1862.] CHAPTERS ON FUNGI. 199 



The species of this group ai'e distinguished by considerable 

 development of the mycelium, by their habit of growing on living 

 plants, by the thin brittle walls of their perithecia, and by their 

 tubular or sac-like asci springing from the base (and not from 

 the walls) of the perithecia. 



At an early stage they present the appearance of Moulds, con- 

 sisting then entirely of interwoven filaments or flocci, generally 

 of a white colour, and in this state they constitute the mildew of 

 the Vine, the Rose, the Turnip, etc., and do much injury, especially 

 to the Vine, which in some places has been almost destroyed by 

 it. In some species the plant never seems to advance beyond 

 this stage, but perithecia and fruit are produced in most species. 



I shall instance the genus Erysiphe. 



Erysiphe. 



Perithecium fleshy, opening at the collapsing apex ; mycelium 

 floccose, effused, free; fulcra floccose. 



Erysiphe communis, Schlecht. Common Erysiphe. Elocci 

 effused, arachnoid, dirty white, at length forming spots ; fulcra 

 simple, acute, deflcxed ; perithecia many. 



On various herbaceous plants, common. Frequent on the 

 garden Pea, forming the Pea-mould of gardeners, E. Pisi. — Grev. 

 Sc. Crypt. Fl. t. 134. 



Appearing at first in the form of a white floccose stratum on 

 the affected leaf (or stem). After a time, minute yellow bodies 

 appear, which become darker and finally black. These are the 

 perithecia and contain short sac-like asci, within which are 

 broadly oblong sporidia, generally four in number. 



Suborder 6, Onygenei. 



Receptacle club-shaped or globose, peridium brittle, filled with 

 branched threads, which produce asci at different points. Asci 

 soon absorbed. Sporidia filling the cavity of the peridium, pul- 

 verulent. 



A very small group and little known. I shall describe the 

 genus Onygena. 



Onygena. ' ( 



Peridium capitate, crustaceous, at length splitting. Asci de- 

 licate, evanescent ; sporidia at length forming a dusty mass. 



The species of this genus are remarkable for growing on ani- 

 mal substances, as hoofs, horns, flannel, etc. 



