590 M. BIOT ON APPLYING CIRCULAR POLARIZATION TO THE 



withers and become.* yellow in its turn, while the superior part which 

 is still green continues to nourish the ear, as is well known to agricul- 

 turists. This fact, taken in conjunction with the preceding results, ex- 

 plains several practices in agriculture, and shows in what their good 

 effects consist. 



Thus when the base of the stem is withered, if the Cerealia be cut 

 before the grain is ripened, it continues to receive nutriment and to be 

 ripened at the expense of the stem, as if it still remained adhering to 

 the soil. When the stems are dry the grain may therefore be brought to 

 maturity without its being exposed to the losses of spontaneous shedding ; 

 at least Avhen there is reason to hope that the rains will not fall and 

 destroy it upon the earth, upon which it has been prematurely ex- 

 tended. The advantages of thus anticipating a retarded harvest have 

 been enlarged upon by skilful agriculturists, and the application of the 

 principle has been commenced. 



Secondly, since the leaves and stems of green plants form sugar 

 and other soluble carbonated products, which are to be absorbed by 

 the seed, which, as I have just stated, occurs in wheat, rye, and, as 

 I have ascertained, in several other herbaceous plants, as well as in the 

 leaves of exogenous trees, if they are buried in the earth in that state 

 of verdure, it is evident that they will enrich the soil with all these 

 products, so eminently conducive to the nourishment of the young plants 

 to be produced from it. Now since it is proved by experiment that the 

 green parts of vegetables decompose the carbonic acid of the air and 

 appropriate the carbon, it becomes infinitely probable that this absorp- 

 tion contributes to form the mass of their saccharine and gummy pro- 

 ducts, in addition to the juices which they may draw from the earth by 

 their roots ; and this probability is increased when we see how consi- 

 derably the carbonated products of the leaves differ from the products 

 of the stems, which derive their aliment more particularly from the 

 earth. It is then the natural and legitimate conclusion that one part 

 of the solid mass of plants is furnished during their life from the car- 

 bon of atmospheric air, so that by burying them green in the earth more 

 is rendered to the soil than it has yielded. 



Those only who are versed in chemistry and vegetable physiology 

 can enter deeply into the grand phaenomena of the absorption and fixa- 

 tion of atmospheric principles in plants, whether immediately by their 

 own organs or by the intermediation of inorganic substances capable of 

 absorbing those principles, and of afterwards conveying them to plants 

 in tlie nascent state. The application of lime in this mode of interme- 

 diate action has already been suggested, and my own observations fur- 

 nish evidence in confirmation of the propriety of the suggestion. Pro- 

 bably analogous (ft'ects of absorption and successive transmission may 

 be produced by other substances, cither upon the carbonic acid or the 



