XXXVIll OUTLINES OF BOTANY. 
169. Tendrils (cirrhi) are usually abortive petioles, or abortive pe- 
duncles, or sometimes 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 consistence, 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 spinuus if it has thorns, aculeate 
if it has prickles. 
171. Hairs, in the general sense, or the indumentum (or clothing) of a 
plant, include all those productions of the epidermis which have, by a more 
or less appropriate comparison, been termed bristles, hairs, down, 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 surface is said to be scaly or lepidote. 
173. The Epidermis, or outer skin, of an organ, as to its surface and in- 
dumentum, 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. 
Jurrowed (sulecate) or ribbed (costate) when the parallel lines are more _ 
distinctly raised. 
rugose, when wrinkled or marked with irregular raised or depressed 
lines, 
umbilicate, when marked with a small round depression. 
wmbonate, when bearing a small boss like that of a shield. 
viscous, viscid, or glutinous, when covered with a sticky or clammy 
exudation. 
scabrous, when rough to the touch. 
tuberculate or warted, when covered with small, obtuse, wart-like pro- 
tuberances. 
muricate, when the protuberances are more raised and pointed but yet 
short and level. . , | 
echinate, when the protuberances are longer and sharper, almost 
prickly. : | 
setose or bristly, when bearing very stiff erect straight hairs. 
glandular-setose, when the sete or bristles terminate in a minute 
resinous head or drop. In some works, especially in the case of Roses 
and Rubus, the meaning of sete has been restricted to such as are glan- 
dular. 
glochidiate, when the sete are hooked at the top. 
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