Saprolegnia 75 
SAPROLEGNIA. 
F. M. ANDREWS. 
In the Saprolegnieae the sporangium is a somewhat club-shaped 
cylinder which sooner or later is cut off from the rest of the filamentous 
structure of the plant by a transverse wall. This sporangium is of 
varying length, but ordinarily its length exceeds its greatest diameter 
from four to ten times. Aside from the presence of a transverse wall, 
one thing that attracts the attention of the observer is the much more 
grumous or densely granular nature of the protoplasm. This latter 
condition is generally quite conspicuous in parts or organs that are or 
are becoming reproductive centers of various kinds. 
This dense protoplasm of. the future zodsporangium finally divides 
into more or less polygonal areas. Sometimes these areas show a some- 
what rounded appearance and the transverse wall which confines them 
to the end of the filament is slightly rounded or arched toward the apex. 
The zodsporangium opens at the end and preparatory changes in the 
contents lead to the final expulsion of the zodspores. There are questions, 
however, concerning this process which are still unanswered and which 
deserve attention. 
The transverse wall above referred to is not always straight at 
first but may become curved at a later period, in some members of the 
group Saprolegnieae, as in some cases in Saprolegnia and Achlya. In 
the latter, especially, it is often straight at first or slightly curved from 
the tip, whereas later it is curved apically, particularly when the zo- 
ospores are escaping. At this time, and even before at times, the thin 
transverse wall is sometimes curved apically due to greater hydrostatic 
pressure back of the zodsporangium, notwithstanding the considerable 
swelling of the contents of the zodsporangium. This curving outward 
of the transverse wall frequently occurs at first whether a new zo- 
osporangium is to be produced or not in the hull of the old zodsporan- 
gium. 
“The distinguishing mark of Saprolegnia,” says de Bary,’ “is that 
the spores are in the motile state as they issue from the sporangium, 
and that the branch of the thallus which bears the sporangium grows 
through it when it has discharged its spores.” In Achlya a branch is 
formed laterally and beneath the transverse wall. This new branch 
becomes the zodsporangium after development. 
An illustration of the apically directed or curved transverse wall 
is also to be seen in Saprolegnia Thuretis at times, as illustrated by 
Nathansohn,* which is due to greater hydrostatic pressure probably 
from the first in the main filament than in the zodsporangium, not- 
withstanding the swelling process in the latter. This wall is not form- 
1de Bary, A., Comparative Morphology and Biology of the Fungi, Mycetozoa and 
Bacteria, 1887, p. 148. 
? Nathansohn, A., Allegemine Botanik, 1912, p. 303. 
