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It is quite possible that the spores of Hemileia might be carried to* 

 Kew on seeds, or in ordinary correspondence, or in the clothes of 

 travellers, just as they have been carried to Fiji and elsewhere, and 

 just as they may at any time be carried to Jamaica by globe-trotters 

 landing in Kingston and making an excursion to the Blue Mountain 

 Peak. 



But precautions are taken with plants and seeds at Kew, which 

 cannot be taken with excursionists to the Peak, so as to prevent any 

 risk. 



But assuming that the ordinary precautions of a scientific estab- 

 lishment like Kew were unavailing and that some traveller from Cey- 

 lon, to take an absurdly extreme case, had actually infected Coffee 

 plants destined for Jamaica with Hemileia spores, the conditions of the 

 temperature and moisture of the air in the plant houses at Kew are the 

 most favourable to the germination of the spores, and spores that 

 remained inactive so long as they were quite dry would within 48 hours 

 grow in the presence of moisture and heat in those plant houses. Any 

 which fell on the soil or on the wooden sides of plant-cases would 

 germinate exactly in the same way as they would on the Coffee leaf, 

 but their existence would be terminated as soon as the nutritive sub- 

 stance of the spore was exhausted I may illustrate this by reminding 

 you that a Coffee seed may germinate, and will grow, producing leaves, 

 in pure sand and pure water as long as the nutritive material of the 

 seed is available, but as soon as this is used up in the growth, the 

 young seedling must die unless it is planted out in soil. Just in the 

 same way spores of Hemileia will inevitably germinate, given the fa- 

 vourable conditions, and will as inevitably die, unless the spores are 

 actually on the leaf of a coffee plant, and penetrate the " breathing pores." 



Supposing that some of these spores have fallen on the leaves of a 

 Coffee plant in the Kew plant-houses. They will germinate probably 

 in 12 hours. If they have not germinated within 48 hours they are 

 dead and will never germinate. From their germination to the 

 " diseased spot" making its appearance on the leaf, the time varies from 

 8 to 19 days, 13 or 14 days being the usual time. 



Plants would be kept in Wardian Cases at Kew before despatch to 

 the Colonies long enough to ascertain and to make sure that they had 

 contracted no disease and were perfectly sound and healthy 

 But even if such precautions were not taken, and the plants became 

 infected on the very day they were leaving Kew, the disease would 

 liave developed by the time they had arrived in Jamaica, and would be 

 so evident to the naked eye that the plants would be immediately 

 destroyed on opening the Wardian Case at Hope Gardens. 



The spores of Hemileia can only infect Coffee through the "breath- 

 ing-pores" of the leaf. They may germinate in any other position, but 

 invariably die, even on the leaf, if the germinal tube does not, in its 

 growth, come across one of the " breathing pores" and penetrate it. 



You allude to the plant-diseases known as " smut" and " ergot." The 

 life-history of smut in corn is of quite a different character, being 

 specially adapted to the life-history of the plant it attacks. The 

 spores cling to the seed, and remain in the ground at rest like the seed 

 itself until the latter germinates. The spores germinate at about the 

 same time as the seed, and although the germinal tubes are unable to 



