THE SPERMAPHYTES. 



233 



the Dicotyledons. The section from which this figure 

 was photographed was cut late in the season, after the 

 activity of the cambium had ceased. It shows the 

 growth of one season. The inner side of the dark ring 

 at A represents the position of the cambium layer ; the 

 outer portion of the same ring is the phloem, or bast. B 

 is the parenchyma of the cortex. The outer row of cells 

 at is the epidermis. D is the xylem ; in it the large 

 openings are 

 principally sca- 

 larif orm vessels ; 

 the fibro vascular 

 bundles, which 

 form a complete 

 ring around the 

 stem, are much 

 crowded to- 

 gether, and the 

 compressed pa- 

 renchyma be- 

 tween them al- 

 ready begins to 

 assume the form 

 of medullary 

 rays. E is the 

 pith paren- 

 chyma. 



Figure 154 shows a portion of a transverse section of an 

 older stem of Basswood taken near the pith. P is the 

 pith parenchyma. A is the first annual ring of the 

 xylem. B is a part of the second annual layer. Well- 

 developed medullary rays run through A and B. A shows 

 well the large vessels that develop in the first growth 

 and the small vessels that are formed in the latter part 

 of the season 



FIG. 154. Transverse section of older Basswood stem. 

 A, wood of first annual ring; B, part of second 

 annual ring ; P, pith parenchyma. 



