52 TREES OF THE NORTHERN UNITED STATES 
KEY TO THE GENERA OF TREES. 
* Leaves narrow linear, needle, scale or awl shaped, usually but not 
always evergreen. (GG.) page 60. 
* Leaves broad, flat, usually deciduous; occasionally evergreen, 
rarely over 5 times as long as wide. (aa.) 
aa. Leaves alternate (see p. 18, Caution), simple. (bb.) 
aa. Leaves alternate, compound. (m.) page 57- 
aa. Leaves opposite or whorled on the stem. (u.) page 58. 
bb. Leaves with a midrib, netted-veined. (cc.) 
bb. Leaves without a midrib, parallel-veined (appearing fan-like)... 
CREM a Nas Rae San aase Mose eee neo estes 109. Salisburia. 
ec. With radiating ribs, and including those which have the 
lower ribs longer and more branching than those above 
them. (K.) 
ec. With distinct and definite feather-veining. (dd. ) 
dd. Margin entire, or so nearly so as to appear entire, sometimes 
slightly angulated but not lobed. (V.) page 55. 
dd. Once or twice serrate or crenate or wavy-edged, but not lobed. 
(ee. ) 
dd. Distinctly lobed. (S.) (If the notches are over 10 on a side, 
look under ee.) 
ee, Straight-veined. (L.) 
ee. Not distinctly and evenly straight-veined. (ff.) 
ff. Leaves evergreen. (A.) 
ff. Leaves deciduous. (B.) 
A. With either revolute or spiny-tipped margins...... ..18. Tex. 
A. With minutely serrate margins and wedge-shaped bases; flow- 
ers white, 3-4 inches wide. No. 1in............ 8. Gordonia. 
A. With entire or minutely serrate margins and rounded bases ; 
flowers inconspicuous. No. 3in.............0. 20. Rhamnus. 
B. Leaves broadened and coarsely notched near the tip ; whole plant 
whitened with scurf............ cece ewer eee ee 49. Baccharis. 
B. Leaves sour; peach-like in shape.............. 50. Oxydendron. 
B. Leaf length usually 3 or more times the width; finely serrated 
(or entire) ; buds covered by but one scale; large stipules often 
present On SOME tWIGS....... 0 cece ee eee teen 91. Salix. 
B. Plants thorny. (C.) 
B. Not included in the above. (H.) 
C. Lowest side veins much the longest ; leaves sometimes opposite. 
NOL DNs cits ep sap ramaa igi way tawaloaa eee ets 20. Rhamnus 
