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tion. The very large mass of corroborating positive evidence, though 

 really conclusive only when based on single-organism cultures, makes it 

 extremely probable, to say , the least, that such saltations or mutations 

 do occur in these groups. 



Among the Eumycetes several examples occur of what appears to 

 be saltation. Edgerton (50) in 1908, writing of Glomerella rufomaculans, 

 states that "of the more than thirty collections studied from over twenty 

 hosts, with less than a half-dozen exceptions all gave at least slightly 

 different characters. Even the two collections on apples from Missouri 

 and Illinois did not give exactly the same characters, but the differences 

 were slight. The two collections from apples in the north, however, gave 

 entirely distinct characters from the more southern forms on the same 

 host. The southern form, especially on sugar medium, was characterized 

 by very rapid growth and a very dark greenish-black color of the sub- 

 stratum and aerial hyphae; while the northern form grew more slowly 

 and had very little dark color. Generally in the latter the aerial hyphae 

 were colored pink from the profuse development of conidia. Even the 

 form on quince collected in New York did not give the same characters 

 as the northern form on apple. The forms on orchid, Coffea, and Sar- 

 racenia, collected in the same greenhouse at the same time, were not 

 exactly alike in culture media." 



Other examples were given by Edgerton (50) in 1908 of what appears 

 to be the same phenomenon as that under discussion here, but as there 

 is no evidence that he worked with single-conidia cultures* his apparent 

 variations may have been due though it is highly improbable to segre- 

 gation of elementary species. His general conclusion follows: "The only 

 explanation of the phenomenon is that one or more individuals of the 

 original form changed quite suddenly their course of development under 

 cultural conditions. It is undoubtedly a Gloeosporium of the Glomerella 

 type, with the development of the perithecia considerably different from 

 other known forms. Mutations, so far as is known by the writer, have 

 not previously been recorded among fungi, but the form just described 

 seems to be one without question." 



Here, too, should be mentioned the plus and minus strains of Glom- 

 erella studied and reported on by Edgerton (51) from single-conidia cul- 

 tures, though this may represent a differentiation of sexes rather than of 

 races. He gives several citations which indicate that other workers have 



*In a personal letter dated February 7, 1921, he writes regarding this as follows: "All of the cultures 

 that I used in that work were obtained by the dilution plate method and presumably came from single spores." 



