THE BREAD MOLD 55 



Each group of downward branches is connected by horizontal 

 branches with neighboring groups. 



Within the cell wall which covers the plant is a colorless protoplasm 

 that includes many vacuoles of different sizes, and often also yellowish 

 fat drops, similar, except for their color, to the vacuoles. Frequently 

 the protoplasm is seen to be in motion. Scattered through it also 

 are many nuclei ; but they are too small to be seen in the living plant. 

 The presence of many nuclei in a single cell is another important differ- 

 ence between the bread mold and any of the plants previously studied. 

 As the mold plant grows older, and especially when it is forming spores, 

 cross waUs appear here and there in various places, dividing the plant 

 into several or many cells, each of which stiU commonly contains 

 many nuclei. The same sort of cell division may occur earlier in the 

 life of the plant if the supply of water becomes insufficient, or if for 

 any reason conditions are imfavorable for growth. 



80. Food. — Since it has no chloroplast and no chlorophyl, 

 the bread mold cannot use carbon dioxid and water to build 

 up carbohydrates, and, like the bacteria and the yeasts, it 

 must obtain its carbohydrate food ready made. Like the 

 yeast, the bread mold is a saproph}i;e — that is, it Hves upon 

 dead organic materials. The carbohydrate food present in 

 bread is chiefl}- starch ; there is also some ceUtilose and there 

 are probably traces of sugar. The starch, as well as the pro- 

 teins which are present in the bread, must be digested — 

 that is, must be changed by enzA,Tns into simpler substances 

 that can be dissolved and so taken in by the mold through its 

 wall. The bread also supplies water, of which the mold 

 requires a great deal, and probably small arhounts of other 

 food substances as weU. When more carbohydrate food is 

 taken in than the plant can use at once, the surplus is trans-, 

 formed into fat. Fat is a very common reser\'e food in fungi, 

 taking the place of the starch that is so abundant in most 

 green plants. 



81. Spore Formation. — After the mold has been growing 

 for some time and has reached a considerable size, branches 

 of a third kind begin to appear. These are stouter than the 



