OUTLINES OF BOTANY. 



14. The Seed. 



161. The Seed is enclosed in the pericarp in the great majority of 

 flowering plants, called therefore Angiosperms or angiospermous plants. In 

 Conifera and a very few allied genera, called Gymnosperms or gymnosper- 

 mous plants, the seed is naked, without any real pericarp. These truly 

 gymnospermous plants must not be confounded with Labiates, Boraginece, 

 etc., which have also been falsely called gymnospermous, their small nuts 

 having the appearance of seeds (158). 



162. The seed when ripe contains an embryo or young plant, either fill- 

 ing or nearly filling the cavity, but not attached to the outer skin or the 

 seed, or more or less immersed in a mealy, oily, fleshy, or horn-like sub 

 stance, called the albumen, or perisperm. The presence or absence of this 

 albumen, that is, the distinction between albuminous and exalbuminous seeds, 

 is one of great importance. The embryo or albumen can often only be found 

 or distinguished -when the seed is quite ripe, or sometimes only when it be- 

 gins to germinate. 



163. The shell of the seed consists usually of two separable coats. The 

 outer coat, called the testa, is usually the principal one, and in most cases 

 the only one attended to in descriptions. It may be hard and crustaceous, 

 woody or bony, or thin and membranous (skin-like), dry or rarely succulent. 

 It is sometimes expanded into wings, or bears a tuft of hair, cotton, or wool, 

 called a coma. The inner coat is called the tegmen. 



164. The funicle is the stalk by which the seed is attached to the pla- 

 centa. It is occasionally enlarged into a membranous, pulpy, or fleshy ap- 

 pendage, sometimes spreading over a considerable part of the seed, or nearly 

 enclosing it, called an aril. A strophioleor caruncle IB a similar appendage, 

 proceeding from the testa, by the side of or near the funicle. 



165. The hilum is the scar left on the seed where it separates from the 

 funicle. The micropyle is a mark indicating the position of the foramen of 

 the ovule (133). 



166. The Embryo (162) consists of the Radicle or base of the future 

 root, one or two Cotyledons or future seed-leaves, and the Plumule, or future 

 bud within the base of the cotyledons. In some seeds, especially where 

 there is no albumen, these several parts are very conspicuous, in others they 

 are very difficult to distinguish until the seed begins to germinate. Their 

 observation, however, is of the greatest importance, for it is chiefly upon 

 the distinction between the embryo with one or with two cotyledons that are 

 founded the two great classes of phaenogamous plants, Monocotyledons and 

 Dicotyledons. 



167. Although the embryo lies loose (unattached) within the seed, it is 

 generally in some determinate position with respect to the seed or to the 

 whole fruit. This position is described by stating the direction of the 

 radicle next to or more or less remote from the hilum, or it is said to be 

 superior if pointing towards the summit of the fruit, inferior if pointing 

 towards the base of the fruit. 



15. Accessory Organs. 



168. Under this name are included, in many elementary works, van out 

 external parts of plants which do not appear to act any essential part 

 either in the vegetation or reproduction of the plant. They may be classed 

 under four heads : Tendrils and Hooks, Thorn* and Prickles, Hairs and 

 Gi+ndt. 



