FIBRO VASCULAR TISSUES: PHLOEM 



117 



the pine family proper. It is not necessary in an elementary work 

 like the present one to enlarge further on the organization of the 

 phloem of the gymnosperms in general or the conifers in particular. 

 The structure of the phloem in the angiosperms, and especially of 

 arboreal dicotyledons, will next occupy our attention. Here the 



FIG. 90. Transverse section of the xylem, cambium, and phloem in the American 

 linden. Explanation in the text. 



general organization is quite different from that characteristic of 

 gymnospermous groups and accordingly merits detailed considera- 

 tion. Fig. 90 shows a transverse section of the region immediately 

 internal and external to the cambium in the trunk of Tilia americana, 

 the American linden or basswood. Toward the lower side of the 



