THE VEGETABLE CEIL. 93 



from starch, we are ignorant from what other compounds all 

 these constituents are derived ; yet there can be no question that 

 theii' hydrogen is originally obtained from "water, and tliat their 

 origin is connected with a separation of oxj^gen. It is remark- 

 able of many of them, especially in the formation of essential oils, 

 how much their production is favoured by the action of strong 

 sunlight. 



The compounds containing nitrogen stand in opposition to those 

 devoid of it. Though in quantity they may stand far behind the 

 latter, their importance in the vital phenomena of plants is not 

 less ; nitrogenous substances, as we have seen, line the cell as the 

 prhnordial utricle, and consequently the contents of the cells are 

 ordered under their immediate influence ; they originate the de- 

 velopment of new cells, and set in action the decomposition of 

 carbonic acid. Doubtless these constitute but a few fragments of 

 the great part wliich these substances play in the Living plant ; for 

 many chemical processes, such as fermentation, the formation of 

 hydrocyanic acid and amygdalin, the conversion of starch through 

 diastase, &c., indicate that the iirst impulse to the transformation 

 of all vegetable compounds, is principally given by the proteine 

 substances. The great importance whicli these substa^nces have in 

 the vital economy of plants, is also denoted by their anatomical 

 conditions, since they are contained in great abundance in all 

 organs destined to farther development, and which are endowed 

 with more important physiological activity ; e. </., in the points of 

 roots, in leaf and flower-buds, pollen-grains, the embryo-sac of 

 the ovule, and in seeds ; while in old organs, principally employed 

 in conveying the sap, they occur in far inferior quantity. 



It is as good as certain, fi-om what has been stated above, that 

 ammonia in combination with organic substances fornishes the 

 nitrogen requisite for the formation of the proteine substances. 

 In what organs and under what conditions these compounds are 

 formed we know not. Mulder ^"P%s. Ghem.") is of opinion that 

 they are formed at once in the points of the roots, and are dif- 

 fused from here over the rest of the plant. But a determined fact 

 may be opposed to this view, namely, the occurrence of salts of 

 ammonia in ascending crude sap, which rather indicates that the 

 formation of nitrogenous compounds takes place chiefly, if not en- 

 tirely, in the leaves. 



Of the formation of the other nitrogenous compounds of plants, 

 such as the vegetable alkalies, indigo, &c., and of their import to 

 the plant, we know simply nothing ; I therefore consider it super- 

 fluous to make any further observations on them here. 



e. Secretions. 



In the consideration of the nutrient process of plants, the ques- 

 tion presses itself upon us, whether, in the series of true formations 

 which the mutual action of the substances contained in the plant 



