14 SALMON : SUPPLEMENTARY 
bacco plant. Iwanowsky observed an Ozdium, which he re-_ 
ferred to the conidial form of “ &. lamprocarpa” (= E. cichora- | 
ccarum), occurring on the leaves of some Compositae, especially — 
Inula Helenium and Lappa tomentosa. This Oidium he found | 
on examination to resemble strongly the Ozdium on the tobacco | 
plant. To quote the author’s words: ‘Bei der Aussaat dieser — 
Conidien auf die Blatter der Tabakspflanze entwickelte sich in | 
der That das Tabaks-Ocdium ; hieraus folgt, dass Letzteres zu i 
Erys. lamprocarpa gehért; jedoch bildet dieser Pilz auf dem | 
Tabak keine Fruchtkérper. In Form von Fruchtkérpern wtber- | 
wintert er auf den genannten Compositen und inficirt im fol- j 
genden Sommer die Tabakspflanze.’’ (3) Neger (54, P. 339) 
records the following observations: ‘‘ Auch das Nahrsubstrat- 
scheint Einfluss zu haben auf die aussere Gestalt der Conidien. 
Ich tibertrug Conidien von Arysiphe communis, welche auf Ranun- 
culus sp. entstanden waren, auf eine vollkommen gesunde, unter 
einer Glasglocke stehende Pflanze von Galium silvaticum ; die 
Infection gelang ; nach einigen Tagen trug das Ga/ium Rasen von 
Conidien-tragern. Der Vergleich ergab, dass die Conidien auf Ga- 
fium betrachtlich langer waren als diejenigen auf Ranunculus.” 
Cases apparently showing that in nature a species of mildew on 
one host-plant sometimes passes over to a contiguous plant of an- 
other species are mentioned by two botanists: (4) Allescher (in 
the Bericht. botan. Verein. Landshut, 146-152. 1887) has re- — 
corded the occurrence of Microsphaera Ehrenbergii (= M. alm 3 
var. Jonicerae) on Syringa vulgaris, and has stated that the Syr-_ 
inga affected stood in the immediate neighborhood of a bush of : 
Lonicera Tatarica attacked by the same fungus. On Allescher’s 3 
specimen sent to me it was noted that the fungus occurred only © 
on the branches of the Syringa which were close to the Lonicerd. — 
(5) Brannon (8) has recorded “Exysiphe communis (Wall.) Schl.” 
occurring “on Ranunculus recurvatus and an aster growing in 
the same place which had probably received the mildew from its — 
neighbors.”’ 
(6) Polla (in Bericht. deutsch. bot. Gesell. 17: 67. 1899) 
has made some observations bearing on the present subject. This 
author, having observed that in certain districts only Berderis 
vugaris and Corylus Avellana were attacked by Phyllactinia, — 
