198 THE FOOD AND NUTRITION OF PLANTS. 



respect altered when Starch is produced. In that case, the direct 

 product of assimilation in the form of dextrine, instead of being 

 immediately appropriated in growth, is solidified in the starch- 

 grains, and in that compact and temporarily insoluble form accu- 

 mulated as the ready prepared materials of future growth (81). 

 So, also, when Inuline is formed instead of starch, as in the roots 

 of Elecampane (Inula Helenium) and the Dahlia, and the tubers 

 of the Jerusalem Artichoke : here the dextrine is solidified into a 

 substance intermediate in its properties between dextrine and cel- 

 lulose, which is closely analogous to starch, and subservient to the 

 same purpose. Notwithstanding the difference in their properties 

 and chemical reactions, these various products are strictly isomeric, 

 that is, they consist of the same elements, combined in the same 

 proportions ; and physiologically they are merely different states 

 of one and the same thing. Dextrine is the most soluble state 

 (dissolving freely in cold water), and that originally formed in as- 

 similation in the foliage : starch and inuline are two temporarily 

 solidified states, and cellulose is the ultimate and usually perma- 

 nent insoluble condition. Accordingly, whenever the materials of 

 growth are supplied from such accumulations of nourishment, as 

 especially from the seed in germination, from fleshy roots (128), 

 rootstocks (174), tubers (175), &c., the starch or inuline is dis- 

 solved in the sap, being spontaneously reconverted into dextrine, 

 &c., and attracted in this liquid state into the growing parts, where 

 it is transformed into cellulose, and becomes a portion of the per- 

 manent vegetable fabric. 



350. Assimilated matter also occurs in the sap under the still 

 more soluble form of Sugar (84). If we suppose this to be a di- 

 rect product of the assimilation of carbonic acid and water, the 

 amount of oxygen gas exhaled will be just the same as before. 

 For sugar has the same elementary composition as dextrine, starch, 

 and cellulose, with the addition of one equivalent of water in the case 

 of cane-sugar, and of three more in that of grape-sugar.* If, as is 

 more probable, sugar is a subsequent transformation of dextrine, 

 then the latter has only to appropriate some water. In the forma- 



ters acted upon in assimilation are at first as much deoxidized as in chloro- 

 phyll, since these general products of vegetation have immediately to absorb 

 oxygen enough to bring them to the form of dextrine, starch, cellulose, &c. 

 * The formula for cane-sugar is C 12 , H 11 , O 11 ; for grape-sugar, C 12 , H 14 , O' 4 . 



