EPIDEEMAL APPENDAGES — HAIES. 33 



two or more hooks around the apex ; shield-like or peltate (pelta, a 

 buckler), when attached by their middle, and projecting horizontally 

 on either side, as in Malpighia urens (fig. 89), and in many cruciferous 

 plants ; ciliated (cilium, an eyelash), 

 when surrounding the margin of 

 leaves. On the pod of the Oowitch 

 (Mucuna pruriens), hairs are pro- 

 duced with projections on their sur- 

 face, which cause irritation of the '®' *^' 

 skin. In Venus' Fly-trap (Dioncea muscipula), stiff hairs exist on the 

 blades of the leaf (fig. 202 e), which, when touched, cause their closure. 



Hairs occur on various parts of plants ; as the stem, leaves, flowers, 

 seed-vessels, and seeds, and even in the interior of vessels. In the 

 interior of the spathe of some palms numerous ovate cells, analogous 

 with hairs, occur in clusters, and when the spathe is dried they can 

 be shaken out in the form of powder. Cotton consists of the hairs sur- 

 rounding the seeds of Gossypium herbaceum and other species of Gossy- 

 pium. Hairs are developed occasionally to a great extent on plants 

 exposed to elevated temperatures, as well as on those growing at high 

 altitudes. When occurring on the organs of reproduction they are 

 connected with fertilisation, as the hairs on the style of Goldfussia, and 

 the retractile hairs on the style of Campanula. Different organs of 

 plants are transformed into hairs ; as may be seen in the flowering 

 stalks of the Wig-tree (Rhus Ootinus), and in the calyx of Oompositse. 



Names are given to the surfaces of plants according to the presence 

 or absence of hairs, as well as the nature of the hairs which cover 

 them. The following are the more important terms ; — Glabrous, 

 smooth, having no hairs ; hairy (pilosus), furnished with hairs j 

 pubescent, covered with soft, short, downy hairs ; villous, having long, 

 weak, often oblique hairs; sericeous, covered with long, closely ap- 

 pressed hairs, having a silky lustre ; hispid (hispidus, hirtus), covered 

 with long stiff hairs not appressed ; hirsute, having long tolerably dis- 

 tinct hairs, not stiff nor appressed ; velvety (velutinus), with a dense 

 covering of short down, like velvet ; tomentose, covered with crisp, 

 rather rigid, entangled hairs like cotton, which form a sort of felt 

 (tomentvmi) ; woolly, with long curled and matted hairs like wool ;■ 

 bearded or stupose (cj-u**), tow), when hairs occur in small tufts. 



The hairs which are most frequently met with in plants are called 

 lymphatic, from their not being connected with any peculiar secretion. 

 Those, on the other hand, which have secreting cells at their base or 

 apex, are denominated glandular, and are not to be distinguished from 

 glands, under which therefore they will be considered. Lymphatic 

 hairs occur on parts exposed to the air, and are wanting in blanched 



Kg. 89. Peltate hair of Malpighia urens, p p, arising from epideimis, e. g, The gland, 

 ■which comniunicates with the hair, t 



I) 



