THE RESERVE MATERIALS OF PLANTS. 63 



In the face of the problem of the utilisation of the bodies 

 resulting from the action of emulsin upon amygdalin great 

 importance must be ascribed to the recent work published 

 by Treub on the occurrence and meaning of hydrocyanic 

 acid in the tissues of Pangium edule (65), one of the 

 Bixacese. This compound, according to the author, does 

 not occur as a glucoside, but in the free condition, and is 

 present in relatively large amount. Greshoff found more 

 than 1 per cent, to be hydrocyanic acid of the dry weight 

 of the plant in one sample among many others analysed. 

 A brief resumi, of the author's conclusions seems not to be 

 out of place here, as throwing light upon the question of 

 the nutritive value of the glucoside of the laurel. Indeed 

 it seems not improbable that the hydrocyanic acid itself may 

 be regarded as, in some cases at least, a reserve material. 



Treub has made a careful investigation into the 

 localisation of this principle in the plant, using as his 

 method the reaction given in the formation of Prussian 

 blue when hydrocyanic acid comes in contact with a ferric 

 salt in the presence of hydrochloric acid. The reaction is 

 very distinct and takes place well in the interior of the 

 cells, causing those which contain the hydrocyanic acid 

 to stand out with great distinctness. 



In the whole of the adult axis, both stem, root and 

 peduncles, he finds it to exist in quantity in the conducting 

 tissue of the bast and pericycle. In the leaves it is still in the 

 same regions, but is more widely spread, nearly all the 

 parenchymatous tissue of the blade containing more or less 

 of it. The epidermis especially is noteworthy, showing it 

 present in the basal cells of the hairs which the leaves bear, 

 and in certain idioblasts which contain also crystals of 

 oxalate of lime. In the young fruits and those which are 

 growing a considerable quantity is present, partly in the 

 bast and partly in parenchyma outside the conducting tissue. 

 In the seeds there is an accumulation in the peripheral 

 layers of the endosperm and in other cells of the same 

 tissue abutting on the embryo. 



In these regions, and in the cortex, and sometimes the 

 pith of the axis, Treub describes the hydrocyanic acid as 



