Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/150

Rh 140 BOTANY [REPRODUCTIVE ORGANS. site to the stamens, as in Crassula rubens (fig. 172). In some flowers, as Jatroplia Curcas, in which the stamens are not developed, their place is oc cupied by glandular bodies form ing the disk. In Gesneraceae and Cruciferte the disk consists of tooth -like scales at the base of the stamens (fig. 227). The parts composing the disk some times unite and form a glandu lar ring, as in the Orange ; or they form a dark-red lamina covering the pistil, as in Pseonia Moutan (fig. 235) ; or a waxy lining of the calyx tube or hol low receptacle, as in the Hose ; or a swelling at the top of the Plate VII. ovary, as in Umbellifene, in which the disk is said to be epigynous. The enlarged torus covering the ovary in Nymphtea and Nelumbium may be regarded as a form of disk. Male organs. Crypto gams. Fig. 235. Flower of Tree Pasony (Pceonia Moutan), deprived of its corolla, and showing the disk in the form of a fleshy expansion covering the ovary. 2. Male Organs in Cryptogams. Sexual organs have not as yet been demonstrated in all Cryptogamic plants ; but in most of them certain structures representing the male organs have been found. These are termed Antheridia or Pollinodia (figs. 236, 250). They are closed sacs of various forms, rounded, ovate, oblong, clavate, flask-like, tkc., developed from various parts of the plants, and composed either of one or of many cells enclosing a single central cell. In the interior of this organ small cells (fig. 236, c) are formed of varying shape, con taining in their interior peculiar bodies, termed antherozoids, spermatozoids, or pliytozoa (fig. 237). These are in most cases filamentous spirally coiled cells, frequently with cilia Fig. 236. Fig. 210 Fig. 239. Fig. 241. c, contammg phytozoa coiled up in their interior. The phytozoa have a thickened extremity, whence proceeds a tapering tail-like process. Along with abo^eamheS * W SCPai ate fllamentS r ^ ^^ s * which ar P&quot;&amp;gt;bably F of ?hIvA 8I 7&amp;lt;r? tOZ i(1 7 ! /! c j lla ! dischar etl fr m a cellule in the antheridium e Forked Spleenwort (AipUnium Kptentrtonale) Fl Shv?J ;7n A &quot; wm, d n m &quot; ?, r z thce &quot;:, of a Sea-weed (Fucu* vrratu,), containing conccptacle antheridlnm there are paraphyscs united in the same FIG 239. Antheridium of .1 Sea-weed (Fucus serratus), still containing two attaS m SaC- T Uie bl ad PSrt f the 1&amp;gt;h - vtoz a two vftratne clUa are F n; Mc^n ifftloh^&quot; 01108 f m the aXi f Whlch ai iSC3 thc Ucule Il t 2 o 4 i^ 10 ! e fl?, f ^T b&amp;lt; ; in S. a Bunded body with eight radiating valves lally, and filaments containing phytozoary cells internally. attached, by means of which they move rapidly through the water. In some cases there are no cilia, as in the Al-al group of Flondese; and the antherozoids of all Al#e differ Partitioned filament of Charn, consisting of a series of cellules containing phytozo:i, one of which is seen escaping in the form of a spiral thread. from those of other Cryptogams in never being filamentous, but short and more or less rounded. The amount of twist ing of the antherozoid varies ; in some llhizocarps there are as many as a dozen coils. Autheridia of this kind have been demonstrated in all vascular Cryptogams, but only in some Thallogens have such structures been seen. In Characese, however, the antheridium, which is here termed globule (fig. 240), has a peculiar structure, differing from all other Cryptogams. It is a globular case, formed by eight flat cells, of which four are quadrangular and four are triangular ; and these are folded at the margins so that the edges of contiguous plates dovetail (fig. 241). These are termed shields. Into the cavity of the globule the terminal cell of the stalk supporting it projects. From the centre of each shield projects ou the inner surface a large oblong cell or man- ubrium, which in turn bears at its apex a round ish cell termed the Jiead. From each head-cell six secondary head-cells pro ject, from each of which pass off f ourslender separ ate filaments (fig. 242) containing antherozoids. When mature the antheridium is ruptured, anil the mother-cells of the antherozoid escape and discharge the antherozoids into the surrounding medium which is always water fertilization only being effected in water, by which the antherozoids are carried to the female organ. In some cases, however, among Thallogens the antheridium actually penetrates into the female organ. Antheridia are pro duced on various parts of plants. Where they have been found amongst Thallogens, they arise from defi nite portions of the cellular thallus. In thalloid HepaticjE they may be sunk in the substance of the thal lus, or they may be im bedded in the upper surface of a peltate stalked disk rising from the thallus, as in Mar- chantia (figs. 243,244). In Mosses they may be seated within the same whorl of leaves or peri- chsetiuui as the female organs, or they may be separate and surround ed by a perigone ; but they are always formed upon the leaf-bearing axis, either terminal or lateral. In Ferns and Equisetum they 243. A species of Liverwort (AtarcJiantia polymwplta) with its green thallus t, bearing a cup-like body g, in which minute cells or free buds are seen, and a stalked receptacle f, r. In the substance of the disk-like receptacle r cells are produced containing phytozoa. These are considered antheridia. produced on the surface usually the lower surface of a cellular flattened expansion, termed a prothallus (figs. 245, 250), in close proximity to the female organs. In Characea3 they always arise from the termination of one of the whorled leaflets. In some Lycopodiacese no antheridia have as yet been found ; but in Selaginella, Isoetes, and in the Rhizo- carpese, hollow sacs, termed microsporanyia (figs. 246, 248), are produced in the axil of certain leaves of tho
 * iG.236.-Anther.dmma of the Hair-moss (Polytnchum), consisting of cellules