396 



l)efore a.^fciidiiiy'. The scfondarv tii])crs produced later all ascend- 

 ed. The surface of these tuhers is rather rooty: the flesh is white 

 hut there is a very distinct layer with magenta sap under tlie skin. 

 The average yield in 1916 was 9 lbs. 8 oz. (4309 grammes). 



Race Xo. ;34 ]X)Ssesses tlie same habit of turning upwards l)ut 

 instead of producing one long tuber and a few -much shorter 

 secondary tubers, it prodiues several similar tubers which do not 

 attain {iny great length. It was figured on p. 301 of the Bulletin 

 under the Xo. 4. It yielded on the average 3 lbs. 15 oz. (178G 

 grammes) in 1910. 



Tlie bottom figure of plate 6 represents race X"o. 72 which be- 

 haved in a different way to the others, in that it grew upwards 

 first and tlien obliquely downwards or else horizontally as is there 

 shown. Its flesh is white, l)ut with a distinct layer holding magenta 

 sap under the skin: its skin is rather rooty. The a\erage yield in 

 1910 was 6 lbs. 13 oz. (3100 grammes). 



Plate 6 shows the yam beds, and in the lower block the supports 

 of wood which had to be used to build up the mounds for the earth- 

 ing of Xos. 38 and 72. The yams it will be observed are allowed 

 poles to grow over about eight or nine feet high. 



Tliere is some diversity in the leaf characters of these up- 

 growing yams: foi' Xos. 28, 34 and 38 have the auricles of the 

 hirgest leaves rounded : hut the others have them more or less 

 subacute. .Vone have thorny stems. 



T. H. BURKILL. 



THE LESSER YAM — DIOSCOREA 

 ESCULENTA. 



The lesser Yam, here illustrated by three plates, is quite un- 

 like the Greater Yam in foliage, and in the production of many 

 relatively small tubers. Economically it is less im])ortant: it is 

 less widely known, less extensively grown, and has not been carried 

 across oceans to the remote islands and continents which the 

 (ireater Yam has reached. Fiji for instance, seems to be its east- 

 ward limit, whereas the CTreater Yam has l)een taken to the eastern- 

 most islands of the Tacihc; and Mauritius seems to i)e its western 

 limit, whereas the Greater Yam has reached Africa and has been 

 carried also to the Tropics of the Xew World. 



As far as can be guessed, its domestication had beginnings 

 not less remote than tlie Greater Yam's, or perhaps even more 

 remote: for the seed-forming habit has been eliminated from it 

 quite as much as from the Sugar-cane and the Pineapple; it has 

 for instance, never been known to fruit, which the Greater Yam 

 does at rather rare intervals. Moreover its parentage is much more 

 obscure than that of the Greater Yam. 



*Onciis esculentus, Loureiro : Dioscoven nndeota, Linnaens iii 17.54, but 

 not in 1753 : D. fasciculata, Roxljurgh. 



