468 SCIENCE PROGRESS. 



Malang, Tangerang and Preanger.' Severe penalties have 

 been enforced against planters disregarding the quarantine 

 regulations, and a constant supply of sereh-free plants has 

 thus been obtained to stock the fields and nurseries of in- 

 fected districts. 



6. It is worth while noting, however, that direct attacks 

 upon a parasite are usually futile. It is difficult to point to 

 a single instance in which a widely distributed pest has 

 been stamped out by these means, and it is not usual to 

 pay much attention to a disease until it is widespread. 

 And this has led the students of plant pathology to turn 

 their attention in another direction. Is it not possible so 

 to strengthen the plant as to render the parasitic attacks 

 harmless ? 



This may be attempted in two ways ; by the perfect adap- 

 tation of a plant to its surrounding conditions of growth, 

 and by the encouragement in a plant of some peculi- 

 arity which is distasteful to the parasite. In the former 

 case careful attention must be devoted to external sur- 

 roundings so as to produce healthy, vigorous growth ; in 

 the latter it is necessary to produce a new variety. In 

 nature both of these principles are unceasingly at work ; 

 among cultivated plants it is needful to see that they are 

 not absent. 



7. The choice of climate, class of soil, mode and 

 efficiency of cultivation and manuring require constantly 

 to be considered. 



The cultivation of any plant in a climate unsuited to it 

 produces a weak form liable to disease. The value of the 

 larch as a timber tree has led to its being planted far 

 beyond its natural limits, with the resulting appearance of a 

 dangerous disease — the larch canker. It would be idle to 

 ignore the fact that different varieties of the sugar-cane vary 

 much as to requirements of soil and moisture. While some, 

 such as the Bourbon, are best grown in clayey soils with a 

 considerable amount of rain, others, such as the Transparent 

 kinds prefer a light volcanic well-drained soil. 



The result of crrowincr the much-valued Botirbon in 

 iKobus (4), (5). Werot (i). 



