386 



BOTANY 



PAllT II 



Within the group of the Zygomycetes a reduction of sexuality can be seen. 

 Thus, in the case of certain Mucorineae, although the conjugating hyphae meet in 

 pairs, no fusion takes place, and their terminal cells become converted directly 

 into spores, which arc termed azygosfores. In other forms again, liyphae 

 producing azygospores are developed, but remain solitary, and do not, as in the 

 preceding case, come into contact with similar hyphae. There are also many 



species in which the formation of 

 zygospores is infrequent. 



Both the size and number of 

 spores produced in the sjiorangia 

 of Mucitr Miardo are subject to 

 variation. The sporangia of the 

 genus Thamnidium are, on the 

 other hand, regularly dimorphic, 

 and a large sporangium contain- 

 ing many spores is formed at 

 the end of the main axis of the 

 sporangiojihore, while numerous 

 small sporangia, having but few 



■a 



Fig. 315. — Mucor Muccdo. Different stages in the 

 formation and germination of tlie zygospore, 

 i, Two conjugating branches in contact ; S, 

 septation of the conjugating cells («) from the 

 suspensors (b) ; 3, more advancf^d stage, the 

 conjugating cells (a) are still distinct from one 

 another : the warty thickenings of their walls 

 have commenced to form ; A, ripe zygospore ('/) 

 between the suspensors (ri); -'', geniiinating 

 zygospore with a germ-tube bearing a sjioran- 

 gium. (After Brefeld, 1-4 x 225, 5 x circa liO, 

 from V. Tavei,, I'ihe.) 



Fia. 316. — Kmjmsa muscae. .^, Hypha 

 from the body of a fly. i>, Young 

 conidiophore arising from the 

 mycelium and projecting from the 

 body of the insect. C, Formation 

 of the conidium into which the 

 7iumerons nuclei have passed from 

 the conidiophore. (.\fter Olive, 

 X 540.) 



spores (sporangioles), are produced by its verlicillately blanching lateral axes. 

 The sporangia may at times develop only a single spore, as the result of certain 

 conditions of food -supply, and in this way assume the cliaracter of conidia. 

 This dimorphism is even more comi^lete in the tropical genus Choa^iephora. In 

 this case, in addition to large sporangia, conidia are jiroduced on special cuni- 

 diophores. There are, finally. Zygomycetes («.</. Chaetodadiuui) whose only 



