LECt. HI.] LJGN f EOU8 FIBRE. 91 



secreted at the base of the petals or coloured 

 floral envelopes, in the greater number of plants ; 

 on the stalks of others, a viscid substance is 

 thrown out ; and on some, little sharp bristles 

 are planted, which are -perforated, and through 

 which a very acrid fluid is ejected into the wound 

 which they make in the cuticles of animals. 

 Examples of the first are to be found in almost 

 all flowers ; we observe the second in the species 

 of the genus Silene, called Catch-fly, and in many 

 other plants ; and the bristles of the Stinging 

 Nettle supply a well-known instance of the last. 



Of the structure of these glands, although 

 they are external, yet very little is 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 the formation of a theory 

 explaining the mode in which they perform their 

 functions. These, however, are, in some degree, 

 obvious from their effects ; and afford more than 

 probability to the idea that vegetables possess a 

 glandular system. We shall have occasion to 

 point out, and explain, the particular forms and 

 functions of these external glands in different 

 plants, when we come to examine the parts on which 

 they are situated. 



The Ligneous Jibre is a very minute, firm, 



