Genus i. 



MIMOSA FAMILY. 



331 



I. Acacia angustissima (Mill.) Kuntze. Prairie Acacia. Fig. 2429. 



Mimosa angustissima Mill. Gard. Diet. Ed. 8, no. 19. 



1768. 

 Mimosa filiculoides Cav. Ic. i : 55. pi. 7S. 1791. 

 Acacia filicina Willd. Sp. PI. 4: 1072. 1806. 

 Acacia filiculoides Trelease ; Branner & Coville, Rep. 



Geol. Surv. Ark. 1888: Part 4, 178. 1891. 

 A. angustissima Kuntze, Rev. Gen. PI. 3^; 47. 1898. 



A low thornless shrub, varying from glabrous to 

 hirsute-pubescent. Pinnae of the leaves 2-15 pairs, 

 oblong in outline, 1-2' long; leaflets 10-50 pairs, 

 oblong or linear-oblong, about 2" long, less than 1" 

 wide, obtuse or acute, slightly inequilateral, i-veined; 

 heads globose, many-flowered, axillary, slender- 

 peduncled, 6"-io" in diameter; sepals distinct or 

 nearly so ; filaments yellow, 3-4 times as long as the 

 sepals ; pod linear, acute, often narrowed at the base, 

 stipitate, mostly straight, l'-2' long, about 3" wide, 

 flat, its valves thin, reticulated, glabrous or pubes- 

 cent, impressed between the seeds. 



Prairies, plains and bluffs, Missouri and Kansas to Texas, Arizona and Mexico. May-July. 



2. ALBIZZIA Durazz. Mag. Tosc. 3^: 11. 1772. 



Unarmed trees, with large bipinnate leaves, widely spreading branches, and perfect or 

 polygamous capitate pink or white flowers, the heads sometimes panicled. Calyx tubular 

 to campanulate, S-lobed. Corolla f unnelf orm. Stamens numerous, longer than the corolla ; 

 filaments united near the base of the corolla. Pods linear, flat, 2-valved, the margins of the 

 valves not separating from them. [In honor of Albizzi, an Italian naturalist.] 



About 50 species, natives of warm and tropical regions of the Old World, the following typical. 



I. Albizzia julibrissin Durazz. Pink Siris. 

 Silk-tree. Fig. 2430. 



A, julibrissin Durazz. Mag. Tosc. 3*: 11. 1772. 



A tree, up to 35° high, and trunk diameter of l4°, 

 the bark thin and scaly, the slender twigs smooth, 

 reddish-brown. Leaves 8'-i6' long, with 8-16 pairs of 

 pinnae; the rachis tipped by a spine; leaflets 25 to 35 

 pairs, oblong, inequilateral, acute, 5"-8" long, revolute- 

 margined, dark green above, pale green and pubescent 

 beneath ; heads panicled, about 2' in diameter ; flowers 

 pink; stamens more than i' long; ovary short-stalked; 

 pod 4'-6' long, narrowed at both ends, papery ; seeds 

 oval, flat, 4"-5" long. 



Virginia to Florida and Louisiana. Naturalized from 

 southern Asia. April-July. 



3. ACUAN Medic. Theod. Sp. 62. 1786. 



[Desmanthus Willd. Sp. PI. 4: 1044. 1806.] 

 [Darlingtonia DC. Ann. Sci. Nat. 4: 97. 1825.] 



Perennial herbs or shrubs, with bipinnate leaves, small stipules, and greenish or whitish 

 small regular flowers in axillary peduncled heads or spikes. Flowers perfect, sessile, or the 

 lowest sometimes staminate, neutral or apetalous. Calyx campanulate, its teeth short. 

 Petals valvate, distinct, or slightly united or coherent below. Stamens 10 or S, distinct, 

 mainly exserted ; anthers all alike. Ovary nearly sessile; ovules 00. Pod linear, straight or 

 curved, acute, glabrous, flat, several-seeded, 2-valved, the valves coriaceous or membranous. 



About 10 species, natives of warm and tropical America, one of them widely distributed in 

 tropical regions of the Old World. Type species : Mimosa virgata L. 



Pods few, linear, erect, straight. i. A. leptoloba. 



Pods numerous in globose heads, oblong, curved. 



A. illinoensis. 



