BLAKESLEE. — SEXUAL REPRODUCTION IN THE MUCORINEAE. 255 



indicated in the table, it is apparent that they belong to strains which are 

 opposite to B.,, and by taking into account the fertile as well as the 

 infertile contrasts, it will be possible to arrange the cultures Bi to Bg on 

 one side in a column as belonging to the same strain in opposition to 

 Bj. and B^. By contrasting representatives from the two different strains 

 of this culture B, with the two strains A(+) and A(— ), it is seen that the 

 culture under discussion forms its zygospores through the interaction of 

 two strains which have the same value as those previously found in A, 

 and can accordingly be placed under the proper signs in the same column 

 with them. 



In the above table, Bi to Bs are cultures from transfers made in sepa- 

 rating these strains of nut culture B. In the columns marked Contrasts 

 is found their disposition, the mark (x) indicating that the cultures be- 

 tween which it is placed were inoculated side by side on flour paste. In 

 the columns marked Results of Contrasts is indicated whether zygospores 

 were present or absent as a result of these contrasts. In the columns 

 A(4-) and A(— ) under Strain Equivalents are arranged the cultures 

 from Nut Culture B according to their strain character as determined 

 by (+) and (— ) strains of A. 



Culture C was obtained on paste from nut shells from Mr. V. B. 

 Swett, Newton, Mass., and for some reason offered greater difficulties to 

 a separation of the strains. As seen from Table V, the two attempts, by 

 using pure transfers from the edge of the mycelium, gave only the single 

 (+) strain. Later, a large number of young zygo.«pores were dissected 

 out and laid separately on nutrient agar in Petri dishes. The following 

 day the suspensors on one side of many of the zygospores, and in three 

 instances those on both sides, had germinated, and made it possible to 

 obtain pure mycelial transfers from them. It should be here noted that iu 



