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It can be shown that plants most widely different in habit and general appearance, and having strongly marked differences in every part of the flower, even in the pollen, in the fruit, and in the cotyledons, can be crossed. Annual and perennial plants, deciduous and evergreen trees, plants inhabiting different stations and fitted for extremely different climates, can often be crossed with ease.
During the process of "sweating" the cotyledons of the cocoa-bean, which are at first a purple colour and very compact in the skin, lose their brightness for a duller brown, and expand the skin, giving the bean a fuller shape. When dry, a properly cured bean should crush between the finger and thumb. Finally the beans are turned on to a tray to dry in the sun.
They had analysed soils, estimated the rainfall, and examined the germination of seeds; they understood such mysterious terms as bacteria, protozoa, cotyledons, trenching and ridging, cross-fertilization and spermatozoids, and had some elementary acquaintance with the theory of the rotation of crops.
It will be a drop of water upon the unfolding cotyledons of a seed just peeping up out of the ground, which will percolate below after you have gone away, and give the little roots a new impulse of growth.
For brevity's sake all these cleft and ternate, double cleft and quaternate cotyledons and even the higher grades are combined under one common name and indicated as tricotyls. A second aberration of young seed-plants is exactly opposite to this. It consists of the union of the two seed-leaves into a single organ. This ordinarily betrays its origin by having two separate apices, but not always.
In the Sunflower the true leaves are nearly the same shape as the cotyledons, so that this is an especially good illustration for the purpose. Thus, without any hint from me, my pupils often write of the Bean, "it has two thick leaves and two thin leaves." In this way the Bean and Pea present no difficulty.
By this inconvenient the cotyledons of her matrix were presently loosed, through which the child sprang up and leaped, and so, entering into the hollow vein, did climb by the diaphragm even above her shoulders, where the vein divides itself into two, and from thence taking his way towards the left side, issued forth at her left ear.
I consider this the best order to study the seeds because in the Morning-Glory the cotyledons are plainly leaves in the seed; and in the Squash or Sunflower the whole process is plainly to be seen whereby a thick body, most unlike a leaf, becomes an ordinary green leaf with veins.
Compare these parts with the Morning-Glory, Sunflower, Bean, and Pea. Where is the food stored? How many cotyledons have Corn, Wheat, and Oats? How many have Bean, Pea, Morning-Glory, and Sunflower? Compare the veins of the leaves of each class and see what difference you can find. This will bring up the terms dicotyledon and monocotyledon. Di means two, mono means one.
In cows, and other ruminating animals, the internal surface of the uterus is unequal like hollow cups, which have been called cotyledons; and into these cavities the prominencies of the numerous placentas, with which the fetus of those animals is furnished, are inserted, and strictly adhere; though they may be extracted without effusion of blood.
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