae — exhibits the highest type among Alg^ in the mode of sexual repro- duction, and also possibly in the development of the vegetative organs. It consists almost entirely of seaweeds, including all the red and purple kinds. A few species only, belonging to the genera Hildenbrandtia (Nard.), Batrachospermum (Bory), I.emanea (Bon,-), Bangia (Lyng.), and a few others, grow in fresh water. Some of these are green, but the great majority of the Floride^e are of a bright red colour, varying with purple, brown, yellowish, or dirty white. The 'fronds' do not attain nearly the size of those of the Fucaceje and Laminariaceas, but they are often of delicate texture and finely divided, rendering them the most beautiful of our seaweeds. The thallus varies within very wide limits in its degree of develop- ment. In a few genera, such as Callithamnion (Lyng.), it consists of distinct filaments of cells which are almost always branched ; in others, as Porphyra (Ag.), Plildenbrandtia, and Cruoria (Fr.), of a flat plate of cells, composed of only a single or of several layers ; in the fresh-water genus Batrachospermum, of an axis with beautifully regular whorls of branches ; while in most seaweeds it constitutes a massive parenchyma, or the filaments are held together by a more or less dense gelatinous envelope. Growth takes place, in the majority of cases, by means of a single apical cell, but this is often followed by a strong intercalary growth. The apical cell is not three-sided, as in Vascular Cr}'ptogams, but is either wedge-shaped, dividing by walls which incline alternately to the right and left, or it divides by nearly parallel walls. In some forms, however, especially the prostrate Melobesiaceae and Squamariace^, and 192 ALG.K in the Nemalieo2, the apical cell appears to be replaced by a group of equi- valent cells, ^^1lle distinguishes six types of Floride?e as respects their mode of growth ; in four of these groups growth takes place from a single apical cell ; in two from an apical mass of cells, with peripheral growth. In the so-called polysiphonous seaweeds, such as Polysiphonia (Grev.), a transverse sec- tion of the 'frond' shows a large central elongated cell, surrounded by four or more smaller cells, which are also elon- gated in the longitudi- nal direction, and which are known as siphons. These perice?itral tubes are often connected with one another and with the axial cell by threads of protoplasm. When the pericentral tubes are wanting the frond is monosiphonous. In some genera belonging to the Ceramiace^ either the single axial tube or both axial and pericentral tubes are surrounded by a pseudo-cortex formed of a dense agglo- meration of secondary branches originating at the nodes and closely adpressed to the pri- mary branch. These are always the result of further division of the pericentral tubes, the apical cell remaining undivided. In other genera a similar cortical tissue is composed of moniliform rows of cells arranged at right angles to the axis. Although there is in the Florideae no distinct differentiation of the Fig. 169. — Gigartina maviillosa Ag., with cystocarps (natural size). (After Luerssen.) FLO RID E^ 193 tissue into epidermal, assi- milating, and conducting systems, still there are, in the higher forms, cells which are especially concerned with assimilation, and which may be either isodiame- trical, or elongated in either direction. Such assimilat- ing tracts are classed by Wille under three heads, viz. : — (i) those which act also for purposes of con- ducting ; (2) those which are altogether distinct from the conducting cells ; and (3) those where, in addition to an assimilating, there are also primary and secondary conducting cells. In some species the 'frond' assumes the appearance of a stalked leaf, as in Hydrolapathum (Rupr.) and Delesseria (Grev.), often of the most beautiful form, and present- ing even a rudimentary venation. The genera Melobesia (Lmx.), Hilden- brandtia, Cruoria, and some others, consist of small algae, mostly marine, with crustaceous or gelatinous thallus, growing flat on stones or larger algae, often of lichen-like appearance. In their mode of growth some Florideae display bi- lateral symmetry, and the branching may be either monopodial or sympodial. In Polysiphonia, Spyridia Fig. 170. — Polysiphonia opaca Zan. a, with cj-stocarps ;. b, with tetrasporanges (natural size) ; c, branch with tetrasporanges ; d, branch with cj-stocarp ( x 100). (After Kiitzing.) 194 ALG.E (Harv.), and some others, the 'phyllotaxis' is spiral. The genera Ryti- phloea (Ag.), Vidalia (Lmx.), Amansia (Lmx.), and Polyzonia (Suhr) are distinguished by the endogenous formation of the normal lateral shoots. In Pollexfenia (Harv.) and allied genera, Falkenberg records a remarkable congenital union of all the branches of the thallus which lie in the same plane. The red colouring matter of the Floridese has been investigated by Rosanoff, Cramer, Askenasy, Sorby, and others. Cramer first extracted it, from Bornetia secundiflora (Ag.) and Callithamnion caudatum (Ag.), in the form of regular crystals, partly hexagonal, partly octohedral, and gave it the name rhodospen?iin. Rosanoff ex- tracted it by cold fresh water, and found it carmine- red in transmitted, reddish yellow, or rarely green, in reflected light. It is insoluble in alcohol. The chlorophyll-grains also exhibit fluorescence when left behind, if the pigment, tho: phyco-erythrin of Askenasy and Sorby, has escaped from them in consequence of injury to the plant. The spectrum of the chloro- phyll is nearly identical with that in Flowering Plants. The compound pigment of the red Algae is termed by Schiitt rhodophyll, the term phyco-erythrin being limited to the portion soluble in water, while the portion soluble in alcohol he calls Flo- ^ ridece-green. Cohn found, in Bornetia (Thur.), colourless crystalloids of an albu- minous substance coloured a beautiful red by the same pigment ; and Klein has found similar crystalloids in several Floridese. The chromatophores contain starch-grains, which differ both from the ordinary grains of Flowering Plants and from those of the brown Algae in being coloured brown or red by iodine. Schmitz (Sitzber. Niederrhein. Gesell., 1880) has detected a number of nuclei in the vegetative cells of many Floridese, but not in the reproductive cells. Hick (Proc. Brit. Ass., 1883; ' Nature,' vol. xxix., 1884, p. 581), Massee (I.e.), and Moore (Journ. Linn. Soc. Bot., vol. xxi., 1886, p. 595) find continuity of protoplasm from cell to cell very beautifully displayed in Callithamnion (Lyng.), Ptilota (Ag.), Polysiphonia, and several other genera, not only in the vegetative cells, but also in the tetrasporanges. In Corallina (L.), Melobesia, Liagora Fig. 171. — Hydrolapathiim sangui- neHt7i Stackh. a, two young fronds with two cj-stocarps ; b, c, prolifica- tions from the stem (natural size). (After Kiitzing.) FLORIDE.^ 195 (Lmx.), and a few other genera, the 'frond' becomes densely incrusted by a deposit of calcium carbonate, giving to the so-called 'corallines' the external form and appearance of miniature corals. The ordinary non-sexual propagative organs of the Floridese are bright red motionless spores, commonly formed in fours in the mother- cell, and hence known as tetraspores (the sphaerospores of Agardh), and the cell in which they are produced as a tetrasporange. The four spores are sometimes arranged in a row, when they are called zo?iate ; more often as quadrants of a sphere, when they are cruciate : rarely there are only one or two, or occasionally eight. In the Ulvaccce, Lemaneacese, Fig. T-]2..—Cro7cania attennata Ag. a, branch (x 40) ; h, apex of branch (x 100) ; c, lower portion of branch with tetrasporanges ( x 100). (After Kiitzing.) and in some Nemaliea^ they are altogether wanting. The tetraspores (see fig. 231) may be formed in the six following ways : — (i) The whole contents of the sporange become a single spore ; (2) the contents divide into two equal parts by a transverse wall ; (3) they divide into four quadrants by two successive bipartitions ; (4) they divide into four tetrahedra by simultaneous quadripartition ; (5) they divide into four by three parallel transverse walls ; (6) the contents divide into more than four spores. On germination the tetraspores may give birth either to sexual or to non-sexual individuals. In the monosiphonous Florideae the tetrasporanges are usually formed at the expense of the ultimate branchlets. In other forms they are most commonly found scattered o 2 196 ALG.'E near the margin of the ' frond,' sometimes (Rhodymenia bifida, Ktz.) im- bedded in the thallus, and then often grouped into sori. (Nitophyllum, Grev.) ; or, in the CoraUinaceae, enclosed in special coticeptacles. In other genera (Phyllophora, Grev., &:c.) they are developed in nematheces, wart-like elevations of the surface, where they are accompanied by barren h)ph£e or paraphyses. In others again they are borne on metamorphosed pod-like branches known as stichids, as in Dasya (Ag.), Plocamium (Lmx.), 6cc. Only in the Porphyraceae are the tetraspores endowed with a slow Fig. 173. — Xitophyllui7i pu7ictatia)i Harv. a, piece of frond with tetrasporanges (natural size) ; b, piece of the thallus with tetrasporanges (x 100); c, section through frond showing cystocarp(x 100,. (After Kiitzing.) amoeboid motion. Zoospores are altogether unknown in the class, except in the Ulvaceae ; but other modes of non-sexual propagation occur in a few cases. In some genera of Ceramiacese special organs occur, known as seirospores. Melobesia is characterised by the production oi ge7}wicE. In ]Monospora (Sol.) stalked gemmae or prop agules are produced at the forks of the branchlets, and readily become detached, apparently repla- cing the sexual organs, which are unknown in the genus. Lemanea (Bory) increases by budding. In Hydrolapathum peculiar bud-like prolifications are produced on the stem (see fig. 171). Fig. 174. — Dasya elegans Ag. a, piece of frond with tetrasporanges ; b, piece with cj-stocarp (natural size) ; c, branch with stichids ( x 100) ; d, cystocarp ( x 25). (After Kiitzing.) 198 ALG.E A true understanding of the sometimes complicated process of sexual reproduction in the Florideag has been much obscured by the numerous terms employed by the older writers for identical organs, and by incor- rect notions as to their functions. The true sexual organs, antherids and proca?'ps, are nearly always formed on individuals which do not produce tetraspores ; and the sexual individuals may be monoecious or dioecious ; the latter is the most common condition. If the Ulvaceae are rightly included under Floridese, we have here a wide departure from Fig. 175. — Stages in the development of the reproductive organs of Nentalion injiltifiduin Ag. (magnified). (Speniiat. — pollinoids.) the normal type, sexual reproduction taking place by the conjugation of motile swarm -cells. The a?itherid consists, in its simplest form (Porphyraceae), of a soli- tary cell at the end of a long segmented branch ; and in this case it gives birth to a single pollinoid ; in other forms the antheridial cells occupy a similar position to the tetraspores, being formed in groups at the expense of the ultimate branchlets. They are also sometimes pro- FLORIDE.-E 199 duced, like the tetraspores, in wart-like protuberances or neijiaiheces on the surface of the thallus, and interspersed with paraphyses, sometimes (Gracilaria, Grev.) in depressions which are overarched by the surround- ing tissue ; or. in the Corallinace^, in special conceptacles. When the thallus is otherwise unilamellar, as in Porphyra (Ag.), the spots where the antherids are formed divide by walls parallel to the surface. The fer- tilising bodies ox pollmoids are naked masses of protoplasm, of a spheri- cal or elongated form, sometimes with a beak-like appendage, and are discharged in succession one after another. They are carried along passively by the water, and are distinguished from the antherozoids of other Cryptogams by the absence of cilia, and, in most cases, of any spontaneous power of motion. Wright (Trans. Irish Acad., 1879, P- ^7) Fig. 176. — Sperviothamnion Jiennaphrodifuvi (magnified). A , branch with procarp {tyg i) and antherid {an) before fertilisation ; B, after fertilisation, the cystocarp developing ; t, trichogj-ne ; c, trichophore ; g, carpogenous cells. (After Nageli.) states that in Griffithsia (Ag.) the pollinoids have an obscure amoeboid motion, as they have also in the Porphyraceas ; according to Dodel-Port their access to the trichogyne is greatly facilitated by the currents made in the water by Vorticellse and other Infusoria ; and there can be little doubt that fishes which feed on seaweeds are an important agent in pro- moting their fertilisation. The pollinoids and the tetraspores appear to be homologous in their origin. The female organ before fertilisation — corresponding functionally to the pistil of Flowering Plants — is termed \hc procarp. In its simplest form (PorphyracejE and Xemalie^) it consists of a single cell with a lateral hair-like prolongation, the trichogyne. But in all the higher forms the procarp is composed of one or more fertile cells constituting the carpogone, and one or more infertile cells which make up the tricho- 20O ALG.-E phore, the function of which is to convey the fertihsing substance from the trichogyne to the carpogone. The procarp is usually formed on the youngest parts of the plant, and often originates from the terminal cell of a lateral branch. Occasionally each carpogone has two trichogynes and two trichophores ; or, again, each trichophore may be connected with two carpogones. U'he trichogyne often becomes eventually coiled ■^w-^- Fig. i-j-j. — LeJoHsia iiiediterranea Born, a, filament with tetrasporange ; b, plant with cystocarps and antherids ; c, empty cystocarp (x 150). (After Bornet.) spirally at its base. It does not open to admit the entrance of the pollinoids ; in the act of impregnation these bodies attach themselves to a spot near the apex of the trichogyne, and at the same time clothe themselves with a cell-wall. At the point of contact the cell-wall of both trichogyne and pollinoid is absorbed ; the contents of the latter pass through the trichogyne and the trichophore to the carpogone, impregnat- FLORIDE^ 20I ing its contents, and the trichogyne then disappears. The carpogone now divides by a horizontal wall into two cells ; the upper one of these is functionless, and ultimately disappears ; the lower one contains the impregnated oosphere or carposperm. The carposperm does not, how- ever, in any case possess the power of germinating directly. In the Porphyracese it breaks up into eight portions, the carpospores, which germinate after movmg about with a slow amoeboid mo- tion. In all the other orders the contents of the carpogone undergo, after impregnation, more complicated divisions, and become differentiated into a sterile and a fertile portion, the placenta and the nucleus. The placenta may consist of one or more cells, and frequently occu- pies the larger portion of the carpogone ; or it may be re- duced to very small dimensions. The nucleus is the mass of carpo- spores, and may be made up of a number of secondary iiuclei. The mass of carpospores is sometimes, as in Callithamnion, completely exposed except for a gelatinous membrane by which it is surrounded ; but much more often there is gradually formed round the nucleus after impregnation, not only a layer of mucilage, but also a more or less hard solid layer, the peri- carp; and the whole structure thus constituted is then known as the sporocarp or cystocarp. From this cystocarp the carpospores escape, when ripe, either by the decay of the pericarp (' coccidium ' of the older systematists). or through an opening at its apex, the carpostome (' ceramidium ' of older writers). In some genera (Polysiphonia, Lejolisia, Born., Bonnemaisonia, Ag.) the cystocarp is completely exposed, con- spicuous, and sometimes stalked ; but it is usually, as in Gracilaria, Fig. t-jZ. — Gracilaria coni^ressa A^. Branch with cystocarps (natural size). (After Hauck.) 202 ALGAi: more or less imbedded in the thallus, often in special fertile branches ; and its situation is then usually indicated by an external wart-like swelling. In Polyides (Ag.), the Squamariaceae, and other forms with a perfectly flat frond, the cystocarps are enclosed in nematheces. In a considerable number of Florideae the formation of the cystocarp is a more complicated process than that already described, the process of impregnation consisting of two distinct stages— (i) the fertilisation of the trichogyne by the pollinoids ; and (2) the fertilisation by the impregnated trichophore-cells of the carpospores, which may be at some considerable distance from the trichophore and trichogyne, even on a Fig. 179. — Dudresnaya coccinea Croua.n. 7, young trichophore. //, young trichogyne; y, young fertilising tubes. ///, impregnated trichophore with pollinoids on the coiled tricho- gyne.y; the fertilising tube, y, impregnating successively the carpogones, l^/I, F7, and ^'. IF', carpogone before fertilisation; c, carpogenous cell. VIII, masses of carpospores. different branch. This is effected by means of long simple or branched tubes, the fertilising-tiibes, or ' ooblastema-filaments ' of Schmitz. The following is the process as it takes place in Dudresnaya (Born.). The trichophore consists of a row of cells which, before fertilisation, put out short branches, ^^hich subsequently develop into long tubes. No carpo- gone is found in the immediate neighbourhood of the trichophore ; but at some distance are a number of short segmented filaments, the termi- nal cells of which are considerably larger than all the rest. These cells are carpogones. The fertilising-tubes make their way between the fila- ments or hyphte of which the thallus is composed, come into contact FLORIDE^ 203 with the carpogones, and convey to them the fertihsing principle from the trichophore. The result is that each carpogone develops into a cystocarp containing carpospores. A single fertilising-tube may in this way impregnate a number of carpogones. Schmitz describes the process of secondary impregnation in the more highly developed Florideae as consisting in the fertile cells (carpogones) entering into communication, through orifices in their cell-walls, with certain special sterile cells rich in protoplasm, the auxiliary cells ^ to which the fertilising material is brought from the trichophore by the ooblastema-filaments. The details of this conjugation between the auxiliary cells and the carpogones are subject to great variation in different genera. In some cases the protoplasmic contents of the two cells coalesce completely, while in others their nuclei still remain distinct after conjugation. The carposperm, or cell resulting from this conjuga- tion, then grows rapidly, and peripheral cells divide off from it, leaving a large central cell which alone remains sterile, all the peripheral cells developing into carpospores. In the Corallinaccce the ooblastema-fila- ment enters into conjugation successively with several neighbouring auxiliary cells. In a larger number of genera the process is as follows : — A short branch of the carpogone, usually consisting of three or four cells, becomes attached laterally to a branch of the thallus, and cur\-es in such a way that the carpogone-cell is closely applied to the nearest auxiliary cell, or reaches it by means of a short protuberance from one or both of the conjugating cells. The entire oosphere, or at all events its nucleus, then passes over into the auxiliary cell. In the Gigartinaceas the auxiliary cell itself becomes the central cell of the cvstocarp. Literature. Nageli u. Cramer — Pflanzenphj^siol. Untersuch. , 1855, 1857. Pringsheim — Monber. Berl. Akad. AViss., 1855, p. 133 Quart. Journ. Microsc. Sc. , 1856, p. 124). Rosanoff — (Rhodosperminy Mem. Soc. Sc. Xat. Cherbourg, 1856; Ann. Sc. Xat., iv., 1865, p. 320 ; and Compt. Rend., Ixii. , 1866, p. 831. Van Tieghem — Compt. Rend., Ixi. , 1865, p. 804. Solms-Laubach — Bot. Zeit., 1867, p. 161. Askenasy — (Rhodospermin) /ii^/fl'. , p. 233. Sorby — (Rhodospermin) Journ. Microsc. Soc, 1871, p. 124. Klein — Flora, 1871, p. 161 ; and 1880, p. 65. Agardh — Epicrisis Syst. Florid., 1876; and Florid. Morpho]. with atlas), 1879. Bornet and Thuret — Notes Algologiques, fasc. i. and ii. , 1876, 18S0 ; and Etudes Phycol., 1878. Falkenberg — Nachricht. Gesell. Wiss. Gottingen, 1879 and 1880. Ambronn — Bot. Zeit., 1880, p. 61 ; and Sitzber. Bot. Verein Brandenburg, 1880, p. 74. 204 ALG.-E Schwendener — Monber. Preuss. Akad. Wiss. , iS8o, p. 327. Berthold— Pringsheim's Jahrb. wiss. Bot,, 1882, p. 569, Schmitz — Sitzber, Akad, Wiss. Berlin, 1883, p. 215. Ardissone — Phycol. mediterranea, Part i., Floridece, 1883. Buff ham — Journ. Quek. Micr. Club, 1884, p. 337. Massee — Journ. Microsc. Soc. , 1884, pp. ig?> et seq. ; and 1886, p. 561. Wille— (Tissue-systems) Bot. Salsk. Stockholm (see Bot. Centralblatt, xxi., 1885, pp. 282, 315 ; xxiii., 1885, p. 330; and xxvi., 1886, p. 86) ; and Nov. Act. Leopold-Carol. Akad., lii. , 1888, p. 51. Schiitt— (Phyco-erythrin Ber. Deutsch. Bot. Gesell. , 1888, p. 36. A complete classification of the very numerous types of structure belonging to the Floridese would carry us beyond our present limits ; and the principles of such a classification are by no means agreed on by the best authorities, many details connected with the process of fertilisation being still obscure. Agardh, in his ' Epicrisis,' divides the family into six groups, dependent on the structure and mode of develop- ment of the cystocarp, and into twenty-two orders. We shall therefore confine ourselves to an account of some groups or special forms, the structure of which has been specially studied, commencing with the most highly differentiated orders. In the Ceramiace.e, which are exclusively marine, are included a considerable number of the more delicate red seaweeds of our own and other coasts, included in the genera Callithamnion (Lyng.), Griffithsia (Ag.), Ptilota (Ag.), Crouania (Ag.), Ceramium (Lyng.), and others. The thallus is either monosiphonous and uncorticated, or more or less corti- cated. In Crouania (fig. 1 7 2) the branches are beautifully whorled. The procarp frequently consists of a carpogone and two trichogynes. The cystocarps are formed externally on the branches or at their base, and are frequently closely surrounded by them as by an envelope. AMth rare ex- ceptions the cystocarp consists of a roundish or lobed nucleus, enclosed in a colourless gelatinous membrane, v.ithout any pericarp, and composed of a larger or smaller number of closely packed carpospores. The tetra- sporanges are usually external, and the mode of division of their contents varies greatly. The complicated process of fertilisation in Dudresnaya has already been described. In addition to the tetraspores, two other special kinds of non-sexual organs of propagation occur in the order. Some species of Ceramium are characterised by the presence oifavellce, dense agglomerations of spores, resembling the cystocarps, but pro- duced at the ends of branches, quite exposed except for a thin colourless membrane. They appear to be homologous to the multipartite tetra- sporanges. Callithamnion seirospermum (Griff.) (Seirospora Griffithsiana, Har\-.), C. versicolor (Drap.), and some other species, produce seirospores, 'V Fig. i8r. — Branch of Ceramhun strictiiiJi Grev. with favellae ( X 40). (After Kiitzing.) liifinwnnnnnoniinn^f/niinnnnmnanwnnf^ b Fig. 180. — Branch of CaUitha77inioi seirosper/niun Griff., with seirospores ( X :oo). (After Kiitzing.) Fig. 182. — Melobesia meinbranacea Lmx. a, vertical section through female conceptacle ; b, vertical sectiorr through conceptacie with tetraspcranges ; c, vertical section through male conceptacle (x 350); d, pol- linoids (x 1300). (Al.er Rosanoff.) 2o6 ALG.-E branched rows of roundish or oval spores resulting from the division of terminal cells of particular branches, or produced on the main branches. Literature. Cramer — Pflanzenphysiol. Untersuch. , 1857 and 1863. Nageli— Sitzber. Miinch. Akad. Wiss. , 1861, p. 297. Pringsheim — Abhandl. Berlin. Akad. Wiss., 1862, p. i. The CoRALLiNACEyE (Corallina, L., Melobesia, Lmx., Lithothamnion, Phil, Amphiroa, Lmx., &c.) are distinguished from other marine a "%L .-t. --^;.-1,< ^ ,A4^y^— ^^^■■ ji^ I5\r ■. ■■ • >.a-jV Fig. i-Zi. — Corallina officinalis L. a, longitudinal section through conceptacle with tetrasporanges ; b, longitudinal section through cystocarp (x 100). (After Bornet.) algae by their calcareous habit. Most of the species are natives of warmer seas. In Corallina the thallus is at first soft and flexible, but it soon becomes very hard and brittle from the deposition of calcium carbonate. The red colour and branching habit give this genus a remarkable resemblance to small corals, as in C. officinalis (L.), the common ' coralline ' or ' nullipore ' of our southern coasts. Many species of Melobesia (fig. 182), Lithothamnion, Lithophyllum (Phil.), and other genera, grow as lichen-hke incrustations or in the form of small flat FLORIDE.^ 207 discs attached to rocks, or on the leaves of Zostera, or on other seaweeds. The sexual reproductive organs and the non-sexual organs of propaga- tion are alike formed in small cavities or conceptades^ which are either entirely imbedded in the thallus, or more often form external wart-like or ovoid swellings. The female conceptacle opens at the apex by an ostiole (fig. 182, a)] the very short sporiferous filaments, the terminal cells of which a i X Fig. 184 — Corallina rubens L. a, branch with three cj-stocarps and a male conceptacle ; con- ceptacles of Melobesia TlturetL Born, are attached to the upper part of the branch (x 20) ; b, longi- tudinal section through a male conceptacle deprived of its calcareous incrustation (x 160) ; c, pol- linoids(x 400). (After Bornet.) become the carpospores, spring from the base of the cavity, and are accompanied by paraphyses. The male conceptacles are of similar structure ; the poUinoids (fig. 182, d) possess one or two short appen- dages. The non-sexual present a general resemblance to the sexual conceptacles ; the tetrasporanges spring from their base and sides, and are accompanied by paraphyses : the contents of the sporange not un- 2o8 ALG^ frequently divide into only two tetraspores. The conceptacles are not unfrequently surmounted by singular horn-like processes. Melobesia produces peculiar branching septated gemince. Literature. RosanofF — Mem. Soc. Sc. Nat. Cherbourg, 1866. Areschoug — Observ. PhycoL, iv., 1 875. Solms-Laubach — Die CoralHnenalgen d. Golfes Neapel, 1881. The greater number of our red seaweeds belong to the following orders, established by Agardh, the boundaries of which are not in all a ■ ■ ■ .^ '^, Fig. \%s- — Cho7idrjts crispus Stackh. a, with cystocarps (natural size) ; b, uppermost portion of frond with tetrasporanges (natural size) ; drOO O a ^ c^o^ Fig. 187.— Vertical median section of swelling on frond of Gracilaria cott/erz'oides Grev. /, /, cells of procarp , ^c, placental cells ; s, s, s, spores ( x 400). (After Johnson.) substance known to microscopists as 'agar-agar' is yielded also by Gracilaria lichenoides, Eucheuma spinosa (Ag.), and other seaweeds. Several other species are employed in different parts of th(=t world as glues and varnishes. ^Marchesettia spongioides (Hauck) (Areschougiacese), from Singapore, has a remarkable resemblance to a sponge. Literature. Berthold — (Cryptonemiacege) Fauna u. Flora Golfes Xeapel, 1884. Johnson — (Gracilaria) Annals of Botany, i. 1888, p. 213. The Squamariace^ (Hildenbrandtia, Nard., Cruoria, Fries, Peysson- nelia. Dene., Szc.) are a small group of small marine, or rarely fresh-water Alga5, growing on stones or on the shells of molluscs or Crustacea, or attached to larger algse. The ' frond ' is expanded flat or hemispheri- cal, gelatinous, membranaceous, or crustaceous, with lichen-like habit, composed of a single layer of cells, or more often of short densely FLORIDE.^ 211 packed vertical filaments. The species of Hildenbrandtia form rose- coloured incrustations on rocks, stones, and shells in salt or (H. rivularis, Ag.) running fresh water. The tetrasporanges are either terminal cells of special filaments, enclosed in a gelatinous coating and rising verti- cally from the flat thallus ; or they are formed in nematheces, in external wart-like protuberances, or in depressions in the surface of the thallus. The cystocarps are also either formed in nematheces, or are external, I '^^^ t: I - : vOMeo5o«ee-- it-:-' ■-■■-■. 'C ■ ' ' - - ■:':'"-■:■ --■■.' _ : y ^ ^^«^' .->''' '^^^'^~^---^— ^--^^^'^ -^-.i:.^^.^.^ ^- FiG. i88. — Hildeiihrandtia prototypJis Nardo. Vertical section through thallus, showing three conceptacles with cystocarps ( x 300). (After Kutzing.) springing from moniliform fertile filaments. It is stated that there are sometimes two kinds of carpogone, one provided with a trichogyne, the other not. After a carpogone of the first kind has been fertiHsed through its trichogyne, it puts out a fertihsing-tube or 'ooblastema- filament,' which impregnates a carpogone of the second kind. In Hildenbrandtia a large number of antherids are developed from a single -cell of the thallus. Literature. Schmitz— Sitzber. Xiederrhein. Gesell., 1879. Borzi — Rivista Scientifica, 1880. Petit — Bull Soc. Bot. France, 1880, p. 194. Wollny — Hedwigia, 1 886, pp. I and 125. The HelmixthocladiacE/E (including Nemalie^e, Batrachospermese, and Chsetangiace^e) comprise a number of marine (Helminthocladia, Ag., Nemalion, Ag., Liagora, Lmx., Galaxaura, Lmx., iS:c.) and fresh-water (Chantransia, Fries, Batrachospermum, Roth, Thorea, Bory) forms, the relationship of which to one another is uncertain, and the family is not likely to be one that will be ultimately retained. The fresh-water species are mostly of small size, but of great beauty from the elegant symmetry and arrangement of the branches. The ' frond ' of Liagora and Galaxaura is calcareously incrusted, like that of a coralline ; that of P2 212 ALG.F. some other genera is very soft and gelatinous : the whole is usually enclosed in a gelatinous envelope. The thallus is of filamentous struc- ture, and either simple or ])ranched, the secondary axes often arranged in whorls. The main axis usually consists of a central row of cylindrical cells surrounded by a pseudo-cortex composed of smaller cells, either placed in rows at right angles to the axis, or parallel to it. It may, how^- ever, consist of a single uncorticated row of cells. Batrachospermum is a genus of small green fresh-water Algae of great beauty from the symmetry of their branching. The stem grows by means of a cup-shaped ^ ^ ^ % ^^\ J D 0 0 ci^v.^;^*" "II^.*?;'^, eg F?^ ;>. BiS> ^^ Fig. iZ'> Y opens at its apex and exudes a drop of colourless mucilage. The oogone still contains chlorophyll, and its protoplasmic contents contract into a green oosphere. At the same time flask-shaped protuberances grow out from adjoining cells, and these, becoming cut off from the parent- cells by septa, are the antherids. The entire contents of each antherid escape as a single ovoid antherozoid furnished with two very long and slender cilia. Other species are dioecious, the antherids being produced on different individuals from the oogones. The antherozoids probably pass into the trichogyne through its open apex, and thence into the oogone ; but the act of impregnation has not actually been observed hitherto. The first result of the impregnation of the oosphere is its investment Fig. x(^().—ColeochcEiepulvinataX. Br. A, portion of fertile thallus(x 350) ; «;?, antherid -.og; oogone : h, hyaline hair ; z, antherozoid. B, ripe oogone with its pericarp, r ( x 280). C, formation of carpospores within the spermocarp ( x 280). D, zoospores ( x 280). (After Pringsheim.) by a cell-wall of cellulose, and a considerable increase in its size. The fertilised oogone, with the exception of the trichogyne, then becomes surrounded hy b. pericarp, or cortical layer of cells ; the oogone and peri- carp together constitute the spermocarp enclosing the fertilised oosphere or, oosperin. The spermocarp subsequently becomes further invested by a cortex of closely applied branches resulting from the continued de- velopment of cells at the base of the spermocarp. After the complete development of this organ, which takes place between ]\Iay and July, the vegetative cells of the thallus disappear, and its walls assume a dark- brown colour. The spermocarp remains dormant through the winter ; 222 ALG^'E the cortical layer is then thrown off, and the oosperm divides into several cells or carpospores. The germinating carpospore does not give rise to a new thallus, but to a zoospore, which gives birth to several successive non- sexual generations propagated by zoospores, until the cycle of generations is completed by the production of a sexual individual. Mycoidea parasitica Cunn. (Trans. Linn. Soc, vol. i., 1879, P- S^^) is probably nearly allied to Coleochsete, which it resembles in the nature of its thallus and in its mode of reproduction. It is endophytic in the cells of the leaves of Camellia in tropical India, inflicting great injury on the trees. Ward (Trans. Linn. Soc, ii., 1884, p. 87) contends that Mycoidea is in reality an epiphyllous lichen. Mobius (Ber. Deutsch. Bot. Gesell., 1888, p. 242) regards Mycoidea, and the nearly allied Chsetopeltis (Berth.), as more probably belonging to Chcetophoraceae. Literature. Brebisson — Ann. Sc. Nat., i. , 1844, p. 25. Pringsheim — Jahrb. wiss. Bot., i860, p. i. Kny — Ber. Deutsch. Bot. Gesell., 1884, p. 93. Order 2.— CEDOGONiACEyE. This small order, as at present constituted, comprises only two genera — CEdogonium (Lk.) and Bulbochaete (Ag.). CEdogonitwi includes several species, abundant in streams, ponds, and tanks. They are readily distinguished by the fact that they never branch, by the cells being of small diameter and considerable length, filled with a homogeneous dark-green protoplasm with a parietal nucleus, and by the peculiar appearance of annular striae near one end of some of the cells. These striae result from the appearance known as 'inter- calary surface-growth.' Below the septum is formed an annular deposit or cushion of cellulose ; at this place the cell-wall splits, as if by a circular cut, into two pieces, which separate from one another, but re- main united by a zone of the cell-wall formed by an extension of the cushion. This process is constantly repeated over a short space of the cell-wall immediately beneath a septum, each slit being a little further from the septum than those that preceded it ; so that these pieces, form- ing small projections, give to the upper end of the cell the appearance of consisting of caps placed one over the other ; while its lower end appears as if enclosed in a long sheath consisting of the portion of the cell-wall below the caps. This lower portion of the cell is always cut off by a septum from the upper cap-bearing portion. The filaments are fixed at their base by a rhizoid to solid bodies or submerged plants. Non-sexual propagation takes place in CEdogonium by means of zoospores^ the formation of which affords a typical example of the process CONFER VOIDED HE TERO GA M.E 223 first described by K. Braun as the ' rejuvenescence ' of a cell, i.e. the transformation of the entire protoplasm of a vegetative cell into a ' primordial cell,' which subsequently invests itself with a new cell-wall, and forms the starting-point of the life of a new individual. In some one cell of a filament, either the terminal or some other, sometimes even in the single cell of which a young filament is composed, the proto- plasm contracts into a globular body which ultimately becomes free by the rupture of the cell-wall, by a transverse slit, into two very un- equal halves. When this takes place in the terminal cell of a filament or the single cell of a young individual, the upper smaller portion of the cell-wall is lifted up like a lid, or even completely thrown off like a cap. The zoospore thus formed, which in some species is one of the largest and most striking known, has a nucleus, a red ' pigment-spot,' and an anterior hyaline region, to which is attached a tuft of cilia, visible even before its escape from its mother-cell. At the period of escape it is still enveloped in a transparent membrane, which, however, it soon breaks through, and then moves about in the water with great velocity for perhaps half an hour, displaying at this period a number of vacuoles. On coming to rest, the zoospore becomes attached by its anterior hya- line end, loses its cilia, invests itself with a cell-wall, puts out a rhizoid from the point of attachment, and develops into a filament with transverse septa. From the position occupied by the zoospore in the mother-cell, the direc- tion of growth of the new individual must be at right angles to that of the parent-filament. Many of the plants which spring from zoospores are non-sexual, producing nothing but zoospores. CEdogonium is also reproduced by resting-spores (Wille, Bot. Gesell. Stockholm, Sept. 26, 1883 : see Bot. Centralbl., xvi., 1883, p. 215). The sexual reproduction of CEdogonium still shows a high degree of differentiation of the male and female elements. The atitherozoids are ver}' similar in form to the zoospores, but much smaller, and they are provided with a similar tuft of cilia. The anfherids are cells belonging to ordinary filaments, but shorter and not containing so much chlorophyll Fig. 200. — Portion of filament of CEdogo7iutm. iv in A , the cushion of cellulose which has lengthened to the piece of cell-wall, 7f' in B; c, cell- caps (magnified). 224 ALG.E as the rest, lying either singly among the ordinary vegetative cells, or sometimes in groups of as many as twelve. In most species each antheridial cell divides either horizontally or vertically into two ' special mother-cells," each of which gives birth to an antherozoid. The oogones are developed either in the same filament as the antherids or not, some species being monoecious, others dicecious. They are also frequently in groups of from three to six. Their development always takes place out of 11. Fig. 20I.— I. A, filament of (Edogonumi ciliat^iui Hass. '; «, zoosporange ; og, oogone with 'dwarf male,' in. B, oogone at the moment of impregnation ; o, oosphere ; z, antherozoid ; in, 'dwarf male.' C, C£".^t';;^^///^^r?, mature plant with oogone, o, and 'dwarf male,' dju (x 400'. (After Cooke.) In some species the mode of fertilisation is more complicated. Peculiar zoospores known as androspores are produced non-sexually in special cells of the parent-plant, similar to those which give birth to the antherozoids, only that there is in their case no preliminary formation of 'special mother-cells.' These androspores, which closely resemble the antherozoids in form and size, fix themselves after swarming to a definite spot on the female plant, on or near an oogone, producing very small male plants, which are known as ' dwarf males ' or micrandres. Each of these consists of two or three cells, the uppermost of which is an antherid. This gives birth to one or more antherozoids, which escape Q 226 ALG.^ by the lifting up of a lid, and which impregnate the oospheres in the usual way. A\'hen the hypnosperm germinates after a lengthened period of rest, it does not immediately develop into a new plant, but breaks up into several zoospores, usually four ; these give birth to several generations of non-sexual plants, until the cycle is completed by the production of antherids and oogones. The sexual plants, however, especially the female ones, produce zoospores as well. The species of i5///^^(r/^(^/ are a prolongation of those of which the thallus is composed, and frequently project, through the mouth or ostiole of the conceptacle, into the surrounding water. When infertile these hyphae are known as paranemes or paraphyses. In the male conceptacles they are usually branched, unbranched in the female. Both the barren and fertile con- ceptacles are always first formed in the neighbourhood of the growing point, the cavity originating from the absorption of a row of cells at right angles to the surface. The antherids are produced on lateral branches of the hyphae in the male or in the upper part of bisexual conceptacles. Each consists of an ovoid thin-walled or sometimes double-walled cell, the abundant protoplasm of which breaks up into a number (usually sixty-four) of Fig. 209. — Section of female conceptacle of F. z'esicidos7is, clothed with unbranched hyphae bearing the oogones ; o, ostiole (magnified). minute antherozoids, pointed at one end, with a pair of cilia of unequal length placed laterally below the beak-like apex, and contains an orange- red pigment spot and a nucleus. The olive-brown oogones are developed from unbranched hyphae in the female, or in the lower part of bisexual conceptacles. These fertile hyphae are at first unicellular, and are bounded at the base by a septum ; the single cell subsequently divides into a basal pedicel-cell, and an upper portion, which swells into a spherical or ellipsoidal form, the oogone, filled with protoplasm coloured brown by phycophaein, and always provided with a wall composed of two layers. Either the whole of the contents of the oogone contract into a single oosphere, or it divides into two, four, or eight oospheres, each with its own nucleus. Impregnation always takes place outside 234 ALGyE the conceptacle. The outer layer of the double wall of the oogone bursts, the inner layer still continuing to enclose the oospheres in a thin bladder-like membrane. In this form they escape from the conceptacle through the ostiole into the surrounding water, where the remaining membrane is also absorbed. In the meantime the antherids have become detached, the inner layer of the double cell-wall having burst through the outer layer, and collect in large numbers before the ostiole of the female or of the bisexual conceptacles, forming orange- red masses which are often caught by the paraphyses which hang out from the ostiole, or are left on the shore at low tide. On the return of the tide, or after they have remained for a time entangled in the paraphyses, the inner membrane of the antherid also becomes absorbed, and the antherozoids escape at the same time that the oospheres become released from their - - ^ Fig. 2IO. — F. vesiculosus. ^ , branched hj-pha bearing antherids ( x i6o). ^, antherozoids ( x 330). /, oogone, Og, containing eight oospheres ; p, unbranched hyphae. //, oospheres preparing to escape ; a, outer, z", inner layer of cell-wall of oogone. ///, oosphere surrounded by antherozoids. IV, F, stages in germination of oosperm ( X 160). (After Thuret.) enveloping membrane. The antherozoids frequently collect round the oospheres in such numbers that the motion of their cilia imparts to the comparatively very large passive oosphere a rolling movement which lasts for about half an hour, when they become absorbed into it and impreg- nate it. The oospheres are receptive over their whole surface ; and, although it has been calculated that the bulk of an oosphere is equal to that of from 30,000 to 60,000 antherozoids, an oosphere can apparently be fertilised by a single antherozoid. In this family the mode of repro- FUCACE.^ O 1 - duction consisting in the impregnation of a passive oosphere by motile antherozoids attains its highest development among Algae. The antherozoids retain their motility and vitality for from one to three days. The oospheres will show signs of a rudimentary germination even when unfertilised, but in that case the germ soon perishes. Thuret succeeded in obtaining a hybrid Fucus by impregnating the oospheres of F. vesicu- losus (L.) by the antherozoids of F. serratus (L.). A short time after impregnation the oosperin invests itself with a cell-wall, fixes itself to some other body, and begins to germinate with- out any intervening period of rest. The first transverse division of the young germinating filament is followed by others in various direc- tions, so that a solid mass of pseudo- parenchyme is at length formed, fixed to the bottom by a root-like rhizoid. The Fucace^e constitute a small and well - marked family of seaweeds, united by some sys- tematists with the Phseosporese, or at least with the Lami- nariaccce, to make up the Fucoideae of Agardh, or the Melanospermese of Harvey. They are, however, well dis- tinguished by their mode of reproduc- tion. The family is represented in Britain by the genera Halidrys (Grev.), Cystosira (Ag.), Pycnophycus (Ktz.), Fucus (L.), Ascophylla (Stackh.),and Himanthalia (Lyng.), and includes also the exotic genera Sargassum (Ag.), Pelvetia(Dcne.), Durvill8ea(Bory), Splachnidium(Grev.), and a few others. Although the number of native British species described by Harvey is only thirteen, some of these occur in such vast quantities that the Fucaceae Fig. 211.— The gulfweed, Sargassum bacciferum Ag. (natural size). 2-,6 ALG.-E -J cover a larger amount of surface of tidal rocks than all the other sea- weeds together. Among these may be especially mentioned the familiar bladder-wrack, Fucus vesiculosus, so abundant on all our coasts. The well-known gulfweed, Sargassum bacciferum, distinguished by its berry- like air-bladders, a native of warmer seas, is sometimes thrown up on our shores, where it is carried by the gulf-stream. It very rarely fructifies ; detached pieces, buoyed up by the air-bladders, being able to retain their vitality for an indefinite length of time. An enormous floating mass of this seaweed, consisting entirely of detached pieces, is said to cover an area of 200,000 square miles in the Atlantic, about lat. 20-25^ N. and long. 40° W., where it has maintained itself with but little shifting since the time of Columbus, affording a home and breeding-place for countless numbers of marine animals. The family is, however, chiefly European ; a large proportion of .the species live only in shallow water, being exposed at every ebb-tide, or only at neap-tides, when fertilisation takes place. The distinctions be- tween the different genera are made to rest on the disposition of the air-bladders and conceptacles, and on the more or less distinct differen- tiation of the leaf-like organs. The frond of Splachnidium is partially gelatinous. The structure of that of Durvillaea, one of the largest of seaweeds, is very beautiful, being permeated by very large and regular cavities resembling a honeycomb. Together with the Laminariaceae, our native Fucaceae are largely used in the manufacture of kelp, though not to the same extent as formerly, and as a source of iodine ; they are also employed by farmers as a manure for their fields. On the coast of Chili the poorer classes use a species of Durvillaea for food, and a soup is made from it which is mucilaginous and sweet. Literature. Agardh— Species, Genera, et Ordines Fucoidearum, 1848. Thuret— Ann. Sc. Nat., 1854, p. 195. Pringsheim — Monber. Berlin. Akad. Wiss., 1855, p. 133. Rosanoff — (Pigment) Mem. Soc. Sc. Nat. Cherbourg, 1867, p. 145. Millardet — (Pigment) Comptes Rendus, Ixviii., 1869, p. 462. Kraus et Millardet — (Pigment) Mem. Soc. Sc. Nat. Cherbourg, 1870, p. 23. Kny— Bot. Zeit., 1872, p. 699; and 1875, P- 45°' Sorby— (Pigment) Proc. Roy. Soc, 1873, pp. 455 et seq. Reinke — Jahrb. wiss. Bot., 1876, p. 399 ; and Bot. Zeit., 1877, p. 651. Roslafinski — Beitr. z. Kenntniss d. Tange, 1876. Thuret & Bornet — Etudes phycologiques, 1878. Kuntze — (Sargassum) Engler's Bot. Jahrbuch, 1880, p. 191. Bower — (Conceptacle) Quart. Journ. Microsc. Sc. , 1880, p. 36. Berthold — Die Cystoseiren (Fauna u. Flora Golfes Neapel), 1883. Hanstein — Sitzber. Phys.-Med. Gesell. Wiirzburg, 1884, p. 104 ; and Arbeit. Bot. Inst. \Yiirzburg, 1885, p. 289. FUCACE^ 237 Dodel-Port — (Cystosira) Biolog. Fragmente, pt. i., 1885. Behrens — (Fertilisation) Ber. Deutsch. Bot. Gesell., 1886, p. 92. Schiitt — (Phycophaein) ibid., 1887, p. 259. Wood worth — (Apical Cell) Ann. of Bot., i. , 1888, p. 203. Class XIII. — Phseosporece. The Phceosporeae or Phaeozoosporese form, together with the Fucacese, the whole of the oUve and brown seaweeds of the globe, formerly grouped together under the names Fucoide^e, ^Melanosporeae, or Melano- spermese ; but of many the histon,' of development is at present but imperfectly known ; and when this is ascertained more fully, they may possibly be separated into groups having but little affinity with one another. A number of the Phseosporese are epiphytic, and a few parasitic on other seaweeds ; a very few grow in fresh water. The ordinary mode of multiplication of the Ph^osporese is, so far as is known at present, non-sexually by means of zoospores, which occur in all the orders except the most aberrant groups — the Dictyotaceae, where they are replaced by motionless spores, and the Syngeneticae. In the Sphacelariace^e there is another mode of non-sexual propagation by means of gemm^ ox propagules. Each zoospore has a large red pigment- spot and two cilia, a longer one pointing forwards and a shorter one directed backwards. They differ from those of the green Algae, such as the Confer voideae, in the lateral insertion of the cilia at the base of the colourless apex. They are produced in zoosporanges, which are either external, when they are usually the terminal cells of short branches, or are imbedded in the thallus, in which case they are frequently collected into definite groups or sori, and are interspersed ^^ ith barren filaments or hyphse, known as paranemes ox paraphyses. These are often swollen and club-shaped at their apex ; the zoosporanges sometimes spring as lateral branches from similar filaments. The zoosporanges are of two kinds, uniloadar and miiltilocidar (the 'oosporanges' and 'trichospo- ranges' respectively of Thuret). The former are comparatively large, nearly spherical, ovoid, or pear-shaped, and their contents break up directly into a large number of zoospores which escape through a terminal or lateral opening. The latter kind have somewhat the appearance of jointed hairs, and are segmented in the transverse direction only ; or less often are more like the unilocular zoosporanges in form, but are divided internallv by both transverse and longitudinal septa. Each cell gives birth to a single zoospore ; and these either escape each separately 238 ALG.-E from its own mother-cell, or an opening is formed at the apex of the sporange through \Yhich all the zoospores escape after dissolution of the septa. The zoospores are in all cases imbedded in mucilage ; no differ- FiG. ixi.—Giraiidia spliacelarioides D. and S. a, upper portion of thallus (x 250) ; b, lower portion with multilocular sporanges(x 250). (After Areschoug.) c, portion of filament with unilocular sporanges (x 6od). (After Hauck.) PH.-EOSPOREAL 239 ence is observable in size or form between those produced in the two kinds of sporange, but those from the unilocular sporanges appear in all cases to germinate directly, while those from the multilocular sporanges are sometimes zoogametes with sexual functions. The two kinds of sporange ma}^ be. borne on the same or on different indi- viduals ; in the former case they are occasionally developed at different times. In certain orders or groups one or the other kind is altogether wanting. The various modes of sexual reproduction known in the Phc^ospore^e present a most interesting gradual transition from the conjugation of equivalent motile zoogametes to the impregnation of a quiescent oosphere by motile antherozoids. In Ectocarpus (Lyng.), Giraudia (D. and S.), and Scytosiphon (Ag.) conjugation takes place between swarm- cells from the multilocular sporanges, which are to all appearance exactly alike : but a slight sexual differentiation is exhibited in the fact of one of them coming to rest and partially losing its cilia before conju- gation takes place. In Cutleria (Grev.) and Zanardinia (Xard.) the differentiation is more complete. The male and female swarm-cells are produced either on the same or on different individuals : the latter are much larger than the former, and come perfectly to rest, entirely losing their cilia before being impregnated by the former. In Dictyota (Lmx.) the differentiation is carried still further, and the female reproductive bodies are from the first motionless masses of protoplasm not provided with cilia. In Dictyosiphon (Grev.) (Punctariacese) a different kind of conjugation has been observed. The degree and mode of development of the thallus differ verv widely within the class. A few species of Ectocarpaceae, belonging to the genera Streblonema (Derb.) and Ectocarpus (Lyng.), are microscopic. Some of the Mesogloeaceae and Ralfsiacese are small seaweeds epiphytic on those of larger growth, with a flat radiating thallus reminding one of Coleochcete. In some of the Ectocarpaceae the thallus consists of simple branched or unbranched filaments resembling those of the Confervaces. In the Sphacelariace^ each branch is composed of a row of larger central surrounded by a layer of smaller cortical cells, all originating from a large uncorticated apical cell. In the Cutleriaceae filaments of cells become separated from the margin of the thallus, the basal portions of which are coalescent into a sohd tissue, the increase in breadth of which is due to the branching of the filaments. The Laminariace^e include, in the genera Alaria (Grev.), Laminaria (Lmx.), Macrocystis (Ag.), and others, the most gigantic of marine organisms, in which the thallus or ' frond ' is to a certain extent differentiated externally into rhizoid or organ of attachment, stipe or stem, and 240 ALG^E leaves. We have here also an approach to the internal differentiation of tissues which occurs in the liigher plants, though this is not so strongly displayed as in the Fucaceae. In Macrocystis, however, the lamina of the frond may be divided into an epidermal layer, cortical parenchyme, and medullary tissue. Sieve-hyphse occur in all the genera, and in Macrocystis and Nereocystis (Post.) true sieve- tubes with sieve-plates and deposit of callus. Through the perforations in the sieve-plates HickQourn. Bot, 1885, p. 356) and Willehave detected the passage of strings of protoplasm connecting the cells with one another. The protoplasts of the cortex in Laminaria digitata (Lmx.) are described by Hick as rhizopod- like bodies spreading in such a. way that the cells of each layer are brought into connection both with one another and with those of adja- cent layers. The cells of the Phseosporeas con- tain a carbohydrate closely resembling starch, but differing in not being coloured blue by iodine, and an olive-brown pigment soluble in cold fresh water identical with the phycophcein of the Fucace^. The tissues both '■O PH.-EOSPORE.r. 24T of the Laminariacece and of other large marine Algce belonging to other groups display remarkable elasticity or other properties to enable them to resist the traction of the waves. In the larger species the frond is buoyed up by air-bladders. Janczewski describes the occurrence in the class of three distinct modes of growth, viz. — (i) The thallus and all its ramifications terminate in a generative apical cell which divides in a direction parallel to its base, and thus gives birth to a series of segments. This occurs in the Sphacelariace^ and in Dictyo- siphon, but is the least common mode. {2) By peripheral growth, i.e. the marginal cells of the thallus are the youngest, and are more or less united into a generative peripheral zone (Myrionema, Grev., Leathesia, Gray, Ralfsia, Berk.). (3) By in- tercalary growth. This is much the most common mode, and there are, again, three modifications of it, viz. — I. The thallus terminates, when young, in one or more hairs, the common growing point of the thallus and of the hairs being situ- ated at their point of junction (Ecto- carpus, Desmarestia, Lmx., Carpo- mitra, Ktz., Cutleria, Sporochnus, Ag.). 2. The thallus is differen- tiated into three 'organs' — frond, stipe, and rhizoids ; the growing point from which the stipe and frond originate is common to these two organs, while the rhizoids increase by apical growth (Laminariaceae). 3. The absolutely undivided thallus is regenerated from the growing point situated at the base of the frond (Scytosiphon, Chorda, Punctaria, Grev., Asperococcus, Lmx.). Fig. 214. — Lcssonia J-uscescetis Bon* (greatly reduced). Literature. Magnus — Festschr. Gesell. naturf. Freunde, Berlin, 1873. Areschoug— Bot. Notis. , 1873. Gobi-Bot. Zeit., 1877, p. 425. Reinke — Ibid., p. 441. Thuret & Bornet— Etudes Phycologiques, 187S. R 242 ALG.E Falkenberg -Mitlheil. Zool. Stat. Xeapel, 1 878, p. 531- Wille — Bot. Sallfik, Stockholm, Nov. 19, 1884 (see Bot. CentralbL, xxi., 1885, pp. 2%2 et seq.). \ >.e ^^/ In so many of the Phoeosporeae the Hfe- historv is at present but imperfectly known, and different authors differ so widely as to the best characters to be employed in classifica- tion, that no attempt is here made to arrange into orders all the known forms. A de- scription is given only of the best-marked groups. The Lamixariace.