MALACEAE 1 29 



ness of its members, especially the apple and pear. There are 

 four shrubby genera found in Illinois. 



Key to the Shrubby Genera 



Leaves compound Sorbus, p. 129 



Leaves simple. 



Shrubs without spines. 



Leaf margins serrate and teeth gland-tipped ; stalked 



glands on the midrib above Aronia, p. 130 



Leaf margins serrate but the teeth not gland-tipped ; no 



stalked glands on the midrib above . Amelanchier, p. 133 

 Shrubs with spines Crataegus, p. 134 



SORBUS (Tournefort) Linnaeus 

 Mountain-Ash 



The mountain-ashes are shrubs or trees, which bear alternate, 

 pinnately compound leaves consisting of serrate leaflets, decidu- 

 ous stipules, and perfect, regular flowers in terminal, compound 

 cymes. The flowers have 5 erect, or spreading, deciduous sepals, 

 5 white, spreading petals, many stamens, and an inferior ovary 

 adnate to the hypanthium. The styles are 3 and usually distinct, 

 and the 3 cells of the ovary each contain 2 ovules. The fruit is 

 small, berry-like and, in our species, red and very acid. 



There are about 10 species, all of them natives of the north 

 temperate zone, and at least 4 are native in North America. 

 The cultivated mountain-ash, noteworthy for its decorative, 

 orange-yellow fruit, is a member of the genus. There is only 

 one shrubby species native in Illinois. 



SORBUS SUBVESTiTA Greene 



Western Mountain-Ash 



The Western Mountain-Ash is an erect shrub, or more rarely 

 a small tree, with branchlets which are at first long pubescent 

 but soon become smooth. Its leaves, which are 4 to 6 inches 

 long, stand on petioles J/^ to ll/^ inches long and consist of 13 

 to 17 leaflets arranged in pinnate pairs along the rachis. The 

 leaflets are lanceolate or oblong, up to 1^ inches long by I/2 inch 

 or a little more wide, acute at the apex, rounded and very asym- 

 metrical at the base, the upper half being the shortest. The 

 margins are singly and sharply serrate to near the base, or the 

 lower side may be serrate only to about the middle. Both sur- 



