132 



MYCOLOGY 



other without paraphyses, so that they form a velvety layer on the 

 surface of the host plant. Eight ascospores are generally found, as in 

 the genus Exoascus, but in Taphr'ma (Taphria) the number may be 

 increased considerably by budding, so that the whole ascus will be 



-::#\ 



■^h 



y , ,; ff 



^^^ ^rrf^f 



Fig. 42. — Exoascus and Taphrina. A-F, Exoascus pruni, A. Appearance on 

 diseased twig; B, cross-section of diseased fruit; C, mycelium in tissues of host; D, 

 young asci; E, mature ascus with spores; F, germination of spores; G, E, Exoascus 

 alnitorquus; H, Taphrina aurea, ripe and unripe asci; J, Taphrina Sadebeckii. See 

 Die naturlichen Pflanzenfamilien I. i, p. 159. 



crammed full of them (Fig. 42). The ascospores are generally ellip- 

 soidal and always one-celled with colorless, yellow, or orange contents. 

 The perennial mycelium is responsible for the formation of witches' 

 brooms in a variety of trees and woody plants. Most of them are the 