^ include many of the largest of the brown seaweeds of both warmer and colder seas ; in the southern hemisphere they form dense submarine forests of gigantic size, frequently making even deep water impass- able for boats, and forming a home for myriads of marine animals ; the individual ' fronds ' sometimes attaining a length of several hundred feet. The thallus is coriaceous, is not articu- lated, and is usually attached to the sea-bottom by rhizoids or root-like organs of attachment, or less often by a discoid expansion, from which springs a tough cylindrical stipe or stem, the tissue of which is more or less differentiated into a medullary portion, an internal and an external cortical portion, and an epidermal portion, the cells of which are coloured brown bv phycophasin. It increases in length by intercalary growth at the junction of the stipe and lamina. Although most of the larger species are perennial, Areschoug states that even the largest species of Xereocystis (Post.) are annual. In others the stem increases in girth from year to year, attaining sometimes the thickness of a man's thigh. In Chorda filum (Stackh.), one of the commonest of our seaweeds, the entire thallus is cvlindrical and Fig. 215. Laviinariasaccliarina Lmx., with rhizoids. s, por- tion of frond which produces . zoospores (reduced \). (After whip- like, as much as lorty fect in length, Reinke.) PI a Fig. 217-— Longitudinal section oi Macrocystis ^yrifera. showing sieve-tubes, /, and sieve-plates, j, with callus (x 3C0). (After Oliver.) Fig. 216. — Chorda filuin Stackh. «, uppermost and lowermost ;)ortion of frond (natural size); b, transverse section, she win aj differentiation into cortical and epidermal layers (x 200). (After Hauck.) R 2 244 ~ ALG^ and is septated by transverse divisions; it is constantly dying off at the apex, the growing point lying at its base immediately above the rhizoids. More often the upper part of the thallus is differentiated into branched annual 'leaves' of cartilaginous texture, usually flat, but sometimes tubular, and often ribbed. Lessonia (Bory) grows erect to a great height, and resembles a branching tree with pendent leaves two or three feet long (fig. 214). In Thalassiophyllum (Post), Agarum (Grev.), and other genera, the frond is beautifully perforated ; these perforations are formed from hollow conical papilte by w^hich the frond is first covered ; the tissue diminishes at the apex of the cones, then bursts, and the opening enlarges as the frond grows. In Macrocystis (Ag.) the stalk-like base of each branch of the frond is swollen out into a large pear-shaped air-bladder. In Nereocystis the air-bladder is barrel-shaped, six or seven feet in length, and crowned with a tuft of fronds. Sieve-hyphae or trumpet-hyph^ with imperfect sieve-plates occur in all the genera ; and Oliver has discovered in the comparatively weak stems of Nereocystis and Macrocystis a structure almost identical with that which occurs in the weak climbing stems of many Flow^ering Plants, true sieve-tubes with perfectly formed sieve-plates both in the septa and in the longitudinal cell-walls, provided with a true callus-formation (fig. 217). Zoosporanges of one kind only — the unilocular — are at present known in the Laminariace^ ; these are distributed uniformly over the surface of the thallus or are collected into sori^ and are interspersed w^th simple unsegmented club-shaped sterile hairs or paraphyses. Of the mode in w^hich the zoospores act as propagative organs very little is known. Areschoug has observed the germination of the zoospores of Chorda tomentosa (Lyng.) after the coherence of two of them by their beaks ; but he does not regard this as a true process of conjugation. Gardiner be lieves that he has detected the conjugation of zoospores in Alaria (Grev.). Along w^ith the Fucacese, the Laminariaceas are one of the most im- portant commercial sources of iodine. The species of our own shores are employed in the manufacture of kelp. Alaria esculenta (L.) is used by the inhabitants of Scandinavia and Iceland as an article of food, as also are Laminaria digitata (Lmx.) and other species under the name of ' tangle.' The stems of the last-named species are employed for surgical purposes ; those of Ecklonia (Hornem.) and others of the larger genera are used as siphons and for making fishing-nets. Literature. Reinke — Pringsheim's Jahrb. wiss. Bot., 1876, p. 317, Areschoug— Observ. Phycol. , iii. , 1875, iv. , 1883, v., [884 ; and Acta Soc. Sc. Upsa- liensis, 1875, 1883, and 1884. Will — (Macrocystis) Bot. Zeit. , 1884, pp. Soi et seq. PH^OSPORE^E 245 Wille — (Sieve-tubes) Ber. Deutsch. Bot. Gesell., 1885, p. 29. Gardiner— (Conjugation of Zoospores) Proc. Cambr. Phil. Soc. , 1S86. Humphrey— (Agarum) Proc. Amer. Acad. Sc, 1886, p. 195. Oliver — (Sieve-tubes) Ann. of Bot., i., 1887, p. 95. In the Pu^x•TARIACE^, SpoROCHXACE.^i:, and Scytosiphoxace.e — the Hmits of which orders are not settled by systematists — the structure of the thallus varies greatly. In Punctaria (Grev.) and Phyllitis (Ktz.) it is flat and leaf-like, from one to six layers of cells in thickness; in other genera it is slender, cylindrical, erect, and more or less branched, the main axis being either solid or hollow, and consisting of a pseudo-parenchymatous tissue, in which the outermost or the two or three outer rows of cells are much smaller than the inner ones. In m^'^^^i^i^^^ - ajJAv.'. •;M|'V;^!^^St Fig. 2iS.—As/erocccc?es bnllostis Lmx. a, natural size (after Bornet) ; /', portion of surface with sorus ( X 100) ; c, transverse section through thallus and sorus ( x 100). (After Kiitzing.) Dictyosiphon (Grev.) the 'frond' branches into delicate hairs. In Arthrocladia (Duby) the branches are arranged in delicate whorls. In Scytosiphon (Ag.) the thallus is elongated, cylindrical, and unbranched, but' constricted at interv^als, and resembles that of Chorda in habit. In other genera, as xAsperococcus (Lmx.) and Hydroclathrus (Bory), it is hollow and bladdery. In most of the genera both kinds of zoosporange are known, while in others one or the other has not yet been detected. 246 ALG^ Their arrangement, on which the deHmitation of the orders is largely made to rest, varies greatly. They may be collected into wart-like sori on the surface of the thallus, appearing sometimes like dark dots uni- formly distributed, or they may spring from the branches. In Sporochnus (Ag.) the unilocular sporanges are collected into a peculiar receptacle J; tA Fig. 219. — Sp07-ochn7is fieduncidatus Ag. a, natural size ; b, c, receptacle containing zoosporanges ; d, unilocular zoosporange ( x ico). (After Kiitzing.) consisting of pear-shaped swellings near the extremity of the branches, composed of a dense mass of filaments on which the sporanges appear as lateral branches. Very little is known of the further history of the zoospores. In Scytosiphon lomentarium (Ag.) Berthold ('Mittheilungem Zool. Stat. Neapel,' ii., 1881) has observed conjugation of the swarm- P'H^OSPORE^ 247 spores contained in the multilocular sporanges, which must therefore be regarded as zoogametes, and the phenomena are the same as in the Ectocarpaceae. Areschoug (' Observ. Phycol., iii., 1875) describes a remarkable kind of conjugation— altogether peculiar as far as the brown seaweeds are concerned— in the swarm-spores of Dictyosiphon hippuroides (Lyng.), somewhat resembling that in the Conjugates. Two, or sometimes three, of the zoogametes cohere by their apices, and the contents slowly pass entirely into one of them, but only after they have come to rest. Both then become invested with a thin coat of cellulose, and the one into which the endochrome has passed, which may be called the female element, subsequently germinates. In other cases the con- jugating zoogametes put out conjugating tubes not unlike those of the Zygnemacese. Some of the zoospores also germinate without conju- gating. Literature. Reinke — Pringsheim's Jahrb. wiss. Bot., 1878, p. 362. The Mesoglceace.^ or Chordariaceae (Myrionema, Grev., Leathesia, Gray, Chordaria, Ag., Mesogloea, Ag., &c.) are seaweeds with a gelatinous or cartilaginous thallus of hemisphe- rical or cylindrical outline, variable in size, and forming small gelatinous or slimy cushions or branching tufts on larger seaweeds. Each filament is com- posed of a vertical central row of cells, surrounded by a ' cortex " of radial rows at right angles to the central row. On these cortical rows are placed the zoo- sporanges, which are both unilocular and multilocular, concealed within the periphery of the 'frond.' Nothing is known of the conjugation of the swarm-spores; they appear to germi- nate directly, giving rise to a creep- ing branched filament, from which the ascending axes subsequently rise Fig. 220. — CJwrdaria JJagelliformis Ag. Transverse section through thallus, with unilocular zoosporanges (x 200). (After Kutzing.) The EcTOCARPACE-E constitute an ill-defined group of small, occa- sionally microscopic, marine (Elachista, Duby, Ectocarpus, Lyng., Giraudia. Derb.) or rarelv fresh-water (Pleurocladia, Br.) Algae, usually 248 ALG.^ attached in tufts to larger algae, and resembling in habit the fresh-water Confervaceag. The thallus consists of segmented more or less branched filaments, either composed of a single row of cells or corticated. The growing point of the filament does not lie at its apex, but at the extremity of a basal portion, the true thallus, the terminal hair-like portion being deciduous. The zoosporanges are of both kinds, and are either external and stalked, or are ordinary cells of a filament, whether terminal or intercalary. Multilocular sporanges are sometmies produced on the ' ^M\ 1/v Fig. 221. — Ectocarpus invcstiens Hauck, epiphytic on Gracila7-ia comptessa ( X 250). (After Burnet.) Fig. '22-2. — Conjugation of zoogametes of pLctocarptis siliculosits Ktz. /, a~f, female zoogamete, gr^idually losing its cilia. //, male zoogametes swarming round female zoo- gamete ///, a-e, stages in the coalescence of the male and female zoogametes ( x 790). (After Berthold.) same individual as the unilocular, but at a later period. The swarm- cells which escape from the unilocular sporanges are non-sexual zoospores, germinating directly after coming to rest, and investing themselves with a cell-wall. Those contained in the multilocular sporanges all escape through a single terminal opening, and partake to a certain extent of sexual properties, or become under certain conditions zoogametes. PH.^OSPORE.-E 249 Goebel has observed their conjugation in Giraudia sphacelarioides (Derb.) and Ectocarpus pusillus (Griff.), Berthold in E. siliculosus (Ktz.). The process is thus described by Berthold. There is no apparent difference between the male and female gametes. The female swarm-spores lose their cilia and come to rest first. They appear to be in a receptive condition only for a few minutes, during which time they seem to exer- cise an attractive force on the male gametes, which swarm round them until coalescence takes place. The impregnated gamete immediately clothes itself with a cell-wall, and proceeds to germinate. If unim- pregnated it will still germinate, though not so rapidly ; as also do the male swarm-spores which fail to conjugate ; but in this case the resulting new individuals are weakly, and soon perish. This process in the Ectocarpacese may be regarded as the first stage between the conjuga- tion of equivalent zoogametes and the impregnation of a passive oosphere by an antherozoid. Wright (Trans. Roy. Irish Acad., 1877, p. 15) has detected on an Ectocarpus a parasitic Chytridium, the zoospores of which he believes to have been mistaken for sexual organs of the host. Literature. Askenasy — Bot. Zeit., 1869, p. 785. Janczewski — Mem. Soc. Sc. Nat. Cherbourg, 1S75, p. 97. Goebel — Bot. Zeit., 1878, pp. 177, 193. Berthold— Mittheil. Zool. Stat. Neapel, ii., 1881. The TiLOPTERiDE.'E (Tilopteris, Ktz., Haplospora, Kjellm.) are a :small and ill-defined family, probably nearly related to the Ectocarpaceae. The Sphacelariace/E (Sphacelaria, Lyng., Stypocaulon, Ktz., Ch^- topteris, Ktz., Cladostephus, Ag.) are all small marine Algie, mostly para- sitic ; Chaitopteris plumosa (Ktz.) grows on rocks at a considerable depth below the surface. The thallus usually consists of a number of TOWS of cells united into a pseudo-parenchyme, and often differentiated into an appearance of a ' medullary ' row surrounded by ' cortical ' tissue. In Cladostephus and Stypocaulon these corticating rows of cells descend to the base of the stem, and form rhizoids or organs of attachment. The zoosporanges are of both kinds, and are usually placed at the ends of special branches, while in Stypocaulon they are axillary ; but very little is certainly known about the germination or possible conjugation of the swarm-spores. The apical cell of each branch is uncorticated, and fre- quently develops into a hollow chamber of considerable size termed a sphacele, filled, when young, with dark mucilaginous contents, which at a later stasre become waterv. Gevler has described two kinds of sexual 250 ALGyE organ, antherids and ' sexual spores ' (oospheres), formed within the sphaceles ; but Janczewski believes that the supposed antherozoids are in reality the zoospores of para- sitic Fungi (Chytridiaceae), to whose attacks these sea- weeds are especially liable. Pringsheim describes two kinds of fructification pro- duced by Cladostephus, one in the autumn, the other in the winter ; but WoUny sug- gests that both the autumnal fructification and the so- called unilocular sporanges may be due to the attacks of parasitic Chytridiaceae. The Sphacelariaceas have a strong tendency to multiply by means of buds, gemmae, or propagides. Janczewski describes the mature gemmas as consisting of a pedicel and ^ a J FtG. 223. — Sphacclaria cirrhosa Ag. a, natural size : b, branch with propagules, a (x 100) ; c. filament with unilocular zoosporange ( X 100). (After Hauck.) Fig. 224.— .9. cir7-Jiosa. a, filament with propagule, ^ (x 140). (After Reinke.) PH^OSPORE.'E 2 5 1 three rays diverging above, with a hair springing from the centre of the rays. They become detached hke the basidiospores of Fungi, and are constantly being formed afresh. Literature. Geyler — Pringsheim's Jahrb. wiss. Bot., iS66, p. 479. Janczewski — Mem. Soc. Sc. Nat. Cherbourg, xvi., 1872, p. 337 ; and Ann. Sc. Nat., 1S73, p. 253. Magnus— Zur Morphologie der Sphacelarieen, 1873. Pringsheim - Abhandl. Berlin Akad., 1873, p. 137. Rischawi — Algol. Untersuch., i.. 1874 (Just's Jahrb. , 1874, p. 13). Wollny — Hedwigia, 1880, p. 65. The Ralfsiace.e (Ralfsia, Berk., Lithoderma, Aresch., &c.) are small seaweeds (with the exception of two species of Lithoderma which grow in fresh running water) with crustaceous thaUus, attached to stones, rocks, or the shells of molluscs and Crustacea, composed of a pseudo- b % ri-J^ ,'-'iS: -^-J^^r-i^ i'.^^i ■^ti^'\:^,. Fig. 225. — Lithoderviafatisccns Aresch. a, vertical section of portion of thaUus with unilocular zoosporanges ; b, with multilocular zoosporanges (x 320). (After Hauck.) parenchymatous tissue of vertical rows of cells. They have both kinds of sporange, collected into wart-like groups or sori on the surface of the thallus, but nothincr is known with res^ard to the function of the swarm- spores. The small order of Cutleriace.^, comprising the genera Cutleria (Grev.), Zanardinia (Xard.), and Aglaozonia (Zan.), consists of a small number of seaweeds, nearly all natives of warmer seas, although others from colder climates have been erroneously included in it. The thallus is coriaceous or membranaceous, flat, and either erect (Cutleria), or prostrate (Zanardinia), with the peculiarity that the marginal filaments are dissociated in their growth from the rest of the 'frond.' A true sexual mode of reproduction has been observed by Reinke in Zanardinia, and by Falkenberg and Janczewski in Cutleria. The former genus is monoecious, the latter dioecious. The oogones and antherids are both collected into sori, the former very dark brown, the latter orange-coloured. 2;2 ALd The oogones are divided into thirty-two or sixty-four cells, each of which produces an oosphere. The oospheres are at first biciliated swarm-cells or zoospheres endowed with active motion, closely resembling the zoo- spores of other Phaeosporese, but are larger and variable in form — one of the very few instances known in the vegetable kingdom of the occurrence of such organs. They are said to be destitute of a nucleus. The antherids are also divided into a number of cells, each of which pro- duces two antherozoids, the normal number in an an- therid (in Cutleria adspersa, De Not.) being 128. The antherozoids are also bi- ciliated swarm-cells, but smaller than the oospheres ; they have each an orange pigment-spot, and are iden- tical in structure with those of the Fucace^. The an- therozoids do not approach the oospheres until the latter have come to rest and lost their cilia ; the absorption of a single antherozoid into the oosphere is then suffi- cient to impregnate it ; it becomes invested with a cell-wall of cellulose, and begins to germinate at once. Thuret states that in C. multifida (Grev.) the oospheres germinate with- out having been fertilised. The thallus resulting from the germination of the im- pregnated oospheres is said to be dorsiventral, producing rhizoids on the ventral side only. Zanardinia produces also non-sexual zoospores in unilocular sporanges ; and has another non-sexual mode of pro- pagation, by budding. In Aglaozonia reptans (Ktz.) the non-sexual zoospores are the only reproductive organ known ; and Falkenberg Fig. 226. — Cutleria imiltifida Grev. (natural size). (.\fter Hauck.) Fig. 22J.—C. mtiltifida ; transverse section of portion of ihallus with a sorus of muitiloculax zoosporanges in different stages of development ( x 330). (After Bornet.) V ,, \ .A\\ ^»l xo- FiG. 229. — Fertilisation of Z. coUaris. a, swarm- ing oosphere ; b, antherozoids ; c, coalescence of antherozoid with passive oosphere; e section of upper portion of thallus ; d, of lower portion (x 100). (After Kutzing.) Florideas, agreeing with that order in the presence of tetraspores and of non-motile pollinoids ; but as the oogone presents no indication of even a rudimentary trichogyne, and there is no process analogous to the forma- Fig. 231. — Stages in the formation of the tetraspores in Padina Pavonia (magnified). (After Reinke.) tion of a cystocarp, it seems best, until more is known of the process of fertilisation, to retain the Dictyotaceae as an aberrant order of Pha^osporeae, with which they also agree best in the nature of their pigment. 256 ALG.^ Literature. Reinke — Nova Acta Acad. Leop. -Carol., 1878. Thuret & Bornet — Etudes Phycologiques, 1878. Hauck — (Padina) Hedwigia, 1887, p. 41. The position of the small family of Syngenetice, as constituted by Rostafinski, is one of great uncertainty. The two genera of which it is composed have generally been regarded as of a very low type of structure, and it is very doubtful whether they are nearly related to one another. The pro- bability seems to be in favour of both genera having been derived from the Phaeosporeas by retrogressive metamor- phosis in different directions. Heckel and Chareyre (Journal de Microgra- phie, 1885) regard Hydrurus and Chro- mophyton as presenting a connecting link between the Diatomaceae and the Phceospore^. Hydrurus Ag. consists of a fila- mentous thallus, attaining sometimes a foot in length, slimy and affixed to a conical disc, and growing in cold fresh running water. The filaments are simple below but branched above, often with exceedingly fine penicillate divisions, filled with a brown or olive endochrome identical with phycophaein. The sur- face is naked or densely covered with delicate hair-like appendages, which are occasionally fasciculate. The thallus is composed of cells dispersed through the gelatinous matrix ; towards the apex of the branches the cells are in close contact with one another, but in the older parts of the thallus they are some distance apart. Each is surrounded by a very delicate membrane, and Lager- heim states that some of them contain pulsating vacuoles. Propagation takes place by means of zoospores of very peculiar form, produced in the branches only, two or four from each cell. When mature the zoospores are tetrahedral, each angle being Fig. 232. — A, Hydriims penicillatus Ag. (natural size). (After Cooke.) B, zoo- -spore (greatly magnified). (After Lager- heim.) PH.^ZOSPORE.^ 257 prolonged into a slender colourless beak ; in one of the angles is a brown chromatophore ; and attached to the centre of the opposite side a single short cilium, and near it two pulsating vacuoles, but no pig- ment-spot The zoospores appear to germinate directly without con- jugation. Lagerheim has also detected, on different individuals from the zoospores, peculiar resting-spores, through the vitality of which Hydrurus remains dormant through the summer and autumn, its active life extending only through the cold season. Hydrurus is placed by Rabenhorst and Cooke among the Palmellaceae. Chromophyton AVor. is an epiphytic organism which vegetates and hibernates within the hyaline cells of the leaves of Sphagnum and other aquatic mosses. In this state it consists of unciliated naked masses of protoplasm with pulsating vacuoles, and endowed with an amoeboid motion. While still within the cells of the host, these bodies become invested with a delicate cell-wall, multiply by repeated bipartition, and assume the condition of resting-spores, the endochrome being now of a brownish red colour. From these resting-spores are developed zoospores, minute ellipsoidal or nearly spherical bodies, 8-9 p.. long and 4-6 /j.. broad, with a single cilium, a contractile vacuole, and a bright yellow or yellowish brown pigment-disc, consisting of a substance apparently identical with the diatomin of the Diatomacece. These zoospores are imbedded in a colourless mucilaginous matrix, in which condition they float in large numbers on the surface of the water of bogs in the form of a fine yellow dust. When completely immersed in water, the zoospores are set free from their investing mucilage, and at once begin to swarm. After a time each zoospore develops a second colourless gelatinous envelope, with a tubular opening below, through which it absorbs water. In this encysted condition, having now lost its cilium, it multiplies by bipartition. Although two forms of zoospore have been obser\-ed, one much smaller than the other, no process of conjugation has been detected. Cornu describes a second species of Chromophyton with stalked bodies which may be sporanges, and a siliceous coat like that of diatoms. Although in some respects presenting a resemblance to a degraded form of Ph^osporeae, it is possible that Chromophyton may be a stage in the development of some organism belonging to a totally different class. In some respects it may be compared to the Chytridiaceae among Fungi. Literature. Woronin— (Chromophyton) Bot. Zeit. , 1S80, pp. 625, 641. Rostafinski— Hydrurus u. seine Verwandtschaft, Krakow, 1882 (Ann. Sc. Nat., xiv. , 1882, p. 5). S 258 ALG.E Cornu — (Chromopbyton) Bull. Soc. Bot. France, 1883, p. xciii. Hansgirg — Oesterr. Bot. Zeitschr. , 1884, p. 31. Lagerheim — Ber. Deutsch. Bot. Gesell. , 1888, p. 73. Phceothainnion Lagerh. (Bot. Zeit., 1885, p. 604) is a fresh-water alga forming brownish yellow tufts on Vaucheria, Cladophora, &:c. Certain cells develop into zoosporanges, each of which produces two biciliated zoospores, and the alga has also a palmella condition. Not- withstanding the brown endochrome, and the fact that the zoospores germinate directly and have not been observed to conjugate, Lagerheim places this genus near to Chroolepideae and Chaetophoraceae, making it the type of a new family, Ph.^othamnie.^. It may possibly, however, be more nearly related to the Syngeneticse. Class XIV.— Conjugatse. The Conjugatoe, as defined by de Bary, constitute an extremely well- marked and natural group, composed of the three families Mesocarpacece^ Zygnemacece, and DesniidiacecE, with no near affinities (except possibly with the Diatomaceae). The individual is unicellular in most of the Desmidiacese ; but in some genera of desmids, and in all belonging to the other two orders, it consists of a filament of cells, which is almost invariably unbranched. The arrangement of the bright green endo- chrome, in spiral bands, plates, discs, or stars of beautiful symmetry, is altogether peculiar to this group of plants, and renders them among the most interesting and beautiful of microscopic objects. No formation of zoospores occurs throughout the class, and the ordinary mode of vegetative increase is by simple cell-division, and the breaking up of old individuals in the filiform genera into fragments. They retain their power of life through the winter, when under conditions unfavourable to the formation of zygosperms, by the production of ?'esting-spores, or single cells which retain for a long period their vitality. These may be either akinetes or aplanospores in Wille's sense of the terms. Gay states (Bull. Soc. Bot. France, 1886, p. 41) that the filaments of Zygnema (Ktz.), especially when growing in dry situations, have a tendency to break up into cysts, i.e. fragments which become enclosed in a mucila- ginous sheath, resulting from the gelifi cation of the outer layers of the cell-wall. These cysts may preserve their vitality for months, and then, when moisture again penetrates the sheath, they divide by trans- verse septa, and develop into new individuals. The single cell of the Uesmidiaceae and the filament of the filiform genera is enveloped in a CONJUGAT.^ 259 thin transparent mucilaginous sheath. According to Klebs (Untersuch. Bot. Inst Tubingen, 1886, p. 333) this sheath is composed of two dis- tinct portions, a homogeneous substance which is but sHghth- refringent, and a portion which consists of minute rods placed at right angles to the cell-wall. He regards this mucilaginous sheath as entirely independ- ent of the substance of the cell-\Yall, and derived from the protoplasmic contents of the cell by diffusion through the cell-wall. The same struc- ture probably prevails also in the Confervaceas and other filiform algse growing in fresh water. The Desmidiacese possess a remarkable power of apparently spontaneous motion, which will be spoken of in detail under that order. The only sexual mode of reproduction in the Conjugatce is the €07ijugatio}i of stationary cells, found nowhere else except in some of the Zygomycetes. This consists, in the unicellular genera, of the complete •union or fusion of the protoplasmic contents of two individuals ; in the multicellular genera, of the isogamous union of the whole or a part of the contents of gametes or non-motile unciliated cells into a zygosperju ; conjugation may take place between cells belonging to the same or to different filaments. Whether the two conjugating cells are physiologi- cally equivalent or not will be discussed under the separate orders, and the process described more in detail. Klebahn finds the union of the two nuclei in the zygosperm to take place only slowly in Zygnema (Ktz.) -(Zygnemaceae) ; while in Closterium (Nitzsch) (Desmidiaccce) they remain distinct even in the mature zygosperm. The Zygnemaceae must be regarded as the typical family of Conju- gatse, from which the Desmidiacese have probably been derived by retrogression, exhibited, in most cases, by the reduction of the filament to a single cell. The Mesocarpaceae display an approach to a higher type of sexual reproduction in the more complicated processes connected with the formation of the zygosperm. The reasons for excluding the Diatomaceae from the Conjugatae, contrary to the opinion of some -writers, and placing them in a totally different group, will be given hereafter. Many of the Conjugatse are extremely abundant in fresh water, whether running or stagnant, to which they are almost entirely confined ; some of the filiform species grow also on moist ground and among moss. Literature. De Bary — Untersuchungen liber die Conjugaten, 1S58. Gay — Essai d'un ]Monographe des Conjuguees, 1884. Bennett — Journ. Linn. Soc. , xx., 1884, p. 430. Klebahn — (Zygosperm) Ber. Deutsch. Bot. Gesell., 1SS8, p. 160. s 2 26o ALG.-E Order i. — Mesocarpace^. The species belonging to this family consist of cylindrical unbranched or \-cry rarely branqhed filaments of elongated cells, in which the chloro- phyll is not arranged, as in the Zygnemaceae, in stars or spiral bands, but in a thin axile plate occupying one diameter in each cell, and con- taining a number of conspicuous starch-grains ; those of adjacent cells lying usually or invariably in the same plane. Vegetative propagation takes place by the breaking up of a filament into its constituent cells ; sexual reproduction by a process of conjugation, which may take place either between cells of the same or of different filaments. The ordinary mode of conjugation in the Mesocarpaceae is that termed scalariform^ viz. between the several cells of two different fila- ments. In most species of Mesocarpus (Hass.) this takes place in the following way. When two filaments lie \^t\ near one another side by^ side, each cell of each filament puts out a short protuberance on the side facing the other filament. While these are forming, the greater part, but not the whole, of the endochrome in each cell passes into the protuberance thus formed, a portion being apparently always left behind As soon as the two protuberances meet, the cell-wall becomes absorbed at the extremity of each, and an open tube is thus formed in which the protoplasm of the two conjugating cells coalesces, with expulsion of cell- sap and consequent contraction into a globular zygosperm. The zygo- spenii is not formed in the centre of the short tube, but at one extremity of it. in contact with what may possibly be regarded as the female fila- ment, although the differentiation is doubtful, and in any case exceed- ingly slight. The zygosperm may be the result of the coalescence of three cells instead of two. The zygosperm is at once separated from the rest of the conjugating tubes, or from the mother-cells, by a septum on either side. In Staurospermum (Ktz.), where the cells are very long and narrow, four cells take part in the formation of each zygosperm. Two of the slender filaments, lying side by side, bend towards one another con- vexly so as to bring a part of each filament where there is a septum in contact. Both the septa and the longitudinal bounding-walls become absorbed at this spot, and the greater part of the contents of the four cells coalesce into a zygosperm, which is often of a more or less quadrate form, and is again sharply marked off from the four mother-cells by septa at the truncated corners. Lateral conjugation also takes place in some species of Mesocarpus between two adjacent cells in the same filament. In this process each of the two cells puts out a horn-like protuberance at the end adjacent to the other cell : these protuberances bend towards one COXJUGA T.-E 261 another and meet ; the septum between them disappears ; the endo- chromes of the two cells draw towards one another and coalesce, with condensation of the protoplasm, in the connecting tube thus formed (fig. 235). In ]M. neaumensis (Bennett, Journ. ISIicr. Soc, 1S86, p. 15) the Fig. i^-^.—Mesocarpiis par^mlus Hass. ; stages in the formation of zj-gosperm ( >< 750)- (After de Bary.) Fig. 234. — Staurospermuvi gracilliinmn Hass., with quadrate zygosperms, showing axile plate of chlorophyll in the cells which have not conjugated (x 400). (From) nature.) zygosperm is not formed in the connecting tube, but in one of the con- jugating cells. In Gonatonema (Wittr.) parthe?iosperms are said to be formed closely resembling zygosperms, but not resulting from the 262 ALG^E coalescence of the contents of two cells. Several species of Mesocarpus frequenth' put out long connecting tubes between two filaments, which assume a barrel-shaped form, but without any formation of zygosperms. In this condition they closely resemble Mougeotia (de By.). The most important point in which the Mesocarpacese differ from the Zygnemaceas is in the processes which take place after the formation of the true zygosperm. Immediately after its formation, it divides into two, three, or more cells, the central one only of which is fertile, ger- minating after a period of rest ; the other sterile cells, which are separated from the fertile cell by septa, taking no part in the germination. The germinating cell is therefore here a resting-spore or hyp?iospore, produced non-sexually, and the whole structure is, as Pringsheim points out, a rudimentary sporocai-p, indicating an approach to the higher classes of Alg^ ; while the family is, on the other hand, con- nected with the Zygnemacese through the species of Zygnema in which the zygosperm is formed in the connecting tube; and the best writers are by no means agreed as to the limits of the two orders. Wittrock has described the formation of the 'spo- rocarp ' as taking place in three different ways in the Mesocarpacese, viz.: — (i) By the tripartition of the zygosperm into a hypnospore and two sterile cells ; when the conjugation is lateral, the sterile cells are not separated from one another by the hypnospore, but are permanently united with one another. (2) By quadripartition of the zygosperm ; this has been observed only in the case of scalariform conjugation, the sterile cells being arranged two on one side and one on the other side of the hypnospore. (3) The zygosperm is cruci- form or H -shaped, and the sporocarp is formed from it by quinqueparti- tion, two sterile cells bounding the h}^nospore on each side ; this mode also only takes place in scalariform conjugation. Although these characters have been used by Braun and others for the separation of the genera of ]\Iesocarpace£e, Wittrock regards them as of very little systematic value, since in one species, Mougeotia calcarea (Wittr.), he observed all three modes of reproduction on one and the same fila- ment. In this same species Wittrock also records the formation of parthe?iosperj?is, precisely resembling the normal zygosperms, but not resulting from any act of conjugation. An outgrowth springs from a filament, but is not met by any corresponding outgrowth from an- other filament. It is, however, cut off by a septum, and divides into sterile cells and a hypnospore, just as if fecundation had taken place. Fig. 235. — Mcsoca7-pics plettrocarpus de tJy. ; lateral conjugation ( X 200). (From na- ture.) COXJUGA T.-E 263 In Gonatonema notabile (Wittr.) parthenogenetic hypnospores are formed by tripartition of the contents of an ordinary cell which swells up into the form of a cask. The phenomenon of reproduction in the ]Mesocarpaceae is regarded by some as a rudimentary appearance of an 'alternation of generations.' The sexual generation or ooph^te is completed by the production of the zygosperm as the immediate product of fecundation. This does not germinate directly, but its formation is immediately followed by cell- division, or the development of the non-sexual generation or sporophyte ; the sporocarp consists of the germinating h\^nospore — in the immediate formation of which no process of impregnation took part — and the in- vesting sterile cells or 'pericarp." Pringsheim, regarding the process of conjugation in the Mesocarpacese as representing a distinctly higher type than that in the Zygnemacese, divides the process in the former family into two stages. The first stage, to which he applies the term ' copula- tion,' consists in the simple union of two cells by the absorption of the dividing cell-wall ; the second stage is an intimate coalescence of the protoplasmic contents of the conjugating cells, effected by the motility of the chlorophyll-bodies ; and this stage he terms ' connubium.' The hypnospore might, indeed, be correctly termed a ' carpospore,' and we have here a point of departure in the direction of a much more highly specialised t}^e of structure. But the complete similarity of the two conjugating cells before conjugation necessitates the retention of the Mesocarpacese among the Conjugatce. Limiting the order in accordance with the above-named characters, the genera which the ^Nlesocarpacea^ comprise are Mesocarpus (Hass.), Staurospermum (Ktz.), Craterospermiim ('Br.), and Gonatonema (Wittr.). Several species of Mesocarpus and Staurospermum are not infrequent in stagnant water, especially in moor pools and among Sphagnum. The filaments are not so copiously invested with mucilage and not of so bright green a hue as those of the Zygnemacese ; Staurospermum capucinum (Ktz.) has a beautiful violet tinge. Literature. Wittrock — Algologiska Studier, Upsala, 1867 ; Oin Gotlands och Oelands Sotwas- seralger, 1872 (Quart. Journ. Micr. Sc, 1873, p. 123); On the Spore-formation of the Mesocarpece, 1878. 264 ALG.-F. \ M Order 2. — Zygnemace/E. The individual consists, as in the Mesocarpace^e, of a filament of cells placed end to end, which is almost always simple and unbranched. The filaments are cylindrical, and the cells of which it is composed often of comparatively large size ; those of Spirogyra crassa (Ktz.) as much as -^\-Q of an inch (125 /x) in diameter, and twice as long as broad. The chlorophyll is arranged in one or more straight (Siro- gonium, Ktz.) or more commonly spiral (Spirogyra, Lk.) bands, or in stars placed in pairs in each cell (Zygnema, Ktz.), or occasionally in an axile plate (Mougeotia, deBy.), and encloses large starch-grains and a nucleus, often very large and easily discernible even without the use of -staining reagents, connected with the parietal protoplasm by radiating threads. In some species ot Zygnema the characteristic appearance of the endo- chrome is assumed only when the cells are about to conjugate. The ease with which some members of this family, especially species of Spirogyra and Zygnema, are cultivated in fresh-water aquaria, and the beautiful arrangement of the endochrome, not only make these algae extremely striking objects under the microscope, but afford especially good opportunities for observing, in their details, the processes of division of the nucleus and of the cell.^ It is also in this family that the interesting process of conjugation is most easily followed. The filaments increase in length by ordinary cell- division ; and single cells, which become very easily detached, are able to develop in this way into new individuals, corresponding, therefore, functionally to the non-sexual spores of fungi. Like the Desmidiaceae and other floating algce, they can obtain their nourish- ment entirely from the water, and increase without any attachment to the substratum. The formation of resting-cells and of cysts has already been mentioned. The only other known mode of reproduction is by conjugation ; but the reproductive organs of other algje or fungi, which are sometimes parasitic upon or ^,i'i % i 'ff ->. 'iG. 236. — Spirogyra porticalis Vauch. ; stages in the forma- tion of zj-gosperm ( X 100). (From nature.) ' See Strasburger, Ueher Zelibildinig unci Zelltheilting % also Sachs, Text-book of Botany^ 2nd English cd. 1882, p. 16. CONJUGA T.E 20: endophytic in species of Spirogyra and Zygnema, have l^een mistaken for zoospores. The usual mode of conjugation is the scalariform, between the cells of two filaments lying side by side. The first stage is the putting out of lateral protuberances at right angles to the axis of growth, from the cells in each filament towards the corresponding cells in the other filament. The protuberances put out by opposite cells at length meet ; the proto- plasm-mass of each of the two cells has by this time begun to contract, withdrawmg itself from the cell-wall, and rounding itself off into an ellip- soidal form, with expulsion of some of its cell-sap, the chlorophyll- bodies at the same time losing their characteristic arrangement. The cell-wall then opens between the two protuberances, and the whole of the protoplasmic con- tents of one of the two cells passes through the connecting tube thus formed, and glides slowly through it into the other cell-cavity, coalescing with its pro- toplasm-mass. After complete union the combined protoplast is again ellipsoidal or spherical, and scarcely larger than each of the two before coalescence, further expulsion of water and conse- quent contraction having taken place. In some species of Zyg- nema the zygosperm is formed, not in either of the conjugating cells, but in the connecting tube, as in the Mesocarpaces. In Sirogonium no connecting tube is formed, but conjugation takes place by genuflexio?i ; the two filaments are brought into contact by a knee-like bend in each : at the point of contact the adjacent cells of the two filaments are placed in communication by the disappearance of the cell-walls, and a zygosperm is formed in one of the two cells by the coalescence of the two protoplasts. A second mode of conjugation, not nearly so frequent, is the lateral, between two conti^ruous cells of the same filament. Protuberances formed near the adjacent ends of contiguous cells bend tov.-ards one another till they meet : the cell- wall between them then disappears. Fig. 237. — Zygnevia pecti- nation As:., in conjugation ( X 1 00). (After Cooke.) Fig. 238. — Spiro- gyra belli s Hass. ; lateral conjuga- tion ( X 100). (From nature.) 266 ALGjE. and conjugation is effected though the curved tube thus formed by the coalescence of the protoplasts of the two cells. The zygosperm is never formed, as in the Mesocarpaceae, in the connecting tube, but in one of the two cells. Lateral conjugation frequently takes place with groups of four cells, the zygosperms being formed in the two central ones. The protoplast formed by either mode of conjugation finally secretes a cell-wall of cellulose, and becomes a zygosperm. Germination some- times takes place while still within the mother-cell ; but most commonly both filaments perish after conjugation, with the exception of the numerous zygosperms, which fall to the bottom, the green endochrome having in the meantime turned to a brick-red colour. It then remains dormant through the winter as a resting-cell or hypnosperm, germinating in the spring. Whether the axis of growth of the new individual is parallel or at right angles to that of the old individual is differently stated by different observers. On the commencement of germination, one end of the zygosperm of Spirog}Ta attaches itself like a root to a stone or to some other alga, so that in the earliest stage of the new individual there is a differentiation between base and apex ; but this soon disappears. The innermost of the three layers of which the cell- wall of the hypnosperm is composed bursts through the other two, and protrudes like a bag. The chlorophyll then arranges itself in spiral bands, with starch-grains within them, and the cell divides by transverse septa into a filament, all the cells being from this time precisely alike. Instances are recorded of filaments persisting through the winter. Hofmeister states that the growth of Spirogyra is intermittent, and that the filaments exhibit a nutation, due probably to differences in the rapidity of growth of different sides of the same cell. Where branching takes place, it appears to be confined to the barren portion of a filament in which z}'gosperms have been formed. Although the view is contested by some writers, the process of conjugation is regarded by most as a sexual process, but one of the most rudimentary character, the differentiation of the two conjugating elements being exceedingly slight. As de Bary has pointed out — and his statement is confirmed by nearly all more recent observers — the direction of conjugation is clearly governed by some physiological law, the movement of the protoplasm between the two filaments almost invariably taking place in one direction only, so that one of the two conjugating filaments is entirely emptied, while the other is filled with zygosperms.^ Designating the former as the male and the latter as the female filament, it is frequently the case that the cells of the > Hassall, however, asserts and figures the contrary {^British Fresh-water Alg(£y i., p. 130). CON JUG A T.^ 267 female are both longer and broader than those of the male filament ; and the contraction of the protoplasm has been observed to begin earlier in the male than in the female filament. It is also stated that the protuberance from the female cell is shorter but broader than that of the male cell, the latter fitting into the former as into a socket. The chief argument against the sexuality of the filaments is the occurrence of lateral conjugation ; and when this takes place a sexual differentiation can be assumed only of the individual cells and not- of the filaments ; but that there is some differentiation of this kind would appear from the fact that when lateral conjugation takes place in a group of four cells the zygosperms are formed in the two centre cells, which may be regarded as female. The phenomena may then be compared to those in Sphaeroplea. Bessey states {in lit.) that scalariform and lateral conju- gation may sometimes be seen in different parts of the same filament. The female filaments are, as a rule, very much more abundant than the male ; and it is not uncommon for conjugation to take place between one male and several female filaments, while the reverse is at all events much more rare. Occasionally one cell will conjugate with two others^ the zygosperm being then the product of one female and two male cells. Several instances are recorded of hybridism between two different species of Spirog}Ta. Parthenogenesis, or the formation of parthe?ios_per??is capable of germination, and in all respects resembling zygosperms, but formed out of the contents of a single cell without any previous process of conjugation, is also stated to occur. The genera included in the Zygnemacege with the above characters are Zygnema (Ktz.), Spirogyra (Lk.), ]\Iougeotia (de By.), Sirogonium (Ktz.), and Zygogonium (Ktz.). Several species of Spirogyra and Zygnema are among the commonest of fresh-water Algse in both stagnant and running water, forming dense bright green masses, often with a slimy feel, owing to the well-developed mucilaginous sheath in which each filament is enveloped. While conjugation is in active progress, which is mostly in the early summer, the filaments of Spirogyra assume a dull green or even brown colour, easily recognised by the naked eye. The other genera are more frequent in moor pools. Literature. Pringsheim — Flora, 1852, pp. 465 et seq. . Cleve — Monografi Zygnemaces, 1868. Hofmeister — Wiirtemb. naturw. Jahresheft, 1874, p. 21 1. Overton— Ber. Deutsch. Bot. Gesell., 1S88, p. 68. (For fuller bibliography see Bennett, Journ. Linn. Soc, xx. , 1SS4, p. 430)- 268 ALGAL Order 3. — Dp:smidiace.^. The Desmids are unicellular organisms, for the most part solitary, and inhabiting almost exclusively fresh water, especially stagnant, where they occur in very large numbers ; a very few species are brackish. They always float free without any attachment to the bottom or to other algae, and many species possess a power of apparently spontaneous motion through the water similar to that of diatoms, though not so strongly marked. In several genera, as Desmidium (Ag.) and Hyalotheca (Ehrb.), the individuals are united into long filaments; and either the separate individuals or the filaments are invested by a more or less dense mucilaginous envelope, species of Desmidium and Hyalotheca frequently forming a green slime on the surface of moor pools. The origin and structure of the mucilaginous sheath appear to be the same as in the Zygnemacese. According to Hauptfleisch, the cell-wall of desmids always consists of two distinct layers, sometimes of more, which are then provided with a girdle-band similar to that of diatoms. He also states that in nearly all species the cell-membrane is perforated, and that through these pores proceed threads of protoplasm, connecting the protoplasm in the interior of the cell with the gelatinous envelope which is excreted through the pores from the cell-contents. In the filamentous species the protoplasm is probably in connection throughout the filament. The cells vary greatly in size and form in different species, the largest (Cosmarium, Cord., Micrasterias, Ag.) being just visible to the naked eye. The individual is usually divided by a deep constriction into two symmetrical halves ; and even where this is not the case, the cell- contents — chlorophyll-bodies and starch-grains — are symmetrically arranged in the two halves of the cell. The cell-wall is smooth, or punctated, warty, or even elevated into spines, but has no (or very little) deposit of silica. The cells contain a large quantity of chlorophyll of a bright green colour, never concealed by any pigment, often arranged in bands or stars, and containing much starch. Each genus has its own general form of cell, often of very great beauty. In Docidium (Breb.), Penium (Breb.), and Tetmemorus (Ralfs) the individual or ' frustule ' is elongated, cylindrical, and usually divided by a constriction into two halves placed end to end; in Closterium (Nitzsch) it is crescent- shaped; in r^Jicrasterias it is very thin and flat, usually with a more or less orbi- cular or elliptical outline, deeply divided into two symmetrical halves, and each half more or less deeply lobed ; in Euastrum (Ehrb.) the indi- vidual is usually smaller than in Micrasterias, often very minute, and CONJUGA TyE 269 the half-cells have a smooth, sinuate, or beaked margin, with circular in- flated protuberances ; in Cosmarium the half-cells are quite undivided, and the whole outline often nearly orbicular; in Xanthidium (Ehrb.) and in most species of Staurastrum (Mey.) the surface is elevated into prominent tubercles or spines. The transparency of the cell-wall in desmids enables the rotation of the protoplasm to be distinctly seen ; and at the colourless spaces at the extremities of some species of Closterium and Docidium the dancing 'brownian' movement of particles suspended in the cell-sap is ven,' Fig. 239. — A, Desmidinvi Sivnrtzii Ralfs ; B, Jlicrasferias rotata Grev. ; c, Euastruin rostratmir Ralfs ; D, Cosinarhcm coelatunt Ralfs ; t., Xatithidinni cristatum Br^b. ; f, Sta7irastr7ijn Arachnc Ralfs ; G. Closterium DianceKhrh. ; h, Docidium baciduin Br^b. (All after Ralfs and variously magnified.) evident. Klebs describes four kinds of movement in desmids, viz. : — (i) A forward motion on the surface, one end of each cell touching the bottom, while the other end is more or less elevated and oscillates backwards and forwards ; (2) an elevation in a vertical direction from the substratum, the free end making wide circular movements ; (3) a similar motion, followed by an alternate sinking of the free end and elevation of the other end; and (4) an oblique elevation, so that both ends touch the bottom — lateral movements in this position ; then an elevation and circular motion of one end, and a sinking again to an obhque or horizontal position. These movements are, according to this observer, all due to an exudation of mucilage, and the first two to the 270 ALG.'E broadening of the isthmus formation, during the motion, of a filament of mucilage by which the ■desmid is temporarily attached to the bottom, and which gradually lengthens. The movements of desmids are especially vigorous when they are in the act of dividing. Stahl found that, like the movements of zoospores, they are affected by light. Vegetative propagation takes place by division or fission, a process which can be easily followed out in species of Cosmarium or Staurastrum, the whole being completed in the course of a few hours. When cell- division is about to commence, the endochrome retreats slightly from the band or ' isthmus ' which connects the two half-cells with one an- other; and the two halves then separate from one another, retaining their connection only by a transverse band formed by the gradual this is after a time divided into two by a septum along the length of the isthmus, midway between the two half-cells and parallel to the constriction between them. The endochrome now passes out of each original half-cell into the half of the band in connection with it, and at the same time the half-band bulges, and, growing rapidly, assumes the form and appearance of an original half- cell. Fresh formation of chloro- phyll is at the same time taking place in it, and the half-band becomes a complete half-cell, but some- times slightly larger. We have now two individuals attached to one an- other by their larger halves ; these frequently remain in contact for a considerable period, but at length separate. In the spiny species of Staurastrum the spines are developed very rapidly on the half-bands while their development into half-cells, is progressing. A sexual process of conjugation takes place in the following way in the genera where the individuals are quite distinct. Two individuals — which cannot in any way be differentiated as male and female — lay them- selves either parallel to or across one another, and the pair become en- veloped in a common mucilaginous coating. In each individual the outer of the two layers of which the cell-wall is composed gives way, and a circular opening is formed at the constricted part ; the inner layer of the cell-wall of each individual protrudes through the opening in the form of a bladder, and these two protrusions come into contact. The outer cell-wall is then thrown off, and the wall separating the two con- Fic. 240. — Staiirastriivi telifcrjun Ralfs, dividing (x 400). (From nature.) CONJUGAT.E 271 jugating protrusions disappears. The two protoplasmic bodies then unite in the conjugating tube thus formed into a nearly spherical zygo- sper?fi, enclosed in a cell-wall which ultimately becomes differentiated into three layers, the innermost and outermost of which are colourless, while the middle one is firmer and brown. The outer surface remains in some species smooth, while in many it becomes, w'hen mature, covered with warts or spines, which are not unfrequently barbed. In those genera where the individuals are associated into filaments, conju- D Fig. 241. — Zygosperms of desmids. a, Euastrum pectinaUnn Brdb. (x 400). b, Penhim inargaf-itacejun Brdb. (x 300). c. Closteruim rostratmn Ehrb. early stage (x 200). d, Dt'SfnidiuKt Swartzii Ralfs ( x 600). (All after Ralfs.) gation takes place betw-een the cells of different filaments, and a large number of zygosperms may frequently be seen in the same fila- ment. In Gonatozygon (de By.), where the cells are very long and slender, the process is very similar to that in Zygnema. The state- ment of the occurrence of zoospores in the Desmidiaceae is founded on erroneous observation, the antherozoids of parasitic fungi having pos- sibly been mistaken for zoospores. After remaining for a considerable time at rest, the zygosperm ger- minates by the bursting of its two outer coats, the protoplasmic contents escaping still enveloped in the very thin innermost coat. In this embryo. 272 ALG.-E as it may bu termed, the protoplasm and chloroph\ll-corpuscles are already distributed symmetrically into two half-cells, which contract somewhat, and the whole becomes invested by a new cell-wall. A con- striction has in the meantime made its appearance between the two halves, and the new individual rapidly assumes its mature form, but is at first of small size. It soon divides repeatedly, and each generation gradually increases in size until the full size is attained. The number of known species of desmids is not large compared with that of diatoms ; they are found in great abundance in the midst of larger algae in fresh water, especially in moor-pools, sometimes forming a green scum on the surface. Literature. Ehrenberg — Die Infusionsthierchen, 1838. Ralfs — British Desmidieae, 1848. Nageli — Gattungen einzelliger Algen. 1849. Stahl — Verhandl. Phys. -med. Gesell. Wlirzburg, 1880, p. 24. Fischer — Bot. Zeit. , 1883, pp. 22^ ei seq. Wolle— Desmids of the United States, 1884. Klebs— Biolog. Centralblatt, 1885, p. 353. Cooke — British Desmids, 1887 (which see for further l:)ibIiography). Hauptfleisch — ZeHmembran u. Hiillgallerte der Desmidiaceen, 1888. Class XV.^Confervoideae Isogamse. In this class the individual still consists of a filament of cylindrical cells, placed end to end, which may be branched or unbranched. As in the Conjugatae, the only known sexual mode of reproduction is an isogainous one between two masses of protoplasm, which are not clearly differentiated beforehand into a male and a female element ; but the conjugating bodies are not the contents of stationary cells, but are motile ciliated swarm-spores or zoogametes^ produced by free-cell forma- tion in ordinary or in slightly differentiated cells of the filament, hence termed gametanges, their conjugation resulting in the production of a zygosperm. The filament increases in length by the repeated transverse septation of successive apical cells, or less often of intercalary cells. The ordinary mode of multiplication is a non-sexual one, by means of naked ciliated zoospores., closely resembling the zoogametes, but often larger, and formed singly or in pairs in a cell. Vegetative propagation also takes place by the formation and detachment of cysts or resting- cells, which may be either akinetes or aplanospores. The cells verv frequently display a plurality of nuclei, but this is not nearly so strongly CONFERVOIDE.E ISOGAM.E ^73 marked as in the unicellular Multinucleatae. The class includes one large order, the ConfervacecB, and three smaller ones, the Ulotrichacece, FithophoracecE, and Chroolepidece^ though the boundaries between them are not in all cases well defined. In the Confer\-ace8e and Ulotrichaceae the filament which springs from the germination either of a zoospore or of a zygosperm resulting from the conjugation of zoogametes, attaches itself to the substratum — a stone, another alga, or some other aquatic plant — by a rhizoid, which may consist of a single cell, or may branch into a number of cells. As in the higher algae, the rhizoid is not a nutritive organ, but simply an organ of attachment. These algae may, however, continue to grow and retain their vitality for a long period in water without any attachment to the substratum. Order i. — Confervace.^ (?>/^/?^^/-^^ Ch.etophorace.^). The term Confervacese has been very vaguely applied to a variety of green fresh- water organisms, but is now limited to a comparatively small number of genera of fresh-water, and a few brackish and salt- water algje, in which each individual consists of a segmented branched or un- branched filament of cylindrical or disc- shaped cells, invested by a mucilaginous sheath, and in which multiplication takes place non-sexually by 7)iegazoospores^ or sexually by the conjugation of smaller zoogametes. Both kinds of swarm-cell have two cilia, or the former in some cases four ; Lagerheim describes, in Conferva bombycina (Ktz.), megazoospores with a single cilium. From each parent-cell are produced either one or two megazoospores. In only a few species has the process of conjugation of zoogametes been actually observed, and the systematic position of a large number of the species is therefore at present only conjectural. Areschoug has followed both the conjugation of the zoo- gametes and the direct germination of the megazoospores in Urospora (Aresch.). In Conferva (L.), Chaetophora (Schr.), Draparnaldia (Ag.), and some other T Fig. 242. — Microspora Jloccosa Thur. A, B, portions of filament. C, fila- ment dividing for the escape of zoo- spores. Z>, zoospores (x 300). (After Cooke.) 274 ALGA£ Fir.. ■2i,->,.—Clndophora gracilis Ktz. a, natural size b, upper, f, lower portion (x 2co). (After Hauck.) genera, vegetative propagation takes place by means of resting- spores or cysts^ usually found in swollen barrel-shaped cells. In Conferva the resting-cells may be either akinetes or apla- nospores ; and Wille believes that they are produced espe- cially under circumstances un- favourable for the formation of zoospores. The resting-spores of Confervacese are formed in three different ways: either (i) by rejuvenescence, and the for- mation of a new cell-wall round the contracting contents; or (2) by separation of a portion of the cell-substance so as to form a swollen part of the mother-cell, and the thickening of the cell- wall at this portion; or (3) by the simple thickening of the wall of the mother-cell. In the formation of aplanospores, one, two, or four proceed from a single cell by the cell-contents rounding off and enclosing themselves in a cell-wall while still within the parent-cell. They hibernate within the parent-cell, and germinate in the spring. Resting swarm - cells, naked masses of protoplasm endowed with an amoeboid power of mo- tion, are formed in the same wa)'. The mucilaginous sheath of the Confervaceae appears to have the same construction as in the classes of algae already described, but is often but feebly ' developed. Wille states that the CONFERVOIDE.E ISOGAM.