HAIRS. 



313 ] 



HAIRS. 



in two directions, as in Grevillia lithido- 

 phylla (PL 21. fig. 29); in several so as to 

 form a star, as in Deutzia scabra (PI. 21. 

 fig-26); Alyssum (Pl.21.fig.28). Structures 

 analogous to the last occur upon the septa 

 of the air-cavities of the Nymphaeacese, such 

 as Nuphar lutea (PI. 21. ifig. 15), Victoria, 

 &c. 



Fig. 310. 



Fig. 308. Fig. 309. 



Q 



A 



Hairs of: — 

 Brassica (leaf). Salvia (calyx). Antirrhinum (corolla). 



Fig. 311. 



Fig. 312. 



Draba (leaf). Alyssum (leaf). 



Magnified 100 diameters. 



Compound hairs. These exhibit a similar 

 diversity of character, and often imitate, on 

 a larger scale, the forms of the simple hairs ; 

 they may be unbratiched, as in the hairs of 

 the garden Pelargonia (PI. 21. fig. 18), and 

 a large proportion of ordinary silky hairs 

 upon the epidermis of plants. Cotton is a 

 striking example, consisting of the hairs of 

 the seeds of Gossypium (PI. 21. fig. 1). 



Commonly these hairs are cylindrical, but 

 not unfrequently one or more of the upper- 

 most or all the component cells are expanded 

 into a more or less globular form. Capitate, 

 glandular, hairs often occui* on corollas, and 

 particularly on the inner scales of leaf-buds ; 

 examples: the bulbils oi Achimenes (PL 21. 

 fig. 32), the corolla of Digitalis (PL 21. fig. 

 33), Lysimachia vulgaris (PL 21. fig. 40), 

 Scrophularia nodosa (PL 21 . fig. 41), Bryonia 

 alba (PL 21. fig. 42), the inner scales of the 

 winter leaf-buds of the ash, &c. Or the 

 hairs are torulose, as in hamium album, the 



common white Dead-nettle ; or moniliform 

 or necklace-shaped, as on the stamens of 

 Tradescantia (fig. 315), the Marvel of Peru 

 {Mirabilis, fig. 313). The transition from 

 these to the branched forms are presented 

 commonly in the simpler forms of the pappus 

 of the Compositse, as in that of the Ground- 

 sel, which has toothed hairs ; in other exam- 

 ples the lateral teeth grow^ out into branches, 

 as in the species of Hieracium and other 

 Compositae, presenting pinnate or plumose 

 forms, according to the extent of ramifica- 

 tion. Verbascum Lychnitis (PL 21. fioj. 19) 

 has compound hairs branched at the joints. 

 Compound hairs likewise exhibit the hori- 

 zontal development ; the hairs of the garden 

 Chrysanthemum are horizontal, navicular 

 cells, supported on a tall articulated pedicle 

 (PL 21. fig. 30) ; the stellate haii's of the Ivy 

 (PL 21. fig. 27) are compound, and sup- 

 ported on a short stalk-cell. The last form 

 a transition to the scales of the Eleagnaceae 

 and many ferns. 



Fig. 313. 



Fig. 314. 



Fig. 315. 



Hairs of : — 



Mirabilis. Antirrhinum (calyx). Tradescantia ^stamen). 



Magnified 100 diameters. 



The bail's above noticed are mostly soli- 

 tary. In the Malvaceae {Hibiscus) tufted or 

 stellate groups of hairs are met with, and in 

 the air-cells of Utricularia are seen curious 

 groups of four hairs. Marrubium creticum 

 is another example of this kind of structure 

 (PL 21. fig. 47). 



Almost all of the above -described forms 

 of hair may contain merely watery, colour- 

 less or coloured contents ; or they may have 

 one or more of the component cells filled 

 with special, oily, resinous or saccharine secre- 

 tion. In the latter condition they are termed 

 glandular hairs. The character of these 

 organs are spoken of under the head of 

 Glands andSECRETiNG Organs of Plants. 

 It has not been thought worth while to sepa- 

 rate them in this article. 



