INTRODUCTION TO BOTANY. XXI 



tinguish ; and in some cases the embryo cannot be found until the seed 

 begins to gonninate. 



li'6. The micropyle (141) always indicates the position of the extremity 

 of the radicle, whoso direction, either as respects the fruit or the seed, it is 

 often important to notice. The radicle is said to be 



superior, if pointing towards the summit of the fruit. 



iiiferior, if pointing towards the base oi the fruit. 



§ 17. Accessory Organs. 



144. Under this name are included various external parts of plants 

 which often do not ai)pear to act any essential pjirt, either in the vegeta- 

 tion or reproduction of the plant. They may be classed imder four heads — 

 Tendrils and Hooks, Thorns and Prickles, Hairs, and Glands. 



14;5. Tendrils are either abortive petioles, or abortive peduncles, or 

 abortive ends of branches. They are simple or Ijranched, flexible, and coil 

 romid any object within their reach, in order to support the plant to which 

 they belong. Hooks are similar holdfasts, but of a firmer consistence, not 

 branched, and only hooked at the extremity. 



146. Thorns and Prickles. A thorn or spine is a sharply-pointed, rigid 

 extremity of a branch, or abortive petiole, or abortive peduncle ; it is 

 organically connected with the woody system of a plant. A prickle is a 

 sharply-pointed, rigid excrescence from the epidermis, or outer skin ; it is 

 not connected with the woody system, and may occur on a branch, on the 

 petiole, on the veins of a leaf, on the peduncle, or even on the calyx or 

 corolla. A plant is spinou'i if it has thorns, aculeate if it has prickles. 



147. Hairs, in the general sense, or the indument (or clothing) of a plant 

 include all those processes fi-om the epidermis which have been called 

 bristles, hairs, down, cotton, or ivool. 



The epidermis or surface is said to be, 



smooth or even, when without any roughness whatever. 



glabrous, when without hairs of any kind; glabrescent, or glabrate, 



when the hairs are deciduous. 

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



merely coloured. 

 furrowed or ribbed, when the parallel lines are more distinctly 



raised. 

 The epidermis, or surface, is said to be, 



viscous, viscid, or glutinous, when covered with a sticky or clammy 



exudation. 

 tuberculate or xvartcd, when covered with minute, blunt, wai't-like 



prominences. 

 muricate, when covered with short, hard, sharp prominences. 

 punctate, when covered "with minute dots. 

 foveolate, when covered with small pits. 

 echinate, w^hen the prominences are longer and sharper, almost 



prickly. 

 setose, or bristlij, when bearing stiff', straight hairs. 

 glandular-setose, when the setic, or bristles, are tipped with a minute, 



glandular head or di'op. 

 glochidiate, when the setai are hooked at the point. 

 pilose, when the surface is thinly sprinkled with rather long, simple 



hairs. 

 hispid, when more thickly covered \\dth rather stiff" hairs. 

 hirsute, when the hairs are dense and not so stiff". 

 dowmj ox pubescent, when the hairs are short and soft; pubei-uhnt, 



when very short or minute ; velvety or velutinous, when very 



dense, like the pile of velvet. 



