250 Dawson—On the Biology 
with the excretion of fluid drops so often seen in Fungi when 
spores are being initiated, e. g. in Pilobolus. The phenomenon 
seems to partake of the nature of root-pressure in higher 
plants, occurring as it does at a time when a considerable 
supply of food material would be required from the sub¬ 
stratum ; it is at present, however, without any adequate 
explanation. 
The natural substratum being horse-dung, it is not im¬ 
probable that cellulose, or some product of its fermentation, 
is utilized by the Fungus; hence the later stages in the culti¬ 
vation of these stromata were carried out on cotton-wool, 
thoroughly soaked with an extract of horse-dung, since after 
several days 5 culture on gelatine this medium was completely 
liquefied. An agar medium proved much less suitable than 
cotton-wool, probably owing to the rapidity with which the 
former dried up; on the contrary, cultures transferred from 
agar to cotton-wool at once began to grow vigorously and 
to send up new stromata. 
From the earliest stages these stromata appear to be 
strongly apogeotropic; after a month or six weeks it was 
found that growth was more rapid at a temperature ranging 
from io°-i3°C. than from 15°-!8°, and again, that increased 
aeration of the cultures led to increased development, both 
in respect to the strength of the stromata and to the rate 
of growth. 
With regard to the effect of injury to any part of the 
Fungus, it may be mentioned that in every case, when any 
portion of a stroma was cut off, e. g. the apical part of the one 
to the extreme left of Fig. 4^, for purposes of investigation, 
the cut surface of the stalk invariably grew out and formed 
a new stroma, which frequently developed into a specimen 
as strong as, or even stronger, than the one cut off. (See 
Fig. 6, a-d, which represents the development of the left- 
hand stroma of Fig. 4^, after the removal of the slightly 
swollen head.) 
