Antheridium

“ The term “colony” is, perhaps, inappropriate, as the whole mass of cells arises from a single one, and may properly be looked upon as an individual plant.
[3] Algæ (sing. alga) .
[4] “Host,” the plant or animal upon which a parasite lives.
[5] The antheridia, when present, arise as branches just below the oögonium, and become closely applied to it, sometimes sending tubes through its wall, but there has been no satisfactory demonstration of an actual transfer of the contents of the antheridium to the egg cell. ”

“ The prothallus is exceedingly small, being little more than a group of cells forming an antheridium. Should there be sufficient moisture about, the spermatozoids which are produced by the antheridium swim towards the archegonia in any female prothallus which may be near. Fertilization then takes place, and the final outcome is the young plant. Now and again in certain species it is seen that the megaspores develop to such an extent within the sporangium that fertilization [21] takes place, and even an embryo or young plant may be formed. ”

“ The body cell corresponds to the central cell of an antheridium; it increases in size more than double, and its nucleus is enlarged in the same proportion. Hereupon this central cell undergoes commonly a cross or oblique division, by means of which two generative cells are created. The stalk cell of the antheridium is divided apparently only under certain conditions. Then the stalk cell and the first prothallial cell lose their independence, and the liberated generative cell passes into the pollen tube. ”

“ The ripe male spore-contents are changed into a few cells, one of which remains sterile and is considered the prothallus, while from the other cells—which taken as a whole constitute the antheridium—the cells which afterward bear the antherozoids are formed. ”

“ De Bary considers that, bearing in mind analogous phenomena observed in Vaucheria, and the direct observations of Pringsheim, [G] the cellulose membrane on the surface of the gonospheres is only the consequence of a sexual fecundation.
In Achlya dioica the antheridium is cylindrical, the plasma which it encloses is divided into particles, which attain nearly [170] the size of the zoospores of the same plant. These particles become globose cells, grouped in the centre of the antheridium. ”

“ The reproductive organs ultimately produced on the same or on different individuals are of two kinds, the antheridia and archegonia; the origin of both is from single superficial cells of the prothallus. The antheridium (fig. 8) at maturity consists of a layer of cells forming the wall which encloses a group of small cells; from each of the latter a single motile spermatozoid originates. The archegonium (fig. 9) consists of a more or less projecting neck and the venter, which is usually enclosed by the tissue of the prothallus. ”

“ Functional male and female organs have been shown to exist in Pyronema and Boudiera; in Lachnea stercorea both ascogonia and antheridia are present, but the antheridium is non-functional, the ascogonial (female) nuclei fusing in pairs; this is also the case in Humaria granulata and Ascobolus furfuraceus, where the antheridium is entirely absent. In H. rutilans, however, both sexual organs are absent and the ascogenous hyphae arise apogamously from the ordinary hyphae of the mycelim. In all these cases the ascogonium and antheridium contain numerous nuclei ”

“ There will always be, in such a case, a single apical cell, of a more or less distinctly triangular form. The annexed figure of the developing antheridium of a Liverwort (Riccia) is a typical example of such a case. In Fig. 185 which represents a “gemma” of a Moss, we see just the same thing; with this addition, that here the lower of the two original cells has grown even more quickly than the other, constituting a long cylindrical stalk, and dividing in accordance with its shape, by means of transverse septa. ”

“ Among gymnosperms it is not difficult to see that it consists of the pollen-grain and the embryo sac with its endosperm. The male prothallus is reduced and rudimentary, and one cell of the pollen-grain, representing the antheridium, produces a tube instead of antherozoids. The endosperm is the female prothallus, and in it the germ-cell develops. The asexual generation is the plant that grows from the fertilized germ. In the angiosperms the sexual generation is reduced to its simplest form, namely, a single cell for the male part, and one or a few cells for the female. ”

