NOTES ON THE ERYSIPHACEAE 187 
conidium occurs which measures over 50 »# long; the elliptical 
conidia measure 30-33 x 17-19 p. On Heracleum Sphondylium 
(Umbelliferae) (f/. 9, f. 2) elliptical conidia are of quite common 
occurrence ; considerable variation in size is found also here. On 
Anthriscus sylvestris (Umbelliferae) (pl. 9, fr) most of the 
conidia are cylindrical, but occasionally elliptical ones occur. 
Also, in examples on Delphinium hybriium, D. elatum, and D. 
Maackianum (Ranunculaceae) (f/. 9, f. 9) the shape of the conidia 
varies from elliptical to cylindrical. The reduction of “ Z. wmdbel- 
liferarum”’ to E. polygoni appears therefore fully warranted. 
It may be here pointed out that, as f 1, 2, and 8 on pl. 9 
show, the conidiophores of &. po/ygoni bear only a single conidium 
at the apex, unlike the Ozdium form of many mildews, where the 
conidia are concatenate in long chains (see monograph f. 727 for 
that of 4. galeopsidis, and f. rgo for that of £. cichoracearum ; 
see also f. rr5, 117, and 156). It would be interesting to 
ascertain if this feature is characteristic of E. polygoni, as if so it 
might be of use in distinguishing the species in its conidial 
condition. 
In connection with the fact mentioned above of the conidio- 
Phores of £. polygoni bearing only a single spore, we may note 
that Passerini has published the following description of a fungus 
(Nuov. Giorn. Bot. Ital. 13: 282. 1881): “ Ozdium monosporum 
Passer. hb. Epiphyllum, maculas discoideas pulveraceo-cinereas 
demum fuscas efformans. Hyphae longae, subclavatae, articu- 
latae, in sporam unicam oblongo-ellipticam desinentes. An 
Ovulariae Sacc. Michel. 6: 17, analogum ?—Sulle foglie della 
Robinia hispida L. nel R. Orto Botanico, Luglio.” Professor C. 
Avetta has kindly sent me the type-specimens of “0. mono- 
Sporum” from Passerini’s herbarium at Parma University, and 
examination of this has convinced me that the fungus described 
is merely the conidial stage of E. polygont. The subcylindrical 
Conidia measure from 28-40 » long x 13-164 wide. £. polygoni 
is known to occur on other species of Robinia (R. Pseudacacia and 
R, viscosa). 
In germinating some conidia of E. polyguni on Delphinium 
Maackianum in a hanging drop of water, several cases were 
Observed of the formation of lobed “ appressoria” at the places 
