EUTHALLEPHYTA—EUMYCETES— MOULD 



197 



to the specimen, the wall of the sporangium collapses and the end of the stalk, 

 known as the columella, turns back, giving it something of the appearance of 

 an umbrella. The columella, before it collapses, projects into the sporangium. 



Fig. 40. Mucor Rouxii. Conidio- 

 phore. 2. Gemmae. 3. Chlamydo- 

 spores. All greatly magnified. 1 after 

 Vuillemin. 2 after Calmette. 3 after 

 Wehmer. (Modified by Charlotte M. 

 King). 



The spores germinate readily when placed in a moist atmosphere. In 

 addition to the production of a sporangium a stalk may bend over and cause 

 the further extension of the fungus by producing what is known as a stolon. 



In some species small, round, or elongated spores are produced in the 

 mycelium which are known as chlamydospores, and spread the fungus. In 

 addition to the formation of spores in the sporangium, zygospores are pro- 

 duced in some species ; two threads of the mycelium lie in proximity and nearly 

 parallel, each produces a tube ; these meet, the walls are absorbed, and, just 

 back of the meeting point, a cell is cut ofif. The contents from the old cells 

 pass into the newly formed cell. We also observe that the cell of one arm is 

 somewhat smaller than that of the other. This spore is a resting spore or zygo- 

 spore. It lies dormant for a period, then germinates by forming directly a con- 

 iodiophore with its sporangium containing the spores. 



Prof. Blakeslee has shown with reference to the fertilization of some of 

 the species of Mucor that it requires a male and a female plant. In speaking 

 of Mucor niucedo he says : 



Mucor mucedo has the sexes separated on different individuals as in Phycomyces. but two 

 different kinds of germ tubes are formed by the germination of its zygospores. While some 