-E 275 spores put out an organ of attachment even before they germinate. In Chaetophora and otlier genera which make up the Chaetophoracese of Hassall, the terminal cell of the main axis or of its branches is prolon^^ed into a colourless hyaline bristle. These are especially well developed in Draparnaldia, an exceedingly beautiful organism not uncommon in Fig. -zjf^.- Draparnaldia gloiiierata Ag. (^x. 100). (From nature.) freshwater, which exhibits a somewhat higher type of development than the other genera, being differentiated into an axis or central tube, and smaller secondar)^ branches arranged in regular whorls ; the zoospores being produced in the latter only. Maupas states (Compt. Rend., Ixxxix., 1879, p. 250) that the cells of Cladophora contain a large number of nuclei ; and Schmitz (Sitzber. Xiederrhein. Gesell., 1879) finds four nuclei in a T 2 276 ALG^ cell in certain conditions of Conferva. In this, and in the possession of proteinaceous crystalloids (Klein, Bot. Zeit., 1880, p. 782), these genera show an affinity to Siphonocladace^e. Binuclearia (Wittr.) (Bot. Centralbl., xxix., 1887, p. 60) appears to have always two nuclei in each cell. There are still many points to be cleared up in the life-history of the Confervaceae, although some of the genera are among the most abundant of fresh-water organisms ; and the bounds and systematic position of the family are still uncertain, x-lccording to some observers, many of the species are connected genetically with forms at present placed under the Protophyta ; to this view further reference will be made hereafter. Andersson (Bot. Centralbl., xxxv., 1888, p. 351) believes Palmella uvasformis (Ktz.) to be a resting condition of Draparnaldia. Among the genera now included in the order are Conferva (L.), Micro- spora (Thur.), Cladophora (Ktz.), Rhizoclonium (Ktz.), Stigeoclonium (Ktz.), Chaetomorpha (Ktz.), Draparnaldia (Ag.), Chaetophora (Schr.), Urospora (Aresch.), and Binuclearia (Wittr.). Phseothamnion (Lagerh.) (see under Syngeneticas) ought possibly to be included here; as also Spongocladia (Aresch.) (see p. 290). Several species of Cladophora, Chjetomorpha, and Rhizoclonium grow in brackish or even in salt water. Literature. Vaucher — Hist, des Conferves d'eau douce, 1803. Arescboug -Nova Act. Reg. Soc. Upsala, vi., 1868, and ix. , 1874. Reinhardt— Arb. Naturf. Gesell. Charkoff, 1876. Wille — Bot. Centralbl., xi., 1882, p. 113; and Pringsheim's Jahrb. wiss. Bot., 1887, PP- 437, 459, and 492. Lagerheini— Ber. Deutsch. Bot. Gesell., 1887, p. 409. Murray and Boodle — (Spongocladia) Ann. of Bot., ii., 1888, p. 169. Order 2 (?).^Pithophorace.'E. The Pithophoraceae must be admitted as a distinct order only with very great doubt, both because the mode of sexual reproduction is at present unknown, and because of their strong resemblance to the Con- fervace^. The family, consisting of a single genus, was founded on Pithophora Kewe?isis Wittr., an inhabitant of warm tanks in the Botanic Gardens at Kew, Oxford, and elsewhere ; other species have since been found in tropical America. The thallus is composed of branching filaments of cells resembling Cladophora, but increasing only by bipartition of the terminal cell, and presenting here and there barrel- shaped cells very rich in chlorophyll, in which are formed resting-spores of non-sexual origin. These germinate directly, and in opposite direc- tions, from the two apices. There is another mode of non-sexual pro- pagation by ' prolific cells ' ; but no zoospores nor any sexual mode of COXFERVOIDE.E ISOGAM.-E 277 reproduction have as yet been detected. They are distinguished by the remarkable development of their rhizoids or organs of attachment. Literature. Wittrock — On the Development and Systematic Arrangement of the Pithophoraceae, 1877. Order 3. — Ulotrichace.^. This small order includes the genera Ulothrix (Ktz.). Hormiscia (Aresch.), and perhaps one or two others, not uncommon in fresh and occasionally in brackish water. The life-histor}' of U. zonata (Ktz.) and other species has been investigated by several observers. They exhibit consider- able affinity both to the Confervaceae and to the Hydrodictyeae. Each individual is composed of an unbranched filament of short cells, broader than long, and nearly uniform in len2:th. Some of the cells are viegasporanges. giving birth to 2, 4, or 8 megazoospores with 4 cilia : others are microsporanges or game ta?iges, producing 16 or 32 biciliated microzoospores or zooga- metes. From the non-sexual megazoo- spores to the zoogametes there is, however, a gradual transition, the only constant dif- ference between them being the number of cilia. Those microzoospores which do not conjugate, as well as the megazoo- spores, germinate directly, germination sometimes taking place even within the mother-cell. Their escape is, however, sometimes arrested, when they lose their cilia, mvest themselves with a thick cell- wall, and assume a palmelloid condition. The plants which spring from the germina- tion of the megazoospores are larger than those which spring directly from the micro- .^ Fig. 245. — Pithophora Keivensis Wittr., branching plant ; sp, spore (x- 20). (After Wittrock.) 278 ALG.'E zoospores, as also thaii those which si)ring from the zygosperms resulting from the conjugation of the zoogametes. The escape of the swarm-spores was observed by Cramer to take place, usually in the morning, even in water which froze on the surfoce every night, conjugation following quicklv afterwards. The two kinds of swarm -spore are never produced in the same cell, but in different cells of the same filament, and Cramer believes that conjugation takes place between zoogametes from the same filament. The megazoospores use up in their formation the whole proto- plasmic contents of the mother-cell, while in the production of the Fig. 24,6. — Ulothri.x hnplexa Ktz. a, vegetative filament (x 4S0) ; b, portion of the same (x 800) ; c, palmella-condition ( x 480) ; d, esjape and conjugation of zoogametes (x 8od). (After Dodel -Port.) microzoospores or zoogametes a portion of the contents forms a bladder which escapes with them, but soon perishes. According to Wille (Bot. Centralblatt, vol. xi., 1882, p. 113) Ulothrix also produces cysts or rest- ing-spores, which may be either aplanospores or akinetes. In some other members of the order the filament is branched. Schaarschmidt points out that a state closely resembling the microsporiferous filaments of Ulothrix occurs in the development of the Confervaceae ; and CONFERVOIDE.E ISOGAM.E 279 Hansgirg (Bot. Centralblatt, 1885) believes that the filamentous genera placed in this genus are connected genetically with forms classed under the Chaetophoracese, Siphonocladacese, and Ulvaceae. To this order belong also Hormidium (Ktz.) and Schizogonium (Ktz.). "Wildeman (Bull. Soc. Bot. Belg., 1886, p. 7) traces a genetic connection between Ulothrix and Pleurococcus. Literature. Cramer — Vierteljahrschrift Nat. Gesell. Zurich, 1870. Cienkowski — Mel. biol. Bull. Acad. St. Petersbourg, 1876, p. 531. Dodel-Port — Pnngsheim's Jahrb. wiss, Bot., 1876, p. 417; Bot. Zeit., 1876, p. 177. Gay — Bull. Soc. Bot. France, 1S88, p. 65. Hansgirg — Flora, 1888, p. 259. Order 4. — Chroolepide.^. This order, as constituted by Borzi, comprises a small group of algae found on damp walls, the trunks of trees, and similar situations, not unfrequently imbedded in the thallus of lichens, or constituting their gonidial element. The thallus consists of a branched or unbranched filament of cells, usually somewhat rounded or mo- niliform in outline, and is distinguished by the mask- ing of the colour of the chlorophyll by a golden yellow, orange, or red oily pigment, soluble in alcohol and imparting a strong odour of violets. This pig- ment, which occasionally occurs also in other lowly organised algae and proto- phytes, has been examined by Rostafinski, and found to be a derivative of chlo- rophyll to which he gives the name chlororufi?i. Microzoospores or zooga- metes and megazoospores are produced in gametanges or zoosporanges, which are indistinguishable from the vegetative cells except by their somewhat larger size, and which are either terminal or intercalary. Conjugation of the Fig. 247. — Tt-cntepohlia Bleischii Rbh, A, filament with swollen cells in which the zoogametes are formed (game- tanges), g; B, stages in the conjugation of the zoogametes ( X 330). (After Wille.) 28o ALGjE smaller swarm-spores has been observed in Chroolepus (Ag.), but they can also germinate without conjugation. Chroolepus also produces resting- spores. Of this genus one species, C. aureum (Ktz.), is common on walls and rocks, and another, C. umbrinum (Ktz.), occurs on the bark of trees, C. lolithus (Ag.) is one of the few algae that grow in perfectly dry situations on gneiss belonging to the Flagellate Infusoria. Under the name of Scyamina, Van Tieghem (Bull. Soc. Bot. France, 1880, p. 200) describes a singular blackish organism found on the surface of ponds, which he regards as a genus of A^olvocine^e destitute of chlorophyll. 296 ALG^E Literature. Ehrenberg — Die Infusionsthierchen, 1838. Busk — Trans. Micros. Soc. , 1853, u. 31. Cohn— Jnhrber. Schlcs. Gesell. , 1856, p. 237 ; and Beitrage, i,, 1S75, ^^^t 3, p. 93 (Pop. Sc. Rev., 1878, p. 225). Carter— (Eudorina) Ann. Nat. Hist., 1858, p. 237 ; and 1859, p. i. Braun— Bot. Zeit., 1875, p. 189. vStein — Der Organismus der Infusionsthiere, part iii., 1878. Henneguy— Journ. d. Micrographic, 1878, p. 485. Maupas — Compt. Rend., Ixxxix., 1879, p. 129. Kirchner in Cohn's Beitrage, iii., 1879. OrDExR 2. — Hydrodictye.'E. The relationship of the Hydrodictyese to the other famihes of Coeno- bieae is somewhat obscure. They differ from them in the form of the coenobe, which, instead of being minute and globular, ellipsoidal or tabu- lar, is of considerable size, and presents the appearance of a net. The only known mode of reproduction is by the conjugation of zoogainetes. As here constituted " the order is limited to the single genus Hydro- dictyon Roth, one species of VN'hich is moderately common in ponds and ditches, and is known under the naiTie of ' water-net.' When the plant is iTiature, the coenobe consists of a sac-like net several centimetres in length, composed of a great number of cylindrical cells united at their ends so as to form a 4- or 6-cornered mesh. The ordinary inode of pro- pagation consists in the protoplasm of one of the cells breaking up into from 7,000 to 20,000 megazoospores^ each furnished with four cilia, which move about with a trembling motion within the zoosporange, come to rest in the course of half an hour, and then arrange themselves in such a way that, by their elongation, they again form a net of the original kind, which is set free by the absorption of the wall of the mother- cell, and attains, in the course of three or four weeks, the size of the mother- colony. In other cells of the mature net the protoplasin breaks up into from 30,000 to 40,000 smaller swarm-cells or zoogainetes^ furnished with only two cilia, which at once leave the gametange and swann about for some hours. Conjugation between these has been observed to take place even within the gametange, more than two sometimes uniting together. The resulting zygosperm retains its green colour, and invests itself with a firm cell-wall. After remaining for several months at rest as a hypnospenn^ it begins to grow slowly, and, when it has attained a considerable size, its contents break u]) into two or four mega- zoospores, which come to rest after a few minutes, and assume a pecu- liar angular form when they have attained a considerable size, putting out horn-like appendages. In each of these polyhedra the green parietal CCENOBIE.E 2[)7 protoplasm again breaks up into zoospores, which swarm about for twenty or forty minutes within a sac which protrudes out of the protoplasm. When they come to rest, they arrange themselves within the sac into a small net consisting of from 200 to 300 cells, which gradually grows to 0^%ei Fig. 260. — Hydrodictyon utriculatum Roth. A, net (natural size). B, mesh (x lo), C, megjazoo sporange ( x 300). D, megazoospores ( x 600). E, gametange with zoogametes ( x 300). (After Cohn.) one of the ordinary size. In some of the polyhedra smaller and more numerous microzoospores are formed ; but they also appear to unite again into a net without displaying sexual functions. Literature. Nageli— Gattungen einzelliger Algen, 184^9, p. 92. Braun — Verjungung in der Xatur, 1851 (Ray Soc. , Bot. and Phys. Mem., 1S53) ; and Algae unicellulares, 1S55. Pringsheim — Monber. Berl. Akad. , i860, p. 775 (Quart. Journ. Micr. Sc. , 1S62, pp. 54 and 104). 298 ALG.E Order 3. — Pediastre.e. The Pediastrese are most nearly allied to the Hydrodictyeae in their mode of reproduction. Of the typical genus Pediastrum Mey., several species are very common in fresh water, whether stagnant or running, attached in the form of minute (usually microscopic) discs to other algae or water-plants, or swimming free. Each disc is of a regular symmetrical "<4 Fig. 261. — PediastrujH integ"2iin Nag. A, younger, B, older coenobe ( x 300). C, portion of older coenobe showing resting-cell, y (x 600). (From, nature.) form, usually elliptical, and consists most often of 8, i6, or 32 cells, or some larger number which is probably always, when perfect, a power of two. The coenobe is invested in a ven,^ thin gelatinous envelope, and the peripheral cells have commonly horn-like or crescent-shaped appen- dages. Pediastrum is multiplied either by non-sexual propagation or by sexual reproduction. In the former case one of the ordinary vegetative cells becomes a zoosporange, its protoplasm breaking up into a number of nearly globular megazoospores each furnished with two very fine and inconspicuous cilia, which, after swarming about for a time, lose their cilia and arrange them- selves in the form of a plate, which then escapes from the zoosporange in- vested in mucilage, and develops into a new Pediastrum-disc. Others of the cells become gametanges, the contents dividing in the same way into zoogametes of an ovoid or pear-shaped form, which conjugate after escaping separately from the mother-cell, but apparently only with those from other gametanges. The peripheral cells of the ccenobe appear to have a tendency to develop into resting-spores. A Fig. 262. — A, polj'bedra of Pediastrinn ( ^ 55o)' B, formation of Pediastriini- disc within polyhedra ( x 550). (After Askenasy.) CCEXOBIE.-E 299 Askenasy has observed the development of the Pediastrum-coenobe by another method from the polyhedra form, previously regarded as a distinct genus under the name Polyedrium (Xag.). In this form each individual consists of a minute flat angular cell often provided with spines or hook-Hke processes. From this a Pediastrum-disc is developed in precisely the same way as from a Pediastrum-cell. The cell-contents break up into a number of megazoospores, which escape in the form of a plate after swarming about for a time ; then, losing their cilia, and placing themselves in a plane side by side, develop into an ordinary Pediastrum. Reinsch, on the other hand (Notarisia, 1888, p. 493)> regards Polyedrium as the type of a separa::e family of Palmellacese. Literature. Xiigeli — Gattungen einzelliger Algen, 1849. Braun — Verjiingung in der Natur, 1851 (Ray Soc. , Bot. and Phys. Mem., 1853) ; and Algee unicellulares, 1855. Lagerheim — Bot. Centralbl. , xii. , 1882, p. 33. Askenasy— Ber. Deutsch. Bot. Gesell. , 188S, p. 127. Order 4. — Pandorixe.e. In the higher genera of this order, Pandorina (Ehrb.), Gonium (^iliill.), and Stephanosphaera (Cohn), the individual is a spherical or tabular coenobe, the cells of which are united together by a gelatinous matrix with a definite bounding-wall. With them are associated also some unicellular organisms, Chlamydococcus (A. Br.) and Chlamydomonas (Ehrb.), which may possibly be connected with them by a process of degeneration. Whether isolated or associated, each cell possesses a pair of whip-like vibratile cilia attached to the anterior pointed end, by means of which it is rapidly propelled through the water : in the case of the social genera these cilia project through the common gelatinous envelope of the colony. ^Multiplication takes place either non-sexually by simple subdivision of the cells of a colony, or sexually l^y the union of two (or occasionally more than two) zoogauietes into a resting zygo- sperm. A characteristic feature of the family is the formation of a colony of cells within each cell in the mother-colony. The organisms here included were described by Ehrenberg as constituting a family of Infusorial Animalcules. They live, associated with larger algae, in fresh water, running or stagnant, often in such quantities as to impart to it a green colour. The family closely approaches Volvocineae through Eudorina. Of the unicellular Pandorincce Chlamydomo7ias Ehrb. may be taken as a type. In the form in which it is known under this name, it 300 ALG^^ •consists simply of a single motile primordial cell, in (;ther words, of a zoospore or swarm-cell. These are megazoospores, half as long again as broad, each with two contractile vacuoles, a lateral red pigment-spot, and two long cilia ; in the posterior half is a nucleus. After the con- clusion of the period of swarming, these zoospores become invested with cellulose, and, after a long period of rest as hypnospores, multiply non-sexually by division into four — less often into two. According to Rostafinski sexual reproduction takes place by one of these mega- zoospores dividing, by successive bipartitions, into eight daughter-cells, Avhich are then microzoospores — or, more correctly, zooga7netes. These have a longish almost elliptical form, and a light green colour, one nucleus, a red pigment-spot, and four cilia. They are distinguished from the true zoospores, not only by their smaller size, but also by the large colourless extremity in place of the two contractile vacuoles. They swarm out, and soon begin to conjugate in pairs, coming into contact by their colourless extremities, and coalescing into a single cell, the ends which bear the cilia at the same time rounding off and approxi- mating. This body has now eight cilia and two lateral pigment-spots ; ultimately the eight cilia disappear, and a zygosperm is formed, which multiplies by simple division without swarming. Dangeard finds in Chlamydomonas pulvisculus (Miill.)a differentiation of male and female gametes, the latter being considerably larger than the former. In C. Morieri (Dang.) he describes a peculiar mode of conjugation of zooga- metes, \vhich he compares to that of Spirogyra. Chlajiiydococcus A. Br. presents a similar life-history ; and, according to some observers, the organisms known as Pleurococcus, Gloeocystis, and others usually included under Protococcacese, are identical with the resting conditions of Chlamydomonas ; and, under suitable conditions, can be made to produce biciliated zoospores with two contractile vacuoles and a nucleus. Under the Volvocinese, and near to Chlamydomonas, Dangeard (Ann. Sc. Nat., vii., 1888, p. 105) and Stein include also Chlorogonium (Ehrb.). Among the most interesting of the social Pandorine?e is Pandorina Ehrb.. Each family or coenobe consists of sixteen cells closely crowded together, and surrounded by a thin gelatinous envelope through which the cilia protrude. Non-sexual multiplication is preceded, after the colony has come to rest, by the absorption of the cilia in the sixteen cells, each of which then breaks up into sixteen smaller cells ; and these sixteen daughter-families are set free by the absorption of the gelatinous envelope of the parent-colony ; each becomes itself invested by a gelatinous envelope, and grows to the size of the original parent-colony, CCEXOBIEyE ;oi having in the meantime developed two cilia from each of its cells.. Sexual reproduction takes place in the following way. Sixteen daughter- families are first of all formed in the same manner, but the gelatinous envelopes of the young colonies deliquesce, and the separate 256 (= 16 X 16) swarm-cells are set free as zoogametes. These vary in size, but are always rounded and green at the posterior end, pointed hyaline and with a red pigment-spot in front, where they bear two cilia. Among the crowd of these swarm-cells — now swimming about freely — some, irrespective of their relative size, approach one another in pairs, their pointed anterior apices coming into contact, and they finally coalesce into a body which has at first somewhat the shape of an hour-glass, but gradually contracts into a sphere, in which the two pigment-spots and the four cilia are still to be seen for a time, but soon disappear. This whole process occupies about five minutes. The resulting zygosperm is then a spherical cell enclosed in a cell-wall, which remains at rest for some time as a hypnosperm, its green colour becoming changed to brick-red. If the dried-up hypnosperms are placed in water, they begin to germinate after about twenty-four hours. The outer layer of the cell-wall is ruptured, an inner layer becomes gelatinous and swells up, and the protoplasmic contents escape in the form of one, two, or three large zoospores. Each of these, after a short period of swarming, loses its cilia, surrounds itself with a gelatinous envelope, and breaks up, by successive bipartitions, into sixteen portions, which develop cilia, and form them- selves into a new coenobe. A still more remarkable succession of phenomena is exhibited by Stephanosphcera Cohn, a rare organism occur- ring occasionally in the rain- water which collects in the hollows of large stones in mountainous countries. In addition to the process of vegetative or non-sexual pro- pagation, the cells belonging to a family, each of which possesses a red pigment-spot, divide repeatedly into zoogametes, which ultimately become free, and coalesce into resting zygosperms or hypnosperms. Motionless balls, which are probably the result of this conjugation, accumulate at the bottom of the water, and assume a red colour. After- Fig. 262.— Pandorlna iitoj-iiin Fhrb. a, swarming coenobe ; b, c, swarm-cells ; d, e, comugation of zoogametes ; _/, z^'gosperm ( x 500). (After Prings- heim.) 302 ALG.E these resting-cells have lain for some time dry, and then again been flooded, the contents break up into four or eight zDospores, which invest themselves with a cell-wall, and, in the course of a single day, divide, by successive bipartitions, into an eight-celled coenobe, which again, during the next night, gives birth to eight motile families. The enclosed primordial cells of Stephanosphasra are of a bright green colour, fusi- form, and are attached to an equator of the investing membrane at both ends by branched strings of protoplasm. The whole family rotates on an axis at right angles to the plane which passes through them all. In Goriiiiin Mull, the ccenobe is a tabular aggregation of cells moving rapidly through the water by the aid of vibratile cilia. Its life-history has not been fully followed out, and very little is known of its mode of reproduction. Literature. Henfrey — Trans. Micros. Soc, 1856, p. 49. ■Cohn& Wichura — (Stephanosphctra) Xova Acta Acad. Nat. Cur., xxvi. , Suppl. 1857, p. I (Quart. Journ. Micros. Sc. , 1858, p. 131). Archer— Quart. Journ. ]\Iicros. Sc. , 1865, pp. 166, 185. Cienkowski — Bot. Zeit. , 1865, p. 21. Pringsheim — Monber. Berlin Akad., 1869, p. 721 ; and Bot. Zeit., 1870, p. 265. Token— Bot. Zeit., 187 1, p. 383. Rostafinski — Bot. Zeit., p. 785 ; and Mem. Soc. Sc. Nat. Cherbourg, 1875. Goroshankin — Xachr. Gesell. Xaturf. Moskau, 1875. Hieronymus - Oesterr. Bot. Zeitschr. , 1S74, p. -^i-^efseq. Keinhard —Arbeit. Xaturf. Gesell. Charkoff, 1876. Breal— Bull. Soc. Bot. France, 1S86, p. 238. Dangeard — (Chlamydomonas) Ann. Sc. Xat., vii., 1888, p. 105. Order 5. — Sorastre^e. In this order are included a few genera distinguished by the ccenobe being unciliated. In Sorastriim Ktz. the colony consists of a more or Fig. 264. — So7-astruin spimc- losnm Nag. ( x 400J. (After Cooke.) Fig. 265.- Ccelastrjim cubiaim Nag. ( X 6od). (From nature.) less spherical aggregation of closely-packed, horned or bifid, somewhat CCEXOBIE.^ 303 Avedo-e-shaped cells ; in Selenastriim Reinsch the cells are crescent- shaped : in Ccelasfruin Xiig. the coenobe is spherical or cubical, com- posed of a single layer of cells, and hollow in the centre. The species are found occasionally in bog-pools ; although unciliated, the coenobe swims freely in the water with a kind of rolling motion. \y. a, formation of first spores (zoosporanges) at ends of branches : b, two ripe spores on each branch and a third being formed ( x about 200). (After de Bar}-.) is popularly termed a fungus, such as the stalk and cap of mushrooms, the peridium of puff-balls, and the like. The structure of these is, as has been said, very diverse, and it will be found described in more or I I " FUNGI less detail under the different groups of fungi. It may be well to note that transition-forms occur between the simple and compound types of / a / Fig. 273. — Agaricits dryophihis Bull, a, compound sporophore, longitudinal section showing the course of the hyphee, a very young complete specimen i'3 mm. in height, first beginnings of pilaus ; b, older specimen with pileus 2'5 mm. in breadth : /, piece of a lamella (slightly magnified). (After de Bary.) sporophore : for example, Penicillium, though commonly simple, some- times produces tufts of sporophores formerly supposed to belong to a different fungus under the generic name of Coremium. Spores. The prevailing mode of spore-formation is by acrogenous abj unction. The terminal portion of the mother-cell or a special protuberance formed on it is cut off by a transverse wall, and this daughter-cell then drops off as a spore. The basidiospores of Basidiomycetes may be taken as an example. Finely pointed processes are formed on the summit of the basid, and these swell into ball-like form at the apex. The globular body is then abjointed and set free as a spore. Series or chains of spores are successively formed in like fashion in Cystopus, Penicillium, Uredineae, &c. Spores are also endogenously formed within mother- cells— 5;^^rrt//^^j- — and these are of two kinds, motile and non-motile. Examples of non-motile spores thus formed are to be found in Mucor, and in the ascospores of Ascomycetes. Such spores are either set free by the disappearance of the sporangial wall or by internal causes effecting their ejection. ]\Iotile spores or zoospores (swarm-spores) possess the power of moving freely in water by means of fine whip-lashes or cilia, and examples of these are to be found in the Saprolegnieae and Perono- sporeae, the groups presumably most nearly related to Algae. That the phenomenon of the production of swarm-spores is one nearly akin to that a Fig. 274. — Pjiccinia graminis Pers. /, teleutospores ; zc, uredo- spore5(x 390). (After isachs.) Fig. 275. — ;//, mycelial branch of Cystopiis Portidacea Lev. producing two basids abjointing spores, in series ; b, sporophore of Eiirothtm hejbarioritm Lk. with sterigmata ; 5 and t, portions showing sterigmata, p, p. with their spores, « being the youngest {a x 390, the rest x 300). (After de Bar\-.) ^s1s?i %S:^ t^ Fig. 276. — Peziza {Pyroncvta) ccnJIiecns'PQrs. a, small portion of hymenium ; /, paraphyse attached to, not originating in, hyphal branches from which the three asci spring ; in, yoimg asci ; r w, successive stages, according to letters, in the development of ascospores within asci ( x 390). (After de Barj.) 3>4 FUXGI of simple germination by the emission of a germ-tube is manifest. The example of i'hytophthora infestans (de By.) illustrates this. The acro- genously-formed zoosporange pro- duces zoospores in pure water containing free oxygen in fair amount. In nutrient solutions, on the other hand, no zoospores are formed, and the potential zoospo- range simply emits germ-tubes. (Termination of spores, however, takes place characteristically in fungi by the emission of gerin- tiihes under conditions of tempe- rature, moisture, and the like presently to be discussed. Germination by the formation of sproiit-ceUs^ however, occurs in a number of forms. Fig. 277. — Zoosporanges o^ PhytophtJwra in/esinfis de By. a, division completed ; b, escape of zoo- spores ; c. free zoospores ; d. spores come to rest and germinating (x 350). (After de Bary.) Sexual Reproduction. This subject is incidentally so fully discussed under the different groups, that nothing need be said here beyond calling attention to the fact that it falls under the same types as in Algse. Such a form as Polyphagus may, however, be mentioned since it exhibits a type apart from ordinary isogamous or oogamous reproduction. r Conditions of Germination. Spores may be divided into two categories with reference X to their power of germination, viz. those, by far the majority, which are capable of germina- tion from the time of maturity, and those which must undergo a period of rest. Of the first kind a considerable number, generally sjjeaking thin-walled watery spores, sporids, or zoo- spores^ do not retain this power for more than a period measured by hours or days. The condi- tions under which they are kept are, as will be expected, of importance in this respect. Many spores retain the power of germination for a long period if kept in an air-dry Fig. 278. — Ascospores of Helvella escnh'uta Pers. Stages of germination in order of letters ( x 390). (After de Barj-.) FUNGI 315 state. This time extends in numerous instances to one or two years, and, in the case of spores of Ustilagineae especially, to longer periods. The spores of Tilletia caries (Tul.) germinated after eight and a half years, and those of other species after shorter intervals varymg from seven and a half downwards. Resting-spores^ or those of the second category, generally un- dergo more or less definite periods of rest corresponding to periods of vege- tation. "While germination cannot be procured before the lapse of this time, they frequently exhibit inability to survive the occasion presumed to be favourable. Such are hibernating spores like the teleutospores of Uredine^, and the oosperms of Peronospore^e. Resting-cells belonging to saprophytes again, e.g. the zygosperms of 3tIucorini, while they undergo a necessary period of rest of varying duration, yet display no partiality for seasons of the year, and this also is intelligible in view of their mode of life. The power of resistance of spores to external agencies operating against their vitality is in many instances very great. The spores and zygosperms of several Mucorini withstand mechanical injury and re- pair slight wounds while preserving the power of germination. Short- lived spores and those of aquatic fungi do not bear desiccation ; but a great number of spores retain the power of germinating, as has been stated, for considerable periods in an air-dry state. Spores adapted for hibernation in temperate climates, and, it may be assumed, long-lived spores, withstand very low degrees of temperature, ranging below zero C. ; while such long-lived spores, on the other hand, are very^ sensitive to high temperatures. The capacity for germination after exposure to high temperatures is maintained or not within certain degrees, according to the dryness or humidity of the environment. Thus it has been shown that while no spores are known to withstand a temperature of loo"^ C. in water or w^atery vapour, and many perish under these circum- stances at much lower temperatures, the same spores can endure a considerably higher temperature in a dry state. Dry spores of some fungi have been found to withstand temperatures up to 120'' C. and beyond, but it is probable that 130° C. marks the death-point of all. Others, again, perish at degrees considerably below 100^ C. It must, of course, l^e borne in mind that the duration of the exposure is an important factor in such experiments, and that spores which support a high temperature for a few minutes or an hour are killed by longer exposure. It is probable that much individual variation exists in regard to this matter and to the duration of life under ordinary circum- stances, and that in this lies the explanation of conflicting results ob- tained by different experimenters. There is not much known as to the maximum, minimum, and 3i6 FUNGI optimum temperatures at which the actual geruii nation of spores takes place. According to ^Viesner the minimum for tlic spores of Penicil- lium glaucum (Lk.) is from 1-5° C. to 2°, the optimum about 22° C, and the maximum 40° C. to 43°. This may be taken as fairly illustrative of other fungi in temperate countries in the open. Those which germinate, like many Mucorini and fungi inhabiting excrement, in the digestive tract of warm-blooded animals, have a much higher minimum, and an optimum agreeing with the body temperature. A supply of water and of oxygen must accompany the favourable temperature in all cases, and of nutrient substances in some. Speaking generally, parasites germinate freely in pure water or vapour, and saprophytes in nutrient substances, but the spores of many fungi germinate in both. Conditions of Vegetation. Under this head it will be necessary to consider little else than the nutritive adaptation of fungi, since they resemble other plants in the general conditions of vegetation, in their dependence on tempe- rature, light, (S:c. The optimum temperature varies, as might be ex- pected, in the cases of fungi which flourish at different seasons of the year, and in different climates. The optimum temperature for the growth of mycele in Penicillium glaucum is about 26"" C, while that of spore-formation is the same as that of germination, about 22° C. These figures may be taken as fairly illustrative. Lummosity ^ is exhibited by a considerable number of fungi- — Agari- ous olearius (DC.) and the rhizomorph form of A. melleus, Polyporus annosus (Fr.), and P. sulphureus (Fr.) (Europe), Agaricus igneus (Tul.) (Amboyna), A. noctil^icens (Lev.) (Manilla), A. Gardneri (Berk.) (Brazil), A. lampas (Berk.) (Australia), A. Emerici (Berk.) (Andaman Islands), a species of Didymium (Jamaica), and probably by a number of other forms, the evidence as to which is doubtful. It is a phenomenon dependent upon the life of the organism, and the progress in it of destructive metabolism. As regards nutrition, the absence of chlorophyll and the consequent inability to decompose carbon dioxide drive fungi to seek for organic •carbon-compounds. In taking up food, fungi cause chemical changes in the organic bodies which furnish the food, e.g. fermentation. The well-known ferment-fungi need only be n:ientioned. It is in the highest degree probable that the solvents secreted by such fungi as penetrate dense woody and other structures are ferments. All fungi may be * Vines, Lectures on the Physiology of Pla7its, p. 317 ; see also Phillips, Proc. Woolhope Chib, 1888. FUNGI 317 divided primarily into such as feed on the decaying bodies of plants and animals and dead organic substances — saprophytes — and those which attack living hodiAQ?>-~ parasites. Between the two extremes of strict saprophytes and strict parasites there are intermediate forms. Some saprophytes, which ordinarily live throughout their course of develop- ment as such, have the power of living as parasites either wholly or during a part of their course of development. Such are called faculta- tive parasites. Similarly some parasites which ordinarily live as such have the power of passing at all events a part of their lives as sapro- phytes. Such are facultative saprophytes. The lichen-for7?n?ig fnngt which live socially with alg^ may be placed in another category. Most fungi are saprophytes, and it is obvious, from the fact that so many are confined to specific substrata, that there is much variation in the nutri- tive adaptations of such forms. These adaptations are, however, more clearly marked in the case of the smaller number which lead parasitic lives. Some are confined to single species of host-plants ; many range over allied species, some of them attacking plants outside the group mostly affected, or exempting from attack certain species within the group. Others, again, may be said to be omnivorous parasites, attack- ing plants or animals of diverse groups. "\A'ith regard to the predisposi- tion of the host to the attack of the parasite, it is impossible for the most part to say exactly wherein it lies. Reference may be made to the case of species of Pythium which as facultative parasites attack Phanero- gams, &c. The amount of water present in the host determines there the degree of predisposition to attack. ^Miile a sickly condition may constitute a predisposing cause to the attack of a parasite in some cases, it is by no means so in the majority of instances. It has been asserted that certain cultivated plants, such as cereals and the potato- plant, hav-e by cultivation acquired an 'inherent tendency ' to certain parasitic diseases, whereas it is obvious that the growing together of vast numbers of these plants furnishes opportunity for the spread of diseases which, in the absence of other evidence, may be taken to account for extensive outbreaks. Parasites commonly attack their hosts by the penetration of the membranes of the uninjured host, though cases are numerous where the entry is made by means of the stomates, or of wounded surfaces only. ]\Iost are endophytes, but a small number — e.g. Erysiphe— are epiphytes, which send haustorial branches into the body of the host. The result of attack is either the destruction of the host, or the production of deformities by anomalous processes of growth in the parts affected. i8 Fu.yci Lichen- FORMING Fungi. These are strictly parasitic fungi which, without the aid of algal hosts, do not develop beyond the earliest stage of germination. Their nutritive inter-relations with their hosts, however, mark them off from other parasites. The hyphse of the lichen-fungus embrace the algal cells, and the two elements together compose a thallus of definite form. The algal cells form by means of their chlorophyll-contents organic carbon-compounds by which the fungal cells benefit ; Ijut here the resemblance to true parasitism ceases. The host exhibits no sign of exhaustion, since a reci- procal accommodation exists be- tween the two elements. The rhizoid filaments of the fungus draw from the substratum mineral substances, the raw material of food. The hyphal cells are fed by the exosmose of starch and the like from the algal cells, and the inference is justifiable that the algal cells receive in exchange by endosmose the waste products of the fungal protoplasm. There thus exists a lasting consortism or symbiosis between the elements, and the result is a thallus which may be treated from the point of view of the systematist as an autonomous oro-anism. It must never be forgotten, however, that it is fundamentally two organisms, one of which, the fungal, cannot live without the other, while the latter can and does exist separately and independently in nature. It is a question not definitely decided whether certain algal forms thus living in consortism can or cannot live separately, and it is also doubtful whether the fungal portion of such lichens as live on the bark of trees or substrata rich in humus, does not live partially as a saprophyte. Evidence certainly points in this direction. The sym- biotic relations existing in lichens are comparable with those described by Geddes, Brandt, and others, as in operation in Radiolarians and other animals, the ' yellow-cells ' of which are actively vegetating algae. Fig. 279. — Algal cells of Lichens. A, spore of Physcia parietina Nyl. germinating on Protococ- cics viridis Ag. B, Synalissa symphorea Nyl. with Glococapsa. C, Cladonia furcata Hofim. with P7-otococcHs. D, Stereocaulon ramu:osuiii Ach. with Scytonema. (A, B, and C, x 950, D X 650.) (After Bornet.) FLWGI 319 By far the greater number of lichen-forming fungi are Discomycetes or Pyrenomycetes. A few small tropical genera, Cora (Fr.), Rhipidonema (Mattir.), Dictyonema (Mont.), and Laudatea (Johow.), are Basidiomyce- tous, and two other tropical forms, Emericella (Berk.) and Trichocoma (Jungh.), have recently been declared by ^lassee (Phil. Trans. Roy. Soc. Lond., vol. 178, p. 305) to be Gasteromycetous Lichens. The two last-named cases are by no g means satisfactorily established, and much more x and better evidence must be forthcoming before Ar^" Fig. T.'i.o.—Coccocarpia violybdia Pers. Transverse section of thallus. or. upper, and itr, under cortical layer. ;«, so-called medulla ; g, algal cells ; r. rhizoids (x 6_o). (After Bornet.) they can be adopted as lichen-forming fungi. Propagation is effected by the spores of the fun- gal thallus, and an adaptation exists in certain lichens examined by Stahl for the supply of algas to the new lichen. Algal cells, the offspring of the thallus algae, which have been carried up into the hymenium, are cast out along with the spores, so that, both falling in the same neighbourhood, the germ-tubes of the spores find suitable hosts at once. This primary' synthesis, however, probably takes place comparatively rarely in lichens as a whole. Propagation is very abundant by means of soredes or brood -buds Fig. 281. — Ephebe pubcsccns Fr. Branch of thallus with two young lateral branches (j-) ; g, algal cells ; h, hjphae (x 500). (After Luerssen.) 320 FUNGI consisting of one or more algal cells surrounded by li\[)lKe which separate from the parent-thallus. As a rule one species of alga furnishes all the algal cells of a lichen ; more rarely two, and then one prevails in abundance (T ^M >?^?rN a d Fig. 282. — Usnca barbata Fr. Development of soredes. a, group of eight algal cells attached to hypha ; b. similar group with Ijranching hj-pha ; c, sorede with algal cell in optical section ; d, sorede with algal cells divided ; c,f, germinating soredes ( x 500 —700). (After Schwendener.) over the other. The same species of alga, however, may be found in consortism with different species of fungus, and taking part in the com- position, therefore, of differently formed thalli — different lichens in short. Fig. 283. — Cetraria islatidica Ach., a fruticose lichen (natural size). Stahl experimentally proved this in his successful attempts at lichen synthesis. The alg^ which furnish the hosts belong to different groups, and both unicellular and filamentous forms occur. The thallus of lichens is of two sorts, the hetei'oniei^oiis and the FUNGI 3-1 hovioiojneroiis. The heteromerous thallus mainly consists of the fungus body of the Hchen differentiated into a cortical layer and a inedullary layer^ the algae occurring either as a definite layer where the cortical and the medullary hyphse join, or they are scattered throughout the medulla, or form a dense mass in it. Such thalli exhibit considerable variety in forms of growth, and are c^W^d foliaceoits, fruticosej criistaceouSy Fig. 284. — Roccella tinctoria DC. A filamentous lichen. Small plant (natural size). &c., in descriptive works. The homoiomerous thallus consists of algal cells and hyphse more or less equally distributed and alike in bulk. CoUema, referred to below, is a gelatifious lichen, exemplifying this structure. Though the fungus does not actually prevail in bulk, it modifies the form of the thallus. Until comparatively recent times, lichens were considered to be Y 322 FUNGI independent organisms, the algal portion, the so-called ' gonidia,' being regarded as only specially developed cells arising from the colourless cells of the thallus. In 1868 Schwendener first accurately determined their dual nature, though de Bary had two years before indicated the possibihty of this state of things in the case of the Collemaceae, &c. The dis- covery so far, though sufficiently convincing, was based on anatomical considerations only, but the matter was finally proved, as well as a thing can be proved, by the experiments of Bornet, Treub, Reess, and Stahl. Reess succeeded in producing the thallus of Collema by synthesis, and Stahl went a step farther, and effected the formation of no less than three species of lichen. His observations on the relations of the algal and fungal elements of the lichen-thallus crowned the work of demon- stration of its dual nature. Many systematic lichenologists who have been unable to shake off the traditions of their study still cling to the old view of the independent nature of lichens. It is hardly necessary to point out that the judgment of morphologists on such matters is the one to be trusted, especially as the matter has once and for all passed beyond the state of trust in authoritative opinion into the perfect state of complete proof. Literature (Books of General Reference). De Bar}- — Vergleichende ^Slorphologie u. Biologic der Pilze, Mycetozoen u. Bacterien (Leipzig, 1884). [Translation by Garnseyand Balfour, Oxford, Clarendon Press, 1887, referred to in text as de Bary, Comp. Morph., &c.] (In the above book a complete guide to the detailed morphological literature will be found.) Systematic. Saccardo — Sylloge Fungorum (1882, in progress). This work is intended to include all known Fungi. The student should also consult the numerous works of Fries, dealing chiefly with Basidiomycetes ; Corda's Icones Fungorum (Prag, 1837-54) ; and for British Fungi, Berkeley's Outlines of British Fungolog}^ (i860) ; Cooke's Handbook of British Fungi (1871); the same author's Illustrations of British Fungi (1881, in progress) ; Stevenson's Hymenomycetes Britannici (Edinburgh, 1886) ; and Phillips' Handbook of British Discomycetes (London, 1887). Diseases of Plants caused by Fungi. Frank — Krankheiten der Pflanzen (Breslau, 1SS0-81). Sorauer — Handbuch der Pflanzenkrankheiten (Berlin, 1886). Smith, W. G. — Diseases of Field and Garden Crops (London, 1884). LiteTatU7-e of Lichen-thallus. This literature is too vast to be quoted here in detail, but the reader is re- ferred to the following essential papers. Bornet — Recherches sur les gonidies d. Lichens (Ann. Sc. Xat., ser. 5, xvii. and xix.). Johow — Ueber Westind. Hymenolichenen (Sitzber. Berl. Acad., 18S4), OOMYCETES 2-23 Reess — Ueber d. Entstehung d. Flechte Collema glaucescens (Monber. Eerl. Acad., 1871). Reess— Ueber d. Xatur d. Flechten (Samml. wiss. Vortrage von Virchow u. v. Holtzendorff, 1 879). Schwendener — Die Algentypen d. Flechtengonidien (Basel, 1869). Schwendener — Erorterungen z. Gonidienfrage (Flora, 1872). Schwendener — Die Flechten als Parasiten d. Algen (\'erh. d. Basel, naturf. Ges. , 1873); Stahl — Beitr. z. Entwickel. d. Flechten, ii. (Leipzig, 1S77). Treub — Lichenencultur (Bot. Zeit., 1873). Treub — Onderzoek. over d. Natuur d. Lichenen (Diss.) (Leiden, 1873). Special literature is quoted wider each group. GROUP L— PHYCOMYCETES. Class XVIII.— Oomycetes. Order i. — Peronospore^e. The thallus of the Peronosporese consists of irregularly and copiously branched hyph^e inhabiting for the most part the living, and especially the chlorophyll-bearing, tissues of terrestrial flowering plants of different natural orders. The mode of life in this case ! A is parasitic, and the hyphae usually follow the intercellular spaces, and in many cases send short processes termed haustoria into the ad- joining cells. These haustoria are variously formed according to the species. They are gene- rally branched in Pero- nospora (Corda) and glo- bular in Cystopus (Lev.). The hyph^ of other species (Phytophthora, de By.) traverse the cells of the host- plant. Trans- verse walls do not commonly appear in the hyphae until the period of the formation of reproductive organs. The effect of this parasitic mode Y 2 Fig. 285. — Intercellular mycelial hyphae (;«), ^vith haustoria penetrating into cells (2), A , of CystopJis candidiis L6v. ; B, of Peronospora calotheca de By. ( x 390). (After de Bary.) 324 FUNGI of life on the host is extensive destruction of the tissues, usually ending in death. Hypertrophy is produced in other cases, especially at the time of the formation of oosperms, leading to swellings and distortions of the parts affected. Of the species of Pythium (Pringsh.) transferred to this order by de Bary (Bot. Zeit., 1881) from the Saprolegnieae, some are saprophytes inhabiting the dead bodies of both plants and animals, while others are both parasites and saprophytes. The oogones are globular cells with either a smooth or a granulated wall of some thickness, situated, as a rule, terminally, or more rarely interstitially. Soon after separation by a transverse wall from the hypha which bears it, the protoplasm of the oogone, which is rich in drops Fig. 286. — Fertilisation of Peronosporeae. /. — VI., PytJiiu7!i gj'acile Schtvk. Successive stages accord- ing to numbers (x about 800). VII .,Peronosp07-a arborebcetis de By. Oosphere is invested with a ; thick membrane, outside of which is the periplasm contracting to form outer coat of oosperm ( x 600). (After de Bary.) of fatty matter, begins to collect into a central mass containing the drops and bounded by a hyaline layer. Outside this central body {oosphere) there is left over a clear mass of protoplasm {periplasvi)^ which fills up the space between it and the wall. AVhile the oogone is thus developing, the antherid arises, either from the pedicel-cell of the oogone itself, or as the terminal cell of a neighbouring branch. It has commonly the form of an irregularly bent tube with an unthickened cell-wall, and at first ordinarily granular protoplasm. It applies itself closely to the wall of the oogone, and sends through it a delicate straight impregnating tube, which penetrates to the surface of the oosphere. The protoplasm of the antherid also undergoes about this period a differentiation into two masses ; one, threadlike but irregular, and occupying the middle. OOMYCETES 325 contains the more granular particles, and is termed the gonoplasm^ while the other {periplasm) surrounds it. The gonoplasm enters the oosphere through the impregnating tube of the antherid, and thus accomplishes the act of impregnation. Sometimes two, rarely more, antherids arise and apply themselves to the oogone, and this varies both with species and individuals. After impregnation the oosperm assumes a cellulose membrane, and gradually ripens. The fatty contents collect into one body occupying the middle, and the membrane becomes thicker and differentiated into two cellulose layers, the extme and the intiiie. The periplasm develops into a brown, often granulated and wart}' membrane, the extine, enclosing the oosperm, while the original wall of the oogone generally breaks up, but may in some cases persist. The oosperms germinate in water after a period of rest generally lasting throughout the winter : and this takes place either by the emission of a germ-tube which gives rise directly to a new thallus like the parent one, or the protoplasm divides into a number oi zoospores, which, extruded together within a globular sac and escaping from it, swim for a short time, and, after settling down, push out each a germ-tube which pro- duces a new thallus. In other species, again, both methods of germina- tion occur, some of the oosperms directly emitting germ-tubes, while in the others the i3roduction of zoospores intervenes. In certain species, the oosperms of which produce a germ-tube directly, a short mycele (promycele) is formed, which, after bearing a few conidiospores, dies, and these conidiospores in turn propagate new thalli. The non-sexual organs of propagation {conidiospores) are borne upon special branches of the thallus {sporophores) in a variety of ways cha- racteristic of the genera and in a minor degree of the species. These germinate either by means of a germ-tube directly produced, or the contents break up into zoospores, which, after swarming, settling down, and becoming invested with a membrane, also produce germ-tubes. The usual course of life is the production upon the thallus of vast numbers of conidiospores, which propagate the species extensively throughout spring and summer, followed in autumn by the bearing of sexual organs, with which the generation terminates. De Bary points out('Comp. Morph.,'^:c., 1884) that only in the instances above mentioned of the production from the oosperm of a promycele bearing a few coni- diospores, can a distinct alterjiation of generations be recognised. There is indeed merely the succession of one oosperm-bearing generation to another, the propagating spores being only accessor}^ products of the thallus. In such cases as Pythium vexans (de By.) and Artotrogus (]\Iont.), for example, there are no such organs of propagation at all, or at least long-continued research has failed to discover them. Other 32( FUNGI a species appear again to have lost the power of producing sexual organs^ and this is notably the case in Phytophthora infestans (de By.), the potato -disease fungus, which succeeds in hibernating by means of a perennial mycele. In such a case the species is entirely dependent upon the propagating spores for distribution. Cystopus (Lev.). — The thallus consists of hyphae inhabiting the intercellular spaces of the tissue of flowering plants, and provided with haustoria. The oosperms are resting-cells which ger- minate in spring by means of the production of zoo- spores in the usual way. The propagating zoospores are borne in zoosporanges at the end of cylindrical or club-shaped zoospo7'angwphores in vertical series. A small broad swelling first appears at the apex, and then a transverse wall cuts off the upper portion, which rounds off and thus becomes the first and oldest zoosporange of the series. Then another is cut off in the same fashion, while the sporangio- phore elongates. A series or chain is thus produced^ each zoosporange joined to its neighbour by a very short and slender connecting stalk. The first cell at the top of the series has a thicker wall than the others, is yellowish in colour, and is, at least in the vast majority of cases, incapable of germination. If germination does take place, a germ-tube is said to be produced, while all the other members of the series give rise to zoospores. These chains of zoosporanges arise in dense masses side by side below the epiderm of the host, which is gradually ruptured, permitting their escape, the thick wall of the top member of the Fig. 287.— w, mycelial scrics scrving as a shield in bursting the epiderm. branch of CystopJis -,-,^1 ,1 ... , Porhdacecs\.€v., pro- W Hcn the zoosporcs gcmimate, their germ-tubes enter phoref,/!b2rTng"foo- ^hc host by way of the stomates, by this means attain- ing directly the intercellular spaces. The disease thus set up in the host is not so active as in the case of species of Peronospora, and the parts affected do not perish so rapidly. During the formation of oosperms in Cystopus candidus (Lev.), regions of the host undergo acute hypertrophy. The commonest species of the genus is C. candidus (' white rust '), which attacks a large number of Cruciferae. Cabbages and the Shepherd's Purse (Capsella bursa-pas- toris) suffer conspicuously from it, while the latter is often affected by Peronospora parasitica (de By.) in company with it. Other well-known species are C. Portulace^ (Lev.) and C. cubicus (Lev.). phores,/, bearing : sporanges, n, in series ( X 390). (After de Bary.) OOMYCETES 327 Perojiospora (Corda). — The thallus and the sexual organs closely resemble those of Cystopus. In both genera the passage of protoplasm from the antherid into the oogone is not directly visible, and the oogonial periplasm is more abundant than in the other genera. In germinating, the oosperm produces a germ-tube, but the process of germi- nation has not been observed in a number of species, and, as de Bary says (Journ. Roy. Agric. Soc, 1876), it is quite possible that the species of Peronospora which, like Cystopus, produce zoospores from their 'conidia' (zoosporanges) present also the same phenomenon in connection with the oosperms. The sporophores of Peronospora commonly issue from the host-plant through the stomates, and are, for the most part, regu- larly and copiously branched. At the fine points of the branches the non-sexual propagating bodies are produced singly. These are in some species conidiospores germinating by the emission of a germ-tube, and in others zoosporanges producing zoospores. Conidiospores and zoo- sporanges are borne in precisely similar fashion, and present the same appearance up to the production of the germ-tube or zoospores, as the case may be. The zoospores are formed within, and escape from the original zoosporangial membrane and not from an extruded sac. Inter- mediate between these forms are the plasmatoparous species (P. densa^ Rab., and P. pygnicea, Ung.), in vrhich the whole protoplasm escapes from the spore in a mass through the opening of a papilla-like point in the wall, and, at once becoming globular, secretes a cellulose membrane^ and subsequently germinates by the emission of a short thick germ-tube. The germ-tubes both of zoospores and of conidiospores penetrate directly the epiderm of the host and the cells underlying it, until an intercellular space is reached. This genus contains a large number of well-known parasites, such as P. viticola (de By.) on the vine, P. nivea (de By.) on Umbelliferae, P. parasitica (de By.) on Cruciferse, P. Schlei- deniana (Ung.) on onions ; P. Viciae (de By.), P. Trifoliorum (de By), &c. Hypertrophy is frequently produced in the host at the time of oosperm-formation, but not so acutely as by Cystopus. The oosperms of several species are unknown, and of these P. Rumicis (Corda) and P. Schachtii (Fiickel) hibernate by means of their perennial mycele, while P. Ficariae (Tul.), the oosperms of which are known, passes the winter in the same way. Fhytophthora (de By.). — This genus was founded for the reception of P. infestans (de By.), which was formerly placed in Peronospora. Industrious research has failed to discover the sexual organs and oosperms of this species. Mr. Worthington Smith claims to have found them, but the balance of evidence is distinctly against this. The sexual organs of Phytophthora omnivora (de By.) have been ^28 FUNGI observed, however, and fertilisation takes place in the usual way. A very small quantity of gonoplasm (not visibly differentiated) i^asses over into the oosphere. The antherids and oogones arise together in this species, and develop in close connection. The oosperms form each a promycele, as described above. The sporangiophores of Fig. 288. — Simple sporophores of Phytophthora in/estans de By. a, formation of first spores (zoosporanges) at ends of branches : b, two ripe spores on each branch and a third being formed (x about 200). (After de Bary'.) Phytophthora, which resemble those of Peronospora in general habit, differ from them in the fact that each branch bears more than one pro- pagating body— not in chains, like Cystopus, but at intervals on the branch. In P. infestans a propagating cell is produced at the apex of each branch ; and as it ripens a papilla-like swelling arises beneath it ; the branch grows on and turns the cell aside. These propagat- ing cells are usually zoosporanges, but not unfrequently they are coni- diospores, differing from them in no other respect than the pro- duction of a germ-tube directly instead of zoospores. The zoo- ¥iG.'2?,<).