ULMUS 85 



a. Twigs without corky outgrowths 



b. Buds downy, dark-colored, nearly 



black; twigs rough, ashy-gray in color 1. U. rubra 



b. Buds brown, glabrous or pale -pubes- 

 cent; twigs smooth or sparingly pilose 2. U. americana 



1. jy_. rubra M uhl. Slippery Elm . Red Elm. (U. fulva Michx. ). 

 A tree 15-24 m. high, 3-7. 5 dm. thick, with tough reddish wood; 

 bark rough, gray, the inner bark very mucilaginous (whence the 

 name, slippery elm); twigs gray-buff, rough-hairy; buds downy 

 with red hairs; flowers nearly sessile, in groups of several, be- 

 ginning to appear in March. Moist soil. New England to North 

 Dakota, south to Florida and Texas (Fig. 81 ). 



2. _U. americana L. American Elm . A handsome tree, 20-50 

 m. high, 6-18 dm. in diameter, usually with a spreading vase- 

 shaped crown and somewhat drooping branchlets; bark gray, flaky, 

 with alternating light and dark layers in cross section; twigs 

 glabrous or sparingly pubescent; buds brown, glabrous or some- 

 what pubescent; flowers long-pedicelled, in groups of 3 or 4, be- 

 ginning to appear in March. Mostly in bottomlands, Quebec to 

 Saskatchewan, south to Florida and Texas (Fig. 82). 



3. XL thomasi Sarg. Cork Elm . Rock Elm (U. racemosa 

 Thomas). A tree attaining a height of 35 m. and a diameter of 

 12 dm. twigs glabrous or puberulent; bud-scales downy-ciliate; 

 branches often with corky ridges. Rich woods, mostly on lime- . 

 stone outcrops. New England to Minnesota and South Dakota, south 

 to Tennessee and Kansas (Fig. 83 ). 



4. U. alata Michx. Winged Elm. A small round-topped tree, 

 up to 20 m. high; branches corky- winged ; branchlets and buds 

 nearly glabrous. Flowers in short racemes, appearing in March. 

 Low woodlands, Florida to Texas, north to Virginia, Kentucky, 

 and Missouri (Fig. 84). 



CELTIS L. (Ulmaceae) 



Deciduous trees or shrubs. Twigs rounded, slender; pith 

 small, white, round, closely chambered, or continuous except at 

 the nodes. Buds sessile, solitary, ovoid, with about 4 scales. 

 Leaf-scars alternate, crescent-shaped or elliptical; bundle -traces 

 1 or 3; stipule-scars narrow. Fruit an ovoid or globose drupe, the 

 mesocarp thin, pulpy, the end o carp bony. 



a. Tree with buds 3-4 mm. long; drupes 



8-11 mm. long 1. C. occidentalis 



