MIMOSACEAE 579 



oblique, small and in many pairs or large and in few pairs : flowers mostly perfect, sessile, 

 in dense heads. Calyx 5-lobed. Corolla of 5 distinct petals. Stamens 10, exserted. 

 Ovary stalked. Style filiform. Ovules numerous. Pods broadly linear, flat. Seeds 

 crosswise in the pod. 



Leaves with 14-18 pairs of pinnae : branches tomentose : leaflets less than 1.5 mm. broad. 



1. L.pulvendenta. 

 Leaves with 2-10 pairs of pinnae : branches glabrous or glabrate : leaflets over 1.5 mm. broad. 



Leaflets 20-40, mostly thrice as long as broad : pods with membranous valves. 2. L. glauca. 



Leaflets 12-16, mostly less than twice as long as broad : pods with leathery valves. 3. L. retusa. 



1. Leucaena pulveru!6nta Benth. A small tree, sometimes 18 m. tall, with finely 

 pubescent inflorescence. Leaves 1-2 dm. long, with 28-36 pinnae ; leaflets 60-120, the 

 blades narrowly oblong, acute: peduncles often clustered, 1-3.5 cm. long: heads globose, 

 1-1.5 cm. in diameter: calyx campanulate, 1-1.5 mm. high; lobes obtuse : petals linear- 

 spatulate, about thrice as long as the calyx, pubescent near the tip : stamens hardly twice 

 as long as the petals : pods linear, 10-20 cm. long. 



In rich soil, southern Texas and Mexico. Spring. 



2. Leucaena glauca (L. ) Benth. A small tree, sometimes 10 m. tall, with spread- 

 ing branches and tomentose twigs. Leaves 1-3 dm. long, with 6-20 pinnae ; leaflets 20-40, 

 the blades narrowly oblong to lanceolate, oblique, 6-12 mm. long, acute : peduncles tomen- 

 tose, 1-4 cm. long : heads globose, 1-3 cm. in diameter : calyx obconic, 1 mm. long, sub- 

 tended by peltate bracts ; lobes obtuse : petals linear-oblong or linear-spa tulate, erect, 

 more than twice as long as the calyx, pubescent : stamens nearly thrice as long as the 

 petals : pods linear, 10-15 cm. long, acute or acuminate at both ends. 



In sandy or rocky soil, Florida to Texas and Mexico. A native of tropical America, now widely 

 distributed in all tropical regions. Spring. 



3. Leucaena retusa Benth. A shrub, with tomentose twigs. Leaves 1-2 cm. long, 

 with 4-10 pinnae ; leaflets 12-16, the blades leathery, oblique, obovate or ovate to oval or 

 oblong, 1-3 cm. long, prominently nerved, usually apiculate : peduncles 5-8 cm. long : 

 heads globose, about 2 cm. in diameter : calyx obconic, 3-3.5 mm. long : pods linear, 

 15-25 cm. long, acute or acuminate at both ends. 



On plains and prairies, southern Texas and New Mexico. Spring. 



9. ACUAN Medic. 



Perennial unarmed herbs or somewhat shrubby plants. Leaves with 2-pinnate blades : 

 leaflets numerous. Flowers in peduncled greenish or whitish head-like spikes, perfect, or 

 the lower ones staminate or neutral, and sometimes apetalous. Calyx 5-lobed. Corolla of 

 5 distinct or slightly united petals. Stamens 5-10, exserted : filaments distinct or nearly 

 so. Ovary nearly sessile. Ovules numerous. Pods very narrow or oblong, unarmed, 2- 

 valved. Seeds lengthwise or oblique in the pod. [Desrnanthus Willd.] 



Stamens 5. 



Pods 4-6 mm. wide, in compact heads : peduncles longer than the pods. 1. A. Ittinoensis. 



Pods 2 mm. wide, in loose clusters : peduncles shorter than the pods. 2. A. leptoloba. 



Stamens 10. 



Leaves mostly with 8-12 pinnae. 



Stems glabrous or nearly so : peduncles 1-2 cm. long. 3. A. Jametti. 



Stems velvety pubescent : peduncles 2.5-5 cm. long. 4. A. velutina. 



Leaves mostly with 2-6 pinnae. 

 Peduncles 1-2.5 cm. long. 



Leaf-rachis and its branches glabrous : leaflets not ciliate. 5. A. depressa. 



Leaf-rachis and its branches pubescent : leaflets ciliate. 6. A. acuminata. 



Peduncles 4-12 cm. long. 



Pinnae mostly with 12-18 leaflets : leaflets glaucous beneath, glabrous or nearly 



so: pods 3 mm. wide. 7. A. reticutata. 



Pinnae mostly with 20-28 leaflets : leaflets ciliate and pubescent beneath : 



pods 2 mm. wide. 8. A. fallax. 



1 Acuan Illinoe~nsi3 (Michx. ) Kuntze. Stems erect or ascending, 3-10 dm. tall, 

 sparingly branched, glabrous or nearly so : leaves with 20-28 pinnae ; leaflets numerous, 

 the blades linear-oblong, 2.5-3.5 mm. long, acute, not reticulated : peduncles 2.5-8 cm. 

 long, usually shorter than the subtending bracts : spikes less than 1 cm. in diameter : pods 

 oblong, numerous, 1.5-2 cm. long, curved and slightly spirally twisted, in heads 2-3 cm. 

 in diameter. [Desrnanthus brachylobus (Willd.) Benth.] 



In dry soil, and on river banks, Minnesota to Tennessee, Florida, Colorado and Texas. Spring and 

 summer. 



2, Acuan leptoloba (T. & G. ) Kuntze. Stems ascending, 3-10 dm. tall, sparingly 

 branched, with scabrous angles : leaves with 10-20 pinnae ; leaflets numerous, the blades 



