1918] LANGDON—RAY SYSTEM OF QUERCUS 317 
are broad, high, gradually tapering wedges, usually formed by the 
gradual widening of a single uniseriate or triseriate ray which has 
its origin at the pith; (2) compound rays, which are wide sheets of 
ray parenchyma formed by the aggregation of many small linear 
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IGS. 9, 10.—Transverse sections of portions of compound rays showing oe 
mode of origin of compound rays: uniseriate (w), multiseriate (m), and compound 
(c) rays; f, wood fibers; #, conte p, thin-walled parenchyma marking boundary 
tween rings of growth; 
Tays; (3) in addition to these broad rays there are “secondary”’ 
broad rays, formed as the stem increases in circumference, which 
originate abruptly some distance from the center, not by a gradual 
widening of a single ray nor as the result of the fusion of many small 
