252 THE CANADIAN NATURALIST. [Sept. 



the roots may, and often do, contain a sufficiency of phos- 

 phates for maintaining unchanged the composition of the 

 plant, and yet the addition of phosphatic manures produce 

 a vastly increased yield. The only rational explanation of 

 these facts, and that which the researches of agricultural 

 chemists appear to corroborate, is that the phosphates, besides 

 forming important elements in the actual material of the 

 plant, are also able to act as carriers of the requisite nourish- 

 ment to the growing parts ; and that, just as, in the animal 

 economy, certain substances, as, for example, the salts of 

 iron, give a tone to the system by aiding the powers of 

 secretion and cell-formation ; so, in the vegetable world, and, 

 more especially, in the important families of Graminace^e and 

 Leguminoe, phosphoric acid stimulates the assimilative powers, 

 excites an increase of vitality, and, in consequence, augments 

 the fecundity of the germ, and enlarges the proportional rate 

 of increase. The consideration of certain analyses of Woods, 

 pubhshed in the first volume of Dr. Percy's Metallurgy, and 

 also of a series in Emmons' Report on the Geology of South 

 Carolina for 1858, pp. 59-78, (and also the second series 

 of Table I., ante p. 8) has led me to this conclusion ; for 

 such analysis shew that the twigs and leaves are richer in 

 phosphates, and other mineral elements, than the bark or the 

 solid wood; whilst, in the cotton-plant, Crace-Calvert has 

 shown that more soluble acid-phosphate of magnesia exists 

 in the pod, than in the husk or stalk.* 



From Table I., it will be seen that, whilst the ashes of 

 solid oak contain 4*5 per cent, of phosphoric acid, the 

 quantity present in those of the young twigs amounts to 

 12*7 per cent., or more than 2*75 times the proportion 

 present in the wood. 



Those parts, therefore, which are pre-eminently in a state 

 of rapid development, are the most abundantly furnished with 

 phosphates, doubtless, having their own peculiar functions to 

 perform in assisting the developmental process. 



As to the manner in wliich plants derive their saline eon- 



Brit. Assoc. Eep. 1869. 



