52 A TEXT-BOOK OF BOTANY 
(phloem).* A vascular bundle, therefore, is made up of 
wood and bast, which differ from one another in the work 
of conduction, the wood chiefly conducting the water that 
enters the plants by the roots and is passing to the leaves, 
and the bast chiefly conducting prepared food. 
The cells of the wood that conduct water are called 
tracheary vessels. They are more or less elongated and 
have very thick walls, upon which there appear markings 
of various kinds. These markings may be seen in a 
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Fic. 53.—Vessels: spiral (A) and annular (B) vessels; dotted vessel (C); sieve 
vessel (D) and sieve plate (£) from pumpkin.—A and B after Bonnier and 
SasLon; C after De Bary; D after SrRASBURGER. 
longitudinal section through the wood. Some of the vessels 
are marked by a spiral band that extends from end to end, 
and are called spiral vessels (Fig. 53, A); others show a 
series of thickened rings, and are called annular vessels 
(Fig. 53, B); while others, and among them the largest, 
* Tf a cross-section of a pine twig be stained first with safranin and 
afterward with Delafield’s hematoxylon, the xylem will become bright 
red and the phloem rich violet. 
