3 i8 SCIENCE FROM AN EASY CHAIR 



but if they get on to another, cause deadly destruction of 

 the foliage. It was an otherwise harmless mould, or leaf- 

 fungus, which destroyed the coffee plantations of Ceylon. 

 It had lived in the Ceylon forests on other plants without 

 attracting notice ; but when the coffee tree was introduced 

 and cultivated in large areas, this little fungus seized on 

 it, grew with terrible activity, and received the name 

 " vastatrix " from the botanists who traced its history, and 

 showed that it was the destroyer of the coffee plantations. 

 Hop-growers are constantly contending with these pests 

 in the same way as other growers 

 of crops have to contend with 

 similar pests, but the hop-growers 

 have the more difficult and delicate 

 " patient " to steer through its 

 diseases. The finest kinds of hops 

 are not robust ; it is a chance 

 . ,. . whether or no they will suffer from 



1 V"t"^ I a we ^ anc ^ co ^ season, or other 



^* irregularity of climate, to such a 



degree as to fall ready victims to 

 blight and mildew. Yet they pay 

 better, provided the season is 

 favourable, and so the grower risks 



planting the fine, delicate variety instead of being content 

 with the more certain but smaller profits yielded by a 

 more robust variety of hop. The hop-lice, or blight 

 insects, are destroyed by washing with soft soap and 

 quassia a process requiring, even when a machine is 

 used, a good deal of care and labour. Mildew and mould 

 are destroyed and also prevented by dusting the hop-vines 

 in hot summer weather with finely powdered sulphur. 

 But both diseases can be combated by keeping the source 

 of infection away from the hop-garden. The mould- 

 fungus can be checked by burning all leaves and plants 



FlG. 57. Ordinary wingless 

 female hop-louse, multi- 

 plying parthenogenetically 

 throughout the summer. 



