1908] EDGERTON—ANTHRACNOSES 



393 



ploying the following media: potato agar, bean agar, potato agar 

 + 10 per cent, of glucor^e, potato agar+malic acid, and Elfving^s 

 nutrient solution. A number of sets of these cultures were carried 

 on during the year 1906-7. 



VARIABILITY OF FORMS 



A most remarkable fact was made evident by the study of the 

 cultures of the various forms. 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 collec- 

 tions on apples from Missouri and Illinois did not give exactly the 

 same characters, but the differences were sHght. 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 substratum 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 

 a? the northern form on apple. The forms on orchid, Coffea, and 

 Sarracenia, collected in the same greenhouse at the same time, were 

 not exactly ahke in culture media. They were similar in most re- 

 spects, but there wxre slight differences which would appear after 

 many transfers. 



What do all of these differences mean ? Miss Stoneman used these 

 m her description of species. Thom declares that in the genus Peni- 

 cillium all of the forms which show differences are distinct species. 

 However, he found that a PenicilUum would always give the same 

 characters on the same medium no matter how long it had been 

 grown on some other medium. A careful study was made of the 

 forms of Gloeosporium to see whether the same species, or rather the 

 same collection, would give the same characters generation after 

 generation. Some of the forms were studied for nearh^ two years. 

 Instead of the cultural characters coming true each time, a number 

 of interesting variations appeared, some of which are as follows. 



A GloeosDorium was collected on apples at ^lexico, New York. 



