152 



American Midland Naturalist Monograph No. 4 



when covered with bright yellow flowers which later develop into small, white- 

 woolly pods. The stems are sometimes covered with a gummy substance 

 which the Indians of the Southwest used as a glue or cement to mend broken 

 baskets. A hot water decoction of the herbage was used as a liniment for 

 treating collar sores in draft horses. ^ 3 The herbage is of no use as a browse, 

 probably because of the resinous substance which gives the plants a strong 

 aromatic odor. The stems bum easily, green or dry, and make a hot fire. 

 Some think that burning stems give off the odor of creosote, hence the 

 common name, creosotebush. 



Occurrence. — ZION: Coalpits Wash, 4,000 feet, grand canyon, in the canyon: 

 lower Toroweap Valley west of park boundary. 



Orange Family (Rutaceae) 



Field Guide to the Genera 



Broom-like, nearly leafless shrub; leaves not more than Yi inch long, not divided 

 nor toothed; flowers dark purple; fruits small heart-sha{>ed capsules 

 THAMNOSMA, p. 152. 



Leafy shrub or small tree; leaves divided into 3 leaflets, the leaflets % to 3 inches 

 long; flowers greenish white; fruits small flattened roundish structures 

 winged all around PTELEA, p. 152. 



Mohave Desert-rue, Turpentine Broom, (Thamnosma montana 

 Torr. & Frem.). — Freely-branching, broom-like shrub 1 to 2i/2 feet high, the 

 stems thickly covered with glandular swellings; leaves few, small, 1/6 to 1/2 

 inch long, oblong, soon falling; flowers blackish purple, about % inch long, 



borne singly along the stems; 

 petals 4, usually remaining erect; 

 fruits 1/3 to nearly i/^ inch across, 

 deeply parted into two roundish, 

 inflated sections and tapering to 

 the base. A decoction of the herb- 

 age was used as a tonic by the 

 Indians and early settlers. 



Occurrence. — grand canyon, in 

 the Canyon, 3,700 to 6,500 feet: Her- 

 mit Basin; Bright Angel trail; Pipe 

 Creek; Clear Creek trail below Phan- 

 tom Point; Kaibab trail on the Tonto 

 north of the Colorado River. 



Baldwin Hoptree (Ptelea 

 Baldwini Torr. & Gray), fig. 87. 

 — Shrub, or small tree 6 to 20 

 feet high; bark whitish; leaflets 3, 

 elliptic to oblong with rounded or 

 pointed tips, % to 2% inches 



Fig. 87. Baldwin hoptree (Ptelea Baldwini). 



33 Jepson, W. L. Flora of California, vol. 2, p. 439. 1936. 



