•NRLF B 3 313 fiS7 '* •Jfc 7T :>'•• -* -' .»4w .. \ <' / THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA DAVIS Alf INTRODUCTION J k BOTANY BY JOHN LINULEY, PH. D. F.R.S, UTY COLLKGK, LONDON, BT<:. WITH SIX COPPER-PLATES AND NUMEROUS WOOD-ENGRAVINGS. FOURTH EDITION, WITH CORHECTIONS AND NUMEROUS ADDITIONS. IN TWO VOLUMES. VOL. II. LONDON: LONGMAN, BROWN, GREEN, AND LONGMANS, PATERNOSTER ROW. MDCCCXLVIII. .LIBRARY UNIVERSITY OF CALIFORNIA DAVIS LONDON : BRADBURY AND EVANS, PRINTERS, WHITEFRIARS. CONTENTS OF VOL. II. ORGANOGRAPHY (Continued.) CHAP. II. (Continued.) Fruit Classification of Fruits Seed 25 Albumen 54 Embryo . 59 Germination 60> 62 Naked Seeds • • • 69 Morphology of Floral Organs 70 CHAP. III. Compound Organs in Flowerless Plants, or Acrogens . Ferns no Lycopodiacese Marsileacere 101 Equisetacese l14 Mosses and Andraeacese Jungermanniacese and Hepaticse Lichens 117 Fungacese Algacese BOOK II.— PHYSIOLOGY. CHAP. I. General Considerations .132 CHAP. II. Vitality 144 CHAP. III. Chemical Constitution of the Elementary Organs . . .162 CHAP. IV. Elementary Organs 171 CHAP. V. Root 18° 0^ s^J VI CONTENTS. PAGE CHAP. VI. Stem and the Origin of Wood 187 CHAP. VII. Leaves .202 CHAP. VIII. Bracts 208 Calyx and Corolla 208 Disengagement of Caloric 211 CHAP. IX. Fertilisation 217 Sexuality of Plants 236 Mules 241 CHAP. X. Fruit . . ,.. '. . . . 252 Changes during ripening 256 Bletting 257 CHAP. XI. Seeds 259 Germination 259 Action of Heat 260 Their Longevity 266 CHAP. XII. Food of Plants 270 Carbon 270 Water 272 Nitrogen 273 Power of Selection . 275 Exhaustion of Soil 285 Manures 286 CHAP. XIII. Digestion 287 Decomposition of Carbonic Acid 295 CHAP. XIV. Of Secretions 300 CHAP. XV. Of Respiration 308 CHAP. XVI. Of the Movement of Fluids 323 General Motion . 325 Rotation 331 Cyclosis 336 BOOK III.— GLOSSOLOGY. Absolute Terms 344 Figure . 347 Division 358 Surface 363 Texture . . 366 Size . . . • . .367 Duration 368 Colour . . . . . . 369 Veining 373 CONTENTS. vii BOOK III. — GLOSSOLOGY (Continued.) PACK Individual Relative Terms 374 Estivation , 374 Direction 376 Insertion 378 Collective Terms 380 Arrangement 380 Number .... 383 Terms of Qualification 384 Signs 384 INTRODUCTION BOTANY BOOK I. ORGANOGRAPHY ; OR, OF THE STRUCTURE OF PLANTS. CHAPTER II. OF THE COMPOUND ORGANS IN FLOWERING PLANTS Continued. 14. Of the Fruit. The fruit (figs. 136. to 168.) is the ovary or pistil arrived at maturity. But, although this is the sense in which the term is strictly applied, yet in practice it is extended to what- ever is combined with the ovary when ripe. Thus the pine- apple fruit consists of a mass of bracts, calyxes, corollas, and ovaries; that of the nut, the acorn, and many others, of the superior dry calyx and ovary; that of the apple of a succulent superior calyx, corolla, and ovary; and that of the strawberry- blite of a succulent inferior calyx and dry ovary. The fruit being the matured ovary, it should exhibit upon some part of its surface the traces of a style or stigma ; and this mark will, in many cases, enable the student to distin- guish minute fruits from seeds. Many fruits were formerly called naked seeds, such as those of Umbellifers, Labiates, and Borageworts, and the grain of corn ; but now that atten- tion has been paid to the gradual development of organs, such errors have been corrected. In cases where a trace of VOL. II. B FRUIT. [BOOK i. the style cannot be discovered, anatomy will generally show whether a minute body is a seed or fruit, by the presence, in the latter case, of two separable and obviously organically distinct coatings to the nucleus of the seed; but in other cases, where the pericarp and the integuments of the seeds are combined in a single covering, and where no trace of style remains, as sometimes happens, nothing can be deter- mined as to the exact nature of a given body without follow- ing it back in its growth to its young state. This, however, may be stated, that naked seeds, properly so called, are not known to exist, unless accidentally, in more than three or four orders in the whole vegetable kingdom; viz. in Conifers and Cycads, where the ovules also are naked, and in Peliosanthes Teta and Leontice, in which the ovules, originally enclosed in an ovary, uniformly rupture it at an early period after fertilisation, and subsequently continue naked until they become seeds. Such being the case, it follows that all the laws of structure which exist in the ovary are equally to be expected in the fruit; and this fact renders a repetition in this place of the general laws of formation unnecessary. Nevertheless, as, in the course of the advance of the ovary to maturity, many changes often occur which contribute to conceal the real structure of the fruit, it is in all cases advisable, and in many absolutely necessary, to examine the ovary, in order to be certain of the exact construction of the fruit itself. These changes are caused by the abortion, non-development, obli- teration, addition, or union of parts. Thus the three-celled six-ovuled ovary of the oak and the hazel becomes, by the non-development of two cells and five ovules, a fruit with one seed; the three-celled ovary of the cocoa-nut is converted into a one-celled fruit, by the obliteration of two cells and their ovules; and the two-celled ovary of some Pedaliads becomes many-celled, by a division and elongation of the pla- centae. In Cathartocarpus Fistula a one-celled ovary changes into a fruit having each of its many seeds lodged in a separate cell, in consequence of the formation of numerous horizontal membranes which intercept the seeds. A still more extra- ordinary confusion of parts takes place in the fruit of the STRUCTURE.] PARTS OF THE FRUIT. 3 pomegranate after the ovary is fertilised ; and many other cases might be mentioned. Every fruit consists of two principal parts, the pericarp and the seed, the latter being contained within the former. When the ovary is inferior, or coheres with the calyx, the latter and the pericarp are usually so completely united as to be inse- parable and undistinguishable : in such cases it is usual to speak of the pericarp without reference to the calyx, as if no such union had taken place. Botanists call a fruit, the peri- carp of which adheres to the calyx, an inferior fruit (fructus inferus) ; and that which does not adhere to the calyx, a superior fruit (fructus superus). But Desvaux has coined other words to express these ideas : a superior fruit he calls autocarpic ; an inferior fruit, heterocarpic ; terms unnecessary and unworthy of adoption. Everything which in a ripe fruit is on the outside of the real integuments of the seed, except the aril, belongs to the pericarp. It consists of three different parts, the epicarp t the sarcocarp, and the endocarp ; terms contrived by Richard, and useful in practice. The epicarp is the external integument or skin ; the endo- carp, called putamen by Gsertner, the inner coat or shell ; and the sarcocarp, the intermediate flesh. Thus, in the peach, the separable skin is the epicarp, the pulpy flesh the sarco- carp, and the stone the endocarp or putamen. In the apple and pear the epicarp is formed by the cuticle of the calyx, and the sarcocarp is confluent with the remainder of the calyx in one fleshy body. The pericarp is extremely diversified in size and texture, varying from the dimension of a single line in length to the magnitude of two feet in diameter ; and from the texture of a delicate membrane to the coarse fabric of wood itself, through various cartilaginous, coriaceous, bony, spongy, succulent, or fibrous gradations. The base of the pericarp is the part where it unites with the peduncle ; its apex is where the style was : hence the organic and apparent apices of the fruit are often very different, especially in such as have the style growing from 4 DEHISCENCE. [BOOK i. their sides, as in Rosacese and Chrysobalanacese, Labiatse and Boraginacese. When a fruit has arrived at maturity, its pericarp either continues perfectly closed, when it is indehiscent, as in the hazel nut ; or separates regularly round its axis, either wholly or partially, into several pieces : the separation is called dehis- cence, and such pieces valves ; and the axis from which the valves separate, in those cases where there is a distinct axis, is called the columella. When the dehiscence takes place through the dissepiments, it is said to be septicidal ; when through the back of the cells, it is called loculicidal; if along the inner edge of a simple fruit it is called sutural; if the dissepiments are separated from the valves, the dehiscence is named septifragal. In septicidal dehiscence the dissepiments divide into two plates and form the sides of each valve, as in Rhododendron, Menziesia, &c. Formerly botanists said that in this sort of dehiscence the valves were alternate with the dissepiments, or that the valves had their margins turned inwards. This may be understood from fig. 169., which represents the fg. 169. relative position of parts in a transverse section of a fruit with septicidal dehiscence ; v being the valves, d the dissepi- ments, and a the axis. fig. 170. In loculicidal dehiscence the dissepiments form the middle of each valve, as in the lilac, or in the diagram 170., STRUCTURE.] ANOMALOUS DEHISCENCE. 5 where the letters have the same value as above. In this it was formerly said that the dissepiments were opposite the valves. In septifragal dehiscence the dissepiments adhere to the axis and separate from the valves, as in Convolvulus ; or in the diagram 171., lettered as before. In sutural dehiscence there are no dissepiments, the fruit being composed of only one carpel, as the Pea. Besides these regular forms of valvular dehiscence, there is a very anomalous mode which occurs in a very few plants, and is called circumscissile. This takes place by a transverse cir- cular separation, as in Anagallis ; in Jeffersonia it only takes place half round the fruit. In some cases, as in lomentaceous legumes, the transverse disarticulation may be supposed to have some relation to the pinnate leaves, whose modification, in those instances, forms the carpel. In other cases the explanation is far less obvious, and must be at least very different. Perhaps the best account of transverse dehiscence is that of Mr. Hincks, as reported in the Annals of Natural History, vol. xvii. " In the fruit, as in the calyx, this author believes that horizontal disruption arises from the force of cohesion of the parts of the circle, the absence of any of the causes favourable to dehiscence along the midrib of the carpellary leaf, and the operation of some force pressing either from without or from within on one particular line encircling the fruit. In the circumscissile capsule of Anagallis, he states that the central free receptacle with the seeds upon it continuing to enlarge in both diameters after the envelope has ceased to grow, and having occupied from the first the entire cavity, it is 6 ANOMALOUS DEHISCENCE. [BOOK i. naturally to be expected, since the chief extension of the inte- rior parts is upwards (the natural direction of growth), while the enlargement of the seeds in the lower half tends to press back the parts of the lower hemisphere, that uniform and regular pressure will resolve a nearly spherical capsule into two equal hemispheres. This remark he applies to Centun- culus also, but confesses himself at a loss to give any reason why the opening of Trientalis, which depends on the same general causes, should be irregular. For the separation of the lid of the capsule in Hyoscyamus he accounts by the con- traction and rigidity of the throat of the calyx exercising a gradually increasing pressure around the upper part of the capsule, and thus causing its separation by the first of the general principles laid down. Lecythis, he thinks is to be explained by the third of his general principles. In illustra- tion he refers to a monstrosity of the common Tulip. In this monstrosity, the upper leaf, being unusually developed, cohered by its edges so firmly as to imprison the flower, and this constraint occurring at a period when the stalk was increasing in length, and previous to any considerable en- largement of the flower-bud, the force applied was chiefly vertical, and carried off the upper part of the leaf in the form of a calyptra, leaving the lower part in the shape of a cup, from the centre of which the stem appeared to rise. The separation of the lid of the capsule of Lecythis, Mr Hincks believes to be effected in an analogous manner; the septa which form the two or four cells into which the fruit is divided, meet in a thickened axis, and the outer part of the fruit becoming (partly from its natural texture, and partly from the adherence of the torus and calyx) hard, solid, and fully grown, while the axis continues slowly to extend, and thus to press upwards that portion of the capsule which rests upon it, causes that portion first to become slightly prominent, and finally by a strain upon the vessels of that particular part to fall off in the shape of a lid. In Couroupita the pres- sure is sufficient to mark the surface of the fruit with a promi- nence, but from the partitions giving way early, and from the abundant juices produced in the interior, there has not been sufficient pressure to occasion disruption. In all the species STRUCTURE.] FALSE DEHISCENCE. 7 of Lecythis, the extent of the loose cover corresponds with the extent of the axis, and what remains of the latter continues attached to it. As regards Lomentaceous fruits in general, the author believes that the intervals between the seeds being sufficient to admit of the sides of the fruit cohering (which is promoted in particular instances by special causes), the swelling of the seeds afterwards stretches the parts over them in a degree which this coherence prevents from being equally distributed, drags the tissue forcibly from the junc- tures which are fixed points, and thus there being a strain in each direction from the middle line of the juncture the contraction of drying in the ripening of the fruit effects the separation." Valvular dehiscence, which is by far the most common mode by which pericarps open, must not be confounded with either rupturing or solubility, — irregular and unusual con- trivances of nature for facilitating the dispersion of seeds. In valvular dehiscence the openings have a certain reference to the cells, as has been already shown; but neither rup- turing nor solubility bear any distinct relation to the cells. Rupturing consists in a spontaneous contraction of a portion of the pericarp, by which its texture is broken through, and holes formed, as in Antirrhinum and Cam- panula. Solubility arises from the presence of certain transverse contractions of a one-celled pericarp, through which it finally separates into several closed portions, as in Ornithopus. For the nature of the placenta and umbilical cord see the observations under ovary. Of these parts, which are mere modifications of each other, the former often acquires a spongy dilated substance, occasionally dividing the cells by spurious dissepiments, and often giving to the fruit an appearance much at variance with its true nature. In some seeds, as Euonymus europseus, it becomes exceed- ingly dilated around each seed, forming an additional envelope, called aril. The true character of this organ was unknown till it was settled by Richard : before his time the term was applied, not only in its true sense to an enlargement of the 8 MODIFICATIONS OP FRUIT. [BOOK i. placenta, but also to the endocarp of certain Cinchonads and Rueworts, to the seed-coat of Jasminum., of Orchids, and others, and even to the perianth of Carex. A very remarkable instance of the aril is to be found in the nutmeg, in which it forms the part called the mace surrounding the seed. It is never developed until after the fertilisation of the ovule. It will be further and much more particularly treated of, when speaking of the seed. Having thus explained the structure of the pericarp, it is in the next place necessary to inquire into the nature of its modifications, which in systematic botany are of considerable importance. It is, on the one hand, very much to be regretted that the terms employed in this department of the science, which is that of Carpology, have been often used so vaguely as to have no exact meaning ; while, on the other hand, they have been so exceedingly multiplied by various writers, that the language of carpology is a mere chaos. In practice but a small number of terms is actually employed; but for collec- tions of fruits, or minute carpological arrangements, a large number is desirable ; and it cannot be doubted that, if it were not for the excessive inconvenience of overburdening the sci- ence with words, it would conduce to clearness of description if botanists would agree to make use of some precise and uniform nomenclature. What, for instance, can be more embarrassing than to find the term nut applied to the superior plurilocular pericarp of Verbena, the gland of Corylus, and the achenia of Rosa and Borago: and that of berry to the fleshy envelope of Taxus, the polyspermous inferior fruit of Ribes, the succulent calyx of Blitum, and several other things ? So much discordance, indeed, exists in the application of terms expressive of the modifications of fruit, that it is quite indispensable to give the definitions of some of the most eminent writers upon the subject in their own words, in order that the meaning attached by those authors to carpo- logical terms, when employed by themselves, may be clearly understood. In the phraseology of writers antecedent to Linn&us, the STRUCTURE. ] OLD WRITERS — LINN^US — GARTNER. 9 following are the only terms of this description employed; viz. : — 1. Bacca, a berry : any fleshy fruit. 2. Acinus, a bunch of fleshy fruit : especially a bunch of grapes. 3. Cachrys, a cone : as of the pine tree. 4. Pilula, a cone like the Galbulus of modern botanists. 5. Folliculus (Fuchs), any kind of capsule. 6. Grossus, the fruit of the fig unripe. 7. Siliqua, the coating of any fruit. In his Philosophia Botanica, LINNAEUS gives the following definitions of the terms he employs : — 1. Capsula, hollow, and dehiscing in a determinate manner. 2. Siliqua, two-valved, with the seeds attached to both sutures. 3. Legumen, two-valved, with the seeds attached to one suture only. 4. Conceptaculum, one-valved, opening longitudinally on one side, and distinct from the seeds. 5. Drupa, fleshy, without valves, containing a nut. » 6. Pomum, fleshy, without valves, containing a capsule. 7. Bacca, fleshy, without valves, containing naked seeds. 8. Strobilus, an amentum converted into a pericarp. GARTNER has the following, with definitions annexed to them : — 1. Capsula, a dry, membranous, coriaceous, or woody pericarp, sometimes valveless, but more commonly dehiscing with valves. Its varieties are, — a. Utriculus, a unilocular one-seeded capsule, very thin and transparent, and constantly valvular; as in Cheno- podium, Atriplex, Adonis. b. Samara, an indehiscent, winged, one- or two-celled cap- sule ; as Ulmus, Acer, Liriodendron. c. Folliculus, a double one-celled, one-valved, membranous, coriaceous capsule, dehiscing on the inside, and either bearing the seed on each margin of its suture, or on a receptacle common to both margins; as Asclepias, Cinchona, and Vinca. 2. Nux, a hard pericarp, either indehiscent or never dividing into more than two valves ; as in Nelumbium, Boragi- neae, and Anacardium. 10 GJ1ETNER — WILLDENOW. [BOOK i. 3. Coccum, a pericarp of dry elastic pieces or coccules, as in Diosma, Dictamnus, Euphorbia. 4. Drupa, an indehiscent pericarp with a variable rind, very different in substance from the putamen, which is bony, as in Lantana, Cocos, Sparganium, Gaura, &c. 5. Bacca, any soft pericarp, whether succulent or otherwise ; provided it does not dehisce into regular valves, nor con- tain a single stone adhering to it. Of this the following are kinds : — a. AcinuSj a soft, succulent, semi-transparent, unilocular berry, with one or two hard seeds ; as the Grape* Rivina, Rhipsalis, Rubus, Grossularia, &c. b. Pomum, a succulent or fleshy, two- or many-celled berry, the dissepiments of which are fleshy or bony* and coherent at the axis ; as Pyrus, Cratsegus, Cydo- nia, Sapota, and others. c. Pepo, a fleshy berry, with the seeds attached at a dis- tance from the axis, upon the parietes of the peri- carp ; as Cucumis, Stratiotes, Passiflora, Vareca, and others. To the term bacca, all other succulent fruits are referred which do not belong to Acinus, Pomum, or Pepo; as Garcinia, Caryophyllus, Cucubalus, Hedera. 6. Legumen, the fruit of Leguminosae. 7. Siliqua and Silicula, the fruit of Cruciferae. WILLDENOW defines those employed by him in the follow- ing manner : — 1. Utriculus, a thin skin enclosing a single seed. Adonis, Galium, Amaranthus. £. Samara, a pericarp containing one seed, or at most two, and surrounded by a thin membrane, either along its whole circumference, or at the point, or even at the side. Ulmus, Acer, Betula. 3. Folliculus, an oblong pericarp bursting longitudinally on one side, and filled with seeds. Vinca. 4. Capsula, a pericarp consisting of a thin coat containing many seeds, often divided into cells, and assuming various forms. Silene, Primula, Scrophularia, Euphor- bia, Magnolia. STRUCTURE.] WILLtfENOW. 11 5. Nuse, a seed covered with a hard shell which does not burst. Corylus, Quercus, Cannabis. 6. Drupa, a nut covered with a thick succulent or cartilagi- nous coat. Prunus, Cocos, Tetragonia, Juglans, Myris- tica, Sparganium. 7. Bacca, a succulent fruit containing several seeds, and not dehiscing. It encloses the seeds without any determi- nate order, or it is divided by a thin membrane into cells. Kibes, Garcinia, Hedera, Tilia. Rubus has a compound bacca. 8. Pomum, a fleshy fruit that internally contains a capsule for the seed. It differs from the celled berry in having a perfect capsule in the heart. Pyrus. 9. Pepo, a succulent fruit which has its seeds attached to the inner surface of the rind. Cucumis, Passiflora, Stratiotes. 10. Siliqua, a dry elongated pericarp consisting of two valves held together by a common permanent suture. Cruci- ferse. Silicula is a small form of the same. 11. Legumen, a dry elongated pericarp consisting of two valves externally forming two sutures. Leguminosse. 12. Lomentum, a legumen divided internally by spurious dissepiments, not dehiscing longitudinally, but either remaining always closed, as in Cathartocarpus fistula, or separating into pieces at transverse contractions along its length, as in Ornithopus. The following are enumerated as spurious fruits : — 13. Strobilus, an amentum the scales of which have become woody. Pinus. 14. Spurious capsule. Fagus, Rumex, Carex. 15. Spurious nut. Trapa, Coix, Mirabilis. 16. Spurious drupe. Taxus, Anacardium, Semecarpus. 17. Spurious bacca. Juniperus, Fragaria, Basella. By this author the names of fruits are, perhaps, more loosely and inaccurately applied than by any other. LINK objects to applying particular names to variations in anatomical structure; observing, "that botanists have strayed far from the right road in distinguishing these terms by characters which are precise and difficult to seize. Terms are 12 LINK. [BOOK i. only applied to distinct parts, as the leaf, peduncle, calyx, and stamens, and not to modifications of them. Who has ever thought of giving a distinct name to a labiate or papiliona- ceous corolla, or who to a pinnated leaf ?" But this reasoning loses its value, when it is considered that the fruit is subject to infinitely greater diversity of structure than any other organ, and that names for these modifications are useful, for the sake of avoiding a minute explanation of the complex differences upon which they depend. Besides, to admit, as Link actually does, such names as capsula, &c., is abandoning the argument; and when the following definitions, which this learned botanist has proposed, are considered, I think that little doubt will exist as to whether terms should be employed in the manner recommended by himself, or with the minute accuracy of the French. According to Professor Link, the following are the limits of carpological nomen- clature : — 1. Capsula, any dry, membranous, or coriaceous, pericarp. 2. Capsella, the same, if small and one-seeded. 3. Nuoe, externally hard. 4. Nucula, externally hard, small, and one-seeded. 5. Drupa, externally soft, internally hard. 6. Pomum, fleshy or succulent, and large. 7. Bacca, fleshy or succulent, and small. 8. Bacca sicca, fleshy when unripe, dry when ripe, and then distinguishable from the capsule by not being brown. egumen, \ ^ pericarps of certain natural orders. 10. Siliqua, J 11. Amphispermium, a pericarpium which is of the same figure as the seed it contains. In more recent times there have been three principal attempts at classing and naming the different modifications of fruit; namely, those of Richard, Mirbel, and Desvaux. These writers have all distinguished a considerable number of variations, of which it is important to be aware for some purposes, although their nomenclature is not much employed in practice. But, in proportion as the utility of a classifica- tion of fruit consists in its theoretical explanation of structure STRUCTURE.] RICHARD MIRBEL. 13 rather than in a strict applicability to practice, it becomes important that it should be founded upon characters which are connected with internal and physiological distinctions rather than with external and arbitrary forms. Viewing the subject thus, it is not to be concealed, that, notwithstanding the undoubted experience and talent of the writers just mentioned, their carpological systems are essentially defective. Besides this, each of the three writers has felt himself justi- fied in contriving a nomenclature at variance with that of his predecessors, for reasons which it is difficult to compre- hend. If a complete carpological nomenclature is to be established, it ought to be carried farther than has yet been done, and to depend upon principles of a more strictly theoretical character. I have accordingly ventured to propose an arrangement, in which an attempt has been made to adjust the synonymes of carpological writers, and in which the names that seem to be most legitimate are retained in every case, their definitions only being altered ; previously to which I shall briefly explain the methods of Richard, Mirbel, and Desvaux. THE ARRANGEMENT OF RICHARD. Class 1. Simple fruits. § 1- Dry- * Indehiscent. * * Dehiscent. § 2. Fleshy. Class 2. Multiplied fruits. Class 3. Aggregate or compound fruits. THE ARRANGEMENT OF MIRBEL. Class 1. Gymnocarpians. Fruit not disguised by the ad- herence of any other organ than the calyx. Ord. 1. Carcerular. Pericarpium indehiscent, but sometimes with apparent sutures, generally dry, superior or inferior, mostly unilocular and mono- spermous, sometimes plurilocular and polysper- mous. 14 DESVAUX. [BOOK i. Ord. 2. Capsular. Pericarpium dry, superior, or infe- rior, opening by valves, but never separating into distinct pieces or cocci. Ord. 3. Dieresilian. Pericarpium superior or inferior, dry, regular, and monocephalous (that is, having one common style), composed of several distinct pieces arranged systematically round a central real or imaginary axis, and separating at maturity. Ord. 4. Etaerionar. Pericarps several, irregular, superior, one- or many-seeded, with a suture at the back. Ord. 5. Cenobionar. A regular fruit divided to the base into several acephalous pericarpia; that is to say, not marked on the summit by the stigmatic scar, the style having been inserted at their base. Ord. 6. Drupaceous. Pericarpium indehiscent, fleshy externally, bony internally. Ord. 7. Baccate. Succulent, many-seeded. Class 2. Angiocarpians. Fruit seated in envelopes not form- ing part of the calyx. THE ARRANGEMENT OF DESVAUX. Class 1. Pericarpium dry. Ord. 1. Simple fruits. § Indehiscent. § § Dehiscent. Ord. £. Dry compound fruits. Class 2. Pericarpium fleshy. Ord. 1. Simple fruits. Ord. 2. Compound fruits. In explanation of the principles upon which the classifica- tion of fruit which I now venture to propose is founded, it will of course be expected that I should offer some observa- tions. In the first place, I have made it depend primarily upon the structure of the ovary, by which the fruit is of necessity influenced in a greater degree than by anything STRUCTURE.] PRINCIPLES OF SUCH CLASSIFICATIONS. 15 else, the fruit itself being only the ovary matured. In using the terms simple and compound, I have employed them precisely in the sense that has been attributed to them in my remarks upon the ovary ; being of opinion that, in an arrange- ment like the following and those which have preceded it, in which theoretical rather than practical purposes are to be served, the principles on which it depends should be con- formable to the strictest theoretical rules of structure. A consideration of the fruit, without reference to the ovary, necessarily induces a degree of uncertainty as to the real nature of the fruit ; the abortion and obliteration to which almost every part of it is more or less subject, often disguising it to such a degree that the most acute carpologist would be unable to determine its true structure, from an examination of it in a ripe state only. In simple fruits are stationed those forms in which the ovaries are multiplied so as to resemble a compound fruit in every respect except their cohesion, they remaining simple. But, as the passage which is thus formed from simple to compound fruits is deviated from materially when the ovaries are placed in more than a single series, I have found it advisable to constitute a particular class of such, under the name of aggregate fruit. Care must be taken not to confound these with the fourth class containing collective fruits, as has been done by more carpologists than one. While the true aggregate fruit is produced by the ovaries of a single flower, a collective fruit, if aggregate, is produced by the ovaries of many flowers ; a most important difference. As the pericarp is necessarily much affected by the calyx when the two adhere so as to form a single body, it is indispensable, if a clear idea is to be attached to the genera of carpology, that inferior and superior fruits should not be confounded under the same name : for this reason I have in all cases founded a distinction upon that character. In order to facilitate the knowledge of the limits of the genera of carpology, the following analytical table will be found convenient for reference. It is succeeded by the characters of the genera in as much detail as is necessary for the perfect understanding of their application. 16 AUTHOR S METHOD. [BOOK I. CLASS I. Fruit simple. APOCARPI. One- or two-seeded : Membranous, Dry and bony, Fleshy externally, bony internally, Many-seeded : Dehiscent : One-valved, Two-valved, Indehiscent, UTRICULUS. ACH^NIUM. DRUPA. FOLLICULUS. LEGUMEN. LOMENTUM. CLASS II. Fruit aggregate. AGGREGATI. Ovaria elevated above the calyx : Pericarpia distinct, .... ET^RIO. Pericarpia cohering into a solid mass, . . . SYNCARPIUM. Ovaria enclosed within the fleshy tube of the calyx, . CYNARRHODUM. CLASS III. Fruit compound. SYNCARPI. Sect. 1. Superior : A. Pericarpium dry externally : Indehiscent : One-celled, . . . . CARTOPSIS. Many-celled : Dry internally : Apterous, . . . CARCERULUS. Winged, .... SAMARA. Pulpy internally, . . . AMPHISARCA. Dehiscent : By a transverse suture, . . . PYXIDIUM. By elastic cocci, . . . REGMA. By a longitudinal suture, . . . CONCEPTACULUM. By valves : . Placentae opposite the lobes of the stigma : Linear, . . . . SILT QUA. Roundish, . . . SILICULA. Placentae alternate with the lobes of the stigma : Valves separating from the replum, CERATIUM. Replum none, . . . CAPSULA. B. Pericarpium fleshy : Indehiscent : Sarcocarpium separable, . . . HESPERIDIUM. Sarcocarpium inseparable, . . . NUCULANIUM. Dehiscent, ..... TRYMA. Sect. 2. Inferior : A. Pericarpium dry : Indehiscent : Cells two or more, . . . . CREMOCARPIUM. STRUCTURE.] AUTHOR S METHOD. 17 Cell one : Surrounded by a cupulate involucrum, Destitute of a cupula, . . Dehiscent or rupturing, B. Pericarpiura fleshy : Epicarpium hard : Seeds parietal, . . . Seeds not parietal, Epicarpium soft : Cells obliterated, or unilocular, Cells distinct, .... CLASS IV. Collective fruits. ANTHOCARPI. Single : Perianthum indurated, dry, . . . Perianthum fleshy, ..... Aggregate : Hollow, .... . . Convex : An indurated amentum, A succulent spike, . . . 136 GLANS. CYPSELA. DIPLOTEGIA. PEPO. BALAUSTA. BACCA. POMUM. DlCLESIUM. SPHALEROCAR- P1UM. SYCONUS. STROBILUS. SOROSIS. 143 144 13(>. Syncarpous Capsule of Euonjmus. 137. Apocarpous Capsule of Nigella. 138. Legumen. 139. Legumen with the two valves opened. 140, Folliculus. 141. Conceptaculum, or Double Folliculus. 142. Apocarpous Capsule of Delphinium. 143. Capsule of Lychnis. 144. Capsule of Lychnis cut through, and showing the free central placenta. CLASS I. Fruit simple. APOCARPI. Ovaria strictly simple ; a single series only produced by a single flower. I. UTRICULUS, Gartner. (Cystidium, Link.) One-celled, one- or few-seeded, superior, membranous, frequently dehiscent by a transverse incision. This differs from the pyxidium in texture, being strictly simple, i. e. not proceeding from an ovarium with obliterated dissepiments. Example. Amaranthus, Chenopodium. VOL. II. C 18 AUTHOR'S METHOD. [ROOK i. II. ACH^NIUM. ( Akenium, of many ; Spermidium ; Xylodium, Desv. ; The- cidium, Mirb. ; Nux, Linn.) One-seeded, one-celled, superior, indehiscent, hard, dry, with the integu- ments of the seed distinct from it. Linnaeus includes this among his seeds, denning it " semen tectum epider- mide ossea." I have somewhere seen it named Spermidium ; a good term if it were wanted. M. Desvaux calls the nut of Anaoardium a Xylodium. Examples. Lithospermum, Borago. III. DRUPA. Drupe, fig. 165. One-celled, one- or two-seeded, superior, indehiscent, the outer coat (nau- cum) soft and fleshy, and separable from the inner or endocarpium (the stone), which is hard and bony ; proceeding from an ovarium which is perfectly simple. This is the strict definition of the term drupa, which cannot strictly be applied to any compound fruit, as that of Cocos, certain Verbenacese, and others, as it often is. Fruits of the last description are generally carcerules with a drupaceous coat. The stone of this fruit is the Nux of Richard, but not of others. Examples. Peach, Plum, Apricot. IV. FOLLICULUS. Follicle. (Hemigyrus, Desvaux ; Plopocarpium, Desv.) fig. 141. One-celled, one- or many-seeded, one-valved, superior, dehiscent by a suture along its face, and bearing its seeds at the base, or on each margin of the suture. This differs from the legumen in nothing but its having one valve instead of two. The Hemigyrus of Desvaux is the fruit of Proteacea?, and differs from the follicle in nothing of importance. When several follicles arc in a single flower, as in Nigella and Delphinium, they constitute a form of fruit called Plopocarpium by Desvaux, and admitted into his Etserio by Mirbel. Examples. Pseonia, Banksia, Nigella. V. LEGUMEN. Pod. (Legumen, Lvtin. ; Gousse, Fr.) fig. 138, 139. One- celled, one- or many-seeded, two-valved, superior, dehiscent by a suture along both its face and its back, and bearing its seeds on each margin of the ventral suture. This differs from the follicle in nothing except its dehiscing by two valves. In Astragalus two spurious cells are formed by the projection inwards of either the dorsal or ventral suture, which forms a sort of dissepi- ment ; and in Cassia a great number of transverse diaphragms (phragmata) are formed by projections of the placenta. Sometimes the legumen is indehis- cent, as in Cathartocarpus, Cassia fistula, and others; but the line of dehiscence is in such species indicated by the presence of sutures. When the two sutures of the legumen separate from the valves, they form a kind of frame called replum, as in Carmichaelia. Examples. Bean, Pea, Clover. VI. LOMENTUM. (Legumen lomentaceum, Rick.) Differs from the legumen in being contracted in the spaces between such seed, and there separating into distinct pieces; or indehiscent, but divided by STRUCTURE.] AUTHORS METHOD. 10 internal spurious dissepiments, whence it appears at maturity to consist of many articulations and divisions. Example. Ornithopus. 148 1 45. Samara. 146. Capsule of Rhododendron. 147. Capsule of Rhododendron divided across. 148. Capsule of Staphylea. 149, 150. Cypsela of Composite. 151. Capsule of Aristo- lochia. 152. Capsule of Aristolochia cut across. 153. Capsule of Staphylea cut across. CLASS II. Fruit aggregate. AGGREGATI. Ovaria strictly simple ; more than a single series produced by each flower. VII. ET^RIO, Mirb. (" Polychorion, Mirb ;" Polysecus, Desvaux ; Amalthea, Desv.; Erythrostomum, Desvaux.) fig. 163. Ovaries distinct; pericarpia indehiscent, either dry upon a dry receptacle, as Ranunculus, dry upon a fleshy receptacle, as Strawberry, or fleshy upon a dry receptacle, as Rubus. The last is very near the syncarpium, from which it differs in the ovaria not coalescing into a single- mass. It is Desvaux's Erythrostoroum. This term is applied less strictly by M. Mirbel, who admits into it dehiscent pericarpia, not placed upon an elevated receptacle, as Delphinium and Peeonia; but the fruit of these plants is better understood to be a union of several follicules within a single flower. If there is no elevated receptacle, we have Desvaux's Amalthea. The parts of an Eteerio are Achenia. Examples. Ranunculus, Fragaria, Rubus. VIII. SYNCARPIUM. (Syncarpium, Rich. ; Asimina, Desv.) Ovaries cohering into a solid mass, with a slender receptacle. Examples. Anona, Magnolia. IX. CYNARRHODUM. (Cynarrhodum, Oflicin. Desvaux.) Ovaries distinct; pericarpia hard, indehiscent, enclosed within the fleshy tube of a calyx. Examples. Rosa, Calycanthus. c 2 AUTHOR S METHOD. 155 156 [Uf'OK I. 159 163 160 161 158 157 154. Pyxidium of Anagallis. 155. Cremocarpium of Apiaceas. 156. Cremocarpium of Apiaceae cut across. 157. Siliqua of Cruciferae. 158. Siliqua of Cruciferae with the valves separating. 159. Siliqua of Cruciferae cut across. 160. Cremocarpium of Apiacese. 161. Cremocavpium of A piacese with the halves separating from their axis. 162. Dacca. 163. Etasrio of Rubus. 164. Etaerio of Boraginaceae. CLASS III. Fruit compound. SYNCARPI. Ovaria compound. Sect. 1. Fruit superior. A. Pericarpium dry. X. CARYOPSIS. (Cariopsis, Rich. ; Cerio, Mirb.) One-celled, one-seeded, superior, indehiscent, dry, with the integuments of the seed cohering inseparably with the endocarpium, so that the two areundis- tinguishable; in the ovarium state evincing its compound nature by the pre- sence of two or more stigmata; but nevertheless unilocular, and having but one ovulum. Examples. Wheat, Barley, Maize. XI. REGMA, Mirb. (Elaterium, Rich. ; Capsula tricocca, Z.) Three or more celled, few-seeded, superior, dry, the cells bursting from the axis with elasticity into two valves. The outer coat is frequently softer than the endocarpium or inner coat, and separates from it when ripe ; such regmata are drupaceous. The cells of this kind of fruit are called cocci. Euphorbia. XII. CARCERULUS, Mirb. (Dieresilis, Mirb.; Coenobio, Mirb.; Synochorion, Mirb. ; SterJgmum, Desvaux ; Microbasis, Desvaux; Polexostylus, Mirb. ; Sarcobasis, Dec., Desv.; Baccaularius, Desv.) Many-celled, superior : cells dry, indehiscent, few-seeded, cohering by a common style round a common axis. From this the Dieresilis of Mirbel does not differ in any essential degree. The same writer calls the fruit of Labi- atee (fi(j. 162.), which Linneeus and his followers mistake for naked seeds, STRUCTURE.] AUTHOR^ METHOD. 