236 BOTANICAL GAZETTE [September 



enormous numbers, gregarious habits, wide distribution, over- 

 lapping generations, and usual habitats, to offer the most favorable 

 conditions for the development of a very large flora, but as yet only 



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two forms of Laboulbeniales have been found on them. Their 

 habit of cleaning themselves evidently does not interfere with the 

 successful propagation of such parasites, since several typical 

 genera and species are thus successfully attacked. That they 

 rarely become hosts, however, seems to be indicated by the fact 

 that, among the many that have been examined both by the writer 

 and by Professor Wheeler, whose attention has been called to this 

 matter for some years past, none have been found which appear 

 to be hosts for any forms except the common Laboulbenia fortni- 

 carutn of America, and the apparently equally common Rickia 

 Wasmanni of Europe. On the other hand, the most nondescript 

 type among those described below is an ant-parasite; although 

 its characteristics are not such as would have been expected to 

 makes its parasitism successful on any type of insect. 



Of the five genera herewith enumerated, three, including the 

 form on ants just mentioned, are very closely allied to well known* 

 genera of Hyphomycetes, the species of which are either saprophytes 

 or parasites on other plants; and did they not occur on living hosts, 

 might have been regarded as accidental saprophytes which had 

 developed after death; dead insect remains being, as is well known, 

 a very prolific source of such forms. Since, however, all the insects 

 examined in the present connection were collected while living, 

 directly into alcohol, and some were examined by the writer while 

 still alive, there can, it would seem, be no question as to the true 

 nature of the relation in these instances. Of the two remaining 

 genera, one comprises species also belonging to the Hyphomycetes, 

 but not closely related to any described types, while the other 

 seems to be more nearly related to the Chytridiales than to other 

 known organisms. 



In comparing the miscellaneous assemblage of forms which are 

 now known to live as external parasites on living insects, it is ol 

 interest to note that a great majority, at least, possess one 

 characteristic in common, namely a more or less clearly defined, 

 blackened footlike structure which serves both as an organ of 



