6 abstracts: plant physiology 



point of the liquid. Consequently, the Daubree experiment gives no 

 ground for supposing that capillary forces would be effective in causing 

 water to penetrate into deep seated and highly heated rock-masses. 

 This conclusion has l.een pointed out before ; the purpose of the present 

 paper is to enforce it, since the opposite, and erroneous, conclusion still 

 frequently appears as an argument in favor of the likelihood of the in- 

 troduction of water by means of capillarity into molten magmas. Even 

 if we make the' somewhat unlikely assumption of free liquid surfaces 

 far dowTi in the rocks, any pressure producible by capillarity is in general 

 likely to be small in comparison with the pressure due to the hydrostatic 

 column, except in pores of such fineness that the amount of water that 

 could flow thru them is infinitesimal. J. J. and L. H. A. 



PLANT PHYSIOLOGY. — The water requireme^its of j)lants. I. Inves- 

 tigations in the Great Plains in 1910 and 1911. L. J. Briggs and 

 H. L. Shantz. Bureau of Plant Industry, Bulletin 284, 1913. 

 This paper deals with the amount of water absorbed by plants in the 

 production of a unit weight of dry matter. In order to determine this 

 ratio, which is called the "water requirement," plants were grown to 

 maturity in large pots having a capacity of about 115 kilos of soil, pro- 

 vided with tight covers, with openings for the plants, the space between 

 the cover and the stem of the plant being sealed with wax. Thirty-one 

 varieties were tested at Akron, Colorado, in 1911, six pots being used in 

 each determination, and the results expressed with their probable error. 

 Of the crops tested, those most efficient in the use of water were mil- 

 let, sorghum and corn, the ratio being 275, 306 and362 respectively, that 

 is, these crops used 275, 306 and 362 pounds of water in the production 

 of one pound of dry matter. The least efficient were the legumes^ 

 alfalfa, Canada Pea and sweet clover, with ratios of 1069, 800 and 709.. 

 respectively, while the water requirement of the small grains was inter- 

 mediate, being 507 for wheat, 539 for barley, 614 for oats, and 724 

 for rye. 



Different varieties of the same crop showed measurable differences in 

 their water requirements. Determinations made under field conditions 

 agreed very well with the pot determinations. A comparison of the re- 

 sults with wheat and sorghum grown at Akron, Colorado, and Amarillo 

 and Dalhart, Texas, showed that while evaporation in Texas was 18 

 per cent higher than in Colorado, sorghum had the same water require- 

 ment, while wheat required 36 per cent more water in Texas than in 

 Colorado. L. J. B. and H. L. S. 