21 Coenobio: it differs from the Carcerulus in nothing but the low insertion of the style into the ovaria, and the distinctness of the latter. Examples. Tilia, Tropceolum, Malva. XIII. SAMARA, G:3 Sometimes the gland is solitary, and quite naked above, as in the common oak; sometimes there is more than one completely enclosed in the cupule, as the beech and sweet chesnut. Examples. Quercus, Corylus, Castanea. XXV. CYPSELA. (Akena, NecJcer ; Akenium, Kick.; Cypsela, Mirb.; Stepha- noum, Deav.) fig. 149, 150. One-seeded, one-celled, indehiscent, with the integuments of the seed not cohering with the endocarpium ; in the ovarium state evincing its compound nature by the presence of two or more stigmata; but nevertheless unilocular and having but one ovulum. Such is the true structure of the Achenium; but as that term is often applied to the simple superior fruits, called Nux by Linnaeus, I have thought it better, in order to avoid confusion, to adopt the name Cypsela. Examples. All Composites. XXVI. CREMOCARPIUM. (Cremocarpium, Mirb.; Polakenium, or Pentake- nium, Rich.; Carpadelium, Desv.) fig. 155, 160, 161. Two- to five-celled, inferior; cells one-seeded, indehiscent, dry, perfectly close at all times; when ripe separating from a common axis. M. Mirbel confines the application of cremocarpium to Umbelliferse: but it is better to let it apply to all fruits which will come within the above definition. It will then be the same as Richard's Polakenium, excluding those forms in which the fruit is superior. The latter botanist qualifies his term Polakenium according to the number of cells of the fruit: thus when there are two cells it isdiakenium, three tridkenium, and so on. M. De Candolle calls the half of the fruit of Umbelliferse mericarp. Examples. Umbellifers, Aralia, Galium. XXVII. DIPLOTEGIA. (Diplotegia, Desv.) One- or many-celled, many-seeded, inferior, dry, usually bursting either by pores or valves. This differs from the capsule only in being adherent to the calyx. Examples. Campanula, Leptospermum. B. Pericarpium fleshy. XXVIII. POMUM. Apple, or Pome. (Melonidium, Rich.; Pyridium, Mirb.; Pyrenarium, Desvaux ; Antrum, Mcench.) fig. 167. Two or more celled, few-seeded, inferior, indehiscent, fleshy; the seeds dis- tinctly enclosed in dry cells, with a bony or cartilaginous lining, formed by the cohesion of several ovaria with the sides of the fleshy tube of a calyx, and sometimes with each other. These ovaria are called Parietal by M. Richard. Some forms of Nuculanium and this differ only in the former being distinct from the calyx. Examples. Apple, Cotoneaster, Crateegus. XXIX. PEPO. (Peponida, Rich.) One-celled, many-seeded, inferior, indehiscent, fleshy; the seeds attached to parietal pulpy placentae. This fruit has its cavity frequently filled at maturity 24 AUTHOR'S METHOD. [BOOK i. with pulp, in which the seeds are embedded; their point of attachment is, however, never lost. The cavity is also occasionally divided by folds of the placenta into spurious cells, which has given rise to the belief that in Pepo macrocarpus there is a central cell, which is not only untrue but impossible. Examples. Cucumber, Melon, Gourd. XXX. BACCA. Berry. (Bacca, L.\ Acrosarcum, Desvaux.) jig. 162. One or more celled, many-seeded, inferior, indehiscent, pulpy; the attach- ment of the seeds lost at maturity, when they become scattered in the substance of the pulp. This is the true meaning of the term berry; which is, however, often otherwise applied, either from mistaking nucules for seeds, or from a misapprehension of the strict limits of the term. Example. Ribes. XXXI. BALAUSTA. (Balausta, Officin. Rich.) Many-celled, many-seeded, inferior, indehiscent; the seeds with a pulpy coat, and attached distinctly to their placentae. The rind was called Malico- rium by Ruellius. Example. Pomegranate. CLASS IV. Collective Fruits. ANTHOCARPI. Fruit of which the principal characters are derived from the thickened floral envelopes. XXXII. DICLESIUM. (Dyclesium, Desvaux ; Scleranthum, Mcench ; Catacle- sium, Desvaux; Sacellus, Mirb.) Pericarpium indehiscent, one-seeded, enclosed within an indurated perian- thium. Examples. Mirabilis, Spinacia, Salsola. XXXIII. SPHALEROCARPUM. ( Sphalerocarpum, Desvaux; Nux baccata of authors.) Pericarpium indehiscent, one-seeded, enclosed within a fleshy perianthium. Examples. Hippophae, Taxus, Blitum, Basella. XXXIV. SYCONUS. (Syconus, Mirb.) A fleshy rachis, having the form of a flattened disk, or of a hollow receptacle? with distinct flowers and dry pericarpia. Examples. Ficus, Dorstenia, Ambora. XXXV. STROBILUS. Cone. (Conus, or Strobilus, Rich., Mirb. ; Galbulus, Gaertn. ; Arcesthide, Desvaux ; Cachrys, Fuchs ; Pilula, Pliny.) fig. 168. An amentum, the carpella of which are scale-like, spread open, and bear naked seeds; sometimes the scales are thin, with little cohesion; but they often are woody, and cohere into a single tuberculated mass. The Galbulus differs from the strobilus only in being round, and having the heads of the carpella much enlarged. The fruit of the Juniper is a Galbulus with fleshy coalescent carpella. Desvaux calls it Arcesthide. Example. Pinus. STRUCTURE.] THE SEED. XXXVI. SOROSIS. (Sorosis, Mirb.) A spike or raceme converted into a fleshy fruit by the cohesion, in a single mass, of the ovaria and floral envelopes. Examples. Ananassa, Morus, Artocarpus. 167 a \65b 1(55. a,Drupa; b, vertical section, section. 166. Glans. 167. a, Pomum; 6, horizontal 168. Strobilus. 15. Of the Seed. The seed is a body enclosed in a pericarp, is clothed with its own integuments, and contains the rudiment of a future plant. It is the point of development at which vegetation stops, and beyond which no increase, in the same direction with itself, can take place. In a young state it has already been spoken of under the name of ovule ; to which I also refer for all that relates to the insertion of seeds. That side of a seed which is most nearly parallel with the axis of a compound fruit, or the ventral suture or sutural line of a simple fruit, is called the face, and the opposite side the back. In a compound fruit with parietal placentae, the placenta is to be considered as the axis with respect to the seed ; and that part of the seed which is most nearly parallel with the placenta, as the face. Where the raphe is visible, the face is indicated by that. When a seed is flattened lengthwise it is said to be com- pressed, when vertically it is depressed; a difference which it is of importance to bear in mind, although it is not always easy to ascertain it : for this purpose it is indispensable that the true base and apex of the seed should be clearly 26 HILUM APEX TESTA. [BOOK i. understood. The base of a seed is always that point by which it is attached to the placenta, and which receives the name of hilum ; the base being found, it would seem easy to deter- mine the apex, as a line raised perpendicularly upon the hilum, cutting the axis of the seed, ought to indicate the apex at the point where the line passes through the seed-coat ; but the apex so indicated would be the geometrical, not the natural apex : for discovering which with precision in seeds, the natural and geometrical apex of which do not correspond, another plan must be followed. If the skin of a seed be carefully examined, it will usually be found that it is com- posed in great part of lines representing rows of cellular tissue, radiating from some one point towards the base, or, in other words, of lines running upwards from the hilum and meeting in some common point. This point of union or radiation is the true apex, which is not only often far removed from the geometrical apex, but is sometimes even in juxta- position with the hilum, as in mignionette : in proportion, therefore, to the obliquity of the apex of the seed will be the curve of its axis, which is represented by a line passing through the whole mass of the seed from the base to the apex, accurately following its curve. If the lines above referred to are not easily distinguished, another indication of the apex sometimes resides in a little brown spot or areola, hereafter to be mentioned under the name of chalaza. The integuments of a seed are called the testa ; the rudi- ment of a future plant the embryo (Plate VI. fig. 1. b, &c.) ; and a substance interposed between the embryo and the testa, the albumen (fig. 1. «, 5. «, &c.) The testa, called also lorica by Mirbel, perisperm and episperm by Richard, and spermoderm by De Candolle, consists, according to some, like the pericarp, of three portions ; viz., 1. the external integument, tunica externa of Willdenow, testa of De Candolle ; 2. the internal integument, tunica interna of Willdenow, endopleura of De Candolle, hilofere and legmen of Mirbel; and 3., of an intervening substance an- swering to the sarcocarp, and called sarcoderm by De Can- dolle : this last is chiefly present in seeds with a succulent STRUCTURE.] INTEGUMENTS OF THE SEED. 27 testa, and by many is considered a portion of the outer integument, which is the most accurate mode of under- standing it. 172 175 178 184 183 186 182 172. Seed of a Garden Bean. 173. The same, after germination has just begun, and the testa is thrown off. 174. Fruit of Mirabilis Jalapa, with the embryo commencing the act of ger- mination by protruding the radicle. 175. The same, disentangled from the pericarp, and become a young plant. 176. A section of the seed of Sterculia, with the embryo inverted in the midst of albumen. 177. The embryo of Pinus, taken out of the seed, to show its nume- rous cotyledons. 178. The same, after germination has advanced a little. 179. Seed of < ).\alis, with the revolute elastic epidermis of the testa. 180. Seed of Salsolaradiata divided vertically, and showing the annular dicotyledonous embryo, rolled round the albumen. 181. Embryo of the same, taken out of the seed. 182. Section of the seed of Cyclamen, showing the t.ansverse embryo lying in the midst of albumen. 183. Section of the fruit of j& Grass, with the lateral embryo at the base. 184. The same, with germination just beginning. 185. The same, after germination is completed, and the monocotyledonous embryo become a young plant. 186. Section of seed of Scirpus, with germination begun ; the solitary coty- ledon is retained within the testa, the plumule and radicle are growing beyond it. 187. Section of a Grass seed germinating ; the plumula is directed upwards like a slender horn ; the cotyledon is at its base, adhering to the albumen. 188. Seed of Commelina germinating ; the cauliculus is protruded, is emitting radicles from its end, and has pushed aside the lid called embryotega. According to Schleiden, the integuments of the seed expe- rience many changes during the period of ripening, so that their original number can rarely be recognised. They are sometimes all consolidated so as to form but one ; or they are broken up into many layers, having no relation to the original number of integuments. In Menyanthes, which has but one integument of the ovule, the seed appears to have two, because of the separation and lignification of the epidermis of that integument ; and in Canna there are five layers of tissue resembling integuments, although the ovule has not even one complete integument. In the case of Spurgeworts, Rock Roses (Cistacese) and Daphnads, a peculiar process takes place ; 28 OUTER INTEGUMENT. [BOOK i. namely, upon the seed becoming ripe the external integument is gradually absorbed, until nothing but a thin membrane is left, usually described as epidermis testa, or in the Spurge- worts (Euphorbiacese) it has been given as aril ; and, on the other hand, the actual modified epidermis testae has also been described as the aril, for instance, in the Oxalids. The cellular tissue of the integuments of the seed is very often reticulated. In most Bignoniads, and many other plants, the epidermis is in this state, and in Casuarina there is a layer of spiral vessels below the epidermis, very thin and delicate, and extremely minute. In Swietenia febrifuga there is, below the epidermis, a thick layer of large spiral cells, which have little cohesion with each other, and which form a multitude of rather large fusiform sacs lying confusedly (?) ; this is the most complete case of spiral cells in seeds with which I am acquainted, and it is accompanied by the presence of a bundle of numerous slender spiral vessels in the raphe. The outer integument is either membranous, coriaceous, crustaceous, bony, spongy, fleshy, or woody; its surface is either smooth, polished, rough, or winged, and sometimes is furnished with hairs, as in the cotton and other plants, which, when long, and collected about either extremity, form what is called the coma (sometimes also, but improperly, the pappus) . It consists of cellular tissue disposed in rows, with or without bundles of vessels intermixed : in colour it is usually of a brown or similar hue : it is readily separated from the inner integument. In Maurandya Barclay ana it is formed of reticulated cellular tissue; in Collomia linearis, some Salvias and others, it is caused by elastic spirally twisted fibres enveloped in mucus, and springing outwards when the mucus is dissolved. In the genus Crinum it is of a very fleshy succulent character, and has been mistaken for albu- men, from which it is readily known by its vascularity. Ac- cording to Brown, a peculiarly anomalous kind of partition, which is found lying loose within the fruit of Banksia and Dryandra, without any adhesion either to the pericarp or the seed, is a state of the outer integument ; it is said that in those genera the inner membrane (secundine) of the ovule is, before fertilisation, entirely exposed, the primine being reduced STRUCTURE.] INNER INTEGUMENT. 29 to half, and open its whole length ; and that the outer mem- branes (primines) of the two collateral ovules, although originally distinct, finally contract an adhesion by their corre- sponding surfaces, and together constitute the anomalous dissepiment. But it may be reasonably doubted whether the integument here called secundine is not primine, and the supposed primine arillus. In Sir Thomas Mitchell's curious Bottle Tree, (Delabechea) the primine is brittle like an egg- shell, and separates spontaneously from the bony secundine, which eventually cracks the apex of the primine and falls through the hole thus formed. The primines, which are held together by entangled hairs, remain in the follicle long after the secundines and their contents have dropped out. The inner membrane (secundine) of the ovule, however, in general appears to be of greater importance as connected with fecundation, than as affording protection to the nucleus at a more advanced period. For in many cases, before impreg- nation, its perforated apex projects beyond the aperture of the testa, and in some plants puts on the appearance of an obtuse, or even dilated, stigma ; while in the ripe seed it is often either entirely obliterated, or exists only as a thin film, which might readily be mistaken for the epidermis of a third membrane, then frequently observable. The apex of the original papilla, which developes itself as nucleus, varies exceedingly in its size in proportion to the entire ovule, if examined in the different families. It often forms a long and nearly cylindrical body, as in Loasa and Pedicularis; in many cases it is shorter, so that that portion of the ovule in which no distinction has taken place between nucleus and integu- ment (the whole being like a fleshy distended stalk) is by far the more predominant, as in all Composites, Canna, Phlox, Polemonium. " The third coat (tercine) is formed by the proper mem- brane or skin of the nucleus, from whose substance in the unimpregnated ovule it is never, I believe, separable, and at that period is very rarely visible. In the ripe seed it is dis- tinguishable from the inner membrane only by its apex, which is never perforated, is generally acute and more deeply coloured, or even sphacelated." 30 VITELLUS — HILUM. [BOOK j. Mirbel has, however, justly remarked that the primine and the secundine are, in the seed, very frequently confounded ; and that, therefore, the word testa is better employed, as one which expresses the outer integument of the seed without reference to its exact origin, which is practically of little im- portance. The tercine is also, no doubt, often absent. He observes that these mixed integuments often give rise to new kinds of tissue ; that in Phaseolus vulgaris the testa consists, indeed, of three distinct layers, but of those the innermost was the primine ; and that the others, which represent nothing that pre-existed in the ovule, have a horny consistence, and are formed of cylindrical cellules, which elongate outwards, in the direction from the centre to the circumference. And this is probably the structure of the testa of many Leguminous plants. De Candolle states, that it sometimes happens that the endo- pleura thickens so much as to have the appearance of albumen, as in Cathartocarpus fistula, and that in such a case, it is only to be distinguished from albumen by gradual observation from the ovule to the ripe seed. This is, however, denied by Schleiden. One of the innermost integuments is occasionally present in the form of a fleshy sac, interposed between the albumen and the embryo, and enveloping the latter. It is what was called the vitellus by Gsertner, and what Eichard, by a singular prejudice, considered a dilatation of the radicle of the embryo : to his macropodal form of which he referred the embryo of such plants. Instances of this are found in Nym- phseat and its allies, and also in Gingerworts, Peppers, and Saururus. Brown, who first ascertained the fact, considers this sac to be always of the same nature and origin, and to be the sac of the amnios. The end by which the seed is attached to the placenta is called the hilum or umbilicus (Plate VI. fig. 5. c, 17. e, 11. c, &c.) ; it is frequently of a different colour from the rest of the seed, not uncommonly being black. In plants with small seeds it is minute, and recognised with difficulty; but in some STRUCTURE.] CARUNCUL^ MICROPYLE CHALAZA. 31 it is so large as to occupy fully a third part of the whole surface of the seed, as in the Horsechesnut, Sapotads, and others. Seeds of this kind have been called nauca, by Gart- ner. In grasses, the hilum is indicated by a brownish spot situated on the face of the seed, and is called by Richard spilus. The centre of the hilum, through which the nourish- ing vessels pass, is called by Turpin the omphalodium. Some- times the testa is enlarged in the form of irregular lumps or protuberances about the umbilicus; these are called strophioloB or caruncula ; and the umbilicus, round which they are situated, is said to be strophiolate or carunculate. Mirbel has ascertained that in Euphorbia Lathyris the strophiole is the fungous foramen of the primine ; and it is probable that such is often the origin of this tubercle : but at present we know little upon the subject. The foramen in the ripe seed constitutes what is called the micropyle : it is always opposite the radicle of the embryo ; the position of which is, therefore, to be determined without dissection of the seed, by an inspection of the micropyle, — often a practical convenience. In some seeds, as the Asparagus, Commelina, and others (fg. 188.), there is a small callosity at a short distance from the hilum : this callosity gives way like a lid at the time of germination, emitting the radicle, and has been named by Gartner the embryotega. At the apex of the seed, in the Orange and many other plants, may be perceived upon the testa a small brown, spot, formed by the union of certain vessels proceeding from the hilum : this spot is the chalaza (Plate VI. fig. 11. b}. In the orange it is beautifully composed of dense bundles of spiral vessels and spiral ducts, without woody fibre. The vessels which connect the chalaza with the hilum constitute a parti- cular line of communication, called the raphe : in most plants this consists of a single line passing up the face of the seed ; but in many Citronworts (Aurantiacese) and Guttifers it ramifies upon the surface of the testa. 32 KAPHE ARIL. [BOOK i. The raphe is always a true indication of the face of the seed ; and it is very remarkable that the apparent exceptions to this rule only serve to confirm it. Thus, in some species of Euonymus in which the raphe appears to pass along the back, an examination of other species shows that the ovules of such species are in fact resupinate ; so that, with them, the line of vascularity representing the raphe is turned away from its true direction by peculiar circumstances. In reality, the chalaza is the place where the secundine and the primine are connected ; so that in orthotropal seeds, or such as have the apex of the nucleus at the apex of the seed, and in which, consequently, the union of the primine and secundine takes place at the hilum, there can be no apparent chalaza, and consequently no raphe : the two latter can only exist as distinct parts in anatropal or amphitropal seeds, where the base of the nucleus corresponds to the geometrical apex of the seed. Hence, also, there can never be a chalaza without a raphe, nor a raphe without a chalaza. It is usual to speak of the aril of plants (fiys. 189 and 190.) when speaking of the ovule; but it more properly comes under consideration along with the ripe seed. As a general rule, it may be stated, that everything proceeding from the placenta, and not forming part of the seed, is refer- able to the aril. Even in plants like Hibbertia volubilis and Euonymus europseus, in which it is of unusual dimensions, STRUCTURE.] TRUE AND FALSE ARILS. 33 it is scarcely visible in the unimpregnated ovary ; aiid it is stated by Brown, that he is not acquainted with any case in which it covers the foramen of the testa before impregnation. The term aril has been misapplied in many cases to the testa, as in Orchids ; and even to a pair of opposite confluent bracts, as in Carex : of these errors, the former arose from imperfect observation, the latter from ignorance of the fundamental principles of Organography. The true nature of the aril has been carefully and skilfully investigated by M. Planchon, whose memoir throws so much light upon general structure, that I reproduce it with very little abridgment, although at great length. A. Difference between True and False Arils. — We will first examine an aril which possesses all the characters assigned to it by Richard ; we will follow its developments, its relations to the ovule and the seed, and we shall be then able to distinguish it from all the organs with which it is at present confounded. Let us take the genus Passiflora. On cutting the ovary of a young flowerbud of P. triloba, we find numerous conical tumours, which are rudimentary ovules, arranged on three parietal placentae. In a bud a little more advanced the tumours are longer, their upper part is slightly hooked, and a little below their point two circular rings, close to each other, are found in relief. In these two rings the two integuments of the ovule, as yet scarcely developed, can be distinguished ; the point of each tumour is a small nucleus, the base of which is scarcely covered by its integuments, and the hooked curvature of each of them is a commencement of anatropy. A little later, just before expansion, the anatropy is com- plete ; each ovule is become ovoid ; the two rings are extended into integuments which are still open at the top ; the inner one (secundine, Mirb.) projecting beyond the outer (primine, Mirb.), and the nucleus projecting through the opening of the inner, which, however, conceals its (the nucleus) base. In the ovary of an expanded flower, the top* of the ovule is * In this essay, by the top of the ovule is meant the place where the micropyle is found, and where the point of the nucleus ends ; hence it is clear that in anatropal and campylotropal ovules, the top will fee very near the base if we take the latter to mean not the chalaza, but the hilum. VOL. II. D 34 ARIL OF PASSIFLORA. [BOOK i. elongated and curved down on the point of attachment so as to rest on the umbilical cord a little above the hilum ; neither the opening of the internal integument nor the point of the nucleus are to be any longer seen ; the external integument has covered both, in consequence of its rapid growth. At the same time, however, a very remarkable development has begun on the umbilical cord. At the narrow end of this organ, around the point at which it joins the ovule, we find a circular rim which on one side surrounds obliquely the base of the raphe, and on the other is interposed between the umbilical cord and the ovule. The edges of this ring soon extend and form a sort of membranous sleeve, the free edge of which expands around the hilum. The evolution of the ovules of Passiflora triloba stops here, and I have not been able to follow the subsequent developments because its ovaries are constantly abortive in the hot-houses at Mont- pellier. Other allied species will, however, suffice. After fecundation each ovule grows rapidly; the membranous sleeve expands more and more, and that part of its edge between the umbilical cord and the ovule extends towards the exostome, and covers the top of the young seed as with a hood. The latter becomes longer by degrees, and at last the ovule, now a seed, is completely concealed in a loose fleshy sac, attached to the border of the hilum and having a large opening next the chalaza. In short, the annular rim, the mem- branous sleeve, the hood which covers the top of the ovule, and the open sac at its end, which completely conceals the seed, are all one and the same organ in different stages of development. From the above it appears that this organ is formed after fecundation ; that it is an expansion of the umbilical cord ; that it does not adhere to the seed except at the hilum ; and lastly, that it is completely open at the point opposite its insertion : in this case I do not hesitate, in accordance with the usual terminology, to call the organ a true aril. If all these characters united do not in this case leave any doubt as to the nature of this envelope, it is not so much owing to their real value as to our having followed them in all the stages of the development of the ovule. These characters become dtfubtful and insufficient when we apply STRUCTURE.] ARILLODE OF EUONYMUS. 35 them to the study of a ripe seed, as is proved by the following remarkable instance. Nothing is more like the aril of Passionflowers than the so-called envelope found on the seeds of Euonymus ; it is a suc- culent, loose, folded sac covering the seed in a greater or less degree, which does not adhere to it except round the hilum and at the origin of the raphe ; the sac is, in short, more or less open next the chalaza. Let us add that this envelope is not formed until after fecundation, a ad we shall have an appa- rent identity between this organ and the aril of Passionflowers. We shall, however, see that this identity is apparent only. Let us take Euonymus latifolius ; in its ovary we find two globular ovules suspended parallel to one another at the inner angle of each cell a little below its top. About the time of expansion they become completely anatropal ; their outer integument covers the inner one and the nucleus ; the raphe, which is prominent, occupies in each of them the side opposite the periphery of the ovary, and the micropyle, on the contrary, is between the point of attachment and the interior angle of the cell at the top of the ovule. The umbilical cord is white, as the ovule also is next the hilum, but at its other end it is of a rosy colour which gradually extends over the whole seed. For some time after the fall of the petals and stamens the ovule grows, but does not undergo any external change. The edge of the exostome, however, soon thickens, and looks like a rim round its narrow opening, reminding one by its origin, its nature, and even a little by its form of the caruncula of Spurgeworts. This rim, however, grows, expands into a membrane at its edge, and, turning back next the base of the ovule, becomes a hemi- spherical cap which partly covers the latter, leaving however, at its origin, the micropyle uncovered. This expansion, lastly, increases its surface, draws its opening nearer and nearer the chalaza, and forms around the seed the succulent bag hitherto described as an aril. When I stated that this sac proceeded solely from the exostome, I have, perhaps, sacrificed exactness to clearness. As the hilum is very near the micropyle, the arilliform expan- sion starting from the edges of the latter would find the 36 ARILLODES. [BOOK i. funicle an obstacle to its extension, and ought, therefore, to have a break in its uniformity : but it is here, as it happens, that the expansion is thickest, and it even adheres, along part of its length, to the base of the raphe, so that it looks as if at this point it proceeded from the latter part. To explain this, we must admit there is a congenial junction between the expan- sion and the funicle. I ought, perhaps, to add, in order to clear up doubts, that in Euonymus it is very difficult to see the micropyle, when the ovule is considerably developed, because the false aril is folded round its opening, and so completely hides it : but by carefully pulling away the accessory envelope it is quite clear that it proceeds from the edges of the exostome.* We have seen, in the Passionflowers, an expansion deve- loping around the hilum and covering the exostome, by ex- tending over the whole ovule. The same fact, variously modified, is found in other plants. In Euonymus, on the contrary, no expansion arises and covers the exostome', but the edges of this opening expanding a little, turn back from the top towards the base of the ovule, and, developing in this direction, form around the latter a sac open next the chalaza. We shall find in other species, a similar expansion of the edges of the exostome produce very various excrescences on the ovule, which have generally been confounded with those of the umbilical cord. I have called the expansion of the umbilical cord in Passionflowers an Aril ; but this name will not apply to the envelope which as in Euonymus proceeds from the edges of the exostome. Similar productions are as common as true arils : I shall examine them in detail under the name of false Arils or of Arillodes. We may, indeed, say that the greatest number of the parts of a seed as yet considered as arils, will come into the new class. In short, the characters assigned to the true aril have been sufficient to distinguish it from the parts of the pericarp and from the integuments of the seed, whilst they are of no * L. C. Treviranus perfectly traced the developments of the false aril of Euonymus latifolius from the time that it half covered the seed ; and he would certainly have arrived at the truth had he traced the progress of this organ from its commencement. STRUCTURE.] HOW DISTINGUISHED FROM ARILS. 37 value in cases like that of Euonymus. From the preceding facts I draw the following conclusions, which will place this subject in a better light. The true aril, an accessory integument of the ovule, is developed round the hilum as the proper integuments are, and covers or would cover the exostome, if we suppose it extended over the whole of the ovule. The false aril (arillode} of Euonymus, &c., an expansion of the edges of the exostome, is often bent back around this opening, but always leaves it exposed. We can distinguish, even in the seed, the nature of an arilliform envelope, by the place of the micropyle which repre- sents the exostome of the ovule. If the micropyle is hidden by the envelope, or if it would be hidden, if the envelope were extended further, we have a true aril. But if, on the con- trary, the micropyle is not covered by the envelope and cannot be, even if the latter is extended, then we have a false aril like that of Euonymus. When an aril, true or false, forms around an anatropal seed a bag open at its extremity, it can be easily distinguished from a proper envelope, inasmuch as the latter is covered by the raphe, and its opening, the micropyle, is in a direction opposite to that of the arilliform sac. If the seed is orthotropal and we find a true aril, the opening of the latter is turned to the same side as the micro- pyle, i. e. towards the apex of the ovule ; in this case, of which I know of but one example, (Cytinus hypocystis), the aril is blended with the proper integuments of the seed. If, in an orthotropal seed there were an arillode in the form of a sac, it could not be confounded with either a true aril or with a proper integument, because its opening would be next the base of the seed on the side of the point of attachment. B. Of the True Aril — True arils, though they resemble each other in all essential points, are yet of extremely various forms and sizes. We see them, even in allied species, take every degree of extension from the annular rim, that hardly surrounds the base of the seed, to the sac that entirely covers it. These different states may be found in Dilleniads. 38 ARIL OF DILLENIADS AND SAMYDS. [BOOK i. If we take the anatropal ovule of Hibbertia volubilis, a little before the expansion of the flower, we find around its point of attachment a sort of circular thickening formed by its great umbilical cord. The edge of this thickening, at first at a tolerable distance from the exostome, continually approaches, and in the expanded flower nearly reaches this opening. I have not been able to trace the further evolution of the ovules; but it is certain that the expansion does not proceed much further, since, according to certain authors, the ripe seed of this species has only a very short arillary mem- brane at its base. In Tetracera, on the contrary, this organ is developed on the seeds as a membranous, coloured sac, which is inserted in a circle around the hiluni, and presents at its top a large opening. The free edge of this orifice is more or less slashed somewhat in the same way as a fimbriated petal. The enve- lope adheres to the hilum of the seed, when the latter is detached from the placenta, and completely covers the micro- pyle which is beneath it, by the side of the point of attach- ment, an essential character of a true aril. In a species of Tetracera from Java, I have seen the aril cover the seed completely : in other species it only partially covered the surface of the seeds. Other genera of the same natural order, as Candollea, Delima, Davilla, Pleuranda, &c., have, it is said, an aril very like that of Tetracera. In the genera Pachynema and Hemi- stemma, the aril is stated to be reduced to a cupule that receives the base of the seed only. The genera Samyda and Casearia, although in their general characters far removed from Dilleniads, have, however, an aril, with a large opening and deeply laciniated border. The seeds of these two genera are semi-anatropal, and only differ from those that are completely anatropal by the position of their point of attachment, which, instead of being quite close to the micropyle, is as far from it as from the chalaza. The raphe, very short in the first, only occupies the half of their length. These seeds are completely hidden by the arillary envelope, which inserted round the hilum, necessarily covers the micropyle, a character sufficient to indicate an aril. STRUCTURE.] OF TURNERADS. 39 Another very curious fact confirms this idea ; of the many ovules found on each placenta, there are very few that arrive at maturity, the rest become early abortive, but, nevertheless, remain at the side of the ripe seeds ; and, what is a very remarkable fact, even if they are dried and reduced in size as much as possible, their arils for all that become very large sacs. The latter are only a little smaller and not so much cut as the arils of the perfect seeds. This shows that the aril can grow independently of the ovule, just as in some fruits the pericarp continues to grow after the abortion of all the ovules. This observation, which I have made on a Samyda, has also been made by M. Cambessedes on the seeds of Casearia grandiflora. Knowing that the aril exists in the Samyds, we shall not be surprised to find it in an allied order, viz., that of Turnerads, where this organ, although it retains its cha- racters, is much modified in form. In a capsule of Turnera, the parietal placentae bear numerous anatropal seeds, which are nearly cylindrical, obtuse at the two ends, and slightly bent. An umbilical cord, which is rather slender, is inserted at a short distance from the micropyle, and gives rise, below its point of attachment, to a sort of membranous, transparent tongue, which applied, but not adhering to the ventral side of the seed, extends more or less according to the species, without reaching either the dorsal side or the base of the seed. Some people, deceived no doubt by an apparent resemblance between this tongue and that found on the seeds of Corydalis, have called the former a Strophiole, whereas this name applies to the latter only. The strophiole, indeed, is an excrescence of the integument, and has nothing to do with either the umbilical cord or with the micropyle ; and I shall show in the sequel that this is the case with the tongue of Corydalis. That of Turnera, 011 the contrary, belongs so little to the integument, that, when the seed is detached from the umbili- cal cord which remains fixed to the placenta, the membranous tongue is often found at the other extremity of the latter, and thus its arillary nature admits of no further doubt. This aril, which covers the seed incompletely, is found throughout the whole of Turnerads, if we can, by analogy, apply what 40 ARIL OF BIXADS. [BOOK r. we have seen in Turnera to what has been described in Piriqueta and Wormskioldia. We are led by natural affinities from Turnerads to Bixads, some genera of which possess the organ we are examining. In Bixa, for example, the numerous turbinate seeds of which are each attached to a long umbilical cord, we find a narrow discoid expansion, arising from the latter around the hilum, and which evidently represents a partially developed aril. The umbilical cords adhering to the placenta after the seeds have fallen resemble little nails, the heads of which are formed by the arillary expansion ; the connexion between these cords and the aril cannot be more clear than in this case. I have nothing more to add concerning the aril of Bixa ; but on the seeds of this genus there is another excrescence that merits our attention. These seeds are anatropal, with a deep furrow extending on their surface from the hilum to the chalaza, and inclosing the raphe. The latter lying in a superficial pulpy layer of the external integument, only becomes visible a little below the point where the vessels that compose it expand into the chalaza on the inner integument. In this small portion of its length that can be seen, it forms on the seed an elevated, hard, shining line, expanded at its end into a circular, lobed, crustaceous, shiny disc, which is only attached to the seed by its centre, like a flattened button with a very short stem. Some physiologists see in the raphe a portion of the umbi- lical cord, which, completely free, when the ovule is ortho- tropal, adheres to the length of the latter, thus making it anatropal ; and they, perhaps, would explain the origin of these two discoid expansions, by looking upon them as two arils arising from the umbilical cord at two different periods ; the first formed, being developed around the hilum when the ovule was orthotropal, the point of its attachment is con- founded with the chalaza; the other, formed at the new point of attachment in the anatropal ovule : this point of attachment is separated from the former and from the cha- laza by the whole length of the raphe. These two expansions would be found on the seed, the first near the chalaza, the STRUCTURE.] EXCRESCENCES ON BIXADS, 41 second at the hilum, and the raphe between them would be a sort of internode intimately adhering to the integument of the ovule. This point of view I take to be more ingenious than correct; for I cannot conceive that a portion of the umbilical cord at first free, should be afterwards found im- bedded in the tissue of the ovulary leaf, under the epidermis, which is perfectly unbroken, and often under several crus- taceous layers of the integument. Besides, the raphe is generally a medial nervure which sends out along its entire length, lateral nervures, and which branches at its origin before reaching the chalaza. These facts prove that this part is not more independent of the exterior ovulary leaf than the midrib is of an ordinary leaf; and that it plays the part of a midrib with respect to the integument, and of an axis with respect to the more interior parts of the ovule ; but they farther prove that there is a congenial adherence and intimate blending between the axis and the nervure, just as on the bracts of the Lime tree (Tilia) the midrib is joined with the floral peduncle from its commencement. From the frequent examination of the passage from ortho- tropy to anatropy in ovules, I am convinced that the umbi- lical cord is never soldered to the ovulary leaf, and if I rightly understand M. De Mirbel, these observations accord with his. The axis of an orthotropal ovule continues in a straight line that of the umbilical cord; the vessels of the latter cross in a vertical direction the thickness of the exterior, to reach the interior integument. But one side of the ovule developing faster than the other, the interior integument is forced to incline to the funicle on the opposite side ; and then the vessels extending from the hilum to the chalaza traverse the exterior integument obliquely, and these two points coincide no longer. The hilum remaining fixed, the part of the ovule between it and the chalaza increases rapidly, separating the one from the other, thus forcing the vessels joining them to lengthen into a raphe, in the thickness itself of the testa. The point of attachment of the ovule, it will be seen, is not changed during this transformation; and we cannot admit the possibility of there being two opposite arils on one seed, since there is never but one hilum, and the aril 42 ARIL OF NYMPILEA ; [BOOK i. always proceeds from this point. We ought, then, to consider in Bixa only that discoid expansion which is around the point of attachment as an aril, while the opposite expansion must be looked upon only as an appendage of the integument. But to return to my subject, from which I have, perhaps, wandered too far, I find the aril, with all its characters, in the genus Nymphsea. The anatropal ovoid seeds of Nymphaea cserulea are entirely covered with a white membranous enve- lope, which is inserted round the hilum ; and being applied, but not adhering to the entire surface of the testa, has but a small opening next the chalaza. Below this envelope, which is a true arillary sac, we find on the side of the point of attachment a very distinct micropyle ; this sac has, therefore, been wrongly described as an epidermis of the proper integu- ment. This error would be dispelled by an examination of the seed ; but we find still stronger characters in the develop- ment of the ovules of another species of the same genus. If the ovary of Nymphsea alba is opened a little before the expan- sion of the flower, on no one of its numerous anatropal ovules is any trace of an accessory envelope to be found ; their exostome is also quite open to view. A simple rim found on the funicle immediately above the hilum, evidently indicates the origin of the membrane which, in Nymphsea cserulea, entirely conceals the seeds ; but at a later period, in the same ovules, the rim is extended into a hemispherical cap, crowning their summit and afterwards covering the entire seed. I have not been able myself to observe this transitory state of the aril of Nymphsea alba ; but I depend for the accuracy of my statement on De Mirbel's excellent observations on the ovule; than which I can have no better authority. We might expect to find some sort of aril on the seeds of Nuphar, which is very nearly allied to Nymphsea ; however, there is none ; the seeds of Nuphar lutea, for example, have no trace of any accessory membrane, either on their crusta- ceous integument, or on their micropyle, which is very visible. I need not state that this envelope does not exist on the seeds of Neluuibium. The amphitropal, lenticular seeds of Chamissoa nodiflora (Nat. Ord. Amaranths) have at their base a shallow STRUCTURE.] OP AMARANTHS. 