1918.] AGRICULTURAL BOTANY. 521 



shown that the addition of other allialine reacting substances, such as sodium 

 and potassium carbonates and calcium oxid, produced effects similar to mag- 

 nesium carbonate." 



It is concluded that the toxic effects that have frequently been noted in 

 studies with the use of magnesium carbonate have been occasioned by exces- 

 sive alkalinity. " In view of the fact that the naturally occurring carbonates 

 of magnesium produce widely different effects from the precipitated carbonate, 

 together with the evidence set forth above, it seems reasonable to conclude 

 that this material is unsuited for studies on the lime-magnesia ratio. With 

 its use, effects on the reaction of the soil may so affect physiological processes 

 as to obscure the effects that may be inherent within the ratio of calcium to 

 magnesium itself, and therefore the result obtained may lead to entirely 

 erroneous conclusions." 



Artificial fertilizers: Prewar and war cost, AV. C. Robertson {Jour. Dept. 

 Agr. Victoria, 15 {1911), No. 5, pp. 295-302, figs. 2).— This paper deals with 

 prices of fertilizers during the years 1907 to 1917, showing that the increases 

 in prices over the 10-year period in Australia have been for bone dust 15 per 

 cent, superphosphate 28, dried blood 38, sodium nitrate 36, and ammonium 

 sulphate 5G per cent. 



Analyses of commercial fertilizers, P. H. Wessels {Rhode Island Sta. Insp. 

 Bui., 1917, Oct., pp. 3-19). — This reports the analyses of commercial fertilizers 

 and fertilizer materials, including lime, plaster, and wood ashes, inspected 

 during 1917. A table of lime equivalents for neutralizing purposes is pre- 

 sented, and the amounts of water-soluble nitrogen and potash determined 

 as well as the usual determinations. The character of the water-insoluble 

 nitrogen has been studied, and the chemical work supplemented by tests of 

 the ability of the nitrogen to supply the needs of growing plants. 



Analyses of commercial fertilizers, R. N. Brackett et al. {South Carolina 

 Sta. Bui. 194 {1911), pp. 3-66).— This bulletin contains the results of actual 

 and guarantied analyses of 1,585 official samples of commercial fertilizers and 

 fertilizing materials offered for sale in South Carolina during the season of 

 1916-17. 



AGRICULTURAL BOTAITy. 



Ecolog'ical studies in the tension zone between prairie and woodland, J. E. 

 Weaver and A. E. Thiel {Univ. Nebr., Bot. Survey Nehr., n. ser., No. 1 {1911), 

 pp. 60, pis. 6, figs. 31). — Investigations near Minneapolis, Minn., and Lincoln, 

 Nebr., are said to show that prairie soils to a depth of 30 cm. (11.8 in.) fre- 

 quently lack available water during the growing season. This gives a clue to 

 the absence of trees on high prairies. While even a brief period of lack of 

 available water would prove disastrous to tree growth, exceptionally wet years 

 might be so favorable as to permit complete establishment and sufficient root 

 growth for the seedling to draw upon the moisture of the deeper soil. On the 

 other hand the prairie soil might be much drier physiologically than the graphs 

 indicate. The wiiole question of the root distribution of prairie plants as cor- 

 related with the seasonal march of soil water at different depths and extend- 

 ing to the lower limit of the soil occupied by the roots, together with the sea- 

 sonal activity of the plants, requires further investigation. 



The great amount of evaporation in the prairie, together with the low water 

 conterrt of the soil, is deemed sufficient cause for the xerophytic character of 

 the vegetation. It shows also the difliculties met by trees in establishing 

 themselves in grassland and may explain their absence .from the prairies. 

 55096°— 18 ^3 



