OUTLINES OF BOTANY. LIX 
§ 15. Accessory Organs. 
168. Under this mere are ae = es Sager works, various 
external parts of plants which do appear to act any essential part 
either in the cof nee w? seipsadletion: ae the near They may be classed 
pce! four heads: Tendrils and Hooks, Thorns and Prickles, Hairs and 
"169. ‘Tendrils abaet bead are usually abortive petioles, or abortive pe- 
cc or som es abortive ends of branches. They are simple or 
e or less aceiine, flexible, and, coil more or less firmly round any 
cae within their r reach, in order to support the plant to which they 
belong. Hooks are similar holdfasts, but of a firmer consistence, not 
branche and less coiled. 
Thorns and Prickles have been fancifully called the weapons of 
oleh A Thorn or Spine is the oe pointed extremity of a branch, 
le. A kl 
or abortive petiole, or abortive p Prickle is a sharply pointed 
excrescence fro e eae: and is usually produced on a branch, on 
the petiole or veins of a le nap e, or even on the calyx or 
ven on 
rolla. When the teeth of a leaf or the stipules a are pungent, they are 
also called theres not thorns. A plant is spinous if it has thorns, aculeate 
if it has prick 
171. Hairs, in the general aa or the indumentum (or bind of a 
plant, include all those productions of the epidermis which have, by a 
ore less a HO priNe panto yonts been termed bristles, oobi down, 
pose or wag 
172. Hairs are often branched. They are said to be attached by the 
centre, if pa wes from the base, and the forks spread along the surface 
in opp _— gasped, plumose if the branches are accueil along a 
omm xis, as in a feather; stellate, if several branches radiate 
horizontally. These stellate hairs have sometimes their rays connected 
he b 
together the base, forming little flat circular disks attached by the 
centre, aa are then called scales, and the surface is said to be scaly or 
lepidote 
173. The ng, aie or outer skin, of an organ, as to its surface and 
indumentum 
smooth, ‘whet without any tpi oo whatever. 
glabrous, when without t hairs of any ki 
striate, when podont — parallel lougitaatuad lines, either slightly 
raised or merely 
fu rrowed ae) or oa (costate) when the parallel lines are more 
mega 0 
rugose, guoet wrinkled or marked with irregular raised or depressed 
lines. 
umbilicate, when marked with a small round depressi 
umbonate, when bearing a small boss like that of a shield. 
seat viscid , or glutinous, when covered with a sticky or clammy 
exudatio 
jacesiik bsg rough to the touch. 
tuberculate or warted, when covered with small, obtuse, wart-like 
jiieedberanoon: 
te, when the protuberances are more raised and pointed but 
yet short and level. 