43 furrow, which renders the seed slightly reniform. A white, circular membrane, evidently arising from the umbilical cord, is found fixed round the point of attachment at the bottom of the furrow ; passing beyond the latter the membrane covers the micropyle, but extends a very little on the surface of the testa. Here then again we have a true aril ; but we may be surprised to find this envelope in a genus lost, as it were, amongst a crowd of others which have no trace of this organ. In the anatropal and amphitropal seeds, to which our attention has as yet been directed, the distinction between the aril and proper exterior integument is quite plain. The latter, as I have before said, a true ovulary leaf, traversed by the raphe, with the nervures depending on it, forms a com- plete envelope, the orifice of which, scarcely visible (micropyle) is more or less near the hilum. The aril, on the other hand, often reduced to the dimensions of a rim or of an unilateral tongue, never has any nervures ; even when extending over the seed as a hood or sac, it presents a large opening on the side next the chalaza, opposite the micropyle. The same distinctive characters can be easily applied to campylotropal seeds, in which, instead of a raphe, there generally exists a vascular network in the external integument, and the micro- pyle is always close to the point of attachment. But these characters, though, when combined, of the utmost import- ance, have not taken separately the same comparative value between themselves. The position of the micropyle, generally determined by that of the radicle, furnishes a very steady character, when compared with the inverse direction of the opening in the aril. The presence of the raphe or of nervures in the proper integument is far from being so constant, and there exists a great number of seeds which have only one entirely cellular integument, whether it proceeds from the secundine, or from the very thin nucleus. If, in such seeds, we suspected an arillary envelope, the position of the micro- pyle or of the radicle, or, better still, the observation of their development, would resolve all doubts. But if we found a cellular envelope of doubtful nature, in an orthotropal seed with only one cellular integument, we could not then decide with certainty as to its nature, and we ought to remember 44 THE AE1L IS AN OVULARY LEAF. [BOOK i. that the proper and accessory envelopes of the seeds, like other parts of a plant, are confounded the one with the other by insensible degrees ; this I have observed in the seeds of the very anomalous Cytinus hypocistis. "We have hitherto seen in the aril an expansion of the umbilical cord, which, the ovule being considered a bud, is its external leaf. Depending on the retrograde manner in which the integuments of the ovule form, the aril appears very late on the outside of the other envelopes of the ovule, and is the last appendage sent out by the exhausted axis. This feeble production, inclosing no vessels even in its highest state of development, is found immediately below and on the outside of the primine, the most perfect leaf of the ovule, just as the pieces of the disc, the most rudimentary append- ages of the floral axis, are found immediately surrounding the carpels, the most vigorous and perfect organs of the whole flower. But M. Aug. de St. Hilaire, the learned and ingenious author of the idea that an aril was a leaf of the ovule, knew too much of vegetable organography not to see that this part, compared in a series of species, insensibly lost its characters of an appendage, and at last became confounded with the simple layer often found at the summit of the umbi- lical cord ; just as the pieces of the disc, which are seldom petaloid, and are more generally represented by little scales, are in many cases nothing but simple projections of the receptacle, which at last disappear altogether. I shall show that the aril passes in allied plants through this series of gradual alterations, and I shall trace it from its usual state until it will be impossible to mark the limit between it and the thickened extremity of the umbilical cord. On the seeds of many Soapworts (Sapindacese) we find the organ in question ; whilst on others no trace of it is discover- able. In an undetermined species of Cupania, for example, the great short funicle supporting each seed expands around the hilum into a circular membranous edge, which is a true cup- shaped aril leaving but a small portion of the testa uncovered. The seeds of Paullinia and Schmidelia are only half covered by an analogous cup, the free portion of which is very narrow and inserted around a large hilum, without the limit STRUCTURE.] FALSE ARILS. 45 between the aril and the funicle being marked by any contraction. This expansion is again found still narrower and less distinct from the umbilical cord in the genus Serjania; and, lastly, in some species of Cardiospermum (C. Halicacabum) we find nothing but the funicles thickened at their top without any trace of a free edge, whilst in others, with a less extended umbilical scar, a funicular expansion is seen which can be nothing but a rudiment of the aril. In these cases, of which I could furnish more in the same natural order, care must be taken not to confound the free part of the expansion of the umbilical cord, which alone is the aril, with any expansion of the same cord which, being extended over the seed, adheres to the testa, and which would only cover the surface of the hilum. It is in consequence of inattention to this character of the aril, viz., its non-adherence to the testa, that this name has been given to the remarkable expansion of the top of the funicle found in beans, peas, and other Leguminous plants, as well as to umbilical scars when large and coloured, as in Cardio- spermum, from which they have taken their generic name. The term aril does not apply to the thin fleshy lobed plate which, in Connarus and Omphalobium, is extended on the surface of the seed from the beginning of the raphe to about the middle of its length, and which is independent of the umbilical cord and of the hilum, being a parenchymatous layer of the testa to which it is intimately joined. Now that we have gone through the principal modifications of the aril, it will be easy to recognise those appendages of the seed which have been wrongly called by this name, and which we shall next review in detail. C. Of the False Aril. — If there is on seeds any envelope of doubtful nature it is certainly that which we are now going to notice ; exterior with respect to the proper integuments, covering the exostome, and depending like the aril on the umbilical cord, it is distinguished from the aril, by important characters, and constitutes a very anomalous false aril. Perhaps, indeed, the name of false testa would be more applicable to it, in consequence of its crustaceous texture, 46 FALSE ARIL OF OPTJNTIA. [BOOK i. and because, being completely developed before the expansion of the flower, it has always been described, not as an aril, but as a true testa. How can one, indeed, avoid taking for a proper integument the exterior envelope of the seeds of Opuntia, a hard, thick, reniform stone bordered by an elevated rim, and presenting no trace of any opening even when free from the pulp with which it is covered ? It is, however, this very stone that I call a false aril or false testa, the origin and nature of which must be looked for in the early development of the ovules. Those of Opuntia vulgaris, composed in a very young flower-bud of an ovoid nucleus and of two open integu- ments, end in thick funicles, with which they are perfectly continuous. Each of the latter, originally nearly straight, is gradually bent into a semicircle, and approaching at. its base the point of the nucleus, forms a complete ring with the ovule. In that half of the ring which is lowest with respect to the ovule, arise, on the sides of the umbilical cord and at some distance from its base, two rather concave mem- branous expansions, which originate next the ovule and soon conceal the empty space comprised in the turn of the ring. The funicle and its two expansions then represent a sort of boat with a very large opening, and the cavity of which imper- fectly conceals the ovule, which gets deeper and deeper into it. The latter soon disappears ; the diameter of the opening remains the same, but seems to diminish in consequence of the very considerable growth of the ovule ; and the side of the boat, distended by the young seed, soon forms for it a complete envelope. It is here that all the transformations of the ovule take place; from being orthotroparit becomes amphitropal, and changes, in this conversion, the direction of its micropyle, which, instead of being opposite the base of the funicle, is turned to the opposite side. Lastly, the ac- cessory envelope of which we have been speaking, becoming thick and hard like a stone, and being covered on its outside with plenty of pulp, plays the part of a crustaceous testa with respect to the seed, and protects its thin proper integuments. But it is clear from what has now been stated, that this stone is nothing but a false testa; the cylindrical portion of the STRUCTURE.] FALSE ARIL OF OPUNTIA. 47 funicle supporting it ought to leave upon it only a false um- bilical scar j and lastly, the small hole of this envelope which represents the originally large opening of the boat can only be looked upon as a false micropyle. It is on the seed itself, i. e. below the false testa, that the true hilum and micropyle must be looked for. Now that we have seen on the seeds of Opuntia an acces- sory envelope, it remains to show the difference between it and a true aril, in order to justify the name of false aril that I have given it. I shall not say that this envelope exists a long time before the expansion of the flower, whilst the aril only appears after impregnation ; the Cytinus has shown us that this character of the aril is not altogether unexception- able, as it was thought to be ; but if it is true that the aril is an appendage of the umbilical cord, and an exterior leaf of the ovulary bud, such an organ cannot be the type of the false testa of Opuntia. The latter, notwithstanding its intimate connexion with the funicle, is no more an appendage of it, or a modified leaf, than the flattened branches of Ruscus or of Xylophylla are true leaves. It is not formed of a circular or unilateral expansion, like that of the Passion flowers, or of Turnera, but of two thin edges, which, produced from the two sides of the funicle, remind us of productions of a similar nature found on those axes called winged or bordered. Now that we know the origin of the crustaceous envelope which conceals the seed of Opuntia, it will be easy to understand that the portion of the umbilical cord originally curved into a ring is represented by the raised rim found at the contour of this envelope. The micropyle is generally looked upon as a canal for im- pregnation, and the supposed existence of a tissue to conduct the fecundating matter is supported by curious and positive facts. When certain ovules, at the time of flowering, are seen invariably to bring their orifice to the same point of the ovary or of the placenta, this point may be properly con- sidered as intended in a special manner to transmit the fecundating agent, and these conclusions have been confirmed by anatomy, which shows the existence of a peculiar tissue 48 OTHER FALSE ARILS. [BOOK i. extending from this point to the stigma. Other ovules, however, instead of bringing their exostome near the peri- carp or the placenta, apply it to their funicle, which in this case either contains the conducting tissue or takes its place. If there is any doubt as to the latter statement, it is only necessary to recur to the ovules of Opuntia, which are, long before impregnation, completely covered by a thick accessory envelope, and the true micropyle of which, in no way cor- responding with the orifice of the false testa called by us false micropyle, can have no direct communication with the exterior. It is clear that in this case the fecundating agent, whatever it may be, pollen-tube or fovilla, cannot pass directly from the pericarp to the ovule, since the latter is completely covered by the accessory envelope before mentioned. And since the ovule is in communication with the ovary only by the funicle, the latter alone can transmit fecundating matter to it. Many genera of Indian Figs are so intimately allied to one another, that great analogy might be expected to be found between the integuments of their seeds. But such is not the case ; the remarkable organisation of the seeds of Opuntia is not found in Epiphyllum, Khipsalis, or Mammillaria, even when their fruit is ripe. Cereus peruvianus, the ovary of which I have only been able to observe sometime after flower- ing, has no trace of any accessory envelope on its ovules, although the funicles were at this time curved in the same way with respect to the ovules, as those of Opuntia before expanding into a membrane. If the anomalous production just described has only been as yet found in a single genus of plants, such is not the case with the expansions of the exostome, the type of which is furnished by Euonymus. These, which are very common, and the nature of which has often been mistaken, deserve more especially the name of false arils, and coincide with certain modifications of the testa, which it will, perhaps, be useful to notice. The testa, it is well known, often contains in its thickness very different layers of tissue. Sometimes its exterior is crustaceous, and the vascular network it contains is hidden, like the raphe, under one or more hard opaque plates. This STRUCTURE.] IN SPURGEWORTS, ETC. 49 is to be found in Leguminosae, Soapworts, Anonads, Dil- leniads, and many other plants. In this case, I have fre- quently seen a true aril, but never an arillary expansion of the edges of the exostome. At other times, over one or two exterior plates of the testa, which are cartilaginous, or crust- aceous, we find a layer, more or less thick, of parenchyma, in which the raphe and its ramifications are visible. This exterior layer, often described by Gsertner, under the name of epidermis, and considered in Euphorbiacea? as an aril, by M. Roeper, is characteristic of the seeds of entire natural orders, as of Euphorbiacea3, Malvaceas, Butneriacese, Myris- ticacese, Tiliacese, Polygalacese, Hypericacese, Violacese, Lina- cea3, Thymelacese, &c., &c.; and it is on these seeds that the expansions of the micropyle, which have often been con- founded with those of the funicle, have been found. Between these two states of the testa, which are sometimes perfectly well marked, a number of intermediate stages are found, which make them run one into the other ; Rhamnus, among many other examples, according to the correct observation of M. Ad. Brongniart, unites them both. Indeed, when I say that the expansion of the exostome is peculiar to those seeds which have a visible raphe on their outside, I do not mean that a true aril cannot exist on their testa, since Bixa, the seeds of which are covered with pulp, has, nevertheless, a rudimentary aril. The seeds of Euphorbia, of Ricinus, and of many other Spurgeworts, have at the side of their point of attachment a fleshy, lenticular, or hemispherical excrescence, which, at an early period, attracted the attention of observers. Without saying anything as to its nature, Adanson described it as a fleshy tubercle ; and Gaertner, after him, as a thick spongy hilum. This error of the German carpologist was soon fol- lowed by one of a more serious nature. Some botanists, no doubt undecided as to the value of the word aril, applied it to the caruncle of Euphorbia. M. Mirbel, however, in his excellent memoir on the ovules of Euphorbia Lathyris, cleared up all doubts as to the nature of this excrescence, and clearly showed it to be nothing but the thickened edge of the exos- tome. If we compare this fact with that we have already VOL. II. E 50 CARUNCLES. [BO°K i- seen in Euonymus, it will be easily seen that the caruncle of Euphorbia is, as it were, nothing but a rudiment of the more highly developed arillode of the Spindletree ; and this analogy will be still more evident, when we shall have seen states of the false aril intermediate between these two. If the results to which I have been led, by applying the single fact of M. Mirbel to a certain number of plants, are at all interest- ing to botanists, I shall state that in so doing I have only followed the example of M. Aug. de St. Hilaire, who, in his Morphologic (p. 751), very positively noticed the relations between the caruncle of Euphorbias and those which render the seeds of Polygala so remarkable. What at first seems very curious in the seeds of the latter genus, is the various forms and sizes of the caruncles in different species. Always next the hilum, but independent of the funicle, they are sometimes nothing but simple conical tubercles, tridentate or trifid at their base ; one or two linear fleshy extensions sometimes proceed from this same base, and extend to a greater or less degree towards the chalaza, being applied to the surface or back of the seed. But, not- withstanding these variations in form, the caruncle is always found at that point of the seed to which the radicle corre- sponds, and the nearly constant direction of the latter towards the micropyle is sufficient to make us suppose beforehand that the opening of the integument is found on the excrescence itself, or rather that the latter is nothing but the dilated exostome. This also was observed by Aug. de St. Hilaire, and if the opinion of so profound a philosopher were not a sufficient guarantee for the exactness of the fact, I should state that I have clearly seen the micropyle at the anterior part of the caruncle of Polygala myrtifolia and speciosa. It is then, I think, quite clear that the caruncle of Polygala is completely analogous to that of Euphorbia, and this new point of resemblance between the seeds otherwise so similar of these two genera, explains better why Adanson brought them both together in his family of Tithymales. In other Milkworts the caruncle is singularly modified ; that of Comesperma is covered with long hairs which conceal the whole seed ; the thick oily one of Badiera occupies the STRUCTURE.] CARUNCLES. 51 whole lower half of the surface of the testa. These excres- cences I have many reasons to think are analogous to those of Polygala, but not having myself seen the seeds of these two genera,, J cannot be certain on this point. Between the excrescences we have just examined and those found on the seeds of the Lasiopetalese and of several Bytneriads, the connection is very striking. There is the same position next the hilum, the same variations in form, the size and toothings, and the same fleshy consistence. In addition to these external resemblances, we may add, that in the latter plants, as in Polygala, the radicle is constantly next the point of insertion of the caruncle, and that this is inde- pendent of the umbilical cord. And lastly, to make the identity perfect, I may state that I have seen in two species of Commersonia, the micropyle scarcely visible and placed on the caruncle itself. I have not been able to repeat the same observations on the seeds of Seringia, Thomasia, Lasiopetalum, and of others having caruncles ; but if we may judge from the figures of the latter given by M. Gay, there exist such analogies in form and especially of position between these excrescences and those of Commersonia, that I should hardly hesitate in regarding them as expansions of the exostome. Let us remark before proceeding further, that the produc- tions of the micropyle have hitherto appeared frequent in families not distantly related to one another. Now that, for example, many botanists have placed Spurgeworts among the Polypetalous orders, we cannot but see the near affinities which unite this order to Lasiopetalese, Butneriaceae, and in short to the whole of those groups which compose Jussieu's order of Malvaceae. In all these families, as in Euphorbiaceae, the presence of a caruncle is combined in a constant manner with that of a layer of parenchyma which covers one or more crustaceous plates of the testa. But because this coincidence is always found, we must not therefore conclude that the layer of parenchyma cannot exist without a caruncle. In the preceding examples the false aril has been as it were rudimentary ; we shall now proceed to some of those cases in which it is found extending much more over the seed. E 2 52 FALSE ARIL OF GUTTIFERS. [BOOK i. The anatropal ovules of Clusia flava are, in an expanded flower, remarkable for the existence of two membranous hoods, placed one over the other, which seem to proceed from the edges of the exostome, and extending round this opening, to cover, without any adherence, nearly a quarter of the young seed. These hoods have sinuated margins and are of unequal length, the upper one only covering about one half of the lower one, which is applied immediately to the proper envelope of the ovule. Have these unequal productions the same origin ? Can the lower one be an extension of the primine beyond its exostome, and the upper and shorter one the rim of the endostome expanded into a membrane? We should answer in the affirmative to the latter question if we stopped at external appearances ; but a mere section of the ovule made through the micropyle and the raphe is sufficient to show that both of these expansions proceed from the primine only, and that the endostome, which is very narrow, is not even thickened at its edges. We are thus obliged to admit, notwithstanding the singularity of the fact, that the external envelope of the ovule, though simple in the greatest part of its extent, is unlined beyond the exostome into two unequal expansions ; and if I may be permitted to compare a leaf of the ovule with the less modified appendages composing the corolla, I should find examples of a similar process of unlining in the petals of Lychnis, Silene, and other Cloveworts, which have at the top of their unguis elegantly fringed lamellae. Whether the curious organisation just described is peculiar to Clusia, and to the single species which I have observed, or not, I leave to be decided by those who can examine other species of this genus, or of the natural order to which it belongs. But I do not doubt that the arillary cupule observed in Quapoya, Havetia, Kenggeria, &c., is a false aril caused by the expansion of the exostome. It will no doubt be remembered that the latter attains its largest size on the seeds of the large-leaved Spindletree. The details which I gave concerning this plant at the begin- ning of the present memoir, will enable me to dispense with a long description of a similar structure, found in other species of the same genus or of the same natural order. V STRUCTURE.] OF THE NUTMEG. 53 Euonymus Europseus, Celastrus scan dens and buxifolius have furnished me, for the organ in question, the same characters as the Euonymus; and I cannot help thinking that they would be also found in Maytenus, Polycardia, Pterocelastrus, and other genera of Spindletrees, in which an aril has been described. The fleshy, laciniate envelope of the nutmeg, so often cited as an example of an aril, is inserted by a pretty large surface to that extremity of the seed to which the radicle points, and even adheres to the base of the raphe. The funicle, which is very short, is attached to the same place, so that the hilum is confounded with the areola of insertion of the accessory envelope, and the latter seems to be an expansion of the umbilical cord i.e. an aril. But we know from the Euonymus that the false aril can be intimately adherent to the funicle, and even to the base of the raphe, without the more for that losing its principal character, and that the micropyle, clearly visible on the arillary integument, distinguishes the latter from the productions of the funicle. I have not been able to examine a nut in a sufficiently good state to enable me to see the micropyle on the surface of its so called aril ; but a very good reason induces me to consider the latter as an expansion of the exostome. In seeds, the testa of which is composed of two layers, the external being parenchymatous, and the internal crustaceous, the position of the micropyle can be distinguished on each ; on the external layer by a narrow opening or a shallow depression, and on the internal one on the contrary by a small tumour, more or less pointed, and very finely perforated, directly corresponding with the external opening, so that the place of the latter can be judged of from that of the tumour, and vice versa. Now, in the Nutmeg, the testa of which is composed of two very distinct layers, in the areola of insertion of the pretended aril, we find the little tumour which on the crustaceous layer of the testa represents the micropyle, and towards which, as I have said, the radicle is pointed ; this laciniate envelope then, though called an aril, is nothing but an expansion of the exostome. The mass inclosed within the testa or outer integument is 54 THE ALBUMEN. [BOOK i. still called the nucleus ; and consists either of albumen and embryo, or of the latter only. The albumen (perispermium, Juss. ; endospermium, Rich. ; medulla seminis, Jungius; secundina internee, Malpighi) (Plate VI. fig. 5. a, 1. 0, 9. a, &c.), when present, is a body inclosing the embryo, and interposed between it and the integuments of the seed when there are any : it is of dif- ferent degrees of hardness, varying from fleshy to bony, or even stony, as in some palms. It is in all cases destitute of vascularity, and has been usually considered as the amnios in an indurated state: but Brown is of opinion that it is formed by a deposition or secretion of granular matter in the cellules of the amnios, or in those of the nucleus itself. The albumen is often absent, is frequently much smaller than the embryo, but is also occasionally of much greater size. This is particularly the case in monocotyledons, in some of which the embryo scarcely weighs a few grains, while the albumen weighs many ounces, as in the cocoa-nut. It is almost always solid, but in Anonads and Nutmegs it is perforated in every direction by dry cellular tissue, which appears to orginate in the remains of the nucleus in which the albumen has been deposited : in this state it is said to be ruminated. The best account of albumen yet published, is that of Schleiden andVogel, of which the following is the substance: — 1. On the Formation of Albumen. — The essential parts of the ovule are the nucleus and embryo sac, which are never absent. In the embryo sac, a portion of cellular tissue is often developed and again absorbed; this is MirbePs quartine. In seeking for albumen, the positions in which it might be expected to be found are, 1, in the integuments, 2, the nucleus, 3, the embryo-sac, 4, the region of the chalaza. It is, how- ever, never found in the integuments, but in all other parts. In Monocotyledons, albumen is mostly found in the embryo- sac, reducing the walls of the nucleus, by pressure, to a thin membrane. It is difficult to say whether the membrana interna of the ripe seed is formed from the integumentum iiiternum of the ovule, from the membrana nuclei, or from STRUCTURE.] FORMATION OF ALBUMEN. 55 a combination of both. It may be sometimes formed from each. In the process of growth the embryo-sac becomes filled with cellular tissue, which produces the albumen. Examples may be seen in Philydrum lanuginosum, also in all Arads, Grasses, Sedges, Lilyworts, Palms, &c. Amomals are an exception, for excepting Canna, they develop their albumen in the nucleus, as in Maranta gibba. The development of Canna is altogether peculiar. The albumen is developed in the region of the chalaza, and although five layers can be dis- tinguished they can none of them be identified. In Dicoty- ledons the growth of the albumen is not so uniform, in these whole groups of families being characterised by its presence or absence. The albumen formed in the embryo-sac is called Endosperm, while that formed in the nucleus is called Peri- sperm. When the embryo-sac does not fill the nucleus, and the embryo does not fill the former, both perisperm and endo- sperm are developed, as seen in Waterlilies (Nymphaeaceae) and Watershields (Hydropeltideae) ; also in Peppers. In Che- lidonium majus, the endosperm is alone developed ; and this is the case with all Papaveraceae, Ranunculaceae, Umbelli- fers and Cinchonads. The perisperm is probably developed in all families which have what is called albumen centrale. 2. On the Structural Relations and Extent of the Albumen. — In most cases the albumen has the form of the seed on a re- duced scale. A remarkable deviation is seen in Convolvulus. The endosperm consists of a double spindle-shaped body, with two wing-like appendages, between which the cotyledons are placed. In many of the Figworts (Scrophulariacea3) the embryo-sac forms little cavities or bags, which, in the ripe seed, remain as appendages to the albumen. Albumen, as well as all other parts of plants, consists essentially of cellular tissue, the cells of which have contents. Cytoblasts are found only occasionally in the cells of albumen, but may be seen very well in Zea Mays. The cells present all the varieties of ordinary parenchym, but never any spiral structure. The walls of the cells are generally thin, simple, without evident configuration, as in the case of the albumen farinaceum and ramosum. The walls are often thick and grown together, so that the cells look as if they were cut out of a homogeneous 56 EXTENT OF ALBUMEN. [BOOK i. mass, as in the albumen oleosum and corneum. In Cinclionads there are thin spots in the horny albumen, as though pores were forming; the same is seen in the horny albumen of some Palms. In the thin- walled cells pores are very evident. With regard to the general arrangement of the cellular tissue, it has a ray-like texture, from its being developed from the walls of the sac towards the embryo, or if that is very small towards the centre of the albumen. With regard to the contents of the cells of albumen, they do not differ much from those of parenchym in general. In Alpinia Cardamomum, formless masses are observed in the cells of the perisperm. Between the cells of Pothos rubricaulis are found larger cells containing some crystallised salt. 3. On the Albumen of Leguminous Plants. — If any one should examine the seeds of Cassia, Gleditschia, and Tetra- gonolobus, he would find it difficult to account for the fact that in recent times albumen had been denied to Leguminous plants. Gsertner originally made exceptions to the statement that they had no albumen ; it was confined, by Jussieu, to the orthoblastic genera. De Candolle called the albumen of these plants an Endoplevra tumida, and most botanists have followed him. Guillemin and Perrottet, in the Flora of Senegal, sometimes call this substance albumen, sometimes Endopleura tumida. In order to investigate this subject, and arrive at the following conclusion, more than 300 different kinds of seeds of Leguminous plants have been examined. a. Formation and Presence. — The ovule of Tetragonolobus purpureus has two integuments covering the nucleus. The embryo-sac developes itself in the vicinity of the micropyle and grows from thence out towards the chalaza. In Brachysema undulatum, the integuments and nucleus are not developed till after the embryo-sac and embryo appear, and the internal membrane disappears with the absorption of the nucleus. In Tetragonolobus the nucleus is first absorbed, then the internal membrane, the entire length of which disappears at the same time. The embryo, in its development, constitutes a transition to that irregular form seen in Lupinus. Ordinarily that part of the pollen tube which has projected into STRUCTURE.] ALBUMEN OF LEGUMINOUS PLANTS. 57 the embryo-sac becomes changed into a part of the embryo ; but in Lupinus only a part of the tube becomes organised with the embryo, the remaining portion forming a little cord-like body, called by Mirbel the suspensor. As the embryo-sac extends, it forms cells out of the mucous and saccharine solution in its inside, the cells being developed around the cytoblasts in the manner described by Schleiden. At the same time this cellular tissue is forming the embryo increases in size, and either absorbs this or presses it more or less together ; in the latter case it is the seat of the deposit of albumen. This is often the case, and in most instances the nucleus is entirely absorbed. Hence the albumen of Leguminous plants is endosperm; its greater or smaller thickness depends on the greater or smaller size of the embryo. In the whole family there is a very decided fluctuation in the presence and quantity of this albumen ; so that the suggestion of Braun to distinguish the genera of Mimosea3 by it, is quite untenable. In fact there are some very good genera, as Lupinus, in which some species have it, and some have none. Lupiuus tomentosus and L. macrophyllus both have albumen, L. tuberosus none. In Ononis altissima, it is scarcely to be seen, whilst in O. aculeata it is very abundant. JEschynomene fluminensis has a maximum, whilst JE. podocarpa has a minimum. Many more examples would undoubtedly occur in large genera, as Trifolium, &c. In Acacia some species have abundance, others none. But if the existence of albumen fluctuates, much more do its relative quantity and its relative position to the embryo. Its development is least decisive in the whole family on the edges of the cotyledons ; in Papilionacese least at the hilum and in greatest quantity between the radicle and cotyledons, and in the commissure between the cotyledons ; in both of which places it may be beautifully seen in Scorpiurus sulcatus, yet it is sometimes wanting here when it appears on the sides of the cotyledons. The quantity of albumen has been supposed to be in an inverse propor- tion to the size of the plumule, but this is not a rule, 58 ALBUMEN OF LEGUMINOUS PLANTS. [BOOK i. even in the genera, to which it was supposed to apply. Nor is a large quantity of albumen accompanied with simple leaves of the plumule, as was supposed by Braun. In opposition to the oft-repeated assertion of Adanson, Jussieu, and De Candolle, it is found that all the principal divisions of Leguminous plants, except Swartziese and Geoffrese, of which only one seed was examined, possess albumen. b. Structure. — If a layer of albumen is cut, it is transparent, almost of a horny consistence, becomes gelatinous in water, is almost insipid to the taste, and consists of vegetable jelly (P. pflanzengallerte of Schleiden) or mucus (P. pflanzenschleim of Berzelius). In most cases the colour is whitish, in some beautifully white, as Cytisus, Kennedya, &c. When it is transparent, so long as the testa remains on, it has a variety of colours. In Bauhinia microphylla, the albumen was of a wood- yellow colour. Where the albumen is tolerably well developed, three layers are observed; first, that next the testa with regular cells, well defined walls, and ordinarily granular mucous contents : the cells are arranged in only one row. This layer is well seen in Astragalus hamosus, Sesbania cannabina, &c. In the second layer there is a number of variously formed cells, constituting the great bulk of the albumen ; these are succeeded by a third row placed next the cotyledons, which are small and without granular contents. In the middle layer the cells have either very sharply defined walls, or they are lost in jelly. The former are most common in Papilionaceae, the latter in Csesalpineae. When the walls of the cell are evident, jelly is found in the inside of the cell, often obstructing the entrance of the light, as in Sesbania cannabina, &c., it is entirely obstructed in Securigera coronilla. Frequently the cavity of the cell presents a star shape, from the form- ation of pores in the jelly, or gelatine, as in Cytisus, Laburnum, &c. Intercellular spaces are seen in Amor- pha fruticosa, See., which are also filled with jelly. These form a transition to those in which the cells are entirely .STRUCTURE.] THE EMBRYO. 59 embedded in jelly, as Gleditschia triacanthos. The walls are not to be distinguished but by dropping on them sulphuric acid, by which means the jelly is dis- solved out. The interior of the cells is filled with mucus (Schleim), a term used to distinguish it from jelly and starch. This mucus is composed of globules, which are coloured brown yellow by tincture of iodine. In Ca- thartocarpus fistula resinous globules were found, and in Mimosa pudica, crystals in the same position. This jelly or gelatine between the cells, seems to be identical with Mohl's intercellular substance, and it may be con- jectured to be the basis from which the cells of the albumen themselves are formed. The embryo (or corculum) (Plate VI. fig. 1. b, &c.) is a fleshy body occupying the interior of the seed, and consti- tuting the rudiment of a future plant. In most plants one embryo only is found in each seed. It nevertheless occurs, not unfrequently, that more than one is developed within a single testa, as occasionally in the Orange and Hazel nut, and commonly in Conifers, Cycas, the Onion, and the Mistletoe. Now and then a union takes place of these embryos. It is distinguished into three parts ; viz., the radicle (Plate VI. fig. 2. b, &c.) (rhizoma or rostellum] ; cotyledons* (fig. 2. 0, &c.) ; and plumule (or gemmule] (fig. 2. c.) ; from which is also by some distinguished the cauliculus or neck (scapus, scapellus, or tigelle] . Mirbel admits but two principal parts ; viz., the cotyledons, and what he calls the blastema, which comprises radicle, plumule, and cauliculus. The direction of the embryo is either absolute or relative. Its absolute direction is that which it has independently of the parts that surround it. In this respect it varies much in different genera; it is either straight (Plate VI. fig. 5.), arcuate (fig. 9.), falcate, uncinate, coiled up (fig. 8.) (cyclical), folded up, spiral (fig. 19.), bent at right angles (Plate V. fig. 28.) (gnomonical, Link), serpentine, or in figure like the letter S (sigmoid). * Cotyledon (KoruATjSwp), not cotyledon as it is often called. 