502 BOTANICAL GAZETTE [JUNE 
necessary energy, under optimum conditions, at least roo —— of ieee 
hydrate for every pound of nitrate formed.2* Under no conceiv 
could the algal flora of a soil supply any substantial portion of the 250 tons of 
dextrose needed for such fixation. 
e most recent contribution to the subject is a study of the nitrate content 
of the country rock by Stewart and PETERsoN.”? While working primarily 
in Utah, these authors have collected and analyzed large numbers of sand- 
stones, limestones, and shales from widely separated localities throughout 
Utah, Wyoming, and Colorado. These may be considered fairly representa- 
tive of the country rocks occurring in the area covered by the cretaceous and 
tertiary seas. They find that while the Jurassic sandstones and shales are 
tertiary sandstones everywhere contain nitrates far in excess of the quantities 
present in ordinary alkali-free soils, often to the amount of one to ten tons per 
acre-foot; while the tertiary shales have prevailingly an even higher nitrate 
content. Over very extensive, wholly barren areas of virgin “clay hill” soil 
there is present beneath the compact, impermeable surface clay a layer of ash- 
like material, two to six inches in thickness, bearing 0.15 to 0.20 per cent of 
sodium nitrate, an amount equal to goo to 36,000 pounds per acre-foot. The 
authors estimate the total nitrate content of the Book Cliffs area in Utah and 
Colorado as being many times greater than that of the deposits of Chile, but 
have nowhere found concentrations of such extent and character as would 
permit them to be profitably worked, a situation resembling that found by 
FREE% in southern California. STEWART and PETERSON consider that the dis- 
covery that nitrate deposits are not confined to the shales, but are generally 
present in the country rock, and that their amounts are everywhere materially 
greater than has been hitherto supposed, constitutes conclusive proof that 
“niter spots” are accumulations resulting from leaching, and have no relation 
to bacterial activities in the soil. In view of the very large accumulation of 
evidence against the latter hypothesis and the conclusive character of the 
results obtained by Stewart and his co-workers, this conclusion would appear 
to be wholly justified —Josepn S. CALDWELL 
Some temperature effects.—In discussing some of the phytogeographic 
effects of winter temperature, SHREvE* calls attention not only to the great 
lack of critical data, but more especially to the fundamental error, so prevalent 
** MARSHALL, C. E., Microbiology. Philadelphia: Blakiston & Co. 1912. PP- 
272-273. 
22 STEWART, ROBERT, and PETERSON, nae ye ee nitric nitrogen content of 
the country rock. Bull. Utah Agric. Exper. Sta. . Pp. 420-465. 1914. 
Free, E. E., Nitrate prospects in the Amarr valley, near Tecopa, Cal. 
Circular U.S. cats Agric., Bur. a no. 73. 19 
24 SHRE ., The of winter temperature in determining the distribution of 
plants. rp Jour, Bot. 1:193-202. 1914. 
