158 THE FUNGI WHICH CAUSE PLANT. DISEASE 



Cryptomyces Greville (p. 156) 



A genus of some ten species living on wood or leaves, fonning 

 large black blotches. 



Ascoma sunken in the substratum, flattened, erumpent, irregu- 

 lar in outline, coal black; asci clavate, 8-spored; spores elongate, 

 1-celled, paraphyses filiform. 



C. maximus (Fr.) Rehm " is a parasite on willow and dogwood 

 twigs in Europe and America, forming large carbonous areas 

 under the bark. 



Khytisina Fries (p. 156) 



To Rhytisma belong about twenty-five species which cause very 

 conspicuous, though but slightly injurious, black leaf-spots. The 

 spots which are white within, are due to sclerotial 

 cushions formed in the host tissue. Thickening 

 of the leaf occurs in the infected part. One- 

 celled conidia (Melasmia form) are abundantly 

 produced in pycnidia early in the season, followed 

 by sclerotium formation. Much later, usually well 

 into winter or the following spring, the apothecia 

 a «»i appear. Besides the asco-spore-producing forms 



Fig. 112. — Tro- several species of which the asco-spores are un- 



chila. Ascus i i i r j i_ 



and paraphy- known have been referred here. 



Rehin ^'*®'' Ascoma on a sclerotial stromatic layer, which 

 is black above, white within; ascocarps elongate, 

 opening by a lip-like slit; asci clavate, often blimt pointed, 

 8-spored; spores filiform or needlelike, hyaline, mostly 1-celled, 

 lying parallel and lengthwise of the ascus; paraphyses filiform, 

 hyaline, often arched above. 

 R. acerinum (Pers.) Fr. 



The spot is at first yellow and thickened and in this stage bears 

 numerous conidia upon short conidiophores. The apothecia 

 ripen in spring and rupture by numerous irregular fissures which 

 follow the ridges of the wrinkled surface. Klebahn secured infec- 

 tion by ascospores resulting in three weeks in yellow spots and in 

 eight weeks in conidiospores. The conidia are supposed to aid in 



