695 



appears to be still open to question as to how far each of them 

 may be right. The main difficulty seems to be that of securing 

 adequate materials for the determination of varieties, for as 

 reported in Trinidad (Bull. Misc. Inf. Roy. Bot. Gdns. Oct. 1896, 

 p. 206) " plants may well be grown for years without furnishing 

 them and yet be at the same time sufficiently vigorous to ripen 

 good crops of fine edible tubers ; we have ourselves grown in these 

 gardens an experimental patch for several seasons and as yet 

 we have no certain material for the identification of may 

 varieties." In India where at the Royal Botanic Gardens, 

 Calcutta, the systematic study of growing plants made by Prain 

 & Bur kill, is more in advance of that in any other country 

 (Prain, Bengal Plants, ii (1903), p. 1064; Watt, Comm. Prod. 

 India (1908) p. 492) the final report is not yet made. This study 

 is being extended to a monograph of the Dioscoreas from Africa, 

 the West Indies and in general to the whole genus by Sir D. Prain 

 and Mr. I. H. Burkill, for which purpose collections have been 

 specially prepared at the request of the Director, by the Depart- 

 ments of Agriculture, Gold Coast (Tudhope, Ann. Rep. 1916, for 

 1915, p. 13) and Northern and Southern Provinces, Nigeria 

 (Johnson, Ann. Rep. 1917, p. 7; letter to Director, dated 

 Ibadan, 9th Dec. 1919); these have recently arrived at Kewand 

 are now under examination. 



r 



The cultivation of yams is, in general, much the same — ^usually 

 planted on mounds or ridges about 3-6 ft. apart, propagated by 

 means of the bases of the stems, upper portions of the tubers, 

 by aerial tubers, small underground tubers or portions of larger 

 tubers. In Northern Nigeria they are planted from root eyes 



with straw, with 



the 



water between them ; fetakes are put in when plants 

 have made a few feet of growth (Dudgeon, Agric. & For. Prod. 

 W. Air. p. 153). In Trinidad the upper parts of the yam are used, 

 and when well ripened the tuber can be cut into pieces, everyone 

 of which will make a plant — but in this case it is advisable to 

 store them under finely sifted damp vegetable mould or coconut- 

 fibre until they start growth (Bull. Misc. Inf. Roy. Bot. Gdn. 

 Trinidad, 1896, p. 211); in the PhiHppines the basal or upper 

 portion is customarily used and sections or chunks of the cylin- 

 drical rooted varieties weighing from 40-100 grams are regularly 

 used in planting (Barrett, Phihppine Agric. Rev. 1912, p. 69). 

 In India it is preferable to use sets of the underground tuber 



hing 



should 



first year close together to form good plants or heads for the 

 next season (Bull. Trinidad, I.e.); the first year's crop is poor, 

 but the second excellent (Watt, I.e.). 



A rich deep sandy loam, good drainage, average rainfall and 

 thorough tillage are essential. Stakes may be bamboo or anything 

 convenient to make a good support, they sometimes require to 

 be 10-15 ft. high. Catch Crops— as "Coco Yam" {Golocama 



