234 THE SOLID COMPONENTS OF PLANTS. 



have been already noticed : but, when the impossibi- 

 lity of attaining an accurate knowledge of the glands 

 of the animal body, which are large and visible to the 

 naked eye, is considered, it will not appear wonder- 

 ful that our remarks on this subject are drawn rather 

 from analogy than from actual observation. When, 

 however, we reflect on the nature and diversity of the 

 vegetable secretions, and that plants possessing the most 

 opposite properties rise from the same soil, there ap- 

 pears to be no medium by which the absorbed ali- 

 ment can be so altered in its characters, except by 

 that of a glandular system. When the eye glances 

 over the number and variety of vegetable products, 

 there is much reason for supposing, that the simple 

 transfusion of fluids can scarcely be sufficient for the 

 production of these changes. We know that the laws 

 of chemical affinity, in the temperature in which they 

 take place, are inadequate to the effect ; and, besides, 

 many of the changes produced, particularly those 

 which fit the sap to be assimilated into the substance 

 of the plant itself, are directly contrary to the laws of 

 chemical affinity, which operates in destroying these 

 combinations, as soon as the vital principle of the plant 

 ceases to act. Although, therefore, we cannot by 

 demonstration prove the existence of internal glands 

 in vegetables, yet we have the strongest analogical 

 evidence in favor of the supposition that they do exist. 

 The pores and clefts of the cells and the vessels 

 which have been described are surrounded by opaque 

 regular borders ; and even the flat thread which forms 

 the spiral vessels is edged with a similar border. 

 These bodies are regarded by Mirbel as glands ; and 

 the opinion receives weight from the circumstance of 

 the mucilage, which is changed into the organized tis- 

 sue, being found always collected in greatest quantity 

 around those vessels which are most studded with these 



