70 ULMACEAE. 



3. Twigs not corky-winged. 4. 



Twigs often warty or corky-winged. 12. 



4. Buds glabrous. 5. 

 Buds pubescent. 9. 



5. Flowers stalked : fruit glabrous except the edge. 6. 

 Flowers nearly sessile : fruit pubescent. U. campestris. 



6. Trees. 7. 



Shrub. U. americana nana. 



7. Leaves green. 8. 



Leaves yellow. U. americana aurea. 



8. Not weeping. (White elm). U. a'mericana. 

 Somewhat weeping. U. americana pendula. 



9. Twigs bristly: buds red-hairy. (Slippery elm). U. fulva. 

 Twigs and buds soft-pubescent. 10. 



ic. Leaves green, n. 



Leaves purple. U. glabra atropurpurea. 



11. Not weeping. (Scotch elm). U. giabra. 

 Weeping. U. glabra camperdownii. 



12. Flowers slender-stalked. 13. 



Flowers nearly sessile. Forms of U. campestris. 



13. Buds glabrous : corky wings thin. U. alata. 

 Buds pubescent : twigs coarsely corky. U. racemosa. 



PLANERA. Planer Tree. 



Deciduous small trees with somewhat brownish wood with 

 minute ducts sometimes in evident tangential lines, and "fine 

 medullary rays; slender terete zig-zag twigs; small rounded con- 

 tinuous pith; alternate 2-ranked half-round somewhat raised 

 leaf-scars ; sessile round-ovoid buds with several 2-ranked 

 scales, the end-bud absent ; short-petioled sometimes oblique 

 rather small and thick toothed leaves ; small perfect apetalous 

 clustered flowers appearing before the foliage ; and small rounded 

 blunt-spiny fruit. 

 Leaves ovate, unequally biserrate. P. aquatica. 



ZELKOVA. 



Deciduous rather small trees with slender twigs ; small pith ; 

 alternate 2-ranked scarcely raised half-elliptical leaf-scars with 



