GROUP I. THALLOPHYTA : FUNGI. 



285 



with a membrane and go through a resting-stage as microcysts ; or 

 the whole or part of a plasmodium may do the same as a sclerotium. 



Sub-Class III. PHYCOMYCETES. Section A : 'Zygomycetes. 



The section Zygomycetes includes several orders of which, how- 

 ever, only the characteristic order Mucorinse will be considered. 



Order Mucorinae. Body an unseptate mycelium, septa being only 

 developed in connection with the formation of reproductive organs ; repro- 

 duction by spores, and by zygospores formed by conjugation; mostly 

 saprophytic, but some are parasitic on other Fungi. 



The mycelium ramifies in the substratum (Fig. 165). The asexual repro- 

 ductive organs are developed as simple sporophores which grow erect into 

 the air. In the Mucoracese the simple sporophores are unbranched, and each 



FIG. 165. Mucor Mucedo : m a mycelium bearing a simple sporophore with a terminal 

 sporangium s ; S a sporangium much magnified; t the end of the sporophore dilated into 

 the columella c ; ic the wall of the sporangium ; gp the spores ; z zygospore formed by the 

 fusion of the contents of two gametangia. 



bears at its apex a single sporangium ; the sporophore projects into the 

 cavity of the sporangium as a columella (Fig. 165). In the Chaetocladieae 

 and the Piptocephalideae the sporophore is branched and more or less 

 septate ; it produces a number of spores by abstriction from the tips of its 

 branches. On germination, the spore gives rise to a mycelium similar to 

 that from which it was derived. 



The gametophores are short swollen hyphse; by the formation of a 

 septum near the tip of the gametophore, a terminal cell is produced, which 

 is the sexual organ or gametangium; the protoplasmic contents of the 

 gametangium constitute the gamete. Two gametophores from adjacent 

 vegetative hyphse come into contact at their tips ; the walls of the two 



