292 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



where there was presumably a greater humidity' in the confined air and 

 in which zygospores were also formed. 



Further to test the effect of humidity on the type of fructification, a 

 series of cultures was made from the material above mentioned under 

 conditions which were made to correspond to those described by Falck 

 in connection with his experiments. On March 1 7, discs of bread were 

 sterilized dry in stender dishes, soaked, five of them with sterilized 

 water and five with equal amounts of dilute prune decoction, and, after 

 having been subjected for eight minutes to steam at 100° C, were in- 

 oculated with drops of water containing spore material. The stenders 

 were left in a culture drawer until March 20, when a vegetative growth 

 was first visible. One of the prune juice cultures showed young zygo- 

 spores in process of formation, but in none of the other stenders had the 

 growth advanced further than a production of the mycelium. The cul- 

 tures were disposed according to the varying degrees of atmospheric 

 moisture indicated in Table XI. 



Air very moist. 

 Cultures open in moist 

 chamber with caps of wet 

 filter paper. 



Ail- normal. 

 Cultures closed on labor- 

 atory table. 



Air dry. 

 Cultures open on labor- 

 atory table. 



Air very dry. 

 Cultures open in a sealed 

 vessel containing calcium 

 chloride. 



TABLE XI. 



Plain Bread. 



Only zygs. 



Only zygs. 



Only sporangia on surface, 

 zygs. on sides below. 



Only sporangia. 



Prune Bread. 



Zygs. with tuft of 

 sporangia. 



Only zygs. 



Only sporangia on 

 surface, zygs. on 

 sides "below. 



Only sporangia on 

 surface; zygs. 

 and a z y g s . on 

 sides below. 



In general, the series demonstrates that increased relative moisture is 

 a condition favoring formation of zygospores, while decreased relative 

 moisture is a condition favoring the formation of sporangia. With the 

 exception of the tuft of sporangia in the prune bread culture in very 

 moist air, none of the cultures in normal, nor those in very moist air, 

 produced any sporangia, while in the cultures in dry, and in very dry, 

 air sporangia predominated. It was observed that the stenders in the 



