XXIV INTRODUCTION. 



164. The funicle is the stalk by which the seed is attached to the placenta. It is 

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

 ing over a considerable part of the seed, or nearly enclosing it, called an aril. A stro~ 

 phiole 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 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 t inferior if pointing towards the base of the fruit. 



§ 15. Accessory Organs. 



168. Under this name are included, in 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, flexible, 

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

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

 tence, not branched, and less coiled. 



170. Thorns and Prickles have been fancifully called the weapons of plants. 

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

 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, acitleate 

 if it has prickles. • 



171. Hairs, in the general sense, or the indumentum (or clothing) of a plant, in- 

 clude all those productions of the epidermis which have, by a more or less appropriate 

 comparison, been termed bristles, hairs, doivn, cotton, or wool. 



172. Hairs are often branched. They are said to be attached by the centre, if 

 parted from the base, and the forks spread along the surface in opposite directions ; 

 plumose, if the branches are arranged along a common axis, as in a feather ; stellate, 

 if several branches radiate horizontally. These stellate hairs have sometimes their 

 rays connected together at the base, forming little flat circular disks attached by the 

 centre, and are then called scales, and the sui*face is said to be scaly or lepidote. 



173. The Epidermis, or outer skin, of an organ, as to its surface and indumentum, is 

 smooth, when without any protuberance whatever. 



glabrous, when without hairs of any kind. 



striate, when marked with parallel longitudinal lines, either slightly raised or 

 merely discoloured. 



furrowed (sulcate) or ribbed (costate) when the parallel lines are more distinctly 

 raised. 



rugose, when wrinkled or marked w r ith irregular raised or depressed lines. 



umbilicate, when marked with a small round depression. 



umbonate y when bearing a small boss like that of a shield. 



