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PROCEEDINGS OF THE AMERICAN ACADEMY. 



from a zygosporic culture. Those marked Normal were placed with 

 their covers on in a locker in the laboratory ; those marked Very Moist 

 were placed under a bell-jar on a plate lined with wet filter paper, and 

 in addition caps of damp filter jjaper were fitted over the uncovered 

 stenders ; those marked Dry had covers removed and were left in the 

 locker in a crystallizing dish loosely covered with a glass plate ; and those 

 marked Very Dry were uncovered and tightly closed in a glass jar 

 alongside with four stenders filled with calcium chloride. The series 

 showed, more distinctly than is indicated in the table, that increase of 

 moisture increases, and decrease of moisture decreases, the relative 

 abundance of zygospores on a given substratum. On favorable nutrients 

 in very moist air the sporangia were comparatively late in developing, 



