590 + M. BIOT ON APPLYING CIRCULAR POLARIZATION TO THE 
withers and becomes 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 when 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. Nowsince 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 aaycialieas 
can enter deeply into the grand phenomena 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 the 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 effects of absorption and successive transmission may 
be produced by other substances, either upon the carbonic acid or the 
