THE EPIDERMIS AND ITS APPENDAGES. 23 



and therefore requires a greater supply of water than plants 

 possessed of from 70 to 100 pores on the same superficies. 



The rapidity with which plants wither and dry when not 

 watered, is exactly in proportion to the number of their exhaling 

 pores. Thus when a shower of rain occurs after long drought, 

 our readers must have witnessed that many plants revive long 

 before the moisture can have reached their roots. The only 

 absorbents in this case were the stomata on the epidermis. 



Occurring on the surface of many plants are certain minute 

 expansions of the epidermal cells termed hairs. These consist 

 either of a single elongated cell, or of several cells, placed end 

 to end. Those hairs which are not connected with any 

 peculiar secretion, are termed lymphatic. Those, on the other 

 hand, which have cellules visibly distended at their base or 

 apex into receptacles of some peculiar fluid, are termed 

 glandular. 



Fig. 4. 



Magnified view of one of the etinging hairs of the nettle with the gland at its base. 



It is from these secreting hairs that the beautiful scent of 

 the sweet brier is derived, and the sting of the common nettle 

 (Fig. 4), is produced by an acrid fluid ejected through its 

 tubular hairs from the glandular receptacles at their base a- 

 Nettles have been very properly termed the serpents of the 



