LIFE HISTORIES OF FUNGI 
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meet, the dense protoplasm has been cut up into innumer- 
able, more or less angular masses, each surrounded by a 
plasma-membrane, and containing from two to six nuclei 
FIG. 187. Rhizopus nigricans. i, Full-sized sporangium, showing 
layer of vacuoles nearly formed along the inner surface of the denser plasm, 
X about 200. 2, Section passing to one side of the sporangiophore, 
showing columella-clef t being formed by fusion of the vacuoles shown in i , 
and by a furrow from the base of the sporangium, X about 200; 3, Detail 
of another part of same sporangium as shown in 2, showing early cleavage 
furrows, X about 850. (After D. B. Swingle.) (Cf. Figs. 186 and 188). 
each (Fig. 187). These finally become entirely separated 
from each other, oval in shape, and surrounded by a cellulose 
wall, having clearly marked ridges (Fig. 188). They are 
