LEGUMINOS.E 611 



states to the valley of the Brazos River, Texas, and northward through western Louisiana 

 and southern Arkansas to northwestern Mississippi, middle Kentucky and Tennessee, 

 the bottoms of the Mississippi at La Pointe, Saint Charles County, Missouri, western and 

 southern Illinois and southwestern Indiana; rare east of the Mississippi River and only in 

 deep river swamps; very abundant and of its largest size westward on rich bottom-lands; 

 in Louisiana and Arkansas often occupying extensive tracts submerged during a con- 

 siderable part of the year. 



9. PARKINSONIA L. 



Trees or shrubs, with smooth thin bark and terete branches often armed with simple 

 or 3-forked spines. Leaves abruptly bipinnate, alternate or fascicled from earlier axils, 

 short-petiolate, the rachis short and spinescent, with 2-4 secondary elongated rachises 

 bearing numerous minute opposite entire leaflets without stipels; stipules short, persistent 

 and spinescent, or caducous. Flowers perfect on thin elongated jointed pedicels from 

 the axils of minute caducous bracts, in slender axillary solitary or fascicled racemes: 

 calyx short-campanulate, 5-lobed, the lobes slightly inbricated or subvalvate in the bud, 

 narrow, membranaceous, nearly equal, becoming reflexed, deciduous; petals bright yel- 

 low, unguiculate, much longer than the lobes of the calyx, spreading, the upper petal rather 

 broader than the others and glandular at the base of the claw; stamens 10, inserted in 2 

 rows on the margin of the thin disk, free, slightly declinate, those of the outer row opposite 

 the sepals and rather longer than the others; filaments villose below the middle, the upper 

 filament enlarged at base and gibbous on the upper side; anthers uniform, versatile; ovary 

 short-stipitate, pilose, contracted into a slender filiform incurved style infolded in the bud 

 and tipped with a minute stigma; ovules numerous, suspended from the inner angle of the 

 ovary. Legume linear, torulose, acuminate at the ends, 2-valved, the valves thin, convex 

 by the growth of the seeds, contracted between and beyond them, longitudinally striate. 

 Seeds oblong, suspended longitudinally on a slender funicle; hilum minute, near the apex; 

 seed-coat thin, crustaceous, light brown; embryo inclosed on the sides only by thick layers 

 of horny albumen: cotyledons oval, flat, slightly fleshy, the radicle very short and straight. 



Parkinsonia, with four species, is confined to the warm parts of America and to southern 

 Africa. Two species occur within the limits of the United States. 



The genus is named for John Parkinson (1567-1650), an English botanical author, and 

 herbalist to James I. 



CONSPECTUS OF THE NORTH AMERICAN SPECIES. 



Flowers in long slender racemes; petals imbricated in the bud; stamens shorter than the 

 petals; legume 1-8-seeded, 12'-18' long; leaves 7'-8' long; rachis of the pinnae flat, 

 wing-margined, 50-60-foliolate; branches with spines. 1. P. aculeate (G, H). 



Flowers in short racemes; petals valvate in the bud; stamens longer than the petals; 

 legume 1-2-seeded; leaves about 1' long; rachis of the pinnae terete, 8-12-foliolate; 

 branches without spines. 2. P. microphylla (G, H). 



1 . Parkinsonia aculeate L. Retema. Horse Bean. 



Leaves of two forms, short-petiolate, persistent, light green and glabrous, except for 

 a few hairs on the lower part of the young secondary rachis, 12'-18' long; primary leaves 

 on young branches, with 2-4 pinnae, and a spinescent rachis developing into a stout ridged 

 persistent short-pointed chestnut-brown spine !'-!$' long and marked near the base by 

 the prominent scars left by the fall of the pinnae; stipules persistent, appearing as lateral 

 spiny branches on the spines; secondary leaves fascicled from the axils of the primary 

 leaves, nearly sessile with a short terete spinescent rachis and 2 pinnae; puma? flat, 12'-18' 

 in length, wing-margined, acute at apex, with 25-30 pairs of ovate or obovate petiolulate 

 leaflets, iV-J' long. Flowers appearing on the growing branches during the spring 



