A Study of Meadow-Crop Diseases in New York 107 



Culture 271 also produced another sector mutation of a reddish brown 

 color, which was designated 271 a. This was distinctly different from the 

 original culture. Subsequently in plate culture the white-island mutation, 

 271 d, produced a definite sector 271 da, which corresponded with the 

 original 271. Then the reddish brown mutation, 271 a, formed two addi- 

 tional sectors. One of these, 271 aa, was definitely pink, and the other 

 reverted to the 271 type. Still later a sector was found that formed heavy 

 rhizomorphic branches on cornmeal agar and was distinctly of a dark yel- 

 low green, 271 ab. It probably corresponds to the original form. One 

 other mutation from culture 271 arose. It was of a gray-green color 

 resembling very much culture 244. Cultures 272, 232, 231, and 251 were 

 then transferred to oat-agar plates, and the pink form corresponding with 

 271 aa arose from each. 



Using mycelium in lieu of spores, these so-called mutations were inocu- 

 lated into blue-grass to see whether they would retain their characteristics 

 after assuming a parasitic relationship. The most pathogenic mutation 

 was culture 271 da, the white-island form. It induced a violent case of 

 the disease within four days. Of less virulence were 271 aa, the pink 

 form, 271 ca, another white-island form similar to 271 da, and 271 ba 

 which resembled culture 244. 



Reisolation was successful with cultures 271 da, 271 ca, 271 ba, and 

 271 aa. The white islands of the first two, as well as the rapid growing 

 and gray characters of 271 ba, came out unchanged, but the pink form 

 of 271 aa was not recovered. 



It seems that mutation occurs in the species but that many of them are 

 relatively unstable, as evidenced by the reversion in culture. This seems 

 to be especially true of culture 271 aa, the pink form. Pink color is more 

 or less evident in lesions in nature, and tends to occur somewhat in all 

 the cultures, especially on oat agar. Pink color also tends to form in the 

 presence of contaminations, so that it is possibly a response to environ- 

 ment. Culture 271 aa arose as a direct sector and bred true except for 

 occasional reversions to the original condition. Although in reisolations 

 it was recovered as the original form, this does not prove that the mutation 

 271 aa is not a definite entity, since it might merely have reverted again 

 (o the original condition within the suscept. 



Reversion did not occur within the suscept in the case of the two white- 

 island mutations, 271 da and 271 ca, which arose independently. These 

 were reisolated without change. The tendency for white islands to form 

 in test-tube cultures of 231, 232, and 2f)l was also observed. These have 

 never been seen in culture 127 or culture 272. The white-island condition 

 seems to be as stable as, or more stable* than, what is called the typical 



condition. 



( ulture 271 ba, since it was reisolated unchanged, is probably also 

 relatively stable. The chief point of the mutation studies is that, of the 



