THE VESSELS. 37 



is thought to be founded on a simple hypothesis, viz. the 

 sensibility of plants ; but, even in admitting a nervous 

 system in plants, it would be impossible to believe that 

 it was represented by an organ which is found wanting 

 precisely in those plants which bear the greatest resem- 

 blance to animals. 



Section III. 

 Of Annular or Striped Vessels. 



The vessels wliich I here designate (PI. 2, fig. 1 b, b, 

 2 a, a, 5 a, a.) are those which Mirbel has described 

 under the name of False Trachea (fausses tracMes), 

 Kieser under that of Spiral Annular Vessels 

 (vaisseaux spiraux annulaires), and which I have often 

 mentioned under that of Striped Vessels (vaisseaux 

 rayes). Seen with the microscope, they commonly pre- 

 sent the appearance of simple cyKndrical tubes, marked 

 with regular transverse parallel lines ; when they are 

 observed embedded in the tissue, they resemble true 

 tracheae which will not unroll ; and they have often 

 been described by the old anatomists under the name of 

 Trachea; ; they differ from them, however — 



1st, Because they do not unroll, and do not afford 

 any trace of elasticity. 



2d, Because their hues (raies) appear parallel, and 

 not spiral. 



3d, Because in the same plant they differ in diameter 

 from the tracheae. 



Striped Vessels are found, in general, in the woody 

 part of vascular plants; among Dicotyledons they are 

 found in all the layers, except in the immediate envelope 



