80 VASCULAR TEXTURE. [LECT. III. 



L Entire vessels. 



2. Perforated vessels, 



3. Spiral vessels. 



1. The ENTIRE VESSELS are, as their names im- 

 port, simple tubes formed of imperforated mem- 

 brane. They are cylindrical ; and are generally 

 in bundles, regularly disposed in the cel- 

 lular part of the bark (fig. c). They are 

 found in the young shoots of almost every 

 kind of plant ; and in the fasciculated 

 state may be readily detected, and ex- 

 amined by the aid of magnifying-glasses, 

 in the leaf-stalk of the common Fern, in 

 the Arrow-head, Sagittaria sagittifblia, 

 and in the common Hemp. In order to 

 examine them individually, the bundles should be 

 steeped in spirit of turpentine for a few days, 

 by which means the vessels can be easily detached 

 from one another. 



These vessels are intended to convey the proper 

 juices of the plant \ and are generally found filled 

 with oils, and resinous juices ; consequently, they 

 are more numerous in plants, the juices of which are 

 of a thick resinous nature; and these drying along 

 with the condensed vessel in the bark, are the 

 matters on which the medicinal virtues of barks 

 in general depend. They are described by Mirbel 

 under the name vaisseaux propres *, and are di- 



* Element de Phys, vrg. Partie l erp , p. 31. * 