—Zoos,^ox:2.r\g&soi Phytophthora infesians sporcs are formed within and de By. a, division completed ; b, escape of zoo- , . , ^ , spores ; c, free zoospores ; d, spores come to rest CSCapC QirCCtly trOm the ZOOSpO- and germinating (X 390). (After de Bar,^) ^^^^^ -^^^j^^ ^^ -^ PcrOnOSpora. Phytophthora infestans has a special economic interest, as the cause of the well-known potato-disease. The disease first appears, as a rule, on the green leaves of the potato plant in July or August, the sporangio- phores emerging through the stomates. Sporanges are formed, under favourable conditions of temperature, moisture, &c., in a few hours, are OOMYCETES 329 wafted away, and, falling on other potato leaves, there produce zoospores, or germ-tubes directly, in drops of water formed by dew or rain. The germ-tubes penetrate the epiderm, setting up fresh growths of mycele in new plants, and thus the disease is propagated. Countless numbers of such propagating cells, each potentially the mother of a number of zoo- spores, may thus be set free from a few diseased plants, and the spread of infection and destruction of tissue in warm moist weather is almost inconceivably rapid. The disease extends to all parts of the plant, in- cluding the tubers, in which the mycele often remains in a resting con- dition throughout the winter (as in certain species of Peronospora mentioned above), and from which a fresh start is made in the following year. The interest attaching to the subject is mainly economic, and an extensive literature bearing upon it has grown up — by far the greater part of it utterly worthless. Pythiiun (Pringsh.). — Several species of this genus are saprophytes, inhabiting the dead bodies of plants and animals, while others are true parasites on fresh-water algae, on prothallia, and on flowering plants. The thallus and sexual organs are of the type described. The oosperms of P. proliferum (de By.), like those of Phytophthora omnivora, form a promycele ; while of P. vexans (de By.) the oosperms only are known. The formation of propagating spores occurs at the end of simple thallus- hyphce. A terminal cell is cut off by a transverse wall, and usually becomes a zoosporange. This body expands at the apex into a thin globular sac, into which the whole of its protoplasm empties itself. There zoo- spores are differentiated, and, bursting the sac, escape and germinate. There is some variation according to species in the forms of the zoo- sporanges ; sometimes they are round or oval and sometimes elongated. They have not the definite arrangement which characterises the other genera. P. intermedium (de By.) and P. de Baryanum (Hesse) some- times form spores which emit a germ-tube instead of the usual zoospo- ranges. P. gracile (Schenk), P. entophytum (Pringsh.), and P. Chloro- cocci (Lohde) inhabit fresh-water alg^, P. Equiseti (Sad.) and P. circumdans (Lohde) attack prothallia, while P. de Baryanum infests seedlings of different phanerogams and fern-prothallia. The last-named is capable of attaining full development as a saprophyte on both dead plants and animals. P. intermedium, also saprophytic, becomes a parasite on fern-prothallia. It is worthy of note that these fungi are parasitic only on seedlings, prothallia, &c., which contain abundance of water ; and though P. de Baryanum causes local injury to grown plants, this power may be raised to one of destruction under water. Pythium vexans is found in diseased potato tubers. 330 FUNGI Fossil Form. Peronosporites (W.G.S.). — This genus was founded by Mr. AVorthing- ton Smith for the reception of a fossil fungus Peronosporites antiquarius (W.G.S.), first detected by Mr. Carruthers in the axis of a Lepidodendron from the coal measures. Mycele and bodies which may well be oogones are visible in the preparations. The fungus is probably nearly related to Pythium. Literature. De Bary — Recherches sur le developpement de quelqnes Champignons parasites (Ann. Sc. Xat., 4 ser. , Tom. xx.). (Contains reference to older literature.) De Bary— Zur Kenntnissder Peronosporeen (Beitr. zur Morph. u. Physiol, d. Pilze, ii. ). De Bary— Untersuch, liber die Peronosp. u. Saprolegn. {ibid., iv. ). De Bar}^ — Research into the Nature of the Potato-fungus (Phytophthora infestans de By.) (Journ. Roy. Agric. Soc. , 1876, xii. ). De Bar}'— Zur Kenntniss der Peror.osporeen (Bot. Zeit., 1881). Cornu — Monogr. d. Saproleg. (Pythium) (Ann. Sc. Nat., 5 ser., Tom. xv. ). Hesse — Pythium de Baryanum, Halle, 1874. Millardet — Le Mildiou (Paris, G. Masson, 1882 ; and Journ. d' Agric. pratique^ 1881, T. i.. No. 6, and 1882, T. ii.. No. 27 j. Pringsheim — Die Saprolegnieen (Pythium) (Jahrb. wiss. Bot., i. ). Schroter — Peronospora obducens (Hedwigia, 1877, p. 129). Schroter — Protomyces graminicola {ibid., 1879, p. 83). W. G. Smith — Resting-spores (so called) of Potato Disease (Gard. Chron., 1875, iv. ,, N.S. ; and 1876, vi., N.S.). W. G. Smith — Peronosporites antiquarius, W. G. S. (Gard. Chron., 1877). [^ee also G. Murray, Academy, 17 Nov. 1877 and following numbers ; and Williamson, Phil. Trans. Roy. Soc. Lond., 1881.] A. Zalewski — Zur Kenntniss der Gattung Cystopus (Bot. Centralb., 1883, No. 33). Order 2. — Ancyliste^. This order embraces a few genera which, so far as what is known of them indicates, are related most nearly to Pythium. All the members of the group are parasitic in fresh-water algas (Cladophora, Mougeotia, Spirog}Ta, ]Mesocarpus, Closterium, &c.), and they are all farther charac- terised by simplicity of structure. The thallus is represented by hyphae at first undivided, which often extend from one end of the host-cell to the other. Ancylistes Closterii (Pfitz.) displaces the chorophyll-plates of its host, and ultimately causes the death of the cell. Lagenidium (Schenk), found in filamentous algae, causes the separation of cell-contents from cell-wall, and discolours the chlorophyll, which gathers together into a mass. The sexual organs are formed by the division into cells of the thallus- hyphas bv transverse walls. Of these cells, some swell and become oogones, while others remain small and act as antherids (Myzocytium, OOMYCETES ^ -^ T Schenk) : or different individuals produce the oogones and the antherids (Lagenidium, Ancyhstes). A perforation having been made in the oogonial wall, the whole of the protoplasm of the antherid empties itself into the oogone (there being no periplasm), and the united mass rounds itself off and becomes the oosperm. The germination of the oosperm has not been observed. Propagation takes place by means of zoospores (Lagenidium), and to this end either the whole thallus-hypha becomes transformed into a zoosporange, or it is divided into a series of such. Each zoosporange sends out through the membrane of the host-cell to the surrounding water a protuberance, through which the contents escape after the fashion of Pythium, forming uniciliated zoospores, which ultimately attack the fresh cells of other alg^. In Ancylistes the only propagation known is a process of extension of its hyphae from one host to another. Literature. Cornu — Monogr. des Saprolegn. {loc. cit.). Cornu— Xote sur I'oospore du Myzocytium proliferum, Schenk (Bull. Soc. Bot. France, xvi. , 1869, p. 222). Pfitzer — Ein neuer Algen Parasit (Monatsber. Berl. Acad., 1872}. Schenk — Ueberdas Vorkommencontractiler Zellen im Pflanzenreich (Wiirzburg, 1858). Zopf — Ueber einen neuen parasitischen Phycomyceten, &c. (Lagenidium) (Bot. Zeit., 1879, p. 351). Order 3. — Moxoelepharide^. The single genus ]\Ionoblepharis(Corn.), like the preceding group, is closely re- lated to Peronosporeae and especially to Py- thium. The thallus- hyph^ bear both ter- minal and interstitial oogones, in which there is no preliminary dif- ferentiation of peri- plasm, but the whole protoplasm contracts and forms the 00- sphere, while the apex of the oogonial wall opens. The antherid (usually a cell adjoining an oogone) produces several swarming antherozoids, which escape, one of Fig. 290. — Monoblepharis sphcerica Cornu. oogone, o, and antherid, a, antherozoid, s. successive stages ( X 800). (After Cornu.) Filament bearing an The numbers indicate 332 FUNGI them attaining and entering l)y the apical opening of the oogone, and uniting with the oosphere. The resulting oosj^erm has not yet been observed to germinate. Propagation takes place by the formation of uniciliated zoospores in zoosporanges, from which they escape in the same way as those of Phytophthora. Literature, Cornu — Monogr. des Saprolegn. {Joe. cii.). Order 4. — Saprolegnie^e. The Saprolegnieoe, as their name indicates, are saprophytes on the dead bodies of both plants and animals in water ; with at all events the exception of the Saprolegnia of the salmon disease, which is both sapro- phyte and facultative parasite. The cause of the predisposition to this disease has not yet been exactly determined, as for example has been the case with those species of Pythium which possess a similar mode of life. Prof, de Bary points out with regard to them that susceptibility to disease in the host is in relation to the amount of water present. The problem in the case of the salmon disease has every appearance of being a more complex one. The Saprolegniese bear in other respects much resem- blance to the Peronospore^, and especially to Pythium, which until recently was included among the former. Pythium indeed presents points of relationship with the types of Oomycetes in general ; and the relationship is rendered the more striking by the union in some of its species of both parasitic and saprophytic modes of life. The thallus- hyphae of the Saprolegnieas are usually of relatively large size, springing from slender rhizoids buried in the substratum. The oogones arise, as in Peronospore^, on branches of the thallus- hyph^. In most cases, however, several oospheres are formed in each oogone (sometimes as many as thirty or forty), and, no periplasm having been differentiated, the whole of the oogonial protoplasm is included in them. It happens in some cases that only one oosphere is formed, but the number is variable according to species, and also partly according to individuals. Pits arise, but by no means always, in the oogonial wall. The antherids, which are commonly club-shaped, are produced on slender branches of the thallus ; and each antherid is borne either on the same hypha of the thallus as the oogone to which it is attached, or on a hypha which bears no oogones. The remarkable point about these antherids is their impotency, since no actual observation of the transference of protoplasm from them to the oospheres has ever been made, though they perforate the oogonial wall, and processes, like impregnating tubes sent through, come in contact with the oospheres. These processes grow from one oosphere to another, and may even OOMYCETES ■^ '1 'i emerge again outside the oogonial \v points, and after a day or two perish, antherids never produce these pro- cesses, or the oogones may be without antherids. In other cases antherids are never produced at all, or only by way of rare exception. In the meantime the oospheres ripen into oosperms, while the antherids, if present, perish. Pringsheim has recently endeavoured to show that impregnation takes place in certain species by the transference into the oospheres of minute portions of antheridial protoplasm moving in amoeboid fashion. De Bary points out that, while Pringsheim has not actually seen this, the sole evidence trusted to is that of stained prepa- rations, which appear to exhibit open communication between antherid and oosphere, &c. In any case the observation does not affect those cases where antherids are either want- ing, or do not produce the penetrating tubular processes. The ripe oosperms thus parthe- nogenetically produced germinate after a period of rest varying from a few days to several months. Ger- mination takes place, as in the Peronosporeas, either by means of a germ-tube, or zoospores are pro- duced. Propagation is ciTected by the agency of zoospores produced in special zoosporanges, and also excep- tionally by means of certain resting- cells formed by the mycele after transverse division of the hyphas (Saprolegnia). These swell out into branes and plentiful protoplasm; and germ-tube, or zoospores are formed all, but they remain closed at all In the case of certain species, the Fig. 291. — A to C, Achlya racemosa Hildebr, At the end of A is an emptj- zoosporange, ^. with emptj^ zoospore membranes ; at a. b, and c, are ocgones with antherids, a, in an early stage, b and c as in B, oogone with two oospheres and an antheridial tube applied to one. C, ripe oosperm. D, E, Achlya polyandra Hildebr. D, oosperms germinat- ing. E, germinating oosperm whichhasformed a sporange with a head of spores. (.-/ x 145. B and C x 375, D and E x 225.) (After de Bar}-.) globular form, with thick mem- germinate by the emission of a in them ('resting sporanges ' of 334 FUNGI Pringsheim). These resting cells or si^oranges are formed only on old myceles, and by no means regularly. The zoosporanges vary in form with the genus, and in a minor degree with the species. The usual form is a large club- shaped zoosporange containing a great number of biciliated zoospores, which escape from it through an opening at the apex ; though in poorly developed indi- viduals (and normally in Aphanomyces, de By.), the zoosporange is more cylindrical, and only one row of zoospores is formed. In Saprolegnia (Nees ab Esenb.) the zoo- spores are actively motile when they escape. Their activity ceases for the most part after a few minutes ; they settle down, assume a thin cellulose-membrane, rest for a short time, only to escape from this membrane, and resume active movement before final settling down and germina- tion. The spores of individuals may on the other hand omit the second period of movement, and germinate directly on first settling down. In Achlya (Nees ab Esenb.) and Aphanomyces the spores escape from the sporange without cilia and active movement. They arrange themselves in globular fashion outside the apex of the sporange, assume each a thin cellulose- membrane, within which they rest for a few hours, and, escaping from it, swim about, and, settling down, ultimately ger- minate. In the sporanges of Dictyuchus (Leitg.) the spores are each enclosed in net-like cellulose walls, from which they escape, not by any special orifice of the sporange, but by taking as it were the shortest cut through the sporangial wall and empty spore-cases if they come in the way. In Aplanes Braunii (de By.) the formation of propagating spores is as a rule omitted. When produced they give rise to germ-tubes directly without swarming. The zoospores produced by oosperms behave, so far as is known like those from the corresponding zoosporanges. Fig. 292. — Zoosporanges of Achlya N. ab E. A, with zoospores formed but still enclosed. B, with zoo- spores escaping. At a they are in- vested, with a cell-membrane, at c they are free, empty membranes at <^ ( X about 300). (After de Barj-.) OOMYCETES 335 The modes of zoospore-formation in Phytophthora and Cystopus, Pythium Achlya, and Aphanomyces, Dictyuchus, and lastly Saprolegnia, express in an interesting way the relationships of these genera. Literature. De Bary — Eeitr. zur Kenntniss der Achlya prolifera (Bot. Zeit., 1852). De Bar}' — Einige neue Saprolegnieen (Pringsheim's Jahrb. wiss. Bot., ii.). De Bary — Untersuch. liber die Peronosp. u. Saprolegn. (Beitr. zur Morph. u. Physiol, der Pilze, iv. ). De Bar}'— Zu Pringsheim's Neue Beob. liber d. Befruchtungsact der Gattungen Achlya und Saprolegnia (Bot. Zeit., 1883). ■Cornu — Monograph, der Saprolegn. %\nn. Sc. Xat., 1872). Hildebrandt — ^Mycolog. Beitrage, i. (Pringsheim's Jahrb. wiss. Bot., vi. ), Hartog — On the Formation and Liberation of Zoospores in the Saprolegnieee (Quart. Journ. Micr. Sc, 1887). Hartog — Recent Researches on Saprolegniese (Annals of Botany, 1888). Huxley and Murray — Salmon Disease (Reports of Inspector of Fisheries, 1882, 1883, 1884, 1885. See also Quart. Journ. ^licr. Sc, 1882, and Journ. Bot., 1885). Leitgeb — Xeue Saprolegnieen {ibid. , vii. ). Lindstedt — Synopsis der Saprolegn., Berl. , 1872. Pringsheim — Entwickelungsgeschichte der Achlya prolifera (X. Acta Acad. Leop.- Carol. , xxiii. , p. i). Pringsheim— Beitr. zur Morph. u. Systeraatik d. Algen, ii. Die Saprolegn. (Jahrb. wiss. Bot., i. , ii., and ix. ). Pringsheim — Xeue Beobacht. liber d. Befruchtungsact von Achlya u. Saprolegnia (Sitzber. Berl. Acad., 8 Juni, 1882). Xachtragliche Bemerk. zu dem Be- fruchtungsact von Achlya (Pringsheim's Jahrb. wiss. Bot., xiv.). Reinsch — Beobacht. liber einige neue Saprolegn. {ibid., xi.). Thuret — Rech. sur les zoospores des Algues, 1851. AVard — On Saprolegnieae, and also on Pythium (Quart. Journ. Micr. Sc, 1883). Contain histological details. Class XIX. — Zygomycetes. Order i. — ^vIucorixi. The Mucorini are for the most part terrestrial saprophytes, the re- mainder being parasites on other Mucorini. The thallus consists of a copiously branching hypha undivided up to the time of the production of spores or sporanges, when transverse walls first appear. Sexual repro- duction is effected by the formation of a zygosperm, while spores and pro- pagating cells (like some of the resting-cells produced by the mycele of Saprolegnia) are also borne, the former regularly and in characteristic forms, the latter only in special cases and under certain conditions. The production of a zygosperm is effected by the conjugation of two specially differentiated cells, gametes, not to be distinguished from each other by any mark or power of movement. The two cells thus contributing to 33'^ FUNGI its formation either, by their simple fusion, themselves constitute the zygosperm, or this body is the direct offspring (daughter-cell) of the union. The spores are produced either in terminal spora?iges or singly at the apex of a sporophore, or again serially in like fashion to the last. In a considerable number of cases the zygosperms are unknown, and it (y-: "■.-- ^.\._ _, ._ ^ Fig. 293. — B, Phycomyces nitens Kze. Plant grown on decoction of plums ; mycele, m, spo- rophore, f^. A,C, and Z>, Miicor Miicedo L. A, sporange in optical longitudinal seciion. C, zj-gosperm (2) borne on suspensors. k, germ-tube ; g, sporange. D, conjugation. a, a, gametes; b, b, suspensors. {^B slightly, A, C, and D more highly magnified.) (After Brefeld.) may be assumed, on the weighty authority of de Bary, that in certain of these they do not occur, since industrious observation has failed to dis- cover them. They are known, in fact, only in nineteen species, though future research may bring a fair number more to light. Where they have been observed the life-history proceeds as folio ivs. The germinating ZYGOMYCETES 337 zygosperm gives rise directly to a promycele bearing the characteristic spores, and these in turn produce on germination a mycele which bears spores again, and ultimately a zygosperm. It has been observed in an artificially nourished individual, that the germinating zygosperm at once produced a mycele which subsequently bore spores without the inter- vention of the promycele stage. In another instance (Sporodinia grandis. Link) zygosperms have been observed on a mycele which arose from a spore, before the production of sporophores upon it ; while it sometimes happens in this species that a zygosperm is produced on a mycele arising directly from a zygosperm without the intervention of spores at all. But in the great majority of cases the production of spores precedes the formation of a zygosperm on the same mycele. In many species the zygosperms are of rare occurrence, and an indefinite number of succes- sive spore-bearing generations come between zygosperm and zygosperm. Throughout the whole order spores are produced in vastly greater numbers than zygosperms. Syzygites (Ehrenb.) is the generic name given to certain forms of doubtful affinity which produce, so far as is known, zygosperms alone. Sub-order i : Mucore.e. — The members of this group are for the most part saprophytes on the excrement of animals, fruits, bread, saccharine fluids, (S:c. The thallus-hyphse are relatively large and much ramified. The conjugating hyphse arise either as branches of the mycele or on special hyph^ somewhat resembling sporangiophores, their place of origin being, in different instances, in either morphological or merely local approximation to each other. At an early stage of development they come into contact by their apices, and a firm connec- tion between the two is established. Thus joined the development of each goes on, and soon a transverse wall cuts off the apical portion of each. This portion is a gamete^ and the rest of the hypha, generally club-shaped, its suspensor. A pore next appears in the centre of the original wall separating the two gametes, and gradually the whole wall disappears and the contents conjugate. The zygosperm thus formed increases in size, drawing upon the contents of the suspensors. The protoplasm becomes dense, and the fatty contents gather into a large drop. The wall commonly becomes covered externally with warts or spines at all points except where the suspensors are attached. The form of the whole is roundish or drum-shaped, the smooth walls adjoining the sus- pensors corresponding with the sides of the drum. The wall is divided into two coats, the outer one {extine) brown or black, and the inner one {intine) stratified, and either entering the corrugations of the extine or remaining smooth along the surface of contact with it. The suspensors usually remain in statu quo, but in Rhizopus nigricans (Ehrenb.), where z 338 FUNGI one gamete is about half the height, though of the same breadth, as the other, the suspensor of the smaller one becomes greatly enlarged after conjugation, while the other remains as it was. In most cases the sus- pensors eventually decay, but in others (Phycomyces, Kze., and Absidia, Van Tiegh.) an outgrowth of darkly coloured hyph^e takes place from each suspensor and invests the zygosperm. In Mortierella (Coemans), which has a smooth extine, this outgrowth arises from the hyphae bearing the suspensors (as well as from the suspensors in one case), and forms a compact integument of the zygosperm. In M. nigrescens (Van Tiegh.) this outgrowth begins after conjugation, first from the suspensors, then from the adjoining hyphce; while in M. Rostafinskii (Bref.) the outgrowth Fig. 294. — Rhizopus nigricans YLhr. Formation of a zygosperm. Stages according to l;tters (x about 90). (After de Bary.) takes place solely from the adjoining hyphse, and begins so early that an investment is formed before actual conjugation takes place. A phenomenon resembling that of the parthenogenesis of the Sapro- legnieas is exhibited by a number of the Mucorese in the formation oiazygo- sperms. This occurs in Absidia, Sporodinia (Link), and Spinellus fusiger (Van Tiegh.), and the formation of these bodies ensues when gametes have failed to conjugate, and even when single gametes only are pro- duced. They possess the structure and power of germination of normal zygosperms, just as the parthenogenetic oosperms of Saprolegnia do. Bainier states that Mucor tenuis (Link) forms only azygosperms, and de Bary suggests that the (as yet little known) Azygites of Fries may be found to exhibit this phenomenon. On the germination of the zygosperm, as has been said, 2^ proniycele bearing sporanges is produced directly, and these sporanges have the ZYGOMYCETES 339 same structure as those that follow them. They are globular sacs borne at the end of sporangiophores, and the spores produced within them are never endowed with the power of active movement. The different forms of sporange and sporangiophore afford characters for the genera of the group. Mucor (Michel.), Pilobolus (Tode), Sporodinia (Link), Phycomyces, Rhizopus (Ehrenb.), Circinella (Van Tiegh.), and Absidia possess a peculiar conformation of the basal wall of the sporange. It bulges inwards in a conical or more or less oval form (see fig. 293 a), and presents an appearance which has suggested the name of columel for this peculiarity. Of. the genera possessing a columel some are dis- tinguished by a fugacious sporangial wall, others by a firm persistent one, while the mode of branching of the sporangiophore (or the absence of branching) and its general form, afford other generic characters. Mortierella has a fugacious sporangial wall but no columel. Tham nidium (Link), Ch^etostylum (Van Tiegh.), and Helicostylum (Cord.) have two kinds of sporange, the one kind like those of Mucor, and the other smaller {sporangioles) with a persistent wall, no columel, and containing but a few spores, which however resemble the others in function. On old and on badly nourished myceles of some species, accessory propagating bodies are formed {chla7nydospores^ stylosp07'es^ &:c.). All such accessory spores are capable of giving rise to normal characteristic myceles either at once or after a period of rest. In ]\Iortierella single acrospores are borne on slender mycelial hyphas. The old myceles and even the sporangiophores of Mucor break up into resting-cells like those . of Saprolegnia with thick walls. The chlamydospores (Van Tieghem) of Mortierella are such bodies, and where they occur terminally, de Bary regards them as transitional forms to the acrospores of the same genus just mentioned. Brefeld and Van Tieghem have described (Mucor racemosus, Fres., &c.) another form of accessory propagating spores, which are produced in series or chains through transverse division of the mycelial hyph^. These either remain joined together in confer\a fashion, as Berkeley says, or they part company, and each such cell exhibits a yeast-like vegetation. Sub-order 2: Ch.etocladie.e. — The mycelial hyphasof Chsetocladium (Fres.) become attached to the hyphce of the Mucor-host, and, by the resorption of the cell-wall at the place of contact, effect a direct com- munication. At such places of attachment a large number of globular protuberances are produced close together, forming a body of consider- able size, which may be regarded as a food-reservoir. The act of con- jugation and the formation of the zygosperm agree in all essential par- ticulars with the corresponding processes in the Mucoreas. The intine z 2 )4o FUNGI of the zygosperm has a smooth surface, not entering the external warts of the extine. Azygosperms have not been observed. The sporophores terminate in a fine hair-point, but below this give rise to a whorl of branches nearly at right angles to each other, terminating again each in a hair-point. These again branch more or less in like fashion. The ultimate branches become swollen, and on these swellings fine short sterigmata arise, each sterigma bearing a spore. The mass of spores thus produced has a bunch-like aspect. Cunningham's Choanephora, found by him on the flowers of Hibiscus, appears to approach most nearly to Chaetocladium. Sub-order 3 : PiPTOCEPHALiDEiE. — This very small group (Piptoce- phalis, de By., Syncephalis, Van Tiegh.) is, like the last, composed of parasites on the Mucoreas, and to this end the mycelial hyphse bear haiistoria^ each of which emits from its slightly swollen base a small crop of short delicate rhizoids traversing the Mucor-hypha affected. The conjugating hyphse of Piptocephalis are arched somewhat like an inverted fl, the point of contact beinsj the summit. Actual conju- gation occurs, as in the Mucoreae ; but when this stage is reached, the pro- duct of the conjugation begins to swell at the point of union, and generally on the convex side, into a globular body, which becomes echinulate as it swells. When it has attained its full size and development at the expense of the protoplasm of the united gametes, it becomes separated from them by transverse partition, and remains seated, as it were, on the summit of the arch. Though not the morphological equivalent of the zygo- sperm of the Mucoreae, but rather the offspring of the original z3^go- sperm produced by the conjugation of the gametes, it will be most convenient to regard it as the zygosperm. The sporophores bear at their apices series or chains of spores produced by transverse partition. In Piptocephalis the sporophore is dichotomously branched at the summit, and each bifurcation bears a capitulum of chains of spores. Accessory acrospores are sometimes produced by Syncephalis. :j)^ Fig. 295. — Piptocephalis Freseniana de Bj-. and Wor. Con- jugation and formation of a z^'gosperm, z. Stages in the order of the numbers ( X 650). (After Brefeld.) ZYGOMYCETES 341 De Bary ('Comp. Morph.,' p. 156) treats the incompletely known Dimargaris and Dispira, both of Van Tieghem, as at present doubtful jMucorini, probably near Piptocephalidese. Another small group of genera of doubtful position is formed by Kickxella (Coem.), Martensella Fig. 296. — P. Freseniana. M, a mycelial tube of Mucor Mtecedo, the host of Pipto- cephalis. The mj-cele of the latter, in, penetrates M by haustoria, h. Z, zj'gosperm. c, sporophore (x 300, the rest x 630). (After Brefeld.) (Coem.), Coemansia (Van Tiegh. and Le Mon.); while Sorokin's Zygo- chytrium, an aquatic saprophyte on dead insects, the account of which needs confirmation, stands in a like uncertain position. Literature. Bainier — Observ. sur les Mucorinees et sur les zygospores des Mucorinees (Ann. Sc. Nat., 6 ser. , Tom. xv. , 1S83 ). De Bary unci Woronin — Beitr. zur Morph. u. Physiol, der Pilze, i. and ii. Brefeld — Bot. Unters. liber Schimnielpilze, i- and iv. 342 FUNGI Rrefeld — Ueber G'ahrung, iii. (Landw, Jahrb., Thiel, v., 1876). Coemans — Spicilege mycologique (Bull. Soc. Bot. Belg. , i.). Coemans — Quelques Ilyphomj-cetes nouveaux (Bull. Acad. Roy. de Belgique, 2 ser,, Tom. XV.). Coemans — Recherches sur le polymorphisme et les differents appareils de reproduction. chez les ^Nlucorinees (z'/^z^., Tom. xvi.). Coemans — Monographic du genre Pilobolus (Mem. Couronn. de I'Acad. Roy. d. Belgique, Tom. xxx. ). Cunningham — On the Occurrence of Conidial Fructification in the Mucorini, illustrated by Choanephora (Trans. Linn. Soc. Lond., 2 ser., i., 1878). Fresenius — Beitr. zur Mycologie, i. and iii. Gilkinet — Mem. sur le polymorphisme des Champignons (Mem. Couronn. Acad. Belg., Tom. xxvi. , 1875). Hildebrand — Ueber zwei neue S5'zygites Formen (Pringsh. Jahrb., vi.). Klein — Zur Kenntniss des Pilobolus (Pringsh. Jahrb., viii. ). Tulasne — Xote sur les phenomenes de copulation, &c. (Ann. Sc. Xat. , 5 ser., Tom. vi., 1866). Van Tieghem et Le Monnier — Rech. sur les Mucorinees (Ann. Sc. Xat., 5 ser., Tom. xxvii., 1873). Van Tieghem — Xouv. Rech. sur les Mucorinees {ibid., 6 ser., Tom. i., 1875). A'an Tieghem — Troisieme Mem. sur les Mucorinees {ibid., 6 ser., Tom. iv. , 1876). Zimmermann — Das Genus Mucor (Chemnitz, 1871). Order 2. — EntomophthoretE. This small group of parasites inhabiting the bodies of insects agrees with the Mucorini only in the formation of zygosperms. The mycele vegetates within the body of the insect attacked, and consists either of septate branching hyphse (Entomophthora, Fres.), or of a yeast-like mass of cells (Empusa, Cohn). Zygosperms are formed, as described by Nowakowski (Entomophthora ovispora, Nowak., and E. curv^ispora, Nowak.), by the conjugation of adjacent hyphje which emit correspond- ing lateral protuberances. These meet, become united in an H fashion (somewhat as in SpirogjTa), and enter thus into open communication. As a result of this conjugation, there arises, either on the conjugating branches or near them, a globular body, which develops at the expense of the protoplasm of the united hyph^e, and finally becomes cut off. by a wall. This must be regarded as a zygosperm, morphologically the equivalent of that of Piptocephalis. Azygosperms occur in E. radicans (Bref.) and certain species of Empusa, arising either as lateral out- growths, or sometimes as terminal bodies. The cell-membrane of both zygosperms and azygosperms becomes much thickened and differen- tiated into a thick extine, generally of regular outline, and a thin intine, while in the contents a large fatty drop appears. Zygosperms and azygosperms both rest for a considerable period within the dead body ZYGOMYCETES 343 of the host, the surrounding mycele disappearing. On germination, which Xowakowski describes in Empusa GrylU (Fres.), a short pro- mycele is emitted which bears a single spore. Commonly, however, neither zygosperms nor azygosperms are formed, and after the death of the insect, spores are produced on its outer surface. In the case of Empusa — for example, E. Muscse (Cohn), which attacks the common house-fly in large numbers in autumn— tne yeast-like mycelial cells, at the tniie of the death of the insect, send forth each a tube, which bursts through the skin, and outside becomes a short club-shaped sporophore bearing a single acrospore. Each sporophore bears but one spore, and then perishes. The spores are capable of germination at once, but the power lasts only for a few days. Affected flies in this condition are common enough objects attached to windows, &c., and surrounded by a whitish mass of spores. The mycele of Entomophthora, which is septate, much branched, and often anastomosing, sends branches through the skin to the outer surface, where farther ramification takes place, investing the body of the insect. These branches range themselves at right angles to the insect's body, and terminate together at nearly the same elevation. Each such branch is a sporophore, which, as in Empusa, forms a single acrospore. The spores are capable of germination at once like those of Empusa ; and in both genera either a very short tube is formed, bearing a secondary spore, as in the promycele of the zygosperm, which, on germination, may attack a fresh insect, or the germ-tube of the primar}- spore may do so without the inter\-ention of secondary spores. Completoria complens (Lohde), found by Leitgeb in fern prothallia, and Conidiobolus utriculosus (Bref.), described by Brefeld as a parasite on Tremellini, are two forms placed here which, unlike the rest of the group, do not attack insects. Brefeld, who has investigated the group minutely, does not accept the conjugation as a real one, and brings forward arguments against it based on the anastomosing of hyphae and the situation of the zygosperms. His opinion, if accepted, would lead to placing the group elsewhere ; but de Bary states (' Comparative Morph.,' p. 159) that Xowakowski's and Brefeld's different observations mav be explained by the different behaviour of different species. Literature. Brefeld — Untersuch. iiber die Entwickel. der Empusa Muscoe und Empusa radicans und die durch sie verursachten Epidemien der Stubenfliegen und Raupen (Abhandl. d. Naturforsch. Gesellsch. zu Halle, xii. ). Brefeld — Ueber Entomophthoreen und ihre Verwandten (Sitzungsber. d. Gesellsch. Naturforsch. Freunde zu Berlin, 1877). See also Bot. Zeit., 1S77, p. 345. Brefeld — Bot. Unters. iiber Schimmelpilze (Ent. radicans), iv., 1881, p. 97. 344 FUNGI Cohn — Empusa iSIuscce und die Krankheit der Slubenfliege (Nova Acta, xxv., p. i). Cohn— Ueber eine neue Pilzkrankheit der Erdraupen (Tarichium megaspermum) (Beiirage zur Biologie der Pflanzen, Bd. i., Heft i, p. 58). Eidam — Eine auf Excrementen von Froschen gefundene Entomophthoree (Bot. Centralbk^tt, xxiv. , 1885). Fresenius— Ueber die Pilzgattung Entomophthora (AbhandL d. Senkenberg. Ges. , Bd. ii.). Giard — Deux especes d'Entomophlhora, &c. (Bull. Sc. du Depart, du Nord, 2 ser. , 2 Ann., No. 11). Frey und Lebert — Die Pilzkrankheit der Pliegen (Verhandl. d. Naturf. Ges. zu Ziirich, 1856). Leitgeb — Completoria complens, ein in Farnprothallien schmarotzende Pilz (Sit- zungsber. d. Wien. Acad., Bd. 84, Abth. i). Nowakowski — Die Copulation bei einigen Entomophthoreen (Bot. Zeit., 1877). Nowakowski — Entomophthoreae (Abhandl. d. Acad. d. Wiss. zu Krakau, 1883). Polish, see Bot. Zeit., 1882. Sorokin — Zwei neue Entomophthora Arten (Cohn's Beitrage zur Biol. d. Pflanzen, Bd. ii., Heft 3, p. 387). Order 3. — Chytridiace.^. The Chytridiacese are a group of minute, more or less aquatic, parasitic fungi, embracing forms which may, in the present state of our knowledge of them, be thus classed together ; but whether it will eventually appear that these are naturally related to each other, or are merely organisms of different affinities presenting a similar appearance owing to similar environment and ways of life, is but a subject for speculation. How- ever, there are points in which all agree, and their life-history may be briefly summarised thus : — Zoospores— mostly uniciliated (the rest with two cilia), and containing generally a drop of fatty substance, and, in tthe larger forms at least, a nucleus — are produced in zoosporanges of various forms and sizes. These escape from the apex of the zoosporange, which is provided in some cases with a lid, either successively or in a mass held together by a viscous substance, from which they are gradually set free. An undulating alteration of outline, accompanied by amcjeboid movement, takes place in the zoospores of certain species towards the end of the period of their activity. I'he zoospores g\N^ rise again to ;zoosporanges. Resting-spores are known in certain cases, which like- wise give rise to zoosporanges ; while in the Rhizidiese a process probably intermediate between oogamous reproduction and isogamous con- jugation takes place. Of the four sub-orders, the first [Rhizidiece) is manifestly nearly related to the Mucorini and the Ancylisteae ; the second (C/(7^^^/^ji'/;7>(^) may be regarded as allied to the Rhizidie^e ; the third {Olpidiece) and the fourth {Synchyfriece) in all probability following the second. De Bary suggests ('Comp. Morph.,' p. 169) that in ZYGOMYCETES 345 this •order the whole group may be looked upon as a lateral branch of the Mucorini or Ancylistese successively modified (degraded) by aquatic parasitism, with its extremity represented by the Synchytrieae, Woronina (Cornu), and Rozella (Cornu). De Bary also discusses {loc. at.) the suggested relationship to such algge as Protococcaceae, Cha- racium, Chlorochytrium, &c. Apart from the possession of chlorophyll, the conjugation of zoospores in these algae separates them from the Chytridiace^, in which group such a process has not (at least as yet) been discovered. Granting a relationship of the simpler Chytridiaceae with Protococcaceae, &c., these might be regarded as leading up to Rhizidieae, Ancylisteae, and Mucorini ; unless one regards the Chytridiaceae as com- posed of two distinct sub-groups, Rhizidieae and Cladochytriese, related to Mucorini and Ancylisteae ; and the Olpidieae and Synchytrieae to Protococcaceae, &c. Only further research may determine these ques- tions of affinity. Sub-order i : Rhizidie.e. — The life-history of Polyphagus Euglenae Fig. 297. — Polyphao2is Euglena Now. A , zoospore with drop of fatty matter and nucleus. B, young plant attached to resting Euglena, e. C, zoosporange containing spores resting on empty pro- zoosporange, a. D, conjugation : a, the receptive individual ; b, the supplying individual ; ^. the swollen end of conjugation tube (rudiment of re^ting-spore) ; e, e, e, the Euglenae. E, portion of D five and a half hours later : b, empty, s, mature^ represent the same parts as in D. {A x 550, B, D, E, X 350, C X about 400.) (After Nowakowski.) (Nowak.), described by Nowakowski, furnishes us with the most highly developed type of the whole group. The mycele consists of very slender branching rhizoids, tapering each to a very thin point, and attaching themselves to the Euglena-hosts. The original germinating zoospore 346 FUNGI from which these arose remains, as it were, the centre of the systen-p of rhizoids, and, nourished by them, grows considerably in size. At length, when it has attained full development, it becomes a prozoosporange, since from it there grows out a thick, cylindrical, thin-walled process, into which all the protoplasm passes, and within which it breaks up- into zoospores. These, escaping, repeat the life-history. Zygosperms (or oosperms) are produced by the conjugation of gametes, which play unequal parts in the process. The one (supplying) individual is round and larger than the other (the receptive) individual. A rhizoid from the receptive individual places its apex in contact with the supplying indi- vidual itself, and begins to grow in girth. The cell-wall at the place of contact disappears, the protoplasm of both unites and passes into a swelling which has arisen on the conjugating tube of the receiving indi- vidual close behind the place of contact. This swelling then becomes the zj^gosperm, which is provided with a thick wall, sometimes covered with fine spines, appearing as early as the outset of the swelling process. It happens — though rarely — that the tubes of two or three receptive in- dividuals attach themselves to one supplying plant, and a corresponding number of zygosperms is thus formed. After a period of rest, the zygo- sperm germinates by producing a zoosporange. Generation after gene- ration of zoosporanges intervene between zygosperm and zygosperm. ' Which of the two should be called the male and which the female, is. not easv to determine. ... It is evident that we have before us an intermediate case between the ordinary forms of oogamous and iso- gamous conjugation.' (De Bary, loc. df., p. 163.) A series of incompletely-known forms may be placed beside Poly- phagus (Xowak.), viz.: — Physoderma (Wallr.) {pro parte), Rhizidium (A. Br.), Rhizophydium (Schenk), Obelidium (Xowak.), Chytridium {A. Br.), Phlyctidium (A. Br.). Resting-cells of some of these have been found, but their genesis is unknown. Sub-order 2 : Cladochytrie/E. — This is a small sub-order, the members of which mostly inhabit the tissues of marsh plants, and possess copiously branching mycelial rhizoids, bearing terminal and interstitial zoosporanges. The zoospores give rise on germination to a mycele like the parent one. Resting zoosporanges occur. No process of conjuga- tion is known either between filaments or zoospores. Cladochytrium (Xowak.) and Physoderma {^pro parte) compose the sub-order. Sub-order 3 : Olpidie.e. — The Olpidie^ are wholly destitute of a mycele, and the life-history, as described by Fischer for Olpidiopsis- Saprolcgnias (Fisch.), and O. fusiformis (Cornu), which inhabits species of Achlya, is a very simple one. The zoospores of O. Saprolegni^ per- forate the young mycelial hyphae of Saprolegnia, and, after a few days of ZYGOMYCETES 347 growth m amceboid fashion, a cell-wall is secreted, and each becomes a zoosporange. Swellings arise on the mycele of the host as the result of this parasitism. The zoosporange then sends forth a cylindrical process, which perforates the wall of the Saprolegnia, and through it the zoospores are discharged. The zoosporanges are either smooth and capable of emission of zoospores at once, or are covered with fine spines and capable either of emission at once or of resting. While the latter are generally formed under adverse circumstances, it seems to occur with some regu- larity that the zoospores of the smooth zoosporanges give rise to spiny zoosporanges, and vice versa. The life-histor}- of these two species may be taken as typical, and the incompletely-known species of Olpidium (A. Br.) doubtless conform to it. Sub-order 4 : Synxhytrie^. — The Synchytrie^ inhabit the epiderm of terrestrial Flowering Plants, in which they excite the production of small yellow or dark-red galls, owing to the abnormal swelling of the epidermal cells affected. Like the Olpidiese, they have no mycele, but they are distinguished from that sub-order by the formation of a sorus of zoosporanges. From the germinating zoospore an initial cell is formed, the contents of which break up into a sorus of zoosporanges. In Pycnochytrium (de By.) ( = Chrysochytrium, Schroet., and Leuco- chytrium, Schroet.) the initial cell is a re sting-cell, which eventually germinates by the gradual protrusion of its contents into a globular sac seated upon the extine. Within this sac the sorus of zoosporanges is formed by the division of the protoplasm. Each zoosporange pro- duces a considerable number of zoospores, which again give rise to resting-cells. In Eusynchytrium (Schroet.) an indefinite number of sorus-forming generations, which at once produce zoospores, intervene between resting-cell and resting-cell ; while in Synchytrium Taraxaci (de By.) the resting-cell produces a zoosporange without the intervention of a sorus, a process suggestive of the Olpidie^e. Xo conjugation of zoospores nor any sexual process has been observed in any member of the group. Woronina and Rozella, which inhabit Saprolegnieae, may be placed with Synchytrie^. De Bary {Joe. df., p. 170) treats as doubtful Chytridiace^ (i) Tetra- chytrium triceps (Sorok.), the zoospores of which are said to conjugate; and (2) Hapalocystis mirabilis (Sorok.), the /^oospores of which are described as conjugating within the mother-cell. The observations, however, require confirmation. Beyond the general reference to Professor de Bary's ' Comparative Morphology,' &:c., the student is specially referred to that source with regard to this incompletely-knov^n group. ;48 FUNGI Literature. De Bar)- — Beitr. zur Morph. u. Physiol, der Pilze, i. (Physoderma [Cladochytrium]). De Bary und Woronin— Beitr. zur Kenntniss der Chytridieen (Ber. Naturf. Ges. Freiburg, Bd. iii. ; and Ann. Sc. Nat., 5 ser. , Tom, iii.). "SVoronin — Xeuer Beitr. zur Kenntniss der Chytridieen (Synchytrium Mercurialis) (Bot. Zeit., 1868, p. 81). ^Voronin — Chytridium Brassiere (in his paper on Plasmodiophora, Pringsheim's Jahrb. wiss. Bot,, Bd. xi.). Braun — Ueber Chytridium, &c. (Monber. und Abhandl. Berl, Acad., 1855). Braun — Ueber einige neue Arten der Gattung Chytridium und die damit verwandte Gattung Rhizidium (Monber, Berl, Acad,, 1856), Cienkowski — Rhizidium Confervae glomeratae (Bot, Zeit,, 1857), Cohn — Ueber Chytridium, lic, (Nova Acta Leop. -Carol,, xxiv., Pt, i,, p. 142). Cornu — Chytridinees parasites des Saprolegniees (in Monogr. d. Saproleg., Ann. Sc. Nat., 5 ser., Tom. xv, , p, 112). Pisch — Ueber zwei neue Chytridiaceen (Sitzber. d. phys. med. Soc, zu Erlangen, 1884). Fischer — Ueber d. Stachelkugeln in Saprolegniaschlauchen (Olpidiopsis) (Bot, Zeit, , 1880). Fischer — Untersuch. liber die Parasitender Saprolegnieen (Pringsh. Jahrb., Bd. xiii. ), (Berlin Habilitationschrift, 1882), Fischer — Zur Kenntniss d, Chytridiaceen (Erlangen, 1884), Kny — Ueber Entwickelung des Chytridium 011a (Sitzber. d, Berl. Xaturf. Freunde. See also Bot. Zeit., 1871, p. 870). Nowakowski — Beitr'age zur Kenntniss d. Chytridiaceen (Cohn's Beitr. zur Biol. d. Pflanzen, ii, ), Xowakowski — Polyphagus Euglence {ibid., ii.). Schenk — Algol. Mittheilungen (Verhandl. d. Phys. ]\Ied. Ges. zu Wurzburg, Bd. viii. ). Schenk — Ueber d. Vorkommen contractiler Zellen im Pflanzenreiche (^Yiirzburg, 1858). Schroeter— Die Pflanzenparasiten aus der Gattung Synchytrium (Cohn's Beitr. zur Biol. d. Pflanzen, i.). Schroeter — Untersuch. liber die Pilzgattung Physoderma (Ber. d. Schlesischen Ges., 1882). Sorokin — Einige neue Wasserpilze (Tetrachytrium triceps) (Bot. Zeit., 1874). Sorokin — Uebersicht d. Gruppe Syphomycetes (Hapalocystis mirabilis) (Arbeiten d. Naturf. Ges. an der Univ. Kazan, 1874, Bd. iv.). (See Just's Jahresbericht, 1875.) Thomas — Synchytrium cupulatum (Bot. Centralblatt, xxix.). Order 4. — Protomycetace^. Protomyces macrosporus^ ^ng., to which there have recently been added a considerable number of species, many of them on insufficient grounds, is a parasite on Umbellifers, especially .-Egopodium Poda- graria, ]Meum athamanticum, and more rarely Heracleum sphondylium, inhabiting the intercellular spaces of the leaf, petiole, stem, flower-stalk, and pericarp. It possesses a branching septate mycele, at irregular intervals on which there are formed interstitially large somewhat oval ZYGOMYCETES 349 resting proga??iefanges, with a stratified membrane and dense contents. These persist when the mycele dies, and hibernate. After this period of rest, and on hberation from the decaying tissues of the host (in water), the intine, with the contents, bursts the extine, and, becoming free, constitutes the gametange. Within it a large number of minute short rod-shaped gametes are formed, while a portion of the proto- plasm remains unused in the process. These gametes are ejected, and, being without the power of spontaneous movement, they remain Fig. 298. — Protomyces macrosportis linger, a. a mature resting progametange ; b, gametange ; c, d, and e, further stages of the same in the development of gamete.', c shows the parietal protoplasm, d the same divided into gametes, e the gametes rounded oflf and separated from the rest of the parietal protoplasmic layer ( x 390). (After de Bary.) in more or less proximity to each other. A\'here pairs of gametes come together, they emit fine processes which conjugate, the whole having the appearance of a dumb-bell or of the letter H. The germi- nation of these has been obser\-ed on the epiderm of ^^Egopodium : it takes place by the emission from one of the original gametes of a germ-tube, to the nourishment of which the protoplasm of the united gametes contributes. This germ-tube, on entering the tissues of the host, repeats the life-history. Literature. De Bar}' — Beilr. zur Morph. und Phys. der Pilze, i. Yon Thiimen — Eine neue Protomyces Species (Hedwigia, 1874). Wolff — See footnote to de Bar}''s paper ' Protomyces microsporus und seine Ver- wandten' (Bot. Zeit., 1874, p. 82). Other litei'attire of systematic interest in Saccardd's Sylloge. Order -USTILAGIXE-E. The parasites which are grouped together under this name affect Flowering Plants of different natural orders, but are especially conspi- j:) o FUNGI cuous as causing diseases of grasses. As a rule the attack of the para- site is limited to one special region of the host, e.g. the ovary, or the whole flower, or the leaf, or the stem, or even, in a few cases, the root ; and when the fungus has attained its maturity, the result commonly is that the part affected has been destroyed with the exception of the epi- derm or integument and the remains of vascular tissue, and is replaced by a powdery mass of brown or black resting-spores. The mycele sends its long thin h3^phje mostly along the intercellular spaces, in many cases •emitting branched haustoria into the adjoining cells, and the resting- spores are formed either on all parts of the hyphae or on particular branches. The life-history, briefly stated, begins with the production from the resting-spore of a pro?nycele which bears sporid-like gametes ; these gametes conjugate in pairs, and the united pair either directly produce a new mycele, or sporids which do so. This mycele then bears resting- FiG. 299. — Tilletia caries Tul., germinating. In a, gametes on promycele, p. In b, ga- metes, s, conjugate in pairs. In c, a germ- tube proceeding from pair of gametes, s. .s', a sporid (x 460). (After Tulasne.) Spores again in another host. Varia- tions on this course of life-history will be mentioned later on. Though these conjugating gametes differ from those of Protomyces in their acro- genous origin on a promycele, they may yet be considered homologues of those, just as the acrogenous spores of Chsetocladium are undoubtedly homologous with the endogenous spores of Mucor. In Entyloma (de By.) the resting-spores are borne interstitially at indefinite intervals on the mycele, as in Protomyces ; in Tilletia (Tul.) they occur singly, and only terminally on the spore-bearing hyphas ; while in Geminella (Schroet.) they are borne, two together, in series throughout the length of the special hyphae. In Urocystis (Rabenh.), Sorosporium (Rudolphi), and Tuburcinia (Berk.) they are united, several together, into a kind of coil, which is invested with a transitory or a persistent integument. With the exception, perhaps, of Graphiola (Port.), the exact relationship of which to the Ustilagineae has yet to be determined, Sphacelotheca Hydropiperis (de By.), formerly Ustilago Hydropiperis, according to de Bary's description, affords the best example of a well-developed stroma. This fungus attacks the ovule of ZYGOMYCETES 351 Polygonum Hydropiper, and replaces it by a dense plexus of hyphae, •which exhibits a differentiation of a thick outer wall enclosing the "whole, a cylindrical columel, both colourless, and a dark-violet mass of resting-spores filling up the space between. An undifferentiated basal portion discharges the function, as it were, of a meristem, and adds new elements to wall, columel, and spore-mass. The fungus attacks only the ovule ; and as it grows thus in bulk, the unaffected wall of the ovary is burst, and exposes the brittle wall of the sporal mass, which breaks at the slightest touch, and sets the resting-spores free. The germination of the resting-spores, which are usually round or many-sided, and possessed of both intine and extine, the latter often covered with characteristic fine granulations, varies according as it takes place in water merely or in a nutritive fluid. In water only the resting- spores of Entyloma, Tilletia, Tuburcinia, and Urocystis produce a short promycele-tube, which bears simultaneously on its blunt apex a whorl, or • crown ' of elongated gametes, varying in number. ]\Iany species of Ustilago (Pers.) and Tolyposporium (Woron.) produce a promycele-tube which divides into a number of cells, from each of which bud off laterally rod-shaped sporids or gametes, somewhat as a yeast-cell buds off. The resting-spores of Thecaphora LatlA-ri (Kuhn) and Ustilago longissima (Tul.) give rise to a short slender promycele- tube, which bears an acrogenous sporid, or several serially ; while in Thecaphora hyalina (Fingerh.), Ustilago carbo (Tul.), and U. destruens (Tul.) it divides mto several cells, each of which produces, if any, only one sporid. The conjugation of gametes in pairs takes place either before or after separation from the promycele, by means of short or long cross hyphje, according to the distance between them. The product of this union is the outgrowth from the connected gametes of a mycelial germ- tube, or, as occurs in Tilletia, Entyloma, Tuburcinia, and Urocystis, sporids are produced on the outgrowth from the connected pair, and these then emit mycelial germ-tubes. In a number of forms gametes are constantly produced which do not conjugate, but give rise to mycelial germ-tubes, as sporids do, while in Sorosporium Saponarise (Rudolph.) the resting-spore itself emits the mycelial germ-tube directly, without the intervention of promycele, gametes, and sporids. What occurs regularly in these species may occur exceptionally in the case of individuals the gametes of which ordinarily conjugate ; that is, they may fail to produce gametes or sporids at all, or their gametes may fail to conjugate, either all of them, or, where the number of gametes is an uneven one, the odd gamete. In such exceptional mstances the 352 FUNGI resting- spore or the single gamete, as the case may be, produces a mycehal germ-tube, as a sporid does. When the resting-spores germinate in nutritive fluids, as the ex^ periments of Brefeld show, the product is, according to the species, either directly a mycele which bears spores, or an abundant yeast-like out- growth from the promycele. In cases where the resting-spores failed to germinate, they were permitted to do so in water, and the sporids so formed, on being introduced into a nutritive fluid, gave rise to myceles bearing acrospores, resembling, as the case might be, either the gametes or the sporids. Accessory acrospores resembling the sporids are borne on branches of the mycele of certain species of Entyloma before the production of resting-spores. The branches of the mycele which bear them protrude through the stomates and epiderm of the host. They probably give rise to new myceles, as the sporids do. The same thing occurs in Tuburcinia Trientalis (Berk.), only here the accessory spores differ in form from the promycelial sporids. They produce in this case un- doubtedly each a mycele which bears resting-spores. Brefeld regards the conjugation of the gametes as a merely vege- tative process, and in no way analogous to any sexual act. De Bary ('Comp. Morph.,' p. 182) subjects Brefeld's arguments to destructive criticism, while stating Brefeld's case in the fairest terms. "WTiile the student is referred to the source quoted for the details, it may be shortly stated that de Bary's arguments are broadly based on the regularity with which conjugation occurs, and on the fact that it takes place equally regularly in pairs, under the normal conditions of germination in water. He shows, besides, conclusively how the process differs from the well-known vegetative anastomosing of hyphas, &c. De Bary regards the higher forms of Ustilagine?e, such as the coil- forming Urocystis, Sorosporium, and Tuburcinia, and Sphacelotheca with its well-developed stroma, as connected through the simpler forms (e.g. Entyloma) with Protomyces. Both produce (in the one case acro- genous, in the other endogenous) conjugating cells of equal value. The next indicated ally is Cladochytrium, the spores of which are zoospores (a matter not affecting the homology), but these fail to conjugate so far as is known. At all events the nearest ally appears to be, in the present state of our knowledge, that group of Chytridiacese to which Cladochy- trium belongs, through Entyloma and Protomyces. The peculiarity is to be noted that in Protomyces and the Ustila- gineae the act of conjugation takes place at a stage of the life-history which bears no homology with the sexual states of other Phyco- mycetes. Z YGOM VCE TES 353 Literature. De Bary — Untersuch. liber die Brandpilze (Berlin, 1853). De Bar}' — Protomyces microsporus und seine Verwandien (Bot. Zeit. , 1874) (Enty- loma). Brefeld— Botanische Untersuchungen, v. (Leipzig, 1883). Cornu — Sur quelques Ustilaginees nouvelles (Ann. Sc. Nat., 6 ser. , Tom. xv.). Fischer von Waldheim— Beitr. zur Biologie und Entwickelungsgesch. der Ustilagi- neen (Pringsh. Jahrb. , Bd. vii.). Fischer von Waldheim — Les Ustilaginees et leurs plantes nourricieres (Ann. Sc. Xat., 6 ser., Tom. iv. ).. Ed. Fischer — Beitr. zur Kenntniss der Gattung Graphiola (Bot. Zeit., 1883). Kuhn — Die Krankheiten der Culturgewachse (Berlin, 1858). Prillieux— Quelques observ. sur la formation et la germination des spores des Uro- cystis (Ann. Sc. Xat., 6 ser., Tom. x.). Schroeter — Bemerk. u. Beobacht. liber einige Ustilagineen (Cohn's Beitrage zur Biologie der Pflanzen, Bd, ii.). Tulasne — Mem. sur les Ustilaginees comparees aux Uredinees (Ann. Sc. Xat., 3 ser., Tom, vii.). Tulasne — Second Mem, sur les Uredinees et les Ustilaginees [ibid., 4 ser., Tom. ii.). Ward — Entyloma Ranunculi, Proc. Roy. Soc, xli. (1886), Winter — Einige X'otizen liber d. Fam. d. Ustilagineen (Flora, 1876). Wolff — Beitr. zur Kenntniss der Ustilagineen (Bot, Zeit., 1S73). Wolff— Der Brand des Getreides (Halle, 1874). Woronin— Beitr. zur Kenntniss der Ustilagineen (Tuburcinia). (De Bar)' und Woronin's Beitr. zur Morph. u. Phys. d. Pilze, v.). The older literature xvill be found quoted in Tulasne, Fischer von Waldheim, and in de Barfs ' Brandpilze. ' GROUP II.