60 EMBRYO — COTYLEDONS. [BOOK i. Its relative position is determined by the relation it bears to the chalaza and micropyle of the seed ; or, in other words, upon the relation that the integuments, the raphe, chalaza, hilum, micropyle, and radicle bear to each other. If the sacs of the ovule are in no degree inverted, but have their common point of origin at the hilum, there being (necessarily) neither raphe nor chalaza visible, the radicle will in that case be at the extremity of the seed most remote from the hilum, and the embryo inverted with respect to the seed, as in Cistus, Urtica, and others, where it is said to be antitropal. But if the ovule undergoes the remarkable extension of one side already described in speaking of that organ, when the sacs are so inverted that their orifice is next the hilum, and their base at the apex of the ovule, then there will be a raphe and chalaza distinctly present ; and the radicle will, in the seed, be at the end next the hilum, and the embryo will be erect with respect to the seed, or orthotropal, as in the Apple, Plum, &c. On the other hand, supposing that the sacs of the embryo suffer only a partial degree of inversion, so that their foramen is neither at the one extremity nor the other, there will be a chalaza and a short raphe ; and the radicle will point neither to the apex nor to the base of the seed, but the embryo will lie, as it were, across it, or be Tieterotropal) as is the case in the Primrose. When an embryo is so curved as to have both apex and radicle presented to the hilum, as in Reseda, it is amphitropal. It is, however, becoming customary to apply to the seed the same names as those used in express- ing the modifications of the ovule ; this will probably become the universal practice, and then all terms referring to the position of the embryo will become superfluous. In the words of Gartner an embryo is ascending when its apex is pointed to the apex of the fruit ; descending, if to the base of the fruit ; centripetal, if turned towards the axis of the fruit ; and centrifugal, if towards the sides of the fruit : those embryos are called wandering, or vagi, which have no evident direction. The cotyledons are generally straight, and placed face to face ; but there are numberless exceptions to this. Some are separated by the intervention of albumen (Plate VI. fig. 11.) ; STRUCTURE.] DICOTYLEDONOUS EMBRYO. (51 others are naturally distant from each other without any intervening substance. Some are straight, some waved, others arcuate or spiral. When they are folded with their hack upon the radicle, they are called incumbent ; if their edges are presented to the same part, they are accumbent ; terms chiefly used in speaking of Crucifers. Upon certain differences in the structure of the embryo, modern botanists have divided the whole vegetable kingdom into three great portions, which form the basis of what is called the natural system. These are, 1. Dicotyledons; 2. Monocotyledons ; and, 3. Acotyledons. In order to un- derstand exactly the true nature of the embryo in each of these, it will be requisite first to describe it fully as it exists in dicotyledons, and then to explain its organisation in the two others. If a common DICOTYLEDONOUS embryo (Plate VI. fig. 2.), that of the Apple for example, be examined, it will be found to be an obovate, white, fleshy body, tapering and solid at the lower end, and compressed and deeply divided into two equal opposite portions at the upper end ; the lower tapering end is the radicle, and the upper divided end consists of two cotyledons. Within the base of the cotyledons is just visible a minute point, which is the plumule. The imaginary line of division between the radicle and the cotyledons is the cauli- cule. If the embryo be placed in circumstances favourable for germination, the following phenomena occur : the caulicule will extend so as to separate the cotyledons from the radicle by an interval, the extent of which varies in different plants ; the radicle will become elongated downwards, forming a little root ; the cotyledons will either elevate themselves above the earth and unfold, or, remaining under ground, will part with their amylaceous matter and shrivel up ; and the plumule will lengthen upwards, giving birth to a stem and leaves. Such is the normal or proper appearance of a dicotyledonous embryo. The exceptions to it chiefly consist, 1 . in the cohesion of the cotyledons in a single mass, instead of their unfolding; 2. in an increase of their number; 3. in their occasional absence ; and, 4. in their inequality. 62 COTYLEDONS OF CAREYA, ETC. [BOOK i. A cohesion of the cotyledons takes place in those embryos which Gsertner called pseudomonocotyledonous, and Richard macrocephalous. In the Horsechesnut, the embryo consists of a homogeneous undivided mass, with a curved horn-like prolongation, of one side directed towards the hilum. If a section be made in the direction of the axis of the horn-like prolongation, through the whole mass of the embryo, a slit will be observable above the middle of the horn, at the base of which lies a little conical body. In this embryo the slit indicates the division between the two bases of a pair of opposite confluent cotyledons ; the conical body is the plu- mule, and the horn-like prolongation is the radicle. In Castanea nearly the same structure exists, except that the radicle, instead of being curved and exserted, is straight, and inclosed within the projecting base of the two cotyledons ; and in Tropseolum, which is very similar to Castanea in structure, the bases of the cotyledons, are slit into four little teeth inclosing the radicle. The germination of these seeds indicates more clearly that the cotyledonary body consists of two and not of one cotyledon ; at that time the bases of the cotyledons, which had been previously scarcely visible, sepa- rate and lengthen, so as to extricate the radicle and plumule from the testa, within which they had been confined. Mr. Griffith states that in Careya herbacea, " The fleshy body which constitutes the entire mass of the seed, after the removal of the testa, consists of a peripheral fleshy mass and a central subulate body firmly adherent with it, of similar texture, and having its apex directed towards one side of the hilum. At the opposite extremity the outer mass is sur- mounted by a number of colourless scales, surrounding and concealing other more minute scales, which occupy the extremity of the central subulate body. There are no traces of cotyledonary division, and the subulate body, excepting at its divided upper extremity, is continuous with the rest of the fleshy mass. The commencement of the germination takes place while the seeds are still inclosed in the fruit. The integument is ruptured longitudinally, and generally with some degree of regularity along the apex ; from this opening are exserted pale greenish scaly leaf-like bodies, consisting STRUCTURE.] THEIR NUMBER AND ABSENCE. 63 first of those which surmount the outer mass,, and subse- quently of the divided termination of the central subulate body. As this latter increases in length, it is seen to termi- nate in a green convolute leaf, in the axilla of which is placed another very rudimentary one. At this period the extremity of the subulate body next the hilum has also become exserted, and forms a subulate fleshy and undivided projection. Into this the cellular tissue of the fleshy body passes, although there is a faint line of demarcation between the two. " The absolute nature of the outer fleshy part," Mr. Grif- fith observes, "can only be determined by pursuing the development of the ovula. The nature of the subulate body is evident ; it is the root, the true plumula being the minute scaly body at its distal end. The root points, as it should do, towards the side of the hilum, the situation, in fact, of the foramen. At the collar it is continuous with the plumula, and laterally with the outer fleshy mass ; which ought, there- fore, to be cotyledonary, and taking it to be so, might be explained, by supposing the cotyledons to be affixed in a peltate manner, and united into a solid mass." In number the cotyledons vary from two to a much more considerable number ; four occur in Borageworts, Crucifers, and elsewhere ; in Conifers they vary from two to more than twelve. Instances of the absence of cotyledons occur, 1 . in Cuscuta (Plate VI. fig. 19.), in which they may be supposed to be deficient, in consequence of the absence of leaves in that genus; 2. in Butterworts (Lentibulariacese) ; and, 3., in Cyclamen, in which the radicle enlarges exceedingly. To these a fourth instance has by some been added in Lecythis, of which Richard gives the following account : — The kernel is a fleshy almond-like body, so solid and homogeneous that it is extremely difficult to discover its two extremities until germination takes place : at that period one of the ends forms a little protuberance, which subsequently bursts through the integuments of the seed and extends itself as a root; the other end produces a scaly plumule, which in time forms the stem. The great mass of the kernel is supposed by Richard to be an enlarged radicle. I, however, see no reason for 64 ANOMALOUS COTYLEDONS. [BOOK i. calling the two-lobed part of the embryo (Plate VI. fig. 17. c) a plumule, instead of cotyledons. An inequality of cotyledons is the most unusual circum- stance with dicotyledons, and forms a visible approach to the structure of monocotyledons : it occurs in Trapa and Sorocea, in which they are extremely disproportionate. In Cycas they are also rather unequal; but in a much less degree. A case has been mentioned by Mr. Griffith, in Crypto- coryne spiralis, of the cotyledon being cut off, after being formed. " The separation/' he says, " of the chief part of that portion, which is evidently from its direction the coty- ledon, is most remarkable, and forms another exception to a general law. I allude to the very general absolute necessity of the cotyledons. I am, however, inclined to think, from this and some other instances, that the presence of a highly developed plumula occasionally obviates this necessity. The separation in question appears to depend upon some constric- tion exerted upon the cotyledon by the apex of the nucleus/7 (Linn. Trans., xx. 271.) The embryo of MONOCOTYLEDONS (Plate VI. fig. i, B, &c.) is usually a solid, cylindrical, undivided, homogeneous body, slightly conical at each extremity, with no obvious distinction of radicle, plumule, or cotyledons. In germination the upper end swells and remains within the testa (fig. 10. c b, &c.) ; the lower lengthens, opens at the point, and emits one or more radicles : and a thread-like green body is protruded from the upper part of the portion which is lengthened beyond the testa. Here the portion remaining within the testa is a single cotyledon; the body which lengthens, producing radicles from within its point, is the cauliculus ; and the thread-like protruded green part is the plumule. If this is compared with the germination of dicotyledons, an obvious difference will be at once perceived in the manner in which the radicles are produced : in monocotyledons they are emitted from within the substance of the radicular extremity, and are actually sheathed at the base by the lips of the passage through which they protrude ; while in dicotyledons they STRUCTURE.] MONOCOTYLEDONOUS EMBRYOS. 65 appear at once from the very surface of the radicular extre- mity, and consequently have no sheath at their base. Upon this difference Richard proposed to substitute the term Endorhizffi for monocotyledons, and Exorhiza for dicotyle- dons. Some consider the former less perfect than the latter : endorhizee being involute, or imperfectly developed : exorhizse evolute, or fully developed. Dumortier adds to these names endophyllous and exophyllous ; because the young leaves of monocotyledons are evolved from within a sheath (coleophyl- lum or coleoptilum), while those of dicotyledons are always naked. The sheath at the base of the radicle of monocotyle- dons is called the coleorhiza by Mirbel. Another form of monocotyledonous embryo is that of Arads and their allies, in which the plumule is not so intimately combined with the embryo as to be undistinguishable, but is indicated externally by a little slit above the base (Plate VI. fig. 6. B. e), within which it lies until called into development by germination . Mr. Griffith describes a most singular exception to the usual monocotyledonous structure in Cryptocoryne spiralis : — " The embryo is of a singular shape. Its descending portion, or cotyledon, is clavate, and nearly entirely inclosed within the nucleus ; the inclosed part separating with that bady exceedingly readily, and subsequently, about the same time of dehiscence of the fruit, spontaneously. The tissue of the inclosed part is firm, and more dense than the short unin- closed part. The exserted portion of the embryo consists exclusively of the base of the cotyledon, of a fleshy, firm, plano-convex body. The plane part is depressed towards the centre, to which the base of the cotyledon is attached. From one side of this the radicle projects, which is still conical and acute, and is always directed from the placenta, and generally outwards, but often laterally, and always more or less down- wards. The circumference of the convex part is entirely occupied by the processes, constituting an enormously de- veloped plumula. These are densely imbricated, intermixed with abortive and rudimentary ones, and of immense length, especially the outermost, which are about one inch long. They are all subulate, with the exception of the two or three VOL. II. F 66 EMBRYO OF CRYPTOCORYNE. [BOOK i. innermost ones, which resemble rudimentary leaves, and are divided into a limb, which is convolute, and a petiole, which is likewise convolute, the innermost inclosing in its fold an extremely minute rudimentary leaf. The outermost are the narrowest, the bases, as we proceed inwards, becoming gra- dually dilated. They are all deflexed and tortuous, especially the outer ones. Their extreme apices are invariably brown, and, as it were, sphacelated. The colour is green, increasing in depth as we proceed inwards, the convolute Iamina3 of the innermost being of a rather deep tint. These processes are furnished with vessels, but their chief bulk is cellular, the cells containing a considerable number of green globules. They are, with the exception, perhaps, of the outermost, fur- nished with stomata. These bodies, however, appear to be perfect in the interior processes only. They are most abun- dant towards the apices of these, especially on the portion which corresponds to the lamina of the perfect leaf, and are perhaps altogether wanting towards or near their dilated bases. The cells of the cotyledon, as well as of the processes of the plumula, in an early stage of their development, abound in active molecules, which have, both in and out of the containing cells, an exceedingly rapid oscillatory motion. It is obvious, from the universal presence of these corpuscles during the formation of tissue, that they play an important part in this most obscure process." (Linn. Trans, xx.) All such exceptions ought, like those of dicotyledons, rather to be called remarkable modifications. Much stress has been laid upon some of them by several writers, who have thought it requisite to give particular names to their parts. It, however, appears more advisable to explain their analogies without the unnecessary creation of new and bad names. In Grasses (Plate VI. fig. 4.) the embryo consists of a lenti- cular body lying on the outside of the base of the albumen on one side, and covered on its inner face by that body, and on its outer face by the testa : if viewed on the face next the testa, a slit will be observed of the same nature as that in the side of the embryo of Aracese ; within this cleft a small coni- cal projection is discovered, pointing towards the apex of the seed. If the embryo be then divided vertically through the STRUCTURE.] OTHER ANOMALIES. C>7 -conical projection, it will be seen that the latter (c) is a sheath including other little scales resembling the rudiments of leaves; that that part of the embryo which lies next the albumen (d), and above the conical body, is solid ; and that the lower extremity of the embryo (e) contains within it the indi- cation of an internal radical, as in other monocotyledons. In this embryo it is to be understood that the conical projection is the plumule ; that part of the embryo lying between it and the albumen, a single scutelliform cotyledon ; and the lower point of the embryo, the radicle. In Wheat there is a second small cotyledon on the outside of the embryo, inserted a little lower down than the scutelliform cotyledon. This last is called scutellum by Gartner, who thought it of the nature of vitellus. Richard considered the scutelliform cotyledon a particular modification of the radicle, and called it hypoblastus ; the plu- mule a form of cotyledon, or blastus ; the anterior occasional cotyledon a peculiar appendage, or epiblastus ; and the radicle a protuberance of the caulicule, or radiculoda. He further^ in reference to this opinion, termed embryos of this descrip- tion macropodal. In these ideas, however, Richard was wrong, as is now well known. From what has been stated, it is apparent that dicotyledons are not absolutely characterised by having two cotyledons, nor monocotyledons by having only one. The real distinction between them consists in their endorhizal or exorhizal ger- mination, and in the cotyledons of dicotyledons being opposite or verticillate, while they are in monocotyledons solitary or alternate. Some botanists have, therefore, recommended the substitution of other terms in lieu of those in common use. Cassini suggests isodynamous or isobrious for dicotyledons, because their force of development is equal on both sides ; and anisodynamous or anisobrious for monocotyledons, because their force of development is greater on one side than on the other. Another writer, Lestiboudois, would call dicotyledons exoptiles, because their plumula is naked; and monocotyle- dons endoptiles, because their plumule is inclosed within the cotyledon; but there seems little use in these proposed changes, which are, moreover, as open to objections as the terms in common use. F 2 68 THEORY OF MONOCOTYLEDONS. [BOOK i. In the Library of Useful Knowledge, the following explana- tion of the analogy between the embryo of monocotyledons and dicotyledons has been given : — "1. The embryo of an Arum is like that of a Palm, only there is a slit on one side of it through which the plumule easily escapes ; 2. in Rice (Oryza) this slit is very much lengthened and widened ; 3. in Barley the plumule projects beyond the slit, leaving a flat cotyledon on one side; and, 4., in Wheat the embryo has the structure of Barley, with this most important exception, that at the base of the plumule in front there is a rudimentary cotyledon, alternate with the large flat one on the opposite side of the plumule. Hence we are to infer that the monocotyledonous embryo of a Palm is analogous to that of a dy cotyledon, of which one of the coty- ledons is abstracted, and the other rolled round theplumula and consolidated at its edges. And this is the view that must be taken of the monocotyledonous embryo in general, all the modifications of which seem reducible to this standard. "Thus in Sea- wrack (Zostera marina), of which the embryo is an oblong almond-shaped body with a cleft on one side, in the cavity of which a long flexuose process is placed, the latter is the plumule, and the former at one end the cotyledon, and the radicle at the other; in Ruppia maritima, whose embryo is an oblong body, cut suddenly off at one end, on which a sort of curved horn crouches, the latter is the plumule, and the former chiefly cotyledon ; and so in Frog-bit (Hydro- charis morsus ranse), the embryo of which is an oblong fleshy kernel with a hole on one side, in which there lies a short cylinder, the latter is the plumule, and the former the cotyledon." M. Adrien de Jussieu has examined this theory with much ability. By tracing the development of the monocotyledonous embryo, he found that in reality the plumule is enwrapped by the lower portion only of the cotyledon, and therefore he would modify the theory accordingly. "La Theorie de M. Lindley n' est done vraie que pour la partie inferieure ou gaine du Cotyledon, la seule qui s'enroule autour de la plumule ; et la premiere feuille de la pi ante monocotyledonee ne se comporte pas autrement que chacune des autres, dont STRUCTURE.] ACOTYLEDOXS — NAKED SEEDS. 69 la gaine enveloppera de meme Teusemble des feuilles suivantes avant leur developpement." (Annales des Sciences, 2nd ser. xi. 350.) It is gratifying to find a morphological speculation confirmed upon such authority. I say confirmed, because, in fact, M. de Jussieu admits all that is essential in the theory as originally propounded. I certainly did not mean that the whole cotyledon of a monocotyledonous embryo was neces- sarily rolled from end to end around the plumule, but that the whole or a part was in that condition. The ACOTYLEDONOUS embryo is not exactly, as its name seems to indicate, an embryo without cotyledons ; for, in that case, Cuscuta would be acotyledonous. On the contrary, it is an embryo which does not germinate from two fixed invariable points, namely the plumule and the radicle, but indifferently from any point of the surface; as in some Arads, and in all flowerless plants. See Mohl, Bemerkungen itbcr die Entwicklung und den Ban der Sppren der Crypto- gamischen Gewdchse : Regensb. 1833. 16. Of Naked Seeds. By naked seeds has been understood, by the school of Linna3us, small seed-like fruit, like that of Labiates, Borage- worts, Grasses, and Sedges. But as these are distinctly covered by pericarps, as has been already shown, the expres- sion in the sense of Linnaeus is incorrect, and is now aban- doned. Hence it has been inferred that there is no such thing in existence as a naked seed ; that is to say, a seed which bears on its own integuments the organ of impregnation. To this proposition botanists had assented till the year 1825, when Brown demonstrated the existence of seeds strictly naked : that is to say, from their youngest state desti- tute of pericarp, and receiving impregnation through their integuments without the intervention of style or stigma, or any stigmatic apparatus. That learned botanist has demon- strated that seeds of this description are uniform in Conifers and Cycads, in which no pericarpial covering exists. But we 70 GENERAL MORPHOLOGY. [BOOK i. have no knowledge at present of such an economy obtaining in other plants except Taxads and Jointfirs (Gnetacese) as a constant character. It does, however, happen, as the same observer has pointed out, that in particular species the ovaiy is ruptured at an early period by the ovules, which thus, when ripe, become truly naked seeds : remarkable instances of which occur in Ophiopogon spicatus, Leontice thalictroides, and Peliosanthes Teta. The seeds are almost uncovered after the ovary begins to swell, in Reseda; and in the common Vine the grapes are occasionally ruptured, allowing their seeds to protrude and ripen. 17. The Comparative Anatomy, or Morphology of the Floral Organs in Flowering Plants. From what has been said in the preceding pages it will have become obvious that the flower, and all the parts that belong to it, are in reality collections of organs originally the same in nature a» the leaf, arranged upon the same plan, and modified according to the different purposes they are to serve. This being so, the apparently complicated apparatus of a flower is in reality an arrangement of the simplest kind ; and the infinite diversity observable in the blossoms of plants is explicable upon a few general principles, Zuccarini has well observed that we should never lose sight of the great fact, that in Nature there is a paucity in the number of forces, but a prodigious variety in their adaptation to the same object. In no department of the organic world is this more manifest than in the Vegetable Kingdom ; so that the difficulty we now experience is not how these things should be, but how it has happened that they were so long unseen. The earliest philosophers who adopted what are now called Morphological views, reasoned a priori, generalising from an exceedingly small supply of facts. Nevertheless, their views have been proved to be correct, by the unerring testimony of progressive development. This is sufficiently proved by the following very instructive cases : — A. The progressive development of Mallow-ivorts (Malvaceae), MOEPHOLOGY OF MALLOWS. 71 by Duchartre. — The calyx, which at a later period becomes monophyllous with five divisions, appears at first in the form of a continuous rim, surrounding the central mass of the flower, bounded by a large convex tubercle having no distinc- tion of parts. This border soon sends off five small festoons, which correspond to the five sepals thus united at the base from the commencement. This mode of formation is found in the envelopes of all those flowers having a monophyllous calyx or corolla, the development of which the author has had an opportunity of studying. The petals and stamens may be subsequently distinguished and are simultaneously developed, so that it is well to trace their evolutions together. Soon after the appearance of the calyx, the margin of the central tubercle becomes raised into five smaller tubercles, which are rounded, alternating with the segments of the calyx, and thus representing the floral whorl which imme- diately succeeds it. Each of these tubercles soon appears like two in juxtaposition, its development ensuing more rapidly at the two sides than in the median line : and thus, instead of five small primitive eminences, we have five pairs. Nearly at the same time a slight transverse fold appears below and outside of each of these five projections ; this appears to be another appendage of the tubercle, which, at first single, subsequently becomes double. The fold becomes the petal ; the tubercles become stamens. Hence the petals and stamens here belong to one and the same group of organs developed from a base which is common to that spot which in most flowers is occupied by the petal alone. The petal in its further development, which is generally rather slow, much more so than that of the stamens, does not become doubled, and gives no other indication of this tendency except in its more or less bilobate summit. Not so, however, with the stamens ; for shortly after the first ten staminal tubercles have become distinct, we find that a formation perfectly similar to the first is produced. Five new pairs of tubercles opposite to the first, appear in a more internal circle ; then a third arranged concentrically, and consisting of ten other tubercles ; then a fourth, so that the total number is successively doubled, tripled, and quadrupled. 72 MORPHOLOGY OF MALLOW-WORTS. [BOOK i. We thus have ten radiant series, opposed in pairs to the petals, and supported upon a common base, which is frequently cut into five corresponding lobes, more or less marked. At a little later period, each of these tubercles, continuing to grow more at the sides than in the median line, is itself divided into two, and we find that four parallel series become substi- tuted for the two before each petal, and the total number is a second time doubled. The same occurs in those flowers which have very numerous stamens; but there is a slight difference in those in which they exist in less numbers. When either fewer concentric rows are formed, or each of these rows stops at that period at which the pairs are simple and not doubled, or within the first pairs, a single tubercle only is formed; this is slightly lateral and oblique; then another still more internal and on the opposite side, so that within the first pair we find only isolated tubercles, sent off alternately, first from one side, then from the other, in a zig- zag direction. In all cases, there are invariably five systems of stamens opposite to the petals. During these changes, the small common tube, to which all these organs are attached, continues to elongate, raising these concentric formations so as to produce a system of stages arranged one above the other ; and, although they enlarge at the same time, they do not do so in the same proportion. The organs which enlarge do not then find sufficient room to lie side by side in regular and concentric circles ; they become rather confusedly mixed, and the original symmetry becomes less and less apparent. When they have arrived at a certain degree of development, each of the tubercles shrinks up at the base into a minute filament which becomes more and more elongated. Each also becomes marked by a median furrow, and buried within two cells which subsequently fuse into a single one. In short, these are so many reniform, unilocular anthers, which tend more and more to assume their definite form. In several species M. Duchartre has observed an ulterior change, from which a new increase in the number of stamens results. Several of them are curved into a horse-shoe form, and terminate by becoming divided into two by a constric- STRUCTURE.] MORPHOLOGY OF MALLOW-WORTS. 73 tion of the summit of their curve — a constriction which ends by forming a complete solution of continuity ; this, extend- ing from above downwards, also divides the filament which was at first simple, into two corresponding to the anthers thus formed. This is a true duplication. This term would apply with less accuracy to the anterior formations, from which the multiplication of the stamens has resulted ; for we may say, that at each of these changes they have doubled rather than multiplied. Be this as it may, we have clearly five groups of organs alternating with the five leaflets of the calyx, each comprising a petal and several stamens, supported upon a base which is common and simul- taneously developed. This is the whorl which is within and alternate to the calyx, and which is ordinarily called the corolla, with this difference, that here each petal is replaced by a group or bundles of organs. One of the reporters on M. Duchartre's observations is of opinion, that in those flowers which have stamens double in number to the petals, whenever the stamens of the external row are opposed to the petals (and this is most frequently the case) they do not constitute a distinct whorl, but form a part of that of the corolla. The development of the flower of the Mallow-worts supports this opinion, exhibiting each of the petals, opposed, not to a stamen, but to an entire bundle. It is added, that such appears to be the most common symmetry in polyadelphous polypetalous flowers, as is seen in so many Myrtacese, Hypericacese, &c., where the bundles, which are perfectly distinct, are opposite to the petals. What has become of the normal whorl of the stamens, — that which should alternate with the petals ? M. Duchartre discovers this in the five terminal lobes of the staminal tube, situated upon a plane anterior to that of the filaments, alter- nating with their five groups, — lobes which we observe in many of the Malvaceae, although they are barely perceptible, and even are entirely wanting in many others. MM. Dunal and Moquin-Tandon recognised them, and considered them as the border of a five-lobed disc. But the nature of the disc is far from rigorously defined, and in many cases this term exactly applies to abortive whorls, as may be seen in 74 MORPHOLOGY OF MALLOW-WORTS. [BOOK. i. many Viniferse, in the Myrsinese, &c., families which are equally remarkable by the opposition of their stamens to the petals, to which they are equal in number. M. Duchartre mentions this example of the Myrsinese as exhibiting exactly the symmetry of the Malvaceae, with this difference, that a single stamen only corresponds to each petal. We do not agree with him in this opinion, but think that in the Myrsinese there are two whorls of stamens independent of the corolla, the external or that alternating with the petal being metamorphosed or abortive. This appears to be de- monstrated by the flowers of Theophrasta, or better still by Jacquinia. The author, arriving at the pistil of the Malvacere, finds in their different genera variations which are sufficiently considerable to establish four different categories, which he successively examines. In the first the quinary symmetry is at once apparent, and the five carpels differ but little in their mode of development from the views and theories generally adopted. In fact, we know that each carpel is considered as a leaf folded on itself, and that numerous organogenic obser- vations exhibit this organ to us in the form of a minute scale which soon becomes concave internally, then tends more and more to close up by the approximation of the borders of the concavity, the adhesion of which completes the formation of the ovary, and forms a perfectly closed cavity, in which one or more ovules subsequently become developed. Now, imagine five of these scales or plates soldered together by their lateral surfaces, we then have the first condition of the pistil of Hibiscus. That will be a small border having five angles, which alternately project and recede internally ; the projecting angles correspond to the borders of five carpels, approximated in pairs, and these angles projecting more and more, and converging, terminate by uniting, so as to form a quinquelocular ovary. But at a still earlier period, before the internal projections were marked, we had a pentagonal border which soon becomes festooned by five tubercles, the first indications of the styles. In a secondary category, Malope, for instance, we also observe a pentagonal border, the five angles of which are opposite to the petals, and consequently correspond to the STRUCTURE.] MORPHOLOGY OF MALLOW-WORTS. 75 place which five normal carpels should occupy. That border of the pentagon which is first united sends out a series of rounded tubercles, which subsequently become slightly swollen externally and inferiorly, so that each tubercle pre- sents two enlargements ; one external and inferior, the future ovary, — another superior and internal, the future style. The latter becomes elongated and raised in proportion as the former increases in size; but as it elongates, the stylous portions, remaining distinct at their summits, are confounded at their base, — at least all those which correspond to the same angle of the common support of the carpels ; an angle which becomes more and more marked as far as the point at which the entire body is, as it were, cut into five oblique lobes loaded with* ovules on every part of their surface. A bundle of styles, equal in number, distinct superiorly and united inferiorly, thus corresponds to each of these systems of ovaries ; and each of these systems, in the general sym- metry, plays an analogous part to that which we have found assigned to each of the bundles of stamens, because it occupies the place which a single carpel should occupy, and which it consequently represents. How is the cavity of the ovary formed ? M. Duchartre has not in this case found that the margins of a folded leaflet approximate towards one another, then touch and adhere ; but, at a certain period, dissection has exhibited to him the cellular mass of the ovary excavated by a slight fissure, which continues to enlarge, without any manifest external appearance. A third category, and that includes the greater part of the Malvaceae, exhibits the carpels not in constant relation with the quinary number of the other parts of the flower ; but they form a perfect circle, are not grouped into five systems, and frequently their entire number is no multiple of five. However, M. Duchartre is led to believe that the same symmetry occurs here as in the pre- ceding case. The ovaries and styles are developed in the same manner, with this difference, that all the styles are united inferiorly into a single cylinder. Finally, a fourth category seems to belong to the first by the quinary number of the carpels ; but here we observe ten 76 MORPHOLOGY OF PAPILIONACEOUS FLOWERS. [BOOK i. tubercles on the pistillary border,, which subsequently form ten summits of distinct styles, and which correspond in pairs to five ovaries, the centre of which also becomes hollowed by a fissure, which forms its cavity without any change being externally apparent. The necessary conclusion from all these observations is, that the parts, from their earliest appearance, present the relations of adhesion which they subsequently exhibit in the perfect flower. The monophyllous calyx on its first appear- ance was a body simple at the base. The petals coherent by their base with the staminal tube, originated from a base common to them with the stamens, and the latter at their origin were united by this base in the same manner as they appear subsequently. The ovaries were from the first grouped and adherent together, nearly in the same manner as the flower subsequently exhibits them, their styles being distinct at the summit, coherent in the rest of their extent, which has been more slowly developed. As regards the peculiar results to be deduced from these observations relative to the sym- metry of the flower of the Malvaceas, we have noticed them above, and it would be useless to repeat them. (Annals of Natural History, xvi.) B. The progressive development of the Papilionaceous Flower, among Leguminous Plants, by Schleiden and Vogel :— 1. The flowers are at their origin perfectly regular. 2. The subsequently cohering parts originate as free points, are developed free, and cohere subsequently. 3. All the parts of the flower are at their first appearance green leaves. 4. Even in the earliest stage only one carpellary leaf is visible in the Leguminosse, which is open in the direction of the axis. 5. The anthers are formed from leaves, the inner cellular tissue being converted in part into pollen; and the loculi originate at both sides of the margin of the leaf, which is subsequently changed into the bursting rima. 6. The ovules are formed alternately at the upper margin of the ovarium, and consist of the nucleus and generally of two integuments, rarely of an integumentum simplex. STRUCTURE.] MORPHOLOGY OF IRREGULAR FLOWERS. 77 7. The ovules of the Papilionacese are hemitropous. 8. The embryo originates from the pollen tube at the micropyle end of the embryonal sac, and increases either from this place towards the chalaza, or (being propelled by the pollen tube, which has become cellular, to the centre of the embryonal sac), both in the direction of the chalaza and that of the micropyle. 9. The epidermis of the seed is formed in the Leguminosse only of one integument, which, however, always separates into several layers. 10. No endopleura tumida exists in the Leguminosse ; what has been considered as such is albumen, and, in fact, endosperm. The authors have also discovered that the ovules of the genus Lupinus are only provided with a simple integument, while those of the other Leguminosse always possess a double one. (Annals of Natural History, vol. iii.) C. Progressive development of Irregular Flowers, by M. Bar- neoud. — If a flower of Orchis galeata be examined in the very earliest condition, it will be found to consist of a simple cupula of very transparent tissue, on the border of which three round equal teeth soon become visible ; these constitute the exterior verticil, which is formed exactly in the same manner as a true monophyllous calyx. In a short time a second cupula is seen to originate in the interior of the first, and its substance quickly becomes blended with that of the latter, except that its border exhibits three small prominences, perfectly equal and alternating with the teeth of the exterior verticil. Thus the author considers that organogeny clearly demonstrates in the Orchidacese, as in most other monocoty- ledonous families, analogies of the calyx and corolla of dicotyledons. The three nascent segments of the interior verticil of Orchis galeata are quite similar in the early condition, and it is not until a subsequent period that one becomes evidently broader and more fully developed than the two others ; this it is which becomes the labellum. Orchis Morio, Ophrys araneifera, and two exotic genera, a Maxillaria and an Oncidium, presented exactly identical conditions. 78 MORPHOLOGY OF IRREGULAR FLOWERS. [BOOK i. In the Labiates, the corolla of Lamium garganicum when it first becomes visible, is represented by a little cupula scarcely hollowed out at all, bordered by five teeth which are very short, and at this time alone, quite equal, for two of them speedily cohere and become blended together to form a large, round, and very convex lamella, which subsequently becomes the helmet of the Lamium. Of the three remaining teeth, the central one also becomes much larger than the others, which are always small and atrophied. The evolution of the didynamous stamens exposes the singular fact, that the larger two originate rather before the other two, which they exceed in length at every period of their development. Among other Labiates, Ajuga reptans, Scutellaria Columnse and commutata present us with the same phenomena. In Phlomis fruticosa the helmet is formed of two segments of the corolla, as in Lamium. In the Scrophulariacese the segments of the nascent corolla are also equal, but only at their origin. The inequality always manifests itself very soon, and earlier in proportion to the subsequent irregularity of the corolla (Antirrhinum majus, Linaria cymbalaria, Pentstemon Scouleri, Collinsia bicolor, Scrophularia verna). In the genera which possess a fifth, supplemental stamen, this is formed at the same time as the two smaller, and in the spot which remains vacant in the Labiates. The symmetry is then perfect. In the Birthworts (Aristolochia Clematitis and Pistolochia), the simple perigone composing the flower is, at its origin, a kind of tube, very short, at first with an equal and as it were truncated border ; but this state per- sists but a very short time. One side of the mouth of the tube becomes much developed, so as to form the well-known limb of the Aristolochias, while the other undergoes but slight expansion. In the Verbenes (Verbena urticaefolia), and in the Dipsaceae (Scabiosa ucranica and atropurpurea), the irregular corolla follows the same law of development. The petals of Leguminous plants are equal and alike at the origin of the flower ; but a difference of form and size very soon becomes evident (Cytisus nigricans and Laburnum, Ulex europseus, Erythrina cristagalli) . The case is the same in the .STRUCTURE.] MORPHOLOGY OF CONFLUENT FLOWERS. 