“ Towards the time when the gonospheres are formed it may be observed that each antheridium sends to the interior of the oogonia one or several tubular processes, which have crossed its side wall, and which open at their extremity in order to discharge their contents. These, while they are flowing out, present some very agile corpuscles, and which, considering their resemblance to those in Vaucheria, to which the name of spermatozoids are applied, ought to be considered as the fecundating corpuscles. After the evacuation of the antheridia the gonospheres are found to be covered with cellulose ”

“ The nomenclature used here for the various cells of the antheridium is somewhat different from that usually used. It was thought best to use terms more in harmony with those used in the Pteridophytes in order to avoid confusion. ”

“ In the rotting tissues branches of the older mycelium similarly swell up and form antheridia and oogonia (fig. 4) . The contents of the antheridium are not set free, but that organ penetrates the oogonium by means of a narrow outgrowth, the fertilizing tube, and a male nucleus then passes over into the single oosphere, which at first multinucleate becomes uninucleate before fertilization. Pythium is of interest as illustrating the dependence of zoospore-formation on conditions and the indeterminate nature of conidia. The other genera are more purely parasitic ”

“ C the two cells of the antheridium have opened by transverse clefts; beneath is seen the microspores enclosed by the hardened mucilage; D spermatozoids still enclosed in the mother-cells.
Fig. 215.—Salvinia natans. A, B Female prothallia, f-f, protruding from the macrospore which is still enclosed in the macrosporangium; œ archegonia. C An embryo (× 16) still in connection with the spore (s) : a the scutiform leaf; b-e the subsequent foliage-leaves, of which b and c stand singly, d-e-v in a whorl; v the submerged-leaf; f-f wing-like lobes of the prothallium: m the foot.
Sexual generation. ”

“ M, ripe antheridium, × 300. sp. sperm cells. N, O, antheridia that have partially discharged their contents, × 300. P, spermatozoids, killed with iodine, × 500. v, vesicle attached to the hinder end.
In choosing spores for germination it is best to select those of large size and containing abundant chlorophyll, as they germinate more readily. Especially favorable for this purpose are the spores of the ostrich fern (Onoclea struthiopteris) (Fig. 70, I, J) , or the sensitive fern (O. sensibilis) . Another common and readily grown species is the lady fern (Asplenium filixfœmina) (Fig. 70, H) . ”

“ The sperm-cells escape from the antheridium and in the water that collects on the prothallus are carried to the archegonium, where fertilization of the egg takes place. From the fertilized egg-cell a plant grows, becoming a “fern.” In most cases the prothallus soon dies. The prothallus is the gametophyte (from Greek, signifying the fertilized plant) .
The fern plant, arising from the fertilized egg in the archegonium, becomes a perennial plant, each year producing spores from its fronds (called the sporophyte) ”

“ The protonemal filaments may be made to grow from almost any part of the plant by keeping it moist, but grow most abundantly from the base of the stem.
The sexual organs are much like those of the liverworts and are borne at the apex of the stems.
The antheridia (Figs. 59, 60) are club-shaped bodies with a short stalk. The upper part consists of a single layer of large chlorophyll-bearing cells, enclosing a mass of very small, nearly cubical, colorless, sperm cells each of which contains an excessively small spermatozoid. ”

“ The act of fertilization may be easily observed by laying fresh antheridia into a drop of water containing recently discharged egg cells. To obtain these, all that is necessary is to allow freshly gathered plants to remain in the air until they are somewhat dry, when the ripe sexual cells will be discharged from the openings of the conceptacles, exuding as little drops, those with antheridia being orange-yellow; the masses of oögonia, olive. Within a few minutes after putting the oögonia into water, the egg cells may be seen to escape into the water, when some of the antheridia may be added. ”

“ This attracts sufficient moisture to burst open the outer, and then it begins to increase by the subdivision of its cells, until the primary green prothallus D is formed. This falls to the ground, and, being furnished on its under side with thread-like fibres, fixes itself to the earth, and thus is developed the rhizome, or root of the future plant. In each of the antheridia, which are numerous, a cell is formed, chiefly filled with albuminous matter and free spores, each having attached a flat ribbon-like filament, or stermatoid, curled in a spiral manner. ”

