Physiologie. 355 



Radishes grown in plots contained much larger quantities of 

 boron in the tops than in the roots. Analyses of entire plants of 

 wheat, corn, peas and oats grown on plots in the South showed 

 the absorption of boron in all cases, the peas absorbing the most. 

 All of the control plants contained at least a trace of boron. 



Samples of soil from some of the control plots showed the pre- 

 sence of acid-soluble boron, while several similar samples of soil 

 from certain boron-treated plots showed no acid-soluble boron. 

 Usually more soluble boron was found in the treated soil than in 

 the control soil. 



The yield of wheat from a plot heavily treated with borax was 

 90 per cent of the manured-control yield and greater than the yield 

 of the unmanured control. The wheat grains were sound and con- 

 tained but a trace of boron. 



The yield of tomatoes in pot tests was unaffected when borax 

 was added in amounts to produce 0,0018 per cent of boron in the 

 soil, but when the amouni was increased to 0,0030 per cent. a 

 reduced yield resulted. 



Numerous factors influence the absorption, distribution and 

 action of boron in plants. 



No more than 0,62 pound of borax or 0,75 pound of calcined 

 colemanite should be added to each 10 cubic feet of manure, and 

 when using to boron-treated manure in growing leguminous plants, 

 the manure should be mixed with untreated manure before being 

 applied to the soil. For other plants, boron-treated manure should 

 not be used at a higher rate than 15 tons per acre. 



M. J. Sirks (Wageningen). 



Harris, J. A. and W. Popenoe. Freezing-point lowering 

 of the leaf sap of the horticultural types of Persea 

 Americana. (Journ. agr. Research. Washington. VII. p. 261—268. 

 1916.) 



The writers summary runs as follows: 



The constants presented in this paper prove that in a tropica! 

 fruit of relatively recent introduction to North American horti- 

 culture, the avocado Persea aniericaiia Miller [P.grattssima Gaerin. f.), 

 one of the groups of varieties, the so-called West Indian type, 

 is characterized by tissue fluids which freeze at a distinctly higher 

 temperature than in the two other groups of varieties (Guate- 

 malan and Mexican). In the conventional terms of physical chemistry 

 adopted by physiologists, the expressed leaf sap of West Indian type 

 varieties is characterized by a slighter depression of the freezing 

 point or by a slighter freezing-point lowering than is that of the 

 two other groups of varieties. This differentiation seems to hold 

 with remarkable constancy notwithstanding the wide geographic 

 origin (West Indian, Bahaman, Central American, Mexican and 

 Hawaiian) of the seeds or budwood from which the tissues dealt 

 with originated. 



The type which is characterized by the slightest freezing-point 

 lowering of its extracted sap — that is, the type in which the 

 expressed sap freezes at the highest temperature — is the one 

 which has been shown by horticultural experience to be the least 

 capable of enduring cold. That capacity to withstand low tempera- 

 tures is not solely due to differences in the freezing point of the 

 sap is evident from the slightness of the differences in the cryos- 