79 Milkworts (Polygala austriaca and chamaebuxus) . From all these circumstances we may conclude that the irregularity of the corolla, at least in the families cited in this note, is a condition arising after the first appearance of the flower, and is a consequence of an inequality of development among the different parts which compose the floral envelope. (Comptes rendus, June 8, 1846. Translated in the Annals of Natural History, v. 18, by Mr. Henfrey.) D. Morphology of Confluent Flowers, by the Rev. Mr. H hicks. — Two of these monstrosities occur in species of Iris, and much resemble each other. The species are I. versicolor, and I. sambucina. They have five parts in each circle, ex- cept that the inner circle of petals consists of four in one instance, and only thVee in the other. It is sufficiently manifest, that they are produced by the union of two flowers to form each, and they lead to the conclusion that, when Irises with four parts in each circle occur (which is not very uncommon), they are unions of two flowers, one-third part of each having perished in the junction. Various other mon- strosities, consisting in the union of two flowers, are com- pared with the subjects of the description, particularly some of OEnothera, flowers having seven petals, fourteen stamens, and seven stigmas, where the parts preserved in the union are in exactly the same proportion as in the Irises. A third specimen is described as a monstrous union of four flowers, in Scrophularia nodosa. The flower-stalk might be perceived to be formed by the adherence of several stalks. The parts found were fifteen sepals, sixteen petals, twenty stamens, and separate ovaria, each with two carpels, and a third ovarium formed by the adherence of two more, and consisting of eight carpels. Mr. Hincks is of opinion that the union of four flowers would account for these numbers of parts. The increased development of the circle of stamens, five appearing for each flower, though of these several are united in threes together, and two are imperfect, and the increased number of carpels in two of the united flowers, he regards as interesting facts. He thinks that they show that the union of the flowers had the effect of diminishing 80 MORPHOLOGY OF SEXES. [BOOK i. and rendering more equable the pressure on the interior circles, so as to allow of the growth of parts which are usually abortive. (Annals of Natural History, vol. iv.) E. Change of Sex under the influence of external causes. — Mr. Knight long ago showed that a high temperature favoured the development of male flowers, and a low one that of females. In a forcing-house, a fire of sufficient power only to pre- serve in the house a temperature of about 70°, during summer, was employed, but no air was ever given, nor its escape facili- tated, till the thermometer, perfectly shaded, indicated a tem- perature of 95° ; and then only two of the upper lights, one at each end, were let down about four inches. The heat of the house was consequently sometimes raised to 110°, during the middle of warm and bright days, and it generally varied, in such days, from 90° to 105°, declining during the evening to about 80°, and to 70° in the night. Late in the evening of every bright and hot day, the plants were copiously sprinkled with water, nearly of the temperature of the external air ; and the following were the effects produced upon the different species : — A plant of the Water Melon grew with health and luxu- riance, and afforded a most abundant blossom ; but all its flowers were male. On the other hand, Mr. Knight had many years previously succeeded, by long-continued very low temperature, in making Cucumber plants produce female flowers only ; and he entertained little doubt that the same fruit-stalks might be made to support either male or female flowers, in obedience to external causes. In like manner, when Strawberry plants are subjected to a high temperature in forcing-houses, they produce male flowers; and females only in a comparatively low one. It would seem, however, that other external causes, beyond mere heat, influence the production of males or females. In the Ray Reports it is mentioned that M. Hampe observed, in a bush of Salix repens, that twigs above the water blossomed as females, whilst those twigs which had been in the water, and subsequently blossomed, when the water was dried up STRUCTURE.] MORPHOLOGY OF SEXES. 81 had only male blossoms. He endeavoured to prove, by other instances, that Diclinous plants, situated in wet localities, produce more male than female blossoms. (See Linnaa, vol. xiv. p. 367). These facts conclusively establish the important point, that the male and female organs have a common origin, and become one or the other in the course of development, according to the influences to which they are exposed. VOL. ir. 82 FLOWERLESS PLANTS. [BOOK i. CHAPTER III. OF THE COMPOUND ORGANS IN FLOWERLESS PLANTS. General Considerations. IN the foregoing pages an attempt has been made to eluci- date the true nature of the different organs which exist in the most perfectly formed plants ; that is to say, in those whose reproduction is provided for by the complicated appa- ratus of stamens and pistils. We have now to examine the analogies, if any, of those lower tribes, some of which are scarcely distinguishable from animals, where there is no evident trace of sexes, in which nothing constructed like the embryo is to be detected, and which seem to have no other provision made, in many cases, for the perpetuation of their races than a dissolution of their cellular system. Although the general facts belonging to this subject will be found in the Vegetable Kingdom, yet there are some cir- cumstances not alluded to in that work, and others which require an extended explanation, which can be best intro- duced into this place as being of a supplementary and explanatory nature. If the highest forms of flowerless plants are selected for examination, they will be found to correspond very nearly with many groups of Endogens; as, for example, when Clubmosses (Lycopodiacese) are compared with Conifers, and Ferns with Palms. And so, in like manner, if the lowest forms of flowering plants are compared with flowerless species — Lemnads with Crystalworts (Bicciacese), or Podostemads with Liverworts — there will still be a great resemblance be- tween them. But among flowerless plants there is a far lower form of structure, with which flowering plants have nothing comparable, where species are reduced to mere threads, as in Confervas, or small clusters of cells, as in STRUCTURE.] FLOWERLESS PLANTS. 83 Brit tie worts (Diatomseceae), or simple cells, as in some of the genera constituting Blights among Coniomycetous Fungals. And even in these instances where flowering and flowerless plants resemble each other, the similarity is confined to the organs of vegetation, no resemblance being usually discover- able, except by the aid of forced analogy, between the repro- ductive organs of the two great forms of plants. It would seem, indeed, as if the mode of producing reproductive organs was wholly changed among flowerless plants, and that such resemblances as sometimes appear to remain, are but the result of general tendencies which, perhaps, are never lost in any part of the kingdom of plants. It is, therefore, mainly to the peculiarity of the reproductive organs that the following remarks will have relation. There are two main questions which require to be con- sidered independently of the special circumstances that vary from one natural order to another. They are : 1 . Have flowerless plants sexes? 2. Have they seeds ? The question of SEXES has long divided the botanical world. There are some who, like Linna3us, assume sexuality to be indispensable, and who therefore find traces of it every where. There are others who, perceiving no necessity of the kind, demand proof of the so called sexes being so, and refuse to acknowledge sexes in the absence of the same proof as is required among flowering plants. The first are sometimes satisfied with assuming the existence of a male and female principle even in the cells of Confervse, where nothing visible exists ; the second are of opinion, that what can neither be seen, nor detected otherwise, cannot be said to have existence. The former opinion is maintained, with his usual acuteness, by Mr. Thwaites, as will be seen hereafter under Mosses and Brittleworts. And the point may be conceded in the view which he takes of sexuality : for it is not so much the mere presence of sexes, or of a mysterious sexual essence, that is denied, as that the organs called sexual in flowerless plants, are of the same, or a similar, nature as those known to be sexes in the higher orders. G 2 84 FLOWERLESS PLANTS. [BOOK i. The late Mr. Griffith may be regarded as the most ex- perienced modern botanist who has supported the sexuality of flowerless plants ; and, therefore, in justice to so great an ob- server, I cannot do less than quote his words from an excellent paper in the Nineteenth Volume of the Linnaan Transactions. "The question of the sexuality of Acotyledonous plants is so intimately connected with the subject of vegetable em- bryology, that I trust I shall be pardoned for hazarding a few observations derived from personal experience. The more developed Acotyledonous plants, which I take to be Filices, Lycopodinese, Isoetes, Marsilea, Salvinia, Azolla, Hepatic&e, and Musci, appear to me to present two very dis- tinct types of organisation, at least, as regards the female organ. In one type there is an evident pistillum containing an ovulum, and this appears to be generally connected with limited development of the organs of vegetation. In the other there is no evident pistillum, nor any palpable point on which analogy would indicate that the male influence would be exerted. That type is also remarkable for the de- velopment of the organs of vegetation. In Musci, the evidence of the mutual action of the sexes, appears to me very satisfactory ; the usual discoloration of the stigma and canal of the style is distinctly observable, and is followed by changes, confined, however, to change of situa- tion, affecting the cell pre-existing in the cavity of the ova- rium, and which is analogous to a Phaenogamous ovulum. In Hepaticae, particularly the vaginulate species, the circum- stances would appear to be the same ; and in the evaginulate ones, and, perhaps, also in Kiccia, still nearer approaches are made by the changes which the pre-existing cell undergoes to the ovulum of Phsenogamous plants. In the Azolla I have examined, which is the only other plant which appears to me pistilligerous, (he had at that time no knowledge of the development of Salvinia), the pistilla in each involucre are two, and both present the appearance so generally characteristic of fertilisation. The changes subse- quent to this are, however, very different, giving rise in one pistillum to the supposed male, in the other to a series of sporules derived from the characteristic dividing process. STRUCTURE.] FLOWERLESS PLANTS. 85 On Lycopodineae / have no observations, and on Filices merely a few surmises to offer. I believe that every species will be found to present a male apparatus, which, I think, was first pointed out by the great Hedwig, and subsequently by M. Link. I have lately alluded to it without having any previous knowledge of the labours of the two above-mentioned botanists. The fertilisation of Ferns I believe to be inter- preted by Anthoceros, .provided my observations on that genus be found to be correct. The only difficulty exists in the anthers not appearing, in some cases at least, to dehisce; but I beseech botanists not to cast away the opinion of the very important nature of these bodies on a solitary objection ; they will remember that until very lately an absorptive pro- cess was generally adopted to explain the fecundation of Asclepiadese and Orchideae, and even adhered to, when a beautiful train of reasoning and observation had reconciled them, in all the essential points, to the ordinary plan. With regard to Marsilea, I have to remark that the obser- vations of M. Fabre, as given by M. Dunal (Ann. Sc. Nat., N.S., t. vii. p. 221), scarcely agree in one particular with some observations on a Marsilea, I believe M. quadrifolia, made by myself at Bamo, on the Irrawaddi, in 1837. In the species I then examined I found the organs to be of two distinct kinds attached to the veins of the involucre. Of these two kinds, one only is subsequently subjected to the usual ternary or quaternary division, from which result bodies altogether similar to the acknowledged spore of other Acotyledonous families. The other body has no analogy, in my opinion, to the acotyledonous form of anther. InM.Fabrei, however, the females have been represented as having curious analogical resemblances to the Phaenogamic pistillum ; and what is, perhaps, more extraordinary, the anthers are said to be simple sacs, containing granules and molecules, and appa- rently are similar to the pollen of certain Naiades, Balano- phoreae, Rafflesiaceae, &c. In Isoetes the males of authors are nothing but modifications of the spore ; and in I. capsularis, Roxb., they seem to be merely temporary modifications : they have, in fact, so pre- cisely a common development that it is scarcely allowable to 86 FLOWEELESS PLANTS. [BOOK i. allot to them the performance of such opposite functions as those usually attributed to them. The true male may, perhaps, be found in the cordiform, fleshy lamina above the receptacle of the spores, from which it is separated by a lamina, perhaps analogous to the indusium. The transition between the two types exists in Anthoceros, which, in the development of its anthers and in habit, has much in common with the pistilligerous type. In this genus the male influence is first exerted on the surface of the frond, and thence is extended through the upper parenchyma to that part of the substance of the frond from which the reproduc- tive organ is to originate. So far as I know, nothing like a pistillum appears to exist : and though there is a calyptra, it has nothing, except situation, in common with the calyptra of Musci and Hepaticae, being only that portion of the paren- chyma between the surface of the frond and the spot whence the young reproductive organ has originated. I take it to be a valuable example, inasmuch as it shows, if my explanation be correct, that the male may not only act successfully without a pistillum, or any similar co-existing body, but that it may act mediately. Consequently, Ferns are easily, and I think fairly, explainable, provided the glan- dular hairs are allowed to be the males. And in what do they differ from the anthers of certain Musci and Hepaticse, or from the anthers of Phsenogamous plants, when they are cellular, undivided bodies containing grumous molecular matter ? In regard to points like these, most botanists have, like some zoologists, pitched upon one standard of organisa- tion, and that at the wrong end of the scale. But those who look for a smaller degree of complication in low organisations, or for a greater degree of reduction to the elementary sub- stances, will, I think, not only admit that the anthers of all the above families, so far as they have been well observed, have a marked correspondence with, but that they are also analogous to, very young anthers of Phanerogamous plants. I might ask what they have in common with gemma ? Is the structure of a gemma compatible with a cellular sac contain- ing a grumous matter ? Is the function of a gemma more compatible with such a sac, often inclosed in a cavity in the STRUCTURE.] FLOWERLESS PLANTS. 87 frond, from which it does not escape, and in which they are, functi officiis, to be found in the shape of withered empty sacs?" In the Calcutta Journal, the same author repeats these opinions in a more concise way. " It appears to me," he says, " sufficiently plain, that in the higher Acotyledonous plants, in which I include Filices, Lycopodineae, Isoeteae, Equiseteae, Marsileacese, Salvinidse, Musci, Hepaticae, Cha- raceae, there are at least two modifications of the female organ representing the modifications of the same organ of Cotyle- donous plants. The term Pistillum has been applied to the female organ of Mosses by some first-rate botanists, though not without violent opposition from some systematists. Since the exami- nation of Balanophora, its application is, if possible, still more legitimate. In my opinion it is not to be doubted, that not only have Musci and Hepaticae a pistillum, but that this contains an ovulum. The analogies presented by the plants which form the subject of this communication, to those Cotyledonous plants in which the ovulum is entirely naked, either, as is supposed to be the case in some, without a carpel leaf, or with that organ in an expanded not a convolute state, are, I think, equally striking. It may be worthy also of remark, that in proportion as Acotyledonous plants become, so to speaky less pistilligerous, their vegetative organs appear to be more developed. This is evident if a Fern be compared with a Moss. And it seems to be so closely followed up, that Salvinia which has less, perhaps, of the atropous phaenogamous ovulum than Azolla, has its organs of vegetation considerably more developed." If the reader will turn to the words which are here printed in Italics, he will at once perceive upon what inconclusive arguments these opinions are founded. Not the slightest proof is adduced from experiment that the parts called male and female exercise the function of the sexes. No attempt is made, for none could be made, to show that they are ana- logous to the undoubted sexes of Flowering plants, because of their being analogous in structure ; but the whole argument 88 THEY HAVE NO SEXES. [BOOK i. is made to turn on if, or perhaps, or trifling coincidences. It is to be remarked, too, that an appearance of speciousness is given to doubtful arguments by the employment of the terms style, stigma, pistillum, ovarium, ovule, and anther, as if such organs really existed; the fact being, that the use of the terms is wholly arbitrary, and that its fitness is the first point to establish. It is, moreover, curious to observe upon what false ground this admirable observer, but bad rea- soner, stands when he is obliged to assume the existence of some incomprehensible power of intus-susception, for no better reason, as it would seem, than that it has been proved not to exist in Flowering plants. Without pretending to defend those who have supposed the antherids of Flowerless plants to be gemmae, that is, buds, I may also remark, that the supposition involves no such absurdity as Mr. Griffith supposed ; because the essence of a bud is its cells ; because all cells are capable of forming buds ; and, therefore, because as all antherids consist of cells, they too may possibly form buds. That Flowering plants have no seeds, properly so called, that is to say, no propagating bodies, formed as a consequence of the contact of sexes, is certain, if the foregoing arguments have any force. The actual condition of the reproductive bodies, or spores, of flowerless plants confirms the opinion; for with most botanists it is not now a question of whether spores are seeds, but whether spores are not of the same nature as pollen. " The identity of the spores of Acotyle- dons," said Mr. Griffith, "and the pollen of Cotyledonous plants is, perhaps, strengthened by the curious resemblance of the fructification of Equisetum to the male apparatus of Cycads ; in which also the pistillary apparatus, in this view to be looked on as a sort of nidus, is of great simplicity." This opinion seems to have originated with Mr. Valentine in 1833, as will be fully shown hereafter in speaking of Mosses. Without for a moment expressing an opinion favourable to such a supposition, which I believe to be quite unfounded, I only refer to it for the sake of showing how entirely different spores must be from seeds to have given rise to such a STRUCTURE.] THEY HAVE NO SEEDS. 89 speculation ; for what botanist would think of pronouncing true seeds to be pollen grains ? Even Mr. Griffith, in attempting to show an analogy between spores and seeds, does not pretend to make out any identity between them ; and his whole account is that of a growing point, — a focus of vitality, — and not a seed. One cannot but wonder that so clever a man should not have perceived how entirely the following criticism upon his brother botanists applied to himself. " The terms used in most of the characters are in several instances unintelligible, as generally is the case when a name is made to pass for an explanation, or when the application of a name is founded on mistaken ideas of the nature or analo- gies of certain parts. In the late work on Genera by M. Endlicher, I find the terms indusium, calyptra, and colu- mella, all in use. And in a note, other general analogies are so extended as to refer one of the organs to the type of a fflos monadelphus ovario infero/ Now of the terms above cited, there appears to me only one (calyptra,) capable of legitimate application, but only as far as regards mechanical function. The difference otherwise is very great; for in Azolla the calyptra is nothing more than what is presented by every dehiscentia circumscissa of a fruit, and is limited to one only of the capsules ; while in Mosses and all calyptrate Hepaticse, it is the pistillum displaced from its base at a remarkably early period. A more real analogy of this part in Azolla is to be found, perhaps, in the seed of Lemnaceae during germination. The term indusium is applied to the capsule itself, whereas, correctly speaking, it is only applicable to a covering of capsules, of a partial or general nature, derived from the surface of the foliaceous body or frond, on which the capsules are situated. This term indusium, which should be distinguished from involucrum, is at most only applicable to Azolla. A columella is the remains of an originally continuous, solid, cellular tissue, unaffected during the development of the spores ; it is a continuation either of a partial or a special axis. It may, I believe, be justly considered analogous to the connectivum of a bilocular anther, or the cellular tissue between the cavities of a plurilocular anther. In Azolla it 90 FLOWEBLESS PLANTS [BOOK i. does not appear to be even solid. It may be seen, also, that the same character gives an indusium to one, a calyptra to the other body, while the application of the term calyptra ceases to be even mechanically correct from being applied to the whole capsule." " In the sporula, so called," he says, " of the more developed Acotyledonous plants, we have organs consist- ing of two envelopes ; the inner of which contains granular matter, has remarkable powers of growth, and, so far as function is concerned, appears to be alone essential. The proper stimulus calls this membrane into growth, and from the apex of its extension cells are developed; from these others again are produced ; and from the centre of the mass thus formed, originates at a certain period the growth of the true axis. Similar phenomena take place in the formation of the seed of Phaenogamous plants, with this difference, that the albumen, unlike, perhaps, the thallus of the Acotyle- donous plant, is not a direct growth from the pollen tube. Such other differences as appear to exist are of minor importance ; they consist in the different nature of the stimulus calling forth the extension of the inner membrane, in the condensation of the growth forming the seed, which may be reasonably inferred to arise from the confined situa- tion in which they occur, and in the cells composing them containing fecula, not green globules, also apparently a con- sequence of the confinement alluded to. The functions of the intermediate growths are in both precisely the same, viz., that of nourishing the young axis until it is sufficiently ma- tured to enable it to maintain an independent existence. " The germination of such Acotyledonous plants appears, therefore, to me to be analogous to the development of the seed of Cotyledonous plants, and the perfect state of the lower is analogous to the imperfect state of the higher organi- sation. And to a similar observance of the phases of develop- ment I am tempted to attribute the prevalence of albumen in Monocotyledonous plants, although this is apparently strongly contradicted by the occurrence of the most exalbu- minous and perfect Monocotyledonous embryos in the least organised plants of the class ; and, perhaps, equally so by its prevalence in the monopetalous division of Dicotyledons. STRUCTURE.] HAVE NO SEEDS. 91 " The analogy between the spore and the grain of pollen has long been remarked ; and its extended application to the processes, constituting germination in the one instance, and the formation of the seed in the other, was given by Mr. Valentine in 1833. I think I am correct in naming it analogy rather than affinity, from considerations derived both from development and functional powers. For the spore of these particular or more developed Acotyledons is not pro- duced by a comparatively simple process as the pollen of Cotyledonous plants is, but is the result of a process as complicated, if not more so, than the development of the seed, and, in addition, presents in its first stages very curious similarities with the development of a true ovulum. Both agree in being set in action by the agency of a comparatively simple structure ; but the early complication of the process in the higher Acotyledonous plants would at once lead me to suspect that the organs alluded to are not strictly similar ; for the earlier we proceed in our investigations, the more marked should be the resemblance, and the more simple both struc- ture and function. The powers of growth in the two are remarkably contrasted, and will be still more so, if the albu- men be ultimately found to be derived from the female. M. Schleiden, on the contrary, is of opinion, that between the spore and the embryo there is an affinity amounting to fundamental unity; and Mr. Valentine not only holds the same opinion, but, overlooking the obvious difficulties to which M. Schleiden has adverted as presented by some of the higher Cryptogamic families, denies to these plants entirely a provision similar to that of the pistillum of Pha- nerogams." (Linn. Trans., vol. xix.) How little analogy there really is between the spores of some flowerless plants and the seeds of the higher orders is sufficiently shown by the following excellent account of the formation of that of Vesiculifera concatenata, an Algal, by Mr. Thwaites : — " This plant occurs in ponds on a common near Bristol, and is of a pleasant pale apple-green colour. The cells are usually from five to seven times as long as broad, and are lined with but a small quantity of endochrome, which is 92 SPORE OF VESICULIFERA. [BOOK i. disposed in a reticulate manner. Some of the cells, however, may be observed to be slightly inflated, and to contain a larger amount of endochrome than the rest : in each of these inflated cells a spore is subsequently formed, and in the fol- lowing way: — The endochrome, after attaining a certain degree of density from an increase in its development, not from any derived from a contiguous cell, moves towards one end of its cell ; it (the endochrome) shortly becomes divided into two very unequal portions, the larger and terminal one of which becomes converted into the spore, and the smaller portion is found to be separated from this by a single septum. A process has, in reality, taken place analogous to the fissi- parous division of the cell of Zygnema ; two cells have been formed within the original one, but in the Vesiculifera one of these new cells is the spore. This is a fact of considerable physiological importance." The same observer found that in Vesiculifera'sequalis, the process of the formation of the spore is similar. In that species, however, he was able to trace the mode of develop- ment of the two or three contiguous spores, which are some- times to be seen in the filaments of this species. The first spore is formed in the way he previously mentioned, and arrives at considerable maturity before there is any appear- ance of one, contiguous to it, being produced; but it may then be seen that the smaller portion of endochrome, which had been separated just previously to the first spore being formed, and which then occupied but little space in the cell, has become considerably increased in amount, an increase having also taken place in the length of the cell ; at length the process of division, &c., occurs as before, and a second spore is formed adjoining the first. The formation of a third spore involves a similar chain of phenomena. The spores of flowerless plants are usually regarded as dif- fering from seeds in not germinating from any fixed point, but from whatever part is exposed to moisture and darkness. This, however, is denied by Mr. Valentine in the case of Pilularia, " for it is quite certain in that instance that ger- mination invariably takes place at a fixed spot, which may be pointed out before germination has commenced. It is at STRUCTURE.] PILICALS. 93 that part of the sporule indicated by the three radiating lines which appear to have been produced by the pressure of the three other sporules that originally helped to constitute the quaternary union ; and as the spores of all the other tribes appear, according to Mohl, to be developed in similar unions, it is most probable that similar lines indicating a valvular dehiscence also exist on them. This is certainly the case in some Mosses, for instance, in (Edipodium, and in Isoetes, Lycopodium, and Osmunda regalis ; and in those instances where such a structure is not visible, it is probably owing to a thickening of the membrane, or a deposition of opaque matter on its surface, as in Pilularia." (Linnaan Transactions, xviii.) But it is time to proceed to particulars. 1. THE PILICAL ALLIANCE.* (Ferns, Dan&ads, Adders Tongues.} FERNS are plants consisting of a number of leaves, or fronds as they used to be called, attached to a stem which is either subterraneous or lengthened above the ground, sometimes rising like a trunk to a considerable height. Some of them are the largest of known vegetables in which no organs of fructification analogous to those of phsenogamous plants have been discovered. Their stems often acquire the height of as much as fifty or sixty feet, or even more, and in that case are usually unbranched, of the same thickness at the upper and lower ends, and grow exclusively at the point. The surface of the stem is often hairy or shaggy, sometimes spiny, and in all cases is more or less copiously furnished with callous points, which render it rough like shagreen leather, or co- vered with roots, sometimes entangled into a compact layer much thicker than the trunk itself, and appearing to be the extension of the callous points. The anatomy of tree ferns has been skilfully elucidated by Mohl, to whose treatise upon the subject (Martins, Plant. Crypt. Bras. p. 40.) the reader is referred for the details of their curious organisation. I must content myself with a * See « Vegetable Kingdom," p. 74. 94 FILICALS. [BOOK i. very general statement. The trunk is covered with a hard rind, occupying the place of bark, two or three lines thick, and consisting of hard brown parenchymatous and prosen- chymatous tissue, the latter, if present, being on the inside. Within the rind is a mass of parenchymatous thinner-sided tissue, which is analogous to the horizontal cellular system of exogens and endogens. The wood is formed by concave or sinuous plates, whose section has a lunate or wavy form, and which are closely arranged in a circle next to the rind, en- closing a column of parenchyma, just as the wedges of wood in exogens enclose a similar column of pith ; and in like manner there are openings between the plates, through which the subcortical and medullary parenchymas communicate. Each plate consists externally of several layers of hard brown prosenchyma, next within which is a pale stratum of thin- sided parenchyma, and in the centre of all is a soft pale mass of trachenchyma, consisting of large scalariform and spiral vessels (sometimes -£§ line in diameter) mixed with soft parenchyma. Externally the stem is marked with long, or rhomboidal scars, .the surface of which is broken into nume- rous hard ragged projections which represent the broken communication between the trunk and the leaves, by the fall of which the scars are produced. Next the apex of a trunk the scars are always arranged with great regularity, but towards the lower part of the stem they become much longer, irregular in form, and are separated by deep furrows ; from which it is to be inferred, that, although in these plants no new parts are added, except at the point of the trunk, yet that the parts after being formed do grow both in length and breadth. Below the scars of the leaves are often (always ?) found elliptical or roundish perforations, filled with a powdery matter. These have no obvious analogy in other plants, unless they are to be compared to the perforations in the rhizome of Nymphsea, which, however, according to Trecul, are caused in that plant, by the falling away of roots. (See last volume.) Their petioles, or stipes (rachis W. j peridroma, Necker), consists of sinuous strata of indurated, very compact tissue, STRUCTURE.] FILICALS. 95 connected by cellular matter ; and the wood of those which have arborescent trunks is formed by the cohesion of the basis of such petioles round a hollow or solid cellular axis. The organs of reproduction are produced from the back or under side of the leaves. In Polypodiaceae, or what are more commonly called dorsiferous ferns, they originate, either upon the epidermis or from beneath it, in the form of spots, at the junctions, margins, or extremities of the veins. As they increase in growth they assume the appearance of small heaps of granules, which heaps are called sort. If examined beneath the microscope, these granules, commonly called sporangia, theca, capsules, or conceptacles, are found to be little, brittle, compressed bags formed of cellular membrane, partially sur- rounded by a thickened longitudinal ring (gyrus, annulus, gyroma], which sometimes at the vertex loses itself in the cellularity of the membrane, and at the base tapers into a little stalk. The sporangia burst with elasticity by aid of their ring, and emit minute particles named spores or sporules, from which new plants are produced : as from seeds, in vegetables of a higher order. Interspersed with the sporangia are often intermixed articulated hairs ; and, in those genera in which the sporangia originate beneath the epidermis, the sori, when mature, continue covered with the superincumbent portion of the epidermis, which is then called the indusium or invo- lucrum (membranula, Necker ; glandules squamosa, Guettard), In Trichomanes and Hymenophyllum, the sporangia are seated within the dilated cup-like extremities of the lobes of the frond, and are attached to the vein which passes through their axis, which is then called their receptacle. In Gleicheni- acese, the sporangia have a transverse complete, instead of a vertical incomplete, ring, and they are nearly destitute of stalks ; in others the sori occupy the whole of the under sur- face of the leaf, which becomes contracted, and wholly alters its appearance : the sporangia have no ring, and the cellular tissue of their membrane is not reticulated, but radiates regularly from the apex. In these plants it has been in vain endeavoured to prove the existence of organs of fecundation. Nevertheless, as it was difficult for sexualists to believe that plants of so large a size 96 FILICALS. [BOOK i. were destitute of such organs, it has been considered indis- pensable that they should be found ; and, accordingly, while all seem to agree in considering the sporangia as female organs, a variety of other parts have been dignified by the title of male organs : thus, Micheli and Medwig found the latter in certain stipitate glands of the leaf; Stsehelin, Hill, and Schmidel, in the elastic ring; Koeleruter, in the indusium ; Gleichen, in the stomates ; and Von Martius, in certain membranes enclosing the spiral vessels. Blume, Sprengel, Presl, and especially Link, imagine the anthers of ferns to be long clavate threads, separated by septa into articulations, generally simple, rarely ramified ; the last articulation being thicker, and filled with a delicate granular mass. This mass is said to be at times exuded at the last articu- lation, when it surrounds it as a crust. Such threads are fre- quently longer than the sporangia, and are easily distinguished from the latter when young. Some botanists think it probable that these may really be the stamens of ferns. Link, who says he has found them, after frequent search, in most of the ferns which he subjected to microscopical examination, has published some beautiful drawings of them. There is not, however, at present, the slightest evidence to show that they possess any male properties. The late Colonel Bory de St. Vincent contended that im- pregnation may take place in plants without the agency of pollen, and he affirmed that hybrid ferns exist ; which, if true, would render it impossible to deny the existence, in this large order, of sexual organs ; and, in that case, the threads de- scribed by Link might be supposed to perform the office of stamens ; but the latter botanist has not availed himself of the supposed fact of hybrid ferns being producible. On the contrary, in the following observations he entirely disbelieves that statement, as I do : — "The remarkable phenomenon which M. Martens first observed at Lowen, in the botanical garden, that an inter- mediate species of fern grew where Gymnogramma calome- lanos and chrysophylla were situated, has also been observed by Bernhardi in Erfurt (Ottos and Dietrichs Flora, 1840, pp. 249, and 325). A fern has grown in the botanical garden of STRUCTURE.] PILICALS. 97 that place, which holds a middle rank between Gymnogramma distans and chrysophylla, species which are cultivated in the same garden, and had been frequently standing next each other. The frond of this intermediate fern is doubly pinnate, decreasing towards the upper part ; the shape of the pinnae and pinnate divisions holds a middle rank between the shape of these parts in its progenitors. The white powder of G. distans is scattered about at the base of the fronds and the pinnae, where they are attached to the footstalk, and the yellow powder of G. chrysophylla, but rather paler, is seen on other parts. M. Bernhardi considers these forms as real hybrids ; he recommends particular attention to the fructi- fication of the fern in these species of Gymnogramma ; he thinks that if his assertion respecting the male fructifying parts of these plants should be confirmed, the phenomenon may be more readily explained, than if other parts are re- garded as anthers. M. B. rejects the opinion too hastily, that the species of ferns, of which such intermediate forms have been observed, may be modifications of the same species ; indeed, these species are very similar, and ferns are by no means so constant in their forms as the author thinks ; on the contrary, they change very frequently, and much more so than other plants. It is often the case, that we see long and short, pointed and blunt pinnae, on one and the same frond of the larger Polypodiaceae." He, therefore, rejects the idea of imaginary hybrids proving that ferns have sexes ; and, with regard to his own supposed anthers, he observes, that, " If any parts are to be regarded as anthers, they evidently are those which Blume first of all definitely indicated, and which are represented in the same part of the Icon. Select. Anatomica Botanicce, tab. 3, fig. 1 — 5 ; they certainly have the greatest analogy with anthers, although I by no means attribute to them the same functions as are possessed by the anthers of phanerogamous plants. For we need only reflect upon the eye of the mole, which certainly cannot see with it, to be convinced that nature sometimes also arranges things for no particular purpose. Provided even that these anthers of the fern, or the parts assumed to be such by Bernhardi, really possessed the function of impregnation, I yet cannot see how VOL. IT. H 98 FTLICALS. ADDEES TONGUES. [BOOK i. hybrids can be produced in this class of plants. With regard to the anthers of Blume, they are too near the pistils of the same species ; and as to those of Bernhardi, the pistils in other species are situated at so remote a locality, that it is impos- sible to explain how the one could get to the other." (Ray Reports.