120 REPRESENTATIVE PLANTS 



serve the varying growths on each substance ; also that black 

 mold may grow on other substances besides bread. 



Appearance. Examine mold under glass, with a lens, and 

 observe its appearance ; also the tiny enlargements, light or 

 dark colored, on the ends of some threads. Observe the 

 total absence of true leaf green (chlorophyll) ; also in a well- 

 grown specimen, observe how the mold seems to grow out 

 from the bread along the sides, or even creep over the glass 

 plate on which the saucer containing the bread is placed. 



Microscopic structure. Examine a specimen under (Zp) and 

 observe the white threads that make up most of the plant. 

 This thread is called the mycelium, and really composes the 

 body of the mold plant. Observe, here and there, rootlike 

 structures, that attached the mold to the bread, and from 

 which a number of the threads diverge. Of what use would 

 these attaching structures be to the mold plant besides 

 holding it in place ? Some of the diverging threads, above 

 mentioned, may end in white or dark knobs, sporangia or 

 spore cases. 



Sporangia. Try to trace all the stages in the formation of 

 these sporangia from the slightly enlarged end of the fila- 

 ment, to the black, spherical body, a ripe sporangium. 

 Find a crushed sporangium. What size and number are the 

 contained spores? 



Mycelium. Examine in detail the mycelium of the mold. 

 Is the plant one or more celled as shown by the filament 

 (exclusive of the sporangia which are at last separated from 

 the rest of the plant by wall)? Do you find branches or 

 not? How are the rootlike structures (substratum myce- 

 lium) sometimes connected with each other? What benefit 

 would these structures be to the plant? 



Drawings. Make drawings showing as many features of 

 this mold as you have been able to find. Be sure to show 

 by a sketch the result of your home experiments. 



Problems. What is your explanation of the molding of 



