MIMOSA CEA E. 5 2 7 



Family 14. MIMOSACEAE Reichenb. 

 Mimosa Family. 

 Herbs, shrubs or trees, with alternate, commonly 2-3-pinnate 

 leaves, the stipules various, and small regular mostly perfect flowers in 

 heads, spikes or racemes. Calyx 3-6-toothed or 3-6-lobed, the teeth or 

 lobes mostly valvate in the bud. Corolla of as many distinct or united 

 petals, also valvate. Stamens distinct, or monadelphous. Ovary i-celled ; 

 style simple. Fruit a legume. Seeds without endosperm ; cotyledons 

 fleshy. About 30 genera and 1350 species, mostly tropical. 



Stamens numerous, at least more than 10. 1. Acacia. 

 Stamens only as many as the petals, or twice as many. 

 Petals separate ; pod smooth. 



Pod separating into 2 valves. 2. Acuan. 



Pod leathery, indehiscent. 3. Prosopis. 



Petals united to about the middle ; pod spiny. 4. Morongia. 



1. ACACIA Adans. 



Shrubs or trees, with bipinnate leaves,- the ultimate leaflets usually small and 

 numerous, or the leaves in many exotic species modified into flat simple phyllodes. 

 Flowers small, in heads or spikes. Calyx campanulate, usually 4-5 -toothed, or of 

 4 or 5 distinct sepals. Petals mostly 4 or 5 or wanting. Stamens exserted; fila- 

 ments filiform; pollen-grains cohering in 2's-6's. Pod linear, oblong or oval, flat 

 or swollen, often constricted between the seeds. [Greek, point, or thorn, many spe- 

 cies being thorny.] About 450 species, chiefly in subtropical regions. Besides 

 the following, some 15 others occur in the southern U. S. 



1. Acacia filicoides (Cav.) Trelease. Prairie Acacia. (I. F. f. 2028.) 

 A thornless shrub. Pinnae of the leaves 2-15 pairs, oblong in outline, 2-5 cm. 

 long; leaflets 10-15 pairs, oblong or linear-oblong, about 4 mm. long, less than 2 

 mm. wide, slightly inequilateral, 1 -veined; heads globose, many-flowered, axillary, 

 slender-peduncled, 1-2 cm. in diameter; sepals distinct or nearly so; filaments yel- 

 low; pod linear, acute, stipitate, mostly stright, 2-5 cm. long, about 6 mm. wide, 

 flat, its valves thin, reticulated, impressed between the seeds. Prairies Mo. and 

 Kans. to Tex., Ariz, and Mex. May-July. 



2. ACUAN Medic. [DESMANTHUS Willd.] 

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



whitish small regular flowers in axillary peduncled heads or spikes. Flowers per- 

 fect, sessile, or the lowest sometimes staminate, neutral or apetalous. Calyx cam- 

 panulate, its teeth short. Petals valvate, distinct, or slightly united or coherent 

 below. Stamens 10 or 5, distinct, mainly exserted; anthers all alike. Ovary nearly 

 sessile; ovules 00 . Pod linear, straight or curved, acute, flat, several-seeded, 

 2-valved. the valves coriaceous or membranous. About 10 species, natives of warm 

 and tropical America, one widely distributed in tropical regions of the Old World. 

 Pods few, linear, erect, straight. 1. A. leptoloba. 



Pods numerous in globose heads, oblong, curved. 2. A. Illinoensis. 



i. Acuan leptoloba (T. & G.) Kuntze. Prairie Mimosa. (I. F. f. 2029.) 

 Stems ascending, rough-angled, 6-9 dm. long. Leaves short-petioled, bipinnate; 

 pinnae 5-10 pairs, sessile ; leaflets 10-24 pairs, sessile, linear-lanceolate, acute, 

 inequilateral, rounded at the base, usually glabrous, 3-4 mm. long, 1 mm. wide or 

 less; peduncles 1-2.5 cm. long, few-flowered; stamens (always?) 5; pods 3-8, nar- 

 rowly linear, acuminate, about 3 times the length of the peduncle, 6-8-seeded. 

 Prairies. Kans. to Tex. Summer. 



2 Acuan Illinoensis (Michx.) Kuntze. Illinois Mimosa. (I. F. f. 2030.) 

 Glabrous or nearly so ; stems angled, 3-9 dm. high. Foliage resembling that of 

 the preceding, but the pinnae and obtusish leaflets are sometimes more numerous ; 

 peduncles 2-8 cm. long; pods numerous, densely capitate, oblong or lanceolate, 

 strongly curved, 1.5-2.5 cm. long, acute, slightly impressed between the 2-5 seeds. 

 Prairies and river-banks, Ind. to Ky., Fla., S. Dak. and Tex. May-Sept 



