50 PRACTICAL BOTANY. 



1. The Epidermis, a single peripheral layer of 

 cells, not very well defined from the underlying tissues : 

 it completely covers the surface. 



N.B. The margin is not perfectly regular, but is 

 here and there extended outwards at the regions sur- 

 rounding the bases of the large multicellular hairs, 

 which may be recognised as being products of the 

 epidermis. 



Since these hairs are usually injured in cutting the sections, the 

 width of their bases being greater than the thickness of a fine 

 section, in order to see them well thick sections should be made 

 specially, care being taken that the hairs shall not be previously 

 injured before the sections are cat. They will then be seen to be 

 long conical hairs with pointed ends, consisting of many cells, 

 uniseriate : their bases are imbedded in cells of the epidermis 

 and underlying tissue, which together form at that point a small 

 emergence, on the apex of which the hair is borne. Other 

 smaller hairs also occur. Compare the description of the apical 

 bud (p. 64). 



Beneath this single epidermal layer lies 

 2/ A band of tissue, several layers of cells thick, 

 the walls of which are thickened at the angles where 

 three or more cells meet, the cell-cavity being thus 

 made oval or circular in transverse section ; this is the 

 chief characteristic of Collenchyma, of which this is a 

 good type. Below this lies 



3. A band of thin-walled Parenchyma, in which 

 are dotted here and there resin-passages. 



Within these tissues of the Cortex (a general term 

 including the tissues described under the headings 2 

 and 3) lie 



4. The Vascular bundles, which are wedge-shaped 

 and are arranged in a ring : according to the stage of 



