973 



MUSCI. 



MUSCI. 



971 



Gymnostomum ovatum, 



\, a Seta, bearing on the apex an urn, from which the opercnlum is rising, 

 proceeding from an apophysU at the base, where it is surrounded by para- 

 physes ; 2, a group of young Urns, among which a few paraphyses are mixed ; 



3, a cluster of gtainimdia and Paraphyses, surrounded by scale-like leaves ; 



4, three Staminiuia surrounded by four Paraphyses ; 5, a Spore ; 6, the same in 

 the first stage of germination j 7, the same in a more advanced state. 



Mosses and Hcpaticce, and of the peculiar organs containing analogous 

 spiral filaments in the Characece, were for a long time the chief facta 

 brought forward by those who supported the sexual hypothesis ; and 

 in the endeavour to carry out the view into the other tribes, a similar 

 nature to that of the antheridia was attributed to most varied 

 structures in the Ferns and other plants. These attempts to find 

 distinct sexual organs were in some instances pursued with so little 

 judgment, that the opinion has of late years fallen in some degree 

 into discredit, and two circumstances contributed still further to 

 strengthen the doubts which were entertained. The first was the 

 exact analogy pointed out by Professor Von Mohl, between the mode 

 of development of the spores of the Cryptogamia and the pollen- 

 grains of the flowering plants, which interfere very importantly to 

 prevent any comparison between the sporangia and ovaries, and 

 apparently determined the analogy of the former to be with anthers. 

 The second was the discovery by Professor Niigeli, of organs pro- 

 ducing spiral filaments, therefore analogous to the antheridia of the 

 Hones, on the germ frond, or pro-embryo developed from the spores 

 of the Ferns. 



" At the same time, the facts observed in Pilvlaria were altogether 

 equivocal. Mr. Valentine traced the development of the larger spores, 

 exhibiting in germination an evident analogy to ovules, from cells 

 closely resembling the parent-cells of pollen and spores ; while Pro- 

 fessor Schleiden stated that he had observed a fertilisation of these 

 supposed ovules by the smaller spores resembling pollen-grains, and 

 thus seemed to remove the ground for attributing a fertilising influence 

 to the spiral filaments contained in the so-called antheridia of the 

 Cryptogams. 



"To this state the question remained until 1848, when Count 

 Snminski published his observations on the germination of Ferns, 

 showing that the researches of Niigeli had been imperfect, and that 

 two kinds of organs are produced upon the pro-embryo of the Ferns, 

 one kind analogous to the antheridia, and the other to the pistillidia 

 of Mosses ; from the latter of which the true Fern stem is produced, 

 like the seta and capsule from the same organ in the Mosses ; further 

 stating that he had actually observed a process of fertilisation. Soon 

 after this M. G. Thuret discovered antheridia like those of the Ferns 

 in the E'/uitetacece ; Niigeli had previously published, in opposition 

 to Schleiden's observations, an account of the production of spiral 

 filaments from the small spores of Pilularia; and finally, M. Mettenius 

 discovered them in the small spores of Isoetes. Thus they were 

 shown to exist in all the families above enumerated, with the exception 

 of the Lycopodiacca, in which they have recently been stated to exist 

 by M. Hofmeister. 



" The antheridia of the Mosses occur in the axils of the leaves or 

 collected into a head, inclosed by numerous variously modified leaves 

 at the summit of the stem. They are produced either on the same 

 heads as the pistillidia, or in distinct heads on the same individuals, 

 nch Mosses being called monoecious ; or the heads are found only 

 on distinct individuals, such Mosses being termed dioecious. The 

 structure of the antheridium in exceedingly simple ; it consists of an 

 elongate, cylindrical, or club-shaped sac, the walls of which are com- 

 posed of a single layer of cells, united to form a delicate membrane. 

 Within this sac are developed vast numbers of minute cellules, 

 completely filling it, and, the sac bursting at ita apex at a certain 



period, these vesicles are extruded. When the nearly perfect sacs 

 are placed in water, the vesicles within appear to absorb water, and 

 sweU so as to burst the sac of the antheridium, and often adhering 

 together, they collectively appear to form masses larger than the cavity 

 from which they have emerged. Through the transparent walls may 

 be seen a delicate filament with a thickened extremity, coiled up in 

 the interior of each vesicle. Often before the extrusion, but always 

 shortly after, a movement of this filament is to be observed when the 

 object ia viewed in water under the microscope. The filament is to 

 be seen wheeling round and round rapidly within the cellule, the 

 motion being rendered very evident by the distinctness of the thickened 

 extremity of the filament, which appears to be coursing round the 

 walls of the cellule in a circle. According to Unger, this filament 

 breaks out of its parent-cellule in Sphagnum, and then appears as a 

 spiral filament moving freely in water, in fact, as one of the so-called 

 Spermatozoa. 



