163 



stages are known in many cases to arise sexually, it may be expected that 

 all perithecia represent sexual stages and a sexual act. The particular 

 forms with which I am working, that is H. No. 1 and derivatives, have 

 given no evidence of perithecial formation nor is it actually known that 

 they possess sexual stages. The presumption, however, is that they do, 

 so it is quite possible that my culture of H. No. 1 is derived from an asco- 

 spore, that is, may be the result of sexual parentage; and this sexual act 

 may have occurred in the not distant past. This is all hypothetical but it 

 appears to me to point to a possibility of an heterozygotic condition in 

 Helminthosporium, as well as in Glomerella as reported by Shear and 

 Wood (105) and in Coniothyrium as reported by Crabill (35), since so few 

 generations may have elapsed since fertilization that the heterozygosis 

 has not yet been eliminated. Such supposition in the case of Botrytis is 

 less tenable. 



It is suggestive to note here that Dastur (40) found variation a com- 

 mon phenomenon only in strains that were recently derived from perithecia ; 

 also that bud variation is more common in hybrids (East, 46). It is there- 

 fore thinkable that such of my strains of Helminthosporium as are saltating 

 are of recent ascigerous origin, while others that are not saltating (for 

 example H. ravenelii and H. geniculatum] are of distant ascigerous origin. 



If heterozygosis be eliminated from the discussion two other possible 

 explanations, suggested by Brierley regarding Botrytis, may be considered 

 here, namely, that of nuclear transference during mycelial anastomosis (Fig. 

 5, p. 104) or that of cytoplasmic contamination by such anastomosis. Evi- 

 dence on these questions, both from cytology of the mycelium and from 

 knowledge of sexuality, is quite lacking. Accepting none of the above 

 hypotheses, the saltation would be a mutation in the strictest sense of the 

 term. 



Reported mutations in Aspergillus and Penicillium described by 

 Arcichoyskij (2), Waterman (125), and Schiemann (100), and said to be in- 

 duced by environmental changes, are quite extensively discussed by 

 Brierley (28), who, repeating much of their work, concludes that when 

 the fungi showing these changes are returned to their original environ- 

 ment they resume their original aspect; that in fact the changes were 

 mere modifications due to environment. 



The cases reported by Brierley, Burgeff, Blakeslee, and Crabill, and 

 my own work reported herein, all based on single-spore culture and car- 

 ried under observation for sufficient time to give assurance of permanence, 

 constitute complete proof of the occurrence of the phenomenon of sud- 



