138 Salmon . — Further Cultural Experiments with 
the fifteenth day the wheat leaves bore a continuous dense powdery Oidium- 
patch 2 cm. long ; two of the barley leaves bore a few mycelial patches, 
one or two of which, on each leaf, bore a little cluster of conidiophores. 
No infection occurred on the third leaf. 
In experiment No. a 50, four barley and four wheat leaves were exposed, 
two leaves of each for 2 minutes, and two for i\ minutes. The leaves were 
then exposed to the air for 1 hour, after which they were inoculated and 
placed at the bottom of a closed Petri dish, as usual. On the eighth day it 
was found that, of the leaves exposed for 2 minutes, the two barley leaves 
and one of the wheat leaves had been killed ; the remaining wheat leaf was 
killed in places here and there, and in the living parts was virulently 
infected and bore powdery Oidium- patches. Of the leaves exposed for 
ij minutes, the wheat leaves were covered with dense mycelial patches, 
here and there powdery with ripe conidiophores and conidia ; no infection 
was apparent at this date on the barley. On the thirteenth day the wheat 
leaves exposed for i| minutes bore extended and continuous densely 
powdery Oidium- patches, pinkish in colour, consisting of very vigorous 
conidiophores bearing conidia in abnormally long chains. One barley leaf 
was now seen to be infected. This leaf bore, scattered over the inoculated 
surface, vigorous mycelial patches of interwoven hyphae, and numerous 
well-grown patches of clustered conidiophores. Altogether several hundreds 
of conidiophores were produced on this barley leaf, and the appearance was 
that of almost full infection. The other barley leaf was not infected. 
In another experiment (No. a 54), in which two barley leaves and two 
wheat leaves were exposed for i| minutes, both the wheat leaves became 
virulently infected, but no trace of infection appeared on the barley. 
In experiment No. a 44, three barley leaves and two wheat leaves 
were exposed for 1 minute. On the ninth day the two wheat leaves were 
covered continuously for a distance of 4 cm. with a powdery Oidium-patch ; 
at this date there were no signs of infection on the barley. On the sixteenth 
day one barley leaf bore a few minute patches of mycelium, which in two 
cases bore a few conidiophores. On the twentieth day the one barley leaf 
bore numerous vigorous little patches of mycelium, most of which bore 
little groups of clustered conidiophores ; another barley leaf bore one 
comparatively large patch of mycelium bearing a few conidiophores. No 
infection occurred on the third barley leaf. Conidia taken from the infected 
barley leaf and sown on an uninjured leaf of barley and of wheat proved 
able to infect only the wheat. 
b. Chloroform-vapour . 
Exposure of wheat and barley leaves for 30 seconds proved fatal 
to all the leaves used. In experiment No. <208, three barley leaves were 
exposed for 10 seconds. Two of the leaves showed on the ninth day 
