420 



STRUCTURE OF CUTICLE AND LEAVES. 



Portion of vertical section of Leaf of Rochea, 

 showing the small Cells, o, a, of the inner layer 

 of Cuticle ; the large Cells, b, b, of the outer layer ; 

 c, one of the Stomata ; d, d, Cells of the Paren- 

 chyma ; l, lacuna between the Parenchymatous 

 Cells, into which the Stoma opens. 



of Plants having any kind of superficial investment to the cuticle. 

 Many connecting links present themselves between Hairs and 

 Scales, such as the 



Stellate Hairs of FlG> 225. 



the Deutzia scabra, 

 which a good deal 

 resemble those with- 

 in the air-chambers 

 of the Yellow Water- 

 lily (Fig. 200). 



311. The Cuticle 

 in many Plants, es- 

 pecially those be- 

 longing to the Grass 

 tribe, has its cell- 

 walls impregnated 

 with Silex like that 

 of the Equisetum 

 (§ 281) ; so that 

 when the Organic 

 matter seems to 

 have been got-rid-of 



by heat or by acids, the forms of the Cuticle-cells, Hairs, 

 Stomata, &c. , are still marked-out in Silex, and (unless the 

 dissipation of the Organic matter has been most perfectly 

 accomplished) are most beautifully displayed by Polarized light. 

 Such Silicified Cuticles are found in the Husks of the Grains 

 yielded by these plants : and there is none in which a larger pro- 

 portion of Mineral matter exists, than that of Rice, which contains 

 some curious elongated cells with toothed margins. The Hairs 

 with which the Palece (chaff- scales) of most Grasses are furnished, 

 are strengthened by the like siliceous deposit ; and in the Festuca 

 pratensis, one of the common Meadow- Grasses, the palese are also 

 beset with longitudinal rows of little cup-like bodies formed of 

 silica. The Cuticle and Scaly Hairs of Deutzia scabra also contain 

 a large quantity of Silex ; and are remarkably beautiful objects 

 for the Polariscope. 



312. Externally to the Cuticle there usually exists a very delicate 

 transparent pellicle, without any decided traces of organization, 

 though occasionally somewhat granular in appearance, and marked 

 by lines that seem to be impressions of the junctions of the cells 

 with which it was in contact. When detached by maceration, it 

 not only comes-off from the surface of the Cuticle, but also from 

 that of the Hairs, &c, which this may bear. This membrane is 

 obviously formed by the agency of the Cells of the Cuticle ; and it 

 seems to consist of the external layers of their thickened Cellulose 

 walls, which have coalesced with each other, and have separated 

 themselves from the subjacent layers, by a change somewhat 



