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THE ANATOMY OF WOODY PLANTS 



parenchymatous elements containing protoplasmic structures and 

 short empty cells with bordered pits. These are the transfusion 

 elements, and it is easy to observe that they are most abundant on 

 the flanks of the xylem and, in fact, take their origin from this 

 general region. As in the case of the Cordaitales, the cells of the 

 transfusion tissue surround the phloem as well as the xylem. An 

 important difference, however, is the absence of intermingled 



FIG.. 153. Transverse section o| leaf of Pinus Strobus 



parenchymatous elements in the girdle of transfusion tissue of the 

 older group. Transfusion tissue is better developed in the leaf 

 of the pine than in any other of the subtribes of conifers. In most 

 of the other subgroups of the Coniferales the transfusion tissue is 

 mainly confined to the flanks of the fibrovascular bundle, and the 

 conducting strand as a whole is not sharply separated from the 

 remaining tissues of the leaf on account of the absence of an endo- 

 dermis. 



