American Mountain Ash 



427 



The leaves are alternate, pinnately compound, the leaflets saw-toothed, their 

 stipules deciduous. The flowers are perfect, in compound cymes; the calyx- tube 

 is obconic, shallowly 5-lobed, without bracts; the 5 petals are broadly rounded 

 and contracted at the base into short claws; stamens many, inserted with the 

 petals in the throat of the calyx; ovary inferior, its cells 2 ovulcd; styles usually 

 3, distinct, and terminated by small blunt stigmas. The fruit is a small, usually 

 red, berry-hke pome, with soft, thin, cartilaginous carpels, each containing two 

 small brown seeds. 



The name apphed to these plants by Linnaeus is an old Celtic one, Sorbus 

 domestica Linnaeus, is the type species. 



About 5 species of shrubs, in addition to the arborescent forms, have been 

 described from western North America. 



Leaflets smooth above, smooth or somewhat hairy beneath. 

 Leaflets hairy on both sides. 



1. 5. americana. 



2. S. Aucuparia. 



I. AMERICAN MOUNTAIN ASH Sorbus americana Marshall 



Sorhiis sambticijolia Roemer, not Chamisso and Schlecht. 



Sargent 



Sorbus americana decora 



This small tree, often only a shrub, occurs in moist or rockv woodlands, from 

 Newfoundland to Manitoba and Iowa, southward in the mountains to North Caro- 

 lina; its maximum observed height is 9 meters, 

 with a trunk diameter of 5 dm. 



The bark is smooth, 3 mm. thick, grayish, 

 and irregularly roughened by small appressed 

 scales. The twigs are stout, shghtly hair}^, 

 soon becoming smooth, reddish brown, and 

 marked by large triangular leaf scars; the inner 

 bark is pleasantly odorous; the winter buds are 

 sharp-pointed. The leaflets, of which there are 

 II to 17, are membranous, lanceolate to oblong, 

 3 to 8 cm. long, sessile or nearly so, the terminal 

 one stalked; they vary from long taper-pointed 

 to short-pointed or blunt, are unequally wedge- 

 shaped and entire-margined toward the base, 

 sharply toothed with short-tipped or glandular 

 teeth, shghtly hairy at first, becoming smooth 

 on both sides, yellowish green, with the midrib 

 impressed above, paler, with midrib prominent, beneath; the petioles are slender 

 and grooved, the stipules broad, nearly triangular and deciduous. The flowers 

 expand in May or June; they are in dense, compound cymes 8 to 15 cm. broad, 

 on short, stout pedicels; the calyx is obconic, 5-lobed, the lobes about one fourth 

 as long as the white, nearly orbicular petals, which are about 3 mm. across. The 



Fig. 373. American Mountain Ash. 



