Chap, hi.] VEGETAL ASSIMILATION AND DISASSIMILATION. Ill 



procures it in another way. In general, as we have seen, the 

 nutritive substances absorbed by the roots are very rich oxygenised 

 compounds ; on the contrary, the assimilated substances, forming 

 a large portion of the dry matter of 'plants, are either poor in 

 oxygen, or do not contain it at all. Assimilation must then be 

 specially an act of dis-oxygenation ; now we know that it takes 

 place particularly in the chlorophyllian cell. We have then here, 

 as Sachs justly remarks, the place, the conditions, and the time 

 of this dis-oxygenation.' 



In fact, it is in the chlorophyllian cells that assimilation, or 

 rather the vitalization, of various substances introduced into the 

 plant takes place. It is towards this living and active laboratory 

 that they converge ; it is there that they enter into conflict with 

 each other. The chlorophyllian cell is a powerful apparatus of 

 synthesis, effecting organic combinations which still defy the 

 power of contemporary chemistry. The molecules of azote, 

 carbon, oxygen, hydrogen, &c., penetrate the cellular cavity, some 

 free, others entangled in combinations more or less complex. 

 There they are mixed together, dragged into the circular current 

 of the cellular protoplasm, subject to the attraction exercised 

 upon them by the chlorophyll, and, on the other hand, shaken 

 by the undulations of the yellow rays of solar light which add 

 their impulsion to the vibrations by which they are already 

 animated. The atoms and the molecules yield to these united 

 influences ; those particles which are involved in combinations 

 abandon them, resume their liberty, and all unite to form living 

 organic substances, ternary and quaternary substances. 



We have already said a few words upon the advent and aspect 

 of one of these substances, one of the most important in vegetal 

 physiology, starch. Starch is especially formed in the green cells, 

 and even in the interior of the chlorophyllian bodies. We have 

 seen that its formation is in direct dependence upon the chemical 

 operation of the ■chlorophyll, consequently upon light. It 



' J. Sachs, loe. df., p. 821. 



