Xxii OUTLINES OF 



allied genera, called Gymnosperms, or gymnospermous plants, the seed is naked, without 

 any real pericarp. These truly gymnospermous plants must not be confounded with 

 Labiatce, Boraginea, 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 filling or nearly 

 filling the cavity, but not attached to the outer skin or the seed, or more or less im- 

 mersed in a mealy, oily, fleshy, or horn-like substance, called the albumen, or p en- 

 sperm. The presence or absence of this albumen, that is, the distinction between al- 

 buminous and exalbuminous seeds, is one of great importance. The embryo or albu- 

 men can often only be found or distinguished when the seed is quite ripe, or some- 

 times only when it begins 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 case9 the only one attended 

 to in descriptions. It may be hard and crustaceous, woody or bony, or thin and mem- 

 branous (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 placenta. It 1 

 occasionally enlarged into a membranous, pulpy, or fleshy appendage, sometimes 

 spreading over a considerable part of the seed, or nearly enclosing it, called an aru. 

 A strophiole or caruncle is 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 coty- 

 ledons that are founded the two great classes of phseuogamous plants, Monocotyledon 

 and Dicotyledons. Cotyledons are said to be conduplicate when folded once length- 

 wise ; contortuplicate when variously folded or twisted ; conferruminate when ao 

 united that no line of separation can be traced. 



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

 in some determinate position with respect to the seed or to the whole fruit. This 

 ]K>sition 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 <» 

 the fruit, inferior if pointing towards the base of the fruit. 



§ 15. Accessory Organs. 



168. Under this name are included, ya many elementary works, various 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, Thorns and Prickles, Hairs and Glands. 



169. Tendrils (cirrhi) are usually abortive petioles, or abortive peduncles, or some- 

 times abortive ends of branches. They are simple or more or less branched, flexibly 

 and coil more or less firmly round any objects within their reach, in order to suppM* 

 the plant to which they belong. Hooks are similar holdfasts, but of a firmer conau- 

 tence, not branched, and less coded. 



170. Thorns and Prickles have been fancifully called the weapons of plan 1 * 

 A Thorn or Spine is the strongly pointed extremity of a branch, or abortive petiole, f 

 abortive peduncle. A Prickle is a sharply pointed excrescence from the epidermis, 

 and is usually produced on a branch, on the petiole or veins of a leaf, or on a peduncle. 

 or even on the calyx or corolla. When the teeth of a leaf or the stipules are pungent- 

 they are also called prickles, not thorns. A plant is spinous if it has thorns, acule"' 1 

 if it has prickles. 



