CARPOASCT. 



119 



Order Gymnoascaceae. The ascocarps are borne sometimes solitarily, or 

 sometimes coiled together. Gymnoascus reessii forms small bodies about 1 

 mm. in diameter on old horse-dung, which at first are white and afterwards 

 orange-red. Ctenomyces serratus lives on the old feathers in birds' nests. 



Family 2. Perisporiales. 



The ascocarps are surrounded by a complete envelope without any 

 opening : the fruit-bodies are cleistocarpic ; the spores are only 

 liberated after the disintegration of the fruit-bodies. Paraphyses 

 are wanting. The two first orders have in addition the means 

 of reproduction by conidia. 



Order 1. Erysiphaceae, Mildews. The Fungi belonging 

 to this order are epiphytic parasites, whose mycelium, somewhat 

 resembling a cobweb, may be seen on the leaves and other 

 green portions of plants (see Figs. 107, 108). The hyphte ramify 



FIG. 107. Erysiphe ciehoriacearum : a mycelium-threads; b sterile hypha ("pollino- 

 clium") ; c fertile hypha (ascogone or archicarp) ; d and e young ascocarps. 



in all directions upon the surface of their host, and emit haustoria 

 which penetrate the epidermal cells, and thus derive the necessary 

 nutriment. The Mildew-Fungi thus belong to the obligate para- 

 sites, and during their growth dwarf and destroy the portions 

 of their host on which they live. The reproduction takes place in 

 the first instance by abstriction of conidio-chains from the end of 

 special branches (Fig. 108 c, a hypha is seen in the act of detaching 

 a conidium). The conidia may germinate immediately, and thus 

 quickly reproduce their species. When present in large numbers 

 they appear as a white meal covering the surface of the plant on 

 which the fungus is found. Later on appear the dark brown, 

 spheroid ascocarps (Fig. 108 a) which, although small, are gene- 

 rally just visible to the naked eye as black specks. 



A characteristic feature of the Mildew-Fungi is the thin, pseudo- 



