562 



Indigo Bush 



are narrowly oblong, pendent, smooth, pointed, about 1.5 cm. long, nearly straight, 

 and usually bear only one flat seed. 



The wood is hard and dense, reddish brown, with a specific gravity of 0.87. 



IX. INDIGO BUSH 



GENUS PAEOSELA. CAVANILLES 



Species Parosela spinosa (A. Gray) Heller 



Dalea spinosa A. Gray 



HIS small spiny tree, or more often a much branched shrub, occurs in 

 the deserts of southern California, southwestern Arizona ajttd adjacent 

 Mexico. Its maximum height is 6 meters, with a trunk diameter up 

 to 5 dm. It is also called Dalea and Indigo thorn. 

 The trunk is usually very short, branching near the base. The bark is about 5 

 mm. thick, deeply fissured into grayish brown scales. The twigs are slender, finely 

 hairy; spines 5 cm. long or less. The leaves are few near the bases of the spine- 

 like twigs, consisting of but one leaflet, 

 which is wedge-shaped, about 2 cm. long, 

 blimtly pointed, sessile or nearly so, wavy 

 and glandular on the margin, and whitish 

 hairy; they fall off soon after unfolding. 

 The flowers appear in June or July in 

 racemes 2.5 to 4 cm. long, the white 

 hairy rachis spine-tipped; they are short- 

 stalked; the calyx-tube is lo-ribbed, 

 glandular between the ribs, its blunt lobes 

 ovate; the petals are dark blue; stamens 

 united into a tube, the anthers all alike, 

 often vrith a gland, 2-celled and opening 

 lengthwise; ovary sessile, hairy and glan- 

 dular; style slender; ovules usually 2. 



Fig. 520. — Indigo Bush. 



The fruit is a one-seeded, compressed ovate pod about 8 mm. long, partly enclosed 

 by the persistent calyx and tipped by the withering style; seed kidney-shaped, 

 about 3 mm. long, shining, brown and mottled. 



The wood is soft, rather coarse-grained, and brown ; its specific gravity is about 

 0.55. Seedling plants bear oblong or oblanceolate toothed leaves sometimes 4 

 cm. long. 



The genus is wholly American, comprising about 100 species of herbs, shrubs 

 and a few trees, most of them being native in the southwestern United States, 

 Mexico and Central America. 



The generic name is an anagram of Psoralea, a genus of closely related plants. 

 The type species is Dalea obovatifoUa Ortega, a Cuban herbaceous species. The 