“ The structure of the stem and leaves is peculiar. The former shows on cross-section a thin-walled central tissue surrounded by a zone of thick-walled cells. Outside this come one to five layers of large clear cells, which when mature are dead and empty; their walls are strengthened with a spiral thickening and perforated with round pores. They serve to absorb and conduct water by capillarity. The leaves have no midrib and similar empty cells occur regularly among the narrow chlorophyll-containing cells, which thus appear as a green network. The antheridia are globular and have long stalks. ”

“ The filament soon broadens into a ribbon-shaped thallus, several cells thick, which is closely applied to the rock. Erect branches may arise from the protonema, and gemmae may be developed on it. The stem of the plant, which arises in the usual way, has no conducting strand and the leaves may or may not have midribs. The leaf grows by a dome-shaped instead of by the usual two-sided initial cell. The antheridia are long-stalked. The upper portion of the archegonial wall is carried up as a calyptra on the sporogonium, which, as in Sphagnum, has no seta and is raised on a pseudopodium. ”

“ The tissues are developed from a single apical cell, but it is difficult to obtain good sections through it.
The antheridia are borne singly at the bases of the leaves on the special branches already described (Fig. 53, A, an.) . By carefully dissecting with needles such a branch in a drop of water, some of the antheridia will usually be detached uninjured, and may be readily studied, the full-grown ones being just large enough to be seen with the naked eye. They are globular bodies, attached by a stalk composed of two rows of cells. ”

“ One "generation," the "sexual," consists of a tiny, green, plate-like object, termed the [Pg 34] prothallium (Fig. 8) . This is connected with the soil by hair-like roots. On its lower surface are borne usually both the reproductive organs of the fern, the antheridia, corresponding to the stamens or fertilizing organs of the flower, and the archegonia, performing the office of the flower's pistils, inasmuch as their germ-cells receive the fertilizing substance produced by the antheridia. But no seeds are formed as the result of this fertilization. ”

“ Underleaves mostly bifid (or 3–4-cleft in n. 1) ; divisions mostly entire.
1. L. bidentàta, Dumort. Stems 1–2 ́ long, procumbent, sparsely branching; leaves pale green, ovate-triangular, acutely 2-toothed, the teeth oblique with a lunulate sinus; monœcious; perianth oblong-triangular, lacinate; antheridia 2–3 in a cluster, axillary.—On rocks in shady rills; not common. (Eu.)
2. L. Austìni, Lindb. Creeping; leaves uniformly deeply lobed, the lobes and usually the sinus acute; underleaves comparatively small, the lobes subulate; cells small; monœcious; antheridia solitary in the upper axils. ”

“ The spore on germination gives rise to a small thalloid structure, the prothallium, on which the sexual organs are developed; this is the gametophyte or sexual generation. The sexual organs have the form of typical archegonia and antheridia. From the fertilised egg-cell there is developed the Pteridophyte plant or sporophyte, which bears the spores. This asexual generation shows a well-marked external differentiation into stem and leaves, and bears true roots. Internally the tissues exhibit a high degree of differentiation into distinct tissue-systems. ”

“ The oosphere is not differentiated within the wall of the oogonium, but certain cells known as wendungszellen, the significance of which has given rise to much speculation, are cut off from the basal portion of the parent-cell during its development. The antheridia are spherical orange-coloured bodies of very complex structure. The antherozoid is a spirally-coiled thread of protoplasm, furnished at one end with a pair of cilia. It much more resembles the antherozoids of Bryophyta and certain Pteridophyta than any known among other algae. ”

“ Sexual reproduction by antheridia and archegonia, which are immersed in the thallus, or sessile or pedicelled upon it, or borne on a peduncled receptacle. The fertilized archegonium develops into a capsule (sporogonium) closely invested by a calyptra, which ruptures above as the ripened capsule (containing numerous spores and usually elaters) pushes upward. It is also commonly surrounded by a usually double involucre, the inner (often called perianth) more or less tubular, the outer tubular or more often foliaceous, sometimes wholly wanting. ”