KEY TO GENERA 23 



113. Prickles paired at the nodes. . , Zanthoxylum ^ p. 130 



113. Not as above. 114 



114. Leaf-scars nearly encircling the thick stem. . . Aralia,p. 157 



114. Leaf-scars not as above. 115 



115. Buds elongated, stalked, pith porous. . . Ribes, p. 99 



115. Buds ovoid, pith continuous. . . Rosa, p. 117 



116. Without leaf-scars, but with persistent leaf-bases. 117 



116. With leaf-scars. 119 



117. Leaf-scars much raised on a clasping 3-nerved 

 base. . . Potentilla, p . 115 



117. Not as above. 118 



118. Pith central in the branches. . . Rubus, p. 115 



118. Pith toward one side of the branches. . . Tamarix, p. 154 



119. Bundle-traces distinct, 3 or more in a line. 120 



119. Bundle-trace one, or many traces scattered or nearly con- 

 fluent in a line. 191 



120. Leaf-scars very narrow. 121 



120. Leaf-scars broader. 145 



121. Leaf-scars straight or U-shaped. 122 



121. Leaf-scars horseshoe-shaped, or ring-like, nearly or 

 completely encircling the bud. 140 



122. Leaf-scars somewhat torn by the developing buds. . . Ptelea, p. 131 



122. Not as above. 123 



123. Stipule-scars encircling the twig. . . Magnolia , p. 94 



123. Stipule-scars smaller or none. 124 



124. Leaf- scars half-encircling the twig. 125 



124. Leai-scars shorter. 126 



125. Tall shrub, buds gummy. . . Sorbus, p. 109 



125. Small shrub, buds not gimimy. . . Xanthorhiza, p. 93 



126. Bud-scale one. . . Salix, p. 46 



126. Bud-scales two or more. 127 



127. Pith porous in old twigs. . . Ribes , p. 99 



127. Pith continuous. 128 



128. Buds round -ovoid with resinous or fleshy 

 scales. . . Baccharis, P. 195 



128. Not as above. 129 



