ZYGOPHYLLACEAE. 221 



2, Ealstroemia hirsutissima Vail. On plains and prairies from Kans. and 

 Colo, to Tex. and N. M. ; also Mex. — Cafion City ; Pueblo. 



2. COVILLEA Vail. Creosote Bush. 



I. Covillea tridentata (DC) Vail. {Larrea mexicana Moricand) Arid 

 districts from Colo, and Utah to Tex. and S. Calif. — " So. Colo.," exact 

 locality not given. 



Family 76. RUTACEAE Juss. Rue Family. 



Fuit a capsule; leaves unifoliolate ; stamens 8. i. Thamnosma. 



Fruit an indehiscent samara ; leaves 3-foliolate ; stamens 4-5. 2. Ptelea. 



I. THAMNOSMA Torn & Frem. 



I. Thamnosma texanum Torr. Dry plains from Colo, to Tex. and N. 

 Mex. ; also in Mex. — Alt. up to 5400 ft. — Soda spring ledge, Canon City 

 {Brandegee). 



2. PTELEA L. Hop-tree, Water Ash. 



Samara truncate at the apex. i. P. angustifolia. 



Samara emarginate at the apex. 2. P. crenulata. 



1. Ptelea angustifolia Benth. Along streams from Colo, to Tex. and N. 

 M. ; also in Mex. — Caiion City; Florence. 



2. Ptelea crenulata Greene. Along streams from Colo, to N. M. and Calif. 

 — Brantly Canon, Las Animas Co. 



Order 29. POLYGALALES. 



Family 77. POLYGALACEAE Reichenb. Milkwort Family. 

 I. POLYGALA L. Milkwort. 



Stems herbaceous, unarmed ; keel with a fimbriate crest. 



Perennial; leaves alternate. i. P- alba. 



Annual ; leaves verticillate. 2. P. verticillata. 



More or less spiny undershrubs ; keel not crested, but with a beak. 



Plant 5-15 cm. high; flowers 7-10 mm. long. 3. P. subspinosa. 



Plant 6-10 dm. high; flowers 3-4 mm. long. 4. P. acanthoclada. 



1. Polygala alba Nutt. On plains from S. D. to Tex. and Ariz.— Exact 

 locality not given. 



2. Polygala verticillata L. On grassy places from Que. and Sask. to Fla. 

 and Colo. — Clear Creek. 



3. Polygala subspinosa S. Wats. On dry mesas from Colo and Nev. to 

 N. M. and Ariz. — Alt. about 5000 ft. — Grand Junction; Gunnison Mesa. 



4. Polygala acanthoclada A. Gray. In dry valleys from Colo, and Nev. to 

 Ariz. — San Juan Valley. 



Order 30. EUPHORBIALES. 



Styles and stigmas distinct or mainly so, cleft or foliaceous ; ovary 3-celled (rarely 



2-celled) ; land-plants. 78. Euphorbiaceae. 



Styles united by pairs ; ovary 4-celled ; small water- or mud-plants. 



79. Callitrichaceae 



