326 MR. H, MARSHALL WARD ON THE 
weather, since the time at which pruning, manuring, &c., are done 
affect these and other phenomena; moreover, since the buds are 
slower in development where winds or a general low temperature 
prevails than where the air is quiet and warm, it will be evident 
that elevation affects this as other processes of growth. The trees 
on which my observations were made, suffer much from leaf-disease, 
and bear little crop, circumstances which must also be taken into 
account. 
Let us now suppose, for the sake of argument, that a quantity 
of spores of Hemileia are scattered about the above-named 
districts in January, after the dry season has fairly set in; many 
of these spores may be imagined on the rocks, ground, tree- 
stumps, &c. around, while others are on the leaves of the coffee. 
The air is so dry that, except on the banks of sheltered streams 
and in damp shady places, those spores cannot germinate; the 
wind is not high, and even in cases where sudden gusts raise 
spores from dead and “ diseased” leaves on the ground, there 
are comparatively few leaves on the trees, and the chances of 
many spores attaching themselves to their dry surfaces are not 
great. 
With the April rains and gusty winds there come in circum- 
stances which distinctly alter the circumstances of these spores: 
a few of these spores on the leaves germinate, infect the leaves, 
and in three weeks reproduce their kind in the normal manner. 
By the time that the May leaves are becoming formed, a some- 
what larger stock of Hemileia-spores exist on the trees than 
before; and these newly-formed spores are better placed for 
distribution—every shower of rain and puff of wind must scatter 
some of these spores. 
During May and June the weather is not unfavourable for the 
germination of the above-named spores; by the time that this 
second generation has gone through its cycle, the older spots are 
still producing vigorous spores in the moist atmosphere, while 
the wind may successfully place others from the original sources 
of infection. 
It must be remembered that the trees are by June becoming 
densely clothed with young, succulent foliage, and that the 
spores from the more recently developed spots-are more likely to 
be deposited on the leaves, since they are more numerous. The 
life-cycle of these later spores may be more rapid by several 
days in the tender young leaves, in the moist, warm atmosphere. 