} " The germination of ferns is simple : the shell of the spore bursts regularly or irregularly, and out of it the kernel extends in the form of a foliaceous expansion, which subse- quently forms a bud, whence the plant proceeds under the form which is proper to its nature. This mode of germina- tion possesses some similarity to that of Monocotyledons; but here the evolution of the kernel is a mere state of rapid transition." (Link.) In ADDERS TONGUES (Ophioglossaeese), a remarkable race of Ferns, the fertile leaf is rolled up in two lines parallel with its axis or midrib, and at maturity opens regularly by trans- verse valves along its whole length, emitting a fine powder, which, when magnified, is found to consist of particles of the same nature as the spores found in the sporangia of other ferns ; here there are no sporangia, the metamorphosed leaf probably performing their functions. Such is my view, of the structure of Adders Tongues ; but by other botanists it is described as a dense spike of two-valved capsules, dehiscing transversely. 2. THE LYCOPODAL ALLIANCE.* ( Clubmosses, Pepperworts.} CLUBMOSSES (Lycopodiacese) are leafy plants with the habit of gigantic mosses. Their leaves and stem have the same structure as those plants, except that the former are some- times provided with stomates, and the .latter with a central bundle of vessels. Their organs of reproduction are kidney- shaped two-valved cases, usually called thecce, sporocarpia, conceptacles, or capsules, either, 1. filled with minute powder- like granules, which, in consequence of lateral compression, * See « Vegetable Kingdom," p. 68. STRUCTURE.] LYCOPODS THEIR OOPHORIDS. 99 from being spherical, acquire the figure of irregular polygons ; these are the Antheridia of modern writers ; or, 2. containing three or four roundish fleshy bodies, marked at the apex by a three-legged line, and each of which is at least fifty times larger than the granules contained in the first kind of theca ; the latter are also named oophoridia, and are said by Brotero to burst with elasticity. The first kind of theca is found in all species of Lycopodiaceae ; the second is only found in a few. The contents of both are believed to be sporules ; but no satisfactory explanation has yet been offered of the cause of their difference in size, and probably also in structure. I would suggest that the powder-like grains are true sporules, and that the large ones are buds or viviparous organs, as has already been stated by Haller and Willdenow. A writer in the Transactions of the Lmrman Society has figured and de- scribed the growth of the larger grains of Lycopodium denti- culatum, and he considers that they exhibit the germination of a dicotyledonous plant ; but, independently of any mistrust which may attach to the account, it is obvious enough that his own drawings and description represent a mode of germi- nation analogous, not to that of dicotyledons, but rather to that of monocotyledons, and also reducible to the laws which govern the incipient vegetation of a bud. The powder-like sporules are inflammable, and have been supposed by Haller, Linnaeus, and others, to be pollen, while the larger have been considered seeds ; and to a part of the surface of the theca the office of stigma has been attributed. The thecse themselves have been fancied to be male apparatus by Koelreuter and Gsertner. Both kinds of theca, the oophoridium, and antheridium, have been critically examined by Karl Muller, whose obser- vations are the latest upon the subject. " The oophoridium," says this author, " is the whole meta- morphosed terminal bud of a main axis. It is therefore an axial organ." This opinion is supported upon the following grounds : — The position of the oophoridium is opposite the spike in the early condition, and hence he regards the oophoridium and spike as two metamorphosed branches into which a main H 2 100 OOPHORIDS OF LYCOPODS. [BOOK i. branch has just divided. It is only at a later period that both oophoridium and spike appear to belong to the same axis. K. Muller thinks that there can be so little doubt about our having, in this case, to do with two branches, that, in the absence of other argument, this mode of development alone would justify his opinion. All that is requisite to form a branch occurs in the oophoridmm ; it is covered by two leaves, and they are to be regarded as the two first of what otherwise becomes an oophoridium. He finds, moreover, that near the oophoridium and the spike is often produced the same root which appears in the bifurcation of a main axis ; that in L. denticulatum, &c., only one oophoridium is found on each fruit-bearing axis, which stands in direct con- nection with the scattered fructification of the said axis. The branches of L. denticulatum divide, he thinks, too fre- quently for the branch to produce many oophoridia. It is too thin to form a main axis out of which oophoridia might be developed. It is different with L. selaginoides. " Here the axis of the fruit is very thick, and thus it is suited to form branches which may develope into oophoridia. Another proof is, that in the young condition the oophoridia are all compressed, as the branch of L. denticulatum always is, since the oophoridium is, in fact, only the transformed apex of the branch." The internal direction of the vascular bundle belonging to the oophoridium is a still better evidence, for it runs into its pedicel. In short, Karl Muller regards it as a modification of the growing point, an hypothesis which he thinks is rendered incontrovertible by an anomaly which he once observed where both branches of the fruit-bearing axis had been transformed into oophoridia. " Here, of course, the spikelet was wanting, and two oophoridia were opposed to each other, the most complete proof that the terminal bud of that branch had been transformed into an oophoridium, which properly should have produced a branch." " Conse- quently," he adds, "the view of H. Mohl and Schleiden in reference to the oophoridium, that this sporangium is a pro- duction from the leaf, is certainly incorrect; neither is it formed of carpellary leaves, as Bischoff endeavoured to show." The next question is, the import of the antheridium ? This STRUCTURE.] ANTHERIDS OF LYCOPODS, 101 much he thinks certain, " that the antheridium can be 110 product from a leaf, since it is formed from the axis contem- poraneously with the leaf. As little can we regard it, with Bischoff, as formed by the growing together of leaves. Besides, Mohl has already triumphantly refuted this view. But that we have to do with a metamorphosed bud, on the contrary, cannot be disputed; since the first, rounded antheri- dium-spherule possesses all the peculiarities of a bud, epider- mis and a formative cell-contents. The only question is, whether we are to regard this bud as analogous to those so often met with in the axils of the leaves." He considers it a lateral bud (the bud of a twig), which is only distinguished from the terminal bud of the branch developed into the oophoridium by the circumstance that the latter is a principal branch, which possibly was capable of a more extensive deve- lopment into branch and foliaceous organs, while the twig which is developed into an antheridium is but a small particle of such a main branch. " That it is a twig, appears to me to be shown by the internal structure of the fruit-axis, since from its central vascular bundle are given off real lateral branches to each bud (antheridia) . Yet it must be freely admitted, that the vascular bundle does not actually run into the peduncle of the antheridium, but terminates before reach- ing it, and it is merely elongated cellular tissue which proceeds from the vascular bundle into the peduncle." (See the whole paper illustrated with figures in the Annals of Natural History, vol. xix.) PEPPERWORTS (Marsileacea3) consist of plants differing so much from each other that the genera require to be examined separately. Of Marsilea the most complete account has been given by M. Fabre. In Marsilea Fabri the fructification consists of a two-valved coriaceous involucre (sporocarpium, Endl.), having its valves held together by a central line continuous with the stalk : this involucre seems to be a modified leaf. From the stalk there rises a mucilaginous ring to which adhere minute ramifications of the spike, terminating in oblong spikes covered with fructification. After a time the mucilaginous 102 PILULARIA. [BOOK i. ring detaches itself from the stalk at one end, straightens, and carries up with it the spikes of fructification, whose connec- tion with the stalk is then destroyed. The spikes are at first enveloped in a mucous membrane, and are composed of two sorts of bodies closely packed together, and considered by M. Dunal to be ovules and anthers. These bodies are some- times intermixed, sometimes stationed separately from each other. The so called ovules are little white semitransparent bodies, surrounded by a sort of projecting hood, beyond which a narrow papilla projects : this papilla is always turned towards the anthers. The latter are little flat parallelopi- pedons, rounded at the two ends ; they consist of a mem- branous sac of great tenuity, in which are found numerous grains of spherical or elliptical pollen. (Ann. Sc., n. s. vii. 227. t. 12, 13.) M. Fabre is represented as having proved experi- mentally that the latter impregnate the former ; and he has traced the ovules from their first impregnation to their com- pletion, and seen and described their germination. (Id. ix. 115, t. 13.) It appears that no trace of embryo is discoverable in the ripe seed. In Pilularia the organs of reproduction lie in hairy oval cases, or sporangia, whose interior is divided into four cells filled with bags arranged in four lines as in parietal placentae, some containing a germinating body or sporule, others filled with a powdery matter. The first have been regarded as pistils, the latter as anthers. But Mr. Valentine has shown, in a very detailed memoir, that the so called anthers are merely abortive spores, as I long ago suggested. (See Lin- naean Transactions, vol. xviii. tt. 34 and 35.) Salvinia and Azolla have been the subject of some elaborate observations by Mr. Griffith, (Calcutta Journal, vol. v.) He regards them as having true sexes, the male being certain necklace-shaped threads found at an early stage, in contact with what he denominates an orthotropous ovule. But strange to say, this so called ovule, instead of giving birth to an em- bryo, becomes the parent of reproductive bodies of two totally different kinds, having not even the smallest resemblance the one to the other, although the matrix out of which they are evolved is identical at an early period of the organisation. STRUCTURE.] SALVINIA. AZOLLA. 103 The following is the substance of his descriptions of Salvinia and Azolla : — Salvinia. — Male organs ? articulated hairs on the stalks of the ovule, each joint containing a nucleus and a brownish fluid ; Ovula nearly sessile, concealed by the roots, and partly covered with hairs ; tegument open at the top ; mature repro- ductive organs solitary, or in racemes of 3-5, about the size of a pea, covered with brown rigid hairs. The upper ones of each raceme, (or lowest as regards general situation), contain innumerable spherical bodies, of a brownish colour and reti- culated cellular surface, terminating capillary simple fila- ments. These again contain a solid whitish opaque body. The other, which occupies the lowest part of the raceme, and which is the first and often the only one developed, is more oblong, containing 6-18 larger, oblong-ovate bodies, on short stout compound stalks : colour brown, surface also reticulated. Each contains a large, embossed, opaque, ovate, free body, of a chalky aspect : it is three-lobed at the apex, and contains below this a cavity lined by a yellowish membrane, filled with granular and viscid matter and oily globules. Azotta. — The growing points present a number of minute confervoid filaments, the assumed male organs, which at cer- tain periods may be seen passing into the foramen, the ovula becoming resolved into their component cells within the cavity of that body ; organs of reproduction in pairs, attached to the stem and branches, one above the other, concealed in a membranous involucrum ; ovula atropous, oblong-ovate, with a conspicuous foramen and nucleus, around the base of which are cellular protuberances ; capsules of each pair either difform, — in which case the lowest one is oblong-ovate, the upper globose, — or both of either kind, generally perhaps the globose, presenting at the apex the brown remains of the foramen, and still inclosed in the involucrum; upper half generally tinged with red ; the oblong-ovate capsule opens by circumcision; with the apex separate the contents, which consist of a large yellow sac contained in a fine membrane, the remains of the nucleus (or the secondary capsule). The sac is filled with oleaginous granular fluid, and surmounted by a mass of fibrous tissue, by which it adheres slightly to the 104 AZOLLA. [BOOK i. calyptra ; on the surface of the fibrous tissue are nine cellular lobes (the three upper the largest), which, when pulled away, separate with some of the fibrous tissue, and so appear pro- vided with radicles. The globose capsule has a rugose surface from the pressure of the secondary capsules within ; these are many in number, spherical, attached by long capilliform pedi- cels to a central much branched receptacle ; each contains two or three cellular masses, presenting on their contiguous faces two or three radiciform prolongations. In their substance may be seen imbedded numerous yellow grains, the spores. I profess myself unable to understand in what respects the parts here called males, females, ovules, capsules, &c. resemble those organs except in name. Indeed Mr. Griffith himself could not help feeling the weakness of his case when he observed that, " A difficulty may be considered to be pre- sented by the existence of the hairs round the base of the ovula. For these in their structure resemble what I suppose to be the male organs of Ferns, and also the anthers of certain Mosses and Hepaticse; although the terminal cell presents less granular matter than usual. In respect of the supposed males, Azolla presents greater analogies with phanerogamous plants, than either Musci or Hepaticse, in which nothing analogous to pollen grains has been, I believe, yet observed in the anther ; which again can scarcely in all cases be considered a grain of pollen, the view suggested by the contents. Still even with the objections before mentioned the analogies are as tenable, I think, as those existing between the pistilla of Mosses and of phanerogamous plants; those organs in the former being originally closed, in the latter, theoretically at least, originally open. General objections may also be raised from the fact of moniliform filaments similar to those of Azolla having been found on the capsule of Salvinia, unconnected apparently with fecundation, and on the dissimilarity of the supposed fecundating process in the two genera." Opinions in which I quite concur, regarding them indeed as being fatal to a sexual theory in this case. It has been thought that of the two kinds of grains or bodies above mentioned, the smaller are males and the larger females ; which has been supposed to be proved by the STRUCTURE.] SALVINIA. ISOETES. 105 experiments of Savi of Pisa. This observer introduced into different vessels, 1. the granules; 2. the grains; and, 3., the two intermixed. In the first two nothing germinated; in the third the grains floated to the surface and developed themselves perfectly. The observations have, however, been repeated by Duvernoy without the same result; and it is clear that Mr. Griffith's observations are entirely opposed to the view entertained by Savi, and Adolphe Brongniart, who thus describes the reproductive bodies of Salvinia and Azolla. In these genera he found at the base of the leaves membranous involucres of two sorts, containing different organs. One includes a bunch of cases (sporangia, Martius), containing only one grain in Salvinia, and from six to nine in Azolla. The integument of these cases is thin, reticulated, brownish, and does not swell in water : the pedicel which supports them appears, in Salvinia, to communicate laterally with the case. The other involucres, which are supposed to be male organs, have a very complex structure, and have been well observed by Brown. In Salvinia they contain a great number of spherical granules, attached by long pedicels to a central column : these granules are much smaller than the grains ; their surface is reticulated in like manner, and they do not burst by the action of water. Of Isoetes the evidence as to sexuality is equally unsatis- factory. " Delile has published an account of the germination of Isoetes setacea, from which it appears that its sporules sprout upwards and downwards, forming an intermediate solid body, which ultimately becomes the stem, or corm ; but it is not stated whether the points from which the ascending and descending axes take their rise are uniform. In Pilularia, Mr. Valentine finds that germination takes place invariably from a fixed point. Delile points out the great affinity that exists between Isoetes and Lycopodium, particularly in the relative position of the two kinds of repro- ductive matter. In Lycopodium, he says the pulverulent spore-cases occupy the upper ends of the shoots, and the granular spore-cases the lower parts : while, in Isoetes, the former are found in the centre, and the latter at the circum- ference. If this comparison is good, it will afford some 106 MUSCALS. [BOOK i. evidence of the identity of nature of these bodies, and that the pulverulent ones are at least not anthers, as has been supposed ; for in Isoetes the pulverulent inner bodies have the same organisation, even to the presence of what has been called their stigma, as the outer granular ones; so that, if Isoetes has sexes, it will offer the singular fact of its anther having a stigma. The anatomy of Isoetes is described by Mohlinthe Linnaea, xiv. 181." (Vegetable Kingdom, p. 73). 3. THE MUSCAL ALLIANCE.* (Urnmosses, Splitmosses, Horsetails, Scalemosses, Liverworts, and Crystalworts.) In the structure of URNMOSSES (Bryacese or Musci) and SPLITMOSSES (Andrseacese), neither vessels nor wo*ody tissue are employed. Their stem consists of elongated cellular tissue, from which arise leaves also composed entirely of cellular tissue without woody tissue ; the nerves, as they are called, or, more properly speaking, ribs, which are found in many species, being formed by the approximation of longer cells than those which constitute the principal part of the leaf. The leaves are usually a simple lamina ; but in Poly- trichum and a few others they are furnished with little plates called lamellae, running parallel with the leaf, and originating in the upper surface. At the summit of some of the branches of many species are seated certain organs, which are called male flowers, but the true nature of which is not understood. They are possibly organs of reproduction of a particular kind, for both Mees and Haller are recorded to have seen them produce young plants. Agardh says they have only the form of male organs ; and that they really appear to be gemmules. By Hedwig they were called spermatocystidia ; by others staminidia or ahtheridia. They are cylindrical, articulated, clavate, membranous bodies, opening by an irregular perfora- tion at the apex, and discharging a mucous granular fluid. Among them are found slender, pellucid, jointed threads, * Vegetable Kingdom, p. 54. STRUCTURE.] MUSCALS. 107 which are abortive antheridia. linger and Meyer have found what they call spermatic animalcules in the antheridia of Sphagnum and Hypnum. (Comptes Rendus, vi. 632.) But such bodies appear, notwithstanding their active motion, to be nothing more than loose spires. Whatever may be the nature of these organs, there is no doubt of the reproductive functions of the contents of what is named the sporangium, theca, or capsule, which, in Urn- mosses, is a hollow urn-like body, containing sporules : it is usually elevated on a stalk, named the seta, with a bulbous base, surrounded by leaves of a different form from the rest, and distinguished by the name of perichatial leaves. If this sporangium be examined in its youngest state, it will be seen to form one of several small sessile ovate bodies (pistillidia, Agardh ; prosphyses, Ehrhart ; adductores, Hedwig), enveloped in a membrane tapering upwards into a point ; when abortive they are called paraphyses. In process of time the raost central of these bodies swells, and bursts its membranous covering, of which the greater part is carried upwards on its point, while the seta on which the sporangium is supported lengthens. This part, so carried upwards, is named the calyptra : if it is torn away equally from its base, so as to hang regularly over the sporangium, it is said to be mitriform ; but if it is ruptured on one side by the expansion of the sporangium, which is more frequently the case, it is denomi- nated dimidiate. When the calyptra has fallen off or is removed, the sporangium is seen to be closed by a lid termi- nating in a beak or rostrum : this lid is the operculum, and is either deciduous or persistent. If the interior of the sporangium be now investigated, it will be found that the centre is occupied by an axis, called the columella ; and that the space between the columella and the sides of the sporan- gium is filled with sporules. The brim of the sporangium is furnished with an elastic external ring, or annulus, and an interior apparatus, called the peristomium : this is formed of two distinct membranes, one of which originates in the outer coating of the sporangium, the other in the inner coat; hence they are named the outer and inner peristomia. The nature of the peristomium is practically determined at the 108 MUSCALS. [BOOK i. period of the maturity of the sporangium. At this time both membranes are occasionally obliterated ; but this is an unfrequent occurrence : sometimes one membrane only remains, either divided into divisions, called teeth, which are always some multiple of four, varying from that number as high as eighty, or stretching across the orifice of the theca, which is closed up by it ; this is sometimes named the epiphragma or tympanum. Most frequently both membranes are present, divided into teeth, from differences in the number or cohesion of which the generic characters of mosses are in a great measure formed. For further information upon the peristomium, see Brown's remarks upon Lyellia, in the twelfth volume of the Linnean Transactions. M. Endlicher considers that the sporangium is formed by the adhesion of an external and internal series of organs ; and he calls sporangidium the inner, to which the peristo- mium belongs. (Genera Plantarum, 46.) The interior of the sporangium is commonly unilocular; but in some species, especially of Polytrichum, it is separated into several cells by dissepiments originating with the columella. If at the base of the sporangium there is a dilatation or swelling on one side, this is called a struma ; if it is regularly lengthened downwards, as in most of the Splachnums, such an elonga- tion is called an apophysis. The spores have no adhesion either to the sides of the spo- rangium or to the columella, but appear to be formed much in the same way as pollen. When they germinate they pro- duce capillary, articulated, green, branched threads, resem- bling Confervse ; and the leaves eventually appear from the axils of such branches.* From the foregoing description, it will be apparent, that * "Mr. Drummond, in a paper published in the 13th volume of the Linncean Transactions, proved, beyond a doubt, that the sporules of mosses germinate by emitting ' pellucid filaments ' from any points on their surface. I have myself examined the germinating sporules of Funaria hygrometrica, and I found that the brown coat burst sometimes in two or three places, but most frequently in one only ; and there protruded from each fissure a delicate transparent tube containing the moving particles, which had previously occupied the cavity of the sporules. These tubes, or, to speak with more precision, elongated cells, gra- dually increased in length, and, from exposure to light, became of a green colour. STRUCTURE.] VIEWS OF GRIFFITH. — OF VALENTINE. 109 the organs of reproduction of Urn-Mosses cannot be com- pared strictly to the parts of fertilisation of perfect plants. I must not, however, omit the opinion of other botanists upon this subject. The office of males has been supposed by Micheli to be performed by the paraphyses; by Linnaeus and Dillenius, by the sporangia; by Palisot de Beauvois, by the sporules ; by Hill, by the peristomium ; by Koelreuter, by the calyptra ; by Gaertner, by the operculum ; and, finally, Hedwig has supposed the males to be the antheridia. The female organs were thought by Dillenius and Linnaeus to be assemblages of antheridia; by Micheli and Hedwig, the young sporangia ; and, by Palisot de Beauvois, the columella. Mr. Griffith thought that the sexuality of Urn-mosses was established by a breaking up of the tissue terminating and closing the style (subsequently to the application of a parti- cular matter,) whereby the style becomes a canal opening exteriorly; by the browning observable in the orifice of this canal extending downwards until it reaches the cavity, &c. But it seems to me that the observations of Mr. Valen- tine dispose of the question conclusively, until some further evidence shall have been produced. " The most satisfactory refutation of the theory of Hedwig will be found in the anatomy of the pistillum, where the im- pregnation of the seeds is supposed by him to take place. It is strange that the structure of this organ should have been so long misunderstood ; that the young theca, under the name of germen, should have been supposed to be con- cealed in the bosom of the pistillum ; a supposition of which there is not the shadow of a proof. If we refer to the description in the first part of this paper, we shall find that the cavity of the pistillum is occupied, in the first instance, by a single cell ; and that this cell always remains at the base of the seta, where it may be found to the very last, tipping the conical extremity. We also find that before one particle of the theca can be formed, the seta must be developed; a process which, in many instances, occupies two or three " They soon became jointed, from the addition of fresh cells at the extremities. They then began to branch, and after a time produced leaves." ( Valentine in Linn. Trans, vol. xvii.) 110 SPORES ANALOGOUS TO POLLEN. [BOOK i. months after the destruction of the pistillum. It is scarcely necessary to ask, how it is possible that the sporules can be impregnated before the theca, in which they are developed, is in existence. If sexes are to be found in Mosses, they must be sought in the theca ; and accordingly we find that various botanists, probably impressed with this idea, have named in succession all the different parts of this organ as performing the function of the anthers. Some have fixed on the columella ; others on the peristome ; others on the oper- culum. It is altogether unnecessary to enter on an exami- nation of the truth of these various hypotheses, as their original proposers have adduced so little in their support, that no one at present considers them worth the slightest attention." (Linncean Transactions, vol. xvii.) Mr. Valentine not only thus disproves the possibility of the parts called Sexes in Urn-mosses being so ; but supports the opinion of Mohl that their sporules, and he adds those of all cellular plants, are analogous to the pollen of the Vas- culares, slightly modified by circumstances, but agreeing in every essential particular. " The analogy of the development of the sporules to that of pollen is very striking," he observes, " even to a superficial observer, and has not escaped the notice of botanists. A sec- tion of the anther of the common garden variety of Primula vulgaris, taken from a bud when about the size of a small pin's head, exhibits a structure which may be compared to a section of the theca of Polytrichum. In the former we find an axis of dense tissue (the connectivum) surrounded by the cuticle. This axis is not central, but placed nearer to the cuticle, on the back of the anther, and may be considered as the columella, whilst the cuticle will represent the theca. A separation of the tissue gradually takes place, in four dis- tinct points, nearly at equal distances from the axis. As the axis is not centrical, these points lie towards the front of the anther. Between each of these points the cuticle is fur- rowed longitudinally, so that the section has somewhat of a quadrangular figure. The theca of Polytrichum merely differs from this in having a complete separation of its tissue all round the axis, instead of in four points only. The spaces STRUCTURE.] SPORES ANALOGOUS TO POLLEN. Ill caused by the separation (not dissolution) of the tissue, gradually enlarging, form the cells of the anther, in which the viscid secretion takes place. This secretion is afterwards converted into pollen, in a manner similar to that in which the sporules are formed. When the anther is nearly ripe, a still further separation of the tissue takes place, and the four cells become two. When perfectly mature, these cells dehisce longitudinally at the lateral furrows. In Buxbaumia the theca frequently dehisces longitudinally after the manner of some anthers; whilst in Solanum the anther dehisces by a pore at the apex, thus approaching the ordinary dehiscence of the theca. The lining of the cells, or Endothecium of Purkinje, may be considered analogous to the columellar membrane." (Linn. Trans., vol. xvii.) Mrr Valentine afterwards supported these views by new observations, and at considerable length. I can only quote a part of the evidence on which he believes that the truth of his opinion is established. "The analogy," he observes, "which exists between sporules and pollen is so remarkable, and the particulars so numerous, that the essential identity of the two can, as I conceive, be scarcely a matter of opinion. In the first place, the sporules are formed in thecse, which have a great resemblance to some anthers. They are in most instances surrounded by a. peri- chsetium, which is a collection of modified leaves analogous to the perianth. They are either sessile, or seated on a stalk or seta, which may be named the filament. In Sphagnum the theca is elevated on a pedicel or leafless prolongation of the axis, of which peculiarity the anther of Euphorbia is a parallel instance. The thecse are one-celled, yet they have a columella, which may be likened to the connectivum ; and, although the connectivum usually divides the anther into two cells, Callitriche is an instance in which there is but one cell ; and there are examples in which the cavity is spuriously divided into four cells, as in Tetratheca, which, in this re- spect, resembles the theca of Polytrichum ; and in the fact of evacuating its contents by a single pore, resembles the general structure of thecae. All thecse are lined by a distinct membrane, and so nearly does this resemble the endothecium 112 SPOKES ANALOGOUS TO POLLEN. [BOOK i. of an anther, that in Jungermannia multifida its tissue is fibrous. The remarkable manner of the development of sporules and pollen is a most convincing analogy; they are secretions in the cellules which occupy the interior of the theca or anther, and are the only instances on record within my knowledge, of organised secretions in the cavities of simple cellules. Although the tetrahedral union of both sporules and pollen is almost always dissolved at an early period, yet, in some instances, as in QEdipodium and Erica Tetralix, it remains at maturity. Again, neither sporules nor pollen ever have the slightest apparent organic connexion with the parent plant, — a most remarkable coincidence. Then, to apply a chemical test, if sulphuric acid be applied to the sporules, the same phenomena occur as when it is applied to pollen. The effects of this test vary according to the nature of the contents of the sporule, and the manner of its application, which must be carefully regulated to insure a satisfactory result." The sporules of Jungermannia com- planata, one of the Scale-mosses, " in their natural state, are of a rich olive-brown colour, and are completely filled with minutely granular matter. On the addition of a small por- tion of acid a few of them immediately burst, and the con- tents are scattered, but the majority acquire a border of a deep red colour, the contents appearing to be collected more towards the centre of the cavity, and they become more irregular in shape, with a projection on one side. Upon the addition of a little more acid the outer coat is slowly ruptured, and the contents are gradually squeezed out, the passage appearing to be a work of great labour, giving an observer the idea of parturition in animals. When the contents are nearly out the action is more rapid, and they are ejected with force, the sporule recoiling and contracting the fissure with a spring, unless, as is sometimes the case, the sporule is so much lacerated as to lose its elasticity." Lastly, "the sporules of Mosses and of some other tribes commence their germination by the emission of the internal lining membrane in the form of a tube, which is exactly analogous to the pollen-tube. In the Mosses these tubes increase by the addition of a series of fresh tubes at their TRUCTURE.] MR. THWAITES'S VIEWS. 113 extremities, and at length a bud containing the rudiments of stem, leaves, and roots is formed, which may be considered analogous to the embryo or young bud, in the seed of more highly organised plants." (Linn, Trans, vol. xvii.) Mr. Thwaites, however, supports the sexuality of the an- therids and pistillids of Mosses on new grounds, and with so much skill that we should leave the subject very incomplete if we did not give his ingenious views nearly in his own words. After observing that he thinks it probable that the conjugation of Brittleworts will throw light upon the real nature of the so called antheridia and pistillidia (archegonia] of Mosses, he proceeds thus: — "The paper on this subject by Mr. Valentine would seem to settle the point that there can be no impregnation of the contents of the moss-capsule by the introduction into its cavity of any external substance, after the formation of the sporules. On the other hand, the learned authors of the Bryologia Europeea state with emphasis that certain species of Mosses, which are dioecious, —that is, some plants of the same species bearing anthe- ridia only, and others only archegonia, — 'do not bear fruit unless the male plants (those with antheridia) are in the neighbourhood of the plants possessing archegonia. It is perhaps not impossible to reconcile these, at first sight, apparently conflicting opinions. It may be that impregna- tion takes place before the production of the capsule ; that the cell from which the capsule, with its seta, &c., is de- veloped corresponds with the sporangium of the Diatoma- ceous plant, or the embryonic cell of the flowering plants ; that this cell contains a mixed endochrome derived partly from the antheridia; and that the entire capsule (with its contents, appendages, &c.), the further development of this primordial cell, corresponds to a perfect seed of the flowering plant, or to the aggregate of the sporangial frustules of a Diatomaceous plant. It is true that in some of the Mosses the structure of the capsule appears very complicated, but it is upon a very simple type, as shown in other species ; and, moreover, the sporangial frustules of the Diatomaceous plant possess cell-walls as highly developed as occur in any other phase of the species. In some of the Conjugate there is VOL. II. I 114 HORSETAILS. [BOOK i. also a division of the reproductive mass before it escapes from the plant, so that the numerous sporules of the Moss furnish no argument against the hypothesis just advanced. As a further argument in favour of the idea of the capsule of the Moss being the product of a mixed endochrome, it is stated by Bruch and Schimper that the capsule itself is not developed unless the two so-called sexes of the species are in proximity." (Annals of Natural History, i. 165, n. s.) For observations on the morphology of Urn Mosses the reader is referred to the Vegetable Kingdom, p. 65. In SPLIT MOSSES (Andraeacese) the sporangium is not an urn-like case, but splits into four valves, cohering by the operculum and base. In HORSETAILS (Equisetacea?) the stem is hollow, jointed, and bears a toothed sheath at each joint. The cylinder of the stem is pierced by longitudinal fistulae, which alternate with furrows on the outside of the stem ; there is also a bundle of ringed ducts connected with the fistula. The organs of reproduction are arranged in a cone, con- sisting of scales bearing on their lower surface an assemblage of cases, called sporangia, thecae, folliculi, or involucra, which dehisce longitudinally inwards. In these sporangia are con- tained two sorts of granules ; the one very minute and lying irregularly among a larger kind, wrapped in two filaments, fixed by their middle, rolled spirally, having either extremity thickened, and uncoiling with elasticity. By Hedwig the apex of the larger granules was supposed to be a stigma, and the thickened ends of the filament anthers, the small granules being the pollen. It is certain that the larger granules, round which the elastic filaments are coiled, are the reproductive particles. Mr. Griffith states that the club-shaped bodies which Hedwig referred to stamens are in reality analogous to elaters, and are developed in or on a loose membranous coat, and later than the central body, spore, or seed. This statement has been confirmed by Henderson and Mohl. SCALE MOSSES (Jungermanniacese) and LIVERWORTS (Mar- STRUCTURE.] SCALE MOSSES. 115 chantiaceae), differ much from each other in their organs of reproduction, while they have a striking resemblance in their vegetation. This latter, which bears the name of frond or thalluSj is either a leafy branched tuft, as in Urn Mosses, with the cellular tissue particularly large, and the leaves frequently furnished with lobes, and appendages at the base, called stipule or amphigastria ; or it is a flat lobed mass of green vegetable matter lying upon the ground. In Jungermannia, that part which is most obviously con- nected with the reproduction of the plant, and which bears an indisputable analogy to the theca of Mosses, is a valvular brown case, called the capsule or conceptacle (sporangium or sporocarpium), elevated upon a white cellular tender seta, and originating in a hollow sheath or perichsetium arising among the leaves. This conceptacle contains a number of loose spiral fibres (slaters) , inclosed in membranous cases, among which sporules lie intermixed : when fully ripe, the membranous case usually disappears, the spiral fibres, which are powerfully hygrometric, uncurl, and the sporules are dispersed. When young, the conceptacle is inclosed in a membranous bag (epigonium), which it ruptures when it elongates, but which it does not carry upwards upon its point, as Mosses carry their calyptra. This part, never- theless, bears the latter name. Besides the conceptacles of Jungermannia, there are two other parts which are thought to be also intended for the purpose of reproduction : of these, one consists of spherical bodies, scattered over the surface of some parts of the frond, and containing a granular substance ; the other is a hollow pouch, formed out of the two coats of a flat frond, and pro- ducing from its inside, which is the centre of the frond, numerous granulated round bodies which are discharged through the funnel-shaped apex of the pouch. There are also other bodies situated in the axillae of the perichaetial leaves, called anthers (spermatocystidia, antheridia, pollinaria, staminidia}, which " are externally composed of an extremely thin, pellucid, diaphanous membrane ; within they are filled with a fluid, and mixed with a very minute granu- lated substance, generally of an olivaceous or greyish colour : i 2 116 LIVERWORTS. [BOOK i. this, when the anther has arrived at a state of maturity, escapes through an irregularly shaped opening, which bursts at the extremity." Von Martius suspects these to be analo- gous to the sporangia of Azolla. In Monoclea and Targionia organs nearly analogous to those of Jungermannia are formed for reproduction. In Targionia the antheridia are represented by M. Montagne as being embedded in discs very like the shields of Lichens. (Ann. Sc., n. s. ix. 100.). In Marchantia the frond is a lobed flat green substance, not dividing into leaves and stems, but lying horizontally upon the ground, and emitting roots from its under surface. The organs of reproduction consist, firstly, of a stalked fungus- like receptacle, carrying on its apex a calyptra, and bearing sporangia on its under side ; secondly, of a stalked receptacle, plane on the upper surface, with oblong bodies embedded vertically in the disc, and called anthers ; thirdly, " of little open cups (cystulce), sessile on the upper surface of the fronds, and containing minute green bodies (gemma), which have the power of producing new plants." The first kind is usually considered a female flower, its spores being intermixed with elaters ; the second male, and the third viviparous apparatus. In the opinion of many modern botanists, the granules of both the first two are spores : about the function of the last there is no difference of opinion. Mirbel considers the first two to be male and female; but, whatever their functions may be, in structure there is but little analogy between them and the organs of more perfect plants. Meyen describes the so called spermatic animalcules, resembling the genus Vibrio, as occupying the interior of each grain of the supposed pollen in Marchantia polymorpha. (Comptes Rendus, vi. 533). They are figured by him in the Annales des Sciences, n. s. x. 319, t. 3, from Marchantia polymorpha, Chara vulgaris, Sphagnum acutifolium, and Hypnum triquetrum. Their real nature has been already explained. In Anthoceros, while the vegetation is the same as in Mar- chantia, the organs of reproduction are very different. They consist of a subulate column, issuing from a pericha3tium perpendicular to the frond, and dividing half way into two STRUCTURE.] LICHENS. 