l8o MORPHOLOGY. 



thread of the mycelium. In other cases large portions of the threads of the 

 m3xelium may separate into chains of cells. Both these kinds of cells are 



Fig. 194. 

 A mucor (Rhizopus nigricans) ; at left nearly mature sporangium with columella showing 

 witliin; in the middle is ruptured sporangium with some of the gonidia clinging to the colu- 

 mella ; at riglit two ruptured sporangia with everted columella. 



capable of growinir and forming the mycelium again. They are sometimes 

 called chlaniydosporvs. 



890a. The Mucorinete according to their manner of zygospore formation 

 are of two kinds: ist, the homoihalVic (moncecious), in which all of the colo- 

 nies or thalli developed from different spores are the same, and both gametes 

 may be developed from the mycelium from a single spore, as in Sporodinia 

 grandis, a mould common on old mushrooms; 2d, the helerothallic (dioe- 

 cious), in which certain plants are of a male nature and small in compari- 

 son with those of perhaps a female nature which are larger or more vigor- 

 ous. W'hen grown separately each of these two kinds ot thalli, or colonies 

 of mycelium, ]"jroduce their own kind but only sporangia. I! the two kinds 

 arc brought together, however, branches from one conjugate with branches 

 from the other and zygospores are produced, as in Rhizopus nigricans, the 

 common bread or fruit mould. This is one reason why we rarely find this 

 fungus forming zygospores. (See Blakeslee, Se.xual Reproduction in the 

 Mucorineffi, Proc. Am. Acad. Arts and Sci., 40, 205-319, pi. 1-4, 1904.) 



