STRUCTURE OF THE STEM 101 
(5) The narrow lines running in very young stems pretty straight 
from pith to bark, in older wood extending only a little of the way 
from center to bark, the medullary rays, shown in Fig. 72.1 
(c) The wedge-shaped masses of wood between these. 
(d) The pores which are so grouped as to mark the divisions 
between successive rings. These pores indicate the cross-sections of 
vessels or ducts. Note the dis- 
tribution of the vessels in the 
rings to which they belong, com- 
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Fic. 72. — Cross-Section of Beech-Wood. Fic. 73. — Longitudinal Section of 
b, bark ; a, flattened cells formed near Mahogany at Right Angles to 
end of each year’s growth; w, regu- Medullary Rays, showing Cut- 
lar wood-cells ; m, medullary ray. off Ends. (Much magnified.) 
pare this with Figs. 58, 72, and decide at what season of the year 
the largest ducts are mainly produced. Make a careful drawing 
of the end-section of one billet of wood, natural size. 
Cut off a grapevine several years old and notice the great size of 
1 These and many other important things are admirably shown ig the thin 
wood-sections furnished for $4 per set of 24 by R. B. Hough, Lowville, N. Y. 
