GROUP I. THALLOPHYTA: FUNGI: ZYGOMYCETES. 289 



gans. In the genus Mortierella (so far as is known), the zygospore does not 

 actually germinate itself, but a number of sporangia spring from the hyphal 

 investment surrounding it. 



The mycelium, when under unfavourable conditions, gives rise to unicellular 

 gemmse, either chlamydogonidia or oidium-cells : the latter multiply by gemma- 

 tion in a yeast-like manner (e.g. Mucor racemosus) and, like Yeast, have the power 

 of causing alcoholic fermentation ; this takes place especially when the hyph 

 are immersed in liquid. The hyphas become segmented into a row of cells by the 

 formation of transverse septa, and the cells then separate and become free. 

 The chlamydogonidia are thick- walled and large; the oidium-cells are smaller 

 and thin-walled (see p. 274). 



The typical life-history presents an obvious alternation of generations. The 

 plant is the gametophyte, inasmuch as it either actually produces sexual organs 

 (when it is an actual gametophyte), or, though capable of producing sexual organs 

 it does not do so, owing to external conditions (when it is a potential gameto- 

 phyte) ; the gametophyte reproduces its like by means of the gonidia. The 

 promycelium, derived from the zygospore, is the sporophyte, inasmuch as it is 

 incapable of producing sexual organs. In some cases, however, the zygospore 

 gives rise to the mycelium bearing sexual organs. 



The Mucorinse may be sub-divided as follows : 



Sub-Order A Sporangiophorae : gonidia developed inside a gonidangium. 

 Fam. 1. Mucoracece : the gonidangium has a columella ; the aygospore is 

 naked or invested only by a few loose hyphas ; principal genera, 

 Mucor, Phycomyces, Sporodinia, Thamnidium, Pilobolus. 

 Fam. 2. Mortierellea : the gonidangium has no columella ; the zygospore 

 is invested by a compact mass of hyphas : Mortierella. 



Sub-Order B. Conidiophorse : gonidia formed by abstriction from sterigmata. 

 Fam. 1. CluEtocladiece : gonidia developed singly on the sterigma ; the 



gametophores are straight : Chastocladium. 



Fam. 2. Cephalideae : several gonidia developed from each sterigma ; the 

 gametophores are curved : Piptocephalis, Syncephalis. 



The Mortierelleae, Chastocladieae, and Cephalideae, are for the most part 

 parasitic on various Mucoraceae. 



OrderS. Entomophthoraceae. Body an incompletely septate mycelium ; 

 reproduction by means of non-motile gouidia, and by zygospores formed by 

 conjugation ; mostly parasitic on insects. 



The mycelium ramifies in the body of the insect, and in most cases produces 

 simple gonidiophores which, after the death of the insect, project from its body, 

 each forming a single gonidium by abstriction at its apex ; the gonidium is 

 thrown off to a considerable distance, so that the body of the insect becomes 

 surrounded by a halo of gonidia. This may commonly be seen in the case of 

 flies in the autumn, which are frequently attacked by a member of this order 

 (Entomophthora Muscce) and remain sticking to window-panes. The gonidium, 

 on germination, puts out a hypha which penetrates into the body of another 

 insect ; this hypha may either grow directly into a mycelium in the body of the 

 insect (*?.</. Entomophthora radicans, ovispora, curvispora), or it may produce 

 by abstriction a number of gonidia which may multiply by budding in a yeast- 

 like manner within the body of the insect, and it is these which produce my- 



V. S. B. U 



