THE RESERVE MATERIALS OF PLANTS. 65 



may be seen to be accompanied by quantities of proteid 

 substance. Taking young cells near the apex of the shoot 

 the special cells contain the hydrocyanic acid alone, showing 

 that it precedes proteid in the time of its occurrence. A 

 little farther back the proteid can be detected, and gradually 

 as sections are taken at increasing distances from the apex 

 it increases in amount while the acid diminishes. As the 

 active life of the cells becomes less and less vigorous, the 

 proteid becomes more and more preponderating in the cell 

 contents, and ultimately cells are found which contain 

 proteid only, the hydrocyanic acid having all disappeared. 

 The same succession of events can be seen if the develop- 

 ment of the pericyclic fibres be traced towards the apex of 

 the stem. 



There seems from these observations to be very strong 

 reasons for supposing that hydrocyanic acid is a nutritive 

 substance and leads at any rate in these plants to the 

 formation of proteid. 



Treub holds that this is its immediate function ; he 

 believes it to be primarily formed in the leaves, principally 

 in the basal cells of the hairs and the idioblasts with calcic 

 oxalate in the epidermis of the leaves. Thence it makes 

 its way to the conducting tissues of the bast and pericycle 

 and travels to the apical meristems. It is thus primarily a 

 body originating only in the constructive processes, and not, 

 as in the cases of the almond and cherry laurel, the product 

 of a decomposition of a glucoside. Indeed Treub says very 

 emphatically : " L'acide cyanhydrique du Pangium edule 

 n'est pas un produit de decomposition ou de desassimila- 

 tion," basing the statement on both indirect and direct 

 arguments. The former are founded on the localisation of 

 the product in the bast and pericycle and its evident trans- 

 portation by the bast tissue. The latter involve the 

 consideration of its localisation with a material which 

 serves as a temporary proteid reserve in the same elements 

 of the tissues, and the order of appearance and disappear- 

 ance of the two substances in such special cells. 



That hydrocyanic acid can subserve not only the for- 

 mation of temporary reserves of proteid but can be used, 



5 



