‘ Biologic Forms' of the Erysiphaceae . 14 1 
of conidiophores. On the seventeenth day one leaf bore numerous vigorous 
patches of clustered conidiophores ; the other two leaves bore only a few 
isolated sub-solitary conidiophores, just as in cases of £ sub-infection V 
A 30 °/ o mixture of alcohol was used in a few experiments. It was 
found that immersion for 4 hours in alcohol of this strength killed barley 
leaves. In two experiments barley leaves were immersed for 2 hours. In 
experiment No. a 85, the three treated leaves showed on the seventh day 
evident signs of injury, the injury often being local and causing the death 
of patches of cells. On one leaf a patch of numerous clustered conidio- 
phores appeared at the inoculated place. In experiment No. #90, three 
leaves were treated, and inoculated together with three control leaves. On 
the eighth day all the treated leaves were killed or injured in places towards 
their tips ; one leaf bore a few little clusters of conidiophores, and several 
patches of mycelium. No infection occurred on the controls. 
The effect of vapour of alcohol was tried in two experiments* In 
the method employed the barley leaves were suspended on an open 
cradle over a watch-glass containing absolute alcohol, in a hermetically 
closed Petri dish. Exposure for 10 minutes was found to kill the 
leaves. In experiment No. a 027, two leaves were exposed for 3 minutes 
(the air being more or less completely saturated with vapour of alcohol at 
the commencement). On the sixth day one of the leaves presented all the 
appearance of being fully infected, and bore vigorous patches of mycelium 
with thousands of conidiophores at a place towards the tip of the leaf, sur- 
rounding a patch of cells killed by the action of the alcohol. Conidia from 
this barley leaf sown on an uninjured leaf of barley and of wheat proved 
able to infect only the wheat. 
Drops of various poisons (caustic potash, 10 °/ o ■; copper sulphate 
(1 part in 100) ; sulphuric acid, 10 °/ o ) were placed on barley leaves, and 
after the leaves had been washed in water conidia and ascospores were sown 
on the patches of cells killed by the action of the poisons, and on the cells 
immediately surrounding, but no infection resulted. 
rj. Injury caused by Heat. 
It was found that barley leaves, heated in water up to 67° C., and left 
in the water until it had cooled to 50° C, were killed. Also, if barley 
leaves are immersed in water heated to 48° C., and the temperature is then 
raised to 65° C., and the leaves left in the water until it cools to 6o°C., the 
leaves are at once killed. Barley leaves can, however, stand immersion 
in water at a temperature of 50° C, and this treatment induces a marked 
susceptibility of the leaf. In five experiments barley leaves were placed 
in cold water in a large glass beaker, and the water heated slowly 
to 50° C. The leaves were then taken out at once, dried, and inocu** 
1 See ‘ Beihefte z. Botan. Centralbl./ xiv. 271, 
