INTRODUCTION TO BOTANY. XXi 
tinguish ; and in some cases the embryo cannot be found until the seed 
begins to germinate. 
143. The micropyle (141) always indicates the position of the extremity 
of the radicle, whose 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. 
inferior, if pointing towards the base of the frzit. 
§ 17. Accessory Organs. 
144. Under this name are included various external parts of plants 
which often do not appear to act any essential part, either in the vegeta- 
tion or reproduction of the plant. They may be classed under four heads-— 
Tendrils and Hooks, Thorns and Prickles, Hairs, and Glands. 
145. Tendrils are either abortive petioles, or abortive peduncles, or 
abortive ends of branches. They are simple or branched, flexible, and coil 
round 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 spinous if it has thorns, aculeate if it has prickles. 
147. Hairs, in the general sense, or the ixdwment (or clothing) of a plant 
include all those processes from the epidermis which have been called 
bristles, hairs, down, cotton, or wool. 
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. 
Surrowed or ribbed, when the parallel les 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 warted, when covered with minute, blunt, wart-like 
prominences. 
muricate, when covered with short, hard, sharp prominences. 
punctate, when covered with minute dots. 
foveolate, when covered with small pits. 
echinate, when the prominences are longer and sharper, almost 
prickly. 
setose, or bristly, when bearing stiff, straight hairs. 
glandular-setose, when the sete, or bristles, are tipped with a minute, 
glandular head or drop. 
glochidiate, when the sete are hooked at the point. 
pilose, when the surface is thinly sprinkled with rather long, simple 
hairs. 
hispid, when more thickly covered with rather stiff hairs. 
hirsute, when the hairs are dense and not so stiff. 
downy or pubescent, when the hairs are short and soft; puberulent, 
when very short or minute; velvety or velutinows, when very 
dense, like the pile of velvet. 
