40 THE AFPENDASES TO PLANTS. 



The distinction between the thorn and the prickle is very easily in 

 derstood. The thom is composed both of wood and hark, the prickle 

 of bark or cuticle alone ; and hence, if you strip the bark from a rose- 

 bush or bramble, yoa will find that the prickles come entirely away 

 with it ; but if you make the same experiment on the hawthorn or 

 sloe, you will not succeed ; you may strip the bark off, but the thorn 

 will remain projecting from the wood. 



12. The tendril is a fine spiral string or fibre, proceed- 

 ing from different parts of the plant, by means of which, 

 it fastens itself to some other plant or body for support. 



The tendril is not in general at first convoluted; it shoots out in a 

 straight direction, but soon twists, and often, if it does not find a body 

 to lay hold of, puts on a very beautiful appearance, its folds lying in 

 contact with each other, and gradually contracting their diameter so 

 as to form a hollow cone, as in the Tine and passion-flower ; and 

 sometimes a tube resembling such as is made by twisting wire. 

 (F.32.) 



13. Glands are small and minute appendages of va- 

 rious forms, found chiefly on the surface of the leaf and 

 leaf-stalk, but often also on the other parts of a plant. 

 They are supposed to be organs of secretion. 



Though the leaf-stalk is that part of the plant on which they are 

 most frequently situated, yet they are by no means confined to it. 

 They are seated on the indented edges of the leaves in the sweet- 

 leaved willow ; on the base of the leaf in the almond-tree, the gourd, 

 the gelder-rose, and the bird-cherry ; on the back of the leaf in the 

 bastard ricinns, tamarisk, and others ; whilst in the butter-wort and 

 sun-dew, they spring out from the upper surface of the leaves. 



14. By the term pubescence, is to be understood, all 

 sorts of vegetable down or hairiness, with which the sur- 

 face of a plant may be covered. 



The pubescent appendages, or covering to plants, differ in form and 

 texture, but consist principally of small slender bodies, which are 

 either soft and yielding to the slightest impression, or rigid and com- 

 paratively unyielding. The former are, properly speaking, hairs, and 

 the latter brittltt. 



