6 THE AMERICAN BOTANIST 



ted appearance, owing to the tendency of all the plants to take 

 on hemispherical forms. In all but the driest locations the 

 greasewood {Sarcohatus renniciilatus) is the dominant shrub, 

 its fat cylindrical leaves strung along the branches suggesting 

 the fronds of ferns. Other conspicuous shrubs are the big 

 rabbit-brush {Chrysothanimis graveolens) and various species 

 of shadscale {Atriplex). Interspersed with these usually 

 grows the low rabbit-brush {ChrysotJiauuiiis fUif alius) ; in 

 fact, the round, yellow-green clumps of this plant are so abun- 

 dant over thousands of square miles hereabouts as to become 

 exceedingly tiresome to the eye. Scarcely less abundant is 

 the rayless goldenrod (Isocoiua lictcrophylla) which forms 

 similar, though larger, hemispheres of green. 



With the exception of several species of Opuntia, cacti 

 are rare. A narrow-leaved yucca is abundant and also the 

 joint fir or Mormon tea {Ephedra liridis). Here and there 

 the dry and shifting surface of the sand dunes were splashed 

 with vivid green where the Russian thistle {Salsola pcstifcr) 

 has established itself. The plant is reported to have entered 

 the region about 1890 but it now has all the appearances of a 

 native. It produces immense rounded clumi)S. often four feet 

 or more across. Sheep and goats eat the young plants with 

 avidity and even the yuccas and joint Ins do not entirely es- 

 cape. 



'I'rees of any kind are. of course, rare in the desert, but 

 as one climbs to elevations of a mile or more above sea-level, 

 the one-seeded juniper (Jiinipcnis iiwuospcrnia) and the 

 ])inon ])ine (Piiiiis iiiouof'hylla), begin to appear and with 

 them the sage-brush {.IrteniisU tridcntata). This latter 

 l)lant. so abundant in many localities, is almost entirely absent 

 from the \icinitv of Tuba. 



One does \mA study tlie vegetation long before discover- 

 ing that three floras meet in this region. Tlierc is first the 



