30 



EPIDERMAL APPENDAGES. GLAKDS. 



cover them. The following are the more important terms: Glabrous, 

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

 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 

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

 bearded or stupose, (VTVKYI, tow), when hairs occur hi small tufts. 



61. 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 plants. On 

 young roots, cellular projections of the cuticle are seen (fig. 77), which 

 may be called radical hairs. Young leaves and buds are frequently 

 thickly covered with protecting hairs. In this instance the hairs arise 

 chiefly from the veins; and as the leaves increase hi size, and the veins 

 are separated, the hairs become scattered, and apparently less abun- 

 dant. On the parts of the flower, coloured hairs occur which have 

 been called coralline. 



62. Gland* are collections of cells forming secretions. The term 

 has been vaguely applied to all excrescences occurring on the surfaces 

 of plants. They are either stalked (petiolate, stipitate) or not stalked 



abed (sessile). The former 

 f ^ may be called glandular 



hairs, having the secret- 

 ing cells at the apex. 

 Stalked glands, or glan- 

 dular hairs, are either 

 composed of a single cell, 

 with a dilatation at the 

 apex (fig. 85 a), or of 

 several cells united to- 

 gether, the upper one 

 being the secreting or- 

 gan (fig. 85 ft). In place 

 of a single terminating 



Fig. 85. Glandular hairs, e, Epidermis, a, Hair formed by a single cell from Sisymbrium 

 chilense. 6, Hairs formed of several cells terminated by a secreting cell, from flower-stalk of 

 Antirrhinum majus. c, Hair composed of several cells, terminated by two secreting cells 

 united laterally, from flower-stalk of Lysimaehia vulgaris. d, Compound hair, terminated 

 by several secreting cells united end to end, from Geum urbanum. 



