SEXUAL REACTIONS BETWEEN MUCORS. 



93 



then inverted, the growth of the reacting filaments may be 

 followed in mid air in the channels, under the low power ob- 

 jective. 



Absidia spinosa is the only heterogamic species which has 

 been found to give reactions with both ( + ) and ( ) races and 

 Mucor V. is the only dioecious form that will react with both 

 male and female gametes of A. spinosa. These have accordingly 

 been most extensively employed in making the tests shown in 

 the accompanying diagram. 



In the left-hand channel at A in the diagram, a filament from 

 the ( ) race is shown giving a sexual reaction with the larger 

 9 gamete of the hermaphrodite, while in the right-hand channel 

 at B a filament of the ( + ) race is figured, showing asexual re- 

 action with the smaller cf gamete of the hermaphrodite. The 



Diagrammatic representation of a Petri dish culture showing a heterogamic 

 hermaphroditic mucor ( S ) in the center separated by channels on either side from 

 the (+) and ( ) races, respectively, of a dioecious species. 



Sp., Sporangia containing spores by means of which the plant may be repro- 

 duced nonsexually. 



i6, stages in development of a hermaphroditic zygospore from unequal male 

 and female gametes. 



A, sexual reaction between a ( ) filament and female gamete. 



B, sexual reaction between a (+) filament and male gamete. 



C, a male azygospore formed at stimulus of contact with a (+) filament. 



male gamete, which has been cut off from a filament of the 

 hermaphrodite at the stimulus of contact with a (-f) hypha, 

 frequently surrounds itself with a thick wall and assumes the 

 appearance of a resting azygospore, as is shown at C. 



Figs. 20-24, Plate II., are drawings from living material. 

 The female gamete of A. spinosa is recognized not only by its 



