5° BOTANICAL GAZETTE [JULY 
of the river, but it by no means exhausts the interesting features of 
the region. If the low-lying contiguous areas to the westward capable 
of being flooded are included, the delta may be said to have an 
area approximately equal to the state of Connecticut. One arm 
extends over 200%" to the northwestward and includes the Salton 
Basin, with its exposed bottom more than 130™ below the level of 
the sea. Although the summer floods of extreme height find their 
Fic. 2.—View of Rio Colorado at a point where it cuts into the desert mesa of 
Sonora a few kilometers south of international boundary; looking downstream; Populus 
and Salix on right bank; dense forest of Populus in background on left bank; portion 
of mesa in foreground on left bank with Covillea, Stillingia, and Ephedra; Station 3- 
way by old channels into this basin, creating a temporary lake of 
great extent, yet the district affected must be classed as desert, since 
the highly saline character of the soil and prevailing low humidity 
and precipitation support representative types of vegetation (fig. 4).° 
Other basins ordinarily dry, with saline deposits, are to be found in 
various parts of the depressed area, which has the characteristics of 
a sea-floor of comparatively recent date. 
9 See also COVILLE and MacDovucat, The Desert Botanical Laboratory of the 
Carnegie Institution (November 1903), pp. 21-22. pls 
