GENERAL TEXTURE OF PLANTS. 29 



than secretion, as well as the due preservation of what 

 has been secreted, are both at an end, and the principle 

 of dissolution reigns absolute. 



Before we can examine the physiology of vegetables, 

 it is necessary to acquire some idea of their structure. 



Much light has been thrown upon the general texture 

 of Vegetables by the microscopic figures of Grew, IMul- 

 pighi and others, repeated by Dr. Thornton in his Illus- 

 tration of the Linnaean System, but more especially by 

 the recent observations and highly magnified dissections 

 of M, Mirbel. See his Table of Vegetable Anatomy in 

 the work already mentioned. From preceding writers 

 we had learned the general tubular or vascular structure 

 of the vegetable body, and the existence of some peculiar 

 spirally-coated vessels in many plants. On these slen- 

 der foundations physiologists have, at their pleasure, 

 constructed various theories, relative to the motion of 

 the sap, respiration and other functions, presumed to be 

 analogous to those of animals. The anatomical observa- 

 tions of Mirbel go further than those of Grew, &:c. and it 

 is necessary to give a short account of his discoveries. 



He finds, by the help of the highest magnifying pow- 

 ers, that the vegetable body is a continued mass of tubes 

 and cells ; the former extended indefinitely, die latter 

 frequently and regularly interrupted by transverse par- 

 titions. These partitions being ranged alternately in the 

 corresponding cells, and each cell increasing somewhat 

 in diameter after its first formation, except where re- 

 strained by tlie transverse partitions, seems to account 



