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 Prothalliufn 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 Pihdaria^ and according to Juranyi in Salvinia, become 
clothed only at a later period with cell-walls and thus form a tissue. The further 
Fig. 2^i.—Saim}im natans (after Priiigsheiin). A longitudinal section through the niacrospcre, 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, fits 
prolongation, d the 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 (X20), a the caulicle, b the scutiform leaf, /, //first and second single leaves, Z, /.' aerial leaves of the 
first whorl, -w 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' above, 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 Arcangeli (/oc. cit?) the prothallium is formed in Pilnlaria by cell-division.] 