117 valves, which discover, upon opening, a subulate columella, to which sporules are attached without any elaters. There are also cystulae upon the frond, in which are inclosed pedi- cellate reticulated bodies, called anthers. Sphasrocarpus consists of a delicate roundish frond, on the surface of which are clustered several cystulse, each of which contains a transparent spherule filled with sporules. In Riccia the spherules are not surrounded by cystulae, but immersed in the substance of the frond. 4. THE LICHENAL ALLIANCE.* (Lichens.) These have a lobed frond or thallus (or blastema), the inner substance of which consists wholly of reproductive matter, that breaks through the upper surface in certain forms which have been called fructification. These forms are twofold; firstly, shields (scutella or apothecia), which are little coloured cups or lines with a hard disc, surrounded by a rim, and containing asci, or tubes filled with sporules ; and, secondly, soredicij which are heaps of pulverulent bodies scattered over the surface of the thallus. The nomenclature of the parts of Lichens has been excessively extended beyond all necessity : it is, however, desirable that it should be understood by those who wish to read the systematic writers upon the subject. 1. Apothecia, are shields of any kind. 2. Perithecium, is the part in which the asci are contained. 3. Hypothecium ; the substance that surrounds, or overlies the perithecium, as in Cladonia. 4. Scutellum, is a shield with an elevated rim, formed by the thallus. Orbilla, is the scutellum of Usnea. 5. Pelt a, is a flat shield without any elevated rim, as in the genus Peltidea. 6. Tuber culum, or Cephalodium, is a convex shield without an elevated rim. 7. Trica, or Gyroma, is a shield, the surface of which is grooved with sinuous concentric furrows. * Vegetable Kingdom, p. 45. 118 LICHENS. [BOOK i. 8. Lirella, is a linear shield, such as is found in Opegrapha, with a channel along its middle. 9. Patellula ; an orbicular sessile shield, surrounded by a rim which is part of itself, and not a production of the thal- lus, as in Lecidea. D. C. 10. Globulus ; a round deciduous shield, formed of the thallus, and leaving a hollow when it falls off, as in Isidium. D. C. 11. Pilidium ; an orbicular hemispherical shield, the outside of which changes to powder, as in Calycium. D. C. 12. Podetia; the stalk-like elongations of the thallus, which support the fructification in Cenomyce. 13. Scypha (oplarium, Neck.), is a cup-like dilation of the podetium, bearing shields on its margin. 14. Soredia (globuli, glomeruli], are heaps of powdery bodies lying upon any part of the surface of the thallus. The bodies of which the soredia are composed are called conidia by Link, and propagula by others. 15. Cystula, or Cistella ; a round closed apothecium, filled with sporules, adhering to filaments which are arranged like rays around a common centre, as in Spha3rophoron. 16. Pulvinuli, are spongy excrescence-like bodies, sometimes rising from the thallus, and often resembling minute trees, as in Parmelia glomulifera. Greville. 17. Cyphella, are pale tubercle-like spots on the under surface of the thallus, as in Sticta. Grev. 18. Lacuna, are small hollows or pits on the upper surface of the thallus. Grev. 19. Nucleus proligerus, is a distinct cartilaginous body coming out entire from the apothecia, and containing the repro- ductive organs. Grev. 20. Lamina prohgera, is a distinct body containing the repro- ductive organs, separating from the apothecia, often very convex and variable in form, and mostly dissolving into a gelatinous mass. Grev. 21. Fibrillce, are the roots. 22. Excipulus, is that part of the thallus which forms a rim and base to the shields. 23. Nucleus, is the disc of the shield which contains the sporidia and their cases. STRUCTURE ] PU.NGALS. 119 24. Asci, are tubes, in which the sporidia are contained while in the nucleus. 25. Thallodes, is an adjective used to express an origin from the thallus : thus, margo thallodes signifies a rim formed by the thallus, excipulus thallodes a cup formed by the thallus. 26. Lorulum, is used by Acharius to express a filamentous branched thallus. 27. Crusta, is a brittle crustaceous thallus. 28. Gongyli, or Gonidia, are granules, universally of a green colour ; they lie either singly or in clusters beneath the cortical layer of the thallus, or break out in clusters called soredia, or in cups called cyphelia. 5. THE FUNGAL ALLIANCE. * (Fungi.) These plants consist of little besides cellular tissue, among which spores, or sporidiferous asci are generated. Some, of the lowest degree of development, are composed only of a few cellules, as Mucor, of which one is larger than the rest, and contains the spores; others are more highly compounded, consisting of myriads of cellules, with sporidia lying in cases, or asci. Sexes have been generally denied to Fungals. M. Leveille has shown that, in the Agaric and some other high forms of the order, there are two sorts of organs ; the one prominent cells containing a highly attenuated form of matter, and the other undoubtedly spores, and that these two kinds of organs are intermingled with each other ; and these bodies have been supposed to represent a sexual apparatus. There does not, however, exist the slightest proof of their nature : and they appear to be wholly absent in all the low Fungals. Corda has shown that spiral-threaded cells, analogous to elaters, exist in the genus Trichia. This, however, had been observed before by the younger Hedwig and Kunze. It is exclusively among these plants that we meet with * See « Vegetable Kingdom," p. 29. 120 FUNGALS. [BOOK i. cases of parasitism upon living animal bodies. The silkworm, and hymenopterous insects, are destroyed by the action of certain species of Botrytis in the one case, and Sphseria in the other, which attack them while alive. Notwithstanding the extreme simplicity of these plants, writers upon Fungi have contrived to multiply the terms relating to them in a remarkable manner. The following are those which are most usually employed. 1. The Pileus, or Cap, is the uppermost part of the plant of an Agaricus, and resembles an umbrella in form. 2. The Stipes, is the stalk that supports the pileus. 3. The Volva, or Wrapper, is the involucrum-like base of the stipes of Agaricus. It originally was a bag enveloping the whole plant, and was left at the foot of the stipes when the plant elongated and burst through it. 4. The Velum, or Veil, is a horizontal membrane, connecting the margin of the pileus with the stipes : when it is adnate with the surface of the pileus, it is a velum uni- versale ; when it extends only from the margin of the pileus to the stipes, it is a velum partiale. 5. The Annulus, is that part of the veil which remains next the stipes, which it surrounds like a loose collar. 6. Cortina, is a name given to a portion of the velum which adheres to the margin of the pileus in fragments. 7. The Hymenium, is the part in which the reproductive organs immediately lie; in Agaricus, it consists of parallel plates, called lamella, or gills. These are adnate with the stipes, when the end next it coheres with it : when they are adnate, and at the same time do not ter- minate abruptly at the stipes, but are carried down it more or less, they are decurrent ; if they do not adhere to the stipes, they are said to be/ree. 8. Stroma, is a fleshy body to which flocci are attached ; as in Isaria and Cephalotrichum. 9. Flocci, are woolly filaments found mixed with sporules in the inside of many Gastromyci. The same name is also applied to the external filaments of Byssaceae. 10. Orbiculus, is a round flat hymenium contained within the peridium of some fungi ; as Nidularia. W. STRUCTURE.] FUNGALS. 121 11. Nucleus, is the central part of a perithecium. 12. Sporangium, is the external case of Lycoperdon and its allies ; it is, however, best employed to designate the false peridium of Mucorini. 13. Sporangiolum, its diminutive. 14. Peridium, Peridiolum, terms usually substituted for Spo- rangium and Sporangiolum. 15. Perithecium, is a term used to express the part which contains the reproductive organs of Sphseria and its co-ordinates. 16. Ostiolum, is the orifice of the perithecium of Spha3ria. 17. Spherula, is a globose peridium, with a central opening through which sporidia are emitted, mixed with a gela- tinous pulp. 18. Capillitium, is a kind of purse or net, in which the spores of some Fungi are retained ; as in Trichia. W. 19. Trichidium, or Pecten, is a tender, simple, or sometimes branched hair, which supports the spores of some Fungi; as Geastrum. W. 20. Asci, are the tubes in which the sporidia are placed; ascelli or theca are the same thing. 21. Paraphyses, barren asci, or at least threads accompanying the asci. 22. Spores ; the reproductive organs when produced at the tip of a cell, without any external case or ascus. 23. Sporidia ; spores contained in asci. Sporidiola ; the nuclei of spores or sporidia. 24. Episporium; the membrane, usually double, which in vests the Endochrome of the reproductive organs. 25. Endochrome; the granular contents of spores and spo- ridia. 26. Nuclei; bodies contained in the reproductive organs analogous to cytoblasts, and then called sporidiola, or mere oil globules. 27. Sporules ; a term used variously by authors, but which is best confined to designate the component granules of the Endochrome. 28. Thallus, or TTialamus, is the bed of fibres from which many Fungi arise. 122 ALGALS. [BOOK i. 29. Mycelia, are the rudiments of Fungi, or the matter from which Fungi are produced. 80. Cystidia, are the projecting cells, or supposed male organs, of Agarics, &c. 31. Sporophores or Basidia, are the cells on the apex of which the spores of such plants are formed. 6. THE ALGAL ALLIANCE.* (Confervas, Seaweeds, fyc.) These, with Fungi, constitute the lowest order of vege- table development : they vary from mere microscopic ob- jects to a large size, and are composed of cellular tissue in various degrees of combination; some are even apparently animated, and thus form a link between the two great king- doms of organised matter. Their spores are either scattered through the general mass of each plant, or collected in certain places which are more swollen than the rest of the stem, and sometimes resemble the pericarps of perfect plants. The mode of propagation in Algals is extremely variable, but apparently always takes place by the formation of spores, either within the ordinary cells of the plant, or within spo- rangia of one kind or other. The Zygnemata have the curious attribute of forming their spores by the copulation of two contiguous branches. The terms used in speaking of the parts of these plants are the following : — 1 . Gongylus ; a round hard body, which falls off from the mother plant, and produces a new individual : this is found in Fuci. W. 2. Thallus ; the plant itself. 3. Apothecia ; the cases in which the organs of reproduction are contained. 4. Peridiolum, Fr.; the membrane by which the spores are immediately covered. 5. Granula; large spores, contained in the centre of many Algacese; as in Gloionema of Greville. Crypt. Fl. vi. 30. * See « Vegetable Kingdom," p. 8. STRUCTURE.] ALGALS. 123 6. Pseudoperithecium ;} terms used by Fries to express sucli 7. Pseudohymenium ; > coverings of spores as resemble 8. Pseudoperidium ; } in figure the parts named peri- thecium, hymenium, and peridium in other plants : see those terms. 9. Sporidia ; granules which resemble spores, but which are of a doubtful nature. It is in this sense that Fries declares that he uses the word : vide Plant, homonom. p. 294. They are also called Sports. 10. Phycomater, Fries; the gelatine in which the spores of Byssacese first vegetate. 11. Vesicula ; inflations of the thallus, filled with air, by means of which the plants are enabled to float. 12. Hypha, Willd. ; the filamentous, fleshy, watery thallus of Byssacese. 13. Sporangia; any kind of case not obviously a joint of the plant, within which spores are generated. 14. Coniocysta ; tubercle-like closed apothecia, containing a mass of spores ; the same as sporangium. Dr. Harvey thus describes their reproductive organs, (British Alg Paris, 1829. The calyx seems, when green, to perform the functions of leaves, and to serve as a protection to the petals and sexual organs ; when coloured, its office is undoubtedly the same as that of the corolla. The common notion of the use of the corolla is, that, inde- pendently of its ornamental appearance, it is a protection to the organs of fertilisation ; but, if it is considered that the stamens and pistils have often acquired consistence enough to be able to dispense with protection before the petals are enough developed to defend them, it will become more probable that the protecting property of the petals, if any, is of secondary importance only. Among the many speculations to which these beautiful ornaments have given birth is one, that the petals and disc are the agents of a secretion which is destined to the nutrition of the anthers and young ovules. These parts are formed in the flower-bud long before they are finally called into action ; in the Almond, for example, they are visible some time before the spring, beneath whose influence they are destined to FUNCTION.] SOURCE OF NECTAR. 509 expand. In that plant, jnst before the opening of the flower, the petals are folded up ; the glandular disc that lines the tube of the calyx is dry and scentless ; and its colour is at that time dull, like the petals at the same period. But, as soon as the atmospheric air comes in direct contact with these parts, the petals expand and turn out of the calyx, the disc enlarges, and the aspect of both organs is altered. Their compact tissue gradually acquires its full colour and velvety surface ; and the surface of the disc, which before was dry, becomes lubricated by a thick liquid, exhaling that smell of honey which is so well known. At this time the stamens perform their office. No sooner is that effected than they wither, the petals shrivel and fall away, the secretion from the disc gradually dries up, and, in the end, the disc perishes along with the other organs to which it appertained. If the disc of an Almond flower be broken before expansion, it will be seen that the fractured surface has the same appearance as those parts which in certain plants contain a large quantity of fsecula, as the tubers of the Potato, Cyperus esculentus, &c. This led Dunal to suspect that the young discs also contained faecula : which he afterwards ascertained, by experiment, to be the fact in the spadix of Arum italicum before the dehis- cence of the anthers ; but, subequently to their bursting, no trace of fsecula could be discovered. Hence he inferred that the action of the air upon the humid faecula of the disc had the effect of converting it into a saccharine matter fit for the nutrition of the pollen and young ovules ; just as the fsecula of the albumen is converted in germination into nutritive matter for the support of the embryo. In support of this hypothesis, Dunal remarks that the con- ditions requisite for germination are analogous to those which cause the expansion of a flower. The latter opens only in a temperature above 32° Fahr., that of 10° to 30° centig. (50° to 86° Fahr.) being the most favourable; it requires a considerable supply of ascending sap, without the watery parts of which it cannot open ; and, thirdly, flowers, even in aquatic plants, will not develope in media deprived of oxygen. Thus the conditions required for germination and for VOL. n. p 210 ACTION OF DISC. [BOOK n. flowering are the same ; the phenomena are in both cases also very similar. When a germinating seed has acquired the necessary degree of heat and moisture, it abstracts from the air a portion of its oxygen, and gives out an equal quantity of carbonic acid gas ; but as one volume of the latter gas equals one volume of oxygen, it is evident that the seed is, in this way, deprived of a part of its carbon. Some changes take place in the albumen and cotyledons ; and, finally, the fsecula that they contained is replaced by saccharine matter. In like manner, a flower, while expanding, robs the air of oxygen, and gives out an equal volume of carbonic acid ; and a sugary matter is also formed, apparently at the expense of the faecula of the disc or petals. The quantity of oxygen converted into carbonic acid in germination is, cateris paribus, in proportion to the weight of the seed ; but some seeds absorb more than others. Theodore de Saussure has shown that exactly the same phenomenon occurs in flowers. Heat is a consequence of germination ; the temperature is also augmented during flowering, as has been proved by Theodore de Saussure in the Arum, the Gourd, the Bignonia radicans, Polyanthes tuberosa, and others. The greater part of the saccharine matter produced during germination is absorbed by the radicle, and transmitted to the first bud of the young plant. Dunal is of opinion that the sugar of the nectary and petals is, in like manner, con- veyed to the anthers and young ovules; and that the free liquid honey, which exists in such abundance in many flowers, is a secretion of superabundant fluid ; it can be taken away, as is well known, without injury to the flower. This opinion will probably be considered the better founded, if it can be shown that the disengagement of caloric and destruction of oxygen are in direct relation to the development of the glandular disc, and also are most consider- able at the time when the functions of the anthers are most actively performed. In no plants, perhaps, is the glandular disc more developed than in Arums ; and it is here that the most remarkable DISENGAGEMENT OF HEAT. 211 degree of development of caloric has been observed. Senebier found that the bulb of a thermometer, applied to the surface of the spadix of Arum maculatum, indicated a temperature 7° higher than that of the external air. Hubert remarked this, in a still more striking degree, upon Arum cordifolium, at the Isle of France. A thermometer placed in the centre of five spadixes stood at 111°, and in the centre of twelve at 121°, although the temperature of the external air was only 66°. The greatest degree of heat in these experiments was at sun- rise. The same observer found that the male parts of six spadixes, deprived of their glandular part, raised the tempe- rature only to 105°; and the same number of female spadixes only to 86° ; and, finally, that the heat was wholly destroyed by preventing the spadix from coming in contact with the air. Similar observations were made by others, with corre- sponding results; but, nevertheless, as many persons at- tempted in vain to witness the phenomenon, it began to be doubted, especially after Treviranus added his authority to that of those who doubted the existence of any disengagement of heat. The truth of the statement of Saussure and others has lately, however, been placed beyond all further doubt, by the experiments of Adolphe Brongniart upon Colocasia odora. (Nouv. Ann. du Museum, vol. iii.) From the period of the expansion of the spathe, he applied to the middle of the spadix a very delicate and small thermometer, which he fixed to its place by a piece of flannel rolled several times round it and the spadix, so that the bulb of the thermometer touched the spadix on one side ; and on all others was pro- tected by the flannel from contact with the air. All this little apparatus covered so small a portion of the spadix, that it was left in its place without interfering with the functions of that part. On the 13th of March, the spathe not being open, the flower diffused, notwithstanding, a fragrant smell. On the 14th it was open, and the odour was much increased. The emission of pollen took place on the 16th, between 8 and 10 A.M., and continued till the 18th. On the 19th the flower began to fade. From the 14th to the 19th the temperature increased daily, during the night and in the p 2 212 • DISENGAGEMENT OF HEAT. [BOOK n. morning falling back to nearly that of the surrounding air. The maximum of elevation of temperature above that of the atmosphere occurred — On the 14th, at 3 P.M. 4'5° centigrade 15th, 4 P.M. 10° 16th, 5 P.M. 10-2° 17th, 5 P.M. 11° 18th, 11 A.M. 8-2° 19th, 10 A.M. 2-5° These maxima might be almost compared to the access of an intermittent fever. Vrolik and Vriese consider the so called Arum cordifolium of the Isle of France to be the same as the aforesaid Colocasia odora, upon whose temperature they made very numerous hourly observations in the Botanical Garden of Amsterdam, the result of which was, that the maximum of difference observed between the temperature of the spadix and that of the green-house amounted to 10° centig. (Ann. des Sc. vol. v. 145.) Goppert adds that plants are generally warmer than the air which surrounds them. ( Ueber warme Entwicke- lung in der lebenden Pflanze. Wien, 1832.) That these phenomena should not be observed in ordinary cases, is no proof that they do not also occur ; f6r it is easy to comprehend that, when flowers are freely exposed to the external air, the small amount of caloric which any one may give off will be instantly dispersed in the surrounding air, before the most delicate instrument can be sensible of it ; and that it is in those instances only of large quantities of flowers collected within a hollow case, like a spathe, which prevents the heat escaping when evolved, that we can hope to measure it. From experiments of Saussure, it seems certain that the disengagement of heat, and, consequently, destruction of oxygen, is chiefly caused by the action of the anthers, or at least of the organs of fecundation, as appears from the fol- lowing table : — FUNCTION.] DESTKUCTION OF OXYGEN. 213 Oxygen destroyed. Names. of the Experiment. By the bud. By the flower dur- ing its expansion. By the flower in withering. Passiflora serratifolia . 1 2 hours. 6 times its vol. 12 7 Hibiscus speciosus . . 24 „ G 8-7 7 Cucurbita maxima, male flower 24 7-4 12 10 Arum italicum, spadix cold . . . 24 „ 5 to 6 „ spadix hot 30 24 hours after 5 It was also found that flowers in which the stamens, disc, pistil, and receptacle, only were left, consumed more oxygen than those that had floral envelopes, as is shown by the following table : — Duration Oxygen destroyed. Experiment. By the flowers entire. By the usual organs only. Cheiranthus incanus . 24 hours. 11 -5 times their vol. 18 times their vol. Tropseolum majus Cucurbita maxima, male 24 „ 10 „ 8-5 „ 16-3 „ • Hy peri cum calycinum 24 „ 7'5 8-5 Hibiscus speciosus . 12 „ 5*4 tt 6-3 Cobsea scandens . . 24 „ 6-5 7*5 „ And it is here to be noticed, that those whose sexual appa- ratus destroyed the most oxygen have the greatest quantity of disc, and vice versd ; with the exception of Cobsea scandens, in which the disc is very firm and persistent, and probably, therefore, acts very slowly. When the cup-shaped disc of the male flowers of the Gourd was separated from the anthers, the latter only con- sumed 11*7 times their volume of oxygen, in the same space of time which was sufficient for the destruction of sixteen times their volume when the disc remained. The spathe of Arum maculatum consumed, in twenty-four hours, five times its volume of oxygen ; the termination of the spadix thirty times ; the sexual apparatus 152 times, in the same space of time. 4 EXTRICATION OF HEAT. [BOOK n, An entire Arum Dracunculus, in twenty-four hours, de- stroyed thirteen times its volume of oxygen; without its spathe fifty-seven times; cut into four pieces, its spathe destroyed half its volume of oxygen ; the terminal appendix twenty-six times; the male organs 135 times; the female organs ten times. The same ingenious observer also ascertained that double flowers, that is to say, those whose petals replace sexual organs, vitiate the air much less than single flowers, in which the sexual organs are perfect, Is it not then, concludes Dunal, probable, that the conse- quence of all these phenomena is the elaboration of a matter destined to the nutriment of the sexual organs? since the production of heat and the destruction of oxygen are in direct relation to the abundance of glandular surface, and since these phenomena arrive at their maximum of intensity at the exact period when the anthers are most developed, and the sexual organs in the greatest state of activity. "To the above facts," says Dumas, " several valuable remarks have been added by the Dutch savants, which serve to complete the study of this curious phenomenon. They found that the temperature of the flower rose as high in oxygen gas as in air, whilst in nitrogen nothing similar could be observed. They have also shown that in proportion as the temperature rises, in the same proportion is carbonic acid formed. In a word, they found all the characters of com- bustion, in this phenomenon, and they did not hesitate so to state it. It may be affirmed, then, that in Colocasia odor a, there is, every day during fecundation, a considerable rise of temperature, owing to the combustion of carbon, by which a large quantity of carbonic acid is formed, and an intense odour produced, which seems connected with this phenomenon of combustion." These observations have been confirmed by Dutrochet by thermo-electrical experiments, of which the following account is given by Meyen : — He says, plants possess a peculiar warmth ; but it is completely absorbed by the evaporation of the sap, by the evolution of oxygen by day, and of car- bonic acid by night. It rather seems that, in the natural FUNCTION.] PROPER HEAT OP PLANTS. 215 state, plants possess the property of producing cold, for they almost always have a lower temperature than that of the surrounding air. If, however, evaporation is prevented, it is easy to observe the proper temperature of plants ; Dutrochet used a thermo-electrical apparatus, and for comparison the experiments were made both with* living and dead plants ; dead plants acquired the temperature of the surrounding medium ; live plants the same, with the addition of that which was lost by evaporation, and which M. Dutrochet reckons at the most to be 4° Cels ; often only -£°, or even -^ or -fa°. The proper heat of young twigs and leaves vanishes in the night, or in general in the dark, and appears again under the influence of light. The higher the external temperature, the greater is the vegetable warmth. That part of the heat of plants which is carried off by the evolution of oxygen cannot be determined quantitatively. Proofs that plants possess a peculiar heat, dependent upon their vital forces, was long since published in Germany; and in my "Physiology," says Meyen, I proved that an extrication of heat occurs not only in germinating seeds, and in the fresh fruits of Areca Catechu when lying together, but also in leaves and herbage in general ; " singly they do not exhibit any warmth on account of the evaporation, but they do when brought together in masses. I convinced myself of the truth of this by the thermometer. I have several times experimented with fresh-cut grass and fresh spinach leaves. Dutrochet has added that new researches confirm the former ones. In the stem of Euphorbia Lathyris he remarked the vegetable heat amount to ±° C., but only so long as it was in a verdant state. He also found heat in roots, fruits, and even embryos. Complete exclusion of light totally prevents the rise and fall of temperature, but this does not always take place the first day. M. Dutrochet remarked the change of temperature by night and by day even on the second day of the experiment." " MM. Bergsma and Van Beck have clearly proved that perspiration is the cause of the difficulty in measuring the temperature proper to plants. They chose (in January, 1839) a hyacinth growing in a glass for their experiments. 216 PROPER HEAT OF PLANTS. [BOOK n. The glass was put into another vessel, containing water of a higher temperature, in order in this manner to increase the activity of the roots. The needles of the thermo-electrical apparatus were then inserted into the external parts of the flower-stalks, and instead of an increase of temperature, they observed a fall; the apparatus indicated 17*5° C., while that of the water was 28' 5°. The experiment was repeated several times with like success, as also with the flower-stalk of Entelea arborescens. This was owing to the powerful perspiration caused by increased activity promoted by warm water. When the needles were inserted into the middle of the flower-stalk of the hyacinth, the temperature of the interior was found to be 1° higher than that of the surrounding air. At a later period M. Dutrochet published some further observations, and stated generally that plants possess a peculiar heat, which is principally located in the green parts. This heat exhibits a daily periodicity ; it reaches its maximum towards mid-day, and its minimum during the night. The hour at which plants reach their maximum temperature is the same for each species, but different in different species ; thus, Rosa canina at 10 a.m.; Allium Porrum at 11 a.m.; Borago officinalis at mid-day ; Euphorbia Lathyris at 1 p.m. ; Sambucus nigra at 2 p.m. ; and Asparagus and Lactuca sativa at 3 p.m. The greatest heat is in the neighbourhood of the principal bud, and in woody plants often only in the green extremities. Other experiments confirm the fact, that plants growing in the dark lose their vegetable heat ; but experiments on different fungi showed that these also possess a daily periodicity. Boletus seneus exhibited a heat FUNCTION.] FERTILISATION. 217 CHAPTER IX. FERTILISATION. HYBRID PLANTS. THE office of the stamens is to produce the matter called pollen, which has the power of fertilising the pistil through its stigma. The stamens are, therefore, the representatives, in plants, of the male sex, the pistil of the female sex. The old philosophers, in tracing analogies between plants and animals, were led to attribute sexes to the former, chiefly in consequence of the practice among their countrymen of artificially fertilising the female flowers of the date with those which they considered male, and also from the existence of a similar custom with regard to figs. This opinion, however, was not accompanied by any distinct idea of the respective functions of particular organs, as is evident from their con- founding causes so essentially different as fertilisation and caprificatiou ; nor was it general, although Pliny, when he said that " all trees and herbs are furnished with both sexes," may seem to contradict this statement ; at least, he indicated no particular organs in which the sexes resided. Nor does it appear that more distinct evidence existed of the universal sexuality of vegetables till about the year 1676, when it was for the first time clearly pointed out by Sir Thomas Millington and Grew. Claims are, indeed, laid to a priority of discovery over the latter observer by Csesalpinus, Malpighi, and others ; but I see nothing so precise in their works as we find in the declaration of Grew, " that the attire (meaning stamens) do serve as the male for the generation of the seed." It would not be consistent with the plan of this work, to enter into any detailed account of the gradual advances which such opinions made in the world, nor to trace the progress of dis- covery of the precise nature of the several parts of the stamens and pistil. Suffice it to say, that, in the hands of Linnaeus, 218 EMISSION OF POLLEN. [BOOK n. the doctrine of the sexuality of plants seemed finally estab- lished, never again to be seriously controverted ; for it must be admitted, that the denial of this fact, which has been since occasionally made by such men as Alston, Smellie, and Schelver, has carried no conviction with it. It is a general law that the powder which is contained in the case of the anthers, and which is called pollen, must come in contact with the viscid surface of the stigma, or no fecundation can take place. It is possible, indeed, without this happening, that the fruit may increase in size, and that the seminal integuments may even be greatly developed ; the elements of all these parts existing before the action of the pollen can take effect : but, under such circumstances, whatever may be the development of either the pericarp or the seeds, no embryo can be formed. This universality of sexes does not, however, extend to cryptogamic plants, as has been already shown. In order to insure the certain emission of the pollen at the precise period when it is required, a beautiful contrivance is provided. Purkinje has demonstrated the correctness of MirbePs opinion in 1808, that the cause of the dehiscence of the anther is its lining, consisting of cellular tissue, cut into slits, and eminently hygrometrical. He shows that this lining is composed of cellular tissue, chiefly of the fibrous kind, which forms an infinite multitude of little springs, that when dry, contract and pull back the valves of the anthers, by a powerful accumulation of forces, individually scarcely appreciable ; so that the opening of the anther is not a mere act of chance, but the admirably contrived result of the maturity of the pollen; an epoch at which the surround- ing tissue is necessarily exhausted of its fluid, by the force of endosmose exercised by each particular grain of pollen. That this exhaustion of the circumambient tissue by the endosmose of the pollen is not a mere hypothesis, has been shown by Mirbel in a continuation of the memoir I have already so often referred to. He finds that, on the one hand, a great abundance of fluid is directed into the cells in which FUNCTION.] COLLECTORS IN BELLWORTS. the pollen is developed, a little before the maturity of the latter, while, by a dislocation of those cells, the pollen loses all organic connexion with the lining of the anther; and that, on the other hand, these cells are dried up, lacerated, and disorganised, at the time when the pollen has acquired its full development. In some plants, especially in Bellworts (Campanulacea3), a provision is found for brushing the pollen out of the anthers and conveying it to the stigma ; concerning which we have the following observations by M. Adolphe Brongniart : — " It has long been known that the external surface of the upper part of the style, and of the stigmatic arms of Cam- panulaceous plants, is covered with long hairs, which are very visible in the bud, before the dispersion of the pollen, and which are regularly arranged in longitudinal lines in direct relation to the number and position of the anthers. " These hairs and their connexion with the pollen, at first remarked by Conrad Sprengel in several species of Campa- nula, and afterwards by Cassini, with more care, in Cam- panula rotundifolia, have been observed by M. Alphonse De Candolle in the whole Campanulaceous order, with the excep- tion of the small genus Petromarula. At the period of dehis- cence of the anthers, before the expansion of the corolla, and when the arms of the style are still pressed against each other in the form of a cylinder, these hairs cover themselves with a considerable quantity of pollen, which they brush, so to speak, out of the cells of the anther ; and for this reason they have been named, like the analogous hairs in Composite, Col- lectors. " At the period when the flower expands, the arms of the style, or stigmata separate, and curve backwards, and the anthers that surround them retire and shrivel up, after having lost all their pollen ; but at the same time the pollen, which was deposited on the outside of the style, detaches itself, and the hairs that covered the surface disappear. " This led Cassini to call these hairs deciduous, and to say that they disappear at the same time with the pollen which they retained. There then remains, he says, upon the style, nothing more than little asperities," 220 COLLECTING HAIRS [BOOK 11. M. Alphonse De Candolle is yet more explicit. He ex- presses himself thus : — " the arms of the style begin to diverge. At the same time the pollen disappears, the collecting hairs drop off, and the style becomes altogether smooth." Never- theless, a microscopical examination of these hairs has satisfied me that they do not fall off, but that they offer a phenomenon of which I know no other example in the vegetable kingdom. They are retractile, like the hairs of certain Annelids, or the tentacula of snails. If we examine a thin longitudinal slice of a young style, before the emission of the pollen, it is seen that these cylin- drical hairs, a little tapering to their fine extremity, are formed by an external lengthening of the epidermis, and that they are perfectly simple, without articulation or partitions even at their base. Immediately below the base of each hair, there exists in the subjacent cellular tissue a cavity about equal in depth to half or a third the length of the hair, continuous with its cavity, and apparently filled with the same fluid. This cavity, however, does not extend beyond the most superficial stratum of the style or stigma, and has no relation to the tissues situated deeper, of which mention will be made presently. This arrangement is preserved up to the time of the expan- sion of the flower, the hairs being at that time covered by grains of pollen, applied over their surface, and held between their interstices. But at this period the hairs retract into the cavities formed at their base among the cellular tissue ; the terminal half ensheaths itself in the half situated next the base, as it by degrees returns into the cavity. The point only of the hair remains projecting beyond the surface of the style, and causes the asperities noticed by Cassini. Sometimes the hair, in retracting thus within itself, draws with it a few grains of pollen, which thus appear to penetrate the tissue of the style, but which, in fact, are always on the outside of the hair. With care these hairs may be pulled out again by the point of a needle, and then the pollen-grains which appear to have penetrated the style are immediately expelled. Such pollen- grains undergo no change during their application to the FI-M-TION.] IN CAMPANULACE.E. 221 collecting hairs, nor even when they are drawn inwards by the latter during their act of retraction. There is, therefore, no communication between them and the interior of the style. As to the immediate cause of this retraction of the hairs, without pretending to give a certain explanation of it, I think it may be ascribed to the absorption of the liquid contained both in the hair and in the cavity at its base, an absorption, the effect of which will be to pull back the hair into the cavity, at least I see no other part whose action can produce the phenomenon. An examination of the structure of the external stratum of the style and stigmatic arms, has already tended to show the baseless character of the opinion held by those physiolo- gists who think that fertilisation can take place by the action of the pollen upon this part ; an opinion offered with doubt by Cassini and Alphons.e De Candolle, asserted, on the con- trary, in the most positive manner, by Treviranus, who, in his Physiology, vol. ii. p. 343, considers the internal stigmatic surface to be formed of papillae analogous to those which sometimes terminate the petals, while, according to him, the hairs covering the external surface of the style and stigma, perform the part of the stigmata. Link (Philosophia Botanica, 2nd edition, vol. ii. p. 222), also admits that fertilisation takes place by these hairs, whose points, he says, are destroyed while the base remains, and so present a large opening which leads into the style. We therefore see that the most distinguished botanists entertain opinions either doubtful or contrary to the most probable analogies. Nevertheless, in dissecting the true stigma of Campanulas, that is to say, the inner face of the stigmatic arms, after their divergence, we find that the grains of pollen, scattered over the surface adhere to it, as to all true stigmas, first by aid of the fluid that lubricates them, and finally, by the production of pollen-tubes which penetrate it, and soon mark a cord of long soft vesicular tissue, which occupies the centre of the style. This cord of conducting tissue, of hexagonal form, in the true Campanulas, whose stigma has three arms, is perfectly 222 ACTION OF POLLEN". [BOOK n. distinct from the surrounding tissue, much more dense, and coloured ; it is easily separated, and is entirely composed of vesicles of a cylindrical or somewhat fusiform figure, very long, colourless, quite separate at the sides, articulated to each other, end to end, and containing very small regular globules of starch, becoming blue upon the application of iodine. The pollen-tubes which penetrate between the utricles of this tissue are easily distinguished by being much finer, unarticulated, and filled with very fine indistinct gra- nules." (Annales des Sciences.