BLAKESLEE. — SEXUAL REPRODUCTION IN THE MUCORINEAE. 259 



In all the uut cultures, while occasionally one suspensor was larger 

 than the other, the ditFerence was not marked, but in cultures F and G 

 that on one side was regularly swollen to such an extent that its diame- 

 ter often equalled or exceeded that of the zygospore itself. In Tables 

 VII and VIII a transfer from the germination of a swollen suspensor 

 is represented by a capital letter with the addition of a Roman numeral, 

 as e. g. F II, and a transfer from an unswoUen suspensor by a small let- 

 ter, as, e. g., (2- Where an Arabic numeral is used with a capital, the 

 suspensors were equal in size. Transfers with the same numerical sub- 

 script came from opposite suspensors of the same zygospore. It will be 

 seen that in the two cultures together, eight out of nine of the swollen 

 suspensors taken were from a (— ) mycelium and five out of seven of 

 the smaller su>pensors belonged to a ( + ) mycelium. Not enough tests 

 were made to show whether so large a majority of the swollen suspensors 

 are normally (— ) as the figures would indicate ; but it is significant that 

 since this greater enlargement occurs also on the (-f-) side the swelling of 

 the suspensor cannot be considered as an indication of sexual differentia- 

 tion. G7 was taken from the germination of a young zygote whose walls 

 had just begun to darken, and whose suspensors had shrivelled. The 

 zygospores of Rhizopus, so far as is known, have never been germinated, 

 and in the present instance the word " zygospore " is not certainly appro- 

 priate, since whatever ripening process goes on in the zygote may not 

 have been completed in so short a time (two days from inoculation). 

 In culture F, the two strains are equally represented, while in G the 

 (— ) strain predominates six to two. 



It should be noted that in culture H, Table IX, the (— ) strain out- 

 numbered the (+) in the ratio of nineteen to one, while in culture C the 

 (-f-) strain outnumbered the (— ) in the ratio of eighteen to three ; and 

 it is further noticeable that the one (+) strain of the former, and the 

 three (— ) of the latter were all obtained from germinating suspensors. 

 This fact is of importance since it indicates that in this species the (+) 

 and (— ) strains are not distinguished from one another by any difference 

 in the luxuriance of their vegetative development, but that in ditlerent 

 cases one or the other may be predominant in that respect. 



The (+) and (— ) strains in these eight cultures (A to H) having been 

 separated and their character determined by means of contrasts with (+) 

 and ( — ) strains, chiefly of culture A, it was thought well to confirm the 

 results by using as a standard the strains obtained from the last culture 

 H. Accordingly, April 4, the (+) and (— ) strains from each of the 

 seven cultures A to G were contrasted respectively with the (— ) and (+) 



