HAIRS. 



[ 379 ] 



HAIRS. 



as Sisymbrium Sophia (fig. 35), Alternan- 

 thera civilians (fig. 37); stellate, Alyssum 

 (fig. 308). Very often hairs composed of a 

 single cell are supported upon a short stalk, 

 and then developed horizontally in two 

 directions, as in Grevillia lithidophylla (fig. 

 29) ; in several so as to form a star, as in 

 Deutzia scabra (fig. 26*), Alyssum (fig. 28). 

 Structures analogous to the last occur upon 

 the septa of the air-cavities of the Nymphse- 

 aceae, such as Nuphar lutea (fig. 15), Vic- 

 toria, &c. 



Fig. 304. Fig. 305. 



Fig. 306. 



Hairs of : 

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



Fig. 307. 



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 uribranched, as in the hairs of 

 the garden Pelargonia (PL 28. 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 (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 occur on corollas, and 

 particularly on the inner scales of leaf-buds : 

 examples the bulbils of Achimenes (fig. 

 32), the corolla of Digitalis (fig. 33), Lysi- 

 machia vulgaris (fig. 40), Scrophularia no- 



dosa (fig. 41), Bi-yonia alia (fig. 42), the 

 inner scales of the winter leaf-buds of the 

 ash, &c. Or the hairs are torulose, as in 

 Lamium album, the common white Dead- 

 nettle ; or moniliform or necklace-shaped, 

 as on the stamens of Tradescantia (fig. 311) 

 the Marvel of Peru (Mirabilis, fig. 309)! 

 The transition from these to the branched 

 forms is presented commonly in the simpler 

 forms of the pappus of the Composite, as 

 in that of the Groundsel, which has toothed 

 hairs ; in other examples the lateral teeth 

 grow out into branches, as in the species of 

 Hieracium and other Composite, presenting 

 pinnate or plumose forms, according to the 

 extent of ramification. The seeds of Ca- 

 talpa Bungeana bear a fringe the hairs of 

 which resemble PITTED DUCTS. Verbascum 

 Thapsus (PI. 28. fig. 19) has compound hairs 

 branched at the joints. Compound hairs 

 likewise exhibit the horizontal development 

 the hairs of the garden Chrysanthemum are 

 horizontal navicular cells, supported on a 

 tall articulated pedicle (fig. 30) ; the stellate 

 hairs of the Ivy (fig. 27) are compound and 

 supported on a short stalk-cell. Very varied 

 forms of compound, more or less stellate 

 hairs occur on the leaves in the orders Jas- 

 minacese and Oleaceae. The last form a 

 transition to the scales of the Eleae-naceaa 

 and many Ferns, such as Acrostichum 



Fig. 309. 



Fig. 310. 



Fig. 311. 

 p 



Hairs of: 



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

 Magnified 100 diameters. 



The hairs 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. Marrubittm 

 creticum is another example of this kind of 

 structure (fig. 47). 



Almost all of the above-described forms 

 of hair may contain merely watery colour- 

 less or coloured contents ; or they may have 



