320 The Botanical Gazette. [June, 
in R. interruptum,; while in R. continuum the whole filament 
constitutes asinglesegment. In R. Americanum, on the other 
hand, we have a transitional form, in which the filament may 
consist of one or of several segments. The filaments them- 
selves are in all the species apparently simple, although in 
reality they consist of a succession of sympodial branches 
which arise below each sporangium after it has formed, the 
further upward growth of the branch causing the sporangium, 
though really terminal, to assume an apparently lateral po- 
sition. This type of filament is distinctly characteristic of the 
genus as limited above; and, although it occurs neither in 
Sapromyces nor in Araiospora, is identical with that which is 
Present in the ordinary sporangiferous filaments of Apod- 
achlya. The sporangia, as has just been mentioned, are terml- 
nal, and are typically solitary, although they may, especially in 
rather depauperate specimens, occur several together at the 
extremity of a filament. Several, however, often succeed 
one another at intervals on the same filament (fig. 5). The 
form of the sporangia, although in R. Americanum it shows 
a considerable degree of variation (figs. 7 and 15), tends, 1 
specimens that have developed under favorable conditions, 
assume the characteristic shape represented in fig. 6; and the 
same peculiarity is noticeable in the published figure of B. 
tnterruptum. 
The sporangia produce a comparatively small number of 
rather large zoospores, which are peculiar not only from their 
appearance, but from the manner in which they make thett 
escape. As the sporangium matures, a broad and conspiclr 
ous papilla is formed at its summit (fig. 7), and its wall is evl- 
dently double; for when the zoospores are ready to emerge; 
the outer wall splits around the base of this papilla which 1s 
then carried upwards at the extremity of the emergent fur 
of spores (fig. 8), remaining attached to the inner wa 
also surrounds the spore mass. The latter makes its ex!t . 
the form of a cylindrical column (fig. 9) which may re@ hi 
length equal to twice that of the sporangium before the st 
Surrounding wall becomes ruptured, usually at the side ai 
10), allowing the zoospores (fig. I1) to escape. s pt 