} Morren has made some statistical observations upon the sexual organs of Cereus grandiflorus. He found that in each flower of this plant there are about 500 anthers, 24 stigmata, and 30,000 ovules. He estimates each anther to contain 500 grains of pollen; the whole number in each flower being 250,000 ; so that not more than an eighth of the whole number of pollen grains can be supposed to be effective. The distance from the stigma to the ovules he computes at 1150 times the diameter of the pollen grain. The exact mode in which the pollen took effect was for a long time an inscrutable mystery. It was generally supposed that, by some subtle process, a material vivifying substance was conducted into the ovules through the style ; but nothing certain was known upon the subject until the observations of Amici and of Adolphe Brongniart had been published. It is now ascertained, that, a short time after the application of the pollen to the stigma, each grain of the former emits one or more tubes of extreme tenuity, not exceeding the 1500th or 2000th of an inch in diameter, which pierce the con- ducting tissue of the stigma, and find their way down to the region of the placenta, including within them the molecular matter found in the pollen grain. These pollen-tubes actually reach the ovules. Brown states he has traced them into the apertures of those of Orchis Morio, and Peristylus (Habenaria) viridis, although this great observer adds that the tubes in those plants probably do not proceed from the pollen. Be this as it may, it seems certain that it is necessary for FUNCTION.] POLLEN-TUBES AND FORAMEN. 223 the pollen to be put in communication with the foramen of the ovule, through the intervention of the conducting tissue of the style. In ordinary cases this is easily effected, in consequence of the foramen being actually in contact with the placenta. Where it is otherwise, nature has provided some curious contrivances for bringing about the necessary contact. In Euphorbia Lathyris the apex of the nucleus is protruded far beyond the foramen, so as to lie within a kind of hood-like expansion of the placenta : in all campylotropal ovules the foramen is bent downwards, by the unequal growth of the two sides, so as to come in contact with the conducting tissue j and in Statice Armeria, Daphne Laureola, and some other plants, the surface of the conducting tissue actually elongates and stops up the mouth of the ovule, while fertilisa- tion is taking effect. A different arrangement occurs in Helianthemum. In plants of that genus the foramen is at the end of the ovule most remote from the hilum ; and although the ovules themselves are elevated upon cords much longer than are usually met with, yet there is no obvious means provided for their coming in contact with any part through which the matter projected into the pollen-tubes can be supposed to descend. It has, however, been ascertained by Adolphe Brongniart, that, at the time when the stigma is covered with pollen, and fertilisation has taken effect, there is a bundle of threads, originating in the base of the style, which hang down in the cavity of the ovary, and, floating there, convey the influence of the pollen to the points of the nuclei. So, again, in Asclepiads. In this tribe, from the peculiar conformation of the parts, and from the grains of pollen being all shut up in a sort of bag, out of which there seemed to be no escape, it was supposed that such plants must at least form an exception to the general rule. But before the month of November, 1828, the celebrated Prussian traveller and botanist, Ehrenberg, had discovered that the grains of pollen of Asclepiads acquire a sort of tails, which are all directed to a suture of their sac on the side next the stigma, and which at the period of fertilisation are lengthened and emitted ; but he did not discover that these tails are only formed subsequently to the commencement of a new vital 224 ACTION OF POLLEN-TUBES. [BOOK ir. action connected with fertilisation, and he thought that they were of a different nature from the pollen-tubes of other plants : he particularly observed in Asclepias syriaca that the tails become exceedingly long, and hang down. In 1831, the subject was resumed by Brown in this country, and by Adolphe Brongniart in France. These two distin- guished botanists ascertained that the production of tails by the grains of the pollen was a phenomenon connected with the action of fertilisation; they confirmed the existence of the suture described by Ehrenberg; they found that the true stigma of Asclepiads is at the lower part of the discoid head of the style, and so placed as to be within reach of the suture through which the pollen-tubes or tails are emitted ; they remarked that the latter insinuated themselves below the head of the style, and followed its surface until they reached the stigma, in the tissue of which they buried them- selves so perceptibly, that they were enabled to trace them, occasionally, almost into the cavity of the ovarium ; and thus they established the highly important fact, that this family, which was thought to be one of those in which it was impossible to suppose that fertilisation takes place by actual contact between the pollen and the stigma, offers the most beautiful of all examples of the exactness of the theory, that it is at least owing to the projection of pollen-tubes into the substance of the stigma. In the more essential parts these two observers are agreed : they, however, differ in some of the details, as, for instance, in the texture of the part of the style which I have here called stigma, and into which the pollen-tubes are introduced. Brongniart both describes and figures it as much more lax than the other tissue ; while, on the other hand, Brown declares that he has in no case been able to observe " the slightest appearance of secretion, or any differences whatever in texture between that part and the general surface of the stigma " (meaning what I have described as the discoid head of the style) . I have remarked that, in Morrenia odorata, an Asclepiad, the emission of tubes takes place to such an extent as to give the head of the stigma altogether the appearance of a mass of tow. (See Botanical Register, 1838, Misc. No. 129.) FUNCTION.] POLLEN TUBES. 225 The first act of fecundation in plants is, therefore, usually the emission of a tube by a pollen grain ; but the impregna- tion of the ovule must necessarily be a subsequent and perhaps different process, in consequence, among other things, of the distance which the pollen tube must travel through the stigmatic tissue before it reaches the ovule ; a distance computed by Morren to amount to 1150 times its own diameter in Cereus grandiflorus. This botanist states that, in that plant and the Vanilla impregnation does not in fact occur till some weeks after contact between the pollen and stigma has taken place. It is., however, worthy of remark, that the first act of fecundation produces an immediate effect upon the floral envelopes, In Orchids, a flower artificially fecundated will change colour and begin to fade in twenty-four hours at the latest after this has happened, although the same flower would have remained in beauty many days if not impregnated. It would, therefore, seem that actual contact between the pollen and the stigma is indispensable in all cases. Orchids have, however, been thought to offer an exception ; for in those plants nature has, on the one hand, provided special organs, in the form of the stigmatic gland and the caudicle of the pollen masses, to assist in the act of fertilisation ; and on the other appears to have taken great precautions to pre- vent contact, by so placing the anther that it seems iiext to impossible for the pollen to touch the stigma unless artifi- cially applied to it. Nevertheless, it is represented by Adolphe Brongniart, in a paper read before the Academy of Sciences at Paris, in July, 1831, that contact is as necessary in these plants as in others, and that, in the emission of pollen tubes, they do not differ from other plants. These statements have been followed up by Brown, in an elaborate essay upon the subject, in which the results that are arrived at by our learned countryman are essentially to the same effect. On the other hand, the observations of Francis Bauer, and the general structure of the order, seemed at variance with the probability of actual contact being necessary ; and, as Brown was obliged to have recourse to the supposition that the pollen of many of these plants must be actually carried by insects VOL. II. Q 226 EMBRYOLOGY. [BOOK 11. from the boxes in which it is naturally locked up, it seemed that the mode of fertilisation in Orchids was still unsettled ; and it must be admitted that the agency of insects, to which Brown had recourse in order to make out his case, was scarcely reconcileable with his supposition that the insect forms, which in Ophrys are so striking, and which, he says, resemble the insects of the countries in which the plants are found, ee are intended rather to repel than to attract." But although such arguments were not unobjectionable, it is, nevertheless, certain that Orchids require contact to take place between their pollen and stigma, in order to insure fertilisation. This has been shown by Professor Morren, and has now become in gardens a matter of notoriety. Conflicting statements as to what really occurs when the embryo is first generated in the amniotic sac, have for several years occupied the attention of Botanists. To enter into any discussion of the respective value of these state- ments would be less advantageous to the student than the record of the observations actually made by excellent and trustworthy observers. The real phenomena are explained in the following cases, described by botanists familiar with the microscope and expert in anatomical examination. In the nineteenth volume of the Linnaean Transactions, Dr. Herbert Giraud has published the following very detailed account of facts observed by him in Tropaeolum majus, a plant whose parts present peculiar facilities for examination. They are arranged under seven general heads, corresponding with as many progressive periods in the growth of the so-called female organs, extending from the completion of the anatropal development of the ovule, to the perfect formation of the embryo : or from the commencement of the expansion of the bud, to the complete formation of the fruit. "First Period. — On making a section of a carpel (just before the expansion of the bud), from its dorsum inwards towards the axis of the pistil, and in the direction of that axis, the solitary ovule is at the same time divided, and is found to have completed its anatropous development. Con- tinuous with that part of the columella which forms the FUNCTION.] EMBRYOLOGY OF TROP.EOLUM, 227 placenta, is a portion of rather firm and dense cellular tissue, inclosing a bundle of vessels, and forming the so-called umbilicus : this, with the vessels it incloses, descends in apposition with the placenta to form the raphe, and near the point where it terminates in the base of the ovule, the vessels are gradually lost, or rather terminate in closed extremities. The nucleus has only one tegumentary membrane (primine ?) at the apex of which is presented the exostome, or micropyle, opening close by, and to the outside of the umbilicus : so that the direction of the nucleus is exactly parallel with that of the axis of the pistil. The conducting tissue of the style may be traced between the columella, and that prolongation of the carpellary leaf which forms the style into the carpellary cavity, as far as the exostome, with which it is brought in con- tact by the anatropous development of the ovule. The vessels which proceed along the placenta to form the raphe, are spiral vessels and annular ducts ; and at the point at which they make a turn downwards towards the chalaza many of them end in closed extremities, while the vascular structure of the raphe usually terminates in a single vessel. These vessels, together with an analogous set which run along the dorsum of the carpel, proceed from a larger bundle of vessels, which in the receptacle bifurcates into these two sets. Second Period. — During the expansion of the bud, before the dehiscence of the anther, and, therefore, before impreg- nation, a small elliptical cavity appears near the apex of the nucleus, having a delicate lining membrane formed by the walls of the surrounding cells. This cavity is the embryo-sac ('sac embryonnaire/ Brongniart and F. Gr. F. Meyen; ' membrana anmii/ Malpighi ; ' quintine/ Mirbel.) From the exostome a minute canal may be traced in the apex of the nucleus, leading to the embryo-sac. The apex of the embryo-sac incloses, at this period, a quantity of organisable mucilage, containing many minute bodies having the appear- ance and character of cytoblast (Schleiden.) Third Period. — The apex of the nucleus, and of its tegu- mentary membrane, is now inclined and approximated towards the axis of the pistil. The embryo-sac is much enlarged and lengthened; its mucilage has disappeared; and in its place 228 DR. GIRAUD — EMBRYOLOGY [BOOK n. there is formed an elongated diaphanous utricle (primary utricle ; ' utricule primordiale/ Mirbel ; ' vesicule embryon- naire/ F. G. F. Meyen ; ' 1'extremite anterieure du boyan pollinique/ Schleiden) containing a quantity of globular matter (' globulocellular cambium/ Mirbel ; ( cytoblasts/ Schleiden). This primary utricle is developed wholly within the embryo-sac, from which it can be clearly seen to be distinct. Fourth Period (after impregnation has occurred). — The pollen tubes do not extend into the carpellary cavity ; but the fo villa, with its granules, is found abundantly in the passage leading from the style to the exostome. With the increased development of the embryo-sac, the primary utricle, as it elongates, becomes distinctly cellular, by the development of minute cells in its interior, while at the extremity, next the base of the nucleus, it is terminated by a spherical extremity, consisting of numerous globular cells. The primary utricle, at this period, assumes the character of the suspensor (Mirbel) ; and its spherical extremity constitutes the first trace of the embryo. Fifth Period. — At this stage the apex of the nucleus, with that of its tegumentary membrane, becomes directed more towards the axis of the pistil. The spherical extremity of the suspensor enlarges, and almost entirely fills the cavity of the embryo-sac ; and it now becomes more evident that it con- stitutes the axis of the embryo. The suspensor is, in a cor- responding degree, lengthened by an increase in the number and size of its cells ; while its upper extremity has now pro- truded through the apex of the embryo-sac, the apex of the nucleus, and through the micropyle. From this extremity there is a considerable development of cells, many of which hang loosely in the passage leading to the conducting tissue of the style, while others unite in forming a process which passes round the outside of the ovule into the carpellary cavity, and between the inner surface of the carpel and the outer surface of the ovule. This process of cellular tissue is composed of from nine to twelve rows of cells ; its extremity resembles in appearance, and in the anatomical condition of its cells, the spongiole of a root. When the ovule is removed FUNCTION.] OF TROP/EOLUM. 229 from its carpel, and slight traction is made upon this cellular process, the suspensor, with the embryo, may be withdrawn from the embryo-sac, through the exostome and apex of the nucleus ; thus proving the perfect continuit}7 of this cellular process with the suspensor, and through it with the embryo itself. Sixth Period, — The suspensor is now more attenuated, consisting only, as at first, of two rows of cells ; the cellular process, with which it is organically united, has reached the base of the ovule ; the cells of its extremity abound in cyto- blasts, showing it to be yet progressing in its development. With the increased growth of the embryo two lateral processes are observed proceeding, on opposite sides, from the axis and evidently forming the first traces of the cotyledons. Seventh Period. — All distinction between the nucleus and its tegumentary membrane ceases, as they are now united in one envelope inclosing the embryo-sac. The cellular process connected with the suspensor has become so much developed, that its extremity has passed around the base of the ovule and is directed towards the axis of the pistil. The lateral processes of the axis of the embryo have become distinct fleshy cotyledons extending backwards from their point of origin towards the radicle, as well as forwards in the direction of the plumule ; both which organs they inclose in corre- sponding depressions in their opposed surfaces. With the development of the radicle towards the exostome, the opposite extremity of the axis of the embryo (in the form of the plumule) extends towards the base of the nucleus, but is still inclosed in the depression formed in the concavity of the cotyledons. The subsequent changes consist chiefly in the great develop- ment of the cotyledons, which ultimately come to occupy the whole cavity of the nucleus, filling the space usually taken up by the albumen." Upon these facts Dr. Giraud observes, that the physio- logical inferences deducible from them contribute to the determination of many unsettled points involved in the theory of vegetable embryogeny, and serve to elucidate many obscurities relating to the morphology of the embryo. 230 DK. GIRAUD EMBEYOLOGY [BOOK n. " It has been shown," he proceeds, ' ' that the formation of the embryo-sac, and the development of cytoblasts within it, takes place at a period prior to the impregnation of the pistil ; and that even the primary utricle itself makes its appearance before the emission of the pollen from the anther, and before the expansion of the stigma; so that the origin of the primary utricle must not be referred to the influence of impregnation, as has been already pointed out by Mirbel and Spach in the case of Zea Mays. (See their paper in the Annals of Natural History, v. 228.) At its first appearance the primary utricle is seen to be quite distinct from the embryo-sac, even at its apex, with which, however, it is brought in contact at a subsequent period, and ultimately even penetrates that membrane ; so that, in this instance at least, the primary utricle cannot result from a depres- sion or involution of the embryo-sac, as is maintained by Adolphe Brongniart. After the expansion of the lobes of the stigma and its impregnation, the pollen-tubes may be traced in the conducting tissue of the style, but not so far as the micropyle : in the channel, however, leading to this point, the pollen-granules are found in abundance, and are doubtless brought in contact with the outer surface of the embryo- sac through the exostome and the minute canal in the apex of the nucleus. At this period the first trace of the embryo appears in the formation of the spherical body at the inferior extremity of the primary utricle, which has now assumed the character of the suspensor (umbilical cord). Hence, then, we are led to consider the origin of this simple spherical body, which is ultimately transformed into the embryo, as resulting from a peculiar process of nutrition, determined by the material or dynamic influence of the fo villa, conveyed through the medium of the primary utricle or suspensor. As it is through that organ that the embryo appears to derive its nourishment during the period of its development, we should from this function, as well as from its anatomical relations, consider the suspensor as the true umbilical cord; the medium of connection, therefore, between the ovule and the columella (or so-called placenta) ought not to receive the name of FUNCTION.] OF TROP^OLUM. 231 umbilical cord or funiculus, which terms it would be well to confine to the suspensor alone; while the former might retain the appellation of podosperm as referring to its relation to the ovule. ee As it is necessary that an umbilical cord should be organically united with the embryo, the impropriety of considering the organ described by Malpighi in that light will become sufficiently obvious. This structure consists of a minute cellular process extending from the base of the embryo-sac to the base of the nucleus, and has been found chiefly in the Cucurbitacese and Rosacese. It appears) how- ever, to be but a mere appendage of the embryo-sac, from which it takes its origin, and often never reaches the base of the nucleus, and therefore cannot be the medium of nutrition even to the embryo -sac. To this organ, therefore, it would be better to confine the term applied to it by Dutrochet, and name it the hypostate, as pointing out merely its anatomical relations. The cellular process proceeding from the extremity of the suspensor, next the exostome, around the outer surface of the ovule into the carpellary cavity is an organ of somewhat unusual occurrence, but from its mode of growth and struc- tural relations, it may be inferred to be of very essential importance to the origin and development of the embryo. Now it has been recently pointed out by F. G. F. Meyen, that in the great majority of instances the pollen-tube, after having penetrated the micropyle, is brought in contact with the apex of the embryo- sac, with which it there contracts an adhesion ; from this period the changes consequent on impreg- nation date their commencement ; and, under the direct influence of this immediate application of the fovilla to the embryo-sac, continue with uninterrupted regularity. But in the case of Tropseolum majus, as the pollen-tube never reaches the embryo-sac, some additional means are required to insure that influence of the fovilla on the primary utricle which is necessary for the development, at its extremity of the spherical cellular body, which subsequently becomes the embryo. This action, then, is effected by the projection of this cellular process from the primary utricle, which, by being immersed (so to speak) in the fovilla, is made the medium 232 GRIFFITH'S VIEWS [BOOK n. for the transmission of the latter to the primary utricle, and through it to the embryo itself; for which office the structure of its extremity (so like a spongiole) renders it peculiarly fitted. " It may now," concludes Dr. Giraud, " be shown how far the foregoing observations bear upon the undetermined question of the origin of the embryo. That in this plant the primary utricle and the future embryo never have any structural connexion with the extremity of the pollen-tube at their first origin, or at any subsequent period of their develop- ment, is sufficiently obvious from the fact, that the pollen- tube is never brought into contact with the embryo-sac. As the primary utricle makes its appearance before impregnation has occurred, it cannot be possible that that organ has ever formed the extremity of the pollen-tube, as is believed to be the case by Schleiden and Wydler. Moreover, as the primary utricle takes its origin wholly within the embryo-sac, and at the earliest period of its formation is not in contact with that membrane, it cannot have been formed by the pollen-tube pressing before it a fold of the embryo-sac in its passage into the cavity of that structure, as Schleiden has maintained." Griffith is equally opposed to the opinion of Schleiden, as to the action of the end of a pollen tube on the sac of the embryo. His paper in the Transactions of the Linncean Society, vol. xix., from which I make a few extracts, will well repay the most careful perusal. " The first process in the development of the seed, subse- quently to the penetration or application of the boyan to the embryo-sac, would in Santalum, Osyris, Loranthus, and Viscum, appear to consist of the formation of cellular tissue. This may be applied, I believe, to most if not to all instances. This cellular tissue appears to have two different origins; one, and this is the earliest in development, being, perhaps, referable to the embryo-sac, while the other appears directly referable to the anterior ends of the pollen tubes. " In no instance, perhaps, where the embryo is developed from the ends of the pollen tubes, does it become developed so immediately that no cells intervene between it and the end of the pollen tube ; this is particularly evident during the FUNCTION.] OF EMBRYOLOGY. 233 earlier stages of development. That part of the embryo in which the condensed tissues occur, and which, from its appearance and frequent tendency to constriction round its base, I at first suspected was the only part of the embryo (the rest being then funiculus), corresponds, I think, in situation with the collet ; it is very evidently not the point of the radicle, for this will subsequently be found so close to the vesicle as to authorise me in assuming that the greater part of the soft cellular tissues becomes the body of the root. "None of my observations have tended to confirm his (Schleiden's) idea of the inflection of the embryo-sac before the pollen tube ; and it appears to me sufficiently obvious, that if such were the case, the cylindrical bag constituting the ' embryo in its first stage of development/ would consist of three membranes or layers : viz., the first or outer, of the ordinary and uninflected membrane of the sac ; the second, of its inflected portion ; the third, of that of the pollen tube itself." M. Schleiden assumes the applicability of his conclusion, drawn from direct observation in several plants, to all others in which direct observation is more difficult, on three distinct grounds, the first of which, regarding the diameter of the tube outside the sac and just within it, is, I cannot but think, of very minor importance, neither does it present itself in Santalum ; the second, which would confine certain peculiar contents to the pollen tube, appears to me contradicted by Santalum and Loranthus ; and the third, which positively refers plurality of embryos to a plurality of pollen tubes, is contradicted in a most marked manner by Loranthus. In the Ray Reports we have the following translation of Link's remarks upon the observations made by M. Decaisne upon the Miseltoe ; a very anomalous plant : — " On examining the ovary in its earliest state, it presents a uniform mass, with two small interruptions of the cellular tissue ; the cells, however, soon unite again, in order to form a clear cellular tissue in the centre, surrounded by a green circle. No ovule is perceived in the ovary for a long time, not as far as the commencement of June, when the ovary has 234 EMBKYOLOGY OF VISCUM. [BOOK n- the thickness of a peppercorn. At a little later period, how- ever, an ovule may be discovered; the easiest method of effecting which is, to separate the central substance into two parts, which is best done by gently drawing it to and fro. The ovule forms a club-shaped excrescence, the cellular tissue of which is arranged in concentric layers ; each cell contains two phakocysts. On subsequently bringing the ovule, when it has assumed the shape of a small, rather compressed sub- stance, in contact with a drop of water, the water will penetrate it and drive out the phakocyst with some force. The application of a drop of tincture of iodine colours the interior yellow, but leaves the granules uncoloured, which only subsequently become coloured when iodine is applied. Two thin club-shaped bodies are found next to the ovules at this epoch, and some weeks earlier, three fibrous bodies, rather thickened at the end. The author considers these bodies as abortive ovules. The ovule, which is thin at the lower end, might be compared with an embryo-sac, if the position of the surrounding vascular system, and the com- parison with the other parts of the fruit, did not contradict it. The young embryo exhibits itself, as a small mass of cells, at the point of the ovule, and nearly in contact with what one might call the epidermis. The author never observed a trace of a pollen-sac in the interior of the ovary, nor did he ever discover the slightest indication of a special integument for the ovule ; so that the latter exhibits nothing more than a nucleus, as has been observed in the Santalacese, and even in the Olacinese. This nucleus is attached by its base to the bottom of the ovary, and has its point exactly in the opposite direction, so that the ovule must be regarded as orthotropus. The author never saw a cavity in the ovule of the miseltoe when the embryo was forming, neither did he ever find an embryo-sac. The embryo exhibits itself, first, as already mentioned, at the upper end of the ovule or nucleus ; and the embryo cell, or the young embryo itself, is subsequently seen to be attached to a series of cylindrical cells in the cavity of the ovule, which cells constitute a kind of umbilical cord, but without a vascular system." These observations tend to throw doubt upon the necessity UNCTION.] OVULE TUBES AND POLLEN TUBES. 285 or universal existence of pollen tubes.* Such processes, observes M. Decaisne, exist, indeed, " in some plants ; but in others, where papillae are situated upon the ovule, as in Arads, they have never been observed, and the papillae seem to be substituted for them; in other plants again, little bands descend from the base of the style, and are deposited in the seed near the micropyle ; for instance, in Composites and some others." Dr. Dickie, of Aberdeen, has carried this remark further, and has shown, that in many plants the tubes found, at the time of impregnation, in the foramen of the ovule, really originated there, and were not derived from the pollen. His very curious observations will be found at length in the 17th vol. of the Annals of Natural History, to which the reader is referred. He has ascertained their existence in plants belonging to Cucurbits, Chenopods, Buckwheats, and Sandal- worts; to which may be added Rushes, several Figworts, (Scrophulariaceae) Parnassia, and probably Orchids. By some it has been thought that the molecular motile matter found in the interior of pollen grains represented the germs of future embryos, and that the introduction of one such molecule into an ovule was necessary in order to insure the production of an embryo. But it has been shown that the molecules are starch : upon this matter Schleiden has the following remarks : — " It appears to me, that the very minute chemical and microscopical researches of Fritsche on the pollen (Peters- burg, 1837) have made an end of the so called pollen ani- malcules; for it would be contrary to the laws of animal nature, that the lively motions of these apparent infusoria should continue undisturbed after the addition of alcoholic solution of iodine (a poison that immediately kills all infu- soria and animal spermatozoa), as Fritsche states to be the case, and which in many instances I have observed. " In the (Enotherse, however, to which Meyen has par- ticularly referred, I have not been able to see anything of * Gasparrini asserts that the pollen of the Orange tree has no power of omitting pollen tubes. 236 SEXUALITY [BOOK n. pollen animalcules (saamenthierchens) ; and in these cases the contents of the pollen, quoad solida, also for the greatest part consist of starch. I have, at least, in (En. Simsiana, grandiflora, and crassipes, throughout, found nothing else in the pollen besides a solution of gum and those easily recog- nisable small crescent-formed bodies, which Brongniart has described as pollen animalcules. They are, however, decidedly starch, and continue starch even when the pollen tube is already deep in the nucleus of the ovule. In order, however, in this case, to detect the starch, we must employ the aqueous solution of iodine, for the alcoholic solution in the first place would coagulate the gum, and in the second it colours the starch so deeply that, on account of the smallness of the grains, one can no longer judge of their colour, and as they are entirely surrounded with the gum, they may easily be supposed to be dark brown. The curvilinear motions of these so called pollen animalcules, which are said to have been observed by a good many, are very easily explained, since at least many of them, being crescent-shaped, when in motion, appear bent to the left, the right, or appear straight, accord- ing to their position to the eye." With respect to the sexuality of plants, that at least would appear, from the facts above recited, to be established beyond controversy ; but lately there has arisen in Germany a school of Botanists, at the head of which are Schleiden and Endli- cher, who either deny it, or assert that the nature of the phenomenon connected with it has been misunderstood. Schleiden states that, " if the pollen tubes be followed into the ovule, the most delicate process perhaps that occurs in botanical investigations, it will be found that usually only one, rarely a greater number, penetrates the intercellular passages of the nucleus and reaches the embryo-sac, which being forced forwards, is pressed, indented, and becomes the cylindrical bag which constitutes the embryo in the first stage of its development, and which consequently consists solely of a cell of parenchyma supported upon the summit of the axis. This bag is therefore formed of a double membrane (except the open radicular end), viz. the indented embryo-sac FUNCTION.] SAID TO BE A MISTAKE. 237 and the membrane of the pollen tube itself. In Taxus, and especially in Orchis, he has been able to withdraw out of the embryo-sac that portion of the tube which represents the first stage of the embryo, and that indeed at a tolerably advanced period. " The tracing of the pollen tube into the interior of the embryo-sac is not so easy in all plants ; because the cells of the nucleus which are arranged around the summit of the embryo- sac are very firm and opaque, so that it and the pollen tube cannot be exhibited quite free. In these cases, however, three circumstances speak for the identity of the embryo with the pollen tube. 1. The constantly equal diameter of the latter, exterior to the embryo-sac, and of the former, just within it. 2. The invariable chemical similarity of their contents, shown by the reaction produced by the application of water, oil of sweet almonds, iodine, sulphuric acid, and alkalies. The general contents of the grain of pollen is starch ; and this either proceeds unchanged downwards through the pollen tube, or else passes along, after being changed by a chemico-vital process into a transparent and colourless fluid, which becomes gradually more and more opaque, and is coagulable by the application of alcohol : out of this, by an organising process, the cells are produced which fill the end of the pollen tube, extending, in Orchis Morio, far beyond the ovule, and thus forming the parenchyma of the embryo. 3. The identity of the embryo and the pollen tube is farther supported by the fact, that, in such plants as bear several embryoes, there is always precisely the same number of pollen tubes present as we find embryoes developed. "The most important result of these facts is, that the sexual classification hitherto adopted in botany is directly false : for, if the ovulum be understood in physiology to repre- sent that material foundation from which the new being becomes immediately developed, and if we term that portion of the organism in which this material commencement is deposited before it becomes developed the female organ, whilst that part which calls into action or promotes the development of the germ by means of its potential effects is termed the male organ, it is evident that the anther of the 238 POLLEN ANALOGOUS TO SPORES. [BOOK n. plant is nothing but a female ovarium, and each grain of pollen the germ of a new individual. On the other hand, the embryo-sac only works potentially, determining the organis- ation and development of the material foundation ; and for this reason, therefore, ought to be termed a male principle, were we not to consider, perhaps more correctly (without embarrassing ourselves with lame analogies taken from the animal kingdom), that the embryo- sac merely conveys new organisable fluids by means of transudation, and thus only serves the office of nourishment. " In the next place, the process of development of the embryo, as already described,, easily establishes the analogy of Phanerogamous plants and those Cryptogamic plants in which the spores are evident conversions of the cellular tissue of the foliaceous organs or leafy expansions; for the same part furnishes the groundwork of a new plant in both groups, and the only difference existing between the two is this ; in Phanerogamse a previous formative process in the interior of the plant precedes a period of latent vegetation, whilst in Cryptogamse the spore (the grain of pollen) developes itself as a plant without previous preparation. Difficulties nevertheless occur here in the consideration of Mosses and Hepaticae, and more particularly in the enigmatical Mar- sileacese." These statements have now been copiously illus- trated by excellent figures in Schleiden's memoir Ueber Bildung des Eichetis, und Entstehung des Embryos bei den Phanerogamen. The opinion of Endlicher is to a certain extent that of Schleiden ; that is to say, he considers what we call pollen analogous to the spores of Cryptogamic plants, and conse- quently the anther a female organ, whose contents perform an act similar to that of germination, when they fall upon the stigma; he does not, however, with Schleiden, assign a male influence to the sac of the amnios, but he attributes that property to the stigmatic papillae, whose moisture lubri- cates the grains of pollen when they fall upon them.* I * See Qrundzuge einer neuen Theorie der Pflanzenzeigung. Professor Wydler of Berne, also, insists upon the pollen being the female apparatus, and he denies that plants have two sexes. (RechercJies sur V Ovule, &c., des Scrofulaires.) These FIMTION.] SELF IMPREGNATION. 239 know of no one else who maintains this last opinion ; but it deserves to be noted that Morren observed a circulating move- ment (he calls it cyclosis) in the fluid filling the papillae of Cereus grandiflorus at the period of impregnation. Notwithstanding the great mass of evidence which botanists possess in favour of the sexuality of plants, there are certain facts which appear to be irreconcileable with that property ; and which wait for further examination. Mr. John Smith has described in the Linncean Transactions, vol. xviii. p. 510, a Spurge wort, named Coelebogyne ilicifolia, which, although absolutely female, not possessing a trace of pollen, nevertheless produces perfect seeds. He inclines to the belief that a viscid fluid issuing from glands below the ovary, may produce an effect by exciting the action of the pistil, a supposition which receives some support from the young stigma being often smeared with this fluid. The state- ment that no male apparatus is discoverable on this plant is confirmed by Francis Bauer and others. We ourselves have often examined the plant without perceiving a trace of stamens or pollen. Dr. Fresenius has observed that in Datisca cannabina, when female plants remain isolated, they are able neverthe- less to produce ripe fruit in abundance; and he concludes that this and other purely female forms are, in the absence of male organs, endowed with the capability of developing, by a purely vegetative process, the highest vital product, the terminal bud (or seed.) In the summer of 1837, a female specimen of the above plant, in the Frankfort Botanical Garden, threw up a stem which now bears male flowers also. (Linwea, 1839.) Spallanzani, Girou de Buzareingues, and others affirm that speculations have all arisen out of the undoubted fact, that the development of spores and pollen grains takes place in the same manner, and that there is considerable resemblance in their final structure. This was, I think, first noticed by Mohl (Ueber die EntwicUtmg der Sporen,