354 Physiologie. 



tions than the phosphorus in other mineral phosphates. The super- 

 iority of these two phosphates over the others tested is shown 

 chiefly by the first crop. 



Chemical analysis showed that the plant-food Solutions applied 

 did not appreciably modify the results. 



The cereals produced as satisfactory yields as the legumes. 



The crop yields tended to increase as the application of rock 

 Phosphate increased up to a point where the size of the pots 

 seemed to be a limiting factor, apatite being the only exception. 



The plants obtained their calcium, as well as their phosphorus, 

 froni brown rock phosphates. No better results were secured when 

 calcium carbonate was applied than when rock phosphate alone 

 was used. 



There was no particular relation between the citric-acid-soluble 

 phosphorus and the availability of these phosphates for plants. 



Dextrose, when used as a fermentable substance, was harmful. 



The degree of fineness is a factor which determines to some 

 extent the availability of rock phospate, as indicated by the brown rock. 



These investigations extended over a period of SVg years, and 

 embrace results from 700 pot cultures and 400 phosphorus deter- 

 minations. M. J. Sirks (Wageningen). 



Cook, F. C, Boron, its absorption and distribution in 

 plants and its effect in growth. (Journ. agr. Research, Wa- 

 shington. V. p. 877—890. 1916.) 



The experiments reported in this paper were made in connec- 

 tion with a cooperative study of borax and calcined colemanite as 

 larvicides for the house fly. The object of this particular study was 

 to determine the effect of boron-treated horse manure on plant 

 growth and to study the absorption of boron and its distribution in 

 the roots, stems and fruit of plants grown on soil fertilized with 

 this manure and on soil fertilized with untreated manure. The 

 plants were grown in pots in greenhouses, Analyses of the soil 

 from several treated and untreated plots are included. 



It apparently made little difference in the quantity of boron 

 absorbed by the plants tested wether boron was added to the soil 

 as borax or as calcined colemanite. The addition of lime with 

 borax had no definite effect in preventing the absorption of boron. 

 Wheat and oats absorbed very little boron, while leguminous and 

 succulent plants absorbed comparatively large amounts. 



Wheat, beets, cowpeas, and tomatoes grown in pots in the 

 greenhouses, contained boron principally in the tops of the plants, 

 and, with the exception of the beets, comparatively little or none 

 in the roots. 



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

 while the fruit of the cowpea contained large quantities. Lettuce 

 grown in the greenhouse absorbed boron in proportion to the 

 amounts present in the soil. 



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. 



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. 



