STINGS. 33 



On applying a high power, as the J-inch, the indivi- 

 dual cells will come distinctly into view, and the 

 nucleus will be seen very clearly as a roundish granu- 

 lar mass (PI. I. fig. 23 a). On carefully examining 

 the cell-contents, delicate lines will be observed radi- 

 ating irregularly from the nucleus, some passing to 

 the top of the cells, while others run towards its 

 base, as in the figure ; and on very close inspection, 

 the portions of protoplasm of which these lines con- 

 sist, will be found to move slowly and steadily, the 

 motion becoming perceptible by means of the minute 

 granules of which the protoplasm consists. The 

 currents return at the ends of the cell, there being 

 no passage of the contents of one cell into the cavity 

 of either of those adjacent. During this examina- 

 tion, it will be noticed that the surface of the cell- 

 wall is striated with fine wrinkles. 



It may be remarked that the hairs should be 

 taken from flowers which have only just opened ; for 

 this curious and inexplicable rotation is connected 

 with the growth of the cell ; and when this has at- 

 tained maturity, it no longer occurs. The phenome- 

 non may be observed in many other hairs of plants, 

 as those of common groundsel (Senecio vulgdris) 

 (PL I. fig. 12 a, b), and in the cells of the leaves of 

 some water-plants; but I must refer to the article 

 "Rotation" in the Dictionary for further information. 



The most important variety of hair is that derived 

 from the Cotton-plant (a kind of Mallow), and form- 

 ing the cotton of commerce. These hairs spring 

 from the epidermis of the seeds. The cells com- 

 posing it are very long and soft, becoming flaccid 

 and easily bent when dry (PI. IX. fig. 13). 



Stings. Stinging hairs or stings may be well 

 illustrated by reference to the common large nettle 

 (Urtica dioica). In this plant they consist of a thick- 

 walled cell, bulbous at the base, which is imbedded 

 in the epidermis (PL I. fig. 21), the pointed end being 



