560 



TREES OF NORTH AMERICA 



aud coriaceous, convex by the growth of the seeds, contracted between and beyond 

 them, longitudinally striate. Seeds oblong, suspended longitudinally on slender 

 fuuicles; 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 three 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; legumes 1-8-seeded 12-18' long; leaves 7'-8' long; rachises of the pinnae flat, 

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



Flowers in short racemes ; petals valvate in the bud ; stamens long-er than the petals ; 

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

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



1. Parkinsonia aculeata, L. Retama. 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 rachises, 12'-18' long; primary 

 leaves on young branches, with 2-4 pinnae, and spinescent rachises developing into 

 stout ridged persistent short-pointed chestnut-brown spines I'-l^ long and marked 

 near the base by the prominent scars left by the fall of the pinnse ; their stipules per- 

 sistent, appearing as lateral spiny branches on the spines ; secondary leaves fascicled 



//^^<3 



from the axils of the primary leaves, with short terete spinescent rachises and 2 

 pinnse; pinnae flat, 7'~8' long, wing-margined, acute at the apex, with 25-30 pairs of 

 ovate or obovate petiolulate leaflets, t^^'-|' long. Flowers appearing on the grow- 

 ing branches during the spring and summer, and in the tropics throughout the year, 

 in slender erect racemes 5'-6' long; petals bright yellow, the upper one marked 



