Vegetable Physiologn. 413 



the agency of the nitrogenous principles ; that the latter conse- 

 quently are the primary substances in vegetable assimilation. The 

 question then arises, Hoav and where are these nitrogenous prin- 

 ciples produced ? From the presence of the protoplasmic matter 

 abundantly in rootlets, from its existence in quantity in Fungi and 

 in other plants grown without access of light, we ai'e led to think 

 favourably of Mulder's opinion that these matters may be formed 

 directly in the roots of plants ; the recent experiments of Bous- 

 singault, of growing plants in sand, with only mineral sub- 

 stances, where the use of nitrate of soda caused a production 

 of nitrogenous principles equal to what would have been obtained 

 in a fertile soil, seem to show that as a rule the nitrogenous sub- 

 stances are taken up by the roots, and the ijrotoplasm may be pro- 

 duced there from nitrates or ammoniacal compounds. 



The further question then presents itself, How do the ternary 

 compounds originate ? Judging from anatomical investigation, 

 we may answer, from the albuminous substances, but in what 

 manner, and where, we are not prepared to say. The hesitation 

 with regard to these points arises from the changeable and ubi- 

 quitous characters of these ternary principles. Yet we have some 

 data. There is certainly strong negative evidence afforded in the 

 inability of Fungi, colourless parasites, and etiolated plants, to pro- 

 duce any considerable development of cellulose in their texture, 

 or, as regards the Fungi, of starch-granules in their cells. Nitro- 

 genous substance is found abundantly in these cases, but the 

 cellulose products are weak and perishable. If the protoplasm 

 had the power of assimilating carbonic acid and water without 

 the peculiar solar action which causes tlie green colour of 

 chlorophyll, we do not see why there should not be abundance of 

 cellulose, &c., in those cases where nitrogenous matter abounds. 

 There is reason to think that organic compounds are taken up in 

 these instances to afford material for the production of the cellu- 

 lose ; and this seems to be borne out by the influence of humous 

 substances in the manure applied to turnips. But ordinary plants 

 do not form their due quantity of cellulose, starch, &c., unless 

 they receive the influence of light, causing a green coloration of 

 their foliage. 



Our attention is thus directed to the chorophyll granules, as 

 the agents of assimilation of the ternary substances ; those 

 granules formed of " protoplasm," which, under the influence of 

 light, become impregnated with a waxy matter containing a green 

 colouring principle. We know that this matter is produced in 

 proportion to the amount of solar action, provided a sufficient 

 supply of nitroyenons matter is afforded to the roots; further, 

 that the quantities of ligneous cellulose, starch, oil, and the more 

 highly carbonized essences, resins, &c., are all similarly pro- 



