194 



A point worthy of notice is that the " Agromyza '" fly is there 

 still quite manifest", and every morning, it can he seen in numbers 

 flitting round and al)0ut the plants which it still damages to some 

 extent: the pest has not died, l)ut it has been completely prevented 

 from laying its eggs in the young stems. The saving of llu' leaves, 

 whicli it perforates to a state of fine lace, is not, by any means, an 

 easy matter, but failing tuba-root, it is hoped, by menus of sulphur 

 dustings in the early mornings, gradually to overcome it. 



The Tuba-plant " Derris elKptica : " in Malay Akar Tuba, a 

 loguminosc, may be seen growing in the Economic (iardcns, as a 

 low l)ush, l)ut it is a climbing plant with a short trunk and long 

 trailinii' l)ranches. The root system is extensive and among the 

 bundles of " al-ar tnha" sold in Chinese shops, pieces of root 8 feet 

 long are not uncommonly found. In digging for roots in the 

 Economic Gardens, the longest, so far found, was 5 f eei; in length : 

 this shortness may be due to the unsuitability of the soil in which 

 it grows — a soil too sandy to retain moisture in hot dry weather. 

 According to a Chinese informant, tuba should be planted not 

 far from water, which attracts tlie roots, thus favouring early deve- 

 lopment, and more fre(iuent cuttings. 



It is to be noted that the trials related in the Journal of Agri- 

 cultural I'esearch were made with dried imported roots, which 

 implies, judging from tlie eifects recorded, that it loses none of its 

 ])()teiu-y ])y keeping. 



Long tables are given in the course of the article with details 

 of tests of tuba root applied as a dry ])o\V(k'r and as a s])rav mixture 

 with and without soap. 



Tlie following extracts are taken from this i)ai)er. A test was 

 made of the eft'ects of tul)a as a contact poisoii on Aphids, with a 

 spray mixture of 1 pound of ])Owder to lOti gallons of water with 

 the following results: 



Percentage of Aphids living on plants at the end of 



