Vol. jit. No. 293. 



THE AGRICULTURAL NEWS. 



235 



breast high, the results of the treatment will be more 

 satisfactory than if the work is carried out when the canes 

 are taller. 



DESTUUCTIOX i>K KGC.S. 



After each brood of froghoppers, the dry leaves on the 

 growing canes should be examined for eggs, and if these are 

 found in numbers the dry leaves should be removed and 

 thrnwn into the cattle pens, where the eggs will be destroyed 

 by the trampling of the animals. As an alternative, the trash 

 might be stacked on the bare ground, where, if the eggs 

 batch, the larvae will not be able to find food. 



The removal of the egg-bearing trash should be 

 accaniplished as soon as possible after the eggs begin to 

 appear, since these hatch during the wet season in about 

 three weeks after being laid. 



PREPARATION OF PLANTATION PARA 

 RUBBER: A REPLY. 



In the A'jncull-ural News, Vol. XII, Xos 289 and 

 290 were published two articles summarizing a recent 

 bulletin on the preparation of plantation rubber, by B. J. 

 Eaton, Chemist to the Department of Agriculture, F.M.S. 

 In this, attention was given, amongst other matters, to the 

 fact that Eaton's results on the maximum quantities of 

 coagulants required for Hevea late.v diti'ered markedly from 

 those obtained previously in Ceylon, by Parkin. 



In view of this fact, and also because, in general, 

 Eaton's paper appears to deprecate the Ceylon investigations 

 referred to, I'arkin has lately published a reply and retros- 

 pect on the subject in the India Ruliher Journal (June 7, 

 1913). 



An account is given first in this article of the conditions 

 under which the Ceylon (1898-99) experiments in question 

 were conducted. At this time, little previous work 

 had been done on Hevea; indeed it was a period 

 when attention was being given mainly to the culti- 

 vation of Castilloa under plantation conditions. Wound res- 

 ponse had not been scientifically recognized, and consequently, 

 the latex used in the experiments was obtained mainly 

 from initial tappings of Hevea trees, and was thicker and 

 •contained a larger percentage of caoutchouc than that 

 procured in ordinary estate practice to-day from successive 

 tappings rendered possible by wound response. Such latex 

 from initial wounds may be more alkaline than that from 

 subsequent tappings, and therefore require more acid 

 for coagulation. A further condition of importance noted 

 is the fact that the laboratory arrangements in Ceylon 

 at that time were limited, though as pointed out, 

 a plea of this kind will not serve to cover the wide dis- 

 crepancy between Eaton's figures for acetic acid and those of 

 Parkin, even though the figures were originally stated as being 

 only approximately true. Another circumstance which might 

 have atl'ected the results was that I'arkin used latex that was 

 kept undiluted. According to Whitby, the development of 

 natural acidity takes place much more rapidly in diluted 

 than in undiluted latex. Lastly, Parkin intimates that his 

 idea of what actually constituted a complete coagulation does 

 not agree with the somewhat loose definition advanced by 

 Eaton. 



Coming to the main points of the dispute, they may be 

 grouped under four headings, and discussed in order. 



(1) The amount of acetic acid required to bring about 

 ■complete coagulation. 



Eaton found that only about a tenth of the quantity 

 -recommended in the Ceylon experiments is required. 



Parkin's reply is that for reasons already touched upon Jvbove, 

 his latex contained less natural acidity. 



{2) Is the amount of acid required independent of the 

 dilution of the latex:' 



In Parkin's experiments, dealing mainly with acetic acid, 

 the conclusion was reached that the amount of acid required 

 depended upon the original quantity of latex present and noti 

 upon the dilution. Eaton found otherwise — the more the 

 dilution the more acid is needed per unit volume of original 

 latex Both Crossleys and Whitby's results on the same 

 subject agree with those of I'arkin, and evidently the matter 

 demands reinvestigation. In concluding his discussion of 

 the point in que.stion. Parkin reproduces some of Eaton's 

 figures to show that they disagree with that investigator's 

 statement, that the greater the dilution the greater is the 

 actual amount of acid that must be added to bring about 

 complete coagulation. 



(3) The percentage range or the minimum and maxi- 

 mum of acid for complete coagulation. 



In connexion with this point, Eaton denies that 

 there is a maximum figure for either acetic or other 

 coagulant beyond which coagulation is incomplete, in 

 spite of the fact that Parkin, Crossley and Whitby have 

 shown independently that there is apparently an absolute 

 maximum for acetic acid, while only a relative one for hydro- 

 chloric acid and sulphuric acid. 



(4) The theory of Hevea latex coagulation. 



Under this heading Parkin discusses views on the subject 

 in general. He maintains that the presence of protein is an 

 important factor in coagulation, and likens latex to milk, in 

 that just as the coalescence of the fat globules and the 

 curdling of the protein are distinct, so in latex the segrega- 

 tion of rubber globules and the actual clotting of latex are 

 equally separate transformations. 



VVithout mentioning Eaton's paper. Parkin concludes: 

 'it may be emphasized that by no means has the last word 

 been said on the coagulation of latex. The subject still 

 awaits complete elucidation. 



Ventilation and Fruit Storage —Since fruits 



produce carbon dioxide very rapidly, and since they brown 

 and lose their flavour when they are not supplied with 

 oxygen, the need for thorough ventilation during storage 

 becomes apparent. Piespiration of ripe fruits as well as thit 

 of green fruits is rapid, though fruit tissues that respire as 

 actively in the absence of air as in the presence of air seemed 

 to be those that have finished their growth and are ripe. If 

 growing tissues, such as green peaches, are put in an 

 oxygen-free place for a few days and then brought back into 

 air, the rate of production of carbon dioxide does not entirely 

 return to the normal. This would indicate a permanent 

 injury to the protoplasm or to some of the enzymes due to- 

 insutticient oxygen. In this connexion it may be noted that 

 the so called 'ice scald' injury is due to the same cause, 

 brought about by an accumulation of carbon dioxide within 

 the paper wrappers in which fruit is stored. The question 

 of wrappers for fruits would appear to be a matter 

 worthy of an extended investigation from the standpoint of 

 ventilation. Wrappers allow only a very small air space 

 around each fruit. Some type of perforated or porous 

 wrapper has been suggested as a possible means of combining 

 the desirable qualities of the wrappers with better ventilatioa 

 tion of the fruit. (From Bulletin 330 of the Agricultural 

 Experiment Station of the College of Agriculture, Cornell 

 University.) 



