490 BOTANICAL GAZETTE [DECEMBER 
The gemmae of this form are perhaps a little more varied in 
shape than is the case with the species, but the shape of these organs 
is so variable in most species that they are of no value for syste- 
matic purposes. 
Had time permitted, it would have been interesting to cultivate 
this form for many generations in leucin-levulose solutions to deter- 
mine whether the vigorous production of oogonia which character- 
izes such forms of S. monoica as my 79¢ would be regained by this 
variety. 
The forms described in this paper are remarkable examples of 
the intimate dependence of the members of this group on external 
conditions. 
UNIVERSITY OF MICHIGAN 
EXPLANATION OF PLATE XXI 
Fics. 1-4.—Achlya Klebsiana. 
Fic. 1.—Portions of hyphae showing aborted sporangia; tip of one (at a) 
has sia died and would shortly have been pushed aside; about 85. 
1G. 2.—Short chain of gemmae showing how they break away and fall 
off; about 8s. 
IG. 3.—Oogonium with oospores; X 300. 
Fic. 4.—Young oogonium showing much branched antheridial hyphae; 
X 300 
FI Ics. 5—7.—Saprolegnia Kaufmanniana. 
Fic. 5.—Two oogonia in series; X 300. 
Fic. 6.—Intercalary oogonium; 00. 
Fic. 7.—Oogonium showing several antheridia; X 300. 
