82 PRACTICAL BOTANY. 



spaces known as mtercellular spaces, or, in case they are 

 large and regular, intercellular passages, or air^assages. 

 They may contain special secretions, and in all probability 

 the milic-vessels are, primarily, regular intercellular air- 

 passages, instead of being composed of special cells. Ihe 

 PUurenchyma and the Parenchyma together form the 

 mainhulh of almost oilplants.) 



Cut VI. 

 Piece of a woody bundle, or compound fibre of an endogen ; a, Parenchyma cells ; 

 J, ducts witli rings, called annular cells ; c, spiral ducts ; d, a dotted duct ; e, wood- 

 cells. 



74. The aekangement of the elementaet cegans 

 on the surface of plants constitutes the Epidermial system, 

 that is to say, the epidermis, stomata, hairs, glands, 

 cuticle, etc. (Out VII.) 



The Epidermis is a membrane, foinned of a layer of 

 united, and commonly tabular, empty cells. The Mosses 

 only excepted, it invests all plants, and all their parts, save 

 the extremities, the stigma and the rootlets, and may be 

 detached untorn from the underlying tissue. In certain 

 places, especially on the lower surface of the leaves, it is 

 pierced with a great many small openings, called stomates 

 or hreathing pores. Prominences are formed by elon- 

 gated epidermial cells, and are called hairs, glands, tuber- 

 cles, warts, stings, "bristles, pricMes, scurf. 



