PLANT ECOLOGY AND FLORISTICS OF SALTON SINK. 91 



contrasts vividly with the gray and parched aspect of the gravelly desert plain in which 

 it is situated, and above which it is elevated on a low mound of black earth, formed by 

 the decay of its vegetation and the accumulation of the dust carried by the wind and 

 detained by the moisture of the spring. The water stands in a pool in the summit of 

 this elevation, but there is no run-off. It is strongly impregnated with sulphureted hydro- 

 gen and is also slightly saline. The entire pool is filled with a dense growth of robust 

 Scirpus olneyi. Surrounding this, the damp soil of the mound is covered with a sod of 

 Distichlis spicata, and bordering this is a sparse fringe of the shrubs Spirostachys occi- 

 dentalis and Pluchea sericea. 



DOS PALMAS. 



This spring is situated also in the northeastern part of the Sink and only 2 feet below 

 its upper contour line. It is at the mouth of a wide wash which drains a large part of the 

 Chuckawalla Mountains, from which source its waters are derived. Below it is a broad 

 playa, flooded occasionally by the torrential storm waters which come down the wash. 

 It consists of a swampy pool of considerable area, retained by a slightly elevated border 

 of black earth, which is strongly impregnated with alkali. The water is tepid and very 

 slightly saline, and only sufficient in volume to maintain the pool without needing an 

 outlet. It is filled with robust Scirpus olneyi, for the most part so dense as to exclude 

 other plants, but in places intermixed with Typha latifolia and a little Juncus cooperi. 

 In the middle of the scirpetum grows a fine specimen of Salix nigra and the two lofty 

 Washingtonias which give the spring its name. On its margin Pluchea camphorata is 

 mingled with the sedge, and in the moist saline soil which borders the swampy pool Anem- 

 opsis californica forms a narrow intermittent belt, in which grow scattered shrubs of 

 Baccharis viminea. Beyond the immediate border, but still in soil somewhat damp, are 

 considerable areas of Distichlis, with a scattered growth of Pluchea sericea, Prosopis pubes- 

 cens, and large domes of Alriplex lentiformis. 



AGUA DULCE AND FIGTREE JOHN SPRrNGS. 



There are several of these springs, alike in character, scattered within a distance of 

 2 or 3 miles on the southwest side of the Salton Sea, which at the height of its recent re- 

 plenishment reached most of them. Its shore is now fully half a mile distant. Rising, as 

 these springs do, from an artesian source, the water, while tepid, is pure and sweet. Their 

 character is similar to that of Dos Palmas — swampy pools grown up with Scirpus olneyi 

 and Typha latifolia. Some afford sufficient water to irrigate small gardens, and there 

 are large tracts of damp soil covered with a sod of Distichlis, in which grow clumps of 

 Juncus cooperi. About them are well-grown trees of black willow, delta Cottonwood, 

 and Washington palm, all of which have probably been planted by the Indians, who have 

 made their homes here for generations. 



SC1RPUS-TYPHA ASSOCIATION OF ALAMO AND NEW RIVERS. 



The margins of the two diffluents of the Colorado which flow through Imperial Valley 

 are bordered by a close growth of Typha latifolia and Scirpus paludosus, which pushes 

 into the water until its depth exceeds 6 or 8 inches, and creeps up on the mire of the low 

 muddy banks. The width of this zone, therefore, varies in accordance with the character 

 of the stream. Where, in its meanderings, it crowds closely to the bluffs there is room for 

 but a narrow belt, but on the opposite side it may extend, in the shallow water and over 

 the mud flats, as much as 200 to 300 feet, or even more. The two species do not inter- 

 mingle, but are mutually exclusive, nor is their respective occupancy determined by 

 hydrophytic conditions. Either may occupy the entire border of the stream, or either 

 may have possession of the water front, leaving the landward margin to the other; but 

 always the gregarious colonies are of considerable extent and exclude all other vegetation. 



