** Leaves twice pinnate; stipules present.
a Leaves unequally twice pinnate, 2°—4° long, deciduous; leaflets serrate, 2′—3′ in length; branches and stem armed with scattered prickles.Aralia ([p. 778]). aa Leaves equally twice pinnate, usually smaller; branches unarmed or armed with stipular or axillary spines (in Parkinsonia often apparently simply pinnate). b Leaflets crenate; leaves simply or twice-pinnate on the same plant, deciduous, usually armed with simple or branched axillary spines.Gleditsia ([p. 607]). bb Leaflets entire. Leaflets 2—2½′ long; leaves deciduous; branchlets stout, unarmed.Gymnocladus ([p. 605]). Leaflets smaller; leaves usually persistent; branchlets slender. Branches armed with prickles or spines. Leaves with 2 or rarely 4 pinnæ. Branches armed with axillary spines or spiny rachises. Pinnæ with 4—8 leaflets; branches with short axillary spines.Cercidium ([p. 613]). Pinnæ with 8—60 leaflets; branches armed with spiny rachises or rigid branchlets terminating in stout spines.Parkinsonia ([p. 611]). Branches armed with stipular prickles; leaves persistent. Pinnæ with many oblong to linear leaflets.Prosopis ([p. 599]). Pinnæ with 1 pair of orbicular to broad-oblong leaflets.Pithecolobium unguis-cati ([p. 586]). Leaves with 6, or more, rarely 4, pinnæ. Prickles usually spreading, often recurved.Acacia ([p. 591]). Prickles usually more or less ascending, straight.Pithecolobium ([p. 586]). Branches unarmed. Branchlets and petioles glabrous; leaves with 2—5 pair of pinnæ, each with 40—80 leaflets.Lysiloma ([p. 589]). Branchlets and petioles pubescent while young; leaves with 5—17 pair of many-foliolate pinnæ, or pinnæ 2—4 and each with 8—16 leaflets.Leucæna ([p. 596]).
*** Leaves simply pinnate.
a Leaves equally pinnate. Stipules wanting. Leaflets 2—4, generally oblong-obovate.Exothea ([p. 714]). Leaflets 6—12. Leaflets obtuse, usually oblong-obovate. Leaflets 8—12, 2′—3′ long, pale below; leaves occasionally opposite.Simarouba ([p. 642]). Leaflets 6—8, 1′—1½′ long, green below.Xanthoxylum coriaceum ([p. 637]). Leaflets 6—8, acuminate.Swietenia ([p. 648]). Stipules present. Branches armed with infra-stipular spines in pairs; leaflets 10—15, usually oblong-obovate, ½′—¾′ long, persistent.Olneya ([p. 626]). Branches unarmed; leaflets 20—46, ovals ½′—⅔′ long.Eysenhardtia ([p. 620]). aa Leaves unequally pinnate. b Stipules present. Leaflets sharply serrate; leaves deciduous; winter-buds resinous.Sorbus ([p. 390]). Leaflets entire or crenately serrate. Leaves deciduous. Leaflets 7—11, 3′—4½′ long; branches unarmed. Leaflets usually alternate, thin and glabrous at maturity.Cladrastis ([p. 618]). Leaflets opposite, coriaceous, pubescent beneath at least along the veins.Ichthyomethia ([p. 628]). Leaflets 9—21, 1—2 cm. long. Branches usually with stipular prickles, sometimes viscid.Robinia ([p. 622]). Branches unarmed, not viscid; leaflets 13—19, elliptic.Sophora affinis ([p. 617]). Leaves persistent. Leaflets 7—9, oblong-elliptic, 1′—2½′ long; branches unarmed.Sophora secundiflora ([p. 616]). Leaflets 10—15; branches prickly.Olneya ([p. 626]). bb Stipules wanting. d Leaves persistent. Leaflets long-stalked (sometimes nearly sessile in Xanthoxylum flavum). Leaflets oblong-ovate, cuneate at base. Leaflets acuminate, glabrous.Picramnia ([p. 643]). Leaflets obtuse, tomentose when unfolding.Xanthoxylum flavum ([p. 636]). Leaflets broad-ovate, usually rounded or subcordate at base.Metopium ([p. 658]). Leaflets sessile or nearly so. Petiole and rachis winged. Leaflets crenate, obovate, about ½′ long; branches prickly.Xanthoxylum Fagara ([p. 634]). Leaflets entire. Leaflets oblong, usually acute, 3′—4′ long.Sapindus saponaria ([p. 712]). Leaflets spathulate, rounded at apex, not more than ¾′ long.Pistacia ([p. 656]). Petiole and rachis not winged. Leaflets 7—19, acuminate, 2′—5′ long.Sapindus marginatus ([p. 713]). Leaflets 21—41, obtuse, ½′—¾′ long.Alvaradoa ([p. 644]). dd Leaves deciduous. Leaflets long-stalked, 3—7, entire, acute.Bursera ([p. 645]). Leaflets sessile or nearly so. Branches prickly; leaflets crenate.Xanthoxylum clava-Herculis ([p. 635]). Branches unarmed. Juice milky or viscid; leaflets serrate or entire; rachis sometimes winged.Rhus species 1—3 ([p. 660]). Juice watery. Rachis without wings. Leaflets entire, acuminate, 7—9.Sapindus Drummondii ([p. 714]). Leaflets serrate or crenate. Winter-buds large; leaflets 5—23, aromatic. Winter-buds naked.Juglans ([p. 169]). Winter-buds covered with scales.Carya ([p. 176]). Winter-buds minute, globose, scaly; leaflets 5—7, ovate, not aromatic.Ungnadia ([p. 717]). Rachis winged; leaflets 10—20, entire, rounded at apex, not more than ¼′ long.Bursera microphylla ([p. 647]).
TREES OF NORTH AMERICA
(Exclusive of Mexico)
Class 1. GYMNOSPERMÆ.
Ovules and seeds borne on the face of a scale, not inclosed in an ovary; resinous trees, with stems increasing in diameter by the annual addition of a layer of wood inside the bark.
I. PINACEÆ.
Trees, with narrow or scale-like generally persistent clustered or alternate leaves and usually scaly buds. Flowers appearing in early spring, mostly surrounded at the base by an involucre of the more or less enlarged scales of the buds, unisexual, monœcious (diœcious in Juniperus), the male consisting of numerous 2-celled anthers, the female of scales bearing on their inner face 2 or several ovules, and becoming at maturity a woody cone or rarely a berry. Seeds with or without wings; seed-coat of 2 layers; embryo axile in copious albumen; cotyledons 2 or several. Of the twenty-nine genera scattered over the surface of the globe, but most abundant in northern temperate regions, thirteen occur in North America.