LEAVES 



167 



Leaf Arrangement. When one leaf occurs at a node, as in 

 wild cherry, the leaves are alternate; when two leaves occur 

 at a node, as in viburnum, the leaves are opposite; when 



6| Til 81 I 9 



FIG. 102. Leaf Scars. 1, Ailanthus (Ailanthus glandulosd) ; 2, horse- 

 chestnut ((Esculus hippo castanum) ; 3, elder (Sambucus canadensis) ; 4 

 white ash (Fraxinus americana) ; 5, Hercules' club (Aralia spinosd) ; 6, butter- 

 nut (Juglans cinered) ; 7, shagbark hickory (Hicoria alba) ; 8, Carolina poplar 

 (Populus deltoides); 9, linden (Tilia americana); 10, northern prickly ash 

 (Xanthoxylum whericanum) ; 11, staghorn sumac (Rhus hirta). 



more than two leaves occur at a node, as in yellow field lily, 

 the leaves are whorled; when the leaves are grouped in a 

 cluster, as in white pine, they are fascicled. 



