228 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Harvard Laboratory on a bread culture which had been set for Rhizopus; 

 in 1889 Professor Thaxter in New Haven found the same species grow- 

 ing from a single spore in a van Tieghem cell culture of sterilized peach 

 decoction into which an inoculation had been made from roots infected 

 with peach yellows, and therefore the form was probably of soil origin, 

 and the material which is at present under cultivation was brought by 

 Professor Thaxter from New Haven, where it had been found by Prof. 

 W. C. Sturgis in a separation culture from earth. The writer has exam- 

 ined preparations of all this material, and also of that mentioned by Coker 

 ('03) as occurring spontaneously on a bread culture in the University of 

 North Carolina, and finds them to agree with Vuillemin's ('03") description 

 of Z. Moelleri. The species differs from Z. heterogamus chiefly in the 

 smaller size of the zygospores, and in the size and shape of the spores. 

 The zygospore formation is essentially the same. 

 The genus is obviously homothallic. 



Circinella umbellata van Tieghem and Le Monnier. 



Zygospores were found by Bainier ('03) during a warm period of 

 summer in a culture of fresh liquorice root placed on sphagnum in a cool 

 cellar. They arise on erect filaments upon which sporangia have not 

 been found. Plate VH, Figure 10, of Bainier's paper shows a zygo- 

 spore the suspensors of which connect with the branches of the same 

 hypha, suggesting the condition iu Sporodinia. If the figure is correct 

 in this respect the species belongs to the homothallic group. It will 

 have, however, the distinction of being the only known homothallic 

 form in which the sporangial stage is very common, while the zygospores 

 are extremely rare. The observation needs confirmation. [This is 

 especially true in view of the fact that since writing the above the writer 

 has found that a laboratory culture of this species will form imperfect 

 hybrids with a ( + ) strain, but is inactive toward a ( — ) strain. The 

 probability therefore of a heterothallic condition is very great.] 



Circinella nigra Bainier. 



This species of Bainier ('03) was found by him on horse dung. The 

 zygospores are similar to those of C. iimbeUata, and were found under 

 the same conditions. Plate VII, Figure 9, does not show enough of the 

 hyphae to indicate whether the progametes originate as in C. umbellata 

 or not. 