— SPOROCARPE.^. Class XX — Ascomycetes. The Sporocarp. This large class is distinguished by the universal formation of spores in asci, for the most part tubular in shape, but sometimes broadly ovate or roundish, and borne terminally on special hyphas termed ascoge?ioiis hyphce. When an ascus has reached its full size, and only then, the formation takes place within it of ascospores by free-cell formation. The young ascus is at first filled with finely granular protoplasm, which con- tains a nucleus, and within it a smaller body, probably a nucleole. The protoplasm next gathers itself together at the upper part of the ascus, while a watery fluid occupies the remainder of the cavity except a thin A A 354 FUNGI layer of protoplasm coating the wall. At this stage the full growth of the ascus is commonly reached, and the formation of ascospores begins with the division of the nucleus into two ; then by the same process four appear, then eight, which in the majority of cases represents the number of ascospores. In many Ascomycetes, however, other numbers typically prevail, e.g. one, or two, or four, or sixteen, fort}', fift}', and so on to over a hundred. Dothidea (Fr.), for example, has two to four, Sor- daria (Ces. and De Not.) four, sixteen, sixty-four, and one hundred and twenty-eight. Whatever the number, the nuclei always possess the same 'Mm Fig. 2f>o.~Peziza (Pyronefna) co7ifluens P. a, small portion of hymenium ; /, paraphyse attached to, not originating in, hyphal branches from which the three asci spring ; ;«, young asci ; 7-— w, successive stages, according to letters, in the development of ascospores within asci (x 390). (After de Bary.) Structure in all stages of multiplication, but they become smaller in size as the number advances. Round each nucleus there gathers a clear mass of protoplasm, and ultimately this becomes enclosed by a mem- brane, and, growing in size, thus develops into a spore. The ascospores are arranged in a series, one over the other within the ascus. The protoplasm left over within the ascus and outside the spores differs from that within the spores in exhibiting a reddish or violet-brown colour after treatment with iodine solution. De Bary originally proposed the term ' epiplasm ' for this portion of the contents ; but, Errera having ASCOMYCETES 355 shown that it contains a relatively large proportion of glycogen, he has more lately (' Comp. Morph.,' p. 7 7) adopted for it the term glycogen-mass or simply the glycogen. In certain cases the separation of the glycogen from the protoplasm takes place before the formation of spores, the former occupying the lower part of the ascus, and in some instances both the apical and the basal portions on either side of the protoplasm in which the nucleus is situated and the ascospores are formed. Such are the asci which characterise the great class of Ascomycetes. They are borne as a rule in considerable numbers mostly between hair- like bodies, \.h.Q paraphyses, and united into hymenia within special j;^6'r(^^:> .the carpogone and form the single-layered outer perithecial wall. From the inner surface of the cells composing this wall there subsequently .arise a number of other cells forming an inner wall several cells thick. The growth of these separates the antherid from the carpogone, and it takes part in the formation of the outer wall. From the outer wall, the cells of which have become larger and brown in colour, fine rhizoids are produced near the base, and in some species a few fine hairs at the apex termed appendiadce. ^Meanwhile the carpogone has divided into two cells, one the ultimate ascus, and the other its pedicel-cell. Within the ascus finally eight ascospores are formed. In Erysiphe (Hedw.) the chief points of difference from Podosphsera Fig. 303. — /, //, Podospho'ra papulosa de Bj^. and Wor. /, chain of spores on sporophore and mycele. II, ripe sporocarp with ascus, a, emerging through wall of sporocarp, h. HI — V, /'. Castagnei de By. and Wor., fertilisation. Hi, c, carpogone : p, antherid. //', older state : h, hj-phal branches of envelope. V, still older state in optical longitudinal section ; a, ascus (x eoo). (/, //, after Tulasne, /// — V, after de Ba^^-.) to be noted are these. The antherid winds spirally round the club- shaped carpogone, which divides into a series of cells — produces a number of asci — and the inner wall of the perithece is more developed. The germinating ascospore gives rise to a mycele provided with haustoria, on a suitable host, and from this thallus there spring short sporophores which produce successively a series of acrospores. The acrospores in turn produce a mycele exactly like the primar}- one from the ascospore — which like it, if completely developed, ends by bearing the sporocarp again. But owing to external conditions such as varying weather, nutrition, and the like, this consummation is frequently not reached, and acrospores only are then formed generation after generation. 364 FUNGI For example, the acrospore form called Oidium Tuckeri (Berk.), which occurs abundantly, and is well known as vine-mildew, never produces irt Europe, so far as is known, peritheces. These it is believed have been found on native vines in North America, which is supposed to be the home of the disease, the perithecial form being the fungus described as. Erysiphe (Uncinula) spiralis (Berk, et Curt.). The Erysiphe^ are parasites infesting living flowering plants of many natural orders. Among the best known and most destructive are the above-mentioned vine-mildew ; E. lamprocarpa (Lk.) on Compositse, Plantago, Verbascum, Labiates ; E. graminis (Lev.) on grasses ; E. Martii (Lev.) on Umbellifer^, clover, lucern, lupins, &c. ; E. communis (Lk.) on Polygonum, Rumex, Convolvulus, Dipsacus, Lathyrus, Delphinium, x\quilegia. Ranunculus, &C. Podosphaera Kunzei (Lev.) attacks species of Prunus, and Podosphsera Castagnei (de By.) is a well- known mildew of hops, though it also attacks many other plants of different natural orders. 2. EuROTiUM (Link). — The carpogone is formed by the rolling up in corkscrew fashion of the tip of a mycelial hypha, the turns of which, four or five in number, gradually come into closer contact till they pre- sent the appearance of a hollow screw. It is then divided by transverse walls into as many cells as there are turns in the screw. From the bottom turn of the screw there grow up two or three branches of irregular diameter, which take an irregular course towards the apex, but remain in close contact with the outside of the carpogone. Sometimes one ascends by way of the inside of the screw. One, however, chmbs faster than the others and reaches the apex first ; this is the antherid. Im- pregnation by it having taken place at the apex of the carpogone after the absorption of a minute portion of the wall, both the antherid and the other branches of the basal turn of the carpogone which follow it proceed to branch copiously, the hyphte being septate, until the carpo- gone is completely enveloped. In this way the outer perithecial wall is formed as in the Erysipheae. From it, as in the last type too, the inner wall grows inward, filling up the space between the outer wall and the carpogone with several layers, and pressing apart the turns of the screw. The wall-cells are of a pseudo-parenchymatous appearance, and the membrane of the outer wall becomes covered externally by a golden-coloured substance. The whole of these envelope-cells, it should be mentioned, increase in volume considerably. From the carpogone there now proceed numerous ascogenous hyphas, which press among and suppress the inner wall-cells, and, branching plentifully, bear at the ends, of the branches oval asci. These contain each eight ascospores. Sa copiously does this take place that, of the ascogenous hyph^ soon only ASCOMYCETES 36: the'traces may be seen, and by the time of maturity even the ascus-walls disappear and the perithece contains little but ripe ascospores. "When the ascospore germinates it produces a mycele, on which there shortly arise upright sporophores v;ith round swollen apices bearing numerous short sterigmata over the surface. On the sterigmata chains of acrospores are formed successively, which, proceeding radially from the a-j-.. Fig. 304. — Etirotuan repens de Bj^. A, branch of mycele with sporophore, c, and sterigmata, st : early stage of carpogone at as. B : spirally twisted carpogone, as, antherid, p, and an envelope- hj-pha. C, older state with more envelope-hyph^e. D, young sporocarp. E and F, young spo- rocarps in optical longitudinal section. In E the inner wall is beginning to be formed ; iv, the outer wall ; f, the nner wall and other cells filling space between it and carpogone. G, ascus with spores. H . ascospore of ^. Jierbariorian Lk. (^A x 190, the others x 600.) (After de Barj'.) apex of the sporophore, surround it with a globular mass of acrospores. The course of development is the same here as in the Er}-sipheas, and generation after generation of acrospores is usually formed in succession without the myceles attaining to the formation again of the sporocarp — this being the result of the external conditions of life of the fungus. 366 FUNGI The species of FAirotium are saprophytes, and are found inhabiting decaying plants, fruits, &c., and forming in such situations a loose mycele of delicate thin-walled cells. The common mould formerly called Aspergillus glaucus (Link) is the acrospore stage of Eurotium herbariorum (Link), and was believed to he an independent form before de Barv discovered the pleomorphism of this fungus and identified it with the sporocarp stage (Eurotium). 3. Pexicillium (Link). — The sporocarp of Penicillium takes its- origin in the winding; round each other once or twice of two lateral branches of mycelial hyph^e. These are so like each other that it is im- possible, from the observations made on them, to say which is male and which female — a question on which the ultimate development throws no light, since it is uncertain whether the ascogenous hyphse proceed from either or from both, and moreover, besides being alike in formation, they are equal in activity. Neither has any observation been made of the conjugation of these presumptive sexual elements— though their position towards each other signifies a sexual union. Together with the out- growths from these of numerous short ascogenous hyphce, there arises from the neighbouring hyph^ of the mycele a dense growth which com- pletelv envelops the presumptive carpogone and becomes interlaced with the ascogenous hyphse proceeding from it — these being at first thicker hyphse than those of the envelope-tissue. However, with the growth of the whole body, the cells of the envelope increase considerably in volume, especially the central mass, and acquire thickened pitted cell- walls, while the layers nearer the circumference form themselves into an outer wall the cells of which have yellowish-brown membranes. The whole has a pseudo-parenchymatous appearance. The originally outer- most cells are cast off, owing to their taking no part -in the growth. V\'hile this development of the envelope has been going forward, the ascogenous hyphas have been pushing in between the interstices of the cells, and sharing in the process of thickening of the cell-membranes. At this stage of the history of the sporocarp a period of rest intervenes lasting about six or seven weeks. This past, the ascogenous hyphss begin anew their growth in vigorous fashion, and, branching copiously at the expense of the cells of the envelope, ultimately produce at the ends of the branches short thick twisted terminal branches, which bear serially strings of asci containing each eight ascospores. So far is this process carried that finally not only is the whole interior envelope-tissue used up. but the asci themselves disappear, leaving enclosed by the outer wall only a dense mass of ascospores. De Bary compares the exist- ence here of two forms of ascogenous hyphas — viz. the relatively slender form which traverses and uses up the envelope-tissue, and the short ASCOMYCETES 367 twisted thicker form which bears the asci — with the occurrence of the two forms of hyphc^ in the ripening sporocarp of Elaphomyces. Some authors, it may be remembered, place Penicillium and Elaphomyces side by side. The germinating ascospore produces a mycele in all respects like that which bore the sporocarp, a much-branching anastomosing septate flocculent iiiycele, which bears acrospores serially in succession at the end of their characteristic sporophores. The sporophore arises from the mycele in the form of an upright septate stalk, which bears at its summit cymose branches ending in sterigmata of equal height. On the sterigmata are the chains of acrospores. Such a sporophore has a brush-like appear- ance, the stalk being the handle, and the branches, sterigmata, dsic. the hairs. The sporophores arise in dense masses, and in all produce enormous numbers of spores. So densely do they occur in exception- ally favourable situations — in the case of Penicillium glaucum (Lk.) — that they are sometimes bound together in bundles, fasciated as it were, and bear at the summit a dense crown of chains of spores. This form was originally described as a distinct genus by the name of Coremium glaucum (Lk.}. As in Erysiphe and Eurotium, so in Peni- cillium, the course of development, after the production of acrospores, may omit the formation of the sporocarp on the same thallus through external conditions being unfavourable to its development. This, in fact, is the usual case in Penicillium, and generation after generation of thalli bearing acrospores only, and there stopping short, inter^-ene as a rule between sporocarp and sporocarp. Perhaps the commonest of all moulds is Penicillium glaucum (Lk.), occurring on decaying fruits, on bread, c\:c., &c., in the acrospore-bearing condition. The sporocarp occurs, very rarely, in dark places where there is a poor supply of oxvgen, and mostly on bread. 4. GvMXOASCUS (Baranetsk.) and Ctenomvces (Eidam) do not differ in any very striking peculiarity from types already discussed. The origin of the sporocarp is characterised by the fact that while one sexual hypha entwines the other, it is the entwining one which is the carpogone — which subsequently produces the ascogenous hyphae — and the other, round which the carpogone winds, is the antherid. The relative posi- tions of these certainly recall the case of Eurotium, where the antherid occasionally ascends by way of the inside of the screw ; but here, on the other hand, the carpogone takes, as it were, the active step, and winds round the antherid. These have their origin as lateral shoots either of the same hypha or of different hyphce ; or it may be that only the entwining one (carpogone) is a lateral shoot, and the other merely the intercalary portion of a hypha. The ascogenous hyphas branch 368 FUNGI •copiously, and ultimately bear at the ends asci containing each eight ascospores, and the envelope-tissue is contributed by shoots from the neighbouring mycele and from the base of the carpogone. As already mentioned above, no acrospore stage intervenes here between sporocarp and sporocarp, i.e. the ascospore, on germinating, produces a thallus, which again bears the sporocarp directly. Gym- noascus is a saprophyte growing on dung. 5. AscoBOLUS (Pers.). — The carpogone arises on the mycele in the form of a thick curved sausage-shaped lateral hypha, which becomes ■divided by transverse walls into six or seven cells, about as long as they are broad. While in this stage the a .r\ farther end of it is clasped by the branching end of a much thinner hypha — like one of the ordinary my- celial hyphas— which, it may be as- sumed, is the antherid, from analogy with those types already discussed. At all events, it soon loses its iden- tity in the dense growth of envelope- hyphse which, immediately after this stage has been reached, are produced both from the ordinary mycele and from the hyphae which bear the carpogone and presump- tive antherid. These envelope- hyphae, w^hich soon enclose the carpogone in a round mass with a differentiated rind, next proceed to develop in the upper region over the carpogone (which is situated in the basal portion) the sub- hymenial layer of a discocarp. From this subhymenial layer there rise upward the straight perpendicular paraphyses. By the time the development has gone so far, the carpogone gives rise to a dozen or more ascogenous hyphae from a cell near the middle of the row, which has manifestly obtained from its neighbours contributions from their contents. The ascogenous hyphae grow upward to the subhy- menial layer, where they branch and spread about among the roots, so to speak, of the paraphyses, and here bear asci. The asci grow straight upward among the paraphyses to the hymenial surface. The portion of the rind (envelope-tissue) immediately over the hymenial surface is ruptured, in consequence of the expansion of this surface Fig Ascobohcs furfia-acciis Pers. Young sporocarp in longitudinal section (diagram- matic), in, mycele ; h, hymenium ; c, car- pogone with ascogenous hj-phae, j, in the subhymenial layer, and a, asci (shaded) ; /, antherid : p—r, tissue of envelope giving rise to paraphyses. (After Janczewski.) ASCOMYCETES 369 during growth, to permit the escape of the ascospores, and as new asci are produced (mostly taking the place of older ones), the expansion often continues till the hymenial surface becomes convex. Ascobolus, like Gymnoascus, has no intervening acrospores, and the germinating ascospore gives rise to a thallus which bears the sporocarp directly. It is a saprophyte, and the species abound on dung. 6. Pyronema (Fckl.). — Pyronema confluens (Tul.) (or Peziza con- fluens, Pers., as it was formerly called), which, when mature, forms a dis- cocarp like Ascobolus, differs considerably from that genus in the struc- ture of the carpogone and antherid, though both, doubtless, belong to Fig. -^od— Pyronema. conjluens Tul. A : c, carpogones ; a, antherids ; t, trichog>'nes. The tri- chogyne marked t has not yet become united with a. B, older state. The tnchogyne /, proceed- ing from carpogone c, and cut off by a transverse wall, is in open union with a. C : the antherid, a^'is in communication through t with carpogone, c, which is swollen and emitting ascogenous hypha; (x about 300). (From de Barj', after Kihlman.) the same main type in this respect. On the mycele of Pyronema con- fluens there arise clusters or rosettes of more or less club-shaped cells by forked branching at the summits of erect hyphse, occurring generally in pairs ; these pairs in turn having their origin in densely branched groups of hyphse. The rosettes consist each of three kinds of cell : the broad club-shaped, slightly curved cells are carpogones, and are usually borne on two pedicel- cells : the antherids are also club-shaped, of the same height, but of about half the breadth ; and the third kind are sterile cells of cylindrical form. Two or three pairs of carpogones and antherids are included in each rosette. From the top of the carpogone there grows forth a slender curved trichog}-ne, with plentiful supply of E B 370 FUNGI J protoplasm ; and this organ, instead of behaving passively in the opera- tion, bends over till it touches the top of an adjoining antherid, to which it adheres. When this has taken place, the trichogyne becomes separated by a transverse septum at the base from the carpogone, and then, through the dissolution of the intervening membrane, the contents of trichogyne and antherid are mingled. After impregnation the carpogone- increases in volume, and from numerous points of its surface there are emitted ascogenous hyphce. From the sterile cells and the whole basal' region of the rosette, the envelope-hyphse now grow forth and form a large sti'oma enclosing the carpogones and antherids — the latter re- maining almost unaltered, full of protoplasm, and taking no part in the formation of the envelope — and upon the stroma a free hypothece bearing the paraphyses. In the production of asci and the farther development of the apothece, Pyronema agrees with Ascobolus. Pyronema, like x\scobolus and Gymnoascus, produces noacrospores; and sporocarp follows sporocarp without intervention on successive thalli. 7. SoRDARiA (Ces. and de Not.) and Melanospora (Corda), both Pyrenomycetous forms, are placed next Ascobolus by de Bary with respect to the morphology of their sporocarps — of course excluding such, differences of form as are peculiar to their being Pyrenomycetes, while Ascobolus is, as has been shown, a Discomycete. Fundamentally there is little real difference in the mode of origin of the sporocarp ; and Chastomium and Ascotricha may eventually prove to belong to the same series. 8. CoLLEMACE^. — In the Collemacese, a group of discocarpous lichens, the structure, development, and mode of behaviour of the male sexual element is wholly different from any hitherto described, while the carpogone remains of similar structure, though, of course, modified^ to meet the requirements of the changed conditions. The male cells are pollinoids formed in a flask-shaped antherid, somewhat resembling a perithece. It is sunk beneath the surface of the thallus, and opens- by means of a narrow neck. The flask consists of a wall of densely- compacted hyphae, giving off towards the interior a layer of numerous, delicate hyphae (sterigmata), which converge towards the central portion of the flask. These form at their apices successively in series numerous polhnoids, which soon fill the central space. The pollinoids are thin- walled rod-shaped cells, with an outer membrane of a gelatinous kind, readily swelling and dissolving in water. In damp rainy weather water gets access to the pollinoids, and through the swelling action mentioned; they are forced out through the neck of the antherid and dispersed over the ■ surface of the thallus. The development of the antherid; ASCOMYCETES J/ generally somewhat precedes the origin of the carpogone. Under the surface of the thallus a hypha not distinguishable from its neigh- bours gives off a broader lateral branch, which coils itself up two or three times, and then sends forth the tip of the coil, which, growing upward, emerges through the surface of the thallus into the open. The tube is commonly somewhat swollen as it passes through the superficial tissue, and for some short distance above it, and attains a height above the surface of four or five times its breadth. This is the trichogyne. The coil as it grows is divided by transverse walls into about a dozen thin-walled cells, and the trichogyne likewise into a similar number. Its development having taken place, and the suitable conditions of moisture having dispersed the poUinoids over the surface, these, wher- FiG. 307. — A, Lej>togiia7t jnicrophylhim Ach., section of thallus. a, point of trichogj-ne ; ^, algal cells ; h, hyphae. B, CoUeitza pidposnm Bernh., young carpogone. C, tricho- gyne with poUinoids of L. jnicrophylhim. D, a similar one showing union with polli- noid. {A X 350, B, C, D x 750.) (After Stahl.) ever they come into contact with a trichogyne, stick to it, sometimes in considerable numbers, and an open communication between pollinoid and trichogyne is established by means of a short minute process from the pollinoid. When this has been accomplished the cells of the trichogyne collapse, remaining distended only where a transverse septum occurs in its course, while the cells of the coil increase in volume and in number through the growth of fresh transverse walls. The neigh- bouring thallus-hyphae then give out numerous shoots, which not only grow round the coils, but press them asunder. The hyphse on the side next the surface then give off branches in that direction, the end shoots of which form the first paraphyses, after displacing the intervening tissue in their course. The enveloping hyphse extend laterally until a basin- B B 2 !72 FUNGI shaped pseudo-parenchymatous exciple is formed, the margin of which reaches the surface. The interior of this basin is then soon filled with upright paraphyses like those which originally attained the surface. The turns of the original coil become unloosed, and eventually there are given off from it ascogenous hyphae which, after branching in the sub- hymenial zone like those of Ascobolus, finally produce successive asci in the mature apothece. In Physma Massal. the carpogone is produced from the hyphse which form the wall of the antherid, and the trichogyne rises to the surface outside the wall. Eventually the paraphyses and asci are pro- duced in the place formerly occupied by the sterigmata of the antherid, Fig. 308. — Lcptogiuvi inicrophylhun Ach., young apothece in section, /z, hj^phae : g, algal cells; a, thalloidal exciple ; b, exciple proper ; c, hypothece. The apothece is filled with paraphyses, among which may be seen bladder-shaped ascogenous hyphae with three j^oung asci ( x 530). (After Stahl.) and the antherid is thus transformed into the sporocarp. The species of Collema (Ach.) have no acrospores, and resemble in the course of their life-history Ascobolus, Pyronema, &c. For structure of hchen- thallus, see p. 318. 9. PoLYSTiGMA (Pers.) is a genus of parasitic fungi bearing a striking resemblance to the Collemaceae in its sexual reproductive apparatus. Antherids and pollinoids are formed differing in no material respect from those of the Collemace^ — the pollinoids being in this case more thread-like and bent. The genesis of the sporocarp is characterised here, however, by the formation of a fundamental coil of hyphas smaller than the thallus-hyphae. The carpogone appears among these, consisting of a spirally-wound hypha of two or three turns, with broad short cells. ASCOMYCETES 373 It traverses the fundamental coil, and its apex grows out as a trichogyne which protrudes through a stomate of the leaf of the host-plant. PoUinoids have been observed attached to it, but so far no actual communication has been detected. Accompanying the trichogyne are a few fine hyphae, which, after the collapse of the trichogyne, protrude through the stomate like the tip of a small brush. The farther development of the sporocarp (the envelope-tissue arising from the fundamental coil) is like that of the last type, with this difference, that, instead of an apothece, it is a perithece which is here produced. The ascospore produces on germinating a short promycelial tube, the end of which bears a sporid. The sporid, on germinating in turn on the leaf of a suitable host (Prunus), sends its germ-tube through the outer wall of the epiderm, and branches within the epidermal cell, these branches again penetrating into the parenchyme of the leaf. Here a thallus is formed, which remains covered by the epiderm of the leaf of the host until the sporocarp is again produced. 10. XvLARiE.t, &c. — In Xylaria (Hill), Hypoxylon (Bull.), Ustulina (TuL), Diatrype (Fr.), Stictosphseria (Tub), Eut}'pa (Tub), Xummularia (Tub), and Quaternaria (Tub), we have the occurrence of a fundamental coil preceding the formation of the peritheces, followed by the gradual disappearance, as mentioned above for Xylaria, of ' A^'oronin'■s hypha,' which is formed in it, without its taking part in the fomiation of the ascogenous hyph^. These arise, together with the paraphyses, from the perithecial wall. Xo trichogyne is formed from ' A\'oronin"s hypha,' and there are no antherids. Before the formation of the peritheces in Xylaria there are borne on the same stroma in dense hymenia bodies which resemble acrospores, or it may be pollinoids. In this genus they have not been observed to germinate, though similar bodies germinate freely in Ustulina, e.g., and other genera. In Xylaria at all events they may be functionless pollinoids persisting in an organism in which indications of a carpogone (in the form of ' Woronin's hypha ') also still remain. 11. ScLEROTixiA (Fckl.). — The sporocarp of Sclerotiniasclerotiorum (de By.) is in the form of a disc at first cup-shaped, borne at the summit of a stalk arising from a sclerote. It takes its origin from an entangled primordial coil of hyphje with gelatinous membranes situated just beneath the dark peripheral cells of the sclerote. There are many such coils in each sclerote, but they do not all attain this farther development. The bundle of hyphae constituting the stalk of the sporocarp breaks forth, as has been said, from this region of the sclerote, the central portion of the hyphae arising from the coil, and the external hyphce from the ordinary tissue of the sclerote. In the growth of the stalk it has 374 • FUNGI been found impossible to trace any anatomical distinction between these elements, and therefore it amounts to no more than a probability that the hyphfe from the coil are the ultimate ascogenous hyphae ; while those from the tissue of the sclerote may furnish the envelope-tissue of the sporocarp. The main difference between the development of S. sclero- tiorum and S. Fuckeliana in this respect consists in the primordial coil of the latter originating not within the sclerote, but in the central portion of the bundle of stalk-hyphse after it has reached the external surface. S. sclerotiorum possesses, so far as is known, no intervening acro- spores. The germinating ascospore produces a mycele on which sclerotes are formed, and on these only the sporocarps again. S. Fuckeliana sometimes does the same, and de Bary has observed a single instance of the sporocarp being produced on the mycele without even the formation of a sclerote. The sclerotes of this species, however, frequently produce filamentous sporophores bearing acrospores, this stage being that formerly known as Botrytis cinerea (Pers.). It never happens that a sclerote bears both acrospores and sporocarps, either together or after each other. The primary mycele may bear acrospores directly without interfering with the subsequent production of sclerotes, but this does not happen often. The mycele produced by the germinating acrospores is similar in all respects to the primary one arising from the ascospore, with the reservation that it has a greater tendency than the other to the pro- duction of sporophores. In this species there are also often formed certain abortive acrospores, or it may be pollinoids. 12. Pleospora (Rabenh.). — In the origin of the perithece of Pleo- spora herbarum (Rabenh.), the traces of sexuality disappear from view, and indeed it is stated that the asci arise among the paraphyses as branches of the basal cells of the latter. In the life-history of this fungus a considerable number of forms are embraced. Besides the ascospores, which are compound multicellular bodies, there are in the second category acrospores of three sorts, viz. {a) Double or multicellular acrospores of rounded short cylindrical form, previously taken to be an independent species (Macrosporium Sarcinula, Berk.). Each such com- pound spore appears as a rule singly on its sporophore. {b) Conical pear- shaped likewise compound spores appearing in series, often in branching series. This was also formerly described as an independent species of Alternaria (Nees ab Esenb.). {c) A small form of acrospore recorded by Bauke, but not, according to de Bary, Cladosporium herbarum (Link), which, though placed in genetic connection with Pleospora herbarum by Tulasne, does not belong here. In the third category there are pycno- spores formed in pycnids interstitially arising on mycelial hyphae. The pycnids consist of a wall of several layers, from the inner surface of ASCOMYCETES 375 which there converge series of cells producing successively (terminally and laterally) pycnospores. These are about twice as long as broad, and very thin-walled, but surrounded by a hyaline gummy substance. Not only are all these forms on record, but the mycele shows a tendency to pass into a resting state, and single cells or groups of cells becom- ing detached add to the means of propagation. There is some contradiction involved in the accounts of the occurrence of some of Fig. 309. — Claviceps piirpiirea Tul. Longitudinal section of portion of sclerote, ///, in SphaccUa stage, producing conidiospores, c (much magnified). (After Tulasne.) these forms and the order of their succession given by Bauke and by Gibelli and Griffini, and further research may be expected to throw light on the matters in dispute, as also on the question whether or not we have here one species very rich in spore-forms or two species resembling each other, but each less rich in forms. 13. Claviceps (Tul.). — The peritheces of Claviceps purpurea (Tul.) appear as it were in a kind of capitulum (immersed in the same stroma), 76 FUNGI .1 '/ u V I Fig. 310. — Ear of rj^e with two mature sclerotes (ergot) of Claviceps pjci-f>ii7-ca (natural size). (After Luerssen.) borne on the summit of a stalk arising from a sclerote (the well-known ergot of grasses) ; tfie ascospores are filamentous in form, and on germinating produce hyphae at several points. When this takes place under suitable circum- stances on the pistil of grasses, the tubes enter,, and, besides penetrating the tissue, form at length a white hymenium on the surface. This hymenium consists of numerous cylindrical ste- rigmata, which bear acrospores at their apices. (This stage was described by Leveille by the name of Sphacelia. ) These are given off- in drops of a sugary juice which oozes out be- tween the flower-leaves in which the pistil lies. This juice, ' honey-dew,' is eaten greedily by insects, which doubtless eat the acrospores with it. These propagate the Sphacelia state. At the base of this acrospore-forming body the formation of the sclerote proceeds, and it ulti- mately replaces the ovary, emerging from the flower of the grass with its base seated on the floral receptacle. It gives rise in turn to the sporocarp again. The allied genera Cordyceps (Fr.) and Epichloe (Fr.) agree with Claviceps in the de- velopment of the sporocarp. Besides the above distinctly marked types,, the origin of the sporocarp and the life-history of a considerable number of other forms have been more or less completely investigated. It would be entirely beyond the proportions of the present book to enter into a description of these, and a discussion of the controversies that are bound up with the accounts of the multitude of incompletely known forms. The citation of the literature at the end of this section will guide the student to original papers, but he may also be referred here, as in so many other cases of difficulty, to de Bary's ' Compara- tive Morphology and Biolog}' of Fungi,' c^c, 1887, as containing an exhaustive and critical treatment of these more or less obscure forms. ASCOMYCETES 377 He will find there also more information on the development of the sporocarps (both discocarpous and pyrenocarpous) of the types Fig. -ijW.— Claviceps p7irpurca Tul. A, sclerote which has produced seven stromata. B, upper portion of a stroma in longitudinal section, i^, peritheces. C, longitudinal section of perithece. cp, ostiole ; sh, cortical tissue ; hy, inner tissue of stroma. D, ascus isolated. sp, ascospores issuing. (^, natural size, B slightly, C and D highly magnified.) (After Tulasne.) quoted than it is possible to give in this place without burdening the section beyond proportion with matter of no striking morphological significance. Homologies of the Organs. De Bary, the founder of the system of classification of fungi adopted in the present book, calls attention to the striking parallelism between Ascomycetous forms on the one hand and the Mucorini, Peronosporeas, and Saprolegnieae on the other. From the oosperms and the spores of the sporocarps there arises a thallus which closes its development \s\\.\\ the formation of sexual organs and the oosperm and sporocarp resulting from their union. In many cases the life-history is confined to this ; for example, from the Phycomycetes, Pythium vexans, &c. ; from the ^yS FUNGI Ascomycetes, Eremascus, Pyronema, and Ascobolus. In most cases, however, there intervenes the formation of non-sexual spores which may be in a species all of one sort, e.g., Erysiphe, Peronospora ; or of several sorts ; and such spores are, moreover, in many cases exceedingly alike. Eremascus might almost belong to the Mucorini (Piptocephalide^e), while on the other hand it is not wanting in the essential attributes of an Ascomycete. In the form of its sexual organs it completely resembles Penicillium, Gymnoascus, Eurotium, &c. Again, great agreement is to be recognised between the thallus, spores, and sexual organs of the Erysipheae (Podosphgera especially) and those of the Peronosporeae. . The resemblance ceases with the farther development of the results of sexual union, and at this point the groups diverge from the point of contact of Eremascus and Podosph^ra with the Mucorini and Perono- sporeae. Of course the envelope-apparatus of the asci is not included in any comparison, as being of purely secondary importance ; and since such envelope is actually wanting in Eremascus, the case is made the clearer. It is also pointed out that though the oogones of the Peronosporeae have no envelope, it is by no means impossible that such may be found, while the zygosperms of Mucorini, as has been shown, are sometimes provided with an envelope. On such evident grounds as these, cited from de Bar}^ ('Comp. Morph. and Biol, of Fungi,' p. 232), who enters minutely into the matter (as well as the subject of the sexuality of the Ascomy- cetes), the relationship of these groups with each other is abundantly established. Doubtful Ascomycetes. I. Laboulbenie.e. — The Laboulbenieae are a small assemblage of remarkable parasites on insects, attacking mostly water-beetles, but also other insects, including the house-fly. They possess no mycele, and occur fixed on the chitin of the insect attacked by means of a short process which serves as a haustorimii., if that name may be applied to it. Above this rises a stalk consisting usually of two cells, one above the other, bearing at the summit a simple perithece and a few lateral hairs (the appendage) composed of seriated cells sometimes having minute round swellings at their apices. Before the complete development of the perithece has been reached, there is emitted from its summit a short fine process, which may be a trichog}'ne ; and according to Karsten (Stigma- tomyces, Karst.) the minute round swellings on the hairs become free and attach themselves to the trichogyne. Doubt, however, has been cast upon the accuracy of this obser\'ation by the investigation of Peyritsch, who also attaches no great value to the suggestion that the so-called ASCOMYCETES 379 trichog)ne is fertilised by the contact with it of one of the young hairs. The perithece contains a number of asci, and these eight or twelve double ascospores. The ripe double ascospore attaches itself to a fresh host by one of its ends, and develops into the new plant. Fig. 312. — A : h — h, Stigjnatoinyccs Baeri Peyr. {St. M7isccz Karsten). A, optical longi- tudinal section of ripe specimen with organ of attachment at base ; the asci are seen through wall of perithece. a, ever^'where the appendage ; b, an isolated ascus with spores ; c — h, stages of development of perithece and appendage in order of letters. B, Laboiil- bc7iia Jlagcllata Peyr. a, the appendage. {,A, c, g, h x 350 ; b, d, e.f x 450 ; B x 125.) (After Pej-ritsch.) 2. ExoASCUS (Fiickel). — The species of Exoascus mostly attack fruits, and set up in them sometimes conspicuous deformities. While some of them possess a mycele which penetrates the parenchyme of the fruit, tScc. (e.g. E. Pruni, Fckl., E. deformans, Fckl.), others extend no farther than between the cuticle and the epiderm-cells. In the former case the terminal cells of the hyphcX which emerge from the surface 38o FUNGI become asci. In the latter case either certain cells become asci while others remain sterile or the whole body of hyph^e form asci. In E. alnitorquiis (Sadeb.) these asci have a pedicel-cell; in E. aureus (Sadeb.) there is nothing but asci left at maturity. When the ascospores ger- minate they give rise to a yeast-like sprouting. 3. Saccharomyces (Meyen). — The species of Saccharomyces occur in fermenting substances, and are well known from theirpower of convert- ing sugar into alcohol and carbonic acid. Among the familiar species are S. cerevisiae (Meyen) (ordinary yeast), S. el- lipsoideus (Reess), S. Pastorianus (Reess), al- coholic ferments which are apparently mere form- species. AVith these should be placed S. My- coderma of Reess, and Chalara Mycoderma of Cienkowski ; and the 'thrush' fungus S. albi- cans (Reess), which lives parasitically on the mu- cous membrane of the human digestive organs, but is also capable of ex- citing a feeble alcoholic sugar fermentation ui solutions. With the ex- ception of the last-men- tioned forms in which Fig. ■i\2-—Saccha7-oviyces cerevisice Meyen. a, single cell hyphae OCCUr, the SpCCicS of beer-yeast ; b, c, stages of sprouting ; d, colony of sprout- r o i cells ; e, cell with four ascospores ; f, one with two ; g, group of SaCCharOmyCCS are of ascospores with one sproutine: ; /;, further development of • n i r • i_ • u a similar group (/i X 750, the ^others much more). {e-h UniCellular tUUgl WhlCh after Reess.) incrcasc by sprouting. The cells, in which a nucleus has not been demonstrated, are round or oval in form, and the sprouting takes place in the form of a pro- tuberance, which gradually swells and becomes constricted and finally cut off by a wall at the point of origin. These new cells either separate at once, or chains or groups remain united as they have been formed. When such cells are cultivated, on the cut surface of a potato for example, certain cells may form asci, each containing two to four ascospores. These are at once capable of germination, which takes ASCOMYCETES 381 place by the sprouting process described, though they may retain the power of germinating for a longer period. This cell-increase by sprouting is, as has been seen, by no means confined to Saccharomyces, but occurs in other groups of fungi (e.g. Mucor), and the special character which entitles them to this place in the classification of fungi is the production of asci, which they share only with the Ascomycetes. They may therefore be regarded as much degraded Ascomycetous forms — the other alternative, that they are early forms from which typical Ascomycetes have developed, being disposed of by the establishment of the connection of this great group with the Phycomycetes as already described. Literature. Barenetski — Entwickel. d. Gymnoascus Reessii (Bot. Zeit. , 1872). 'De Bary— Ueber d. Fruchtentwickel. d. Ascomyceten (Leipzig, 1863). De Bary — Beitr. zur Morph. u. Physiol, d. Pilze, iii., 1870. De Bary — Exoascus Pruni (Beitr., i.). De Bary — Ueber einige Sclerotinien, &c. (Bot. Zeit., 1886). Bauke — Zur Entwickelungsgesch. d. Ascomyceten (Bot. Zeit., 1877). Bauke — Beitr. zur Kenntniss d. Pycniden (Nova Acta Leop., xxxviii. , 1876). Borzi — Studii sulla sessualita degli Ascomicete (N. Giorn. Bot. Ital. , x. , 1878). Brefeld— Botan. Untersuch., ii. and iv. ; compare also v. Brefeld — Mucor racemosus und Hefe (Flora, 1873). Brefeld — Ueber Gahrung (Thiel's Landwirthsch. Jahrb. , 1875, 1876). Cienkowski — Die Pilze der Kahmhaut (Melanges Biol. Acad. St. Petersb., viii.). Cornu — Reproduction des Ascomycetes (Ann. Sc. Nat., 6 ser., Tom. 11). Currey — On the Fructification of certain Sphaeriaceous Fungi (Phil. Trans. Roy. Soc, 1858). Eidam— Beitr. zur Kenntniss d. Gymnoasceen (Cohn's Beitr., iii.). Eidam — Zur Kenntniss d. Entwickel. d. Ascomyceten {ibid.). Eidam — Ueber Pycniden (Bot. Zeit., 1877). Engel — Les ferments alcooliques, 1872. Fisch — Zur Entwickelungsgesch. einiger Ascomyceten (Bot, Zeit., 1872). Fiiisting— De nonnullis Apothecii Lichenum evolvendi rationibus (Diss, inaug, Berol., 1865). Fliisting — Zur Entwickelungsgesch. d. Pyrenomyceten (Bot. Zeit., 1867, 1868), Eiiisting — Zur Entwickelungsgesch. Lichenen {ibid., 1868). Gibelli — Sugli org. reprod. del gen. Verrucaria (Mem. Soc, Ital, di Scienc. Nat., i.). Gibelli e Griffini — Sul polimorfismo della Pleospora herbarum (Arch. d. Laborat. di Bot. Crittog. Pavia, i., 1875). Gilkinet — Recherches sur les Pyrenomycetes (Ball. Acad. Belg., 1874). Hansen — Oidium lactis, &c. (Medd. fra Carlsberg Laborat., Bd. i. ). Hansen— Untersuch. iiber d. Physiol, u. Morph. d. Alkoholfermente {ibid.). Hansen — Untersuch. iiber d. Organismen welche sich zu verschiedenen Jahreszeiten in d. Luft finden, &c. {ibid.). Hansen— Untersuch. iiber d. Physiol, u. Morph. d. Alkoholgiihrungspilze {ibid., Bd. ii.). 382 FUNGI Hansen — Bemerk. liber Hefc'inlze (Allg. Zeitsch. f. Bierbrauerei, «S:c. , 1883; Bot^ Central bl., xvii.). Hartig — Wichtige Krankheiten d. Waldbaume, p. loi. Hartig — Untersuch. aus d. Forstbot. Institut zu Miinchen, i. Janczewski — Morphol. d. Ascobolus furfuraceus (Bot. Zeit. , 1871). Karsten — Stigmatomyces (Laboulbeniaceen) in Chemismus der Pflanzenzelle, 1869. Kihlman — Zur Entwickelungsgesch. d. Ascomyceten (Acta Soc. Sc. Fennicae, xiii. ^ 1883). Kral)be — Entwickel., Sprossung und Theilung einiger Flechtenapothecien (Bot. Zeit.^ 1882). Krabbe — Morphol. u. Entwickelungsgesch. d. Cladoniaceen (Ber. d. D. Botan. Gesellsch. , 1883). Kiihn — Mittheil. d. Landw. Instituts Halle, i. Lauder Lindsay — Spermogones and Pycnides of Lichens (Trans. Roy. Soc. Edinb. , xxii.). Low — Ueber Dematium pullulans (Pringsh. Jahrb., Bd. vi.). INIattirolo — Sullo sviluppo e sullo sclerozio della Peziza Sclerotiorum Lib. (N. Giorn. Bot. Ital., xiv.). Millardet — Mem. Soc. d'Hist. Nat. Strasbourg, vi., 1868 (Myriangium, &c. ). Pasteur — Mem. sur la fermentation alcoolique (Ann. Chim. et Phys. , Tom. Iviii., i860). Pasteur — Etudes sur la biere (Paris, 1876). Peyritsch — Ueber die Laboulbeniaceen, &c. (Sitzber. Wiener Acad., Bd. 64, Abth. I, 1871 ; Bd. 68, Abth. i, 1873 ; and Bd. 72, Abth. 3, 1875). Pirotta — Sullo sviluppo della Peziza Fuckeliana (N. Giorn. Bot. Ital., xiii. ). Rathay — Ueber d. Hexenbesen d. Kirschbaume (Sitzber. Wiener Acad., Bd. 83,. Abth. i). Reess — Botan. Untersuch. iiber d. Alkoholgahrungspilze (Leipzig, 1870). Reess — Zur Kenntniss d. Exoascus d. Kirschbaume (Sitzber. d. Phys. Med. Gesellsch. zu Erlangen, 1882). Reess — Ueber den Soorpilz {ibid., 1877 and 1878). Reess — Untersuch. ii. Elaphomyces granulatus (Deutsch. Naturf. u. Aerzte, Strass- burg, 1885). Reinke u. Berthold — Die Zersetzung d. Kartoffel durch Pilze (Berlin, 1879). Schwendener — Ueber d.- Entvvickelung der Apothecien von Ccenogonium (Flora, 1862). Schwendener — Ueber d. Apothecia primitus aperta u. d. Entwickel. d. Apothecien im Allgemeinen [ibid., 1864). Sorokin — Quelques mots sur I'Ascomyces polysporus(x\nn. Sc. Nat., 6 ser. , Tom. iv. ). Stahl — Beitrage zur Entwickelungsgesch. d. Flechten, i. (Leipzig, 1877). Van Tieghem— Chaetomium (Comptes Rendus, 81). Van Tieghem — Nouv. observ. sur le developpement du fruit, &c. , des Ascomycetes (Bull. Soc. Bot. France, xxiii., 1876). (See also Bot. Zeit. same year.) Van Tieghem — Sur le developpement du fruit des Ascodesmis {ibid. ). Van Tieghem — Nouv. observ. sur le developpement du perithece des Chcetomium {ibid.). Van Tieghem — Sur le developpement de quelques Ascomycetes {ibid., xxiv. ). Van Tieghem — Monascus, genre nouveau de I'ordre des Ascomycetes (Bull. Soc. Bot. France, 1884). Tulasne — Fungi hypogaei (Paris, 1851). ASCOMYCETES 383 Tulasne — Selecla Fungorum Carpologia, i.-iii. (Paris, 1861-65). Tulasne — Rech. sur I'organisation des Onygena (Ann. Sc. Xat., 3 ser. , Tom. i. ). Tulasne — Note sur I'appareil reproducteur des Lichens et des Champignons {ibid., 3 ser., Tom. xv.). Tulasne — Mem. pour serv. a Thist. organograph. et physiol, des Lichens {ibid., 3 ser., Tom. xvii.). Tulasne — Discomycetes {ibid., 3 ser., Tom. xx.). Tulasne— Mern. sur I'Ergot des Glumacees {ibid. ). Tulasne — Note sur I'appareil reprod. des Hypoxylees et des Pyrenomycetes {ibid.^ 4 ser., Tom. v.), Tulasne — Xouv. observ. sur les Erysiphes {ibid., 4 ser., Tom. i.). (See also Bot. Zeit., 1853.)^ Tulasne — Note sur les Isaria et les Sphceria entomogenes {ibid., 4 ser., Tom. viii.). Tulasne — De quelques Spheries fongicoles {ibid. , 4 ser. , Tom. xiii. ). Tulasne — Note sur les phenomenes de copulation d. L Champignons {ibid., 5 ser., Tom. v.). Tulasne — Super Friesiano Taphrinarum genere {ibid.). Vittadini — Monographia Tuberacearum (Mediolani, 1831). Vogel — Gjnnnoascus uncinatus (Bot. Centralblatt, xxix. ). Wilhelm — Beitr. zur Kenntniss d. Pilzgattung Aspergillus (Diss. Berl., 1877). Woronin — Entwickelungsgesch. d. Ascobolus pulcherrimus und einiger Pezizen (Beitr. zur Morph. u. Physiol, d. Pilze, ii.). Woronin — Sphseria Lemaneae, Sordaria, &c. {ibid., iii. ). Zopf — Zur Entwickelungsgesch. d. Ascomyceten (Cheetomium) (Nova Acta Leop., xlii.). Zopf — Die Conidienfriichte von Fumago {ibid., xl.). Class XXI.— Uredineae. The Uredineae are a class of parasites on flowering plants and ferns. They resemble the Ascomycetes in many points, as will be seen from this short account of them. The mycele is septate and much branched, follows the intercellular spaces of the host-plants, and penetrates the cells themselves by means of short branches. Puccinia graminis (Pers.) may be taken as a type of the course of development followed by some of the forms. Owing to the change of host involved in the course of development of this and other forms, and to the different appearances presented by succeeding stages of the organism, it was formerly supposed that these stages constituted distinct fungi. Thus no less than three form-genera (JEcidium, Pers., Uredo, Pers., and Puccinia, Pers.) were established to denote the stages of the life-cycle of Puccinia graminis, the well-known corn mildew. The sporocarp (^cidium) is formed in spring on the barberr}-. In its. >84 FUNGI Fig barberry s (slightly magnified). B, uredospores, u, and teleutospore, t. C, germinating uredospore {B and C x 390). D, teleutospores. E, germi- nating teleutospore : promycele. /, and spo- rids, j/ ( X 400). {A, B, D, and E oi Piiccinia g7-aviinis. C of P. stratiiinis Fckl., E teleuto- spore oi P. co7-onata Cord., x 300). G, teleuto- spore of Phraginidimn inci-assatii7it Link. ( X 300). (^, /^and G, after Luerssen ; B — Z>, after de Bar>' ; E, after Tulasne.) earliest stage it appears to consist of a densely interwoven mass of hyphge situated in the subepi- dermal parenchyme of the leaf. This gradually increases in bulk and displaces the surrounding tissue. As it grows the hyphae in- crease in size, and the shape of the whole becomes more definitely spherical. Within the base of this sphere the hymenium is developed, and consists of a continuous layer of club-shaped basids, from the sum- mit of each of which is produced in basipetal succession a single series of cecidiospores. Enclosing the sporal mass is a single layer of pseudo-parenchymatous cells aris- ing from the margin of the hyme- nium, and arching over the top of the spores. The cells composing the envelope are larger than the spores, and possess thicker walls, while their clearer contents contrast with the orange-coloured spores. The enlargement of the whole body increases until the epiderm is ruptured, while the tissues of the host are pushed aside and com- pressed. After the rupture of the epiderm the envelope bursts at the apex, and curves back, forming the lip of a cup-shaped body ; the sporal mass is farther elevated and the spores escape. These sporo- carps are situated on the under sur- 314. — .4, diagrammatic transverse section of - , -berry leaf with secidia, «, <^, and antherids. taCC OI the Icai, bUt aCCOUipanymg them on the upper surface there are to be found numerous flask-shaped antherids containing pollinoids produced at the apices of ste- rigmata, and in all points recalling UREDINEAl those already described in Collema. They are orange-coloured Hke the sporocarps, and the polhnoids have never been known to germinate. No corresponding female sexual organ occurs in any Uredine, though the early stages of the development of the sporocarp are not sufficiently known. No such body as Woronin's hypha inXylaria, for example, has ever been observed in the Uredineae, and the only suggestion of a female sexual organ is to be found in the occasional occurrence in some Uredines of short obtuse hyphae, projecting through the stomates of the host like the trichogynes of Polystigma. These may be traced, it is true, to young gecidia, but there may well be nothing more in the suggestion than the mere protrusion of mycelial hyphte, since observations connecting such filaments with an act of fertilisation are wholly wanting. Massee ('Annals of Botany,' 1888, p. 47) has recently published an ac- count of observations of a supposed sexual process in Uredineae, involving the fertilisa- tion of a carpogone by an antheridial branch ; but the subject stands in great need of farther mvestigation. Fig. 315. — Pticcinia graininis Pers. t teleutospore ; «, uredo- spores ( X 390). (After Sachs. ) The spores from the ripe sporocarp {ceci- diospores) germinate only on the leaves or stems of grasses, and the germ-tubes entering by way of the stomates give rise to mvceles, which attack the tissues of the host. In the course of a week or more, cushion- like masses of mycelial hyphae situated be- neath the epiderm give rise to erect basids, each of which bears a red uredospore (Uredo) at the apex. On the rupture of the epiderm the uredospores escape, and these alighting on grass plants germinate, again enterby way of the stomates, and renew the same generation. This process may and does go on indefinitely, and thus much damage is annually caused by the attack of this fungus on the corn crop. Later on there are developed on the same mycele, first side by side with the uredospores, then gradually replacing them altogether, two-celled spores called teleuiospores, and with their production the development of the fungus ceases for a period. In this condition the winter is passed. With spring they germinate, each of the two cells of the teleutospore (Puccinia) giving rise to a short promycele, the terminal cells of which . bear on slender stalks a single sporid apiece. These sporids germinate in turn on the leaves of the barberry, the germ-tubes piercing the epi- c c 386 FUNGI derm, and giving rise within to the mycele which ultimately bears the sporocarps and anthcrids. Gymnosporangium (DC.) represents another type of the course of development in Uredineae. The sporocarps (corresponding to aecidia, but here denoted by the form-genus Roestelia, Reb.) appear in summer on the leaves and fruits of Pomeae. No uredospores are formed. The next generation (teleutospores) is produced in spring on juniper in odd-shaped mucilaginous brown or yellow masses. Promyceles are formed which bear sporids, and these again set up on the leaves, &c., of Pomeae the sporocarp generation. A farther reduced type is to be found in Endophyllum (Lev.). In this case the germ-tube of the spores of the sporocarp (aecidiospores) becomes a promycele, and, dividing up into several cells, each of these bears at the end of a sterigma a single sporid. The sporid on germi- nating renews the sporocarp generation. Two cases of exceptional structure may be noted. In Phragmidium (Link) the sporocarps have no proper envelope, the place of the w^all being taken by a circle of club-shaped paraphyses surrounding the margin of the hymenia. On the other hand the uredospores of Me- lampsora populina (Jacq.) and of Cronartium (Pers.) are enclosed in an envelope resembling that of the sporocarp. The development of the paraphyses in the one case and of the envelope in the other requires investigation. Besides the sporocarp-forming Uredineae there is another group know^n as the tremelloid UredinecB, which do not possess a sporocarp generation. These are not to be confounded wath those Uredineae in which presumably from want of investigation the sporocarps are un- known. The course of development of the tremelloid Uredineae is per- fectly well known in a number of cases (Leptopuccinieae and Leptochry- somyxa, de By.), and consists of a teleutospore-bearing generation with commonly softer and more gelatinous spore-membranes. These teleuto- spores germinate as a rule at maturity and not after a period of rest. The sporids formed on the promycele produce a mycele which again bears teleutospores. Leptopuccinia malvacearum (Schroet.), L. Dianthi (Schroet.), &:c., bear the same relation in appearance, &c., to Puccinia as Leptochrysomyxa Abietis (Ung.) bears to Chrysomyxa (Ung.), the species of which form sporocarps, uredospores, and teleutospores. Enough has been said in this brief account to indicate a probable connection of the Uredineae with the Ascomycetes through their sporocarps. Those forms — the tremelloid Uredineae — in which the sporocarp generation may be presumed to have been lost, sufficiently resemble the complete types to be necessarily bound up with them ; UREDINE.E 387 while on the other hand, as will be seen, they furnish a valuable link with the next class. Literature. De Bary — Untersuch. liber die Brandpilze (Berlin, 1853). De Bary— Rech. sur le developpement de quelques Champignons parasites (Ann. Sc. Nat., ser. 4, xx.). De Bary — Ueber Cieoma pinitorquum (Monatsber. Berl. Akad., 1863). De Bary— Xeue Untersuch. iiber d. Uredineen [ibid., 1865, 1866). De Bary — Ueber d. Krebs u. d. Hexenbesen d. Weisstanne (Bot. Zeit., 1S67). De Bary — .