BLAKESLEE. — SEXUAL RErRODUCTION IN THE MUCORINEAE. 269 



hoped that a similar condition might be found in Rhizopns. The unequal 

 Rwelling of the suspensors has been already referred to as a variable 

 circumstance independent of the (+) or ( — ) character of the strains 

 contrasted, yet swollen suspensors are almost constantly present in 

 contrasts between certain (+) and ( — ) strains, while they are as con- 

 stantly absent in conti-asts between others. In addition, conditions of 

 the substratum unfavorable to zygospore formatiim seem to be a hindrance 

 to suspensor enlargement. Both suspensors may remain small or both 

 may enlarge, and the explanation which naturally suggests itself is that 

 the swollen suspensor is connected with the hypha which happens to 

 contain an excess of protoplasm. Whenever a number of zygospores have 

 been carefully dissected out, the swollen suspensors have always been 

 observed to have the same h^phal connections and are often seen to 

 arise from the larger hypha. In contrast to the opposite filament which, 

 together with the smaller suspensor connected with it, is generally soon 

 empty, the larger suspensor seems to furnish most of the nourishment 

 to the growing zygospore, and it is not unusual to find a young zygospore 

 associated with a suspensor greater than itself and acting as a reservoir 

 of dense protoplasm which it gives up as the zygospore matures. That, 

 however, the difference in size does not correspond to an inherent dif- 

 ference in the (+) and (— ) strains as such is shown by its inconstant 

 occurrence as well as by such results as were obtained by culture F 

 (p. 259), in which germinations of both larger and smaller suspensors 

 gave rise to (-f ) and (— ) strains indiscriminately. 



Although van Tieghem ('75) was unable to confirm de Bary's view, 

 that there is a relationship between the size of the gametes and that of 

 the suspensors, he considers the inequality in the size of the gametes an 

 indication of a sexual differentiation. The difference in vigor of the two 

 sides is often indicated by an inequality in the progametes ; and in cultures 

 where unequal swellings of the suspensors is marked, the difference in 

 their size is generally evident as soon as the gametes are cut off. Though 

 in the material examined the smaller gamete was in a majority of cases 

 adjacent to the enlarged suspensor, the reverse condition has been ob- 

 served. From Plate I, Figure 15, it will be seen that the size of the 

 gamete can be of no sexual significance in this species. The connected 

 suspensors and their gametes belong obviously to the same strain, and 

 consequently in the two cases where the gametes are unequal the smaller 

 gametes are seen to belong to the 9pposite strains. This figure is a 

 camera drawing from a preparation taken from a culture where tlie 

 suspensors were approximately equal in size. 



