Keene—Studies in Zygospore Formation. 
1203 
Zygospore Production 
Van Tieghem and Le Monnier (1873) were the first to report 
the zygospores of Phycomyces nitens and in their drawings in¬ 
dicate it as a homothallic form, as a result of which de Bary 
placed Phycomyces with Sporodinia. Van Tieghem’s first 
cultures were obtained from cochineal. He lost these but later 
obtained others from horse dung and again from cochineal. 
He failed to obtain zygospores when cultures were made from 
a single sporangium. Bainier (1883a) described the zygospores 
on horse dung mixed with flax-seed flour or soaked with flour, 
but he also realized the uncertainty of securing them. Later 
he found that if, during February or March, he started fresh 
cultures of horse dung he almost always obtained the zygospores 
within a short time. Zygospores have been reported in 
Phycomyces microsporus by Van Tieghem (1876) and in 
Phycomyces pirrotianus by Morini (1896). 
Until Blakeslee (1904) worked with Phycomyces nitens, the 
zygospores had not been reported in this country except in one 
case in which Thaxter, according to Blakeslee, described them 
in rabbit dung obtained from Daytona, Florida. 
The general facts of the morphology of conjugation in this 
form have been described by de Bary (1864), to whose ac¬ 
count Blakeslee (1904) has added a few points of interest. The 
majority of writers in describing the origin of the progametes 
say that the club-shaped progametes develop from the.hyphae, 
increase in size, come in contract and fuse. Blakeslee, how¬ 
ever, believes that the stimulus to development comes from con¬ 
tact; that they are “ zygotactic ’ ’ and that the progametes are 
normally adherent from the first. Blakeslee has devised an 
ingenious experiment to determine whether the origin of the 
progametes is dependent upon contact or upon chemical stimuli. 
The experiment has been repeated by the writer. A small bat¬ 
tery jar was lined with filter paper. Suspended by means of 
wire in the jar, one and one-fourth inches apart, were two 
small cheese cloth bags containing rye bread. Blakeslee soaked 
these with orange juice but the author found moistening well 
with water to be sufficient. An inch of water was put in the 
bottom of the jar and paper was tied over the top. This was 
then sterilized in the autoclave at 8 lbs. for 15 minutes. When 
cool one bag was inoculated with the plus strain and the other 
