Page:Popular Science Monthly Volume 50.djvu/115

Rh derived from plants reverting to the parental characteristics, as sometimes happens in imperfectly fixed hybrids.

When flowering takes place in good weather, fecundation goes on regularly, and the chances increase of obtaining a good crop. These chances, on the contrary, diminish when the earing occurs in a rainy time. Probably water gets within the involucre, and the wet pistils imperfectly retain the pollen grains, or their germination is irregular, the pollinic branch not reaching the micropyle, and the ovules not being fecundated; and the ears bear many sterile flowers in which the corn is not formed.

The production of the corn, of the seed which assures the perpetuity of the species, is the ultimate end of the herbaceous plant; it is essential that the reserve stores necessary for its development be accumulated around the embryo inclosed in this seed, and that it find everything near by: the starch which it will liquefy and then transform into cellulose; the gluten, the nitrogenized matter, with which it will form the protoplasm of its cells. These reserves must be abundant, so that a part of them may be burned, producing by their slow combustion the heat which favors these transformations. The whole life of the herbaceous plant tends toward this end of accumulating in the seeds the principles elaborated during its short existence; and it is precisely this accumulation in the seed of the gluten and the starch, both excellent food-stuffs, for which men have cultivated wheat from the most remote antiquity; or, if they live in different climates from ours, sow other corn plants—rice in the extreme East, maize in America—in order to find in their seeds the association of nitrogenized matter and starch which gives the grain so pronounced an alimentary value that it forms an essential part of the food of a large proportion of the inhabitants of the globe.

It is easy to follow the migration of the nitrogenized matter, phosphorus, and potash from the lower to the upper leaves, and from these to the end of the stem and the seed. The transportation of these principles has been studied for more than thirty years by a distinguished agronomist, Isidore Pierre, professor in the Faculty of Sciences at Caen. We are less well informed concerning the formation of starch. It can not be seen accumulating in the leaves of wheat as in those of a large number of other species, nor are reserves of saccharine matters found in these leaves. The formation of starch is very late, as it does not take place till during the last stage of vegetation. It thus happens that the quantities of starch contained in the grain vary greatly from one year to another.

The phenomenon of transportation and migration of