212 BOTANICAL GAZETTE [march 



7-8 cm. long and 6-7 cm. wide; petioles slender, compressed, 

 4-7 cm. in length. Flowers not seen. Fruit in slender, glabrous 

 aments 7-8 cm. long, oblong-ovate, acute, deeply pitted, glabrous, 

 thin-walled, 3-valved, 8-9 mm. long, the disk slightly lobed, 

 2 . 5-3 mm. in diameter; pedicels slender, 3-4 cm. in length. Seeds 

 ovate, acuminate, 4 mm. long. 



A tree up to 20 m. high, with a trunk sometimes i m. in diameter, and 

 stout more or less pendulous branches, stout, glabrous, pale yellow-brown 

 branchlets, and acuminate, glabrous winter-buds. 



In canyons and along the streams of northwestern Texas, where it appears 

 to be the only cottonwood. Low sandy banks of the Canadian River, Cana- 

 dian, Hemphill County, E. J. Palme/, June 17, 1918 (no. 14107); creek banks, 

 Amarillo, Potter County, E. J. Palmer, July 13, 1917 (no. 12541); canyon, 

 Paloduro Creek, Randall County, E. J. Palmer, October 3, 1918 (no. 14591); 

 river banks in canyon, Gamble's Ranch, Armstrong County, June 6, 1918 

 (no. 13959). "One of the largest trees found in Paloduro Canyon, growing in 

 the protection of high bluffs. It usually grows in the protection of high bluffs 

 or at the heads of canyons. The young trees here are slender and straight, 

 but older specimens are very irregular or unsymmetrical in growth, with pale 

 or dark ashy bark. It is rarely found in the more open parts of the canyon 

 here, but near Canyon City it grows on the river margins" (E. J. P. in litt.); 

 Post, Garza County, E. J. Palmer, May 31, October i, 1918 (nos. 13848-, 13853, 

 14575); along creeks. Sweet Water, Nolan County, E. J. Palmer, October 21, 

 1917, May 28, September 28, 1918 (nos. 13045, 13799 type, 13899, 14526). 



By the shape of the leaves and by the thickness and color of the branchlets 

 this species cannot be distinguished from P. Wislizenii Sargent, but from that 

 species it is well distinguished by the smaller fruit on much shorter pedicels and 

 by the glabrous winter-buds. The range of the two trees is also quite different. 



PoPULUS Macdougallii Rose, Smithsonian Misc. Coll. 61:61. 



1 9 13. — This species, of which I have not seen the flowers, is well 



distinguished from P. Fremontii by the minute disk of the fruit, 



which does not exceed 3 mm. in diameter. The fruit is borne on 



slender, glabrous pedicels 3-5 mm. in length, in racemes 5-6 cm. 



long; it is ovate and acute at apex to ellipsoidal and acute or 



acuminate at ends, glabrous, slightly pitted, thin-walled, 3-valved, 



1Q-12 mm. in length. The seed is oblong-ovate, acuminate, 3 mrn. 



in length. 



It is probably always a small tree with erect branches and slender branch- 

 lets pubescent or puberulous when they first appear, soon becoming glabrous 

 and pale yellow -brown at the end of their first season. 



