4 A Monograph of the Erysiphaceae 



face of these (which are closely appressed to the cuticle), or from 

 the hypha itself at the point where the swelling originates, the 

 haustoria are produced in the usual manner — these are termed 

 haustoria appendiculata ; or, finally, the hyphae are sometimes 

 provided with processes, often on both' sides at the same point, 

 which are more or less deeply lobed or crenulate at the margin, 

 or reniform in shape, and from these swellings, or from the hypha 

 itself adjacent to them, the haustorium proceeds — these are hmis- 

 toria /obnlata (Y'lg. 128). 



The genus Phyllactinia shows some important differences in 

 the majincr of producing haustoria. As pointed out by Palla 

 (264), in his valuable paper, the vegetative mycelium on the under 

 surface of the host-leaf does not send haustoria into the epidermal 

 cells, but forms special hyphal branches, of limited growth, which 

 enter the stomata, penetrate into the intercellular spaces, and finally 

 send haustoria into the surrounding cells of the spongy-paren- 

 chyma (Fig. 163). Each of these special branches, or " Ernah- 

 rungshyphe," consists of two, three, or rarely more cells, and is 

 sometimes sufficiently long to extend through the spongy-paren- 

 chyma to the palisade-ceils, but no haustorium has been observed 

 to be formed in the cells of this layer. Each " Ernahrungshyphe," 

 of which sometimes two pass through the same stoma, produces' a 

 single haustorium, in all cases, from its last cell. Sometimes two 

 haustoria (produced by different hyphae) are found in one cell. 

 The haustorium itself does not differ from that found in the other 

 genera of the ErysipJuiccac. 



With the exception of the haustoria, and the special branches 

 of Phyllactinia, the mycelium of the Erysiphaceae is entirely super- 

 ficial, /. €., external to the tissues of the host-plant. In the rose 



been frequently stated that 



Sph 



the mycelium hibernates during the winter months within the tis- 

 sues of the host-plant, but this statement appears to rest merely on 



supposition. 



The first kind of reproductive bodies borne by the mycelium 

 are the asexually-produced conidia, which are formed under favor- 

 able circumstances, throughout the summer and during the early 

 part of autumn. The mycelium produces special hyphal branches 

 the conidiophores, which are erect, simple, colorless or white, thin- 



