i35 
c Biologic Forms ’ of the Erysiphaceae . 
(No. i) vigorous patches of mycelial hyphae, proceeding from the sown 
conidia, were visible on the fifth day, on the semi-translucent tissue which 
had been bruised by the pressure of the weight. On the seventh day a small 
cluster of nearly mature conidiophores was visible on the bruised place. On 
the thirteenth day there were several little clusters of conidiophores 1 on the 
bruised part, which was now yellowish and translucent. On the seventeenth 
day patches of conidiophores were still visible, scattered over the bruised place. 
In the second experiment (No./) conidia were sown not only on the 
bruised part but also at a distance of 1-5 cm. from the edge of the bruise. On 
the seventh day (Jan. 16) the central part (which measured 2*5 mm. across) of 
the bruised tissue was formed of translucent, dead, and disorganized cells ; 
round this the cells were slightly yellowish, and nearly translucent, and here 
numerous little patches of mycelium were formed. On the twelfth day 
several little clusters of conidiophores, on patches of radiating mycelial 
hyphae, occurred round the bruise, at distances up to 2 mm. from the 
edge of the bruise. Two of the conidia sown at a distance of 0-75 cm. from 
the bruise produced a minute patch of mycelial hyphae and a few conidio- 
phores ; some of the conidia sown at a distance of 1-5 cm. produced minute 
barren patches of mycelial hyphae. 
In the third experiment (No. a 2) a few patches of mycelial hyphae, 
bearing a few conidiophores, were produced on the bruised cells. 
In the next three experiments, pressure, using a weight of 9*5 oz., was 
applied for 2 hours only. 
In experiment No. £, conidia were sown on the bruised place and also 
on either side at a distance of 1 cm. By the tenth day five little patches 
of mycelium, each with a few conidiophores, were visible on the bruised 
place; no infection occurred at the inoculated places 1 cm. distant. In 
the two other experiments (Nos. a 21, <225) no infection resulted on the 
slightly bruised places. 
In six experiments barley leaves were injured by pressure applied by 
hand in the following way. The barley leaf was laid flat on a glass slide, 
and the end of a glass rod with rounded edges was pressed firmly down so 
as to crush a group of cells. By this means a circular bruise, 4*5 mm. in 
diameter was made. The crushed cells were rendered more or less 
translucent, and if the bruise was severe soon died ; the surrounding tissue 
for a little distance became discoloured by the expression of cell-sap from 
the injured cells into the intercellular spaces, and so rendered more or less 
translucent by transmitted light and opaque by reflected light. 
In the first experiment (No. m) eight barley leaves were bruised rather 
lightly on the upper surface. On the sixth day small vigorous mycelial 
1 There were ten of these clusters, each bearing about twenty conidiophores ; so that, roughly 
speaking, about 200 conidiophores, each bearing six to ten conidia in a chain, were produced at the 
bruised place. 
