314 PROCEEDINGS OF THE AMERICAN ACADEMY. 



group together in two opposite series the strains of all the heterothallic 

 forms under cultivation. 



(12) When thus grouped the ( — ) or less luxuriant strains will be in 

 one series while the (+) or more luxuriant will be in the other. 



(13) From the foregoing observations it may be concluded, — 



(a) that the formation of zygospores is a sexual process ; 



(b) that the mycelium of a homothallic species is bisexual ; 



(c) while the mycelium of a heterothallic species is unisexual ; 



(d) and further, that in the (+) and (— ) series of the hetero- 



thallic group are represented the two sexes. 

 A preliminary summary of the results of the present paper has been 

 given by the writer ('04) in Science, June 3, 1904. 



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 Bainier, G. 



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