DEVELOPMENT OF PLANTS 



225 



veloped by a mass of hyphae that originate from the mycelium. 

 These ascocarps appear at maturity as black specks and in the 

 majority of forms they are provided with hair-like outgrowths 

 that are very regular and characteristic of the genera (Fig. 148). 

 The ends of these hairs are rather mucilaginous and may assist 



Fig. 147. Sexual reproduction of a powdery mildew: A, meeting of the 

 male, an, and female, 0, gametangia. B, fertilization, the male gamete, m, 

 is seen approaching the female. C, section of young ascocarp showing the 

 early germination of the gametospore, which has become surrounded by 

 hyphae derived from the mycelium. D, later stage, the gametospore has 

 developed several cells and the second cell from the end, as, will produce 

 the ascus. — After Harper. 



in the dissemination of the ascocarps. The ascospores are resting 

 spores adapted to enduring drought and cold as in Penicillium, 

 which they resemble in their discharge and germination. 



87. Forms with Slightly Opened Ascocarps. — Several orders 

 of the Ascomycetes are distinguished from the preceding group 

 by the formation of ascocarps that are slightly open (Figs. 151; 

 152, B). In this way, provision is made for the discharge of 

 the ascospores without the decay of the ascocarp. Only two of 

 these orders can be noticed. 



88. Order e. Sphaeriales or Black Fungi. — This is the largest 

 group of the ascomycetes, over 2,000 species being known in the 

 United States alone. Scarcely a fallen twig or bit of old wood 



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