112 SILVA OF NORTH AMERICA. SAPINDACEZ. 
or oval, acute, rounded, or wedge-shaped at the base, and coarsely and irregularly serrate above the 
middle, or sometimes three-lobed, the lower surface being coated with tomentum when they unfold, and 
at maturity are smooth or more or less pubescent; they are membranaceous, prominently veined, light 
bright green, paler on the under than on the upper surface, two to four inches long and two or three 
inches broad, and are borne on stout petiolules, that of the terminal leaflet being often an inch long, or 
twice the length of those of the rather smaller lateral leaflets. The sterile and fertile flowers appear on 
separate trees, and expand just before or with the leaves from buds developed in the axils of the last 
leaves of the previous year, the sterile flowers fascicled on slender hairy pedicels an inch and a half to 
two inches in length, the fertile flowers in narrow drooping racemes. The flowers are minute, apeta- 
lous, and yellow-green, with a hairy calyx which is five-lobed and campanulate in the sterile flower, and 
in the fertile flower is much smaller and divided to the base into five narrow sepals. There are four to 
six stamens in the sterile flower, with slender exserted hairy filaments and long linear anthers surmounted 
by the pointed end of the connective. The ovary, which is placed on a narrow rudimentary disk, is 
covered with pubescence, and is only partly inclosed by the calyx; the styles separate at the base into 
two long stigmatic lobes. The fruit, which attains its full size early in the summer, hangs on stems an 
inch or two inches long, in graceful racemes six or eight inches in length; it ripens in the autumn 
and drops from the stems which remain upon the branches until the following spring; the samaras 
are an inch and a half to nearly two inches long, with narrow acute nutlets diverging at an acute angle, 
and with thin reticulate-veined straight or falcate wings, the margin undulate towards the apex. The 
seed is narrowed at each end, and is half an inch in length, with a thin coat, narrow thin cotyledons, 
and a rather long radicle. 
Acer Negundo is one of the most widely distributed, and in some parts of the country one of the 
commonest, trees of the North American forest. It occurs on the banks of the Winooski River and 
of Lake Champlain in Vermont, on the shores of Cayuga Lake in New York, in eastern Pennsylvania, 
and ranges to Hernando County, Florida, and northwestward to Dog’s Head Lake in Winnipeg and 
along the southern branch of the Saskatchewan to the eastern base of the Rocky Mountains; in the 
United States it is found as far west as the eastern slopes of the Rocky Mountains in Montana, the 
Wahsatch Mountains in Utah, western Texas, New Mexico, and eastern Arizona, extending south 
along the mountain ranges of northeastern Mexico. The Box Elder inhabits the banks of streams and 
lakes and the borders of swamps; it is comparatively rare in all the region east of the Appalachian 
Mountains, and is much more common in the basin of the Mississippi, being most abundant and reach- 
ing its greatest size in the valleys of the streams which flow into the lower Ohio River. Here it 
flourishes in the deep rich moist and often inundated bottom-lands, forming a large part of the growth 
under the Oaks, Hickories, and Gum-trees, which in such situations rise to a great height. It is mingled 
with Willows, the Elm, and the Hackberry on the banks of the streams which flow through the midcon- 
tinental plateau almost to the western limit of tree-growth, while in the central mountain region it is 
confined to valleys five or six thousand feet above the level of the sea. 
In western Texas and in New Mexico the pubescence which clothes the young shoots and the under 
surface of the leaves of the Box Elder increases in thickness and is persistent, and the eastern tree is 
thus gradually connected with the variety’ which in California is found on the banks of streams in the 
valley of the lower Sacramento River, and in the interior valleys of the coast ranges from the Bay of 
1 Acer Negundo, var. Californicum, Sargent, Garden and Forest,iv. Jahrb. vii. 213. — Wesmael, Gen. Acer, 27. — Greene, Fl. Francis. 
148. i. 76. 
Negundo Californicum, Torrey & Gray, Fl. N. Am. i. 250, 684.— Negundo aceroides, Torrey, Pacific R. R. Rep. iv. 74; Bot. Mex. 
Hooker & Arnott, Bot. Voy. Beechey, 327, t. 77.— Walpers, Rep. Bound. Surv. 47; Bot. Wilkes Explor. Exped. 259 (not Moench). — 
i, 410.— Bentham, Pl. Hartweg. 301.— Nuttall, Sylva, ii. 90, t. Bolander, Proc. Cal. Acad. iii. 78. 
72. — Koch, Dendr. i. 545.— Brewer & Watson, Bot. Cal. i. 108. Negundo aceroides, var. Californicum, Sargent, Garden and For- 
Acer Californicum, Dietrich, Syn. ii. 1283. — Pax, Engler Bot. est, ii. 364. 
