FORM AND LIFE. 



527 



tlie word ; for it is connected by continuity with all the heads of 

 wheat that preceded it and with all those that will follow it. The 

 important part is the seed, or the germ which it includes, continu- 

 ing itself by a stem and a flower into another seed like it. The 

 root, the straw, the glumes are accessories all to be abandoned 

 every year by the seed incessantly reviving of itself, which veri- 

 tably incarnates the species wheat. 



The molecular movement being at the very basis of life, to 

 what extent does it regulate its manifestations ? Does it make its 

 influence felt only to maintain the external form or to exert a cer- 

 tain amount of command upon it ? It does command it in effect, 

 and all the external characteristics of the species and the individ- 

 ual appear to us definitely as subordinated to the conditions of 

 their inner chemistry. Chevreul was the first who formulated 

 the principle of the absolute dependence of life on the physico- 

 chemical laws of inert matter. The demonstration of it is fur- 

 nished in the manure and fertilizers by means of which we suc- 

 ceed in prodigiously modifying the external appearance of the 

 plant, to the point of rendering it almost unrecognizable. This 

 sprout, in a dry, arid soil, is stunted, coriaceous, and hairy ; that 

 other one, from the same kind of seed, growing in the shade, on a 

 soil constantly moist, is large, plump with water, soft and smooth. 

 Without more knowledge, we should see in them two distinct spe- 

 cies, if all the intermediate terms did not meet here and there on 

 grounds half dry or half shaded, to show that we are simply deal- 

 ing with two individuals of the same species, the molecular con- 

 stitution of which is not absolutely identical because of the differ- 

 ent conditions in which each one has lived. 



It was long thought that the plant could choose by its roots 

 the substances in the earth useful in its support and growth. This 

 is not correct. The root, in contact with the extremely complex 

 bodies which are continually formed and unformed in the soil 

 around it, takes all those which the spongy terminal tissue of each 

 radicle can dissolve. The plant is in this case only a reagent like 

 any other ; it is passive, and suffers itself to be penetrated by every 

 substance, useful or injurious, in the quantity in which that sub- 

 stance is susceptible of mingling and combining with its super- 

 ficial tissues. By virtue of the molecular constitution of the walls 

 of the root, and especially of the extreme cells of their fibers, plants 

 absorb particular mineral principles, and these principles in their 

 turn, drawn into the vital molecular movement, favor it, impede 

 it, or modify it in some way, and at last provoke a perceptible 

 change in the aspect of the plant. This direct, immediate influ- 

 ence of molecular constitution on the forms of living beings ap- 

 pears to be more sharply marked in plants, but that is perhaps 



