June 6, 1913] 



SCIENCE 



881 



The diiSculties in technique involved in fol- 

 lowing the sexual reactions in a thicket of 

 filaments have been overcome by growing the 

 heterogamic hermaphrodite W) in a Petri 

 dish between the (+) and ( — ) test strains 

 and cutting channels in the nutrient agar be- 

 tween the different growths. If the Petri dish 

 be then inverted, the growth of the reacting 

 filaments may be followed in mid air in the 

 channels. 



Only a single heterogamic species has been 

 found which will give reactions with both 

 (+) and ( — ) races and only a single dicecious 



the smaller c? gamete of the hermaphrodite. 

 The male gamete, which has been cut off from 

 a filament of the hermaphrodite at the stim- 

 ulus of contact with a (+) hypha, frequently 

 surrounds itself with a thick wall and as- 

 sumes the appearance of a resting azygospore, 

 as is shown at C. 



Of three other heterogamic hermaphrodites 

 investigated, two show a sexual reaction with 

 the (+) race only and one with the ( — ) race 

 only. It is difficult to interpret the sexual re- 

 action when shown with only one of the two 

 sexual races. 



JU 



Sestjal Reaction between a Heemapheoditic Mucoe and ( + ) and ( — ) Races 



OP A Dicecious Species 



Diagrammatic representation of a Petri dish culture showing a heterogamic hermaphroditic 

 mucor (<J) 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 reproduced nonsexually. 



1-6, stages in development of a hermaphroditic zygospore from unequal (? and ? gametes. 



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



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



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



species which will react with both male and 

 female gametes of this heterogamic hermaph- 

 rodite. These have accordingly been used in 

 making the tests shown in the accompanying 

 diagram. 



In the left hand channel at A in the dia- 

 gram, a filament from the ( — ) race is shown 

 giving a sexual reaction with the larger 2 

 gamete of the hermaphrodite, while in the 

 right-hand channel at B a filament of the (+) 

 race is figured, showing a sexual reaction with 



Judging from the behavior of the forms 

 figured in the diagram one would seem justi- 

 fied in considering the vegetatively more vig- 

 orous (+) race as female and the less vigor- 

 ous ( — ) race as male. 



The details upon which the conclusions in 

 the present article are based are being pub- 

 lished in another journal. The article itself 

 is a summary of a paper presented before the 

 Botanical Society of America, January 2, 

 1913. A. F. Blakeslee 



