GKOUP I. THALLOPHYTA : FUNGI : ZYGOMYCETES. 



287 



to so many other different forms. It is allied, on tbe one hand, by the simple 

 Myxochytridineee to the Monadinese, and thus also to the rest of the Myxomy- 

 cetes. On the other hand it is allied to the simple Oomycetous Phycomycetes, 

 the Ancylistaceoe, a group which is sometimes actually included in the Chytri- 

 diaceaa ; and, again, through such forms as the CladoclrytrieaB, to the Ustila- 

 gineae. 



Order 2. Mucorinse. Body an unseptate mycelium, septa being only 

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

 tion by gonidia and spores, and by zygospores formed by conjugation ; mostly 

 saprophytic, but some are parasitic on other Fungi. 



The mycelium ramifies in the substratum (Fig. 199). The asexual reproduc- 

 tive organs are developed as simple gonidiophores which grow erect into the air. 

 In the Mucoraceae the simple gonidiophores are unbranched, and each bears 



FIG. 199. Mucor Mucedo : m a mycelium bearing a simple gonidiophore with a terminal 

 gonidangitim s ; S a gonidan^ium much magnified ; t the end of the gouidiophore dilated 

 into the columella c; w the wall of the gonidangium; sp the gonidia; z zygospore formed 

 by the fusion of the contents of two gametangia. 



at its apex a single gonidangium ; the gonidiophore projects into the cavity 

 of the gonidangium as a columella (Fig. 199). In the Chaatocladieaa and the 

 Piptocephalidese the gonidiophore is branched and more or less septate ; it 

 produces a number of gonidia by abstriction from the tips of its branches. On 

 germination, the gonidium gives rise to a mycelium similar to that from which 

 it was derived. 



The gametophores are short swollen hypha? ; 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 hypha3 

 come into contact at their tips ; the walls of the two gametangia are absorbed 

 at the point of contact ; the protoplasmic contents (gametes) of the gametaugia 



