PERI8PORIACEJE. 



tilization. The sexual organs and the sporocarp resulting 

 from the act of fertilization bear a striking resemblance to 

 those of Coleochcete, the difference being such as may be ac- 

 counted for by considering the aquatic habits of the one, and 

 the aerial and parasitic or saprophytic habits of the other. 



373. In the parasitic Perisporiacecethe jointed filaments 

 of the mycelium closely invest and cover the leaves and 

 other tender parts of their hosts, and draw nourishment 

 from them by means of haustoria, which project as irregular 

 pullulations from the side of ^ 



the hyphae next to the epider- 

 mis (Fig. 187) ; these haustoria 

 apply themselves closely to the 

 epidermis cells, and, in some 

 cases at least, appear to penetrate 

 them.* The crossing and rami- 

 fying hyphae soon send up many 

 vertical branches, in which parti- 

 tions form at regular intervals; 

 the cells thus formed are at first 

 oblong and cylindrical, with flat- 

 tened ends ; but the topmost one 

 soon becomes rounded at its ex- 

 tremities, and the others follow ng _ 18r ._^^ (Oidium) 

 in quick succession, thus giving h ^,* p p ^ 



rise to a niOlllllform rOW of loose- epidermis of the leaf of the vine, and 

 , i i IT , i i i to which it is fastened by the haus- 



ly attached elliptical or rounded toria. A/ &, an isolated 'piece of a 



cells, the conidia (T, Fig. 188). 



These fall off and germinate at AfterVonMohl - 



once by pushing out a germinating tube, which gives rise 



to a new mycelium. 



374. The sexual process, which in most species takes 



* De Bary (' Morphologic und Physiologic der Pilze," etc., 1865, p. 

 19) says that the haustoria of the investigated species do not penetrate 

 into the epidermis cells ; while Sachs (" Lehrbuch, 4te Auflage," 1874, 

 p. 312) says that haustoria are sent into the epidermis cells. A myce- 

 lium on Poa pratensis (probably of Erysiphe communis) examined in 

 1877 appeared to have sent its haustoria through the outer walls of 

 tho epidermis cella 



