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Frequently the influence of fertilization is felt beyond the ovary, and other parts of the flower take part in the formation of the fruit, as the floral receptacle in the apple, strawberry and others. The character of the seed-coat bears a definite relation to that of the fruit.
On the other hand, indehiscent fruits discharge these functions for the embryo, and the seed-coat is only slightly developed. Dissemination. Dissemination is effected by the agency of water, of air, of animals and fruits and seeds are therefore grouped in respect of this as hydrophilous, anemophilous and zooidiophilous.
A caulicle. The outer covering is the wall of the ovary, the inner the seed-coat. Bean. A seed covering. Two cotyledons. A caulicle. A plumule. Pea. The same as the Bean. They have also learned how the first leaves in the last three differ from those of the Morning-Glory, being considerably thicker in the Sunflower, and very much thicker in the Bean and Pea.
In albuminous Monocotyledons the cotyledon itself, probably in consequence of its terminal position, is commonly the agent by which the embryo is thrust out of the seed, and it may function solely as a feeder, its extremity developing as a sucker through which the endosperm is absorbed, or it may become the first green organ, the terminal sucker dropping off with the seed-coat when the endosperm is exhausted.
The needs for these are obvious buoyancy in water and resistance to wetting for the first, some form of parachute for the second, and some attaching mechanism or attractive structure for the third. Special outgrowths, arils, of the seed-coat are of frequent occurrence.
Their function is the twofold one of protecting the embryo and of aiding in dissemination; they may also directly promote germination. If the fruit is a dehiscent one and the seed is therefore soon exposed, the seed-coat has to provide for the protection of the embryo and may also have to secure dissemination.
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