336 THE MICROSCOPE. 



by minute openings termed Stomata, which are bordered by 

 cells of a peculiar form, distinct from those of the cuticle. 

 In Iris germanica, fig. 181, each surface has nearly 12,000 



1, Portion of a vertical section of the Leaf of the Iris: a, a, elongated cells of 

 the epidermis; b, stomaia cut through longitudinally; c, c, cells of the 

 parenchyma; d, d, colourless tissue of the interior of the leaf. 2, Portion of 

 leaf of Iris germanica, torn from its surface; a, elongated cells of the cuticle; 

 b, cells of the stomata; c, cells of the parenchyma; d, impressions on the epi- 

 dermic cells ; e, lacunae in the parenchyma. 



stomata in every square inch ; and in Yucca each surface 

 has about 40,000. 



The structure of the leaf of the common Iris shows 

 a central portion, formed by thick- walled colourless tissue, 

 very different from ordinary leaf-cells or from woody fibre. 



Fig. 182. A portion of the efidermi$ of the Sugar-cane, showing the two kinds oj. 

 cells of which ii is composed. (Magnified 200 diameters.) 



