TISSUE FORMATION. 



13. Leaf -tissue is made up of cells, with cavities, 

 fibre-vascular bundles, and epidermis. (Fig. 17.) The 



FIG. 17. Perpendicular section of Melon-leaf: h. hairs; st. stomata ; fv. fibro-vas- 

 cular tissue of the veins. 



latter is a sort of skin composed of compressed cells, 

 among which are found openings, or pores, (stomata^] 



each guarded by two or 

 more elastic cells which 

 regulate evaporation and 

 respiration by their ex- 

 pansion. (Fig. 1 8.) 



From the surface of 

 the epidermis arise hairs, 

 formed of minute expan- 

 sions of cellular tissue. 

 They are of various forms. 



FIG. 18. Epidermis of Madder, with stomata. Some of them SCCretC 



volatile oil, others, as the nettle, an acrid fluid. They 



