314 RHAMNACBAE (BUCKTHORN FAMILY) 



Leaves simple. 



Corymbs pedunoled; fruit wings broad 1, A. glabrtim. 



Corymbs nearly sessile; fruit wings narrow . . , . 2. A. grandidentatutn, 



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-lobpd, the middle oae cuneate: flowers 

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

 Mountain Maple. — New Mexico to Montanaand 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. PI. 1056. 1753. A low and fteely branched tree, 

 with Ught 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; fruili 

 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 yalvate 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 shortrclawed or wanting; fruit fleshy .1. Rhamnus. 



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



1. RHAMKUS L. Buckthokn , 



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 ithe 

 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 wooUy-ciliate : flowers appearing with the undeveloped 

 leaves and mostly solitary in their axils: mature leaves 3-5 cm. ldng> lanceo- 

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

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



