Vol. XVIII. No. 459. 



THE AGRICULTURAL NEWS. 



3«I 



VARIATION IN HEVEA BRASILIENSIS. 



A pape' of consideriblo import mc i and iaieresC to 

 those engaf^ed ia the Para rubber industry has been 

 published in the Annals of Bo/any, Vol. XX.KIII, No. 

 CX.\.'iI, July 1919, p. ;}i;), by ' Mr Stafford Whitby, 

 M.Sc, A.K.C.S , of McGill University, Montreal, Canada. 



Tlie piper 'inbudies ili-^ results of th'^ observations 

 made by the author ir the Federated .Malay States, as to 

 the extent to wliicli variatiin o'lcurs in the ainmnt of rubber 

 yielded by individual trees of flc7>cti /irasilieiisis of the 

 same age and growing under the same conditions. He also 

 investii^ited the possible orrel aion b-tween the yield of 

 rubber and the girth of the trunk. S^me 1,000 trees, seven 

 years old, in a normal plantation covering about, 13 acres 

 vpere caretiilly studied, the trees being in iheir third year 

 of lapping. As the Eastern plantati::ns have been made 

 with trees raised from nnn-seleced s?9d, the results of the 

 investigation are of particular iiUer--r. Gr-ac variations 

 vfere found in the rubber conten'. of the latex (the 

 ' strength ' of tl^e latex) from diffyn^nt trees, and appeared to 

 be constant and characteiistic for the individual tree. Some 

 trees yielded only l'3 grms. of rubber per 100 c.c. of lato^, 

 while at the other extreme, trees were found yiel ling as 

 much as .j4-5.5 grms. of rubb'i- per 100 c.c. of latex, the 

 mean for the 24?) tree.s examined in this connexion being 

 36'5c5 gims. per 100 c.c. 



The author concludes from his observatims on older 

 trees, that as a tree grows older the rubber content of the 

 latex yielded by it increases 1-2 per cent, per annum. The 

 results are .'et out in tabular form, and wrhile only relatively 

 few tree^< show the lo»er percetit 'ges of from 2.'5-2y grms., 

 and the higher from 44 5.5 grms,, the majority yield amounts 

 varying from .SO^S grms 



With regard to yield of rubber, it was found that 

 individual trees were comparative'}- constant, and from obser 

 vations extending over two year.i, it is stated that a tree 

 which was found to be a high yielder at one time could be 

 relied upon to give a high yield at all tioa-'S. The yield- 

 •results are summarized in a table and by means of a curve, 

 and embody the examination of 1,011 seven-year-oil trees. 

 The mean yield in grammes per itay came t'^ T'lJ grmn . 

 but 8"me few trees yielded more than 2~ grms a day, and 

 fur a large number the yield was from 2 giins. Tlius from 

 96 per cent of the total numb-r of trees 2?5 percent, of 

 the total yield was lottributed, while I3'7per cent. (0'2 

 grm.=. group) only gave 29 per cent, of the yield, and 

 cer'.anly did not rep^y the co^t of tapping. Fmr out-tan line 

 trees in the plantation gave 41 •4.5, 41 o(J, 41 '72, and 42 77 

 .grms per d«y 



The great pos.sibilities of .seed seltction in improving 



rubber yield ate v. ly clearly indicate 1 from those figures 



A further important observation in conoexi m with seed 



selection to which -Mr. Whitby draws attention, is that the 



■ 8<-eds frini any one tree are exactly similar in appearance as 



regards tint, mottle pattern, and shape. 



It now remains to be seen whether seeds from a ligh- 

 yielding tree will give lise to trees similar to the parent. Tnis 

 is hardly likely to he the oise under present plantation 

 conditions, where high- and low-yielding trees are indiscrimi- 

 nately ii.termixed. But it does seem to be indicated ih-it 

 if hi!:h virlding trees can be segrega'Mi, and provided that 

 pollen ot poor-yielding trees be prevented a-cess to the 

 flovters, sctds cap.ible of produ'-in^ irces jielding a hieh 

 percentage of rubber would be a'suied. 



