DEPARTMENT OF BOTANICAL RESEARCH. 51 



the concentrated brine shows a solution of remarkable composition as well 

 as concentration. In these two respects it forms an extraordinary habitat 

 for living organisms and presents problems of great physiological interest. 

 The difficulties of the investigation are so great that progress is necessarily 

 slow. In spite of this, enough definite results have been reached to encour- 

 age the student in further work. 



A chromogenic bacillus has been isolated which has some economic impor- 

 tance. In addition to the existence of these micro-organisms in brine, they 

 are found also on the crude salt produced in these salterns. As this salt is 

 sometimes used without purification, they may be transferred to the material 

 with which the salt is mingled and thus come into another and quite different 

 environment. In this only the chromogenic bacteria have attracted attention. 

 It is unlikely, however, that the others disappear or are entirely inactive, and 

 further effort will be made to determine their fate. 



Geological, Climatic, and Vegetational Features Presented by the Otero 

 Basin, by Mr. B. B. Free. 



Some information — interesting, especially in comparison with the Salton — 

 has been obtained by a reconnaissance of the Otero Basin in south central 

 New Mexico. Geologically this basin is a long, narrow, dropped block be- 

 tween two outward-tilted mountain ranges: the White and the Sacramento 

 mountains on the east, the Organs and San Andreas on the west. As usual 

 in arid basins, the valley has been deeply filled with alluvial material washed 

 in from the surrounding mountains. The topography of the floor is also 

 quite typical : a fairly steep bajada on alluvial slopes at the foot of the moun- 

 tains merging into a flat and featureless plain which sinks very gently to a 

 central playa. 



In recent geologic time the basin has been occupied by a very variable lake 

 fluctuating in response to changes in climate, overflowing in wet periods, re- 

 treating in dry, and leaving the records of these climatic vicissitudes in the 

 deposits of its bottom and the topography of its borders. Of these deposits, 

 the earliest whose history can be read with any surety are the beds of reddish 

 gypsiferous, calcareous, and sometimes saline clay exposed in many places 

 lo to 30 feet under the surface of the basin, and which are almost certainly 

 the deposits of this old lake during its last period of great expansion and 

 overflow and during the first part of the following period of contraction and 

 concentration. These so-called ''red beds" are covered nearly everywhere 

 by beds of granular, somewhat consolidate gypsum which are believed to be 

 materials deposited at the borders and on the final dry playa of this evapo- 

 rating lake and afterward whipped into dune form by the arid winds. This 

 gypsum is so widespread in the basin that one must assume for its formation 

 a long and intense period of aridity and of dune movement. This arid period 

 was followed by a period of greater rainfall and of expansion of the lake, 

 with resultant fixation, planation, and consolidation of the gj'^psum dunes. 



