CONTRIBUTIONS FROM THE CRYPTOGA.MIC LABORATORY 

 OF HARVARD UNIVERSITY. No. LXXXVII. 



XEAY DIMORPHOMYCETEAE. 

 By Roland Thaxter. 



Received March 6, 1920. Presented March 10, 1920. 



The Diniorphomyceteae, or unisexual Peyritschiellaceae, include 

 those unisexual forms among the Laboulbeniales in which the male 

 individual possesses one or more compomid antheridia, and include 

 the three genera Diviorphomyces, Dimcrornyces and Streblomyces, to 

 which a third, Polyandromyccs, is now added. In the present Con- 

 tribution I have given a list of all forms of this type which have been 

 published hitherto, and have added a large number from various 

 parts of the world which are new and in many cases very peculiar and 

 interesting. The greater number of the latter belong to Bimeromyces, 

 a genus which, like Rickia, has proved to be unexpectedly important 

 numerically, and to occur on a considerable variety of unrelated hosts 

 belonging to various families of the Coleoptera, Diptera, Orthoptera 

 and Acarini. 



A study of this large series of species, and a comparison of more 

 abundant material of Dimorphomyces than has been hitherto avail- 

 able, has served to make clear a number of doubtful points in regard 

 to homologies and development in these two genera, and has empha- 

 sized the fact that the two are much more closely related than I had 

 at first supposed. 



Typical forms of Dimorphomyces are clearly and easily distinguished 

 from normally developed species of Dimeromyces by the cell-relations 

 in the mature female, which, in the last mentioned genus, consists of a 

 primary axis of superposed cells, ^'ariable in number and terminated 

 by a more or less clearly distinguished terminal primary appendage. 

 In very young individuals this axis consists of a two-celled primary 

 receptacle, terminated bj^ the appendage. The basal and subbasal 

 cell of the primary receptacle, which are formed by the first division of 

 the basal spore-segment, are thus in contact one above the other; 



