254 



APPLIED BIOLOGY 



are formed by expansion of the ends of aerial hyphse. The proto- 

 plasm inside these expanded ends divides into numerous small 

 masses, each of which becomes a spore. Examine with high power 

 of microscope spores obtained by brushing a wet needle or small brush 



against some sporangia and 

 then rubbing the spores col- 

 lected into a drop of water 

 on a glass object-slide. 

 Notice the thick cell-wall, 

 which is very protective 

 against heat, drought, and 

 other unfavorable con- 

 ditions. 



(D) If some spores be 

 placed in a dilute sugar solu- 



FIG. 80. Unlike the spherical spore-case of 

 the black mold, the green mold forms 



tion in a watch-glass, many 



spores (sp) at -ends Tof branches i of aerial of them will be found ger- 

 hyphae. minating after a day ; and 



after several days much 



branching will produce an extensive mycelium (Fig. 79). Later some 

 aerial branches or hyphae arise and form spore-cases. The entire 

 mycelium and aerial branches with spore-cases, which originate from 

 a single spore, is a mold plant. Usually such plants are closely in- 

 terlaced, because many spores fall on the same piece of bread. 



Sometimes a 

 peculiar method 

 of reproduction 

 occurs as follows: 

 From each of two 

 hyphae which 

 happen to lie 

 near together, 

 c 1 u b-s h a p e d 

 bodies grow until 

 their ends meet 

 (Fig. 81). The protoplasmic contents in the ends of the 

 two bodies unite into one mass, and around it a thick wall 

 or coat forms. There is thus formed a combined spore 



b c d e 



Stages in conjugation of two mold hyphae, 



a 



FIG. 81 



forming the spore (zyg). 



(From Parker.) 



