ACCESSORY ORGANS. 



139 



(fig. 731), or branch, iii a fork (fig. 732), trident, star (fig. 733), &c. Some branch 

 in stagesj and resemble superimposed whorls (fig. 734). Chambered, septate, or 

 jointed hairs are composed of cells joined end to end, and forming 

 simple beads (figs. 785, 736) or branches; sometimes a bundle of 

 hairs radiates horizontally from a common centre, and, being united 



.•:<%\^..i /,//-;: 



732. 'Vniitlow- 

 gra^s. Bifur- 

 ■ Gated one- 

 celled hair 

 (mag.). 



733. Alyssnm. 



Starred one-celled 



hair (mag.). 



73.5. Tradescatitia. 



Chambered hair 



(mag.). 



738. Mirabilis. 

 Hair resembling 

 a necklace(mag. ) . 





737. BlEcagnus. 



Badiated hair 



(mag.). 



734. Alternanthera. 



Branched hair 



(mag.). 



The small brown scales 



by the cuticle, resembles the rays of the sun (fig. 737). 

 observable on ferns are considered as scarious hairs. 



Glands.— 'These are organs of secretion, i.e. they extract a peculiar liquid from 

 the materials with which they come in contact ; they are entirely ceUular ; the 

 cells of some glands project, and are called glandular hairs, which only differ from 

 ordinary hairs by the liquid they contain ; some are swollen at the tip ; most are 

 unicellular, as those on the calyx of the Sage (fig, 738), and on the velvety palate 

 of the Snapdragon (fig. 739). 



The stinging hairs of the Nettle (fig. 740) are formed of a single 

 conical cell, of which the base ia swollen into a bulb, and surrounded 

 by a group of epidermal cells ; the top is lightly 

 bent, and it is the fragile tip of. this hair which, 

 breaking in the skin which it has penetrated, intro- 

 duces the venomous 

 juice contained in 

 the cell. The sting- 

 ing hairs of the 

 Wigandia have a 

 lanceolate tip (fig. 

 741). Glandular hairs 

 mav be chambered, one-cefied hair 



•/ . ^mag.). 



when the terminal 

 cell alone is glandular, as in the calyx of the Snapdragon (fig. 742) ; or there may 

 be several superimposed cells ; but it is invariably the upper ones alone which 

 secrete. Peltate hairs are composed of one cell lying horizontally on the leaf, 

 and adhering by its centre to the epidermis, by means of a gland which forms its 

 bfiiSe {Malpighia). 



True glands differ from glandular hairs only in projecting slightly or not at all 



L 



Glandular 



739. Snapdragon. 

 Glandular one- 

 celled hairs 

 (mag.). 



740. Nettle. 742. finapdragon. 

 Stinging one-celled Glandular 



hair, bent chambered hair 

 at the top (mag.). (mag.). 



741 . Wigandia. 



Stinging hair 



with lanceolate 



point (mag.). 



