160 



BOTANY 



the case with the wall of the stalk of the sporangium. At maturity the outer mem- 

 brane of the sporangium, which in many Mucoracese contains minute calcareous 

 bodies, becomes mucilaginous, and on being wet, dissolves and sets free the 

 ripe spores, which germinate promptly if placed in water ; and if supplied with 

 proper nutriment they grow with great rapidity, and soon develop a new 

 mycelium. 



Pilobolus. In the genus Pilobolus (Fig. 125, B, C), which grows 

 abundantly upon stable manure, the stout sporangiophores are much 

 distended just below the sporangium. When the latter is ripe, a 

 ring-shaped break occurs around its base, and the fluid contained in 

 the distended bulb below the sporangium is suddenly liberated with 

 such force as to project the sporangium to a long distance. Where 



FIG. 124. JUucur st^lvidfer. Development of zygospore. A-B, X 225. 

 C-E, X about 90. 



the plants are grown under a bell-jar, its inner surface soon appears 

 dotted with the adherent sporangia thrown off in this way. 



In other genera, e.g. Chsetocladium and Syncephalis, the spores are 

 conidia, somewhat like those of Albugo. They may be borne singly 

 or in chains (Fig. 125, A). 



Sexual Reproduction. Zygospores, formed from the union of two cells 

 borne at the end of short branches, are found in many of the Mucorinese, but 

 as a rule they are of somewhat rare occurrence. In Mucor stolonifer (Fig. 124) 

 the process begins by the sending out of short branches from neighboring hy- 

 phae, which grow toward each other and finally come into contact. The proto- 

 plasm in these branches, which become much enlarged, is very dense and 

 granular, and from the end of each a cell is cut off which forms one of the 



