DEVELOPMENT OF PLANTS 



221 



Xylaria and Daldinia, which develop an extensive stroma on 

 stumps and trees that contains numerous ascocarps (Fig. 152). 

 In Hypoxylon, the stroma containing the ascocarps breaks 

 through the bark of a large variety of trees and shrubs in the form 

 of spherical or cake-like masses (Fig. 149). 



Fig. 149. 



Fig. 150. 



Fig. 149. A common black fungus, Hypoxylon: A, habit of the fungus 

 as it appears on dead branches and logs. The round black bodies are an 

 association of the mycelium, stroma, and numerous ascocarps. B, a single 

 ascus enlarged, showing character of the ascospores. 



Fig. 150. The black knot, Plowrightia, infecting a branch of cherry. At 

 the bottom of the branch is shown the early summer or spore-bearing stage, 

 c, and above a black warty mass of ascocarps, as, produced the previous 

 season. 



Fig. 151. A, several ascocarps enlarged, taken from region in Fig. 150. 

 B, diagram of an ascocarp as seen in section, showing the asci and the open- 

 ing for the escape of the ascospores. 



89. Order f. Hypocreales. — These fungi are distinguished 

 from the Sphaeriales by their rather fleshy or membranous as- 

 cocarps and stroma, which range in color from white to yellow, 

 purple, scarlet and brown. Numerous species are saprophytic 

 while others are parasitic upon higher plants, fungi and insects. 

 Claviceps is a common example of this group causing the disease 

 known as ergot in the flowers of rye and other grasses (Fig. 

 153). The mycelium at first spreads over the outer part of the 



