LIFE-HISTORY OF HEMILEIA VASTATRIX. 327 
If the above be correct, it should follow that J uly, or there- 
abouts, would show a wide-spread and sudden outbreak of the 
yellow disease-spots ; and we know that such is the fact. 
In August the leaves, destroyed by the abundant mycelium, 
fall in showers, the trees becoming in many cases almost stripped. 
One set of observations may be recorded as typical of all the 
others*. A coloured ribbon having been loosely tied on a twig 
of the growing coffee, the development of the buds and leaves 
was carefully watched, and notes made of the changes which 
occurred from time to time as the latter passed from their 
earliest stages to adult age, and finally died off. 
In the case which I will here cite, the terminal bud commenced 
to open about March 21st, and in a few days had developed a pair 
of shining, dark green, tightly apposed young leaves about 
4 inch long. 
During the first three weeks in March, a continuance of dry, 
hot days caused all quiek growth to cease; but the opening of 
the bud commenced at once after the showers which set in 
towards the end of March, and continued for the most part 
throughout April. 
On April 2nd, in fact, after a week of showery growing- 
weather, the swollen bud had burst, and presented two leaves 
each š inch long; and by April 25th these were fully formed, 
handsome bright-green structures, about 45 inches long by 21 
inches broad in the middle. On or about this date the leaves 
ceased to enlarge, and may be considered adult and in full working 
order. 
During the last week in April and the first week in May much 
rain fell in heavy showers; but from May 8th to May 25th a 
hot period intervened, the mornings being frequently close and 
steamy, however. Atthis time a few spots of “ leaf-disease ” were 
observable here and there on surrounding coffee-trees. 
Now, from April 25th, the period at which we may consider 
the leaves adult, to June 1st no trace of Hemileia was discovered 
on either of the leaves ; but on June Ist a distinct, though small 
“ pin-spot ” was seen on one of the leaves, which I shall call the 
left-hand leaf; and on June 3rd a few spores were seen proceed- 
ing from this. On the latter date also I found a minute yellow 
* pin-spot " on the right-hand leaf of the pair. 
* For further evidence cf. Third Report. 
