46 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Mountains of New Mexico west to the Pajaritos Mountains of Ari- 

 zona and Sonora. It is a pretty tree, with brittle branches and thick 

 leaves which are pale and glaucous on the under surface. In young 

 ■trees the bark is smooth and greenish. The longstalk willow often 

 grows with Salice nigra. On the streams of Chihuahua and Sonora 

 the two were often seen side by side. 



SALIX AMYGDALOIDES Andersson. 

 AIMONDLEAr WILLOW. 



This is the commonest willow of the Rio Grande from El Paso to 

 Fort Hancock, Texas, where it forms thickets on the islands and low 

 banks of the stream. 



SALIX LAEVIGATA Bebb. 

 SMOOTHLEAF WILLOW. 



This is a large, handsome tree, with rough, blackish bark and 

 glossy leaves. It 'is a common species on the banks of streams which 

 flow into the Pacific Ocean. It was onlj' found west of the Coast 

 Range Mountains. 



SALIX FLUVIATILIS Nuttall. 

 LONGLEAF WILLOW. 



The longleaf willow is a common tree along the Colorado River 

 from the Gila to the Gulf of California, flowering in April. On the 

 Salton and New rivers — branches of the Colorado — of the Western 

 Desert, it was the most abundant tree. It was also found at Jacumba 

 Hot Springs, on the Pacific slope of the Coast Range, opposite a 

 deep notch in those mountains through which several desert plants 

 and animals have reached the west side. This is usually a smaller 

 tree than the black willow {Salix nigra) . 



SALIX ARGOPHYLLA Nuttall. 

 CANESCENT WILLOW. 



This silky-leaved willow appears to be verj' distinct fi'om Salix 

 fluviatilis. It was found on the east side of the Coast Range Moun- 

 tains, in California and Lower California. 



SALIX TAXIFOLIA Humboldt, Bonpland, and Kunth. 

 YEWLEAF WILLOW. 



This is a beautiful little tree, usually not more than .15 to .3 meters 

 in diameter and 5 to 6 meters (15 to 20 feet) in height. (See Plate IV, 

 fig. 2. The bark is flaky, light gray, and rough. This species can 

 exist in drier soil than any other willow of the region, -and will grow 

 wherever a mesquite could find sufficient moisture. We found it from 



