‘ Biologic Forms' of the Erysiphaceae. 145 
Experiments with Conidia obtained by sowing conidia from 
Wheat on Barley leaves rendered susceptible by the 
action of Alcohol, Ether, and Heat respectively. 
(1) Alcohol. 
(a) Conidia produced on barley leaves previously immersed 
for 4 hours in io°/ o alcohol . 
Experiment No. 77*. Conidia produced on the fourteenth day 
were sown, at a marked place, on a leaf of barley and of wheat 1 . By the 
seventh day a little powdery Oidium- patch was produced on the wheat leaf, 
at the marked place ; no trace of any infection appeared on the barley. 
EXPERIMENT No. a 92. Conidia produced on the fourteenth day 
were sown, at a marked place, on two leaves of both barley and wheat. On 
the seventh day the two wheat leaves were fully infected, at the marked 
place, with small vigorous Oidium- patches ; no trace of any infection 
appeared on the barley. 
Experiment No. #99. Conidia produced on the sixteenth day were 
sown, at a marked place, on a leaf of barley and of wheat, and a control leaf 
of each placed by the side. On the fifth day both the barley and the 
wheat leaf bore, at the marked place, a small patch of mycelium bearing 
a few young conidiophores, the patch on the wheat being a little further 
developed than that on the barley. By the eighth day the wheat leaf had 
produced two small, contiguous, very powdery Oidium- patches ; the 
mycelial patch on the barley leaf had not developed further, except that it 
now bore five conidiophores which were beginning to wither. On the 
eleventh day a few conidiophores were still visible on the now hyaline 
barley leaf, but no further growth of mycelium had taken place. The 
control leaves of barley and wheat remained quite free. Conidia were 
taken from the wheat leaf and sown in considerable quantity on a barley 
leaf, but no trace of any infection resulted. 
Experiments Nos. a 100 and # 015. Conidia produced on the tenth 
day were sown in each experiment, at a marked place, on a leaf of barley 
and of wheat. On the tenth day a large powdery Oidium- patch was 
produced, at the marked place, on the wheat leaf; no trace of any infection 
occurred on the barley. 
Experiment No. #019. Conidia produced on the twelfth day were 
sown, at a marked place, on a leaf of barley and of wheat. By the ninth 
day a large vigorous and powdery patch of Oidium was produced at the 
1 In all these experiments the leaves used were cut off from seedlings of barley and wheat, and 
placed at the bottom of a Petri dish on damp blotting-paper. 
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