BLAKESLEE. — SEXUAL IlEl'UODUCTION IN THE MUCORINEAE. 223 



According to Rainier ('83'', p. 342), if in March and April dried horse 

 dung be examined from a beaten road, it is not rare to find zygospores 

 in the interior, and if laboratory cultures of fresh horse dung arranged in 

 a thin layer be sown with this same M. Mucedo, one easily obtains a large 

 (juantity of zygospores during this period. Zygospores were obtained 

 many times in January on Bainier's alcoholic decoction of prunes. lu 

 his £tude, Bainier ('82) speaks of the zygospores occurring in the dung 

 when the spores of the species are abundant in the horse's food. 



Leo-er ('96, p. 59) obtained the zygospores on horse dung when the 

 substratum had begun to dry; Vuillemin ('82''), used zygospores of 

 this form for the study of the zygosporic membrane; and Spegazzini 

 ('91) mentions zygospores in his description of this species from Argen- 

 tine. The occurrence of zygospores of M. Mucedo has not been infre- 

 quent on dung cultures in tlie Harvard Laboratory during the past fifteen 

 years. 



The species is heterothallic. 



Mueor racemosus Fresenius. 

 Bainier ('82) found zygospores of this species on moist bread, horse 

 dunof, and plaster wet with a solution of glucose, and in a later paper 

 (83'', p. 347) he says : '' If Macor racemosus be grown in cell cultures 

 in alcoholic decoction of plums during December, January, and Febru- 

 ary, one infallibly obtains an exaggerated production of zygospores. . . 

 The air was often renewed in the cultures, hence increase or decrease of 

 oxygen can be only an accessory factor." He further remarks that 

 " Since the plant grew on a liquid and in a nearly saturated atmosphere, 

 dryness cannot be a general cause of zygospore production. In solution 

 of peptone or extract of malt zygospores are rare, while in solution of 

 glucose only chlamydospores and sporangia occur." In the plates ac- 

 companying this paper (Plate XVII, Figure G ; Plate XVIII, Figure 

 0) as many as three zygospores are figured arranged in a scalariforai 

 fashion one above the other between two adjacent hyphae. No figures 

 showing a homothallic condition are given, and probably such a condi- 

 tion does not exist. Under this species Bainier includes six forms which 

 differ in branching, size of sporangia, and relation to nutrients. One of 

 these gave zygospores only exceptionally. Being of the opinion that 

 polymorphism may exist in this species Bainier considers these as varie- 

 ties. It is for this reason, perhaps, that the zygospores which he figures 

 as belonging to M. racemosus do not correspond and show at least three 

 distinct types (Bainier, '82, Plate I, Figure 1 1 ; '83% Plate V, Figure 



