444 



VASCULAR CRYPTOGAMS, 



but finally becomes detached. When the antherozoids are formed in their mother- 

 cells, the exospore bursts at the apex, the endospore swells up as a hyaline bladder, 

 which finally bursts and allows the escape of the antherozoids (Fig. 310, B). 



The Female Prothallium is formed within the apical papilla of the macrospore 

 from a small part of its protoplasm, and only partially emerges at a later period 

 from the spore-cavity, but remains united with the latter, closing it by its basal 

 surface, for the purpose of using up the food-materials (starch-grains, fatty oil, 

 and albuminous substances) which are stored up there. The separate stages in 

 the first formation of the prothallium are still in many respects not clear ; but it is 

 certain that it arises from a collection of protoplasm in the cavity of the papilla ; 

 this protoplasm immediately breaks up into several cells, which, according to 

 Hanstein in Marsilia and Pilularia^ and according to Juranyi in Salvinia, become 

 clothed only at a later period with cell-walls and thus form a tissue. The further 



Fig. 311. — Salvmia 7iatans (after Pringsheim). A longitudinal section through the macrospore, prothallium, and embryo 

 in the median line of the prothallium (X about 70), a wall of the sporangium, b epispore, c proper wall of the spore, e its 

 prolongation, rfthe diaphragm mentioned above which separates the prothallium from the spore-cavity, /r the prothallium 

 already broken through by the embryo,/, // its two first leaves, s the scutiform leaf; B an older seedling with the spore sp 

 and prothallium /r (X 20), a the caulicle, b the scutiform leaf, /, // first and second single leaves, L, L' aerial leaves of the 

 first whorl, tu submerged leaf of the first whorl. 



processes seem to me, according to the statements of Pringsheim, Hanstein, and 

 Hofmeister, compared with my own observations on Marsilia Salvairix, to be 

 briefly these : — the tissue of the prothallium is for a certain time completely enclosed 

 in the apical papilla of the macrospore, covered above by the epidermal layers 

 of the apex of the spore itself, and shut off from the spore-cavity below by a 

 wall of cellulose which is stretched across like a diaphragm and is attached at 

 the circumference to the endospore. By the further growth of the prothallium 

 the epidermal layers of the papilla are ruptured" abote, the dorsal part of the 

 prothallium projects into the funnel-shaped cavity which is left by the absence 

 of the thick episporial layer of the macrospore ; subsequently the diaphragm 



^ According to Aicangeli {loc. cit.) the prothallium is formed in Pihdaria by cell-division.] 



