FUNGI IMPEK1 !( II 



331 



such cross-inoculation experiments as have been made indicate 

 that many species, at least, are not closely restricted as to hosts, 

 and one form might be the cause of disease in a variety of plants. 

 It has seemed to be a group which would well reward comparative 

 study in artificial culture, and advantage has been taken of this 

 by Stoneman, 1 Kdgerton, 1 and others. With particular reference 

 to species of one type, those which may represent stages of the 

 pyrenomycetous genus Glomerella, Edgerton says in part : 



There are many closely related forms and species and all are variable. 

 They vary under artificial cultivation and probably under natural conditions. 

 Many are similar enough to be considered the same species, but evidence suffi- 

 cient to warrant bringing together the related forms as one species is generally 

 lacking. 



In the determination of a species too much dependence cannot be placed 

 upon cultural characters alone. These characters are useful, but are not suffi- 

 ciently constant to justify exclusive use. 



Thus far species of Glceosporium seem to have been definitely 

 connected with three genera of Ascomycetes, as follows : Pseudope- 



ziza, Glomerella, and Gno- ^___ 



monia, the imperfect stages 

 of which were respectively 

 known as Glceosporium 

 Ribis (Lib.) Mont. & 

 Desm., Glceosporium frnc- 

 tigcnmn Berk., and Glceo- 

 sporium nerviseqtimn Sacc. 

 The imperfect form is in- 

 variably the important 

 stage from the phytopatho- 

 logical point of view. The 

 effects upon the hosts are 



FIG. 158. Gur.osi'oRit M ON LEAVES OF 

 \ NORWAY MAPLE 



in every way comparable 

 to those resulting from the 

 attacks of various species 



placed in the closely related genus Colletotrichum previously de- 

 scribed. In fact, some species of Glceosporium occasionally pro- 

 duce a small number of setae under special conditions. Upon the 



1 See Bitter Rot of the Apple, p. 271. 



