18 



RUTACEAE 



ulate cymes. Flowers polygamous, greenish white. Calyx-lobes 4 or 5, imbricate. Petals 

 4 or 5, longer than the calyx-lobes. Stamens as many as petals and alternate with them, 

 the filaments hairy on the inner side, present in the pistillate flower but not fertile. Ovary 

 compressed, 2-celled or rarely 3-celled; ovules 2 in each cell. Fruit a samara, with a 

 reticulate wing completely encircling the body. [Greek name of the elm, which has simi- 

 lar fruit.] 



A genus of 3 species, native of the United States and Mexico. The foliage is variable, which has led some 

 authorities to recognize a much larger number of species. Type species, Ptelea trifoliata L. 



1. Ptelea crenulata Greene. Western Hop-tree. Fig 3005. 



Ptelea crenulata Greene, Pittonia 1:216. 1888. 



Ptelea Baldzvinii var. crenulata Jepson, Fl. W. Mid. Calif. 249. 1901. 



Small tree, 3-5 m. high, the young twigs pubescent. Leaves somewhat pubescent, glabrate in 

 age ; leaflets 3, rarely 5, elliptical to ovate or especially the terminal one often obovate, 2-6 cm. 

 long, more or less crenate; petals 4-6 mm. long; filaments hairy only near the base; samara 

 1-2 cm. long, fully as broad, the wing emarginate at both ends ; style persistent. 



Canyons and bottomlands. Upper Sonoran Zone; Inner Coast Ranges and Sierra foothills from Shasta 

 County to Tulare and Santa Clara Counties, California. Type locality: no definite locality given in the original 

 description. April-June. 



2. THAMNOSMA Torn & Frem. in Frem. Second Rep. 313. 1845. 



Small, strong-scented, glandular, desert shrubs. Leaves simple, alternate, entire, some- 

 times reduced to scales. Flowers in racemes or racemose cymes, perfect. Sepals and petals 

 4. Stamens 8, inserted on the cup-like disk. Ovary 2-celled, deeply 2-lobed, stipitate ; style 

 filiform; stigma capitate; ovules 5 or 6 in each cell. Fruit a leathery capsule, _2-lobed, de- 

 hiscent at the apex. Seeds reniform, [Name Greek, meaning bush and odor, in reference 

 to the strong odor of these plants.] 



A genus of 2 species inhabiting the arid southwestern United States and northern Mexico. Type species, 

 Thamnosma tnontana Torr. & Frem. 



1. Thamnosma montana Torr. & Frem. Turpentine Broom. Fig. 3006. 



Thamnosma montana Torr. & Frem. in Frem. Second Rep. 313. 184S. 



Strong-scented shrub, 3-5 dm. high, the stems freely branching, broom-like, yellowish green 

 and thickly beset with pustulate glands. Leaves 2-10 mm. long, oblanceolate, or linear, few and 

 early deciduous; flowers in loose terminal racemes, 8-12 mm. high; petals dark purple, erect; 

 fruit distinctly stipitate, deeply parted into 2 nearly globose lobes; seeds dark brown, smooth 

 or slightly wrinkled. 



Sandy or rocky ridges. Lower Sonoran Zone: Mojave and Colorado Deserts, California to southern Utah, 

 Arizona, New Mexico, Sonora, and Lower California. Type locality: Virgin River, southeastern Nevada. 

 March-May. 



3005. Ptelea crenulata 



3006. Thamnosma montana 



3007 

 3007. Cneoridium dumosum 



