234 A Monograph of the Ervsiphaceae 



to 1 20 X 50 /^ and spores 35-50 // long, are similar to those of 

 the Japanese form. Both, I feel convinced, are to be considered 

 as merely large forms of P, coryka, quite unable to be separated 



systematically, 



Erysiphc dctonsa Fries is, in all probability, the present species, 



as Leveillc has contended (214, p. 145). In the Friesian Herbarium 

 there is a specimen named '*£. dctonsa'' in Fries' handwriting, 

 and this is certainly P, corylea. This specimen occurs on the 

 wood of Fraxinus, however, and is, therefore, not the type which 

 is described in Syst. M}X. as growing on Tanacctum vulgare. I 

 have seen the specimens on Tanacctiun vidgarc (in Montague's 

 Herbarium at the Paris Aluseum), which Leveille has stated came 

 from the same source as those on which Fries founded his species, 

 and find that these also belong, as Leveille has said, to P. coryica. 

 It is true Fries says of his plant **peridiolo solitario " ; with the 

 exception of this character, however, the description applies well 

 to imperfect examples of P. coryica^ and it is to be noted that 

 Fries says ** Peridia . . . idccx^ E, gnttatacJ' The fungus identi- 

 fied by Kickx as Fries' E, detonsa is the SpJiacrothcca called 

 S. huJHuU^ var. fidiginea (see Sacc. SylL Fung. I : 4 ; also 

 Oudem. Rev. Champ. Pays-Bas, 2: 84-85. 



In the description of P, corylea above it is mentioned that the 

 perithecia possess a mass of special apical outgrowths. The nature 

 of these outgrowths has been until quite recently completely mis- 

 understood. Each outgrowth, which springs from the external face 

 of a cell of the outer wall of the perithecium, consists of a stalk- 

 cell (Fig. 173, d)^ bearing a terminal mass of densely-clustered, 

 short, swollen, more or less tubular branches (Fig. 173, /;). Some- 

 times the stalk cells branches irregularly before giving rise to the 

 branches. At a certain stage of development, the branches of each 

 outgrowth become mucilaginous, and their separate walls more or 

 less indistinguishable (Fig. 174, d). In this mucilaginous condition, 

 the outgrowths which arise in a dense mass from the apical cells, 

 cause the firm attachment of the perithecium to the substratum. 

 During the process of this mucilaginous degeneration, the walls of 

 the hyphal branches become more or less dissolved and are invis- 

 ible without staining, while the protoplasmic contents of each 

 branch remain distinct, especially toward the apex (Fig. 175); at 



