148 Controversial Questions. 



plants by carefully selecting the twigs which were to be 

 used as cuttings. His plan was to look over a plant for 

 any leaves which showed even the slightest indication of 

 variegation and then to make cuttings from the buds in 

 the axils of these leaves. The leaves gave the promise 

 of a higher degree of variegation, and justified it by en- 

 abling Salter to put several varieties on the market. 



The same principle has recently been applied with the 

 most satisfactory results by J. Kobus in the cultivation 

 of sugar cane in Java.^ There are great difficulties in 

 the way of propagating the selected plants sexually in 

 this case, the most serious of which is that the best kind 

 of all — the Cheribon cane — is sterile. Kobus, therefore, 

 sought among the best varieties that which was richest 

 in sugar and only used this to take cuttings from (such 

 cuttings are called bibif in Java). But all the specimens 

 of a single variety are, in this case, obtained by vege- 

 tative methods, so that every variety is, as we have ex- 

 plained above (pp. 84-85) a single individual. The cut- 

 tings from individuals rich in sugar give rise to rich 

 canes. This method insures, in the first place, the elimi- 

 nation of the less valuable plants in a very simple and 

 effective manner, and in the second, the use of the very 

 best canes as breeding material : moreover the yield is 

 much more quickly and much more simply increased 

 than by the ordinary method of selection. 



To sum up : I claim that I have shown that there is 

 a complete parallel between partial and individual varia- 

 bility; and that both are brought about by the same 

 causes. These are external ; they are to be found in the 

 amount of light and of moisture and in such other fac- 

 tors as would be placed in the category of "nutritional" 



^ ArcJiief voor lava-Suikerindusfric, 1898, Nr. 16, 1899, Nr. 15-16. 



