76 SILVA OF NORTH AMERICA. LEGUMINOS&. 
abruptly enlarged at the base, and, like the rachises, flattened and grooved on the upper side; they are 
eighteen to twenty-eight-foliolate or sometimes bipinnate, with four to seven pairs of pinne, which 
increase in length towards the apex of the leaf, the upper pair being four or five inches long and 
the lowest often single leaflets; when they unfold they are covered with thick white tomentum; at 
maturity they are pubescent on the petioles and rachises, on the short stout petiolules, and on the under 
surface of the midribs of the leaflets. The leaflets are 
lanceolate-oblong, rather unequal at the base by the greater development of the upper side, acute or 
slightly rounded at the apex, remotely crenulate-serrate, dark green and lustrous on the upper surface, 
dull yellow-green on the lower surface, and from one to one and a half inches long and half an inch 
broad. The flowers are produced in June, when the leaves are nearly fully grown, from the axils of 
those of the year or of previous years, the staminate in short many-flowered pubescent racemes, which 
In autumn they turn a pale clear yellow. 
lengthen after the flowers begin to open, and which at maturity are from two to two and a half inches 
in length and often clustered, the pistillate in slender graceful few-flowered and usually solitary racemes 
two and a half to three and a half inches long. The flower-buds are nearly globose, and are covered 
with hoary orange-colored pubescence persistent on the outer surface of the calyx after the flowers have 
opened. The calyx is campanulate, narrowed at the base, its acute lobes, which have thick revolute 
ciliate margins and thickened tips and are covered on the two surfaces with white hairs, being rather 
shorter than the erect acute petals and half their width. The stamens are exserted, with slender fila- 
ments pilose towards the base and green anthers. The pistil is occasionally bicarpellary and is coated 
with thick white tomentum. The legumes, which are twelve to eighteen inches long or sometimes 
much shorter,’ dark brown, pilose and slightly faleate with straight thickened margins, are borne two 
or three together in short racemes on stalks an inch or an inch and a half in length; their walls are 
thin and tough, with a thin papery inner coat, and contain a quantity of pulp between the seeds; they 
contract in drying with a number of cork-screw twists, and fall late in the autumn or in early winter. 
The seeds are oval, flattened, and a third of an inch in length, with thin albumen and orange-colored 
embryos. 
Gleditsia triacanthos grows naturally on the western slope of the Alleghany Mountains in 
Pennsylvania, and ranges westward through southern Ontario® and Michigan to eastern Nebraska and 
Kansas, and to about longitude 96° west in the Indian Territory, and southward to northern Alabama and 
Mississippi, and to the valley of the Brazos River in Texas. East of the Alleghany Mountains it 
It inhabits the borders of 
streams and intervale lands, growing in the most fertile soils with the Black Walnut, the Shellbark 
Hickory, the Red Elm, the Blue Ash, the Box Elder, and the Kentucky Coffee-tree, usually singly, but 
sometimes so multiplied as to form the prevailing tree-growth over considerable areas; or less commonly 
it is found ‘on dry and sterile gravelly hills like those of central Kentucky to which the name of 
“barrens” has been given, and upon which it is the characteristic and often the prevailing tree. In 
the valleys of the smaller streams of southern Indiana and Illinois Gleditsia triacanthos attains its 
greatest size and majesty. Here individuals may still be found from one hundred and twenty to one 
hundred and forty feet in height, with trunks six feet in diameter and free of branches for sixty or 
seventy feet.* In less favorable situations and in poorer soil it is low, stunted, wide-branched, and often 
covered with thorns. 
has often become naturalized by seeds scattered from cultivated trees. 
1 Gleditsia brachycarpa, Pursh, Fl. Am. Sept. i. 221.— De Can- 
dolle, Prodr. ii. 479.— Sprengel, Syst. iii. 919. — Don, Gen. Syst. 
ii, 428. — Loudon, Arb. Brit. ii. 653. — Dietrich, Syn. v. 539. 
G. triacanthos, var. brachycarpos, Michaux, Fl. Bor.-Am. ii. 257. — 
Torrey & Gray, Fl. N. Am. i. 399. — Sargent, Forest Trees N. 
Am. 10th Census U. S. ix. 59. 
4 The contraction of the walls of the pods of Gleditsia triacanthos 
seems to be intended to facilitate the distribution of the seeds. 
Without this provision they would remain where they fall under 
the trees, but the pods thus twisted roll like wheels, and, being 
very light, are blown for great distances over the frozen ground 
and especially over the snow. The obstacles they are obliged to 
overcome in their journeys probably help to break open the pods 
and liberate the seeds. 
8 J. W. Burgess, Bot. Gazette, vii. 95. 
4 Ridgway, Proc. U. S. Nat. Mus. 1882, 64. 
