DEPARTMENT OF BOTANICAL RESEARCH. 65 



lected earlier in the season, probably in March. In order to form any 

 comprehensive notion of these aquatic plants it probably will be neces- 

 sary to have samples taken for a number of years to come, or at least 

 until the water has reached an almost stable condition. 



One of the problem.s in connection with the Salton is the process by 

 which the tufa deposits are formed. As pointed out by Jones (Carnegie 

 Inst. Wash. Pub. 193, p. 23) and suggested by Walcott (Smithsonian 

 Miscellaneous Collections, vol. 64), this may be due to algse, and cer- 

 tainly the evidence collected by Jones strongly supports such a hypo- 

 thesis. There is also a possibility of the deposition of carbonates being 

 due to bacteria, or indeed it may be the result of the combined action 

 of these two groups of organisms. The only way to understand why 

 and under what circumstances tufa is deposited, with the solution of 

 the various other problems involved, is to discover b}'^ what organism 

 and in what way the bicarbonates present are decomposed and the 

 resulting carbonates laid down in the characteristic tufa formation. 

 Good material for an investigation of this point was obtained at the 

 Salton Sea, but the most promising collection was made near Reno, 

 Nevada. Attempts are now being made to isolate in pure cultures some 

 of the algal organisms associated with the forming of tufa, and if this 

 can be done successfully, it may be possible to discover something of 

 the actual processes involved. 



The bacterial side of the investigation has been delegated to Mr. 

 Karl F. Kellerman, of the United States Department of Agriculture. 

 The samples thus far furnished him have been insufficient to enable 

 him to draw any definite conclusions. 



Origin of the Tufa Deposits of the Interior Basins, by J. C. Jones. 



The work begun in the Salton Sink has been carried to the basin of 

 Lake Lahontan and it has been found that the blue-green algae and 

 associated bacteria are probably concerned in some manner with the 

 deposition of most of the tufa found in the latter basin. Remnants 

 of algae have been found in all the Lahontan tufas, except the thino- 

 litic form, and while the relation between the development of tufas and 

 the light exposure is not so evident as in the Salton, yet in all other 

 respects the evidence is essentially the same in the two basins. The 

 tufa forming at present in Pyramid Lake is lithoid in character, appar- 

 ently on account of the low content of calcium of the lake w^aters. Lab- 

 oratory experiments have been started through the cooperation of Dr. 

 G. T. Moore, in which it is hoped to develop tufas under controlled 

 conditions. 



Measurements of the more perfect thinolite crystals indicate aragon- 

 ite as the original mineral. It has been found that calcium carbonate 

 is deposited from the water of Pyramid Lake as aragonite when a sat- 

 urated solution of calcium bicarbonate is added. 



