BOTANY. 



151 



of the plant. They are met with in the trunk or in the 

 leaves, where they communicate with the external air by little 

 openings called Stomata. 



EXTERNAL ARRANGEMENT. 



EPIDERMIS. 



The external, general envelope of plants, composed, first, of 

 a simple superficial pellicle, without appreciable texture, 

 pierced with elongated apertures, corresponding to the middle 

 of the stomata ; secondly, of one of several beds of utricles, 

 diversely formed, according to the species, intimately united, 

 and filled with a liquid which is generally colourless. 



STOMATA. 



Little oval apertures, rarely visible to the naked eye, pre- 

 senting themselves, when viewed through a microscope, with 

 dark lip-like edges, and situated between the ordinary cells of 

 the epidermis, principally upon the parenchyma of the leaves, 

 and communicating, internally, with air cells. They have 

 the property of closing, when moistened. 



LENTICLES. 



Small tubes or punctuations found upon the surface of the 

 branches of monocotyledonous vegetables, and which they 

 render more or less rough to the touch ; their colour is gene- 

 rally paler than that of the wood; the young roots issue 

 through them, when a branch is put into the moist earth. 



Hairs. 



Appendages of the cellular tissue, formed of elongated cells, 

 and designated according to their forms, their consistency, or 

 their physiological functions, as simple, divided, aculeiform, 

 glanduliferous, excretory, &c. 



The Root. 



The inferior part of vegetables, by which they are fixed to 

 the earth, and through which the liquids which nourish them 

 penetrate. It is characterized by growing in a direction op- 

 posite to that of the trunk ; by being elongated only through 

 its extremities ; by being without stomata ; by never becoming 



