66 FUNCTION OF LATEX 



laevo-methylinosite. This substance was found to occur 

 to the extent of 046 per cent, in the latex of the tree 

 from which the rubber was obtained. Its presence in 

 fine hard Para from South America was also proved.* 



Mineral Matter. — A portion of the mineral matter 

 present in the latex invariably finds its way into the crude 

 rubber and is left in the form of ash when the rubber is 

 incinerated. The quantity of ash in plantation Para 

 rubber does not usually exceed 0'5 per cent., whereas m 

 the case of rubber prepared by natives, such as Landolphia 

 balls, there may be ten times this amount or even more, 

 owmg to the admixture of earthy impurities. According 

 to Henriques, the bases usually present in the ash of 

 rubber are lime, magnesia, alumina, and iron. Spence 

 has recorded that the ash which he obtamecl from a 

 sample of the latex of Funtumia elastica contained potas- 

 sium, iron, calcium, and magnesium, which were present 

 in the latex chiefly as phosphate, sulphate, and oxalate ; 

 the total amount of ash was 0*266 per cent, on the latex 

 and more than three-fourths of it consisted of soluble 

 potassium salts. 



Function of Latex. — In concluding this chapter a brief 

 summary may be given of the views which have been 

 advanced as to the function of latex in the plant. In 

 the first place it may be again noted that latex is not 

 universally met with in plants, but is confined to certain 

 orders only, so that it cannot be regarded as essential to 

 plant life. Again laticiferous plants differ widely in 

 character and in the conditions under which they grow, 

 and as we have ah-eady seen, some of them produce a 

 rubber-yielding latex whereas others do not. The latex 

 is therefore very variable in composition, and it is possible 

 that its function may not always be the same in every 

 plant. 



It has been suggested that the latex serves for the 

 purpose of storing water for use by the plant during 

 drought, and this may perhaps be true of those laticiferous 

 plants which inliabit countries havhig a well-marked 

 dry season. Many laticiferous plants, however, are 

 found in countries and situations where there is always 

 abunchiut moisture, and in these cases it would appear 



* Sco pfiprr by S. S. Pickles and B. W. \Vliitfoild in Proceedings 

 of the Chemical Society, 1911, vol. xxvii. p. 54. 



