314 RHAMNACEAE (BUCKTHORN FAMILY) 



Leaves simple. 



Corymbs peduncled; fruit wings broad 1. A. glabrum. 



Corymbs nearly sessile; fruit wings narrow . . . . 2. A. grandidentatum. 



Leaves compound . . . . . . . . . 3. A. Negundo. 



1. Acer glabrum Torr. Ann. Lye. N. Y. 2: 172. 1826. A shrub usually, 

 rarely a small tree: leaves orbicular in outline, 3-lobed or often 3-parted, 

 sometimes truncate or subcordate at base; segments short and broad, acutely 

 incised and toothed, somewhat 3-lobed, the middle one cuneate: flowers 

 polygamous, the umbel-like corymb pedunculate: sepals about 8. ROCKY 

 MOUNTAIN MAPLE. New Mexico to Montana and west to the coast. 



2. Acer grandidentatum Nutt. T. & G. Fl. N. A. 1: 247. 1838. Becoming a 

 tree, sometimes 10-12 m. high: leaves slightly cordate or subcordate at base, 

 rather deeply 3-lobed, the sinuses broad and rounded; the lobes subacute with 

 a few sinuous indentations: corymbs nearly sessile, few-flowered; the pedicels 

 long and nodding: fruit glabrous, with small diverging wings. Infrequent; 

 near streams; from western Wyoming into Utah and northward. 



3. Acer Negundo L. Sp. PL 1056. 1753. A low and freely branched tree, 

 with light green twigs and delicate drooping clusters of greenish flowers, a lit- 

 tle earlier than the leaves: leaves trifoliolate or pinnately 5-foliolate; the leaf- 

 lets ovate, acute, dentate: flowers dioecious: petals and disk wanting: fruit 

 glabrous, the broad wings somewhat incurved and finely veined. Negundo 

 aceroides. (Rulac Negundo and R. texanum Rydb. Fl. Col. 227. 1906.) Box 

 ELDER. From New Mexico and Arizona northward to Canada and eastward. 



70. RHAMNACEAE Dumort. BUCKTHORN FAMILY 



Shrubs or small trees, with simple undivided leaves, small and often ca- 

 ducous stipules, and* small regular flowers. Sepals valvate in the bud; a con- 

 spicuous disk lining the short tube of the calyx. Petals clawed, mostly in- 

 volute, each around a stamen in the bud, sometimes wanting. Stamens 

 perigynous and alternate with the sepals. In ours the fruit is berry-like or 

 dry, containing 2-4 separating seed-like nutlets, and the leaves are alternate. 



Petals short-clawed or wanting; fruit fleshy . . . . . .1. Rhamnus. 



Petals long-clawed; fruit dry, with three dehiscent nutlets . . . .2. Ceanothus. 



1. RHAMNUS L. BUCKTHORN 



Shrubs or small trees (ours unarmed), with alternate or somewhat opposite 

 pinnately veined leaves and small greenish flowers in sessile or short-peduncled 

 axillary umbels. Calyx 4-5-cleft, with erect or spreading lobes, the cam- 

 panulate tube persistent and lined with the disk. Petals on the margin of the 

 disk which is free from the ovary. Fruit berry-like, with 2-4 indehiscent 

 nutlets. 



Petals wanting; nutlets grooved . . . . . . . . 1. R. alnifolia. 



Petals present; nutlets smooth ........ 2. R. Smithii. 



1. Rhamnus alnifolia L'Her. Sert. Angl. 5. 1788. Shrub 6-12 dm. high: 

 leaves deciduous, ovate-oblong, acute at each end, 5-8 cm. long, crenately 

 serrate, slightly puberulent on the slender petioles: calyx-lobes and stamens 5: 

 fruit black, 3-lobed, 6 mm. long, as long as the pedicels. Northern Wyoming 

 and westward. 



2. Rhamnus Smithii Greene, Pitt. 3: 17. 1896. Deciduous shrub, with 

 short, stout, glabrous, rather densely leafy and fructiferous branchlets: bud- 

 scales obtuse, densely woolly-ciliate : flowers appearing with the undeveloped 

 leaves and mostly solitary in their axils: mature leaves 3-5 cm. long, lanceo- 

 late, scarcely acute, finely serrulate: flowers 4-merous: berries on very short 

 pedicels, black when ripe, 2-seeded. Southern Colorado. 



