LIFE-HISTORY OF HEMILEIA VASTATRIX. 801 
and nights prevent dangerous evaporation or radiation, though 
boisterous winds may injure the tender shoots mechanically. 
About the end of the last or beginning of the next of our 
arbitrary periods, ¿ e. July to September, the S.W. monsoon 
sets in, accompanied by continuous and heavy rains and winds; 
July and August are frequently characterized by fine hot weather, 
with alternate showery and cloudy intervals, the S. W. wind 
becoming more gentle and continuous; while September com- 
monly ushers in another warm damp period, when moulds and 
mildew luxuriate in the steamy atmosphere. 
In the fine weather, which usually characterizes great part of 
the next three months, the “ pieking of crop ” is carried on; the 
trees become weary, so to speak, as their last fruit ripens, and 
little more growth is noticeable after November; the leaves 
formed in September have attained their full size and normal 
dark colour and leathery texture, and a state of comparative rest 
i8 characteristie of December and January. 
Having premised these facts, the importance of which will be 
more evident as we proceed, I may sketch in a similarly general 
manner the phases of the malady known as “ Coffee-leaf disease ” 
as they commonly occur in the districts named. From the 
middle of January to the end of March the orange-red “rust” 
spots, so characteristic of this disease, are either altogether absent 
or rare; during April and May the spots occur here and there, 
chiefly on the older leaves, and very rarely on the young ones. 
In June and July the great and disastrous annual "attack of 
disease” usually becomes manifested by the myriads of yellow 
spots breaking forth from the leavesin all stages, each producing 
its masses of orange-red “rust ;” and from this time forwards, 
until the dry weather is again fairly set in, the disease is con- 
stantly present, fluctuating in intensity according to circumstances. 
It generally happens, indeed, that another severe “ attack of the 
disease ” occurs about December or January; and in rare cases, 
as in wet ravines, the disease-spots do not completely disappear 
all the year round. 
It became an important part of my duty to ascertain clearly 
what conditions influenced the rise and fall, so to speak, in the 
virulence of the disease; it was therefore necessary to obtain 
an accurate knowlegde of all the circumstances affecting the life 
of the fungus causing the latter. 
Having ascertained that the spore (“ uredospore ”) of Hemi- 
LINN. JOURN.—BOTANY, VOL. XIX. 2c 
