KEY. It. ABBAY ON HEMILEIA YASTATRIX. 183 



the fungus can infect the leaf that the stoniates should be in a spe- 

 cially favourable condition for receiving the infection (a condition 

 perhaps only occurring in certain states of the plant), this might 

 be the reason why in the midst of such countless multitudes of 

 spores every coffee-leaf is not covered with " disease " spots. On 

 the other hand, it may be due to the fact that for some obscure 

 reason only a very small proportion of the spores will germinate. 

 It is also possible that my inability to grow the red sporanges is 

 due to the fungus requiring some other tree or plant on which to 

 develope before it is able to infect the coffee-leaf ; but this is 

 improbable. 



In more than one district it has been noticed that a strong wind 

 has apparently had a great effect in carrying the " disease " up or 

 down a valley, most probably by spreading the spores from some 

 badly infected estate over the comparatively healthy ones. If 

 such is really the case, the fact points to the conveyance of the 

 disease, as suggested before, to the tree through the stomates of 

 the leaf and not through the roots. It might be possible under 

 such conditions to moderate the virulence of the pest in some of 

 the more isolated districts if all the proprietors tcould combine to 

 gather and burn, at the commencement of the chief annual attack, 

 all the diseased leaves and twigs that at present are allowed to lie 

 on the ground beneath the trees until they decay. Such a plan 

 would no doubt be expensive ; but it would certainly destroy 

 vast number of spores, and might sensibly reduce the virulence of 

 the "disease." The sprinkling of quick-lime on the ground 

 beneath the trees has, in one instance at least, proved beneficial ; 

 and as it would no doubt destroy all the spores it came in contact 

 with, it is not improbable that the two remedies, if applied simul- 

 taneously, might be found in some degree successful. The trees 

 should also be washed with some suitable disinfectant, and the 

 watering of the ground about the trees with the same disinfectant 

 might possibly prove more beneficial than sprinkling with lime. 

 It would be of little or no use for one planter in a district to 

 attempt these remedies if the others did not — the spores produced 

 on a single badly diseased tree being so enormously numerous, 

 that a whole estate of healthy plants might easily be infected by 



single unhealthy plant in their neighbourhood. 



It has been asserted at various times that " native/' i. e. un- 

 pruned and uncultivated coffee, as well as plants of the Liberian 

 species, are exempt from the attacks of Hemileia vastatrix. This 



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