LIFE HISTORIES OF FUNGI 259 



harmful result followed. The discoverers of the toxin 

 suggest that the discovery may possibly throw light on 

 ''pellagra" and some of the destructive diseases of cattle, 

 such as "cornstalk-disease," and the "horse-disease," 

 prevalent in some of our western states, and for some 

 time thought to be due to some food-impurity. 



262. Vegetative Mtiltiplication. — At various points the 

 mycelium produces one or more upright, aerial hyphae, 

 15 to 20 millimeters high, and of larger diameter than the 

 mycelial hyphae. One or more of these hyphse eventu- 

 ally bend over and grow for a short time along the 

 surface of the substratum, like the stolons or "runners" 

 of such plants as strawberries. Finally, at their free ends 

 there develop slender hyphse that penetrate the sub- 

 stratum, like rhizoids, and another group of the larger, 

 aerial hyphae, one or more of which may repeat the process 

 just described. The formation of these stolons suggested 

 a former name of the plant, viz., Mucor stolonifer. 



253. Asexual Reproduction. — At the tip of each up- 

 right hypha there develops a globular sporangium, and 

 hence the hypha is called a sporangiophore (Fig. i86). The 

 protoplasm is constantly streaming up the sporangiophore, 

 getting more and more dense toward the sporangium, and 

 contains large numbers of nuclei. Further down, to- 

 ward the base of the sporangiophore, the protoplasm 

 becomes thinner and thinner, and the nuclei, fewer in 

 number, finally disintegrate. In the meantime the tip 

 of the sporangiophore increases in size until the globular 

 sporangium is formed, rich in cytoplasm and nuclei. 

 By degrees the protoplasm becomes more dense toward 

 the periphery, and gradually thinner toward the central 

 portion, where large numbers of vacuoles develop. Soon 



