LIFE-HISTORY OF HEMILEIA VASTATRIX. 323 
coffee ; the necessary conditions for their germination are known 
to recur naturally at frequent intervals; and experiments have 
conclusively shown that within three weeks from the successful 
sowing of any spore on a coffee-leaf the mycelium reproduces 
spores again, to go through the same cycle. 
Moreover, evidence has been brought to show that any kind of 
coffee may become infected, though of two given leaves the 
younger and thinner one usually shows the “ disease-spots ” more 
rapidly. How far do these and similar facts explain what occurs 
on masses of coffee ? 
I have shown in detail elsewhere * that in the districts chosen 
for illustration, young coffee-leaves are formed most rapidly 
during the “ growing weather” of April to August, and that, prac- 
tically, the quickest development of new leaves occurs during 
May and June. On the contrary, very few leaves are produced 
during the hot dry season of February and March. Alterna- 
tions of rapid and slow growth occur during the rest of the year, 
depending on the variations of climate experienced; but it com- 
monly happens that a rapid renewal of growth occurs towards 
the end of the year, in October and November. 
To determine as far as possible the rate of growth and other 
changes in leaf-buds and leaves at Pérádeniya, certain trees were 
selected in August 1880, and watched during the following twelve 
months, notes being made at short intervals as to the conditions 
of the buds and leaves on twigs around which coloured ribbons 
had been loosely tied. 
The shortest time in which a pair of leaves was developed in 
my experiments was about 4 weeks, when the bud first exposed 
on April 10th became an adult pair of leaves by May 8th; and 
the longest period occupied by the same process was (excluding a 
very abnormal example, where 173 weeks were occupied in the 
process) 18 weeks, when a bud which first appeared free on 
October 29th did not begin to open until the following January, 
and its leaves were not fully formed before February 27th. 
During the very dry weather experienced in Pérádeniya from 
December to March, there is, on the whole, much less activity 
displayed in the formation of leaf-buds and leaves than during 
the period from April to August; and this is in accordance with 
the general experience of planters on the Kandy side of Nuwara 
Eliya. Of course there are differences in the rate of develop- 
ment of leaves, dependent on circumstances other than the 
* Appendix to Third Report. 
