87 



3. a Hai-nan Yam. i)robablv D. belophi/Uoidex, I'rain and 



Burkill. 



4. an xVfrican Yam, D. dumetorum, Pax. 



5. an Indian Yam, D. //entapli.ylla, Linn., var, Linnnei, 

 Prain and Burkill. 



6. a Malayan Yam D. peniapliijlla, Linn., var. malaica, 



Prain and Burkill. 



7 and 8 Pliilip])inc Yams, D. pcntaphi/lla, Linn., var. and 

 an ally. 



Dio.scorea ahita. Linn., wliicli of all species is the yam most 

 cultivated in Lido-Malaya, was the subject of an article in the last 

 issue of the Bulletin. It is cultivated in Africa ; but it is apparent 

 that the Portuguese who iised it for provisioning their ships on the 

 return journey from India deliberately introduced it at their ports 

 of call on the coast of that continent, not so much because they 

 could not get yams in various parts of Africa, as because it was 

 their wont to introduce everywhere everything, whether animal or 

 vegetable, that might become useful. It is not intended to deal 

 here with the races of Dioscorea (data now in Africa, but with other 

 species only, and firstly with that Dioscorea which appears always 

 to have had the greatest importance upon the Guinea coast and to 

 be native. No botanical nanie will be given to it; but it will be 

 called the White or Eight-months Guinea vam. Plate vi, illustrates 

 it. 



1. TlIK WlIITI': 0I{ ElGHT-MOKTIlS GUINEA YaM. 



This White or Eight-months Guinea yam has very many races 

 in its own home. A glance at the plate shows that the tubers in 

 some are more elongated than in others. Some, also, more al)un- 

 dantly than others have them protected by thorns on the roots : and 

 -agtiin variation also appears in the foliage as the annexed outline 

 drawings show. To enumerate the races is out of the question, and 

 even, to suggest a scheme for a classification of them is difficult. 

 Therefore little will be said about their differences. 



The tuber of this species has a skin of a dark khaki colour in 

 nil the races that have been grown, with white flesh under it ; and 

 if there is any sign in the cells of a sul)stanee with a magenta 

 colour it is to be foufid only about the base of the stem at the top 

 ■of the tuber. The surface of the tuber is generally rather free from 

 rootlets and nearly smooth. The tubers may grow as twins or in 

 small grou])s. 



When the new stem appears above ground, it is thick and of 

 a rather livid colour, with abumlant prickles, and pairs of la,rge 

 broadly ovate bracts from the axils of which strictly at right angles 

 stout rapidly ta])ering branches arise. It is obvious that these 

 branches by their position and tlieir rigidity, serve the purpose of 

 preventing the stem from slipping back through the tangled thickets 

 in which it would grow naturally. 



Soon the bracts give place to ])aired leaves, and the stem be- 

 comes less prickly, until it is quite unarmed. 



