98 



ZYGOMYCETES. 



, The Mucoracese, in addition to the chlamydospores and oidia, 

 have a more normal and ordinary method of reproduction; viz. r 

 by spores which are formed without any sexual act. Mucor has- 

 round sporangia ; from the mycelium one or more long branches,, 

 sometimes several centimetres in length, grow vertically into the 

 air ; the apex swells (Figs. 78, 80) into a sphere which soon 

 becomes separated from its stalk by a transverse wall ; in the 



interior of this sphere (spor- 

 angium) a number 1 of spores are 

 formed which eventually are set 

 free by the rupture of the wall. 

 The transverse wall protrudes 

 into the sporangium and forms 

 the well-known columella (Fig. 

 80 d, e). The formation of 

 spores takes place in various 

 ways among the different 

 genera. 



SEXUAL EEPEODUCTION by conjugation takes place in the follow- 

 ing manner. The ends of two hyphte meet (Fig. 81) and become 

 more or less club-shaped ; the ends of each of these are cut off 

 by a cell- wall, and two new small cells (Fig. 81 A) are thus 

 .formed, these coalesce and give rise to a new cell which becomes 

 the very thick- walled zygote (zygospore), and germinates after a 



PIG. 79. Chlamydospores of CTiZamydo* 

 mucor racemosus ( x 375 times.) 



FIG. 80. JJfitcor mucedo : a a spore commencing to germinate ( x 300 times); b a germi- 

 nating spore which has formed a germ-tube from each end ( x 300 times) ; c the apex of a 

 young sporangium before the formation of spores has commenced; the stalk is protruded 

 in the sp orangium in the form of a column : on the wall of the sporangium is found a very 

 fine incrustation of lime in the form of thorn-like projections ; d a sporangium in which 

 the formation of spores has commenced ; e a sporangium, the wall of which is ruptured,, 

 leaving a remnant attached to the base of the columella as a small collar. A few spores are- 

 seen still adhering to the columella. 