" The pistillidia of the Mosses are the rudiments of the fruit or 

 capsules. When young, they appear as flask-shaped bodies with long 

 necks, composed of a single cellular membrane. The long neck 

 presents an open canal like a style, leading to the enlarged cavity below, 

 at the base of which, according to Mr. Valentine, is found a single 

 cell projecting free into the open space. The single cell is the germ 

 of the future capsule ; at a certain period it becomes divided into two 

 by a horizontal partition, the upper one of these two again divides, 

 and so on until the single cell is developed into a cellular filament, 

 the young seta ; the upper cells are subsequently developed into the 

 um and its appendages, and as this rises, it carries away with it, as 

 the calyptra, the original membrane of the pistillidium, which 

 separates by a circumscissile fissure from the lower part, the future 

 vaginula. These observations of Valentine are not exactly borne out 

 by those of Schimper in some of the detail points. According to this 

 author, the lower part of the pistillidium (the germen of Dr. Brown) 

 begins to swell at a certain time, when a capsule is to be produced, 

 becoming filled with a quantity of what he terms ' green granulations.' 

 As soon as the thickness has become about that of the future seta, 

 the cell-development in the horizontal direction ceases, and its activity 

 is directed chiefly to the upper part, which begins to elongate rapidly 

 in the direction of the main axis. This elongation causes a sudden 

 tearing off at the base, or a little above it, of the cell-membrane 

 enveloping the young fruit, and the upper part is carried onwards as 

 the calyptra; the lower part, when any is left, remains as a little 

 tubular process surrounding the seta. While the young fruit is being 

 raised up by the growth of the seta, the portion of the receptacle 

 upon which the pistillidium is borne, becomes developed into a kind 

 of collar, and at length into a sheath (the vaginula) surrounding the 

 base of the seta, which is articulated into it there. 



" M. Hofmeister again describes the details much in the same way as 

 Mr. Valentine. He states that there exists at the point where the 

 style and germen of the pistillidium join, a cell, developed before the 

 canal of the style has become opened. In those pistillidia which pro- 

 duce capsules this cell begins at a certain period to exhibit very active 

 increase ; it becomes rapidly divided and subdivided by alternately 

 directed oblique partitions into a somewhat spindle-shaped body, 

 formed of a row of large cells. Meanwhile the cells at the base of 

 the germen are also rapidly multiplied, and the lower part of the 

 pistillidium is greatly increased in size. The spindle-shaped body 

 continues to increase in length by the subdivision of its uppermost 

 cell by oblique transverse walls, and the opposition which is offered 

 by the upper concave surface of the cavity of the germen causes the 

 lower conical extremity of the spindle-shaped body to penetrate into 

 the mass of cellular tissue at the base of the germen a process which 

 resembles the penetration of the embryo into the endosperm in the 

 embryo-sac of certain flowering plants. The base of the spindle- 

 shaped body, which is in fact the rudiment of the fruit, at length 

 reaches the base of the pistillidium, and penetrates even some distance 

 into the tissue of the stem upon which this is seated. The growth 

 of the upper part going on unceasingly, the walls of the germen are 

 torn by a circular fissure, and the upper half is earned upwards, 

 bearing the calyptra ; the lower part forms the vaginula. The upper 

 cell of the spindle-shaped body then becomes developed into the 

 capsule, and the calyptra often becoming organically connected with 

 this, as the base of the seta does with the end of the stem, it in such 

 cases undergoes further development during the time it is being carried 

 upwards by the growing fruit. 



" The view now entertained by Schimper, Hofmeister, and others of 

 the reproduction of the Mosses is, that the antheridia are truly male 

 organs, and that they exert, by means of the spiral filaments, a fer- 

 tilising influence upon the pistillidia, it being assumed that those 

 bodies, or the fluid which they are bathed in, penetrate down the canal 

 of the style, or neck-like portion of the pistillidium, to reach the 

 minute cell, the supposed embryonal cell, situated in the globular 

 portion or germen of the pistillidium, and thus render it capable of 

 becoming developed into a perfect fruit. 



" No such process of fertilisation has actually been observed in the 

 Mosses, and therefore all the evidence is at present merely circum- 

 stantial, but this is very strong. In the first place it is stated as an 

 undoubted fact by Schimper and Bruch, that in the dioecious Mosses, 

 those on which the antheridia and pistillidia occur in separate plants, 



