VARIETIES OF SECRETIONS. 57 



ojficinarum. There is great reason to suppose Sugai 

 not so properly an original secretion, as the result of a 

 chemical change in secretions already formed, either 01 

 an acid or mucilaginous nature, or possibly a mixture 

 of both. In ripening fruits this change is most striking, 

 and takes place very speedily, seeming to be greatly 

 promoted by heat and light. By the action of frost, 

 as Dr. Darwin observes, a different change is wrought 

 in the mucilage of the vegetable body, and it becomes 

 starch. 



A fine red liquor is afforded by some plants, as the 

 Bloody Dock or Rumcx sanguinms, Engl.Bot. 1. 1533, 

 the Red Cabbage and Red Beet, which appears only 

 to mark a variety in all these plants, and not to con- 

 stitute a specific difference. It is however perpetuated 

 by seed. 



It is curious to observe, not only the various secre- 

 tions of different plants, or families of plants, by which 

 they differ from each other in taste, smell, qualities 

 and medical virtues, but also their great number, and 

 striking difference, frequently in the same 1 plant. Of 

 this the Peach-tree offers a familiar example. The 

 gum of this tree is mild and mucilaginous. The bark, 

 leaves and flowers abound with a bitter secretion of a 

 purgative and rather dangerous quality, than which 

 nothing can be more distinct from the gum. The fruit 

 is replete, not only with acid, mucilage and sugar, 

 but with its own peculiar aromatic and highly volatile 

 secretion, elaborated within itself, on which its fine 



