FLOWERLESS PLANTS 



161 



Formation of Zygospores. — Two hyphae which are close-lying put 

 out threads which communicate. The end of each of the threads 

 cuts off a cell, and the two cells, each from a different hypha, 

 flow together and mingle. In this condition they remain as a single 

 resting cell. This cell, which puts a heavy wall around itself, is 

 called a zygospore. In the process we called fertilization, we found 

 that the two cells which united to form one cell were of dif- 

 ferent sizes. Here the cells are of the same size. When two cells 

 of the same size unite to form a single cell, we call the process conjuga- 

 tion. The ultimate result of the conjugation of the two cells is 

 that a new plant grows from the zygospore after a period of rest. 

 During the resting stage a b 



the spore may undergo 

 veiy unfavorable condi- 

 tions, even to extreme 

 dryness, heat, or cold. 

 The use of the zygospore 

 to the plant is evidently 

 to continue the species 

 during an unfavorable 

 time in the life history 

 of the plant. The pro- 

 cess of conjugation is 

 probably a sexual process. Its significance is not well under- 

 stood.^ Is there then an alternation of generations in the mold ? 



Physiology of the Growth of Mold. — Mold, in order to grow 

 rapidly, evidently needs considerable moisture and heat. It ob- 

 tains its food from the material on which it lives. This it is able 

 to do by means of digestive ferments, which are given out by 

 the rhizoids or rootlike parts of the hyphae, by means of which the 

 mold clings to the bread. These digestive ferments change the 

 starch of the bread to sugar, and change the proteids into a form 

 that can be osmosed into the hyphae. Thus the plant is enabled 

 to absorb the material. The foods are then changed into 



Conjugation of black mold; A, B. (', D. successive 

 stages in the formation of the zygospore. 



* It seems to have been proved recently that zygospores are formed by the 

 union of two cells, from different filaments, one of which has male, the other female 

 characters. 



HUNTER S BIOL. 



11 



