THE FUNGI. 125 



CLASS III. The Molds and Mildews (Phy corny cetes). - 

 The most important plants of this class are the Black 

 Molds, the Mildews and Rusts, and the Water Molds. 



The Black Molds {Mucorinece) . The Mucorinece are 

 among the commonest of the molds. They are found in 

 abundance on moist, decaying organic matter. They are 

 saprophytic in their nourishment. The plants grow from 

 rootlike filaments which interlace just above or just be- 

 neath the surface of the substance on which the mold 

 grows. This interlacing rhizoid is called a mycelium. 

 From it delicate stalks or hyphse rise tipped with en- 

 larged masses which are sporangia filled with spores. As 

 the spores ripen they become dark colored so that the 

 mold, which was in the earlier stages colorless or white, 

 turns black. 



The reproduction is ordinarily asexual by the spores 

 already mentioned. These spores dry up and are carried 

 about in the air. They, retain their vitality indefinitely. 

 When they fall on decaying organic matter under suit- 

 able conditions of temperature and moisture, they develop 

 at once by cell multiplication into new plants. 



The sexual process of reproduction is of much less fre- 

 quent occurrence than the asexual process. Two hyphse, 

 which must, of course, be of opposite sexes, send out pro- 

 jections to meet. These projections are then separated 

 from the hyphse that produce them by the growth of a 

 cellulose wall. The meeting ends of the projections break 

 away, and the contents of the two cells mingle in one. 

 The resulting zygospore becomes encysted in a wall 

 that is sometimes covered with curious protuberances. 

 According to Strasburger, it is easy to raise the zy go- 

 spores in moist chambers by sowing the asexual spores 

 on thick plum juice mixed with 10 to 20 per cent of 

 ethyl alcohol. Zygospores are also said to be formed in the 

 spring of the year on Mucor that grows on horse manure. 



