RUTACE^E 



639 



ing a small irregular head, and slender pale branchlets covered with minute wart-like ex- 

 crescences, slightly puberulous when they first appear, soon becoming glabrous, and marked 

 during their second year by small inconspicuous leaf-scars; or a low shrub. Bark of the 

 trunk about |' thick, covered with dark brown closely appressed scales separating in large 

 irregular patches and leaving when they fall a smooth pale yellow surface. Wood hard, 

 very heavy, close-grained, light orange-brown, with rather lighter colored sapwood. 



Distribution. Often forming thickets of considerable extent and abundant near Rio 

 Grande, Starr County, Texas; mesas south of the lower Rio Grande; of its largest size 

 and tree-like in habit on the limestone ridges of the Sierra Madre of Nuevo Leon. 



3. PTELEA L. 



Small unarmed trees or shrubs, with smooth bitter bark, slender terete branchlets, with- 

 out terminal buds, small depressed lateral buds covered with pale tomentum, and nearly 

 inclosed by the narrow obcordate leaf-scars marked by the ends of 2 or 3 small fibro-vas- 

 cular bundles, and thick fleshy acrid roots. Leaves alternate or rarely opposite, without 

 stipules, long-petiolate, usually trifoliolate, the leaflets conduplicate hi the bud, ovate or 

 oblong, entire or crenulate-serrate, punctate with pellucid dots. Flowers polygamous, on 

 slender bracteolate pedicels, in terminal or compound cymes, greenish white; calyx 4 or 

 o-parted; petals 4 or 5, hypogynous; stamens 3 or 4, alternate with and as long as the petals, 

 hypogynous, much shorter in the pistillate flower with imperfect or rudimentary anthers: 

 filaments subulate, more or less pilose, especially toward the base; anthers ovoid or cordate; 

 pistil raised on a short gynophore, abortive and nearly sessile in the staniinate flower; ovary 

 compressed, 2-3-celled; style short; stigma 2-3-lobed; ovules superposed, amphitropous, 

 the upper ovule only fertilized. Fruit a 2 or 3-celled broad-winged indehiscent samara 

 surrounded by a reticulate whig or rarely wingless. Seed oblong, acute at apex, rounded 

 at base, ascending; seed-coat smooth or slightly wrinkled, coriaceous; cotyledons ovate- 

 oblong. 



Ptelea is confined to the United States and Mexico, where four or five species are known; 

 of these one is a small tree. The bark and foliage of Ptelea is bitter and strong-scented and 

 possesses tonic properties. 



The generic name is from irreXta, a classical name of the Elm-tree. 



1. Ptelea trifoliate L. Hop-tree. Wafer Ash. 



Leaves rarely o-foliolate on vigorous shoots; leaflets sessile, ovate or oblong, pointed, the 

 terminal leaflet generally larger and more gradually contracted at base than the others, 



Fig. 582 



