36 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



called cats claws, and claim a place second only to the cacti in popu- 

 lar detestation. Scarcely less familiar and annoying are the mem- 

 bers of the buckthorn family, among them the genera CondnVta^ 

 Zhyplius^ Ccanothus, C olvhrhia^ and Rhamnas. There are also spiny 

 shrubs of the families Oleace<e, Saxifrxigacea'^ RosacecB^ and many 

 others. None are more undisguised and openh' aggressive than 

 Kwherlmia^ A^hich is necessarily avoided and more easily forgiven 

 than the '* ocotillo,'" which tempts one to grasp a handful of cool 

 leaves in riding ]:)ast, ouly to find that every leaf conceals a dagger. 



Among the remarkable plants of the mountains of the Western 

 Desert Tract are wood}^ species of milkweed, of FJuphorhia, and of 

 Tereh in tli us ( B ursera ) . 



Several genera of the family Astcracew are coarse and woody. 

 Aster spinosus groAvs in masses resembling asparagus in sandy soil 

 beside streams; Baecharis of several species, Ilymenodea, and arrow- 

 wood (Phfchea sericea) form close thickets beside streams or in moist 

 valleys or canyons in the hills, and even the genera Trixls and Senecio 

 in some species develop into large bushes. 



Further details respecting the distribution of the coarser forms of 

 vegetation along the Boundary will be given in the description of 

 the principal collecting stations. A collection of plants aggregating 

 4,085 numbers and about 10,000 specimens, from the Mexican Boun- 

 dary Line, was made and turned over to Mr. Frederick V. Coville, 

 Botanist of the United States Department of Agriculture, for the pur- 

 pose of being reported upon. As the report has not yet been prepared, 

 a list of the trees is here given, togetlier with such notes regarding 

 their abundance and transverse and vertical distribution as have 

 ]">een retained, some knowledge of the forest trees being essential in 

 order to enable the student to acquire an intelligent understanding 

 of the habitat, distribution, and life history of the diiferent animals. 

 The following list of 119 species of forest trees found on the Mexican 

 Boundarv is not inclusive of those peculiar to the lower Rio Grande 

 Valley: ^ 



LIST OF TREES OF THE MEXICAN BOUNDARY LINE. 



PINUS STROBIFORMIS Engelmann. 



MEXICAN WHITE PINE. 



This tree was found at the summits of the main peaks of the San 

 Luis Mountains, south of the Boundary Line (altitude 2,-tOO meters, 

 or 7,874 feet). It was also found on the Animas Peaks (altitude 

 2.677 meters or 8,783 feet) in New Mexico. In the San Jose Moun- 

 tains (altitude 2,541 meters or 8,337 feet), Sonora, a few trees were 

 found close to the sunmiit of the main peak. It is a common tree 

 on the highest peaks of the Huachuca Mountains, where it occupies 