^cidium abietinuni {ibid., 1879). Dieiei — Beitr. z. Morph. u. Biol. u. Uredineae (Bot. Centralblatt, xxxii., 1887, p. 54; ibid., 1888, No. 33). Farlo\v--The Gymnosporangia or Cedar Apples of the United States (Mem. Boston Soc. Nat. Hist., 1880). R. Hartig — Wichtige Krankheiten der Waldbaume (Berlin, 1874). R. Hartig — Lehrbuch der Baumkrankheiten (Berlin, 1882). Leveille— Sur la disposition methodique des Uredinees (Ann. Sc. Nat., ser. 3, viii.). Oersted- Om Sygdomme hos Planterne, «S:c. (Kjobenhavn, 1863). Oersted — On Podisoma and Roestelia (Oversigt k. Danske Vidensk. Selskab. Forhandl., 1866 ; and K. Danske Vidensk. Selskab. Skrifter, ser. 5, vii. \ Parker— On the Morpholog}- of Ravenelia gland ulceformis (Proc. Amer. Acad. Sc. and Arts, 1886). Rathay— Untersuch. iiber d. Spermogonien d. Rostpilze (Denkschr. d. Wien. Akad., 1883, Bd. xlvi.). M. Reess —Die Rostpilzformen d. deutsch. Coniferen (Abhandl. Nat. Gesellsch. zu Halle, Bd. xi. ). Schroter— Die Brand- u. Rostpilze Schlesiens (Abhandl. Schles. Ges. vaterland. Cultur, 1869 [1872]). Schroter— Entwickelungsges. einiger Rostpilze (Cohn, Beitr. i., Heft 3; ibid./m.. Heft I). Schroter — Ueber einige amerikanische Uredineen (Hedwigia, 1875). Schroter — Beobacht. iiber d. Zusammengehorigkeit von .Ecidium Euphorbice u. Uromyces Pisi {ibid., 1875). Tulasne— Mem. sur les Ustdaginees et les Uredinees (Ann. Sc. Nat., ser. 3, vii. ; ibid., ser. 4, ii. ). Ward — Researches on the Life-history of Hemileia vastatrix (Linn. Soc. Journ. B«>t., xix. ). Ward— On the ^Morphology of Hemileia vastatrix (Quart. Journ. Micr. Sc, N.S., xxii., 1882). R. Wolff— /Ecidium pini u. seine Zusammenhang mit Coleosporium Senecionis Lev. (Festschrift, Riga, 1876). In the above papers will be found references to older literature and farther memoirs on the group. For a systematic account the student is specially referred to Winter's Die Pilze Deutschlands, Oesterreichs und der Schweiz, in the new edition of Rabenhorst's Kryptogamentlora von Deutschland, &c.; and to Plo a light's British Uredinese and Ustilaginese (London, 1889). C c 2 388 FUXG] Class XXII. — Basidiomycetes. The Basidiomycetes are a large class comprising forms of the utmost diversity in appearance, mostly saprophytes living on humus, rotten wood, or the old wood and the bark of trees. A small number are parasites. They all agree in the production of spores {basidiospores) acrogenously on basids, which are club-shaped and disposed as a rule parallel to each other, thus forming hymenia. The spores produced on one basid are two or four in number, more rarely eight, though divergences from these numbers occur. They vary in shape, but consist, except in some Tremel- linese, of a single cell. Among the basids there commonly occur sterile hyphal branches — paraphyses. Besides these spores thus borne on definite hymenia there are also others produced more or less inde- finitely on the myceles of certain members of the group, and their character will be described below. The Basidiomycetes are divided into two sub-classes, the Hymenomycetes with gymnocarpous, and the Gasteromycetes wath angiocarpous fructification. Sub-class 1. — Hymenomycetes. The Hymenom5'cetes are characterised by the possession of a hynieiiiiim on the free exposed surface of the compound structure which bears it — the sporophore. The forms embraced in this sub-class range from very simple to highly complex structures, the latter being repre- /^ Fig. 316. — Tremella inesenterica Retz. (natural size). (After Tulasne.) sented by such types as the common mushroom and the like — in short those fungi to which the name is popularly applied. ExoBASiDiUM Vaccinii (Woron.) may be taken as the simplest type. Its mycele is parasitic on the leaves and stems of Vaccinium vitis-idasa, B AS IDIOM YCE TES 389 and forms on the surface a hymenium of club-shaped basids each of which produces four basidiospores. The spores divide at maturity trans- versely into four cells, only the two end cells of which germinate, doubt- less at the expense of the contents of the remaining two. The germ- tubes penetrate the epiderm of the leaf of the host, and a new mycele is formed which again bears basids. If, however, germination takes place elsewhere than on the proper host-plant, and conditions for the vegeta- tion of the fungus be otherwise favour- able, the germ-tube begins to sprout in- definitely by means of elongated sprout- cells^ giving rise to others only at the ends. This condition has been maintained in nu- trient solutions for a considerable time, but the sprout-cells have never been observed actually to give rise to a new mycele like the one produced by the basidiospores. The Tremelline^ (Tremella, Dill., Exidia, Fr.) present another simple type. They are gelatinous fungi of not very definite form, commonly of wavy outline, and are saprophytic on old and dead wood. The hymenia are formed on the surface of the gelatinous mass. The basids vary in appearance, and are usually provided with fine elongated sterigmata and reniform spores. Certain forms such as Sebacina (Tul.) and Hypochnus (Fr.) do not possess gelatinous membranes. The course of development is much the same as in Exobasidium. The germinating basidiospore gives rise under ordinary con- ditions to the compound sporophore again. Under other conditions, it has been observed m Dacryomyces, the germ-tubes do not grow to any great length, but produce secondary spores, or they form sprout-cells. The basidiospores of the same form divide transversely at maturity, usually into four cells, each of which may germinate. It should be added that on germination these secondary spores give rise to myceles. The hyphae of such myceles, moreover, as well as those proceeding from basidiospores, sometimes give rise to tufts of rod-like cells, which in turn produce myceles. Similar phenomena have been observed in other Tremelline-x. Fig. 317. — Exidia spiculosa Sommerf. Longitudinal section of portion of hymenium (much magnified). jt, spores ; b, basids : //, hyphae of thallus. (After Tulasne.) 390 FUNGI It is manifest therefore that in these simple types we have repeated very much the same order of things as in the tremelloid Uredineae. It is perhaps most striking in the case of Exobasidium, from which the transi- tion is easy to the TremelHneae. The layer of basids and basidiospores may ])e compared with the layer of teleutospores, while the transverse division Fig. 318. — Coprinns stercorariics Fr. A, B, and C, germinating spore in successive stages. D portion of mycele, w, with five early stages of development of fungus. E and F, further stages. G, longitudinal section through germinating sclerote, s, with young fungus still within volva, 7>. H, fully developed fungus with sclerote, s, and rhizoids, r. (A — Cx. 300, £> x 200, £ x 120, F X e^o, G and // natural size.) (After Brefeld.) of the basidiospores into four cells, two of which germinate, heightens the resemblance. Farther the production of secondary spores on the short germ-tubes of basidiospores recalls the formation of sporids on the BASIDIOMYCETES 391 promyceles from teleutospores. From the Tremelline^e another easy step leads us on to the Thelephoreae, and it may be borne in mind in this connec- tion that certain Tremellineae, as mentioned above, do not possess gelatinous membranes. The Thelephore.^ (Corti- cium, Pers.) may be shortly described as recalling in point of simplicity of structure the teleutospore-layer of Uredineae, while they approach very closely the club-shaped Hymenomy- cetes such as the Clavarieae, in which the hymenium is dis- posed on the outer surface of erect club shaped cylindrical and often much-branched com- pound sporophores. Through a series of intermediate forms, the completeness of which may f " be recognised from a systematic | study of the group, we proceed « to the more perfect types of Hymenomycetes which possess sporophores of more complex structure. In the higher forms of Hymenomycetes, the sporo- phore consists of a cap or pile us borne on the summit of a stalk or stipe. The mycele com- monly vegetates in a soil rich in humus or on old wood or the like, and though usually of loose filamentous texture it is in Fig. ;^ig.—A^arjc7(s 7neUeus L., in diffe- rent stages of development on branched rhizomorph-strands. The upper portion of rhizoniorph represents that formerly . known as Rliizo7norpha fragilis Roth, while the lower strap-shaped portion is var. subcoiticalis. (After Hartig.) 392 FUNGI certain instances of more compact character. Such are the sderotes which are resting states of Coprinus stercorarius (Fr.) (fig. 318), and the rhizo- morphs of Agaricus melleus (L.) (fig. 319), composed of root-Hke branched strands of rnyceHal hyphae, parasitic on the pine. The rhizo- morphs are simply sclerotes with growing-points. From the mycele, of whatever character it be, there arises the compound sporophore by the continued apical or marginal growth of a bundle of hyphge. It is not certain, but it may very well be, that intercalary growth also, in some Fig. 320. — Agaricus cavipestris'L.. The common mushroom (natural size). Stages of development from a \o e \ b and c in section. (After Luerssen.) cases at least, assists in the development. The hymenial surface, which is commonly situated on the under surface of the cap or pileus, is characterised in different genera by being spread over teeth-like projec- tions (Hydnum, L.), radial plates in the numerous species of Agaricus (L.), concentric plates in the small genus Cyclomyces (Kze.), reticulated folds or pores (Polyporus, ]Mich. Boletus, L.) ; such typical characters being united by a wealth of intermediate forms. As a rule these pro- jections are very symmetrical and of regular occurrence, and on them the chief generic characters are based in the classification of the group ; BA SID 10 M VCE TES Fig. ^■2\. — Coprimis stercorariiisYr. Longi- tudinal section of the end of a gill in com- plete spore-bearing. t. trama ; p. sterile palisade cells ; b, basids with spores ; f, cystids (x 300). (After Brefeld.) they are termed ^^///^ or lamellce in the AGARicixi,/^r«?.f or tuhidi in Polv- PORE.t, and teeth in the Hydne^. In many of the forms the hymenium is exposed from the first ; in a series of others a membrane {vehwi partiale) connects the edge of the pileus all round with the stalk, and on its rupture by the extension of the pileus, part of it is left attached to the stalk, when it is termed the annuhis or ring (fig. 320), though this does not occur in all cases. In a third series a membrane {vebivi universale ox volva) (fig. 318) encloses the whole sporophore, pileus and stalk alike, and in the species be- longing to Amanita, a sub-genus of Agaricus, both velum universale and velum partiale are present. In these latter cases, therefore, in which a membrane is present, the sporophore differs from the truly gymno- carpous forms. The de- velopment of Amanita is especially noteworthy, since the gills are not developed on the free inner surface of the pileus, but during an early condition from tissue common to both stalk and pileus. Immediately beneath the hymenium is a layer of tissue called the sub- hymenial layer, distin- guished from the rest of the tissue of the sporo- phore by the greater density of the ramifica- tions of the hyphae and by the more abundant protoplasmic contents. ^c'^f^ '¥$0' 3h1 ;yz. ^-^ Fig. 322. — Polyporus ig^iiarhis Fr. Transverse section of the under surface, h, the plexus of hypha; forming the walls be- tween the pores ; s, the hymenium ( x 270). (After Luerssen.) 394 FUXGT I'he trama is that portion of the projection which bears the subhyme- nial layer, and consists of hyphae running parallel to the surface from the insertion of the projection to its margin, which in many cases is un- covered by the hymenium. The hymenium itself consists of parallel rows of club-shaped basids surmounted by sterigmata and basidiospores. The basids are the termi- nations of the subhymenial hyph?e, but the latter also frequently end in sterile cells, which are termed paraphyses^ from the fact that they stand in the same relation to the basids as the paraphyses do to asci. Large inflated cells, often of relatively great dimensions, called cystids, Fig. 323. — Polyporiis igniarius Fr. Upper surface (half natural size). (After Luerssen.) are frequently found emerging from the hymenial surface (fig. 321). They are very variable in form, club shaped, flask-shaped, cylindrical ; pointed, hooked, or knob-shaped at the tip. They may be regarded as merely prominent hymenial hairs with the probable function of protecting the basids, or of parting the appressed lamellce. They have been the subject of much idle speculation, and among other erroneous views they have been regarded as male organs. In the sporophores of many Agaricini, notably of Lactarius (Fr.), laticiferous hyphce occur, which yield considerable quantities of milky, generally acrid, juice when the tissue is bruised. BA S IDIOM YCE TES 395 Sub-class 2. — Gasteromycetes. The Gasteromycetes very closely resemble the Hymenomycetes in the essential points of the structure of the basids. At all events the agreement is close in this respect between the higher Hymenomycetes with cap and stalk, and the Hymenogastrese, a section of the Gastero- mycetes ; while other subordinate sections, such as the Lycoperdaceae and Phalloideae, diverge from the Hymenogastreae only in minor points, as, it was seen, the lower Hymenomycetes do from the higher forms. The possession of a trama with a hymenial layer on either side of it may be here noted. In the external conformation, however, of the members of the group, a great variety is displayed, and, but for the existence of numerous intermediate forms, the group would appear to lack coherence in this respect, so great is the range of variation. The mycele is very frequently in the form of root-like strands, though there is no constancy in this respect, and the simple filamentous mycele occurs abundantly. The compound sporophores frequently grow to a great size in some of the sections, but the character which unites the whole is the possession of an invest- ing membrane, \.\\q peridiii??i, within which, and springing from it, are plates of tissue dividing the interior into chambers where the hymenium is produced. At the outset there may be noted the remarkable genus Gautieria (Vitt.), which has no peridium. The peripheral chambers are therefore exposed on the free surface. The peridia of other forms vary consider- ably in thickness and other characters, and a tendency exists towards excessive thickening in the basal region, which develops outwards, forming a stalk in some instances, e.g. Lycoperdon (Tourn.) ; or inwards, in which case either a cushion-like body is produced, e.g. Hymeno- gaster (Vitt.), or a central column, e.g. Phalloidete. The whole cham- bered structure is termed the glebe. The HvMENOGASTRE.^ may be regarded as an assemblage of the simplest forms of Gasteromycetes, possessing usually the simple structure indicated, but including among its members Gautieria without aperidium, and Secotium (Kze.), a genus with a central column traversing the body of the fungus. These two forms but heighten the resemblance which it has been remarked exists between the Hymenogastreae and the Hymeno- FiG. 324. — A, Octaz'iana asterosperjna Vitt.. in sec- tion ( x 5). (From Luerssen after Tulasne.) 396 FUNGI mycetes, the one being an approach to gymnocarpous forms, and the other noteworthy in respect of its stalked and pileate appearance. I)e Bary, in comparing the groups, says (' Comp. Morph. and Biol,' p. 337) : 'If we could attribute a decisive value to the habit of the plants, we should dwell upon the great resemblance between the stalked Hymenogastrese, like Secotium erythrocephalum (TuL), and a veiled Boletus. . . . But among the Polyporese there is a remarkable form Polyporus volvatus (Pk.), the Polyporus obvallatus (Berk, and Cooke), which considered by itself must be placed with or close to the Hyme- nogastreae. Its sporophore, which lives in the bark of trees, is a hollow spherical body flattened at the poles and about the size of a hazel nut, with a thick closed wall of leathery texture ; its interior surface is Fig. 325. — Batarrea Steveni Fr., longitudinal sections, rt, a younger specimen, but with most of its spores ripe b, a mature specimen, of which only apex and base are shown, p and h, the outer, /, the inner peridium ; g, the glebe (one-third natural size). (After de Bary.) Fig. 326. — Batarrea Steveni Fr. Isolated threads of the capillitium ( X 390). (After de Bary.) covered with the hymenium of a Polyporus on the part next the sub- stratum, and is sterile on the opposite side.' In the Lycoperdace^ (Puff-balls) the peridia are often developed to a colossal size, and in structure they agree in the main with the Hyme- nogastreas. The chief distinction lies in the existence of two kinds of hyphae in the trama ; slender segmented hyphae with dense protoplasmic contents, the terminal members of which compose the hymenium, and stouter hyphae running not only in the trama, but crossing the chambers. Eventually the slender hyphas and the hymenium disappear, leaving only the stout hyphae, now called the capillitium^ and the masses of spores between. As examples of the possession of both inner and outer peridium in this section, there may be cited Geaster (Mich.), in which the outer one BA S IDIOM YCE TES 397 becomes recurved after splitting longitudinally and acquiring a stellate aspect, and Batarrea (Pers.), which possesses an axile column mimedi- ately beneath the middle of the inner peridium. It develops into a stout stalk, which raises the closed inner peridium on its summit and ruptures the outer one, which now resembles in appearance the velum universale of Hymenomycetes. In Scleroderma (Pers.) the development of the glebe is intermediate between Hymenogastreae and Lycoperdacece. While the trama is disorganised, and a portion persists as a fine network together with the masses of spores, it yet forms no true capillitium. The NiDULARiE.E, though very different in outward aspect from the ^''f C' Fig. 2>'^-j. — C7-iccilnihait rndgare Tul. A — C, longitudin=il section through ripening sporophores ; stages of deve- lopment in order of letters (slightly magnified). D, ripe sporophore in which the epiphragm is beginning to disappear (natural size). (After de Bary.) Fig. 2,'2^-—CrHcihilnm vulgare. Section through upper part of sporophore of about same age as B in Fig. 327 (more highly magnified), ap, the outer, ip, the inner peridium; r/" and af, its hairs; n, funiculus; /, the layer which forms a sheath round it, and belongs to a peridiolum divided through the middle. (After Sachs.) other sections, are yet readily comparable with them. The chambers of the glebe possess very stout walls, and ultimately become separated from each other. The wall of the peridium becomes transformed into a gelatinous substance over the apical region, and on its disappearance the chambers of the glebe (peridiola) are left exposed in the interior of the bowl-shaped lower portion of the wall. Free and detached they resemble comparatively large sporanges. In Crucibulum (Tul.) a thin white membrane termed the epiphragjn temporarily covers the summit (fig- 327)- The Phalloide^ are an assemblage of very remarkable and strange forms, in which the Basidiomycetes find their highest development. '398 FUNGI Great variety of external conformation exists within the group, as the student will at once recognise on viewing such members of it as Phallus (L.), ,Hymenophallus (Nees ab Esenb.), Clathrus (Mich.), Ileodictyon (Tul.), Aseroe (La Bill.), «S:c. Specimens of Phallus impudicus (L.) while yet enclosed within the peridium exhibit the following structure : The peridium consists of an outer white membrane and an inner white thinner one, and between these two a thick layer of tissue which has become gelatinous. Immediately within the inner membrane lies the glebe, situated in the upper capitate portion, and bounded on its inner surface by a conical membrane T^>y Fig. 329. — Muthtus caninus Fr. Young sporophore. in, mycele ; stages of development in order of letters 11 — y. y, a specimen with ripe spores, but before elonga- tion of stalk, a, the outer wall ; i, the inner ; g, gela- tinous layer of peridium ; b, the basal portion ; k, the cone ; s, the stalk ; gd, the glebe (natural size), (After de Bary.) Fig. 330. — A nearly mature specimen of Pkalhts impudicus L. before elonga- tion of stalk, in longitudinal section. m, mycele ; a, outer, 2, inner wall ; g, gelatinous laj'er ; st, stalk ; A, its cavity filled with mucilage ; t, lower margin of pileus ; sp, glebe ; «, the cup-shaped basal portion ; x, the spot where the peridium bursts (two- thirds natural size). (After Sachs.) belonging to the central axis. This membrane gives off outwards into the glebe numerous walls arranged honeycomb fashion and dividing the glebe into compartments. The structure of the glebe itself recalls that of the Hymenogastreae and Lycoperdaceae. Below the glebe, and surrounding the base of the central axis, is a cup-shaped mass of com- paratively firm tissue, in which the base of the stalk is fixed. It connects with the lower portion of the inner peridium, and sends a thin projection of tissue of less consistency upwards between the conical mem- brane and the stalk. The base rests on the outer layer of the peridium. The stalk itself is hollow at maturity, and is composed of air-containing BA SID 10 M YCE TES 399 tissue, with numerous compartments. To scatter the spores the stalk elongates enormously, while it increases in thickness at the same time ; the peridium bursts at the apex, and the glebe is separated from the inner peridial membrane and ele- vated on the summit of the stalk. When the spores are scattered, the conical membrane (so-called pileus) remains with the honey- comb-like structure on its outer surface attached to the apex of the spongy stalk. In Clathrus the development of peridium and glebe agrees with Phallus, but instead of a stalk a net-like structure serves to burst the peridium and elevate the glebe. Such forms as Mitremyces (Nees ab Esenb.), Tulostoma (Pers.), Polysaccum (DC), and Sphaerobolus (Tode) exhibit other and remarkable types of development. Though they do not properly fall under any of the sections dealt with, they may be regarded as more or less divergent from the Lycoperdaceae. Fig. 331. — Aseroe rubra Berk. Mature specimen. The peridium is attached below ; the glebe is in the middle of the radiating expansion (half natural size). (From de Bary, after Berkeley.) Literature. De Bary — Zur Kenntniss einiger Agaricinen (Bot. Zeit., 1859). Bonorden — Beobacht. u. d. Bau d. Agaricinen (Bot. Zeit., 1858). Bonorden — Mycologische Beobacht. (Phallus, Sphserobolus) {ibid., 1851). Bonorden — Die Gattungen Lycoperdon u. Bovista, kc. {ibid., 1857). Brefeld — Bot. Untersuch. li. Schimmelpilze, iii. (Leipzig, 1877). Brefeld— For further development of Brefeld's views on the classification, &:c. , of Basidiomycetes (with much research on the lower forms) see Unters. aus dem Gesammtgebiete der Mykologie, Heft vii., 1888. Corda— Icones Fungorum Prag (1837-1854). Eidam — Die Keimung der Sporen u. d. Entstehung d. Fruchtkorper bei d. Nidu- larieen (Cohn's Beitrage, ii.). Fischer — Zur Entwick. d. Gasteromyceten (Spharobolus, Mitremyces) (Bot. Zeit., 1884). Hartig— Wichtige Krankh. d. Waldbaume (Berlin, 1874). Hartig — Die Zersetzungserscheinungen d. Holzes d. Nadelholzbaume u. d. Eiche (Berlin, 1878). Hesse— Mikroskop. Unterscheidungsmerkmale d. typischen Lycoperdaceengenera (Pringsh. , Jahrb. x. ). Hesse— Keiinung d. Sporen von Cyathus striatus {ibid., x. ). 400 FUNGI Murray— On the outer peridium of Broomeia (Journ. Linn. Soc. Bot., xx., 1884). Murray — On two new species of Lentinus, one of them growing on a large sclero- tium (Trans. Linn. Soc, 1886). Nees V. Esenbeck —Plant, mycetoid., &c. , Evolutio (Nova Acta Acad. Leop.- Carol., xvi.). Pitra — Zur Kenntniss d. Sphaerobolus stellatus (Bot. Zeit., 1870). Rossmann — Beitr. zur Entwickl. d Phallus impudicus (Bot. Zeit., 1855), Sachs — Morph. d. Crucibulum vulgare Tul. (Bot. Zeit., 1855, p. 833). (Omitted from index to vol. of Bot. Zeit. ) Schlechtendal— Eine neue Phalloidee, nebst Bemerkungen u. d. ganze F'amilie (Linnaea, 1862). Schlechtendal u. Miiller — Mitremyces Junghuhnii (Bot. Zeit., 1844). Schmitz — Mycologische Beobachtungen, &c. (Linngea, 1842). Schinitz — Ueber Entw. , Bau u. Wachstum von Thelephora sericea u. hirsuta {ilnd., 1843)- ^ Schrriter — Ueber d. Entwickl. u. d. systematische Stellung von Tulostoma (Cohn's Beitrage, ii.). De Seynes— L'organisation des Champignons superieurs (Ann. Sc. Nat., ser. 5, i.), De Seynes — Rech. sur 1. vegetaux inferieurs, i. Des Plstulines (Paris, 1874). Sorokin — -Developpement du Scleroderma verrucosum (Ann. Sc. Nat., ser. 6, iii. ). Tulasne — Carpologia, i. (Paris, 1 861). Tulasne — Fungi Hypogaei (Paris, 185 1 ). Tulasne — Obs. sur l'organisation des Tremellinees (x\nn, Sc. Nat., ser. 3, xix.). Tulasne — Nouvelles notes sur les fungi Tremellini et leurs allies [ihid., ser. 5, xv.). Tulasne — De la fructification des Scleroderma comparee a celle des Lycoperdon et des Bovista [ibid., ser. 2, xvii.). Tulasne — Sur les genres Polysaccum et Geaster {ibid., ser. 2, xviii,). Tulasne — Rech. sur I'organ. d. Nidulariees {ibid., ser. 3, i.). Tulasne — Description d'une espece nouvelle du genre Secotium {ibid., ser. 3, iv.). Tulasne — See Explor. Sc, d'Algerie, p. 434 (Clathrus). Van Tieghem — Sur le developpement du fruit, &c. , des Basidiomycetes, &c. (BulL Soc. Bot. France, 1876). (See also Bot. Zeit., 1876.) Vittadini — Monographia Lycoperdineorum (Mem. Acad. Torino, v., 1842). Woronin — Exobasidium Vaccinii (Ber. d. Naturf. Gesellsch. Freiburg, 1867). Of historical interest is — Micheli— Nova Plant. Genera, 1729 (Phallus, Clath,nis). The student is also referred for both morphological and sj^stematic treatises to the numerous papers of Berkeley— to be found especially in the Ann. and Mag. of Nat. Hist. and. Hooker's Journal of Botany — and to his separate books; for systematic information particularly to the works of Fries, Persoon, Hoffmann (Icones Analyticx Fungorum, Giessen, 1861-65), Saccardo, Sylloge, vols. v. -vii. ; and for British forms to Cooke's Handbook of British Fungi, 1 871, and to Stevenson's Hymenomycetes Britannici, 1886. 40I SIXTH SUBDIVISIOX. MYCETOZOA. The Mycetozoa are a group of organisms separated by a great gulf from the Thallophytes, but presenting certain points of resemblance to the Fungi which may here be indicated, while the amount of that resem- blance and the degree of their divergence will be more fittingly esti-- mated at the end of this chapter. Their nutrition is saprophytic, and the organs of reproduction are sufficiently like those of the Fungi to justify the use of the terms sporange, spore^ swarm-spore. The vegetative body, on the other hand, differs in structure tofo ccelo from any form of thallus. It consists of a naked protoplasmic body, either a plasmode formed by the coalescence of peculiar swarm-spores, or an aggregation of such swarm-spores. The first case is characteristic of one class, the Myxo- mycetes ; the second case of the other smaller class, the Acrasiea^. Class XXIII. — Myxomycetes. The ripe spores of ^lyxomycetes are capable of germination at once, and many of them retain this power for considerable periods, some for as long as several years. Most germinate at the ordinary spring or summer temperature, and in pure water, while others require a nutrient solution. The germination of the spores of Cribrarieae and Tubulinae has not been observed, and the failure of the attempts to pro- cure it may be owing either to the supply of unsuitable media or to a necessity for a period of rest — more likely the former. In structure the spores resemble those of fungi, as has been said. The wall is either smooth or sculptured on the outer surface, and the protoplasm contains one, sometimes two, nuclei. The act of germination consists of the emission of a swarm-spore. The membrane opens and the proto- plasm escapes with a creeping motion. This naked protoplasmic bodv or swarm-spore then exhibits amoeboid movements, protruding and with- drawing irregular processes, becoming more or less elongated, and D D 402 MYCETOZOA Fig. 332. — Chondt-iodenna diffortne Rost. i, a ripe spore ; 2, the same germinating ; 3-5, swarm-spores ; 6, 7, the same in amoeboid state ; 8, two in close contact ; 9, the same coalesced ; 10, three in contact ; 11, two after coalescence, the third still free ; 12, ^-oung plasmode which has taken up two spores into its substance (x 350). (From Sachs, after Cienkowski.) acquiring a cilium at the end of a finely pointed process. Its movements are of two kinds : a hopping movement, during which it commonly rotates round its longi- tudinal axis, while the outline undulates ; and a creeping movement,, which takes place on a firm substratum with the cilium in advance. The creeping is also some- times accomplished by the protrusion and re- traction of pseudocodes. The same swarm- spore often moves both by hopping and by creeping alternately. After passing through this stage, during which swarm-spores mul- tiply by simple division into two (such division taking place in some cases even before leaving the spore), the formation of plasmodes begins. The swarm-spores taking part in this process are such as have withdrawn their ciha and exhibit creeping amcjeboid movements. Several come into con- tact and coalesce, thus forming the beginning of the plasmode. Others are drawn towards it — how, no one has ever found out — and successively coalesce with it, until a comparatively large plas- mode is formed with the appearance and move- ments of a huge amoeboid swarm-spore without cilia. This plasmode Fig. 333. — Didyjnium serpjda Fr. A and B, plasmodes (natural size). C, margin of a moving plasmode ( x about 200). (After Reinke.) MYXOMYCETES 403 nourishes itself and grows, acquiring, in the case of some Physarece, great dimensions, and forming reticulated masses which may be measured by inches. Fuligo varians (Somm.) (or as it is more commonly called .-Etha- lium septicum (Fr.)or 'flowers of tan,' from its appearing during summer on tan) is such a body, but the plasmodes of other families of Myxo- mycetes, as well as of some Physarese, generally remain very small in com- parison with this. The appearance of the strands or branches of the plas- mode (under the microscope) is that of a turbid granular mass bordered by a clearer hyaloplasm. The surface of the plasmode of Physareae is in- vested with a soft shiny envelope of a substance different from protoplasm. The plasmodes of certain other forms are similarly invested with en- velopes, as to the nature of which not much is known. The larger portion of the granules contained in the plasmodes of Physareae are of calcium carbonate ; granules contained in other plasmodes require investigation. Nuclei are abundantly present. Many foreign bodies such as spores, diatoms, (Sec, are often found included in plasmodes. Constant movement is maintained, and the most characteristic is that of the pro- trusion and retraction of pseudopodes. Since protrusion is commonly more active on one side than on the other, an advancing movement of the whole is thus brought about. Internal streamings, more or less copious, answer to the amceboid movements. The external causes of move- ments are : with reference to (i) illnmi7ia- tion, they are negatively heliotropic ; (2) watei' — they are positively hydrotropic, i.e., when not about to form spores they leave comparatively dry spots and move towards moist places ; (3)>^^— they are positively trophotropic, i.e., they move towards nutrient substances (as might be expected) ; (4) /z^^/— within certain limits they move towards the warmer side of a surface unequally warmed. These movements are without reference to the direction in space in which they may have to be made. It may be stated here that the process of nutrition takes place only in the amoeboid states — the swarm-cell and plasmode. Fig. 334. — Steinonitis /itsca Roth_. A, sporange (natural size). B, capillitium (X about 100). (After Reinke.) D D 2 404 MYCETOZOA Resting states may occur at all motile stages of the life-history. Micro- cysts are the resting states of swarm-spores. They round themselves off, and are invested with a delicate membrane or only with a firm border. Young plasmodes similarly form thicker- walled cysts, and mature plas- modes form multicellular bodies — sclerotes. The spores of Myxomycetes are formed either endogenously within sporanges, or on the free surface of sporophores (Ceratieae). Sporanges are formed either by the whole plasmode becoming one, or the plasmode divides into portions, each of which becomes a sporange. Such as are situated on stalks begin as small swellings on *a strand of the plasmode, and by degrees acquire their mature form as the protoplasm ascends into Fig. 335. — «, Cc7-atin]ii hydnoidcs Alb. and Sch. Piece of sporophore in act of forming. b, Ceratiunt Jtorioidcs Alb. and Sch. Piece of the margin of a sporophore ; spore- formation begmning; two spores which subsequently become slightly ellipsoid on their stalks, (a x about 68, b x 120.) (After Famintzin and Woronin.) them. AVhile this process of formation goes on the sohd contents of the plasmode are expelled. The interior of the mature sporange is either filled with spores only, or more commonly there is also present a capiHitiuju consisting of numerous filaments traversing the cavity in all directions. They probably serve as supports to the wall of the sporange in the first instance, and may further be connected with its rupture and the dispersal of the spores. There are only two known species of Ceratium (Link), a genus which forms free spores, i.e. not within a sporange. In this case the plasmode before spore-formation consists of a network of innumerable branches from which cylindrical processes arise. The whole protoplasm M \ 'XOJI YCE TES 405 flows into these processes and finally breaks up into numerous polyhedral portions. Each of these portions grows outward into the form of a ball connected with the surface by a short narrow stalk. This sphere acquires a wall, and the process of spore-formation is completed. Class XXIV.— Acrasiese. So far as is known the spores of Acrasiese germinate only in nutrient solutions. The swarm -spores are never ciliated, and move only by creeping in amcjeboid fashion. Under unfavourable conditions they encyst themselves, and form temporary resting states. They unite in great numbers for the purpose of forming spores again, but the union never amounts to coalescence into plasmodes. They are heaped together as it were, and compose bodies of more or less definite form. In this condition each swarm-spore becomes invested with a thin membrane, though no common sporangial wall is formed. Guttulina(Cienk.) forms simple spore-heaps, but in Dictyostelium (Bref.j and Acrasis (Van Tiegh.) a stalk is formed by the swarm-spores in the centre of the mass becoming transformed into series of cells with firm walls, and up it the rest of the swarm-spores climb and form spores at the top. Doubtful 2\Ivcetozoa. De Bary repudiates the attempt made by Zopf to bring together under this group an ill-assorted assemblage of lower organisms exhibit- ing amceboid movements. He considers such forms as Bursulla (Sorok.), Protomyxa (H?eck.), Vampyrella (Cienk.), Xuclearia (Cienk.), Monas amyli (Cienk.), Monadopsis (Klein), Pseudospora (Cienk.), Colpodella (Cienk.), and Plasmodiophora (Woron.) to be doubtful Mycetozoa. Plasmodiophora Brassicse (Woron.), which is parasitic on the roots of Crucifer^e, on which it produces large swellings, is common. The cihated swarm-spores penetrate into the parenchymatous tissue of such roots. The cells affected swell to a great size, and large amceboids appear in them, but it is not certain whether these are single swarm- spores or small plasmodes formed by the coalescence of several. The whole protoplasmic contents of a cell then break up into spores. Affinities. De Bary, to whose remarkable investigations we owe the bulk of our knowledge of the Mycetozoa, considers that the group differs 4o6 MYCETOZOA distinctly from the Fungi (and still more from other plants) ' in all such characteristics as do not belong to all organisms alike. . . . The differ- ence would not be less decided, if the Mycetozoa were without their re- markable amoeboid movements, for such movements are observed in other vegetable cells which have not a firm membrane. The character- istic mark of separation lies in the formation of plasmodes or aggrega- tion of swarm-cells ' (' Comp. Morph.,' p. 443). He farther remarks that the highest forms of the group give no evidence of close affinity with yet higher organisms, and seeks for their relationship with Amoeba. Guttulina, he points out, differs from such forms only by the aggregation of its spores. Guttulina protea (Fay.) (Copromyxa protea, Zopf) even forms solitary spores. This form then links the Amoebae with the more highly differentiated Acrasiese, and these connect with the Myxomycetes. Taking together this connection with the animal kingdom, and the want of connection on the other hand with Fungi (to which they have a merely superficial resemblance) or other plants, we are justified in placing them, as de Bary does, 'outside the limits of the vegetable kingdom.' Literature of Mycetozoa. Baianetzki — Influence de la lumiere sur les Plasmodia des Myxomycetes (Mem. Sc. Nat. Cherbourg, xix. , p. 321). De Bary — Die Mycetozoen (Zeitsch. f. wissensch. Zoologie, Bd. x., 1859; and 2nd edition, Leipzig, 1864). Brefeld — Dictyostelium mucoroides (Abh. d. Senckenberg. Naturf. Gesellsch., vii.). Brefeld— Untersuch. aus der Gesammtgebiete der Mykologie (Leipzig, 1884). Cienkowski — Zur Entwickelungsgesch. d.Myxomyceten(Pringsh. Jahrb. wiss. Bot., iii.). Cienkowski — Das Plasmodium {ibid.^\\\.\ Cienkowski — Ueber einige protoplasmatische Organismen (Guttulina). See Just's Jahresber. for 1873, p. 61. Cienkowski — Beitr. zur Kennt. der Monaden (Schultze's Arch. f. micros. Anal., i.). Lister — Plasmode of Badhamia and Brefeldia (Ann. of Bot., ii., 1888, p. i). Rostafinski — Versuch eines Systems der Mycetozoen (Dissertat. Strassburg, 1873). Rostafinski — Slucowce (Mycetozoa) (Paris, 1875). A monograph admirably illustrated, but written in Polish. The system in Cooke's Myxomycetes of Great Britain (London, 1877) is adapted from Rostafinski's monograph. Stahl — Zur Biologie der Myxomyceten (Bot. Zeit., 1884). Strasburger — Wirkungd. Lichtesund d. Warmeauf Schwarmsporen(Jena, 1878, p. 69). Strasburger — Zur Entwickgesch. d. Sporangien v. Trichia fallax (Bot. Zeit., 1884). Van Tieghem — Sur quelques Myxomycetes a plasmode agrege (Bull. Soc. Bot. de France, 1880, p. 317;. Zopf — Die Schleimpilze, in Schenk's Handbuch der Botanik, iii. (1887). For further literature see De Bary's Comp. Morph., p. 453, and Rostafinski's monograph. 407 SEVENTH SUBDIVISION. PROTOPHYTA. "Whether the Protophyta should be reckoned as a distinct subdivision from the Algae, or only as the lowest members of that great series, is a question rather of convenience than of principle. In an ideal system of classification founded exclusively on genetic affinities, those organisms would be regarded as ' protophytes ' which were the earliest heralds of the appearance of vegetable life on the surface of the globe. But, from the structure and conditions of life of such organisms, it is impossible that they can have been preserved to us in the fossil state, and it is only from the comparative simplicity or complexity in the structure of an organism that we can conjecture whether it is an archaic or a derivative form. And here, as was remarked in the Introduction, we are extremely liable to be misled if we neglect to take into account the phenomenon of the constant appearance of degeneration or retrogression in the vegetable kingdom. An organism may be simple in its structure either because it has never risen, through countless ages, above the simplicity of its primeval ances- tors, or because it has fallen back from a more complicated condition. The object of the scientific systematist should be to separate, so far as possible, between these two sets of organisms, to include the former among his lowest class of protophytes, and to relegate the latter in each case to the class from which they have degenerated. But this task is attended with great difficulties, and is often well-nigh impossible. An organism may display degeneration of one set of organs, while another set manifest no such degeneration and have even continued to develop. We may take it indeed as a general law that wherever you have either the vegetative or the reproductive organs strongly developed, while the other set are very feeble or altogether wanting, you have prima fade evidence of retrogression. But, on the other hand, degeneration may take effect in all the organs of a plant, leading to retrogression in all lines towards, it may be, the archaic form. As knowledge advances, the constant tendency will be to transfer to this class of retrogressive members of higher families forms previously regarded as protophytal. 4o8 PROTOPHYTA While the Schizophyceae or chlorophyllous Protophyta approach very closely to the lowest forms of Algge, the Schizoniycetes or non-chloro- phyllous Protophyta exhibit greater affinities, as de Bary has shown, with the chlorophyllous forms than with any family of Fungi. Grouping, therefore, all these lowest forms of vegetable life, whether containing chlorophyll or not, into a single subdivision of Cryptogams, it will be most convenient to discuss them under two heads, as distinct and to a certain extent parallel series. (;roup L— SCHIZOPHYCE.^. An attempt is here made to bring together those chlorophyllous forms which, in the present state of our knowledge, we must regard as primordial ; while others, almost equally simple in structure, have been referred to the classes of which they appear to be retrogressive members. The group now under consideration comprises the greater number of the forms of vegetable life which are unicellular, which display no true pro- cess of sexual reproduction, and which contain chlorophyll. Limited in this sense, the Schizophycese may be divided into three well-marked classes, the Protococcoidece, the Diatomacece^ and the Cyano- phycece. In the Cyanophyceae are included those forms in which the pure green colour of the chlorophyll is masked by a blue-green pigment dissolved in the cell-sap, an arrangement not found except in plants of the very simplest structure. The position of the Diatoms has been a subject of much controversy among systematists. They display in some respects a similarity to the Desmids ; but, for reasons given below, we are disposed to consider this resemblance as apparent rather than real, and to regard the Diatomaceae, not as a family derived from the Desmidiaceae by retrogression, but as a primordial type of great simplicity of structure. In the Protococcoideae are included those forms in which the pure-green of the chlorophyll is not concealed by the blue-green colouring matter of the Cyanophyceae, nor by the brown colouring matter of the Diatoms. It is unquestionably from them that all the higher forms of vegetable life have been derived, and the boundary line between the Protococcoideae and the lower forms of Algae is one that cannot be accurately laid down. Literature. The literature of the Schizophyceae is included under that of AIg?e, or in the works specially named when treating of the separate classes and orders. PROTOCOCCOIDE^E 409 Class XXV. — Protococcoideae. In this class, the Chlorophyll ophyceae of some writers, are included those simplest forms of vegetable life in which the endochrome consists of pure chlorophyll of its natural green colour, sometimes replaced, to a larger or smaller extent, by a red pigment, but the cell-sap never pervaded, as in the Cyanophycese, by a soluble blue colouring-matter. The individuals are of microscopic size, and may be either motile or resting, and very commonly the same species occurs in both conditions. The motile ox protococcus form is, in the lower members, strictly unicel- lular, consisting of chlorophyllous protoplasm either naked or invested with a very delicate coat of cellulose or of a carbohydrate nearly allied to cellulose, usually developing but little or no mucilage, and moving freely through the water by means of a pulsating vacuole and two vibra- tile cilia. In the resting condition the individuals are invested by a much thicker cell-wall, and have a tendency to congregate or coalesce into /rt;/;;/^//*?/^ families, and to enclose themselves in a common gela- tinous envelope. In this state they multiply rapidly by repeated bipar- tition. The palmelloid form ma}' be derived directly from the proto- coccoid, the protococcus-cells coming to rest, losing their cilia, and investing themselves with a thicker cell- wall of cellulose ; or, in the higher members, the individual consists- of a number of gotiids, chloro- phyllous masses of protoplasm, enclosed in a common watery hyaline envelope of mucilage, and propagation takes place by the escape of these gonids from the envelope in the form of naked biciliated zoospores or swarm-spores, closely resembling protococcus-cells, which, after going through a motile period, come to rest, lose their cilia, invest themselves with a coat of cellulose, and multiply by repeated bipartition in the palmelloid form. In some cases these swarrn-spores are of two kinds, the smaller ones being conjugating zoogametes. In no case is the individual filiform and divided by transverse septa, as in the higher families of the Cyanophycese. It cannot be too strongly insisted on that this class is a purely pro- visional one. Many of the forms at present included in it are, in all probability, nothing but stages in the development of alg;« of consider- ably greater complexity of structure belonging to widely separated families. The external resemblance between the Protococcaceae and the Chroococcacese, and the parallel series of forms in these two families, does not probably represent any genetic affinity. There is, on the other hand, an undoubted alliance with the Pandorineae, through Chlamy- dococcus and Chlamydomonas, as well as with the Hydrodictye^e and 4IO PROTOPHYTA Siphoneae through intermediate forms. The Protococcaceae converge also on the boundary hne between the vegetable and animal kingdoms ; and, since it has been demonstrated that the power of forming chloro- phyll and starch is not of itself sufficient to determine an organism to belong to the vegetable kingdom, it is impossible to draw a hard and fast line between the Protococcaceae and the Flagellate Infusoria, with which they are connected by such forms as P^uglena and the Peridinicce. The Protococcoideas are divided into two orders, the boundaries of which are very ill-defined : the Erenwbite and the Protococcacece. Literature. Ehrenberg — Die Infusionsthierchen, 1838. Nageli — Neuern Algensysteme, 1847, pp. 123-132 ; and Gattungen einzelliger Algen, 1849. Braun — Verjiingung in der Xatur, 1 85 1 (Ray Soc. Bot. and Phys. Memoirs, 1853) ; and x\lgarum unicellularum genera, 1855. (Also the Memoirs referred to under the separate genera, and the literature ot AlgK generally. ) Order i.— EREMOBi.t (including Sciadiace.'E). In this ill-defined family, known by some writers as Characiacea^, the limits of which are very difficult to assign, are included a number of genera distinguished from the Protococcaceae by their greater complexity of structure. They are mostly fresh-water, but comprise also a few marine organisms, free-swimming or attached to algae. In the larger number of genera each individual consists of a number of green proto- plasmic bodies, pseudocysts or gonids — that is, masses of chlorophyllous protoplasm of defined outline but not clothed with a definite cell-wall of cellulose — sometimes of considerable size, enclosed in a common trans- parent hyaline envelope, which may be simple or may branch in an arborescent manner. In some genera the hyaline envelope is wanting. MultipHcation takes place by simple division, or by the transformation of the gonids into zoospores, which sometimes display a differentiation into larger uiegazoospores ^axd. sniciUer micro zoospores or zoogametes. Although conjugation of these gametes has hitherto been observed only in a few cases, this appears to be the earliest indication among chlorophyllous organisms of a differentiation of sexual elements ; and the Eremobiae clearly approach those algae which multiply by conjugation through Botrvdium, or through such forms as Endosphaera, Chlorochytrium, and Phyllobium, or again through Hydrodictyon. Lagerheim (Ber. Deutsch. Bot. Ges., 1884, p. 302) asserts the presence of chromatophores in Glaucocystis (Itz.). PRO TOCOCCOIDE.E 411 In the following paragraphs only the more remarkable or better known genera are described. In Sciadiuni A. Br., made by some writers the type of a distinct family Sciadiace/E, the peculiar mode of germination of the zoospores gives rise to a remarkably complicated structure. Each individual consists at first of a single elongated cylindrical cell. The green protoplasmic contents of this cell break up ultimately into a number of biciliated zoospores, which are set free by the upper })ortion of the cell -wall be- coming detached in the form of a cap. The zoospores do not, however, escape, but 2:erminate while still attached to the mother-cell, giving rise to a cluster of smaller cylindrical cells springing from the apex of the mother-cell. This may go on until the colony consists of as many as four generations, giving the appearance of a minute branching shrub. The zoospores of each genera- tion are smaller than those of the pre- ceding one, and it is probable that those of the last generation, which escape altogether from the parent-cell, are conjugating zoogametes. It is pos- sible that a form aUied to Sciadium may have been the starting-point of the Siphonocladaceae, with which family it shows a certain affinity, as, for example, with Valonia. Chlorothecium Bzi. (Malpighia, 1888, p. 250) occurs in the form of palmelloid colonies with a thick and firm cell-wall on aquatic plants. From the cells of these colonies are developed zoosporanges, or rather gametange:^ without any alteration of their primitive form ; from each gametange there escape from two to four swarm-spores, or occasionally only one, each provided with a single cilium and a conspicuous red pigment-spot. These swarm-spores are zoogametes, conjugating by gradual fusion. After hibernating the contents of the zygosperm break up into two masses, each of which escapes as a non-sexual zoospore^ so that the zygosperm is itself a zoosporange. From these zoospores are again formed the palmelloid colonies, in which form Chlorothecium may multiply itself non-sexually without producing zoogametes. The position of HalospJuBra (Schmitz, ]\Iittheil. Zool. Stat. Neapel, 187S, p. 61) is very doubtful. Each individual is a minute green globe, just visible to the naked eye, as much as 0*5 mm. in diameter, floating on the surface of the sea, and bearing an external resemblance to Volvox. Fig. 536. — SciadiHiii arbnscula A. Br. (magnified). 412 PROTOPHYTA -y,:-^ 5 r^:,-^' ^(B^§) ^'' '^ -^■; -■- @.; Each cell contains a nucleus and a vacuole ; the green protoplasmic contents break up ultimately into zoospores of a very peculiar form, conical, with two cilia attached to the nearly flat base, recalling those of Hydrurus (p. 256). In Didyosphceriiun Nag., which ought possibly to be placed under the Coenobieae, the free-swimming colony is com- posed of globular or kidney- shaped green gonids connected together by delicate threads of mucilage. New colonies are formed by repeated biparti- tion of the gonids, which fre- quently exist for a time without any enclosing cell-wall. Mis- chococcus Nag. consists of minute globular gonids connected together in an arborescent manner and enclosed in a hyaline envelope, the whole colony attached to fresh-water algae. Borzi (Malpighia, 1888, p. 133) describes also a palmelloid form of Mischococcus, the cells of which give birth to megazoospores with only a single cilium. The dendroidal form may spring either from these zoospores or directly from the palmella- cells ; its cells also produce uniciliated swarm-spores, similar to the zoospores but smaller. They are apparently zoogametes conjuga- ■^ Fig. 337. — HaplosphiEra ■viridix Schm. Globe ( x So), and zoospore (x 150). (After Schmitz.) Fig. 338. — Dictyosp]ia:rium 7-cniforine Buln. (x 400). (After Cooke.) Fig. 339. — Mischococcics conferzncola Nag. (x 400). (After Cooke.) ting to produce a biciliated zoosperm. Botrydina Breb., found on moist ground, trunks of trees, cvic., is composed of a number of minute gonids enclosed in a pear-shaped or globular hyaline envelope, as much as o-i mm. in diameter, and resembling Aphanocapsa among the Chroococcaceae. It may possibly be allied to Botrydium. Characium A. Br. is a minute green organism attached by a gela- tinous stalk to alg;£ or other fresh-water plants, often in groups. It is. PROTOCOCCOIDEzE 413 ovate or pear-shaped. 0-02-0 025 mm. in diameter in the larger species, often apiculate or spinous at the apex. The cell-contents divide, by successive biparcitions. into zoospores, which commence swarming while still within the mother-cell, indicating an approach to Hydrodictyon. They escape through a lateral or terminal fissure. Nearly allied to Characium are Hydrocytium A. Br., also met with in fresh water, and Hxdriamim Rabh., found in similar localities. In the last genus the zoospores also escape at the apex. In Apiocystis Xag. a large number of gonids are sparsely scattered through a stalked pear-shaped gelatinous envelope attached to fresh-water algge. They, occur chiefly in the periphery, and are ulti- mately converted into zoospores. Codiolum A. Br. is a club-shaped marine organism, about 0*04 mm. in diameter, and four to six times the length, attached to rocks or sea- weeds. It is propagated by zoospores, or, according to some observers, also by resting hypnospores. Haiickia Bzi. (Xuov. Giorn. Bot. Ital., Fig. 340. — Characium ornitJwcephahiJii A. Br. (x 600). (After A. Braun.) '^ - Fig. 341. — Apiocystis Brartniana Nag. ( X 100). (From nature.) Fig. 342. — Codiolum grcgariiim K. Br. (magnified). (After Hauck.) 1880, p. 290) grows on rocks exposed to the sea. The gonids are placed in pairs on a long hyaline stalk ; it produces zoospores of two different sizes, but no process of conjugation has at present been observed. 414 PROTOPHYTA Sykidio?i\sx\^X (Trans. Irish Acad., 1881, p. 27) is also a marine genus, allied to Characium and Hydrocytium ; but the zoospores escape through a terminal instead of a lateral fissure. Of free-swimming forms occurring in fresh water, Nephrocytiuni Nag. consists of kidney-shaped gonids enclosed in a hyaline envelope. Although the production of zoospores has not been detected in this genus, its position is probably here, though its true place may possibly be among the Sorastre?e. Dangeard (Bull. Soc. Linn. Normandie, i., 1888, p. 196) has. observed a mode of propagation by the formation of daughter-colonies within the membrane of the parent-colony. In Ophiocytium Nag., the origi- nally cylindrical individual becomes curved in a serpentine manner, and produced at one extremity into a hyaline spine. The zoospores escape by the detachment of the cap-like apex of the hyaline envelope. In Hormospora Breb. the free-swimming individual or colony con- sists of a very elongated straight or bent cylinder, sometimes branching, the gonids arranged in a single or double row within a dense hyaline envelope. No formation of zoospores has been observed. Cylindro- capsa (Reinsch) (see p. 227) is placed here by some authorities. Fig, 43. — Nephrocytuaii Ndgelii Griin. ( x 300). (After Cooke.) Fig. 344. — Hormospora viutabilis Br6b. ( x 200). (From nature.) Although in the majority of the genera named above only one kind of swarm-spore has hitherto been observed, it is highly probable that some or all of them produce both megazoospores and zoogametes with a sexual function. Literature. Fresenius — Abhandl. Senckenberg. Naturf. Gesell., iii., 1856-8, p. 237. Archer — Microscop. Journ., 1866. Zukal — Oesterr. Bot. Zeitschr., 1880, p. 11. Hohties — Journ. Linn. Soc, xviii., 1881, p. 132. Borzi — Nuov. Giorn. Bot. Ital., 1882, p. 272; and Studi Algologici, 1883. Lagerheim — Bot. Centralbl., xii., 1882, p. 33 ; and Oefv. Vetensk. Akad. Forhandl., Stockholm, 1885, p. 21. Klebs — Unters. Bot. Inst. Tubingen, i., 1883, p. 233. Bennett — Journ. Micr. Soc, 1887, p. 9; and 1888, p. 2. PRO rOCOCCOIDE.-E 41 Order 2.— PROxococcACE.^i (including Palmellace.