DRUPACEAE (PLUM FAMILY) 269 



appearing with the leaves, pale rose-color: calyx-tube adnate to the ovary, 

 its lobes pubescent within: petals orbicular-obovate: styles 2: fruit globose, 

 crowned with the persistent calyx-lobes. Colorado and to the far northwest. 



4. SORBUS L. MOUNTAIN ASH 



Low shrub with pinnate, serrate, deciduous leaves and white flowers in flat- 

 topped compound cymes. Calyx-tube urn-shaped or turbinate, 5-lobed. 

 Petals 5, spreading, short-clawed. Stamens 20. Styles 3-5, distinct, woolly 

 at base. Ovary 3-5-celled, becoming a berry-like pome with 2-seeded cells. 

 Pyrus. 



1. Sorbus scopulina Greene, Pitt. 4: 130. 1900. Shrub 1-4 m. high, rather 

 stout, the young branches sparsely hirsutulous: leaves 1-2 dm. long, the 

 rachis glabrous or slightly pilose at the joints; leaflets 11-15, glabrous on 

 both sides, 3-4 cm. long, oblong-lanceolate, sharply serrate; the teeth not 

 glandular or callous at tip: cyme large, flat-topped: fruit red, bitter. Pyrus 

 sambucifolia, in part. Rocky canons; Colorado, Wyoming, and northwest- 

 ward. 



56. DRUPACEAE DC. PLUM FAMILY 



Trees or shrubs, with alternate, petioled, serrate leaves and small early- 

 deciduous stipules. Bark, leaves, and seeds bitter (prussic acid). Flowers 

 regular and perfect. Calyx 5-lobed, free from the ovary, deciduous. Petals 

 5, inserted on the calyx as are also the numerous stamens. Stigma small, 

 capitate; ovary 1-celled. Fruit a drupe. Rosaceae in part. 



PRUNUS L. PLUM AND CHERRY 



Trees or shrubs, with simple serrate leaves, the bark exuding gum. Flowers 

 white, fascicled in the axils or in terminal racemes. Calyx 5-cleft. Petals 

 5, spreading. Stamens 15-25, inserted with the petals. Carpels solitary, 

 entirely free from the calyx, becoming drupes. 



Leaves convolute in vernation; fruit large and pit flattened. 

 Flowers appearing before the leaves; umbels 2-5-flowered. 



Sepals entire, not glandular . . . . . . . 1. P. americana. 



Sepals glandular-ciliate 2. P. angustifolia. 



Flowers appearing after the leaves; umbel 1-3-flowered . . 3. P. ignota. 

 Leaves conduplicate in vernation; fruit small and pit subglobose. 



Flowers in terminal racemes 4. P. melanocarpa. 



Flowers axillary. 



A small tree; flowers in short corymbs . . . . . 5. P. pennsylvanica. 



A low shrub; flowers in sessile umbels . . . . . 6. P. Besseyi. 



1. Primus americana Marsh, Arb. Am. 111. 1785. Tree thorny, 2-5 m. 

 high: leaves ovate or somewhat obovate, conspicuously pointed, coarsely or 

 doubly serrate, very veiny, glabrous when mature: fruit nearly destitute of 

 bloom, roundish oval, yellow, orange, or red; the stone turgid, more or less 

 acute on both margins; pleasant-tasted, but with a tough and sour skin. 

 WILD YELLOW or RED PLUM. Along streams; Colorado, Wyoming, and east- 

 ward. 



2. Primus angustifolia Marsh, Arb. Am. 111. 1785. Stem scarcely thorny: 

 leaves nearly lanceolate, finely serrulate, glabrous: fruit nearly destitute of 

 bloom, globular, red; the stone ovoid, almost as thick as wide, rounded at 

 both sutures, one of them minutely grooved. P. chicasa Michx. CHICKASAW 

 PLUM. Native in the central southwest; w r idely introduced ; Colorado. 



3. Prunus ignota A. Nels. Bot. Gaz. 42: 53. 1906. Shrubby or possibly 

 becoming tree-like; branches slender, none of them becoming indurated or 

 thorny: leaves glabrous from the first, simply and sharply serrate: flowers 

 white, appearing with or after the leaves, solitary or 2-3 in a cluster; calyx 



