684 The Trees of Great Britain and Ireland 



ACER NEGUNDO, Ash-leaved Maple, Box Elder 



Acer Negundo, Linnaeus, Sp. PL 1056 (1753); Sargent, Silva N. Amer. ii. in, t. 96 (1892), and 



Trees N. Amer. 641 (1905). 

 Negundo aceroides, Moench, Meth. 334 (1794). 

 Negundo fraxinifolium, Nuttall, Gen. Amer. L 253 (1818); Loudon, Arb. et Frut. Brit. i. 460 



(1838). 



A tree attaining in America 70 feet in height and 12 feet in girth; bark 

 deeply fissured into broad rounded ridges. Young branchlets green or glaucous, 

 glabrous. Leaves (Plate 205, Fig. 2) pinnate, turning yellow in autumn. Leaflets, 

 three or five, stalked, ovate or oval, rounded or cuneate at the base, acuminate 

 at the apex, serrate or toothed above the middle, often three-lobed ; upper surface 

 bright green and glabrous ; lower surface pale green and with slight pubescence 

 on the midrib and nerves ; rachis glabrous. 



Flowers dioecious, without petals, appearing with the leaves, from buds in the 

 axils of the leaf-scars of the previous season, staminate flowers in fascicles, pistillate 

 in narrow pendulous racemes. Fruit, with narrow acute nutlets, diverging at an 

 acute angle, and thin reticulate, straight or falcate wings. 



In winter, the terminal buds are about \ inch long, acute, with four tomentose 

 ciliate external scales ; lateral buds appressed to the twigs, with two outer visible 

 scales ; opposite leaf-scars united around the twig, narrowly crescentic, three-dotted, 

 fringed with hairs on the margin. 



Varieties f 



The species, extending over a vast territory, varies considerably in the wild 

 state, the typical form described above occurring in the eastern part of its distribution. 

 Farther west, in Colorado, Utah, and New Mexico, the branchlets and leaves become 

 pubescent ; and in California, an extreme form is met with, which is often considered 

 to be a distinct species : * 



I. Var. calif ornicum, Wesmael, Bull. Bot. Soc. Bel^. 43 (1890); Sargent, 

 Garden and Forest, iv. 481 (1891), Silva N. Amer. ii. 112, t. 97 (1892), and Trees 

 N. Amer. 643 (1905). 



Acer californicum, Dietrich, Syn. ii. 1283 (1840). 



Negundo californicum, Torrey and Gray, Fl. N. Amer. i. 250, 684 (1838). 



This is distinguished, according to Sargent, by its darker-coloured bark ; buds 

 covered with dense tomentum ; short pale persistent pubescence on the branchlets 

 and ripe fruit ; leaflets three, larger, more coarsely serrate, and more frequently 

 lobed than in the type, and coated beneath with pale pubescence. As seen in 

 cultivation at Kew, the leaflets are usually five and not three ; and in the wild state, 

 5-foliolate leaves are occasionally met with, as in a specimen in the Kew herbarium 

 collected by Lobb in California. The pubescence on the leaflets beneath is most 

 strongly marked on the midrib and nerves, is whitish in colour, and forms prominent 



