CEYPTOMYCES. 



247 



especially Salix incana, but also on ^S*. purpurea. When the 

 black apothecial cushions break out through the bark, the twigs 

 of the host-plant are frequently still green and leaf-clad. 



The apothecia originate in the lower bark and so loosen 

 the epidermal layers as to cause the appearance of yellow spots. 

 Black centres appear in the spots, due to the formation of a 



Fig. 132. — Cryptomyces maximum. 1, Cross-section of a twig of Salix incana, 

 with stroma a b ; the mycelium occupies the rind and bast into the cambium, so 

 that a wood-ring for the current year has been only partially developed ; the 

 shaded part between a and h is an aerating tissue, formed of loose hyphae, which, 

 with a, forms the stroma proper ; 6, the ascogenous layer. (Lens-magnification.) 

 2, Asci, showing a dry ascus ; one to which water has been added, so that it is 

 elongating ; one ruptured and ejaculating spores. 3, Young stromata in spring, 

 still covered by the epidermis of the Saiis:. 4, Willow twig after detachment of 

 the patches of Crypiomyces in autumn, (v. Tubeuf del.) 



black apothecial cover underneath the epidermis. On rupture 

 of the epidermis, black apothecial cushions emerge and cover 

 large areas of the living twigs. Eain causes the apothecia 

 to become gelatinous, and to swell considerably ; on drying 

 the cushions roll up and fall off, leaving scars' in the bark 

 (Figs. 132, 4). 



