42 THE AMERICAN BOTANIST 



ert plants are nearly all woody perennials and, of course, are 

 conspicuous features of the desert at any time of the year. 



The plants of the oasis, proper, are more often herbaceous 

 perennials or, in some cases, annuals and are not limited to cer- 

 tain seasons of growth, as the other plants arc, by a lack of 

 water. The vegetation of the springs, seeps, rills and reser- 

 voirs is the usual one. The plants have the appearance of the 

 water plants in other parts of the world and, in fact, consist 

 of the identical species that inhabit more humid regions. 



No matter from what direction Tuba is approached, the eye 

 picks it out while still far distant, for the deep green of its spiry 

 poplars and clustering fruit trees is in sharp contrast to the 

 prevailing red and gray of the desert. After a long trip over 

 the shifting sand dunes and bare rocks of the adjacent region 

 the sight of its verdure is a most welcome one. The transi- 

 tion from desert to arable land at Tuba is always so sudden as 

 to be noticeable. The hot red sands come up to the very edge 

 of the oasis and push in wherever the boundaries are not de- 

 fended b\- water. The oasis itself is so circumscribed as to 

 appear like an island. There is no spot within its confines 

 from which the desert is not visible 



Owing to the close contact of the desert and oasis, it is some- 

 times difficult to decide to which region certain plants on the 

 b(3rder-land belong. In niakin,!:; up the accompanying list, how- 

 ever, I have chosen to exclude those species that are found 

 pretty generally distributed in the desert, ainiin,<; in this discus- 

 sion to present only tliose plants that one might expect to find 

 in any locality in the! desert where water comes to the surtace. 

 In a later paper the flora of the desert, itself, will be considered. 



The arborescent flora of the oasis is limited 'to the species 

 brought in by the white inhabitants. Most important and con- 

 spicuous arc llic I.oinbardv poplars which are sn constantly 



