a. 74] 



CLASSIFICATION AND DESCRIPTION 



133 



Biixus semp6rvirens, L. (BOXWOOD.) 

 Leaves ovate, smooth, dark green ; leaf- 

 stems hairy at edge. This plant is a native 

 of Europe, and in its tree form furnishes 

 the white wood used for wood-engraving. 



Var. subfruticosa (dwarf boxwood) grows 

 only a foot or two high, and is exten- 

 sively used for edgings in gardens. 

 The tree form is more rare in cultivation, 

 and is of slow growth, but forms a round- 

 topped tree. 



B. sempervirens. 



ORDER XXXVI. TTRTICACE-ffi. (NETTLE FAMILY.) 

 A large order of herbs, shrubs and trees, mainly tropical. 



GENUS 74. 



Tall umbrella-shaped trees with watery juice and alter- 

 nate, 2-ranked, simple, deciduous, obliquely ovate to 

 obliquely heart-shaped, strongly straight-veined, serrate 

 leaves, harsh to the touch, often rough. Flowers insig- 

 nificant, appearing before the leaves. Fruit a flattened, 

 round-winged samara; ripe in the spring and dropping 

 early from the trees. Bark rough with longitudinal ridges. 



* Leaves very rough on the upper side. (A.) 



A. Leaves 4 to 8 in. long ; buds rusty-downy ; inner bark very 

 mucilaginous ................................ ......... 1. 



A. Leaves smaller; buds not downy ; cultivated. (B.) 

 B. Wide-spreading tree; twigs drooping; fruit slightly 

 notched ........................................... 2. 



B. Tree rather pyramidal; twigs not usually drooping; fruit 

 deeply notched .................................. . . .3. 



* Leaves not very rough on the upper side. (O.) 



C. Buds and branchlets pubescent; twigs often with corky 

 ridges ....................................... ...... 4. 



C. Buds and branchlets free from hairs, or very nearly so. (D.) 



D. Twigs with corky wings ............................... 5. 



D. Twigs often with corky ridges; cultivated ........... 2, 3. 



D. Branchlets never corky ............ .................... 6. 



