386 
VASCULAR CRYPTOGAMS. 
often produced on the same prothallium. In the Rhizocarpeae, Selaginelleae, and* 
Isoetese, on the other hand, the separation of the sexes is ah-eady prefigured by the 
two kinds of spores, the Macrospores being female, in so far as they develope 
a small prothallium, which produces exclusively archegonia, or sometimes only 
a single one ; the Microspores being male, inasmuch as tliey develope a still smaller 
prothallium bearing exclusively antheridia. The female prothallium of the Rhizo- 
carpeae is a small appendage of the macrospore, formed in its interior but afterwards 
developed externally although nourished by it; in Selaginelleae and Isoeteae the 
prothallium is developed in the spore itself, filling it up with a mass of tissue, the 
archegonia becoming exposed only by the splitting of the cell-wall of the spore. 
The male prothallium consists, in these groups of plants, of a single sterile or 
vegetative cell, and of a larger or smaller number of cells in which antherozoids 
are developed. 
The Archeg07iia of Vascular Cryptogams, like those of the Muscineae, are 
bodies, consisting of a ventral part which encloses the oosphere, and of a neck, 
usually short and composed of four longitudinal rows of cells. The two groups 
differ in the fact that in Vascular Cryptogams the tissue of the wall of the ventral 
part is formed from the prothallium itself; and the ventral part of the archegonium 
is therefore enclosed in the tissue of the sexual generation, the neck only projecting 
beyond it. The archegonium originates from a superficial cell of the prothallium 
which is divided by a tangential wall into two, an external and an internal. The 
former forms, by intersecting longitudinal and subsequent transverse divisions, the 
four rows of cells of the rather short neck ; the latter grows outwards between the 
neck-cells into a projection which becomes separated, forming the neck-cell, and 
another segment is cut off from the large inferior cell (the central cell, Janczewski) 
to form the ventral canal-cell. Thus there arises from the original internal cell an 
axial row of three cells, the lowest of which is the oosphere. The two neck-cells 
become converted into mucilage as in the Muscineae. The mucilage thus produced 
in the neck finally swells up considerably, forces apart the four apical cells of the 
neck, and is expelled ; an open canal is thus formed, leading from without to the 
oosphere ; the expelled mucilage appears to play an important part in the conduc- 
tion of the * swarming' antherozoids to the opening of the neck. Fertilisation is 
always effected by means of water, which determines the opening of the antheridia 
and archegonia, and serves as a vehicle for the antherozoids. The advance of these 
latter as far as the oosphere, and even their entrance into and coalescence with its 
protoplasm, has been directly observed in the different groups. 
The Antherozoids'^ are, like those of the Muscineae, spirally coiled threads usually 
with a number of fine cilia on the anterior coils. In the cases hitherto observed they 
arise from the peripheral part of the protoplasm of their small mother-cells, a central 
vesicle of protoplasm, containing starch-grains, being left over, which, adhering to a 
posterior coil of the antherozoid, is often dragged along by it, but is detached before 
^ [On the development of the antherozoids of the Vascular Cryptogams, see Strasburger, Zell- 
bildung und Zelltheilung, 3rd. ed. 1880, The formation of the antherozoid is, in all cases, preceded 
by the disappearance of the nucleus of the mother-cell, its substance becoming diffused throughout 
the protoplasm.] 
