THE SOLID COMPONENTS OF PLANTS. 235 



opaque borders. If vegetable glands then do exist, 

 they must necessarily enter, as a general component 

 into the structure of every plant. 



Besides these obscure internal glands, there are 

 also external bodies, which all Botanists have agreed 

 in considering as glands, and which, in general, sepa- 

 rate, as an excretion, some peculiar fluid. Thus honey 

 or a nectarious fluid is secreted at the base of the petals, 

 in the greater number of plants ; on the stalks of others, 

 (as the Catcb-fly) a viscid substance is thrown out ; and 

 on some, perforated hairs or bristles, emit spontaneous- 

 ly a mild, or eject into the punctures they make in the 

 skins of animals, an acrid fluid. Such are the excret- 

 ing glandular hairs of the Sun-dew (Drosera), and the 

 stings of the Nettle and the Jatropha. 



Of the structure of these glands, although they are 

 external, very little is yet known ; and microscopes of 

 the greatest magnifying powers present them as masses 

 of cellular substance only, with vessels passing on to 

 their centre, without developing any other particular 

 organization, which might lead to explain the mode in 

 which they perform their functions. These, however, 

 are, in some degree, obvious Irom their effects ; and 

 afford more than pr bability to the idea that vegeta- 

 bles possess a glandular system. 



The Ligneous fibre is a very minute, firm, elastic, 

 semi-opaque filament, which, by its cohesion with other 

 filaments of the same kind, forms the proper fibres, or 

 layers of longitudinal fibres, that constitute the grain 

 or solid part of wood. It enters, also, into the com- 

 position of another set of layers, that traverse the 

 longitudinal, named divergent. It is intended, appar- 

 ently, to give support and firmness to the vegetable 

 body, and hence is found in greater abundance in 

 trees and other perennial plants ; and according to the 



