120 BULLETIN 56, UNITED STATES NATIONAL MUSEUM. 



Cereus pringlei Watson, extends to within a few miles of the Boun- 

 dary near this point, but nowhere crosses the Internationa] Line. 



Other trees seen on this journey were the small-leaf horse bean, 

 whose habitat is quite general, that of the true palo verde (Cercid- 

 ■ ii in torreyanum) being restricted to the edges of arroyos. The So- 

 noran ironwood was quite generally distributed and unusually large. 

 The indigo thorn (Parosela spinosa) , locally called mangle, was abun- 

 dant all along the Sonoyta, but did not appear again until the Tide 

 Mountains were reached. Mesquites were occasionally seen, and on 

 them the red-berried mistletoe grew, as it did upon all of the trees 

 mentioned, excepting the mangle and cacti. Ocotillo, yerba de la 

 flecha, pitaya, and bisnaga were abundant. 



Station No. (50. — Camel Skeleton, a mile north of Monument No. 

 181, 729 kilometers (453 miles) west of the Rio Grande, and 130 

 kilometers (81 miles) east of the Colorado River. Altitude. 215 

 meters (801 feet). Small collections were made at this camp, in the 

 midst of the Tule Desert, February 9 and 10. 1894. 



Station No. Gl. — Tule Wells, Yuma County. Arizona, about 6 

 kilometers (3| miles) northeast of Monument No. 186, 7G3 kilometers 

 (474 miles) west of the Rio Grande, and 96 kilometers (GO miles) 

 east of the Colorado River. Altitude, 375 meters (1,230 feet). 

 There are two ordinary wells at this place, which is in the midst of 

 a wild and rugged desert range called the Tule Mountains, though 

 there are no signs of tides or other aquatic vegetation in the region, 

 and no water on the surface of the ground. The mountains reach 

 an altitude of 75G meters (2,480 feet), and are rocky and barren, 

 the rock consisting of granite, quartz, hornblende-mica-andesite, and 

 basalt. Cacti (Cactus, Echinocactus, Cereus, and Opuntia), an 

 Ac/are, and a few stunted palo verde and ironwood trees grow on 

 their rocky sides, and in some of the canyons an enormous nolina, 

 with a tall caudex, which is sometimes a meter or more in diameter, 

 grows sparingly. Along the arroyos a dusty-looking, spiny tree, 

 Parosela spinosa is abundant, the largest individuals reaching the 

 height of 8 meters. Mesquites and large-leaved palo verde, iron- 

 wood, asclepias, creosote bush, and sagebrush are found about the base 

 of the mountains and along dry water courses. There is water in a 

 few places in the mountains, in tanks which are small and hard to 

 find. Plants and animals were collected from February 9 to 14, 

 L894, by myself and assistant. 



FJora of Tule and Granite Mountain*. — No large collections were 

 made in the vicinity of this station. So barren are these desolate 

 ranges that the occurrence of an arborescent nolina (Nolina bigelovii 

 Watson). Inning a caudex and ilmverstalk together measuring 7 

 meters in height, was a surprise. An agave, in a new form, reap- 



