366 



THE SPERMATOPHYTES 



351. The tissues of the pine stem. The pine is an excellent 

 subject for the study of stem structure and growth in a timber 

 tree. There are five principal regions in the stem: (1) the pith, 



FIG. 297. Structure of the stem of the Scotch pine (Pinus sylvestris) 



A, diagram of the arrangement of the fibro-vascular bundles at a growing point : 

 the shaded parts are wood. B, diagram of the position of the principal tissues 

 shown in a cross section of a four-year-old stem. C, cross section of a region 

 of cambium Cain, with adjacent wood and bast. D, cross section of wood at 

 an annual ring: d, resin duct. E, radial section of wood. F, longitudinal sec- 

 tion of wood. G, section of bordered pit. Medullary rays m appear in most 

 of the figures 



(2) the woody (3) the cambium, (4) the last, and (5) the outer 

 bark (see Fig. 297, B). 



The pith occupies the very center of the stem, and is the 

 remains of the undifferentiated primitive tissue present at its 