^^:). In this family are included a number of organisms of very simple structure, many of which occur both in the free-swimming {protococcus) and in the resting {pabneUa) condition. In the former state they bear a very .close resemblance to the zoospores of the higher alga^. Other forms are known in one condition only, in which they have a free- swimming motion without the aid of cilia. Frotococcus Ag. is one of the commonest objects in fresh water, especially stagnant rain-water, forming masses of a bright green colour, either floating free or attached to a submerged or floating object, but destitute in this state of any spontaneous power of motion. In this, palmella-condition each individual consists of a nearly spherical cell, varying between forty and fifty microns (= "04- -05 mm.j in diameter, which multiphes rapidly by repeated bipartition of its contents. The bright green endochrome has usually intermixed with it a larger or smaller quantity of a red pigment, the propor- tion varying according to the conditions -545. — Protococcus pluz'ialis Ktz. A, motile condition ; B, palmella condi- tion ( X 250). (After Cohn.) of life, &c. The change to the active condition takes place in the following way. The protoplasm withdraws itself from the cell- wall, and escapes in the form of an ovoid mass provided with two very long and slender vibratile cilia and a pulsating vacuole, by the agency of which it is driven rapidly through the water. The pulsation of this vacuole has been explained by the alternate absorption from the water, through the agency of the chloro- phyll, of carbon dioxide, and the expulsion of free oxygen resulting from the process of assimilation. In some cases the contents of the mother- cell do not escape as a single zoospore, but break up before escaping into eight or more smaller zoospores. The motile protococcus may be either entirely without cell-wall of cellulose, or may have a very dehcate one, through orifices in which the protoplasmic cilia pro- trude. Some observers state that there are two kinds of zoospore in Protococcus — microzoospores and megazoospores, and that conjuga- tion takes place between the latter ; but this last statement at all events requires confirmation. After swimming about rapidly for a time in all directions with an apparently spontaneous movement, the motile protococcus comes to rest, loses its ciha, becomes encysted, or in- vested with a thick cell-wall of cellulose, and again enters the palmella- 4i6 PROrOPHYTA condition in the form of resting-spores, which may become dried up and retain their vitahty for years as a dry powder, resuming their activity when again placed in water. McNab (Ann. tv: Mag. Nat. Hist., 1883, p. 124) has, by the use of osmic acid and carmine, detected a nucleus in the free ciliated state of Protococcus, and also in individuals in which cell- division is going on. When in an active condition in sunlight, Protococcus gives off into the surrounding water large quantities of oxygen, the result of the activity of its chlorophyll, thus contributing to render it habitable for animal life. The amount of the red pigment varies greatly. It is often con- fined to a small spot near to the point of attachment of the cilia, the 'pigment-spot,' bearing a close resemblance to the 'eye-spot' of the Flagellate Infusoria. If present in larger quantities, so as to give a red tint to the entire organism, this is known as Hoematococcus (Ag.). In the palmella-condition this form frequently presents the structure and appearance of a blood-red incrustation on rocks and stones, when it has been described as Palmella cruenta (Ag.) and Porphyridium cruentum (Nag.). Very closely allied are the Palmella prodigiosa (Mont.) (Monas prodigiosa, Ehrb.), which forms blood-red spots on bread, potatoes, &c., and the Palmella nivalis (Hook.) (Protococcus nivalis, Ag., Chlamydo- coccus nivahs, A. Br.), which, under the name of 'red snow,' frequently covers large tracts of snow in arctic and alpine regions in a very short time. Phipson (Compt. Rend., Ixxxix., 1879, pp 316, 1078) has examined the red colouring-matter of Palmella cruenta, and finds it to consist of minute globules about four microns ('004 mm.) in diameter, closely resembling those of the haemaglobin of blood, but somewhat smaller. He proposes for the pigment the name pabnellin. It is soluble in water, but insoluble in alcohol, ether, and carbon bisulphide. Like hsemaglobin it contains traces of iron. Other lowly-organised snow and ice plants besides Palmella nivalis are brightly coloured, and appear to perform an important function in melting the snow by their strong absorption of the rays of heat. In addition to palmellin, Palmella contains also xanthophyll, and a small quantity of another substance of the nature of camphor and possessing a marshy odour, which Phipson calls characin, and which is present in other terrestrial and fresh-water algae, and espiecially in Chara. In the haematococcus-condition it is sometimes impossible to detect directly the presence of chlorophyll ; but experiments by Engelmann (Rev. Internat. Sci. Biol, 1882, p. 468, and Bot. Zeit., 1882, p. 663) seem to show that there is always a certain amount of chlorophyll present, though it is possible that the power which Hsematococcus undoubtedly has of decomposing carbon dioxide may be due to the presence of other substances allied to chlorophyll, but differing from it in colour. PROTOCOCCOIDE^ 417 It is impossible to distinguish between the genera Protococcus (Ag.), Pleurococcus (Meneg. ), and Pahiiella (Lyngb.) ; but it is doubtful whether Chlamydococcus (A. Br.) and Chlamydomonas (Ehrb.), which undergo much more compHcated changes of form, and in some condi- tions very closely resemble Protococcus, have been rightly identified with it (see p. 299). Hsematococcus Butschlii (Blockmann, Ber. Heidelberg Naturh. Ver., 1886) probably belongs to Chlamydomonas. Schnetzler s |t 5 FiG- 346. — Glockiococcns angliciis Benn. ( X 200). (From nature.) B Fig. 2A7 •~ Chlorococcuvt gigas Grvin. {x. 300). (After Cooke.) (Bull. Soc. Vaud. Sc. Nat., 1882, p. 115) regards Palmella uvc^formis (Ktz.) as a stage in the development of a Stigeoclonium ; while Ander- sson identifies it with Draparnaldia. Glochiococcus (Lagerh.) (Acanthococcus, Reinsch, Ber. Deutsch. Bot. Ges., 1886, p. 237) differs from Palmella in the cell-wall, which is thick and lamellated, being in most of the species furnished with wart.s, spines, or other prominences. The cells, which closely resemble the zygosperms of desmids, divide into eight or sixteen daughter-cells, which remain but a short time in connection, being set free by the deliques- cence of the outer membrane. Chlorococciim (Fr.) is analogous to Chroococcus among the Chroo- coccacese. Several species are common in pools or on moist walls or rocks. In C. gigas (Griin.) the cells are as much as CO 1-0*015 '^^^' in diameter, and either a single cell or a colony of cells is enclosed in a very thick lamel- lated hyaline envelope. In G/ceocysfis (Nig.), corre- sponding to Gloeocapsa among the Cyanophyceae, the cells are associated in families of two, four, or eight, each family being enclosed in a lamellated gela- tinous envelope, in addition to the similar envelope which encloses each cell. In Schizochlamys (A. Br.) the cells escape from the surrounding envelope by the latter splitting into two or four equal parts. EremosphcEra (de By.) is a beautiful bright green globe, o- 1-0-15 ^im. in diameter, floating free in bog-pools, and enclosed in a thin hyaline envelope. E E Fig. 348. — Schizochlafuys gelatinosa A. Br. ( x 600). 4i8 PROTOPHVTA Fig. 349. — Botryo- coccus Braunii Ktz. ( X 400). Fig. 350. — Urococc7is hisigtiis Hass. ( x 400). (From nature.) Botryococcus Ktz. consists of mulberry-like masses of thick-walled cells united together into colonies, with no investing membrane, or only a very slight one ; it is found in bog-pools, and is endowed with a rotating as well as a free-swimming motion. It has possibly a genetic affinity with the Coenobiese. In Urococais Hass. the endo- chrome is bright red, and the cell- walls throw off successive layers of mucilage, which form together a cylindrical or fusiform stalk, com- posed, in some species, of a large number of distinct annular segments. Tetraspora Lk. is composed of cells associated together in large numbers in a single layer imbedded in a copious gelatinous envelope. It has no spontaneous motion, and is possibly allied to Merismopedia, and also appears to have affinities with the Ulvaceae. Gay (Bull. Soc. Bot. France, 1886, Sess. Extraord , p. 41) records in T. gelatinosa (Desv.) the formation of biciliated zoospores, one being produced from the contents of each cell, and afterwards becoming encysted into a resting-spore. In Palmodictyon Ktz. the gelatinous envelope is filiform and branched, and cell-division takes place chiefly in two directions only. The position of the following genera is very uncertain. Very little is known of their mode of reproduction, and they lack the copious gelatinous envelope which is characteristic of the family gene- rally. They are mostly but feebly endowed with spontaneous move- ments, and may probably be a resting condition of algae or protophytes classed under entirely different groups. Raphidiu7n Ktz. includes several species very common in fresh water, and consisting of very narrow fusiform acuminate cells, usually curved, solitary or joined together in bundles, the cells being in the latter case united by their middle. Cell-division takes place in one direction onlv. Under the class Palmellaceae are usuallv placed also the genera Scenedesmiis Mey. and Polyedrium Nag., but their rank as independent organisms is exceedingly doubtful. Their probable position has already been discussed under the heads of the Sorastreae and the Pediastreae respectively (see pp. 303 and 299). Fig. 351. — Raphi- dium falcatuin Ktz. ( X 800). (From nature.) Fig. 352. — Scene- desmiis obtus7(s Mey. (x 400). (From nature.) FROTOCOCCOWE.-E 419 Reinsch unites Polyedrium with three other genera to make up a sepa- rate family, Polyedriace^, belonging to Palmellaceae. Richter connects Gloeocystis with the Chroococcaceae, and hence genetically with higher forms of algae. Cienkowski regards Pleuro- coccus, Gloeocystis, and probably other genera of Protococcaceae, as resting conditions of Chlamydomonas, or of similar organisms classed among the Coenobicce which multiply by conjugation. Under suitable conditions he states that they can all be made to produce biciliated zoospores with two contracting vacuoles and a nucleus. The part taken by some Protococcaceae in the development of lichens has already been discussed on p. 318. Literature. Cohn— (Protococcus) Nov. Act. Akad. Cks. Leop.- Carol., xxii,, 1850, p. 605 (see Ray Soc, Bot. and Phys. Mem., 1853, P- S'^S)- Cienkowski — Bot. Zeit., 1865, p. 21. Rostafinski — (Haematococcus) Mem. Soc. Sc. Nat. Cherbourg, 1 87 5, p. 142. Lagerheim — Oefv. Svensk. Vetensk. Akad. Forh., Stockholm, 1882, p. 47 ; and 1883, p. 37 (Bot. Centralbl., xii., 1882, p. t^t,). Richter— Hedwigia, 1 880, pp. 154, 169, 191 ; 1884, p. 65 ; and 1886, p. 249. Dangeard — (Chlamydococcus) Ann. Sc. Nat., vii., 1888, p. 105. Reinsch —(Polyedrium) Notarisia, 1888, p. 493. Class XXVI.—Diatomaceae. The family of Diatoms — called by the older writers Bacillariaceae — • includes a very large number of genera and species, all microscopic, some of them extremely abundant in running, stagnant (but not putrid), and salt water. The individuals are strictly unicellular, and are either free-swimming and isolated, or attached to one another in a linear series or in zigzag chains, adhering to one another by means of small annular cushions, or fixed to some solid object by a simple or compound gelatinous stalk. They are, with very few exceptions, characterised by the presence in the cell-wall of a deposit of silica, by which it becomes converted into a hard but thin and perfectly transparent shell ; and this is always invested in a thin gelatinous envelope. Some species are closely adherent to submerged plants by the whole of one side ; in other cases whole colonies are enclosed in a common gelatinous en- velope, which assumes the form of a simple or compound tube, flattened plate, or globular mass. This is especially the case with the marine species. Each individual ox frustule consists of two more or less symmetrical EE 2 420 PROTOPHYTA halves known as valves ; the siHcified cell-wall of the older of these halves is slightly the larger of the two, fitting on to the younger one like the lid of a cardboard box. The cell-wall is composed of an organic matrix closely allied in composition to cellulose, impregnated with silica or a compound of silica ; either of these two ingredients can be removed and the other left behind, the former by calcination, the latter by the action of hydrofluoric acid. In those species which are fixed by a gelatinous stalk, this stalk is also com- posed of a substance allied to cellu- lose. The overlapping edge of one of the two valves over the other is called the girdle or hoop ; this girdle may be simple, or there may be several. In many species — and probably in all, if examined with a sufficiently high power — each valve is marked with a number of rows of very fine perfora- tions, which, except under the very highest microscopic powers, appear as if confluent into striae or furrows. There may be two or three sets of these apparent strise, but they do not, as a rule, reach to the centre of the valve. So constant is the arrange- ment and the fineness of these stria- tions in some of the more abundant species, that they furnish an admirable test for the definition and angular aperture of microscopic lenses. Some species of Navicula (Bory) and Pleu- rosigma (Sm.) are especially used for this purpose. Some marine genera in particular (Triceratium, Ehrb., Coscinodiscus, Ehrb., &:c.) are cha- racterised by the beautiful honeycomb-like areolation of the cell-wall, due to the presence in it of actual chambers, which may or may not be covered by a thin membrane. The membrane at the bottom of these chambers is also most minutely perforated, constituting what is known as the secondary markitigs. In describing diatoms, the aspect in which the girdle is turned towards the observer is spoken of as i\\Q front, girdle. Fig. 353. — Pinnularia viridis Sm. A , valve-view ; B, girdle-view (diagrammatic). r, furrows ; 7n, raphe ; £, central node ; A', terminal nodules ; a, outer and older valve ; z, inner valve ; n, secondary lines ( X 800). (After Pfitzer.) DIATOMACE.^ 421 ^ a or 0^;?(7/ vieiv ; the aspect m which the surface of the valve is turned to- wards the observer is the si'^/e or va/ve viezv. In many diatoms the central space on the valve view not occupied by transverse striae shows at its middle and at each end a strongly refractive thickening known as a node or fiodule ; and these nodules are connected with one another by a longitudinal Ime or rib — the raphe or suture. The primary classification of the genera of di- atoms usually adopted depends on the presence or absence of this raphe. Each diatom-cell contains a nucleus and a nucleole. The chlorophyll occurs in the form of plates or bands arranged with more or less symmetry, and there are usually also drops of oil, especially when conjugation is about to take place. A very few di- atoms are green; but in the great majority of cases the colour of the chlorophyll is obscured by a characteristic brown pigment known as diato)nin^ readily soluble in alcohol, forming a brownish-yellow solution which is only slightly or not at all fluorescent. ^Vith concentrated sulphuric acid it assumes a beautiful blue-green colour. Petit (Brebissonia, 1879-80, p. 81) has very carefully in- vestigated the chemical and physical properties of the colouring matter of diatoms. Fig. 354 a.— .4«t Ehrb. s, valves, side \'iew, showing nucleus ; g„ g;„ girdle- views ; q, transverse section through middle of cell, showing silicified cell-wall, one half overlapping the other ; k, nucleus ; p, dense protoplasm ; ^ , g„, girdle surfaces (magnified). (After Pfitzer.) compound of chlorophyll and phycoxanthin, and as having a great analogy with the chlo- rophyll of the higher plants, the two spectra being very similar. Many of the solitary species of diatom, such as those belonging to 422 FROTOPHYTA the genus Navicula, possess the power of propcHing themselves through the water with considerable rapidity backwards and forwards in the direction of their longer axis, often with a jerking motion, or of creeping along the bottom on some submerged substance. The cause of this motion is a subject on which a large amount of attention has been be- stowed. Xiigeli attributed it to osmotic currents passing through the cell-wall. Ehrenberg believed that he had actually seen, in some cases, the extrusion through the raphe of vibratile cilia, in other cases of a ' foot ' or pseudopode ; but ^•/^ lf\ ^^^ observations have not been confirmed by others. The explanation of the mo- tion now generally accepted is that of Schultze — ^that it is due to the contractility of the protoplasm which is exuded outside the cell-wall. Mereschkowsky (Bot. Zeit., 1880, p. 529) states the arguments in support of the various views with regard to the causes of the mo- tion, and sums up in favour of the theory that it is the result of osmotic currents within the siliceous cell-wall. Hallier, again (Unters. liber Diatomeen, 1880), considers it due to a contractile layer of protoplasm, and asserts that at an early stage di- atoms have no true cell- wall of cellulose. Onderdonk (Microscope, 1885, p. 205) also attributes it to 'external cyclosis.' Diatoms have three modes of multiplication : — by simple division, by auxospores, and by a kind of conjugation which is regarded by some as sexual ; but the three modes pass gradually one into another. Simple division always commences with the bipartition of the nucleus. When it is about to commence the two valves separate from one another, the contents divide into two daughter-cells, and new siliceous valves are formed inside the old ones, and therefore necessarily smaller than they. The valves of the new individual are formed necessarily one after the other, the one formed later being smaller. The individuals produced in Fig. 355.— Stages in the formation of the auxospore of Friistulia saxonica Ag. s, valves ; in, gelatinous en- velope ; c, endochrome-plates ; a, auxospore (x 1,200). (After Pfitzer.) DIATOMACE.-E 423 this way constantly diminish in size, until the original size is restored by the formation of an auxospore, resulting from the concents leaving the siliceous valves, which fall away from one another, and increasing in size, either by simple growth or by the coalescence of two auxospores produced in the same mother-cell. In other cases two distinct auxo- spores appear to be produced from the contents of a single mother-cell. The auxospore finally becomes invested in a new siliceous cell-wall. In those cases in which the process has been most carefully followed out, the auxospore does not appear to owe its origin to any process of true sexual union. In some genera what is regarded by some as a true process of con- jugation has been observed, a zygosperm being produced as the result of the coalescence of the protoplasmic contents of two different individuals. The conjugating diatoms are here placed side by side enclosed in a common gela- tinous sheath ; the contents of each escape by the falling apart of the two valves, and unite into a single zygosperm. In other cases two zygosperms result from the con- jugation of a pair of cells. The protoplasm of each cell, as it escapes from its siliceous wall, puts out two protuberances ; these meet in pairs, and the whole contents of the pair of mother-cells finally pass into the two zygosperms, which complete their development in precisely the same way as the auxospores. Buffham states (Journ. Quek. Micr. Club, 1885, p. 131) that in the conjugation of Rhabdomena (Ktz.) the 'male' frustule is always smaller than the 'female' frustule, and that the union is effected by the 'male' frustules attaching them- selves in numbers to any part of the girdle of the 'female' frustule. De Bary and Pfitzer do not regard the fusion of the cell-contents of diatoms as in any sense a true process of sexual conjugation. De Bary (Bot. Zeit, 1858, Supplement, p. 61) thus summarises the four modes in which diatoms are reproduced by means of auxospores or zygosperms : — (i) Two products of conjugation are formed by the union of the contents of two distinct individuals; (2) a similar process results in the formation of a single product of the same nature ; (3) a single act of conjugation (production of auxospore) takes place between two portions of the contents of the same individual ; (4) two such acts of conjugation take place simultaneously between different portions of the contents of the same individual. In all cases the formation of a new in- dividual is completed by the simple division of the product of union Fig. 356. — Gouipho7iema constric- Uini Ehrb. attached by gelatinous stalks to a fresh-water alga (greatly magnified). 424 PROTOPHYTA (auxospore or zygosperm) into two symmetrical halves with or without the intervention of a period of rest. Still another mode of reproduction is described by Count Castracane and by some other observers, in Mastogloia (Thw.) and a few other genera, in the production of endogenous spores within the frustules. It will be seen that, notwithstanding the great abundance of diatoms, some important points in their life-history still remain unsettled. On the minuter details of the modes of reproduction, the spontaneous motion of diatoms and its causes, the structure of the sihceous cell-wall, and the chemical and physical properties of diatomin, the reader is referred to the very extensive literature of the subject ; only the most important memoirs are referred to below. The number of described species certainly exceeds 10,000 ; but this has been unduly increased by want of attention to the necessary variations in size in the same species. Not unfrequently diatoms form a gelatinous yellow scum on the surface of the water, or completely encrust submerged algae and other w^ater-plants ; they abound on the surface of \vet walls and rocks, and are not unfrequently present in the air. Some species are cosmopolitan ; the marine forms are especially remarkable for their size and beauty. Various deposits found on the surface of the globe, often of very considerable thickness, know^n as tripoli, ' Kieselguhr,' cSjc., consist almost entirely of the fossilised siliceous shells of diatoms, and they enter largely into the composition of a variety of earths used for manufacturing purposes. In some countries, such as China, Japan, Siberia, Lapland, cjcc, they form, cemented together by salts of lime, the edible earths which are mixed with meal to make a kind of flour. They occur also in large quantities in guano. As has already been stated, the position of the Diatomaceae in the natural system is a point on which there has been much controversy. Those who regard the mode of reproduction already described as a true process of conjugation place them in the class of Conjugatae, near to the Desmidiaceae, with which family they present many points of resemblance in external form, phenomena of spontaneous movement, &c. ; and it is possible that the diatoms may be derived from the desmids by retro- gressive metamorphosis. But we are, on the whole, disposed to the conclusion that they have a totally different origin ; their very wide dis- tribution in time and space, the sharp differentiation of the family, and the enormous number of species, favouring the view that they represent a comparatively small ascent from an archaic type which has never attained any higher degree of development. lUusirative genera: — Eunotia (Ehrb.), Diatoma (DC), Melosira (Ag.), Gomphonema (Ag.), Navicula (Bory), Rhabdonema (Ktz.), DIATOMACE.-E 425 Fig, 357— Diatomaceae : A, Ennotia monodon'Ehrh. ; B, Triceratinvi FavnsY\v[\>.\ C, Surirclla spiendida Ktz. ; D, Synedra Arciis Ktz. ; E, Xa-nczila rhoviboides Ehrb. ; /", Pkurosigma lacustre Sm. ; 6^, Coccone»ia ianceolatian Ehrb. ; //, M cridion constrictttni Rlfs. : 7, Achnanthes trei'ipes Ag. ; K, Diatuina elongatiivi Ag. (vaiiously magnified). (After W. Smiih.) 426 PROTOPHVTA Nitzschia (Hass.), Pleurosigma (W. Sm.), Achnanthes (Bory), Meridion (Leibl.), Bicldulphia (Gray), Amphora (Ehrb. I, Campylodiscus (Ehrb.), Cymbella (Ag.), Epithemia (Breb.), Pinnularia (Ehrb)., Stauroneis (Ehrb.), Surirella (Turp.), Synedra (Ehrb.), Mastogloia (Thw.), Amphipleura (Ktz.), Fragillaria (Lyng.), Tabellaria (Ehrb.), Aulacodiscus (Ehrb.), Coscinodiscus (Ehrb.), I-icmophora (Ag.). Literature. Agardh— Conspectus Diatomacearum, 1830. Ehrenberg -Die Infusionsthierchen, 1838. Kiitzing — Die kieselschaligen Bacillarien, 1844. Rabenhorst — Die Slisswasser-Diatomaceen Deutschlands, 1853. Rylands — (Marking of diatoms) Quart. Journ. Micr. Sc, i860, p. 25. Griinow — Oesterreichische Diatomaceen, 1862. Heiberg — Kritisk Oversigt Danske Diatomaceer, 1863. Cleve — Svenska och Norska Diatomaceer, 1868. \V. Smith — Synopsis of British Diatomaceee, 1872. Hamilton L. Smith — Conspectus of the Diatomaceae, Lens, 1 873, p. 63. Habirshaw — Catalogue of the Diatomaceee, 1877. Mereschkowsky— (Movements of diatoms) Bot, Zeit., 1880, p. 520. Hallier — Untersuchungen iiber Diatomeen, 1880. Brun-Diatomacees des Alpes, 1880. Van Heurck— Synopsis des Diatomacees de Belgique, 1 88 1. Ptitzer — Die Bacillariaceen, in Schenk's Handbuch der Botanik, ii., 1882. Castracane — Diatoinacea; of the C//a//^;/^ Fig. 367. — HapalosipJwn byssoide2is Kirch, (x 200). (From nature.) the direction of cell-division. Two or three contiguous pseudocysts in an older portion of the filament divide in a direction parallel to the axis of growth of the filament, and one of the new pseudocysts thus formed now becomes the basal pseudocyst of a lateral branch, which generally consists of a single row uf pseudocysts at right angles to the axis. In Plectonema Thur. the branches protrude outside the mucila- ginous sheath. Heterocysts are formed in all parts of the filament, but their function is unknown. 440 PROTOPHYTA Coleodestniiim Bzi. appears to be one of the simplest forms of the Scytonemace^. No pseudo-ramuh are formed ; the filam.ents increase by fission only, and a number remain united in a bundle within a common envelope. Mazcea (Bornet, Bull. Soc. Bot. France, 1881, p. 287) is, on the other hand, a genus in which the development is carried to its highest point. The gelatinous ' fronds' are about 25 mm. in diameter ; the heterocysts are borne on pedicels consisting of from one to three cells, and the whole appearance is that of a Rivularia, the filaments being immersed in a homogeneous jelly, and spreading from a central spot. No distinct sheath has been observed, nor any resting- spores or hormogones. In Petalonema Berk, the mucilaginous sheath forms a kind of broad coloured wing to the filament. Mastigocoleits (Lagerheim, Notarisia, 1886, p. 65) is a marine genus growing attached to the shells of molluscs, with both terminal and lateral heterocysts ; the filament sometimes ends in a hair, as in the Rivulariaceae. Drilo- siphon Jidianus Ktz., frequent on the damp walls of greenhouses, is characterised by an outer calcareous sheath, and is a remarkably pleo- morphic organism. According to Zukal (Oestcrr. Bot. Zeitschr., 1883, p. 73) it forms two kinds of hormogones, and displays a kind of alterna- tion of generations. The ordinary hormogones produce only more and more slender filaments, which gradually assume a moniliform character, and are then known as Nostoc parietinum (Rabh.). Eventually the cells of these nostoc-filaments separate, and assume the character of an Aphanocapsa, or, in other cases, become the organism known as Gloeocapsa fenestralis (Ktz.) ; or very slender filaments are produced, constituting the Leptothrix parasitica and muralis (Ktz.), which forms are distinctly connected genetically with Drilosiphon. These leptothrix- filaments may again break up into vibrio- and bacillus-forms. The second kind of hormogone has a fusiform shape, and consists usually of from four to eight pseudocysts. It may remam dormant for a time, and, on germinating, reproduces the ordinary thick filaments. Wille (Ber. Deutsch. Bot. Gesell., 1883, p. 243) and Scott (Journ. Lmn. Soc, xxiv., 1887, p. 188) have determined the presence of a cell- nucleus in Tolypothrix. Wille states also that in S^igonema compactum (Kirch.) the necklace-like pseudocysts are in direct communication with one another through perforations in their cell-walls. When this species passes into the Gloeocapsa-condition, the perforations disappear, in consequence of the gelification of the common sheath, and the separate cells then carry on their existence as distinct individuals. Under the name Tolypothrix amphibia, Zopf (Ber. Deutsch. Bot. Gesell., 1883, p. 319) describes an organism having both an aerial and an aquatic form, the latter being a true Tolypothrix with its filaments CYAXOPHYCEAL 441 enclosed in sheaths and breaking up into hormogones, from which is derived the aerial form with the nature of a Chroococcus, and dividincr in three directions. Rabenhorst and Cooke regard Stigonema, and the latter authority also Hapalosiphon, as genera of lichens ; and Bornet and Flahault state that several organisms described as species of Sirosiphon and Stigonema are really lichens in a more or less advanced stage of deve- lopment. Hansgirg (Oesterr. Bot. Zeitschr., 1884, and Bot. Centralbl., xxii. & xxiii.j 1885) considers the genera placed under Scytonemeae to be the highest forms of development of various organisms hitherto mostly placed under Oscillariaceae. In the same way, from Tolypothrix and Scytonema may arise, by further development, the corresponding forms of Hapalosiphon, Mastigocladus, Sirosiphon, Stigonema, Fischera, and other genera usually placed under Sirosiphoneae. With the exception of ]Mastigocoleus, the Scytonemaceae are found only in fresh water, in bog-pools, or very commonly on wet rocks or trunks of trees, or among moss. They may form mats of considerable thickness, but the individual filaments, including the sheath, seldom exceed o"o4-o'o5 mm. in thickness. Several Scytonemaceae are known to enter into the composition of lichens (see fig. 279 d.) Literature. Bornet — Notes Algol., fasc. i, 1876, pp. iv.-v. ; fasc. 2, 1880. pp. 135-156. Bornet and Flahault — Ann. Sc. Nat., v., 18S7, p. 51. Order 4. — Oscillariace.^ (including Cham^siphonace.e). The Oscillariaceae or Oscillatorie^, in which the Lyngbyeas are also included, consist of delicate blue-green threads, occurring singly or in large floating masses in fresh running, or more abundantly in stagnant, less often in salt, water. The filaments are cylindrical and unbranched, straight, or (Oscillaria princeps, Vauch.) with the terminal portion bent at an obtuse angle with the rest of the filament ; in Spirulina (Lk.) the whole filament is coiled in a corkscrew-like manner. The filament is divided by very delicate transverse septa into disc-shaped pseudocysts ; there is no differentiation between the two extremities. The cell-wall has the property of transforming its outer layers into copious mucilage, which forms a gelatinous sheath investing either single filaments, as in Lyngbya (Ag.)and Symploca (Ktz.), or a number of filaments, as in Inactis (Ktz.) and Microcoleus (Desm.). In most species of Oscillaria (Bosc.) and Spirulina a distinct sheath is either wanting or it is extremely thin and delicate, but the filaments are often imbedded in structureless jelly. 442 PROTOPHYTA The blue-green colour of phycocyanin is sometimes replaced by a red or violet pigment. Scott finds a cell-nucleus in several species of Oscillaria. The only certainly known mode of multiplication of the Oscillariacese is by a filament escaping from its mucilaginous sheath, and breaking up into hormogones^ each composed of a small number of pseudocysts, which round themselves off at both ends and develop into new filaments. The family derives its name from the oscillating or wavy motion with which the filaments are endowed. This consists in a creeping movement in the direction of the length of the filament, now backwards and now forwards, accompanied by a curvature of the filament and rotation round its own axis ; but, according to Borzi, this power of motion is limited to the reproductive period. The filaments of the Oscillariacese have a remark- able power of resistance to both cold and desiccation, to which they are adapted by the encysting of the filament and hardening of the mucilaginous sheath. The movements of the Oscillariaceae are greatly influenced by temperature and light, being much more active in warmth and sun- shine than in cold and shade, but their cause is involved in considerable obscurity. Cohn (Arch. mikr. Anat., 1867, p. 48) observed that the oscillating movements take place only when the filament is in contact with a solid substratum. Siebold(Zeitschr. wiss.Zool., 1849, p. 284) states that if the water in which they grow is coloured by indigo, the particles collect round the filaments of Oscillaria up to their apex, whether they are in motion or not. Some- times creeping spiral lines of pigment begin to be formed at both ends of the filament and meet in the middle, where the particles become heaped up into little balls ; or sometimes this begins in the middle and advances to both ends. The mode in which the particles of indigo adhere to the filament and to one another appears to indicate the excretion of mucilaginous protoplasm. Fig. 368 — Oscillaria t^nu s Ag. ( X 400). (After Cooke.) CYANOPHYCEyE 443 Engelmann (Bot. Zeit., 1879, P- 49) claims to have detected this external secretion in the case of Oscillaria dubia (Ktz.). Zukal compares the motion of Spirulina to that of a growing tendril, and asserts that it is intimately connected with the growth of the filament. It consists of a slow torsion of the entire helix round its own axis, and is the result of the more rapid growth in length of the filament than of the ideal axis of growth. If the motion is suddenly interrupted, the filaments become for a moment quiescent, and then retreat towards the central point of the movement, forming a dark green lump. Hansgirg, on the other hand (Sitzber. Bohm. Gesell. Wiss.,see Bot. Centralbl., xii., 1882, p. 361), considers the twisting and nodding movements to be due, not to the growth of the filament, but to osmotic changes in the cell-contents ; the separate cells exhibiting motion when the envelope itself is at rest. He regards the movements as of the same nature as those of the sarcode in the pseudopodes of Rhizopods and other Protozoa. The same observer states further (Bot. Zeit., 1883, p. 831) that in the protoplasm which had escaped from the broken end of a filament of O. princeps, he has observed Fig. 360. — Oscillaria princeps YsMch. {yi 200). (From nature.) a number of amoeboid cells from 9 to 12 |/ in diameter, nearly spherical in form, and putting out colourless pseudopodes about twice the length of the central body, and to these he attributes the motile properties of the protoplasm. He believes the cause of the oscillating motion to be that the internal protoplasm takes up water more rapidly, and conse- quently swells to a greater extent, than the enveloping sheath, causing the filament to move slowly backwards and forwards within the sheath. In those species in which each filament is not invested in a separate sheath, variations in the turgidity are also brought about by variations in the endosmotic and exosmotic currents. Finally Schnetzler (Arch. Sc. Phys. et Nat., 1885, p. 164) describes the moveaients in O. jerugineo- ccerulea (Ktz.) as of six different kinds, viz. : (i) rotation of the filament or of its segments round its axis ; (2) creeping or gliding over a solid substratum ; (3) a swimming change of position in the water : (4) rota- tion or flexion of the entire filament ; (5) sharp tremblings or concus- sions ; and (6) a radiating arrangement of the entangled filaments. Most of the species of the typical genus Oscillaria Bosc. grow in dense shmy tufts attached to other alg^e or floating bodies, th<^ filaments being not more than from 2 to 6 /( in diameter : in a few species, 444 PROTOPHYTA such as O. princeps (Vauch.), the diameter is much greater, the separate filaments, just visible to the naked eye, floating on the surface of the water. Lynghya Ag. is distinguished by its property of forming ' persistent cells,' the function of which is not known ; they may possibly be propagative spores. The species have a much less active motion than those of Oscillaria, and chiefly inhabit salt or brackish water. Symploca Ktz. grows in tufts, frequently among grass with the habit of a Rivularia. In Microcoleus Desm, and Inactis Ktz. a large number of filaments are enclosed in the same gelatinous sheath. The genera Chamaesiphon (A. Br.), Clastidium (Kirch.), Cyanocystis (Bzi.), and Dermocapsa (Crouan) (to which Thuret adds Xenococcus and Sphasrogonium, Rostaf) constitute Borzi's family of ChamcEsiphonacece^ dis- tinguished, according to that author, by the presence of coccogones, propa- gative cells of the nature of sporanges, in which conids are formed by repeated Hv^rjX^A^'jvfm'Ji^X^^^^^J'^ Fig. 370. — Spinilina fenrtisshna Ktz. ( X 400). (After Cooke.) Fig. 371. — Lytighya cestiiar-ii Liebm. (x 2co). (After Hauck.) division, the usual number in each coccogone being four, eight, or sixteen. Clastidium (Jahrhft. vaterl. Naturk. Wiirtemberg, 1880, p. 135) is characterised by each filament having a terminal bristle. Dermocapsa and Xenococcus are epiphytic on Catenella, Lyngbya, and other marine algae. The former genus has been placed among both Florideae and Fucaceae, owing to its mode of propagation ; D. violacea (Crouan) has a bright red colour, Flaxonema Tangl (Sitzber. Akad. Wiss. Wien, 1882) is a fila- mentous protophyte with the habit of an Oscillaria, but characterised by the presence of a disc-shaped chromatophore in the blue -green proto- plasm. Under certain conditions the filaments break up into zooglcea- iike colonies. Borzia Cohn (Jahrber. Schles. Vaterl. Cultur, 1883, p. 226) is a genus of Oscillariaceae with the habit of a bacillus, consisting oi CYANOPHYCE^ 445 Together short oblong rods, which oscillate slowly and are not enclosed in a gela- tinous sheath. In B. trilocularis (Cohn) each hormogone is composed uniformly of three pseudocysts only. Many of the Oscillariacece enter largely into the composition of the blue-green scum seen on the surface of stagnant ditches, *!!v:c with others of the Nostochine^e they are said to have the power of decomposing vegetable matter, and to this is largely due the foul stench of stagnant water. In addition to many species of Lyngbya a few belonging to other genera grow in salt or brackish water. Several species of Oscillaria are found in thermal springs. The relationship of the genera of Oscillariacece to one another, and even to genera at present included in other families, is still very obscure. Hansgirg believes that manv of the forms described as species of Chroococcus result from the breaking up of filaments of Lyngbya ; while, on the other hand, most of Kiit- zing's species of Leptothrix, and many of Oscillaria, may be simply hormogones of species of Rivulariacese, Scytonemeae, and Stigoneme^e, propagating by frequent divisions, and becoming invested in a more or less thick gelatinous sheath. Many species of Lyngbya may be only the young stages of development of those species of Calothrix and Scytonema to which they are found attached. Oscillaria or Lyngbya antliaria (Hansg.) he now regards as in reality an Aphanocapsa. The same author further states that in the ;B a Fig. 372. — Syjiiploca hydnoides Kt7. {(i, natural size ; b, x 200). (After Hauck.) iffllEDiaz^ Fig. -^T^.—Syinploca vioJacea Hauck (x 280). (After Hauck.) Lyngbye^ and other of the higher families of CyanophycecC, nuclei, pyrenoids, and chromatophores occur, but only when they are in a con- dition of retrogression from the filiform state, and are breaking up into the unicellular condition. Under the name Chroo??ionas Nordstediii Hansgirg describes (Bot. Centralbl., xxiii., 1885, p. 229) a biciliated 446 PROTOPHVTA organism with blue-green endochrome which he regards as the swarm- cell condition of a phycochromaceous alga which occurs normally in a filamentous form, probably as Oscillaria tenuis (Ag.) or O. Frolichii (Ktz.). Literature. Fresenius — Ueb. d. Ban u. d. Leljen d. Oscillarieen, 1845. Braun — Bot. Zeit., 1852, p. 395. Bornet and Thuret — Notes Algol., fasc. I, pp. iii. iv. ; and fasc. 2, pp. 1 32- 1 35. Zukal — Oesterr. Bot. Zeitschr., 1880, p. 11. Hansgirg— Oe>terr. Bot. Zeitschr., 1884, pp. 313 et seq. ; and Ber. Deutsch. Bot. Gesell., 1885, p. 14. Sub-class 2 and Order 5.— Chroccoccacese. The Chroococcace^ share with the Schizomycetes the distinction of being among the lowest forms of vegetable life. The separate cells are always microscopic, and are filled with a blue-green or violet endochrome which owes its colour to the phycocyanin dissolved in the cell-sap ; they contain neither distinct chlorophyll-grains nor starch, nor, except in Chroodactylon (Han sg.), a distinct nucleus. The cells are either isolated, or are more often connected together into colonies by a mucus formed from the disintegration of the outer layers of the cell- wall ; they are never united into a filament. This gelatinous envelope is either colourless and hyaline, or of a blue, brown, or olive colour, and is often strongly lamellated. In Chroo- coccus (Nag.) it is homogeneous and capable of swelling greatly ; in Glceocapsa (Ktz.) it is com- posed of two successive layers, and becomes eventually, in some species, crustaceous, and of a very dark brown or even black colour. The internal pseudocysts or gonids are never endowed with cilia, as in some Protococcaceae, and are usually quiescent ; but in Microcystis (Ktz.) they have a constant 'swarming' motion within the hyaline envelope. The entire organism has usually a power of slow spontaneous motion. Multiplication by swarm-spores or zoospores is unknown except in the doubtful case of Merismopedia (Mey.) (Goebel, 'Outlines of Classification,' p. 22). jResti fig- spores or cysts (akinetes) are formed in Glceocapsa by the cells of which a colony is composed investing themselves, while still within their common gelatinous envelope, in a rough or spiny coat of Fig. 374.— Stages in the de- velopment of Chroococcus Uirgidus Nag. (greatly mag- nified). (After Reinke.) CYANOPnvCE.-E 447 cellulose ; the spiny resting-spores thus formed reproduce the colony by division after a period of quiescence. With the above exceptions the only mode of propagation in the Chroococcacese is by division — repeated bipartition of the cell, which may take place in one, two, or three directions. This is usually accompanied by the disappearance of the separate gelatinous envelope of each indi- vidual cell ; but in Glofocapsa these still remain, and as many as three or four generations of families may be enclosed within the original envelope, each surrounded by its own investment. In Chroococcus Nag- it is not unusual for the individual cells to be entirely isolated within the common envelope. In Synechococcus Nag. division takes place in one direction only, and the derivative cells remain attached to one another JQ 10 0 . 0 Q.» ^^"^ ^< r^-. § ^^ %.^^ OO ' Fig. 375. — Aphanoihece uturoscoplca Nag. (x 70). (From nature.) Yig'. ^^S.— Glasothece granosa Rabh. ^, gela- tinous colony (magnified) ; B, cells ( x 25c). (After Couke.) in a string ; but the attachment is very loose, and soon ceases. In Merismopedia, Tetrapedia Reinsch., and Gloiochcete Lagerh. division takes place in two directions, the result being the formation of a plate of cells, often of great regularity. In Chroococcus^ Gl(eocapsa^ Glceothece Nag., Aphanocapsa Nag., Aphanothece Nag., Microcystis^ and most other genera, division takes place in all three directions. In ClatJwocystis Henf the gelatinous envelope, which is of great extent, is broken up into clathrate segments. In Coelosphceriiun Nag., a common organism in bog-pools moving about with considerable rapidity, it is lobed at the margin, the pseudocysts appearing like blue-green projections on the surface of the globe. Chroodactylon Hansg. (Ber. Deutsch. Bot. Gesell., 1885, p. 14) is distinguished by the formation of cell-families branching in an arborescent manner, by its distinct cell-nucleus, and 448 PROTOPHYTA by the star-shaped chromatophores which enclose moderately large pyrenoids. It has possibly been erroneously referred to this family. Most of the genera and species of Chroococcaceae grow in moist situations, as on damp rocks, where they frequently form large shining blue-green mucilaginous masses ; others swim freely on the surface of bog-pools ; a few are found in salt water, attached to sea-weeds. The gonids or algal constituents of many lichens have been shown to be pro- tophytal organisms belonging to the Chroococcaceae. As it is highly probable that many forms at present included in the family are stages in the history of development of more highly organised protophytes, or even of algae, their place in a final system of classification is altogether un- certain until their life-history has been more thoroughly investigated. Many are closely analogous to corresponding forms among the Protococ- caceas, as Chroococcus to Chlorococcum, Gloeocapsa to Gloeocystis, Fig. 377. — Microcystis marginata Men, Fig. ■^■jZ. — Coei-osphcErhim Kutzingiamim Nag. (x 400). (After Cooke.) (X400). (After Cooke.) Aphanocapsa to Protococcus, Coelosphaerium to Botryococcus, and Merismopedia to Tetraspora ; but they are probably merely parallel series of forms without any direct genetic connection. Richter, however, identifies Gloeocapsa and Gloeocystis. The same observer suggests also a genetic afiinity between the various genera usually included under the Chroococcaceae of the follow- ing nature. The lowest form is the naked Aphanocapsa-condition, corresponding to Palmella among the Protococcaceae. From this naked or only sHghtly encysted condition is developed the Gloeocapsa- or Gloeocystis-form, with several gelatinous envelopes, the Chroococcus- condition, where the investment is altogether wanting, and the coenobe- or Coelosphaerium-condition, where there is only a slight vesicular envelope. The Gloeocapsa-form is especially adapted for exposure to air and growth upon a comparatively dry substratum ; the coenobe-type is developed in water or on a moist substratum in the air. With this is connected the cylindrical form, a higher stage, because it displays differentiation in the direction of growth, and a development towards CYANOPHYCE^E 449 the filiform condition. This cyUndrical condition, when attained, is usually unstable, but becomes stable in Synechococcus. Gloeocapsa may also pass into an encysted filiform condition in Sirosiphon (see p. 439). Zopf insists on the close afifinity between the blue-green Schizo- phyceas and the Schizomycetes. Hansgirg regards many of the forms included under Chroococcus as resulting from the breaking up of fila- ments of the higher Cyanophyceae such as Lyngbya, while Gkeocapsa may be derived in the same way from Stigonema, and Synechococcus from Calothrix. He believes, in fact, most if not all of the organisms hitherto included in this family to be connected, by retrogressive metamorphosis, with other more highly developed forms, and even possibly in some cases (Flora, 1886, p. 291) with the protoneme of a moss, r^^licrocystis is regarded by Richter (Hedwigia, 1885, p. 18) as a resting-form of Euglena. The Chroococcaceae, like the other Cyanophyce^ and the Protococcaceae, enter largely into the composition of Lichens. The reader will find this subject amply treated by Bornet in his ' Recherches sur les gonidies des Lichens ' (Ann. Sci. Xat., 5 Ser., xvii. and xix.). Literature. Nageli- Gattungen einzelliger Algen, 1849. Borzi — Nuov. Giorn. Bot. Ital., 1878, p. 369 ; and 1S79, p. 47. Richter— Hedwigia, 1880, pp. 154, 169, 191. Zopf — Bot. Centralbl. , x., 1882, p. 32 ; and Ber. Deutsch. Bot. Gesell., 18S3, p. 319. Tangl — Anzeiger Akad. "Wiss. Wien, 1883, p. 87. Hansgirg— Oesterr. Bot. Zeitschr., 1884, pp. 313, 351, 389; and Bot. Centralbl. xxii. and xxiii., 1885. GROUP IL AND CLASS XXVIIL— SCHIZOMYCETES (BACTERL\). Though this group has been the subject of a great deal of investiga- tion and much speculation, it cannot be said that our knowledge of it is in due proportion to the literature. The minute size of the cells pre- cludes an exact study of their structure. This leads to errors of deter- mination and to confusion of forms in culture experiments, and thus renders difficult the study of the course of development. A large number of the investigators have been and are unequipped with a knowledge of natural history, and are unfitted to appreciate the significance of phenomena observed, or, in other cases, are incapable of observation of G G 450 PROTOPHYTA the kind at all. Records of the successive occurrence of different forms in the same situation have been substituted for direct observations of continuity, while errors of even grosser kind abound in the vast literature of the subject. Bacteria are the present refuge of those who believe in ' spontaneous generation,' just as higher forms of organ- ised beings were the subject of their speculations in former times, when the instruments of investigation were less perfect. Bacteria are either single minute cells of roundish form, or cylin- drical and rod-like cells or rows of cells. As has been said, their very minute size has prevented our attaining an exact knowledge of the cell- structure. The cell-cavity is ordinarily filled with homogeneous proto- plasmic contents. Chlorophyll has been discovered tingeing the proto- plasm in three forms — Bacterium viride and Bacillus virens of Van Tieghem, and more faintly in Bacterium chlorinum of W. Engelmann. A red colouring matter discovered by Lankester, and named by him bacteriop2{rp2i7'm^ tinges the protoplasm of Beggiatoa roseo-persicina (Zopf ), but though colours are often associated with masses of Bacteria, it is difficult to discern in the magnified view the exact seat of it, whether it occur in cell-contents, cell-wall, or substratum. In some forms (which do not contain chlorophyll) a substance resembling starch is found. No one has yet detected nuclei with absolute certainty. The cell-membranes are very dehcate, and in such cases as Spirillum (Ehrenb.) highly elastic, but it happens to most Bacteria at one stage of their development that gelatinous outer layers are formed, which either invest single cells and cell-groups, or unite into masses large numbers of cells. A great number of Bacteria have the power of free movement. During such movement rotation takes place round the longitudinal axis, while movements of oscillation also occur in other forms. Ciha or flagella are found in some, but not all, of these moving Bacteria, and it has not been proved that they are motile organs as one might too readily infer. As a matter of fact it is not known, in many cases, whether these flagella are parts of the membrane or of the protoplasm protruded through it : and since they are not always present in motile Bacteria, they need not be regarded as essential organs of locomotion at all events. A^arious growth-forms occur which were at first associated with dif- ferent Bacteria and received generic names. Individual Bacteria are either roundish or in the form of straight rods, or of twisted rods. As de Bary has remarked, ' a billiard ball, a lead pencil, and a corkscrew so exactly illustrate these three chief forms,' that there is no need of models to convey instruction in this respect. The round growth-forms are termed Coccus (^Micrococcus Cohn &c.) ; the rod-like forms include those SCHIZOM ] 'CE TKS 45' which have been termed Bacillus Cohn (long rods), and specially Bac- terium Cohn (short rods) ; the shortly coiled forms are known as J^idrio Cohn ; and the spiral forms have received the names of Spirillum Ehrenb., Spirochceta Ehrenb., &c., and the very elongated filiform forms are Leptothrix Ktz.. Beggiatoa Trev. &c. Involutio?i forms are swollen bladder-like structures of irregular outline probably produced Ijy malnutrition. These growth-forms of cells or of -individuals either occur free, or in the form of filaments, or more seldom of flat surfaces or cube-like packets. Large gelatinous masses called Zoogloea, composed of numerous individuals of these growth-forms, occur in various situations such as the surfaces of fluids and solids, or they may be found suspended in fluids. o O O « OO 'OO^ Fig. 379. — Bacillus Fitziamts Zopf. Transition forms from round cocci to rods d, with spores ( x 4,000). (After Buchner.) Such forms of Bacteria are grouped into two divisions, viz. those which form their spores endogenously, the Ejidosporoiis Bacteria, and those which have no such mode of forming spores, the ArtJwosporous Bacteria. This classification, which can hardly be regarded as finally satisfactor}', corresponds, at all events, with the state of our knowledge of the course of development of Bacteria. Endosporous multiplication is accomplished by the formation within a cell of a minute, granule-like body, which gradually enlarges, while the surrounding protoplasm disappears until it reaches its mature form G G 2 452 PROTOPNYTA ^%4^ within the wall of the mother-cell. The mature spo?'e is usually a highly refringent body with definite outline, and of globular or ellipsoidal form. The formation of spores commonly takes place when the substratum yields no more nourishment, or vegetation is otherwise interrupted, and it usually occurs in most of the cells, others remaining sterile. Arthro- sporous reproduction is effected by the simple separation of members which form the starting point of new growths. The spores of Bacteria are capable of germination from maturity onwards, often for considerable periods. They withstand the operation of external agencies, such as ex- treme degrees of temperature and the like, with varying success, many of them exhibiting astonishing en- durance. Such arthrosporous forms as Beggiatoa, which vegetate in water, are probably incapable of withstanding desiccation at a very high temperature, but the spores of endosporous Bacteria possess, many of them, remarkable powers of endurance. The spores of Ba- cillus Anthracis (Cohn) (the cause of splenic fever) remain alive in absolute alcohol. They may be kept for at least three years in an air- dry state, and for at least one year in water, and probably for longer either in air or in water. They were found by Brefeld to with- stand boiling in a nutrient solution for a quarter of an hour, the greater part of them for half an hour, a smaller number for one hour, but none for three hours. And so with the spores of other forms. The tempe- ratures at which germination takes place, the minimum, the optimum, and the maximum, vary with different forms ; but for the most part the minimum and certainly the optimum may be said to be above the ordinary temperature of a room. Similarly the optimum temperature for vegetation is usually high, being about 3o^C., speaking ver}' generally. With reference to their behaviour towards the supply or exclusion of Fig. ■^%o.—Bacilhts Megatey-uim de By. a, outline of a motile chain of rods ; b, a pair of same ; p, a quadricelluiar rod after treatment with alcoholic solution of iodine ; c, a five- celled rod before spore-formation ; d—f, suc- cessive stages of pair of rods while forming spores, about an hour interval between each — state d was about two o'clock afternoon, and the spores in y were ripe towards evening ; r, a quadricelluiar rod with ripe spores ; g^ a five-celled rod with three ripe spores placed in a nutrient solution after several days' desic- cation at 12.30 ; g", same about 1.30 ; ^', the same about 4 o'clock ; h}, two spores with the walls of the mother-cells dried, and then placed in a nutrient solution about 11.45 ; ^^'j the same about 12.30; z, k, I. later stages of germination ; m, a rod formed from a spore placed eight hours before in a nutrient fluid, and in the act of splitting transversely, {a x 250, the other figures x 600.) (After de Barj-.) SCHIZOM YCE TES 453 Fig. -^Zy.— Bcggiatoa alba Trev. i, group ot filaments. 2 — 5, filaments of varjnng thickness, 5 breaking up ; small dark circles in all cases grams of sulphur : where such are abundant transverse segmentation is indistinct. 6—8, filaments rich in sulphur showing transverse segmentation after treatment wiih solution of methyl violet ; in 8 longitudinal division is shown (formation of cocci or spores). 9, filaments which have broken up into spores. 10, motile spores, (i x 540, other figures X 90Q.) (After Zopf.) 454 PROTOPHYTA oxygen, there is great variation among Bacteria. This variation extends from those forms, called aerobiotic by Pasteur, which require a plentiful supply of free oxygen for the purpose of vegetation (e.g. Bacillus sub- tilis, Cohn), to others {an aerobiotic) in which vegetation is promoted by its exclusion (e.g. Bacillus Amylobacter, Win Tiegh.). Intermediate forms occur between such extremes ; and Xageli has shown that aerobiotic forms continue to vegetate when the supply of free oxygen ceases. Speaking in general terms, what has been said already of the mode of life of Fungi in other respects, e.g. nutritive adaptation, holds good of such Bacteria as contain no chlorophyll. They are saprophytes exciting fermentations and producing combustions of the substratum, and putrefactive processes ; or parasites, though very rarely on living plants, it may very well be on account of the acid reaction. As para- sites in living animals they obtain the greatest share of our interest, since, as ever}'one knows, it is sought to connect them with a large number of diverse diseases. Thai this attempt is made with the greatest rashness in many cases, on utterly insufficient data, often on the mere presence of some vaguely determined form in diseased tissues, is a scandal of medical literature. On the other hand it has been thoroughly proved in certain cases that their presence and action have the character of exciting causes of disease, and it cannot be doubted that painstaking research will bring to light numerous other instances of equal weight. Slipshod research will only retard progress in this direc- tion. It has already done much in obscuring results, and in placing obstacles in the path. The most noteworthy feature, as de Bary has pointed out, in the parasitism of Bacteria in the living bodies of animals is their facultative parasitism — (as illustrated for example in the well-established case of Bacillus Anthracis in anthrax or splenic fever), a matter of grave importance from the medical point of view. Among saproph}tes may be mentioned Bacterium Termo (Duj.), an exceedingly abundant agent of putrefaction ; Bacillus Megaterium (de By.) (fig. 380), and Beggiatoa alba (Trev.) (figs. 381, 382), the ' sewage-fungus ' of engineers, found in sulphuretted waters, the effluents from manufactories and sewage-works, which has a remarkable power of extracting sulphur from the water, and storing it up in the form of minute refringent globules. As regards the position of Bacteria, ' to say that they are offshoots of the Fungi is to " contradict all trustworthy observations " so flatly, that the view need not be seriously discussed in this place' (de Bary, *Comp. Morph.,' (S:c., p. 474). They are only fungi in the ver}- limited sense of their being 'thallophytes which contain no chlorophyll,' and indeed it SCHIZOM YCE TES 455 has been seen that certain Bacteria do contain chlorophyll. Looking at their morphological characters, so far as these are at present known to us, it cannot be doubted that the nearest allies of the Arihrosporous Bacteria are those Protophyta, Nostocace^e, Oscillariaceas, Chroococcace?e, (Sec, which contain chlorophyll. Leuconostoc (\'an Tiegh.) has already been mentioned (p. 433) as an intermediate form. A gap certainly exists between Arthrosporous and Endosporous forms ; but so far as Fig. 2^2.— Bcggiatoa alba Trev. Cun-ed and spiral forms. A, attached filaments. B—Il, por- tions of spiral filaments ; H showing separate cells, E swarming ('spirillum') with a cilium at each end. Small dark circles are sulphur granules ( x 540). (After Zopf.) can be seen the latter stand nearer to the former than to any other group, and the interval which separates them may become narrower with farther knowledge. On the other side a connection appears to be in- dicated between Bacteria and the Flagellata ; but more than this one 456 PROTOPHYTA can hardly say. In conclusion, and as summing the matter up, the words of de Bary (' Comp. ]Mori)h.,' kslc, p. 475) may be quoted. ' If we assume for a moment a connection between the Bacteria and the Flagellata, it is evident that as a consequence the following series of forms converge to the Flagellata : firstly^ the series of Bacteria and the Nostocace^ ; secondly^ that of the Mycetozoa ; thirdly, that of the chlorophyllaceous Algas, with which are connected in ascending line the main series of the vegetable kingdom and of the Fungi as one or more lateral branches. . . . fourtJily, and lastly, the Rhizopoda and the Protozoa with the animal kingdom, which connects with these in an ascending line.' Literature. De Bary — Vorlesungen liber Bacterien (Leipzig, 1885 and 1886). (See English trans- lation by Garnsey and Balfour, Oxford, 1887.) The above contains an admirable guide to the literature of the subject. (See also the same author's Comparative Morphology, &c. ) Cornil et Babes — Les Bacteries, &c. , 2nd ed. (Paris, 1886). Crookshank — Introduction to Practical Bacteriology (London, 1886). Duclaux— Chimie biologique (Paris, 1883). Grove — A Synopsis of the Bacteria and Yeast Fungi (London, 1884). Klein — Micro-organisms and Disease, 3rd ed. (London, 1886). Hueppe — Die Formen der Bacterien (Wiesbaden, 1886). Hueppe — Die JNIethoden der Bacterienforschung (Wiesbaden, 1885). Zopf— -Die Spaltpilze (Breslau, 1884). The references to the vast literature of the subject in the above books will be a sufficient guide to the most ardent student. At the same time it would be unpardon- able to abstain from a special reference to the labours of Cohn, Pasteur, Koch, Lan- kester, Brefeld, Van Tieghem, Prazmowski, Naegeli, and Lister, since these are of fundamental importance. INDEX. -*o*- {The figures in large type refer to Illustrations.) ABI Abies, 3 Abjunction, 312, 275 Absidia (Van Tiegh.), 338, 339 Absorbing system, 138 Acanthococcus(Lagerh.), 417 Acetabularia (Lmx.), 286, 2d1, 252 — mediterranea (Lmx.), ^51, 252 Achlya (Xees ab Esenb.), 335, 346, 291, 292 — polyandra (Hildebr.), 2yi — racemosa (Hildebr.), 29 l Achnanthes (Bory), 426 ~ brevipes (Ag.), fol Acrasieae, 401, 405, 406 Acrasis (Van Tiegh.), 405 Acroblaste (Reinsch), 280 Acrocarpi, 149 Acrogynous Jungermanniaceai, 161 Acrospore, 330, 343> 352, 361, 362, 363, 364, 3^5, 367, 368, 369. 