160 



time without uprooting the plant whieh like the " Cut-aud-come- 

 again 3'am "' of the West Indies goes on growing. In the race 

 ■" Buga," the tubers are ]n'oduced very diffusely upon the ends of 

 certain relatively long slender roots of which they are the terminal 

 parts. But as the slender part does not die at the end of the 

 reason a new plant springing from the spot where the old plant 

 stood exhausts the diffusely produced tubers through their "stalks"; 

 and the diffuseness does not lead to a crop of new plants radiating 

 from the old centre, unless pigs or some other animal or some 

 accident may have l)roken the connection, in which case the isolated 

 tuber gives origin to a new plant upon its own account where it lies. 

 Diffuseness, therefore, is iiot an immediate means of dispersal but 

 a guarantee against animals uprooting all the tubers and so des- 

 troying the plant com])letely. 



So far the Pa})uan races have shown themselves less diffuse 

 than ■•' Bnga."' 



The duration of the growth of these wild races Avould seem to 

 be aljout ten moiiths, when " Buga," for instance, may return two 

 and a half, three or even four kilos by weight of tubers per hill, not 

 edible tubers, but tubers too stringy for the ta])le. The yield of 

 edible tubers should be taken at an earlier date and would be less. 



Of the cultivated races, ""' Kiioai tu bua " in character of its 

 tul)ers a])proaches the wild races, but yet is quite distinct. It 

 yielded large returjis at longer periods than did the Avild races, — a 

 matter for study. 



In classifying the races it is convenient to put it A\-ith the 

 wdld races thus: — 



Few and large tubers, 

 Tubers rooty. 



Tubers roundish, on long stalks . . Buga 284 

 Tubers roundish, on short stalks . . Tailukava 428 

 Tubers similar but- more elongated . . Deba .432 

 Tubers not rooty. 



Tubers turni]j-like tapering or toed . . Memu 424 

 Tubers flattened and lobed . . . . Khoai tu bua 288 



More numerous and smaller tubers. 

 Tubers lohed, rooty 



fMoa alu 286 

 (2 Indian and 1 Pliilippine race) . . ^Goradu 296 



[Tugui 274 



(Tugui 278 

 "jPora alu 300 



(2 races of Indo-China) 



Tubers sausage-shaped 

 Tubers rooty 



(1 Indian and 1 Philippine race) . . ]p^"^ ^^■^J q 



Tubers not rooty 

 Eelatively thin 



