161 



Eelativel}' thick 



(2 Philippine races) . . . . jf ^^'^f ^ ^^^^ ^'^ 



^ ^ (Invod 280 



In what eastern country Dioscorea esctdenia took its origin, still 

 remains obscure: bnt the demonstration that wild Papuan races 

 exist with characters similar to those of the Philippine wild plants, 

 strengthens the idea that eastern Malaya is perhaps its home. Wild 

 plants fonnd in India and Indo-China wonld then be but relics of 

 ciiltivatiou, — a view reasonable enough until or unless it can be 

 demonstrated that India produces wild races which differ from 

 those there cultivated. Greater thorniness is not dilfereuce enough ; 

 for undisturbed wild plants of the races which produce thorny roots 

 get an accumulation of these thorny roots above them, which gives 

 an impression that they are thornier than neighljouring cultivated 

 races : and it is well to be on guard against a false deduction there- 

 from. 



If left in* the ground over their full time, the new plant 

 depletes the old tubers, and any digging at a wrong season results 

 in a loss of return. It seems that the species as a whole divides 

 the year into about two months resting, and ten months growing. 

 If dug at eight months the yield is relatively small, but the tubers 

 are much l)etter for the table. If dug about two months later and 

 in the resting period which follows the yield is at the maximum. 

 If dug soon after ncAV growth has started the yield may be miser- 

 able. When the race Buga was left in the soil until new gro^i;h 

 had started the return was 500 grammes per root instead of 2000 

 to 3000 : and when left two months longer it was 1700 grammes. 

 So also with other races. It is recognised that some races mature 

 a little earlier than others ; but as yet exact information is not avail- 

 able. 



The return of the lesser Yam is less than the return of Dios- 

 corea alata after the same number of months of growth. 



var. spi/iasA. 



1 Lobed tuber of the race Tuqui 274 ; 2 3 Sausage shaped tubers of the 

 races Bulucan Yam 276 and Tuqui 278; on the right the large tuber of " Buga." 



