AGRICUIvTURAL BOTANY, CHEMISTRY AND PHYSIOLOGY OF PLANTS IIOI 



benches, each 3x5 feet. The percentages of boric acid were calculated 

 on a water and ash-free basis. 



The general conclusions may be stated as follows : 



1. It apparently made little difference in the quantity of boron 

 absorbed by the plants tested whether boron was added to the soil as borax 

 or as calcined colemanite. The addition of lime with borax had no defin- 

 ite effect in preventing the absorption of boron. Wheat and oats absorbed 

 very little boron, while leguminous and succulent plants absorbed com- 

 paratively large amounts. 



2. Wheat, beets, cowpeas, and tomatoes grown in pots in the green- 

 houses contained boron principally in the tops of the plants, and, with the 

 exception of the beets, comparatively little or none in the roots. 



3. The fruit of the tomato plants contained only traces of boron, 

 while the fruit of the cowpea contained large quantities. Ivcttuce grown 

 in the greenhouse absorbed boron in proportion to the amounts present 

 in the soil. 



4. Potatoes grown in the open showed, when mature, a small amount 

 of boron in the tops and relatively large amounts in the roots and tubers. 



5. The leguminous plants, string beans, soybeans, and cowpeas, 

 which were very sensitive to boron, showed, when grown in plot tests, a 

 more equal distribution of the boron among the roots, tops, and fruit than 

 the other plants tested. 



6. 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 absorption of boron in 

 all cases, the peas absorbing the most. All of the control plants contained 

 at least a trace of boron. 



7. Samples of soil from some of the control plots showed the presence 

 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. 



8. The yield of wheat from a plot heavily treated with borax was 90 

 per cent, of the manured-control yield and was greater than the yield from 

 the unmanured control. The wheat grains were sound and contained but 

 a trace of boron. 



9. The yield of tomatoes in pot tests was unaffected when borax was 

 added in amounts giving 0.0018 per cent, of boron in the soil, but when 

 the amount was increased to 0.0030 per cent., a reduced yield resulted. 



10. Numerous factors influence the absorption, distribution and action 

 of boron in plants. 



11. Not more than 0.82 pound of borax or 0.75 pound of calcined 

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

 the boron-treated manure in growing leguminous plants, the manure should 

 be mixed with untreated manure before being appHed to the soil. For other 

 plants, boron-treated manure should not be used at a higher rate than 

 15 tons per acre. Fourteen references are quoted in the 1)ibliography (i). 



(1) Sec B. Jan. I'^i i , No. 38, and B. May, 1913, No. 483. (Ed.). 



