110 MR. W. G. P. ELLIS ON A TRICHODERMA 
this way were produced clusters of spores like those of figure 26. 
Spore-formation was in some cases very slow indeed: thus at 
6.35 p.m. on Monday, July 13th, I made a sketch of a small part 
from a hanging-drop culture, leaving the same part in the high- 
power field. At 6.35 a.m. on the next day, that is to say after | 
twelve hours, I found that the only change was an increase in 
size of one conidium; no new conidia had appeared. As the 
spores increased in number the clusters became of course darker, 
that is to say more opaque, but there was also a change in colour 
that could be easily made out with the naked eye, and under the 
microscope was seen to be due to the fact that on approaching 
maturity the spores themselves acquired a green, a sort of olive 
green, colour. Hence the whiteness of the young clusters is 
merely due to the air entangled between the branching aerial 
hyphe; the darkening is due to the increasing density caused 
by the repeated branching and the interweaving of the branches; 
the acquirement of the greenish and other tinges is due to the 
increase in number and the consequent collecting together of the 
spores and their approaching maturity. In slide-cultures the 
small clusters did not show the white margin found in tube- and 
flask-cultures but not found on the host; and this fact may indicate 
that the occurrence of this margin is associated with the greater 
supply of nutriment. This idea is borne out by the fact that in 
tube- and flask-cultures there were commonly produced around 
this margin new spore-clusters, so that in some cultures the 
cluster eventually acquired a considerable size and a vel! 
irregular shape. In many hanging-drop cultures the spot 
appeared imbedded in a bubble or drop of liquid, which fuid 
seemed to disappear when the conidia were green and mature 
The spores were certainly distributed actively, for, as à rule, 
they were found adhering to the cover-slip; and were it merely 
a falling-off of ripened spores, they would have tumbled into the 
water below, but instead they had been shot upwards and had 
adhered to the gelatine surface on the cover-slip from which the 
aerial hyphe were growing—and therefore downwards; but? 
no case was the mechanism of the distribution made out, 17 
could I identify stalks by which the conidia had been attached 
Yet the attachment was firm, for spores adhered when material 
was fixed and preserved in absolute alcohol ; and in material that 
had been teased out and mounted in glycerine they adhered » 
clusters of from four to eight or ten, and all still attached t the 
r 
