PLANT ECOLOGY AND FLORISTICS OF SALTON SINK. 93 



A careful study of the vegetation of this area, correlated with analyses of the soils 

 in which the dififerent plants grow, would doubtless yield definite and accurate results 

 explanatory of its distribution. In the absence of such studies only a cruder and more 

 general account can be presented. 



The dominant plants of this area are all of Chenopodaceous genera. They are Atri- 

 plex lentiformis, A. polycarpa, A. canescens, Suceda torreyana, and Spiroslachys occi- 

 dentalis. A composite, a variety of Isocoma veneta, occupies an important subordinate 

 position. These several species do not grow intermixed, or at most are intermingled only 

 on the borders of the portions respectively occupied by each. Whether the soil shall be 

 monopolized by Atriplex, or by the other two chenopods, appears to depend upon the alka- 

 line content, the latter enduring larger percentages. 



ATRIPLICETA OF THE INDIO-MECCA FLATS. 



The three species of Atriplex above named hold possession of the larger part of this 

 area, their distribution being determined by the amount of water in the soil. Those parts 

 in which the water-content is greatest is occupied by Atriplex lentiformis. This is a vigor- 

 ous species with leaves broader and greener than those of the others. It grows either in 

 thickets close as a hedge, or isolated in great domes, G to 8 feet, and exceptionally even 

 12 or 15 feet in height and base diameter. The same requirement of a very damp soil 

 is manifested elsewhere in its position about springs and on river banks. 



Where the soil is somewhat drier Atriplex polycarpa forms a nearly pure stand. Its 

 habit of growth is similar to that of A. lentiformis, but mostly in thickets, and less fre- 

 quently in dense entangled individuals, in neither case much over 3 feet in height. Its 

 leaves are narrowly linear, short, and in color gray. 



The third species, Atriplex canescens, has great ecological adaptability, so that while 

 reaching its best development on the drier margins of these flats, it also is frequent in the 

 most arid soils. In such situations it grows in individual isolation, one low shrub more or 

 less distant from its neighbors, but on the flats it is gregarious and forms close thickets, 

 about 3 feet in height. It has the fewest, the smallest, and the grayest leaves of any of 

 the three species, the foliage development of each being in accordance with the amount 

 of moisture in the soil in which they grow. 



In October and November, the season of their fruitage, the Atriplices of the flats 

 are so laden with heavy panicles of fruit that they seem as if thatched with them. These 

 are of a bright green color, which is especially manifest in the broad fruit-wings of A. 

 canescens, and the fruit of A. polycarpa is frequently tinged with red. By this adaptation 

 the fruit obtains the benefit of a large chlorophylious surface at the time of ripening, while 

 the sparse foliage of small gray leaves minify the excessive insolation of summer. WTien 

 thus loaded with fruit these homely shrubs have a cheerful and elegant appearance. 



SUj^DETA and SPIROSTACHETA OF THE INDIO-MECCA AREA. 



Those parts of the flats where the alkaline content exceeds the amount tolerated by 

 any of the Atriplices, and perhaps differs in saline composition, are given over to two 

 other chenopodaceous plants, Suceda torreyana and Spiroslachys occidentalis. 



As it grows in these flats, Suwda is an erect suffrutescent plant, 2 to 4 feet high, with 

 numerous slender, much intertangled branches, which are distantly set with small, terete, 

 succulent leaves. It is often gregarious in habit, and is notably high and thick-set on 

 soil which has been denuded of its original vegetation. In such places it is the first plant 

 to establish itself. 



Spiroslachys occidentalis also has terete leaves, which are larger, more numerous, and 

 more succulent than those of Suceda, the only other true succulent of the flats. Both 

 appear, where an open interval permits, as subordinates in the Atriplex associations, but 