370, 372, 373. 374, 376 Acrostichese, 80, 83 Acrostichum (L.), 85 Adder's Tongue, 100 Adiantum (L.), 85, 44, 50, 58 — capillus-Veneris (L.), 44, 50 Adventitious bud, 77, 81, 100, 49 ^cidia, 384, 385, 386, 314 iEcidiospore, 6, 384, 385, 386, 314 yEcidium(Pers.). 383 _ iEgopodium Podagraria, 348, 349 Aerial leaf, 28, 7, 8 Aerobiotic Bacteria, 454 iEthalium septicum (Fr.), 403 Agar-agar, 210 Agaricini 393, 394, 270, 273 318-321 Agancus (L.), 4, 392, 393, 270, 273, 319, bd^i — campestris (L.), 320 — or^'ophilus (Bull.). 273 — Emerici (Berk.), 316 — Gardn-ri (Berk.), 316 — igneus (Tub), 316 — lampas (Berk.), 316 — malleus (L.), 309, 310, 316, 392, 270, 319 — noctilucens (L^v.), 316 — olearius (DC.), 316 Agarum (Grev.), 244 Aglaozonia (Zan.), 251 — reptans (Ktz.), 252 Air-bladder, 232, 236, 241, 244, 206, 207, 211 ANO Air-cavity. 102, 105, 100, 147, 167, 169, 2J, 110, 112, 153,' 154 Akincte, 185, 258. 274, 446 Alaria (Grev.), 239, 244 — escuienta (L.), 244 Alcoholic ferment, 380 Alga, 2, 3, 4, 184, 16&-265 Algal cells of Lichens, 318, 319, 370, 279-282, 307,308 Alsophila aculeata (Klotzsch), 57 Alteinaria (Nees ab Esenb.), 374 Alternation of generations, 16, 1S2, 180, 214, 263,325, 440 Amanita, 393 Amansia (Lmx.), 194, 209 Amoeba, 406 Amoeboid motion, 196, 199, 217, 274, 284, 344, 401, 402, 403, 405, 406 Amphigaster, 160, I3ci, 139 Amphipleura (Ktz.), 426 Amphiroa (Lmx.), 206 Amphithecium, 145 Amphithrix (Ktz.), 437 Amphora (Ehrb.), 426 Amylum-star, 176 Ana'bjEna (Borj-), 430, 432, 433, 360 — flos-aquae (Fr.), 360 Anacrogynous Jungermanniaceae, 161 Anadyomene Lmx.), 289 Anaerobiotic Bacteria, 454 Ancylistea;, 4, 330, 344, 345 Ancylistes(Pfi[z.), 331 — Closterii (Pfitz.), 330 Andrejea (Ehrh.), 145. 150, 123, 124 — alpestris (Schmp.), 123, 124 AndreseacejE, 136, 150, 123, 24 Androspore, 6, 225, 202 Aneimia (Sw.), 78, 90, 91, 43 — Phyllitidis (Sw.), 43 Aneura (Dum.), 164 Angiopteris (Hoffm.), 91, 94, 95, ''^ — caudata (De Vriese), 71 — evecta(Hoflm.), 93 Angiospcrms, 12, 13 Annularia(Brongn.), 126, 101 Annulus, 74, 78, 86, 89, no, 122, 146, 393, 55, 56, 83, 110, 112, 319, 320 Anomoeneis spherophora (Pfitz.), 354a 458 INDEX ANT Antherid, 7 (see also under Vase. Crvpt.. Muse, Char., Alga;, and Fungi). 11. 30, 36. 43. 44, 65, 74, 78, 106, 108. 130, 141. 157, 163-165, 175- 177, 192, 199, 201-203, 208, 210, 248, 259. 286, 290,291,303-306,314 Antheridial tube, 291 Antherozoid 7 (see also under Vase. Crypt., Muse., Char., Alga;, and Fungi). 11. 15. 17, 20, 30, 44. 78, 108, 130, 157, 163. 199, 201, 210, 248, 259. 290 Anthoceros(L.), 157, 16:;, 144. 145 " la;vis (L.), 144, 145 Anthoceroteae, 159, 164, 144, 145 Antipodal eells, 15 Aphanizomenon (^lorr.), 430, 432, 361 — flos-aqua; (Morn), 432, 361 Aphanocapsa (Nag), 412, 440, 445, 447 448 Aphanomyces (de By.), 334, 335 Aphanothece (Nag.), 447, 375 — microscopiea (Nag.), 375 Aphlebia, 120, 92 Apical eavity, 179 — cell, 23, 41, 74, 90, 98, 102, 105, 156, 173, 174, 176, 191, 214, 228, 241, 437, 52, 162 — papilla, 179 Apiocystis (Nag.), 413, 341 — Brauniana (Nag.), 341 Aplanes Braunii (de By.), 334 Aplanospore, 185, 258, 274 Aplolepidae, 148 Apogam3^ 11, 52, 69, 86, 47 Apophyse, 148, 112, 124 Aposporj-, II, 69, 86, 48 Apothece, 355, 356, 370, 372, 373, 308 Appendage, 378, 379, 312 Appendiculcb, 363 Aquilegia, 364 Archaeocalamites (Stur), 126, 99 — radiatus (Stur), 99 Archegone. 8 (see also under Vase. Cr\T3t.. Muse., Char., and Alga;), 4. 10. 14, 20', 29. 43, 45, 46.61, 74, 79. 80. 109, 131. 141. 142! 147, 148, 158, 164, 165, 166 Arehegoniophore, 86, 61 Archespore. 13, 20, 36, 60, 80, 99, iii, 134, 135, 144, 146, 159, 33, 56, ilO Archidium (Brid.), 145, 150 Areolation, 420 Arthrocladia (Duby), 245 Arthrodonteae, 148 Arthropitys (Gijpp.), 126 Arthrosporous Bacteria, 451, 452, 455 Artotrogus (Mont.), 325 Ascobolus (Pers.), 356, 359, 360, 361, 368, 369, 37O) 372. 378, 305 — furfuraceus (Pers.), 305 Ascogenous h>TDha;, 353, 355, 360, 364, 366, 367, 368, 369, 370, 372, 373, 374, 305, 306, 308 Ascogone, 360 Ascomycetes, 4, 312, 353, 383. 386. 267, 268, 271, 276, 278, 300-313 — course of development, 361 — homologies of the organs. 377 — (doubtful), 4, 378, 312, 313 Ascophylla (Stackh.), 235 Ascospore, 6 (see also under Ascomvcetes), 268, 276, 278, 300, 304, 311, 312, 313 Ascotrieha (Berk.}, 370 Ascus, 353 (see also under Ascomycetes), 276, 300, 303, 305, 308, 311, 312 Aseroe (La Bill.), 398, 331 — rubra (Berk.), 331 Aspergillus glaucus (Lk.), 366 Asperococcus (Lm.v.), 241. 245, 218 — bullosus (Lmx.), 218 BAT Aspidiea;, 83 Aspidium (.Sw.), 85, 42, 55, 58 — filix-mas (Sw.), 72, 76, 77, 82, 42, 55 Aspleniese, 83 Asplenium (L.), 69, 85, 49, 51, 56, 58 — Adiantum-nigrum (L. ), 51 — bulbiferum (Forst.), bi — decussatum (Sw.), 49 — Trichomanes (L.), 56 Assimilating tissue, 138, 193 Asterophyllites (Rev.), 126, 130, 101 Asterotheea (Presl), 122, 94 — Sternbergii (Stur), 94 Astromyelon (Williams.), 126 Athyrium filix-fremina (Bernh.). 69, 76 Atrichum undulatum (P. B.), 102, 119 Attachment-disc, 228 Aulacodiscus (Ehrb.), 426 Aulacomnion (Schw.), 149 — androgynum (Schw.), 140 Aulosira (Kirchn.), 430, 433 Auricle, 92, 161, 140 Auxiliary cell, 203 Auxospore, 6, 422, 423, 355 Azolla (Lam.), 19, 26, 31, 115, 12, 13 — caroliniana (Willd.), 13 — filiculoides (Lam.), 12 Azygosperm, 338, 340, 342, 343 Azygites(Fr.), 338 Bacillariace^, 419 Bacillus (Cohn), 440, 451, 379, 380 — amylobacter (Van Tiegh.), 454 — anthracis (Cohn), 452, 454 — Fitzianus (Zopf), 379 — Megaterium (de Bj'.), 454, 380 — subtilis (Cohn), 454 — virens (Van Tiegh.). 450 Bacteria, 305, 306, 449 — conditions of vegetation, 452 — growth-forms of, 450 — mode of life, 454 — movements of, 450 — spores of, 451, 452 Bacteriopurpurin, 450 Bacterium (Cohn), 451 — chlorinum (Engelm.), 450 — Termo (Duj.), 454 — viride (Van Tiegh.), 450 Bseomyces (Pers.), 361 Balsamia (^^itt.), 358 Bangia (Lyngb.), igo, 191, 216, 193-195 — ceramicola (Chauv.), 193 -- fusco-purpurea (Lyngb.), 194, 195 Bangiacea;, 216 Barberry, 383, 384, 385 Barbula (Hedw.), 140, 147, 149, 105 Barilla, 190 Bartramia (Hedw.), 149 Basal cell, 68 Basid, 312. 384, 385, 388, 389, 39o> 393, 394> 275, 317, 321 Basidiomycetes, 4, 306, 312, 388, 266, 270, 273, 316-331 Basidiomycetous Lichens, 319" Basidiospore, 6, 312, 388, 389, 390, 275, 317,. 321, 322, 325, 329 Basilar cell, 433, 365 Batarrea(Pers.), 308, 397, 325, 326 — Steveni (Fr.), 325, 32b P5atrachospermese, 211, 189-191 Batrachospermum (Borj-). iQi> 211, 212, 213,. 214, 189 — moniliforme (Roth), 189 INDEX 459 LEA Beam, 226, 2M Beer-yeast, 268, 313 Eeggiatca (Trev. , 4, 451, 452, 38i, i>^^ — alba (Trev.), 454, 381, 38ki — roseo-persicina (ZopO, 45° Biddulphia (Gray), 426 Binuclearia (Witt.), 276 Bladder-wrack, 230, 236 Blasia (Mich.), 156, i57, 164 Blechnum (L.), 85, 58 Blyttia(b:ndl.), 160 Bog-mosses, 151 Boletus (L.), 392, 3q6 Bonnemaisonia(Ag.), 201 Bornetia(Thur.X i94, 209 — secundiflora (Ag.), 194 Bornia (Brongn.), 126 Borzia (Cohn), 428, 444 — trilocularis (Cohn), 445 Bothrodendron (L. and H.), 116 Botr^-chium (Sw.), 97, 98, 99, JLf' ^^"'^ — Lunaria (Sw.), 97, 98, 100, 76-/t) Botrj^diaceas, 280, 285, 250 Botrj-dina (Breb.). 186, 412 Botrydium (Wallr.) 186, 284, 285, 41°, 412, ^5U — granulatum (Wallr.;, 285, 250 Botryococcus (Ktz.), 186, 418, 448, 549 — Braunii(Ktz.), 349 Botr3-opteris(Ren.), 122 Botrj-tis cinerea ( Pers.), 374 Brach^-trichia (Zan.), 437 Bract, 173, 163-165 Bracteole, 173 Brake, 82 Breaking of the meres, 432 Brittle-worts, 181 Brownian movement, 269 Bruckmannia (Sibg.), 127 Bri-acea, 136, 146, 102-120 Bryum(L.), 145, 149, .H^ — argenteum (L.), iio Bryopsideae, 289 Brj'opsis (Lmx.), 289, 290 Bud, 133, 181, 196, 214, 250, 252, 15^ Bulbil, 61, 67, 176 Bulbochaite (Ag.), 188, 222, 226, 3id. — setigera (-Ag.), 202 Bundle-sheath, 44, 109 BursuUa (Sorok.), 405 Buxbaumia (Hall.), 149 Cabbages, 326 Calamarieae, 125. 130, 96-100 Calamites, 125, 126, 97 Calamitina (Weiss.), 126, 98 Calamocladus (Schmp.), 126 Calamodendres. 125 Calamodendron (Brongn.), 125, 126 Calamostachys (Schmp.), 125, 127 . Calcareous incrustation, 181, 195, 206, 211, itb, 304, 403, 440, 167 Calcium oxalate, 85, 308 Callithamnion (Lyngb.), 4, 189, 191, i94. 204, 180 — caudatum (Ag.), 194 — seirospermum (Griff.), 204, 80 — versicolor (Drap.), 204 Callus, 240, 244. 217 Calothrix (Ag.), 435. 43^, 445, 449. <^b4 — Crustacea (Thur.), 364 Calotrichaceae, 433 Calypogeia (Radd.), 162, 164, 154 — Trichomanis (Cord.), 134 Calypter, 134, i44. 110> 114, 117, 131, CHI Campylodiscus (Ehrb.), 426 Canal, 143. 109 Canal-cell, 69, 133, 45 Capillitium, 358, 396, 397, 404, 326, 334 Capitulum, 177, 163 Capsella bursa-pastoris, 326 Capsosira (Ktz.), 439 Carinal canal, 106, 108 Carpogenous cells, 176, 179 Carpogone, 8, 185. 199, 359, 360, 361, 362, 363. 364, 3*55. 366, 367, 368, 369, 370, 371, 372, 373» 385, 179, 303-30/ Carpomitra (Ktz.), 241 Carposperm, 185, 201, 203 Carpospore, 185, 201, 222, 263, 179, 199 ' Carposporeae, 3 Carpostome, 201 ' Carrageen moss,' 210 Casuarina, 113 __ Catharinea undulata (^ . & M.), 102 Caudex, 71 Caulerpa (Lmx.), 289, 256 — prolifera(Lmx.),Ji56 Caulerpea;, 289, 256 Cell-cap, 222, 2(X) Cellulin, 176 Central bundle, 138 — cavity, 105, 81 — cell, 10, 14. 17, 26, 31, ^9, 133, 143, 159, ^'^■> 158 — node, 353 Ceramiaceae, 196, 204, 172, 179-181 Ceramidium, 201 Ceramium (Lyngb.), 204, 181 — strictum (C^rev.), 181 Ceratieae, 404 Ceratium (Lk.), 404, 335 — hydnoides (Alb. 6t Sch.), 355 — porioides (Alb. ^S: Sch.), 335 Ceratodon (Brid.), 149 ^ Ceratopteris thalictroides (Brongn.), 77, bi, ^^ Ceterach Adans.), 85 Cetrarla islandica (Ach.), 283 Chaetangiaceae, 211 Chaetociadiea;, 339 Chaetocladium (Fres.), 339, 340, 35^ Chaetomium (Kze.), 370 — fimeti (Fckl.), 356 Chaetomorpha (Ktz.), 276 Chaetopeltis (Bert.), 222 Chaetophora (Schr.), 273, 275, 276 Chaetophoraceje, 222, 258, 273, 275, 279 Chaetopteris (Ktz.), 249 — plumosa (Ktz.), 249 Chstostylum (Van Tiegh.), 339 Chalara Mycoderma (Cienk.), 380 Chamaesiphon (A. Br.), 444 Chamaesiphonacea;, 441, 444 , ._^ ,q, Chantransia(Fr.), 211, 213, 214, 210, IW, lai — cori'mbifera (Thur.), 214, 191 — virgatula (Thur.), 190 ,s. ifiP- Chara(L.), 174, i75, 170, i79. ^Si, 182, ibt 162, 164, 167, 168 — aspera (Willd.), 176 -- crinita (Wallr.), iSi — fragilis (Desv.), 176, IbO 162, 164, 168 — hispida(L.), 176, 161, 16? Characeae, 15, i73, 160-168 Characiaceae, 410 Characin, 181, 416 Characium (A. ^r.), 345- 412, 340 — ornithocephaluni (-\- ^''•\.^"*Yc7 Chares, 173- 182, 160-162, 1l4, 167, 168 Cheilanthes (Sw.), 85, 58 Chiloscj-phos (Cord.), 164 460 INDEX CHL Chlamydococcus (\. Br.), 186, 299, 300, 409, 417 — nivalis (A. Br.), 416 Chlamydomonas (Ehrb.), 1S6, 299, 300, 409, 417,419 — Morieri (Dang.), 300 — pulvisculus (Miill.), 300 Chlamj-dospore, 6, 339 Chlorochj-trium (Cohn), 284, 345, 410 Chlorococcum (Fr.), 417, 448, 347 — gigas (Griin.), 417, 347 Chlorogonium (Ehrb.), 300 Chlorophyceae, 305 Chlorophyllophyceae, 409 Chlororufin, 279 Chlorothecium (Brzi.), 411 Chlorotylium (Ktz.), 280 Choanephora (Cunn.), 340 Choiromj'css (Vitt.), 358 Chondria (Ag.), 209 Chondrioderma diffbrme (Rost.), 332 Chondrites (Sternb.), 304 Chondrus (Grev.), 208, 185 — cispiis (Stackh.), 210. 185 Chorda (Stackh.), 241, 2i6 — filum (Stackh.), 242, 216 — tomentosa (Lyngb.), 244 Chordaria (Ag.), 247, 220 — flagelliformis (Ag.). 220 Chordariacese, 190, 247 Chromatophore, 194, 410, 427, 444, 445 • Chromophyton (Wor.), 188, 257 Chroococcacea;, 409, 419, 427, 446, 455, 374-378 Chroococcus (Nag.), 417, 44i, 445i 446, 447, 448, 449, 374 ■ — turgidus (Nag.), 374 Chroodactylon (Hansg.), 446, 447 Chroolepidese, 187, 258, 273, 279, 247 Chroolepus (Ag.), 280, 284 — aureum (Ktz.), 280 — lolithus (Ag.), 2S0 — umbrinum (Ktz.), 280 Chroomonas Nordsedtii (Hansg.), 445 Chr\-sochytrium (Schroet.), 347 Chr^•somyxa (Ung.), 386 Chylocladia (Grev.), 208 Chytridiacege, 4, 250, 344, 352, 297 — (doubtful). 347 Chytridium (A. Br.), 4, 249, 346 Cilia (of peristome), 135, 147, 111 Cinclidium stygicum (Sw.), 120 Cingularia (Wei'^s), 12S, 100 — t\T)ica (Weiss), 100 Circinate vernation, 72, 51 Circinella (Van Tiegh.), 339 Cladochytrieae, 344, 345; 34^ C'adochytrium (Nowak.), 346, 352 Cladonia (Hill), 361, 279 — furcata(Hoffm. , 279 Cladophora (Ktz.), 275, 276, 330, 243 — gracilis (Ktz.), 243 Cladosporium herbarum (Lk.), 374 Cladostephus (Ag.), 249, 253 Clamp-connection, 306, 266 Clastidium (Kirchn.), 444 Clathrocystis (Henf.), 447 Clathrus'(Mich.), 398, 399 Clavarieae, 391 Claviceps(Tul.), 361, 375, 309-311 — purpurea (Tul.), 375, 309-311 Cleistocarp, 355, 356 Closterium (Nitzsch), 259, 268, 269, 330, 239, 241 — Dianze (Ehrb.), 239 — rostratum (Ehrb.), 241 COR Clover, 364 Club-moss, 61 Coccidium, 201 Coccocarpia molybdia (Pers.), 280 Coccogone, 444 Cocconema lanceolatum (Ehrb.), 357 Coccus, 450, 379, 381 Codiolum (A. Br.), 413, 342 — gregarium (A. Br.), 342 Codium (Stackh.), 289, 290 Coelastrum (Niig.), 186, 303, 265 — cubicum (Nag.), 265 Cceloblasta;, 186, 281 Coelospharium (Nae.), 447, 448, 378 — Kiitzingianum (Niig.), 378 Coemansia (Van Tiegh. and Le Men.), 341 Coenobe, 184, 186, 291, 29?, 259-265 Coenobieae, 186, 291, 412, 418, 419, 259-265 Coleochaetaceae, 188, 190, 219, 220, 199 Coleochaete (Brdb.), 189, 220, 199 — divergens (Brings.), 220 — pulvinata (A. Br.), 220, 199 — scutata (Breb.), 220 — soluta (Brings.), 220 Coleodesmium (Brzi.), 440 Collateral vascular bundles, 75, 89, 98 Collema (Ach.), 321, 322, 372, 385 307 — pulposum (Bernh.), 307 Collemaceae, 322, 359, 360, 361, 370, 372, 307 308 Collenchymatous tissue, 93 Colpodelia (Cienk.), 405 Columel, 29, 86, 135, 145, 165, 339, 351, 110, 112 _ Commissure, 92 Completoria complens (Lohde), 343 Compositae, 364 Concentric vascular bundles, 18, 75, 98, 109 Conceptacle, ir, 196, 199. 207, 232, 290, 182-184, 188, 208, 209 Conducting tissue, 138, 193 Conferva (L.), 185, 273, 274, 276 — bombycina (Ktz.), 273 Confer\'aceae. 18^, 187. 190, 259, 273, 277, 278, 242-244 Confervites (Sch.), 304 Confervoideae, 237 — Heterogamae, 185, 188, 219, 199-204 — Isogamae, 185, 186, 272, 242-247 'Conid,' 327, 436, 444 Conidiobolus utriculosus (Bref.), 343 Conidiospore, 325, 327, 309 Coniferae, 13, 310, 3 Conjugatae, 185, 187, 258, 233-241 Conjugation, 185 (see also under Algae, Fungi, and Schizophyceae), 198, 222, 233- 238, 241, 246, 247, 252, 293-297, 299 Conjugation-tube, 346, 297 ' Connubium,' 263 Consortism, 318 Continuity of protoplasm, 66, 76, 192, 194, 230, 240, 428, 440 Contractile protoplasm, 422 — (pulsating) vacuole, 257, 292, 300, 409, 415 Convolvulus, 364 Coprinus stercorarius (Fr.), 392, 318, 321 Copromyxa protea (ZopQ,- 406 ' Copulation,' 263 Cora(Fr.), 319 Corallina (L.), 189, 194. 206, 183, 184 — officinalis (L.), 206, 183 — rubens(L.), 184 Corallinaceae, 196, 199, 203. 206, 182-184 Coralline, 195, 206 Cordj-ceps (Fr.), 376 INDEX 461 COR Coremium (Lk.), 312 — glaucum (Lk.), 367 Cork, 98 Cormophytes, 135, 156, 173 Corn-mildew, 383 Corpusculum, 14, 3 Corsinia (Radd.), 160, 166 Cortex, 173, 174, 221, 247, 39 Cortical lacuna, 81 — tissue, 76, 228, 242. 249, 321, 216, 271, 311 Corticium (Pers.). 391 Coscinodiscus (Ehrb.), 420, 426 Cosmarium (Cord.), 268. 269, 270, 239 — coelatum (Ralfs), 239 Cotyledon, 17, 28, 41, 55, 71, 105, 8, 9, 14 Craterobpermum (A. Br.), 263 Cribrariese, 401 Cronartium (Pers.), 386 Crouania (Ag.), 204, 172 — attenuata (Ag.), 172 Crown, 179, 164, 166 Cruciate (tetraspores), 195 Crucibulum (Tul.), 307, 327, 328 — vulgare (lul.), 32?', 328 Cruciferae, 326, 327 Cruoria (Fr.), 191, 193, 210 Crustaceous Lichens, 321 Cryptogramme crispa (R. Br.), 72 Cr^-ptonemia (Ag.), 208 Cri"ptonemiaceae, 208 Crj-stalloid, 276, 288, 308 Ctenomyces (Eidam), 367 Cupule, 140, 157, 170, 155 Cupuliferse, 310 Cushion, 93, 115, 87 Cutleria (Grev.), 239, 241, 251, 26, 227 — adspersa (de Not.), 252 — multifida (Grev.), 252, 226, 227 Cutleriaceae, 187, 239, 251, 254, 226-229 Cyanocystis (Brzi.), 444 Cyanophycese, 408, 409, 426, 358-378 Cyanophycin, 428 Cyathea (Sm.), 85, 124, 59 Cyatheacea;, 71, 73, 78, 80, 81, 85, 123. 124, 57, 59 Cj'cadeae, 13, 1 Cyclomyces (Kze.), 392 Cyclopteris hibernica (Forbes), 121 Cyclosis, 175, 422, 163 Cylindrocapsa (Reinsch), 227, 414 Cylindrocapsacea;, 228 Cj'lindrospermum (Ralfs), 430, 433, 362 — • macrospermum (Ktz.), 362 CjTnbella (Ag.), 426 Cjinopolia (Lm.x.), 28S Cyst, 185, 258, 264, 272, 274, 278, 427, 429, 446 Cj'stid, 394, 321 Cystocarp, 201, 213,169-171, 173, 174,176-178, 183, 184, 188, 189, 191 Cystopteris (Bernh.), 69, 85, 58 — bulbifera (Bernh.), 81 — fragilis (Bernh.), 67 Cystopus (L6v.), 312, 323, 326, 327, 328, 335, 269, 275, 285, 28/ — candidus (L^v.), 326, 269, 285 — cubicus (L6v'.), 326 — Portulacae (L6v.), 275, 287 Cystosira (Ag.), 235 Dachyomyces (Xees ab Esenb.) Dansea (Sw.), 94, 95 Danaeites (Gopp.), 122 Dasya (Ag.), 196, 209, 174 — elegans (Agl), 174 389 ECT Dasycladaceze, 280, 281, 286, 251-255 Dasycladus (Ag.), 287, 288, 253 — clavseformis (Ag.), 253 DaYallia (.Sm.), 85 DaYallieae, 83 Delesseria(Grev.), 193, 208 Delesseriacea;, 208 Delphinium, 364 Derbesia (Sol.), 289 Dermocapsa (Crotian), 444 — violacea (Crouan), 444 Desiccation of spores, 315, 452 Desmarestia (Lmx.), 241 Desmidiaceae, 187, 190, 258, 259, 268, 239-241 • Desmidium (Ag.), 187, 268, 239, 241 — Swartzii (Ralfs), 239, 241 Desmids, movements of, 269 Diaphragm, 31, 39, 105, 124, 125, 179, 9, 14 Diatoma (DC.), 424, 357 — elongatum (Ag.), 357 Diatomacese, 187, 258, 408, 419, 353-357 Diatomin, 257, 421 Diatoms, movements of, 422 DiatrjTJe (Fr.), 373 Dichothri.x (Zanard.), 4^7 Dicksonia (L'H^rit.), 71, 84, 85, 42 — antarctica (Lab.), 42 Dicranum (Hedw.), 138, 149 Dictyonema (.Mont.), 319 Dictyopteris (Lm.\. , 254 Dictyosiphon (Grev.), 239, 241, 245 — hippuroides (Lj-ngb.), 247 Dictyosphaerium (Nag.), 412, 338 — reniforme (Buln.), 338 Dictyosteiium (Bref.), 405 Dictyota (Lm.x.), 254 Dictyotacese, 188, 237, 254, 230, 231 Dictyuchus (Leitg.), 334, 335 Didymium (Schrad.), 316, 333 — serpula (Fr.), 333 Dimargaris (Van Tiegh.), 341 Diplolepidae, 148 Diploxylous bundles, 117 Dipsacus, 364 Disc, 170, 184, 220 Discocarp, 355, 369 Discomycetes, 308, 319, 355, 356, 370 Dispira (Van Tiegh.), 341 Diverticula, 209, i87 Docidium (Br^b.), 268, 269, 239 — baculum(Br^b.), 239 Doodia (R. Br.), 85 Dothidea (Fr.), 354 Draparnaldia (Ag.), 273, 275, 276, 417, 244 — glomerata (Ag.), 244 Drilosiphon (Ktz.), 433, 438, 440 — Julianus (Ktz.), 440 Dry-rot, 309 Dudresnaya(Born.), 189, 202, 204, 179 — coccinea (Crouan), 179 Dulse, 210 Dumontia (Lmx.), 208 Dumontiera (Nees ab Esenb.), 171 Durisa (Bor.), 166 Durvillaea (Bor^), 188, 228, 230, 235, 236 Dutch rushes, 113 Dwarf male, 225, 201, 202 EcKLONiA (Horn.), 244 Ectocarpaceffi, 187, 239, 247, 212, 221, 222 Ectocarpu-s (Lyngb.), 187, 239, 241, 247, 221. 222 — .investiens (Hauck), 221 — pusillus (GrifT.), 249 46: INDEX F.CT Kctocarpus siliculosiis (Kt/.), 249, 222 Edi))Ie earths, 424 E'achista (Duhy). 247 Klaphomyceai, 358 Elaphomvces (Nees ab Esenb.), 357> 358. 359> 367 Elater, 102, iii, 128, 134, 159, 163, 171, 84, 85, 158, 159 Elk's-horn-fern, 72 Embryo, 11, 13, 17, 27, 40, 56, 105, 134, igo, 271,21,45,158 Embrj-o-sac, 14, 3 EmbrAonic vesicle, 11. 14. 3 Emericella (Berk.), 310 Empu?a ^Cohn), 342, 343 — (Irylli (Fres.), 343 — Muscas (Cohn), 343 Encalypta (Schreb.), 149 Encalj'pteje, 148 Encysted condition, 415 Endoclonium (Franke), 284 Endoderm, 76, 109 Endogenous spore, 424, 451, 379-381 Endophyllum (L^v.), 386 Endophytic Alga;, 222 — Fungi, 317 Endosperm, 15, 39, 20 Endosphjera(Klebs), 284, 410 Endospore, 20. 47, 74, 80, 112, 134, 145, 160, 17 Endosporous Bacteria, 451, 452, 455 Endostome. 147 Endothecium, 145 Enteromorpha (lA-.), 217, 218, 219, 197 — intestinalis (Lk.), 197 Enterosora (Baker), 79 Entomophthora(Fres.). 342, 343 — curvispora (Nowak.), 342 — ovispora (Nowak.), 342 — ■ radicans (Bref.), 342 Entomophthorea;, 4, 342 Entyloma(de By.), 350, 351, 352 Envelope of plasmode, 403 Envelope-tissue, 355, 360, -361, 363, 364, 366, 368, 370, 373) 374: 378, 384) 303-305 Ephebe pubescens (Fr.), 281 Ephedra, 113 Ephemerum (Hampe), 150, 121 • — serratum (Hampe), 121 Epichloe (Fr.). 361. 376 Epiderm, 39, 54, 153-155 Epidermal tissue, 10, 138, 193, 242, 216 Epiphragm, 146, 397, 112, 117, 327 Epiphytic Algae, 237, 239, 248, 257. 444, 184, 221 — Fungi, 317 Epiplasm, 354 Epispore, 20, 22, 25, 36, 47, 14, 16 Epithemia (Br^b.), 426 Equiseta crj-ptopora, 107 — phaneropora, 107 Equisetaceae, 19, 20, 100, 124, 2, 77-86, 96-101 Equisetites(Sch.), 124 — arenaceus (Brongn.), 124 Equisetum (L.), 102, 124, 2, 77-86 — arvense (L.), 106, 107, 109, no, 78, 79 — giganteum (L.), 113 — hyemale (L.), no, 113, 82 — limosum (L.), 109, in, 86 — littorale (KuhL), 109 — maximum (Lam.), no, 78, 81, 83 — palustre [L.), no — pratense (Ehrh.), no X- sylvaticum (L.), 77, 80 Eremascus (Eid.), 378, 302 — albus (Eid.), 359, 361. 302 Eremobise, 186, 410, 336-344 FON Ercmospha;ra (de By.), 417 Ergot, 376, 309-311 Erysiphe (Hedw.), 317, 362, 363, 367, 378 - communis (Lk.), 364 — graminis (Ldv.), 364 — lamprocarpa (Lk.), 364 — iSL'irtii (L6v.), 364 — (Uncinula) spiralis (Berk. & Curt.), 364 Erysipheae, 309, 359, 360, 362, 364, 365, 378, 303 Essential air-cavity, 106 Euastrum (Ehrb.), 268, 239, 241 — pectinatum (Br^b.), 241 — rostratum (Ralfs), 239 Eucheuma spinosum (Ag.), 210 Eudorina (Ehrb.), 255 F^uglena, 345, 410, 449, 297 Eunotia (Ehrb.), 424, 357 — monodon (Ehrb.), 357 Eurotium(Lk.), 359, 360, 364, 367, 378, 275,304 — herbariorum (Lk.), 366, 275, 304 — repens (de By.), 304 Eutypa (Tub), 373 Eusynchytrium (Schroet.), 347 Exciple, 355, 372. 308 Exidia(Fr.), 389,' 317 — spiculosa (Sommerf.), 317 Exoascus (Fckl.), 379 — alnitorquus (Sad.), 380 — aureus (Sad.), 380 — deformans (Fckl.), 379 — Pruni (Fckl.), 379 Exobasidium (Woron.), 389, 390 — Vaccinii (Woron.), 388 Exospore. 20, 47, 74, 80, 112, 134, 14^, 160, 17, 20, 42 Extine, 166, 325, 337. 340, 347, 349, 351 Facultative parasites, 317, 454 • — saprophytes, 317 False stomate, 107 Favella, 204. 181 Fegatella (Radd.), 168, 170, 171, 152 — conica (Cord.), 152 Female conceptacle, 232, 209 — filament, 266 — inflorescence, 151, 156 — prothallium, 15, 102, 103, 4, 79, 80 Ferment, 316. 380, 454 Ferns, 64, ng, 42-76, 92-95 Fertilising-tube, 202, 211, 179 Filament, 184, 428 Filamentous Lichens, 284 Filices, 15, 16, 17, 19, 20. 21, 64, 119, 42-71, 92-95 Filmy ferns, 71, 72, 88, 62-64 Fimbriaria (Xees ab Esenb.), 171 Fischera (Schw.), 439, 441 Fissidens (Hedw.), 137, 149 Fission, 185, 270, 240 Flagellate Infusoria, 410, 416, 455, 456 Float-corpuscle, 31 Floating apparatus, 31 Florideae, 185, 188, 191, 444, 169-198 Florideae-green, 194 ' Flos-aqua;,' 436 Flower, 134, 139, 141, 154, 104, 106, 129 ' Flowering fern,' 73, 90, 66, 67 ' Flowers of tan,' 403 Foliaceous Lichens, 321 Foliose Hepatica;. 135, 156, 160, 132-134, 137- 142 Fontinalis (L.), 145, 149, 111 — antipyretica (L.), Ill INDEX 46: FOO Foot, 17, 41, 71, 105, 144, 146, 154, 422, 14, 131 Fossil Cn^ptogams, 114, 172, 183, 303, 330, 424, 87-101 Fossombronia (Radd.), 156, 164, 135 — pusilla (Nees ab Esenb.), 135 Fovea, 50 Foveola, 51 Fragillaria (Lyngb.), 426 Fragmentation of nucleus, 176 Frond, 72, 191, 228, 239, 241, 242, 430, 432, 359 Frondose Hepaticse, 135, 156, 135, 136, 143-159 Front view (diatoms), 420. 353, 354 Fructification, 102, no, 5, 6, 77, 94, 96, 100, 101 Fruit, 180 Frullania(Radd.), 164, 139, 140 — dilatata (Nees ab Esenb.), 139 — Tamarisci (Dum.), 139 Frustule, 268, 419, 423, 353-355 Frustulia saxonica (Ag.), 355 Fruticose Lichens, 321, 283 Fucacese, 185, 188, 190, 228, 304, 444, 205-211 Fucoideae, 235, 237 Fuco.xanthin, 230 Fucus (L.), 188. 235, 304, 207-210 ' — amylaceus,' 210 — furcatus (Ag.), 228 — serratus (L.), 235, 207 — vesiculosus (L.), 232, 235, 236, 207-210 Fuligo varians (Somm.), 403 Funaria (L.), 140, 103, 106. 108-110 — hygrometrica'(L.), 103, 106, 108-110 Fundamental tissue, 10, 76, 39, 53, 54 Fungi, 3, 4, 305, 266-331 — cell-contents, 307 ■ — cell-membrane, 308 — differentiation of thallus, 309 — histological characteristics. 306 — luminosity, 316 — nutrition, 316 — spores, 312 conditions of germination, 314 — conditions of vegetation, 316 Fungus-cellulose, 308 Funiculus, 328 Funnel, 31, 36, 15 Furrow, 100, 106, 124, 129, 420, 353 Galaxaura (Lmx.), 211 Galls, 284, 347 Gametange, 272, 277, 279, 296, 349, 411, 246, 247, 260, 298 Gamete, 259, 335, 337, 338, 340, 346, 349, 350, 351, 293, 298, 299 Gasteromycetes, 309, 388, 395, 324-331 Gasteromycetous Lichen, 319 Gautieria (Vitt.), 395 Geaster (Mich.), 396 Gelatine, 190, 210 Gelatinous Lichens, 321 Gelidiaceae, 209 Gelidium (Lmx.), 209, 210 Geminella (Schroet.), 350 Gemma, 61, 86, 133, 140, 157, 170, 185, 196, 208, 219, 250, 105, 114 Genabea (Tub), 357, 358 Genea (Vitt.), 358 General bundle-sheath, 109 Genuflexion, 265 Geocalyceae, 162 Geocalyx (Nees ab Esenb.), 164 Germ-cell, 179 Germ-filament, 20 Germ-tube, 314, 325, 326, 327, 328, 329, 333, 351, 352, 373t 385, 389, 390, 293, 299 HAL Gigartina(Lmx.), 208, 169 — mamillosa (Ag.), 169 - GigartinacejE, 203, 208, 169, 185 Gills, 393, 319-321 Giraudia(D. & S.), 239, 247, 212 — spha<.elarioides (D. & S.), 249, 212 Girdle, 420, 353, 354 Girdle-band, 268 Girdle-view (diatoms), 420, 354 Gland, 76, 67 Glaucocystis (Itzig.), 410 Glebe, 395, 397, 398, :t99, 325, 329-331 Gleichema (.Sw.), 77, 85, 60 Gleicheniaceae, 85, 60 Glochid, 30, 13 Glochiococcus (Lagerh.), 417, 346 — anglicus (Benn.), 346 GlcEocapsa (Ktz.), 417, 440, 446, 447, 448, 449, — fenestralis (Ktz.), 440 Gloeochaete (Lagerh.), 447 Glceocystis (Nag.), 300, 417, 419, 448 Glceothece (Nag.), 447, 376 — granosa (Rabh.), 376 Gloeotrichia (Ag.), 436 — natans (Thur.), 435 — punctulata (Thur.), 436 Glomerule, 213 Glossopode, 50 Glycogen, 308, 355, 357 Gomphonema (Ag.), 424, 354, 356 — constrictum (Ehrb.), 354b, 356 Gonatonema (Wittr.), 261, 263 — notabile (Wittr.), 263 Gonatozygon (de By.), 271 Gongrosira (Ktz.), 284 — de Baryana (Rabenh.), 280 ^'^'/ii'^'^^t' 77:'/°^' "^^°" '^^^' '*^"^' ^^37' '^^^' •*^^' o4i, o4»j, o44 Gonium (Miill.), 186, 299, 302 Gonoplasm. 325, 328 Gottschea appendiculata (Nees ab Esenb.). 133 Gracilaria ,Grev.), 199, 201, 208, 178, 187 — compressa (Ag.), 178 — confervoides ((irev.), 209, 187 — lichenoides (L.), 210 Graphiola (Port.), 350 Grasses, 350, 364, 376, 385 Grateloupia (-A.g.), 208 Griffithsia (Ag.), 199, 204 Grimmia (Ehrh.), 149 Gulf-weed, 232, 236, 211 Gum-cell, 58. 76, 123 Guttulina (Cienk.), 405, 406 — protea (Faj-.), 406 Gymnoascus (Baranet.), 359, 360, 361, 367, 368, 369, 37°) 378 Gymnocarpous Lichens, 356 Gj-mnogramme (Desv.), 16, 67, 83, 85, 58 — leptophylla (Desv.), 65 Gymnomitrium (Nees ab Esenb.), 164 Gymnopodal shoot, 176 Gymnosperms, 12, 13, 14, 15, 52, 1, 3 Gymnosporangium (DC), 386 Gymnostomous, 135, 147 Gyrolith, 183 Hadrome, 19 Haematococcus (Ag.), 416 — Butschlii (Blockm), 417 Halidrys (Grev.), 232, 235, 206 — siliquosa (Lyngb.), 206 Halimeda (Lmx.). 289, 258 — Tuna (Lmx.), 258 464 INDEX HAL Halosphxra (Schm.). 41 ir 337 — viridis (Schm.), 337 Halymenia (Ag.), 208 Hapalocystis mirabilis (Sorok.), ^47 Hapalosiphon (Niig.), 430, 441, 36/ — byssoideus (Kirchn.), 367 Haplotnitrium (Nees ab Esenb.), 156, 161 Haplospora (Kjellm.), 249 Hard hern, 72 Hauckia (Brzi), 413 Haustoriiim. 309, 323, 326, 340, 350, 362, 378, 269, 285, 296 Hawlea Miltoni (Stur), 94 Hedwigia (Ehrh.), 149 Helicostylum (Cord.), 3^9 Helminthocladia (Ag.), 211 Helminthocladiaceas, 189, 211, 175, 189-191 Helminthostachys (Kaulf.), 98, 99, 100 Helvella esculenta (Pers.), 278 Hepaticae, 135, 156, 132-159 Heracleum sphondylium, 348 Hermonitis (L.), 85 Heterocyst, 427, 430, 431, 434, 438, 359, 362 Heteroecism, 383 Heteromerousthallus, 320 Heterophyadic Equisetaceae, 113 Heterosporous Vascular CrjptogamS; 13, 15. 20, 21,5-33 Hibernating spores (Fungi), 315 Hibiscus, 340 Hildenbrandtia (Nard.), 190, 191, 193, 210, 211, 188 — protot^-pus (Nard.); 188 — rivularis (Ag.), 211 Himanthalia (Lyngb.), 228, 232, 235, 205 — lorea(Lyngb.), 2105 Homoiomerous thallus, 321 Homophyadic Equisetaceae, 113 'Honey-dew,' 376 Hookeria(Sm.), 149 Hoop, 420 Hops, 364 Hormactis (Thur.), 436 Hormidium (Ktz.), 279 Hormiscia (Aresch.), 277 Hormogone, 427, 429, 431, 435, 438, 442, 445 Hormospora (Br^b.). 414. 344 — mutabilis (Br^b.),' 344 Horse-tails, 100, 113, 124 House-fly, 343, 378 Hyaline hair, 226, 275, 433, 199 Hyaloplasm, 403 Hyalftheca'(Ehrb.), 187, 268 Hybridism, 145, 235 Hydneae, 393 Hydnobohtes (Tul.), 357, 358 Hydnocystis (Tub), 358 Hydnolria (B. and Br.), 358 Hydnum (L ), 392 Hydrianum (Rabh.), 413 Hydroclathrus (Bory), 245 Hydroc^'tium (A. Br.), 413 Hydrocictyeae, 277, 291, 296, 409 260 Hj-drodictj'on (Roth), 186, 296, 410, 413, 260 ^ utriculatum (Roth), 260 Hydrolapathum (Rupr.), 193, 196, 208, 71 — sanguineum (Stackh.), 171 Hydropteridea;, 21 Hydrurus (Ag.), 188, 190, 256, 257, 232 — penicillatus (Ag.), 232 Hygroscopic properties, 171 Hymenium, 355, 357, 368, 373, 376, 384, 386, 389, 391, 393, 394, 395, 396, 276, 300, 301, 305, 317, 322 Hymenogaster C^^itt.), 395 KIE Hynienogastrea;, 395, 396, 398 Hymenomycetes,'^388, 395, 266, 270, 273,319- 323 Hymenophallus (Neesab Esenb.), 398 Hymenophyllaceae, 16, 17, 18, 19, 64, 66, 67, 70, 71, 73, 76,80, 81, 86, 121, 122, 61-64, 93 Hymenophyllum (L.), 86, 87, 88, 62-64 — tunbridgense (Sm.), 62 Hypertrophy, 324, 326, 327 Hypha, 228, 306, 208-210. 267, 273, 281, 282, 285, 300, 307, 308, 317, 322 Hj-pnea (Lmx.), 209 Hypneaceae, 208 Hypnosperm, 225, 227, 266, 283, 295, 296 Hypnosporange, 285 Hypnospore, 262, 281, 284, 300 Hj'pnum (IMll.), 149 — populeum (S\v.), 113, 118 Hj-pochnus (Fr.), 389, 266 — centrifugus (Tub), 266 Hypocopra (Fckl.), 361 Hypcdermal tissue, 107 Hypothece, 355, 360, 361, 370, 308 Hj-poxylon (Bull.), 373 Hysterineae, 356 Ileodictvox (Tub), 398 Impotent antherid<, 332 Impregnating tube, 324, 332, 286 Inactis (Ktz.), 441, 444 Indusium, 24. 29, 50. 73. 79, 86, 121, 19, 32, 59, 63, 93 ' Inflorescence, 134, 158. 170, 104. 106, 109, 131, 150, 151, 156, 157 Infusoria, agents in fertilisation, 199 Innovation, 85, 133, 139, 151, 157 Intercalary- growth, 241 — surface-growth, 222, 200 Internode, 102, 174, 81, 165, 168 Intine, 325, 337, 339, 349, 351 Involucre, 85, 94. no, 159, 165, T71, 59 Involution-forms (Bacteria), 451 Iodine, 190, 236, 244 ' Irish moss,' 210 Isactis (Thur.), 436, 365 — plana (Thur.), 365 Isinglass, 210 Isocystis (-Brzi.), 432 Isoeteae, 21, 47, 119, 28-33 Isoetes(L.), 19, 38, 47, 52, 119, 28-33 — lacustris (L.), 28-33 Isoetites (Schmp.), 119 Isogamous reproduction, 272 ' Isospore,' 285 Isosporous Vascular Cryptogams, 12, 15, 20, oo. 34-85 Isthmus, 270 Japaxese isinglass, 210 Jungermannia (L.), 164, 132, 138, 142 — barbata (Schreb ), 138 — bicuspidata (L.), 142 — nemorosa (L.), 132 Jungermanniaceae, 159, 160, 172, 132-142 KALLYiMENI.A (Ag.), 2o8 Kaulfussia (Bl.), 78, 92, 93, 94, 95 Kelp, 190, 236, 244 Kickxella (Coem.), 341 Kieselguhr, 424 INDEX 465 LAB Lap.iat.-e, 364 Labium, 51 Laboulbenia flagellata (Peyr.), 312 Laboulbenieae, 37S, 312 Lactarius (Fr.X 394 Lacuna, 105, 81 Lagenidium (Schenk), 330, 331 Lamella, 393, 394, 153, 273, 319-321 Lamina, 50. 230, 242 Laminaria (Lmx.), 239, 304, 215 — digitata (Lmx.)? 244 — saccharina (Lmx.), 215 Laminariacea;, lOo, 230, 236, 239, 241, 242, 304, 213-217 Lamprothamnus (A. Br.), 182 ■ — alopecuroides (A. Br.), 176 Lastrea (Presl), 85 Lateral conjugation, 260, 265, 235, 238 Lathyrus, 364 Laticiferous hypha;, 394 Laudatea (Johovv), 319 Laurencia (Lmx.), 209 Laver, green, 219 — purple, 217 Leaf-sheath, 102, 105, 124, 81, 83 Leathesia (Gray), 241 Leiodermaria (Ren.), 117, 89 Leiodermarieae, 117, 89 Lejeunia (G. & L.), 164 Lejolisia (Bom.), 201, 209, 177 — mediterranea (Born.), 177 Lemanea (Bory), 191, 196, 214, 192 — fluviatilis (Ag.), 216 — nodosa (Ktz.), 192 Lemaneaceae, 189, 195, 214, 192 Lemna, 432 Lenticel. 93 Lepidodendreae, 115, 87, 88 Lepidodendron (Sternb.), 115, 87, 88 Lepidophloios (Sternb.), 116 Lepidophyllum (Brongn.), 88 Lepidostrobus (Brongn.), 115, 116, 88 — Brownii (Schmp.), 116, 88 — dabadianus (Schmp.), 116 • — ornatus (Hook.), 88 Lepido2ia (Dum.), 164 Leptochaete (Brzi.), 436 Leptochrysomvxa (de By.). 386 — Abietis (Ung.), 386 Leptogium microphyllum (Ach.), 307, 308 Leptome, 19 Leptophloem, 146 Leptopuccinia Dianthi (Schroet), 386 — iNIalvacearum (Schroet.), 386 Leptopuccinieae, 386 Leptosira (Brzi.), 280 Leptothrix (Ktz.), 4, 440, 445, 451 — muralis (Ktz.), 440 — parasitica (Ktz.), 440 Leptoxylem, 146 Lessonia (Borj-), 244, 214 — fuscescens (Bor^-), 214 Leucobrj-um (Hampe), 138, 139, 149 Leucochytrium (Schroet.), 347 Leucodon (Schw.), 149 Leuconostoc (Van Tiegh.), 433, 455 Liagora (Lmx.), 194, 211 Lichen-fungi, 317, 318, 361 Lichens, 222, 279, 318, 356, 419, 441, 448, 449, 279-284, 307, 308 — discocarpous, 370 — gymnocarpous, 356 Licmophora (-Ag.), 426 Lid-cell, 17, 158 Ligulatae, 38, 44 MAS Ligule, 38, 44, 51, 31, 32 Lmdsaya (Dr>'.), 85, 58 Lip-cell, 79, 55 Lithoderma (Aresch.). 190, 251, 225 — fatiscens (Aresch.), 225 Lithophyllum (Phil.), 206 Lithothamnion (Phil.), 206 Liverworts, 135, 156, i6o Lobospira (Thur.), 254 Lomaria(\Villd.), 83, 85 — spicant (Desv ), 72 Lomentaria (Gaill.), 209 Lomentariacese, 209 Lophoclea (Dum.), 164 Loxsoma (R. Br.), 86, 87, 121 Lucern, 364 Luminosity of fungi, 316 Lunularia (Mich.), 157, 170, 171 Lupins, 364 Lychnothamnus (Leon.), 182 — stelliger (A. Br.), 176 Lycoperdacese, 395, 396, 398, 399 Lycoperdon (Tourn.), 308, 395 Lj-copodiaceap, 11, 15, 16, 18, 19, 53, 34-41 Lycopodieae, 53, 118, 34-39 Lycopodites (Brongn.), 118 — Stockii (Kidst.), it8 Lj-copodium (L.), 19, 20, 53, 56, 61, 34-37, 39 — albidum (Bak.), 59 — annotinum (L.), 54, 34, 39 — cemuum (L.), 54, 61, 35 — clavatum (L.), 56, 61, 37 — inundatum (L.), 53 — Phlegmaria (L.), 55, 118, 36 Lj-godium (S\v.). 71, 77, 90, 91, 69 — palmatum (S\v.), 69 Lj-ngbya (-^g.), 441. 444.- 44 5, 449. 371 — aestuarii (Liebm.), 371 — antliaria (Hansg.), 445 Lyngbyeae, 441, 445 :Macrocystis (Ag.), 239, 240, 244, 213, 217 — pyrifera (Ag.),^213, 217 '' Macrosporange,' 7 ' Macrospore,' 7 Macrosporium Sarcinula (Berk.), 374 ' Macrozoospore,' 7 Madotheca (Dum.), 157, 164 Male conceptacle, 233, 208 ' — fern,' 72 — filament, 266 — inflorescence, 104, 150, 152, 157 — prothallium, 15, 103, 78 ^Mantle-cells, 36, 80, 99, 104 Manubrium, 175, 177, 163 Marattia (Sm.), 91, 94, 95, 70, 71 — cicutaefolia (Kaulf.), 93, 95 Marattiaceae, 20, 21, 64, 65, 74, 77, 78, 79, 81, 91, 121, 122, 70, 71, 94 Marchantia (L.), 157, 170, 171, 149 151, 153- 159 — pol>-morpha (L.), 157, 149-151, 153-159 Marchantiaceae, 133, 157, 160, 167, 149-159 Marchesettia spongioides (Hauck), 210 Marsilea (L.), 33, 37. 114, 4, 6, 14, 15, 17, 19 — Drummondii (R. Br.), 38 — quadrifolia (L.), 34, 6 — salvatrix (L.), 14, 15, 17, 19 Marsileacese, 12, 13. 25, 31, 4-6, 14-19 Marsilidium (Schenk), 114 Martensella (Coem.), 341 Massaria (De Not.), 356 IMassula, 25, 30, 13 Mastigobrj'um (Xees ab Esenb.), 164 H H 466 INDEX MAS Mastigocladus (Cohn), 439, 441 Mastigocoleus (Lagerh.), 439, 440, 441 Mastogloia (Thw.), 424, 426 Maza;a (Born.), 440 Mechanical system, 138, 171 'Medulla,' 118, 124,280 Medullary system, 76, 228, 242, 249, 321. 271 Megasporange, 7, 11, 22, 277, 7, 18, 19, 26, 27 Megaspore. 7. 11, 15, 20, 22. 118, 155, 7-9, 14- 16, 18, 20. 29, 125 Megazoosporange. 260 Megazoospore, 7, 218, 273, 296, 410, 196, 260 Meiampsora populina (J acq.), 386 Melanospermeje, 235, 237 Melanospora (Cord.), 359, 360, 370 Melobesia (Lmx.), 193, 194, 196, 206, 182, 184 — membranacea (Lmx.), 182 — Thureti (Born.), 184 jNIelobesiacese, 191 Melosira (Ag.), 424 Meridion (Leibl.), 426, 357 — constrictum (Ralfs), 357 Merismopedia (Mey.), 418, 446, 447, 448 ]Merispore. 6 Mercensia(Willd.), 77, 85 Merulius lacrymans (Fr.), 309 Mesocarpaceae. 187, 258, 259, 260, 233-235 Mesocarpus (Hass.), 260, 262, 263, 330, 233, 235 — neaumensis (Benn.), 261 — par\-ulus (Hass.). 233 — pleurocarpus (de By.), 235 3Iesogloeaceae, 239, 247, 220 Metzgeria (Cord.), 164 ^leum athamanticum, 348 Alicrandres. 22=;, 201. 202 Micrasterias(Ag.), 268, 239 — rotata (Grev.), 239 Microchaete (Thur.), 436 — diplosiphon (Gom ), 434 Micrococcus (Cohn), 450, 379 Microcoleus (Desm.), 429, 441, 444 !Microcyst, 404 INIicrocystis (Ktz.), 446. 447, 449, 377 — marginata (Meneg.), 377 Microspora (Thur.). 276, 242 — floccosa (Thur.), 242 Microsporange. 7. 11. 22, 277, 7, 11. 18. 19, 26, 32,33 Microspore, 7, 11, 12, 20, 22, 40, 115, 116, 155, 7, 11, 18, 20, 30, 125 ISIicrothamnion (Nag.), 280 Microzoospore, 218, 277, 410 Mildew of corn, 383 Mischococcus (Nag.), 412, 339 — confer\'icola (Nag.), 339 Mitremyces (Nees ab Esenb.), 399 jMnium (L.), 138, 140, 149 jSIohria (Sw.), 90, 91 Monadopsis (Klein), 405 Monas amyli (Cienk.), 405 Monoblepharidese. 331, 290 Monoblepharis (Cornu), 4, 331, 290 — sphaerica (Cornu). 290 Monoclea (Hook.). 164, 143 — Forsteri (Hook.), 143 Monocleaceae, 164, 143 Monosiphonous, 192, 195 ^lonospora (Sol.), 196 Monostroma (Thur.). 217, 218, 219, 198 — bullosum (Thur.), 198 Moonwort. 100 Morchella (Dill.), 356 Mortierella (Coem.), 338, 339 — nigrescens (Van Tiegh.), 338 — Eostafinskii (Bref.), 338 xos Messes, 135, 145 Mougeotia (de By.), 262, 264, 267, 330 - calcarea (W'ittr.), 262 Moulds, 366 Mucilage, 69, 220, 221, 238, 256, 257, 263. 269, 283. 298, 398, 248, 330 Mucilage-cell, 58, 76, 89, 92, 168, 67, 154 Mucilaginous sheath, 259, 267, 268, 274, 298, 428, 430, 434, 437, 440, 441 Mucor (Mich.), 4, 307, 339, 340, 350, 381, 293, 296 — INIucedo (L.), 293, 296 — racemosus (Fres.), 339 — tenuis (Lk.), 338 Mucorea;, 337, 339, 340 Muccrini, 4, 308, 315, 316, 335, 341, 342, 344, 345: 377. 378, 29^296 ]\Iulti!ocular zoosporange, 187, 237. 212. 227 Multinucleatse, 186. 280, 248-258 Musci, 135, 136, 102-131 Muscinea;, 2, 132, 102-159 IMushroom, 311, 320 Mutinus caninus (Fr.), 308, 329 Mycele, 309, 337, 363, 366, 369, 375, 389, 275,^ i^93, 296, 303-305, 318, 330 Mycetozoa, 305, 401, 456, 332-335 — doubtful, 405 Mj-coidea (Cunn.), 222 — parasitica (Cunn.), 222 IMycorhiza, 310 Mylitta(Fr.), 309 iNIyrionema (Grev.), 241 ]\Iyxomycetes, 401, 406, 332-335 Myzocytium (Schenk), 330 Nardoo, 38 Xavicula (Bory), 420, 422, 424, 357 — rhomboides (Ehrb.), 357 Neck, 16, 26, 39, 86. 68, 143, 179, 109, 148, 158 Neck-canal-cell, 16, 27. 39, 69, 159, 10 Neck-cell, 26, 68, 10 Neckera (Hedw.), 149 Nectria cinnabarina (Fr.), 267 Nemaliese, 192, 195, 199, 211, 175 Nemalion (Ag.), 211, 213, 175 — -.multifidum (Ag.), 175 Nemastoma (Ag.). 208 Nemathece, 196, 199, 202 Nematodonteae, 148 Nematophycus (Carruth.), 304 Neomeris (Lmx.). 287. 254 — Kelleri (Cram.), 287, 254 Nephrocytium (Nag.). 414. 343 — Nagelii (Griin), 343 Nephrodium (Rich.), 85 Nephrolepis (Sch.), 77, 85 Nereocystis (Post.), 240, 242, 244 Neutral zone, 175, 163 Nidularieae, 397, 327. 328 Nitella (Ag.), 175. 176, 179, 182, 163, 165, 166 - flexilis (Ag.), 163, 165, 166 Nitellea;, 173, 182, 163, 165, 166 Nitophj'ilum (Grev.), 196, 208, 173 — punctatum (Harv.), 173 Nitzschia (Hass.), 426 Node, 102, 173, 421, 165, 168 Nodularia (Mert.), 430, 433 Nodule, 421 Nostoc (Vauch.), 28, 165, 171, 429, 430, 431, 432, 433, 358, 359 — commune (L.), 358 — hyalinum (Benn.), 359 — muscorum (Ag.), 431 — parietinum (Rabenh.), 440 INDEX 467 NOS Nostocacea, i£5, 427, 428, 43°, 455, 456, 358-362 Nostochinese, 186, 427. 428, 5t)»-6/>5 Nothoclasna (R. Br.), 85 Xotommata, 284 . „ „„ Nuclei, plurality of, iSb, 187, 188, 194, 272, 273, 281, 284 Nuclearia(Cienk.), 405 Nullipore, 206 Nummularia (Tul.), 373 Obelidium (Nowak.), 3)6 _ Octaviana asterosperma (\ itt.), >5^4 ' Octospore,' 217 onn_9n? CEdogomaceap 188, 220, 222, 2(X)-20^ CEdogonium (Lk.), 222, 223, 226, 20U, i99. 216, 219, 193-195 . Porphyridium cruentum (^ag.;, 410 Potato-disease, 328 Pottia (Ehrh.), i47, i49 Prasiola (Ag.), 217, 219 Preissia(Cord.), 169, 170, 171 Primary node, 180 — root, 180, 168 Procarp, i98,_ 199, 213, 176, 187, 192 'Proembryo,' 177, 180 'Proembryonic branch," 176 Progametange, 349, 298 Prolific cells, 276 m/i 171 Prolification, 69, 139, 142, 196, 289, iU4, la Promycele, 325, 328, 329, 337, 338, 350, 35I' 352, 362, 373, 385, 386, 391, 299, 314 Propagation, 8 Propagule, 196, 237, 250, 289, 5«5t)-JO^ Protococcus (Ag.), 186, 285, 409, 417, 448, d.i'd, 345 — pluvialis (Ktz.), 345 Protomyces (Ung.), 4, 350, 352, 298 — macrosporus (Ung.), 348, ii98 Protomycetaceas, 348, 298 Protomyxa (Haeck.), 405 Protoneme, 133, 135, 136, 140, 214, 449, J-U->, 121, 125 Protophloem, 59 „, ^ -,-.. ,00 Protophyta. 2, 3. 4, 186, 276, 407, ^i^b-^o-i Protosalvinia (Daws.), 115 Protozoa, 456 Prozoosporange, 346, 297 Prunus, 364, 373 Psaronieae, 124 Psaronius (Cord.), 124, 95 Pseudo-bulbil, 70 Pseudo-cortex, 192, 212 Pseudocyst, 410, 427, 437, 441, 44^ Pseudo-parenchyme, 249, 251, 307, 350, 350, 360, 366, 372, 384, 267 Pseudopode, 151, 154, 402, 403, 422, 443, J-^-^, 332 Pseudo-ramulus, 434, 438, 364, 366 Pseudospora (Cienk.), 405 Psilophyton (Daws.), 119 Psilotea;, 21, 53, 61, 119, 40, 41 ^ ^ .^ Psilotum (Sw.), 17, 18, 19, 20, 53, 61, 63, 4U — triquetrum (Sw.), 61, 40 Pteris (L.), 85, 46, 47, 54, 58 — aquilina (L.), 75, 76, 77, 82, 54 — serrulata (L. fil.), 69, 46, 47 Ptilophyton (Daws.), 118 Ptilota (Ag.), 194, 204 Puccinia (Pers.), 383, 385, 3S6 — coronata (Cord.), 314 — graminis (Pers.), 383. 274, 314, 315 — straminis (Fckl.), 314 Puff-ball, 311, 396 Pulvinus, 93 RHI Punctaria(Grev.), 187, 241, 245 Punctariaceae, 239, 245 Pycnid, 362, 374 Pycnochytnum (de By.), 347 Pycnophycus (Ktz.), 235 Pycnospore, 362, 374, 375 Pyrenocarp, 355 Pyrenomycetes, 319, 355, 356, 370 Pyronema(Fckl.), 356, 359, 360, 361, 3^9, 370. 372, 378, 276, 306 — coAfluens (Tub), 276, 306 Pythium (Pringsh.), 317, 324, 329^ 33°, 33i, 332, 335, 286 — Chlorococci (Lohde), 329 — circumdans (Lohde), 329 — de Baryanum (Hesse), 329 — entophytum (Pringsh.), 329 — Equiseti (Sad.), 329 — gracile (Schenk), 329, 286 — intermedium (de By.), 329 — proliferum (de By.), 329 — vexans (de By.), 325, 329,377 QUATERXARIA (Tul.), 373 Radiolarians, yellow cells of, 318 Radula (Dum.), 162, 164, 137, 14i — complanata (Dum.), 13 /, 14i Ralfsia (Berk.), 241, 251 Ralfsiacea;, 239, 251, 225 Ramentum, 72 Ranunculus, 364 Raphe, 421, 353 Raphidium (Ktz.), 418, .5t)i — falcatum (Ktz.), 351 Reboulia (Radd.), 171 i/iq 1^1 1^4 156 Receptacle, 80, 170, 232, 246, 149-lol, 104, iOO, 157, 205, 207, 2i9 Receptive spot, 69, 227 ' Red snow,' 416 Rejuvenescence, 223, 274, 281 Renaultia (Stur), 122 Reproduction, 8 Reser%-e-system, 139 Resting-cell, 213, 264, 335, 339, 34°, 347 Resting-sporanue, 333 , o a. oR- oc^^ Restini-spore, 223, 258, 276, 278, 281, 28 29S, 315, 344, 345, 350, 351, 352,410,42/, 4.0, 436, 261, 361, 36;i Resting-swarm-cell, 274 Resting-zoosporange, 346 Retrogression, 4, 407, 449 Rhabdonema (Ktz.), 423, +^4 gg Rhacophyllum adnascens (L. 6c H.;, i-o, x^c. Rhipidonema (Mattir.), 319 Rhizidieae, 344, 345 Rhizidium (A. Br.), 346 Rhizocarpeai, 18, 19, 21, 114, -^^^ Rhizoclonium (Ktz.), 276 Rhizoglossum (Presl), 99 g Rhizoid, 16, 132, 139, X56, 174, 180, 222, 22b, 239, 241, 242, 273, 277, 282 2S^ ^^2 ^4 , 345 346, 363. 14, 43, 50, 60, 102, lb3, ib«, ^w, ^5'^, 256, 280, 318 Rhizome, 51, 72, 81, 86 Rhizomorph, 392, 270, 4iy Rhizomorpha (Roth), 309 — fragilis (Roth), 319 Rhizophore, 45 , , . , Rhizophydium (Schenk), 340 Rhizopoda, 456 Rhizopus (Ehrb.), 339, ^^\ . - nigricans (Ehrb.), 337, 29* 470 INDEX RHO Rhodomela (Ag.), 209 Rhodonielacea;, 209, 170, 174 Rhodophyll, 194 Rhodospermeae, 191 Rhodospermin, 194 Rhodosporea;, 191 Rhodymenia (Grev.), 208, 186 — bihda (K.tz.), 196 — palmata (Grev.), 209 — Palmetta (Grev.), 186 Rhodymeniacea;, 208, 171, 186 Rhytidolepida;. 117 Riccia(L.), 165, 166, 148 — glauca(L.), 148 Ricciaceae, 160, 165, 146-148 Ridge, 100, 106, 124, 129, 81 Riella (Mont.), 156, 159, 165, 166, 146 — helicophylla (rilont.), 146 Rivularia (Roth), 436, 363 — fluitans (Cohn), 436 — polyactis (Hauck), 353 Rivulariaces, 185, 427, 428, 433. 445, 363-365 Roccella tinctoria (DC), 284 Roestelia (Reb.), 386 Root-cap, 18, 78, 109 Root-hair, 18, 78 Rotation of protoplasm, 175, 163 ' Royal Fern,' 73, 90, 66, 67 Rozella (Cornu), 345, 347 Rumex, 364 Russula adusta (Fr.), 308 Rye, 310 Rytiphloea (Ag.), 194, 209 Saccharomvces (Meyen), 4, 380, 381, 268, 313 — albicans (Reess), 380 — cerevisiae (Meyen), 380, 288, 313 — ellipsoideus (Reess), 380 — Mycoderma (Reess), 380 — Pastorianus (Reess), 380 Sacconema (Brzi.), 437 Sacheria (Sir.), 214 Saddle, 51 .Salicaceae, 310 Salmon-disease, 332 Salvinia (L.), 17, 18, 25, 31, 7-11 — natans (L.), 7-11 Sahaniaceae, 12, 13, 20, 25, 114, 7-13 Saprolegnia (Nees ab Esenb.), 4, 332, 333. 334, 335, 338, 339, 346, 347 Saprolegnieae, 4, 308, 312, 324, 332, 338, 347, 377, 291, 292 Saprophytes, 315, 316, 317, 329, 366, 454 Sargasso Sea 232 Sargassum (Ae.), 230, 232, 235, 211 — bacciferum (Ag.), 232. 236, 211 Scalariform conjugation, 260, 265, 233. 234. 236, 237 — tracheide, 18, 76, 98, 123 Scenedesmus (Mey.)^ 303, 418, 352 — obtusus Mey.), 352 Schizaea(Sm.), 90, 91 SchizEeaceae, 64, 80, 81, 90, 122, 43, 69 Schizochlamys (A. Br.), 417, 348 — gelatinosa (A. Br.), 348 Schizogonium (Ktz.), 279 Schizomycetes, 433, 449, 379-382 Schizoneura (Schimp.), 124 Schizophyceae, 408, 336-378 Sciadiaceae, 410, 411 Sciadium (A. Br.), 411, 336 — arbuscula (A. Br.), 336 Sclerenchyme. 75, i23> ^3, 54 Scleroderma (Pers.), 397 SOR Sclerosis, 58, 309, 39 Sclerote, 309, 310, 361, 373, 374, 376, 392, 404, 271,309, 310.311,318 Sclerotinia (Fckl.), 373 — Fiickeliana (de By. and Wor.), 361, 374 — sclerotiorum (de Bj-.), 360, 361, 373, 374, 271 Sclerotium (Tode), 310 Scoiecopteris (Stur), 122, 94 — polymorpha (Stur), 94 Scolopendrium (Sm.), 8t, 85, 58 Scutiform leaf, 28, 8, 9 Scyamina (V'an Tiegh.), 295 Scylonema (Ag.), 438, 441, 445, 279 Scytonemaceae, 303, 427, 428, 433, 437, 366, 367 Scytonemeae, 438, 441, 445, 366, 367 Scytonemin, 427, 437 Scytosiphon(Ag.), 239, 241, 245 — lomentarium (Ag.), 246 Scytosiphonaceae, 245 Seaweeds, 184, 190, 191, 235, 237 Sebacina (Tul.), 389 Secondary capitulum, 178, 163 — embryo-sac, 14, 52, 3 — -growth in thickness, 49, 116, 125 — markings, 420, 353 — prothallium, 39 Secotium (Kze.), 395 — erythrocephalum (Tul.), 396 Secreting system, 139 Seftenbergia (Cord.), 122, 94 — ophidermatica (Stur), 94 Seirospora Griffithsiana (Harv.), 204 Seirospore, 196, 204, 180 Selaginella (Spring), 19, 20, 38, 39, 47, 20-27 - — caulescens Spr.), 20 — denticulata (Lk.), 24 — insqualifolia (Spr.), 22. 23, 25-27 — Martensii(Spr.), 20, 2l' Selaginellaceab, 12, 13, 18, 10, 38, 115, 130, 20^33, 87-91 Selagmelleae, 38,^ 39, 20-27 Selenastrum (Reinsch), 186, 303 Seta, 134, 144, 146, 110, 112 Sewage-fungus, 454 Sheath, 50, 428, 430, 434, 437 Shepherd's Purse, 326 Shield, 177, 163 Side-view (of diatoms), 421, 354 Sieve-hypha, 244 Sieve-plate, 240, 244, 217 Sieve-tube, 18, 58, 240, 244. 217 Sigillaria, 117, 118, 89, 91 Sigillariostrobus, 117, 118 Silica, 102, 107, 419, 420 Siphon, 192 Siphoneae, 186, 280, 281, 290, 308, 410, 248, 249 Siphonocladaceae, 186, 190, 279, 280, 281, 288, 304, 411, 256-258 Siphonocladus (Schr.), 289 Sirogonium (Ktz.), 264, 265, 267 Sirosiphon Ktz.), 439, 441, 449 Sirosiphoneae, 437, 438, 439, 441 Solenites (L. & H.), 119 Sorastreae, 186, 291, 302, 414, 418, 264, 265 Sorastrum (Ktz.), 186, 302, 264 — spinulosum (Nag.), 264 Sordaria (Ces. and De Not.), 354, 359, 360, 370 Sorede, 319, 282 Sorophore, 37, 19 Sorosporium (Rud.), 350, 352 — Saponariae (Rud.), 351 INDEX 471 SOR Sorus, II, 20, 24, 72, 79, 94, 122, 196, 237, 244, 251,347,19,58, 59,71,218 Spatoglossum (Ktz.), 254 Special bundle-sheath, 109 ' Sperm,' 7, 8 ' Sperm-cell,' 8 ' Spermatia,' 7, 360 ' Spermatozoid.' 8 Spermocarp, 180, 221, 165, 167, 168, 199 ' Spermogone,' 7, 360 Spermothamnion (Aresch.), 209, 176 — hermaphroditum (Nag.), 176 Sphacelaria (Lyngb.), 249, 223, 224 — cirrhosa (Ag.), 223, 224 Sphacelariaceae, 237, 239, 241, 249, 223, 224 Sphacele, 249, 223 Sphacelia (Lev.), 37^^, 309 Sphacelotheca (de By.), 352 — Hydropiperis (de By.), 350 Sphaerobolus ( 1 ode), 399 Sphserocarpus (Mich.), 160, 166, 147 — terrestris (Sm.), 147 Sphaerococcaceae, 208, 178, 187 Sphaerococcus (Stackh.), 208 Sphaerogonium (Rostaf.), 444 Sphairoplea (Ag.), 227, 203, 204 ^ annulina (Ag.), 226, 203, 204 Sphaeropleaceae, 188, 220, 226, 203, 204 ' Sphaerosp re,' 195 Sphaeroz^-ga (Ag.), 430, 433 Sphagnaceae, 132, 136, 139, 142, i44; 145; 151 125-131 Sphagnum (L.), 138, 156, 172, 125- 131 — acutifolium (Ehrh.), 125-127. 129-131 — cymbifolium (Dill). 128 — squarrosum (Pers.), 131 Sphenoglossiim (Emm.), 114 Sphenophylleae, 129, 130, lUi Sphenophyllum (Brongn.), 129, 130, 101 Sphenopteris crenata (L. & H.), 120, 92 Spherocrj-stal, 93 Sphyridium (Flot.), 361 Spinellus fusiger (Van Tiegh.), 338 Spiral bands, 152 Spirillum (Ehrb.), 450, 451, 382 Spirochaeta (Ehrb.), 451 Spirogj'ra (Lk.), 4, 264, 265, 266, 267, 330, 342, 236, 238 — bellis (Mass.), 238 ^ crassa(Ktz.), 264 — porticalis (Vauch.), 236 Spirulina (Lk.), 429, 441, 370 — tenuissima (Ktz.), 370 Splachnidium (Grev.), 235, 236 Splachnum(B. & S.), 149 — ampullaceum (L.), 116 Splenic fever, 452, 454 Spongiocarpeae, 209 Spongocladia (Aresch.), 276, 290 Spongodieae, 289 Spontaneous generation, 450 — movement, 415, 427, 431, 442 Sporange, 6 (see also under \ asc. Crypt., IMusc, Algae, Fungi, Mycet., and Prot.), 2, 37, 40, 41, 55, 56, 58-60, 63, 68, 71, 72, 75, 76, 83 93. 110, 111, 114-118, 122, 124, 131, 133, 134, 137, 145, 158, 293, 334 — dehiscence of, 79, 94, 135; i53; i59! ^^ Sporangiole, 339 Sporangiophore, 328, 337, 339, cX>i Sporangiospore, 6 Sporangites (Daws.), 115 Spore, 5 (see also under Vase. Crj-pt-; ^lusc, Algae, Fungi, Mycet., and Prot.), 37, 84, 85, 158. i81, 245. 249. 272, 275, 303, 317, 318, 332, 335, 361, '362, 37^381 STR Spore-sac, 147, 112 Sporid, 6, 314, 350, 351, 352, 362, 373,- 385) 336 . 390, 299, <14 Sporiferous filaments, 192 Sporocarp, 11, 353 (see also under Vase. Crj-pt. Algae, and Sporocarpeae), 5-7. 12, 18. 19 302-305 . > . — origin of, 359 Sporocarpeae, 353, 300-331 Sporocarpon (Williams.), 114 Sporochnaceae, 245 Sporochnus (Ag.), 241, 246, 219 — pedunculatus (Ag.), 219 Sporodinia (Lk.), 338, 339 grandis (Lk.),'337 ' Sporogenous tissue, 20. 46, 33 Sporogone, 134, 136, 144, 159, 163. 107, 110, 131,142,143,145,148,156,158 Sporophore, 309, 325, 327, 328, 336, 337, 340, 343= 363) 365, 367,- 374, 388, 389. 404, '£12, 275, 288, 293, 296, 303, 304, 327-329, 3^ Sporophore (compound), 301, 392, 393, 395, 396, 397> 398, 273, 319, 320 Sporophyll, 46, 51. 72. 99, no. 116. 32. 72. 75, 76, 83, 88 i-^ - . , . > Sporophyte, 10, 17, 132, 135, 159 Sporophytic budding, 69 Sprouting, 307, 314, 339, 352, 380, 381, 389, 268, olo SpjTJdia (Harv.), 193, 209 Spjiidiaceae, 209 Squamariaceae, 189, 190, 191, 202, 210, 188 Stag's-horn-moss, 61 Staurastrum Mey.). 260. 270, 239. 2^0 — Arachne (Raifs). 239' - teliferum (Ralfs), 240 Stauroneis (Ehrb.), 426 Staurospermum (Ktz.), 260, 263, 234 — capucinum (Ktz.), 263 — gracillimum (Hass.), ii34 Stemmatopteris (Cord.), 124, 95 — insignis (Cord.), 124 Stemonitis fusca (Roth), 334 Stephanosphaera (Cohn), 186, 299, 301 Stephensia (Tub), 358 Stereocaulon ramulosum 'Ach.), 279 Sterigma, 86, 340, 367, 370, 372, 376, 384, 3S6, 389, 394. 275. 304 Stichid, 196, 174 Stictosphaeria (Tub), 373 Stigeoclonium (Ktz.), 276, 284, 417 Stigma, 133, 143 Stigmaria, 118, 90, 91 — ficoides (Brongn.), 118, 90 Stigmatic cell, 17, 27, 133, 143, 15S, 15, 109 Sligmatomvces (Karst.), 378 — Baeri (P'eyr.), 312 Muscae (Karst.), 312 Stigonema (Ag.), 439, 441, 449, 366 — compactum (Kirchn.), 440 — minutum (Hass.), 366 Stigonemeae, 437, 438, 445, 366 Sdpe, 230, 239, 241, 242, 286, 391, 319, 320 Stipule, 92, 174 Stoechospermum (Ktz.), 254 Stolon, 78, 133, 139 Stomate, 19, 72, 78, 93, 107, 144, 169, 23, 82, 153-155 Stomium, 79, 55 Stoneworts, 181 Strand-mj-cele, 309 Streblonema (Derb.), 239 Stroma, 35o,_ 352, 355, 356, 370, 375, 311 Struthiopteris (L.), 66 — germanica (L.), 66, 69, 77 Struvea (Sond.), 289 47 INDEX STY Stylospore, 339, 362 Stypocaulon (Ktz.), 249 Subhymenial layer, 355, 368, 372, 393, 394, 305 Submerged leaf, 28, 7, 8 Subsidiary cell, 107 Sulphur, 454, 381, 382 Surirella ('lurp.), 426, 357 — splendida (Ktz.), 357 Suspensor, 41, 56, 337, 338, 21, 293-296 Suture, 421 Swarm-cell, 198, 218, 239, 292, 196, 259, 263 Swarming motion, 446 Swarm-spore, 312. 401, 402, 405, 252, 332 Sykidion (Wright), 414 Symbiosis, 318 Symploca (Ktz.), 441, 444, 372, 373 — hydnoides(Ktz.), 372 — violacea (Hauck), 373 Synalissa symphorea (Nyl.), 279 Synange, 94, 122, 71, 94 Syncephalis (Van Tiegh.), 340 Synchytrieae, 344, 345._ 347 Synchytrium Tara.xaci (de By.), 347 Synechococcus (Nag.), 447, 449 Synedra (Ehrb.). 426, 357 — Arcus (Ktz.), 357 Syngenetica;, 188, 237, 256, 232 Syz5-gites(Ehrb.), 337 Tabellaria (Ehrb.), 426 Tangle, 244 Tannin-cell 34, 76, 92 Taenia (Ag.), 254 Tapetal cells, 20, 25, 36, 60, 80, 33 Tapete, 20, 80 Targionia (Mich.), 171 Targionieae, 171 Tayloria (Hook.), 149 Teeth of Hydneae, 393 peristome, 135, 145, 111 sheath, 102, 105, 124, 83 Teleutospore, 6, 385, 386, 390, 391, 274, 314, 315 Terfezia (Tul.), 358 Terminal nodule (diatoms), 353 Tetmemorus (Ralfs), 268 Tetrachytrium triceps (Sorok.), 347 Tetrapedia (Reinsch). 447 Tetraphis (Hedw.), 149 — pellucida (Hedw.), 140, 114 Tetraspora (Lk.), 219, 418, 448 — gelatinosa (Desv.), 418 Tetrasporange, 195, 217, 254, 170. 172-174, 177, 182, 183, 186, 190, 230 Tetraspore, 6, 185, 195, 217, 254, 195, 231 Thalassiophyllum (Post.), 244 Thalloid Hepaticae, 135, 156, 160, 135, 136, 143-159 Thallophytes, 2, 3, 4, 135, 156, 184 Thallus, 132, 184, 191. 306, 430, 432, 153. 188, 199, 212, 227, 230, 307, 358 — compound, 306 Thamnidium (Lk.), 339 Theca, 134 Thecaphora hyalina (Fingerh.), 351 — Lathyri (Kuhn), 351 Thelephoreae, 391 Thorea (Borj-)) 211 Thrush-fungus, 38 Tilletia (Tul.), 350, 351 — caries (Tul.), 315, 299 Tilopterideae, 249, Tilopteris (Ktz.), 249 UST Tmesipteris (I'err.h.), 61, (^ii ^^ -- tanncnsis (I'ernh.), 41 Tndea(\VilId.), 89, 90 superba (Col.), 90 Tolypella(A. Br.), 182 Tolyposporium (Woron.), 351 Tolypothrix (Ktz.), 429, 437, 438, 439, 440, 441 — amphibia (Zopf), 440 Tortuia (Hedw. ), 149 Trabecule, 41, 52, 147, 23, 32, 33, 112 Tracheide, 18, 76 Trama, 394, 395, 396, 397, 321 Traquairia (Carruth.), 114 Tree-ferns, 71, 75, 78, 85, 57 Tremella (Dill.), 389 — mesenterica (Retz.), 316 Tremellinejt;, 343, 388, 389 Tremeiloid Uredineae, 386 Trentepohlia (Mart.), 185, 280, 284, 247 — Bleischii (Rabenh.), 247 Triceratium (Ehrb.), 420, 357 — Favus (Ehrb.), 357 Trichocoma (Jungh.), 319 Trichosyne, 188, 199, 219, 220, 360, 369, 370, 371, 372, 373, 378, 379, 385, 175, 176, 179, 192, 306, 307 Trichomanes (L.), 70, 71, 86, 87, 88, 61 — alatum (Sw.), 86 — pyxidiferum (L.), 86, 61 Trichome, 428, 359 Trichophilus (Web.), 280 Trichophore. 199, 176, 179 ' Trichosporange,' 237 Tripoli, 424 Trochopteris (Gardn.), 91 Truffle-familj^, 357 Truffles, 358 Tuber, 56, 112, 38, 86 — (Mich.), 357, 358 — rufum (Pico), 301 Tuberaceae, 308, 357 Tubereae, 358 Tubular organ, 161 Tubuli of Polyporeae, 393 Tubulinae, 401 Tuburcinia (Berk.), 350, 351, 352 — Trientalis (Berk.), 352 Tulostoma (Pers.), 399 Udotea (Lmx.), 289 Udoteaceae, 289, 258 Ulodendron (Stemb.), 116 Ulothrix (Ktz.), 185, 277, 278, 279, 246 — implexa (Ktz.), 246 — zonata (Ktz.), 277 Ulotrichaceae, 187, 273, 277, 246 Ulva(L.), 189, 217, 304, 196 Ulvaceae, 189, 190, 195, 196, 198, 217, 218, 219, 279, 418, 196-198 Umbelliferae, 327, 348, 364 Unicellular plants, 184, 281, 284, 286, 288, 427 Unilocular zoosporange, 187, 237, 212, 219, 220, 223 Uredineae, 4, 312, 315, 383, 391, 274, 314, 315 — (tremeiloid), 386, 390 Uredo (Pers.), 383, 385 Uredospore, 6, 385, 386, 274, 314, 315 Urn, 134 Urococcus (Hass.), 418, 350 — insignis (Hass ), 350 Urocystis (Rabenh.), 350, 351, 352 Urospora (Aresch.). 273, 276 Usnea barbata (Fr.), 282 Ustilagineae, 4, 315, 349, 299 IXDEX 473 UST Ustilago (Pers.), 351 — carbo (Tul.), 351 — destruens (luL), 351 — Hydropiperis (Schm.), — longissima (Tul.)i 351 Ustulina (Tul.), 373 550 Vaccin'ium V'itis-id.ea, 388 Vagina, 134, 135, i44. 146 163, 131 VallecuSar canal, 105 Valonia (Gin.), =39, 411, 257 — macrophysa (Ktz.), 257 Valoniacea;, 289, 257 Valve, 420, 355-355 Valve-view, 421, 353, 3o4 Vampyrella (Cienk.), 405 Vascular bundle-sheath, i3 — Cryptogams, i, 2, 10, 2 — cylinder. ^8. 39 Vaucheria (DC), 186, 2S1, 283, 284, 248, 249 — dichotoma (Lyngb.), 249 - sessilis (Vauch.), 248 Veil, 50 Velum partiale, 393 — universale, 393, 397 Venter, 16, 39, 68, 133 16, , 76, 39 4-101 Ventral canal-cell, Verbascum, 364 Vesicle, 23, 17, 44 Vessel, 76 Vibrio (Cohn), 440, 451 Vidalia (Lmx.), 194, 205 Vine. 327 — mildew, 364 Violet-stone, 280 Vittaria (Sm.), 67, 85 Volkmamiia (Sternb.), 127 Volva, 393, 318 Volvocinca;, 291, 292, 259 Volvox (L.), 4, 292, 295, 259 - globator (L.), 292, 2o9 Vorticella, iqq Water-beetles, 378 Water-net, 296 Weissia (Hedw.), 149 ' Wendungszellen,' 179, 166 Whip-shaped filaments. 17B, 318 143, 159, 109, 158 7, 40, 69, 143, 159, 45 163 ZYG Woodsia (R. Br.), 85, 58 Woodwardia (Sm.), 85, 53 — radicans (Sm.), 78 Woronina (Cornu), 345, 347 ■ Woronin's hj-pha,' 360, 373, 385 Wrangelia (Ag.), 209 Wrangeliacea;, 209, 176, 177 Xanthiuil M (Ehrb.), 269, 239 — cristatum (Br6b.), 239 Xenococcus (RostaC), 444 Xylaria(Hill), 360, 373, 385 Xylarieae, 373 Yeast, 380, 268, 313, Yellow cells of Radiolarians, 318 Zamia, 1 Zanardinia (Xardo), 239, 251, 252, 228, 229 — collaris (Crouan), 2^8, 229 Zippea (Cord.), 124 Zonal view (diatoms), 421 Zonaria (Harv.), 254 Zonate (tetraspores), 195 Zoogamete, 185 (see also under Alua; and Prot.), 196, 222, 246, 247, 252, 260, 26'3 Zooglcea, 433, 444, 451 Zoosphere, 252, 295, 229 Zoosporange, 220 (see also uader Alga;, Fungi, and Prot.), 201, 252-255, 258, 259. 272. 277! 287-289, 291, 297 Zoosporangiophore, 326, 275, 287 Zoospore, 6 (see also under Alga;, Fungi, and Prot.). 199, 201, 232, 242, 259, 277, 289, 291, 292,297 Zygnema (Ktz.), 258, 259, 264, 265, 267, 237 — pectinatum (Ag.), 237 Zygnemacese, 187, 258, 259, 264, 236 233 Zygochytrium (Sorok.), 341 Zygodon (H. & T.), 149 Zygogonium (Ktz.), 267 Zygomycetes, 4, 335, 29J-299 Zygosperm, 218 (see also under Alga; and Fungi), 222, 233-238, 241, 252, 263, 293-29? 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