BLAKESLEE. — SEXUAL REPRODUCTION IN THE MUCORINEAE. 241 



on Agaricus campestris from his several findings of the fungus in the 

 autumn, when be succeeded in obtaining them in the spring on the same 

 substratum. 



Chaetocladium Jonesii Fresenius. 



According to Brefeld ('81j the zygospores appear in serial cultures 

 after a short period of cultivation. Neither the description nor the 

 figures indicate the hyphal connections of the suspensors. 



Chaetocladium Brefeldii van Tieghem and Le Monnier. 



Only once from among a large number of spontaneous and artificial 

 cultures which Brefeld ('72; carried on continuously for a long time did 

 the zygospores of this fungus appear, and then on a spontaneous horse 

 dung culture. The Mucor was scant, but the Chaetocladium was very 

 luxuriant, producing side by side conidiophores and yellow zygospores, 

 the genetic connections between which could be easily made out. Brefeld 

 distinctly states that he was unable to discover zygophoric branches 

 arising near each other from a single hypha, although they were found 

 adjacent in great numbers and in continuity with conidiophores. Though 

 attempts were often repeated, zygospores were never obtained from the 

 sowings of spores produced from germinating zygospores. 



Pale and dark zygospores of this species were also obtained by Bainier 

 ('84), the color corresponding in either case to temperature differences in 

 the cultures. Nothing is said about the conditions accompanying zygo- 

 spore formation, and the figures add no information on this point. It is 

 possible, as A. Fischer ('92. p. 287) suggests, that Bainier may have had 

 the zygospores of two species mixed in his cultures. 



Schroter ('86^j reports that this species is rather frequently found 

 in Breslau with zygospores, and Leger ("96} also mentions their 

 occurrence. 



In 1902 the writer found zygospores of this species on horse dung sent 

 from Berlin. They had developed before reaching the laboratory, and it 

 was then impossible to induce further formation. In the spring of 1903 

 Professor Thaxter obtained zygospores from sowings on sterilized horse 

 dung. The Chaetocladium came from a tube culture, and the Mucor host 

 was taken from a gross culture. This does not render impossible a 

 heterothallic condition, for a complementary strain may have been intro- 

 duced with the host, and even the tube culture may have contained two 

 strains which were prevented from forming zygospores by unfavorable 

 nutrient conditions. 



VOL. XL. — 16 