The author also gives jiarticuUrs of the corre'ation be 

 tween yield and girth, which indiciite that though there is 

 a deHnile corrrlatioD— trees wiih a lar^e tmnk beiii.' good 



yielders and those with small trunks being poor yielders — 

 it is not sufficiently well indicated to be of great value in 

 eliminating trees from a plantation. 



It is of interest to notice that A. A. L llutges 

 ('•Sclectie en Uitdunning,' .■X.rchief voor de Itubber cuUurer, 

 11)19, 3, pp. 10-"j-2.'J) has made ol).-,ervaiions in Sumatra 

 in full accord with those of .Mr. Whitby, and linds that 

 'good trees remain good, poor trees remain poor.' ( Krora the 

 Ktui Bulletin of Mitcellaneous In/ormaiion, No. S of 1919.) 



INCREASING THE YIELDS OP TOMATOES. 



An abstract in the Eipririmcnt Hl<itiiin lUi.urd, 

 Vol. XL No. 9 rleal.s with hiiid pollination of fcoinitoes, 

 and .shows that this method, if carefully carrieil out, 

 give.s increased yields to an extent than should pay 

 handsomely. In connexion with incroasing the yield 

 of tomatoes, see al.so the' Arjrtci'J.lnnU Ncwh, Vol. 

 XVII, p. 4. 



If ind pollination of flowers has reduced the number of 

 unfruitful blossoms from 00 per cent, to 20 per cent, of the 

 total number of fl iwers produced, the pErcenla<e of reduction 

 depending upon the cunipirative thoroughness of the polli- 

 nation For various causes diffieul. to contr d. when work- 

 ing with a large number of blossoini, a reduction below 20 

 percent, of unfrdtful blnssomH s-emel to be impossible. 

 The averig • fruitfulness in typical plants of fifteen crop< of 

 tomatoes was 72 per cent, for pollinated blossoms and 36 

 per cent, for unpollinated blosjomi. Tne average yields for 

 pollinated a^d unp >llinated plmts were 7-taid 4'4 lb of 

 tomatoe.s, respectively. The perciniage of fruitfulness and 

 unfruitfniness of individual clusters ot a crop given 8pe;:ific 

 treatment varied to a considerable extent, but total and 

 average records indicated a remark ible mean of per':entage 

 of uniformity of all clusters. 



Of various methods of pollination tried, the emascu- 

 lation method has been more widely used than any other, 

 and is recommended principiUy because of ease in applying 

 pollen, ptevention of duplicttion of pollinaion, and thor- 

 oughness of application a', a time when ihe flower is most 

 receptive. Details developed at the station in using the 

 em'sculation method arn described. 



Hand pollination of blosioms stimulated early develop- 

 ment of the fruit as r.i.npired with naturally pillina^ed 

 blossoms. Fruits produced from h md pollinated flowers 

 have been liarveste 1 as etrly as twenty one d.iys bifore 

 fruit from plaits n >c a-ri'i:iilly polinitel. The author 

 p lin's out thit the cost of pillinilioa for the entire season, 

 which was approxims-tely i:- per plant, may be covered 

 by increi.sed yields from p illinated pUnts in the first two 

 w-eks of harvesting, when higher prices prevail. The 

 coiupirative net returns of pUnts after deducting the cost nf 

 p-)llination show an increased value of from lOc. to b7c. a 

 plant or an averai-e of 3Sc. a plant for pfjllination. 



It is pointed o it that whereas regularity and thorough- 

 ness of pollination are . onducive to high plant yield, 

 inexperienced labour, haste, and irregularity in doing the 

 wirk may not produce orofitable net results. 



No. 3 of the '.studies of Tropical .Vmeri'in Phimegrnu-, 

 issued by the United States National Hirbarium, ba« been 

 received ThiS and previous issues contain imp-.iriint keys 

 to ppecies, and the description of many species regarded aa 

 new. 



