1902] CLADOCHYTRIUM ALISMATIS 51 
The exospore breaks open in so regular a manner that it indicates 
some definite line of dehiscence, though no such appearance 
was made out on the mature sporangia before germination. In 
the meantime there is a change in the contents. So far as could 
be determined, the large central oil drop is gradually eaten away 
from its circumference inward until it disappears, or is really 
broken up into a large number of very small drops scattered 
through the protoplasm. This latter is now seen to be very 
faintly divided into areas, showing the formation of the zoo- 
Spores, in which the small oil drops frequently appear to be 
arranged more or less peripherally (fig. 38). These small oil 
drops gradually unite in each area to form the final large oil 
drop of each zoospore (jig. 39), and it is these oil drops more 
than any separating lines that indicate the number and position 
of the mature zoospores. While this has been going on, the 
papilla of dehiscence has been forming, though the sporangium 
is not always placed so that it can be seen. The papilla is best 
made out when examined in optical section at one side of the 
Ssporangium (fig. 39). It is usually a somewhat protruding area 
developed in the wall of the exposed endospore, and begins its 
dehiscence by the swelling of the cell wall which gradually 
extends inward as a hyaline area, due to the gelatinization of 
the wall. In some cases shortly before dehiscence this area 
seemed to be somewhat pitted, as is mentioned by Biisgen, 
perhaps allowing a greater flow of water into the sporangium, — 
forming the extended hyaline space in this vicinity. In one 
Sporangium, carefully watched, there could be seen no further - a : : 
Change at this point, the hyaline space now having ‘greatly — oe 
-€xtended inward, until there was a sudden m nt of the mass — 
bus zoospores, and one coming out into this space darted toward - 
= we Somewhat distended area in the endospore, and, apparently — 
forcing its way through, escaped, and was f oI wed, one by one = 
_ by the others, about a hundred, until all had gone. This place 
__ Of escape usually shows a polygonal opening with a few cracks — 
| Stading from the angles (fgig7)- 
€ zoospores are somewhat variable in si ze and vary from 
