INFECTION-POWERS OF ASCOSPORES IN ERYSIPHACE® 209 
same as those of the conidial ina In the — experiment, 
however, in which ascospores were sown on H. jubatwn—a species 
which Marchal states is infooted ca the conidia of the fungus—no 
infection occurred. I must state, however, that in some infection- 
experiments with the Oidium on Hordewn vulgare, now being carried 
on, I have not been able to cause infection on H. ju 
n these infection-experiments, the details of which I hope to 
Sabla shortly, some pease have been obtained which seem to 
show that certain species of Hordeum exist which, while usually 
immune as regards the Beige of the Oidium on H. vul gare, are y 
occasionally susceptible. In such cases the conidia produce, at 
of inoculation, only a few scattered cect a which 
usually soon disappear. I have met with the same phenomenon 
v 
appeared on H, bulbosum, H. maritimum, and H. secalinum—species 
which, as a rule, the conidia of the Oidium on H. vulgare fail 
entirely to touch. In the case of H. bulbosum a little group of 
ia poe Sia ee thirty—bearing chains of spores, appeared on 
ne leaf on the sixth day after inoculation. The fungus by the 
ve day bad ae way. On H, maritimum only seven 
conidiophores appeared on a single leaf; these — for a few 
days. On H. secalinum, however, the infection wa more pro- 
nounced, aia al picker of Oidium with almost ssnueiaks masses of 
spores being produc 
Now it is certainly possible that in nature—if we may assum 
that a number of plants of any of these three pone —- near 
ume (a 
an Oidium may occasionally extend its range of host-species. 
Another fact observed is of interest in connection with the 
present subject. ze i ng when sown on the epidermis of a 
le 
af, at once germ ; the germ-tube swells pes the end, 
applies itself closely to ‘tie cell-wall, and forms the first appressorium. 
Penetration cell-wall from this appressorium takes place, 
resulting in the roe after twenty hours from sowing, of the 
first haustorium. In the case of conidia sown on a eaf of their 
Were sOwn on whea @ 
the haustoria beseg are een on ihe ‘* wrong at ce ars do 
not increase in size and as a rule do not hanes the finger-like 
processes. In some cases what appeared to be the gradual breaki 
died and disintegration of the haustorium has been observed. 
Journan or Botany.—Vot. 41. (June, 1903.) P 
