242 



Vegetable Physiology. 



The following figures will illustrate the difference 1 

 respect between the leaf of the Lily, where the upper strati 

 contains but a single layer of barely oblong cells, and that f 

 the Oleander, a native of dry and sun-burnt places in the E a 

 the upper stratum of which consists of two layers of very l on ' 

 vertical cells as closely compacted as possible. 



Fig. 13. 



a 



I li i.liii 1 tliilTl'i J III 



■ it- JLuV 1 it Hvi 1 ■ L 1 J if 



In Figure 13 a represents a magnified section through the 

 thickness of a leaf of the White Lily, showing the parenchyma 

 and the epidermis of both surfaces ; the lower pierced with 

 stomata. c shows the appearance of two of the cells of the 

 upper stratum of parenchyma, detached and more magnified, 

 snowing the contained grains of chlorophylle. /, a magnified 

 view of the hundredth part of a square inch of the epidermis of 

 the lower surface, with the stomata, or breathing pores, it bears. 

 These are unusually large in the Lily, so as to be visible by a 

 very moderate magnifying power, and are proportionally few 

 in number. One them is shown more magnified, at e in the 

 closed state ; and open at b. d is a magnified perpendicular 

 section through the thickness of the epidermis and upper stratum 

 of parenchyma in the leaf of the Oleander, showing the epider- 

 mis composed of three layers of thick-sided cells, and the 

 upper parenchyma of very compact vertical cells. 



