AGRICULTURAL BOTAXY, CHEMISTRY AND PHYSIOLOGY OF PLANTS I429 



gen. In some cases the amounts precipitated vary widely, while in 

 others the agreement is close. In these series the nitrogen precipitated 

 by phosphotungstic acid averaged in the tops of both soybeans and 

 cowpeas about 12 per cent of the total nitrogen; in the roots 5.5 per cent ; 

 in the nodules of the soybeans i per cent and in the nodules of the cowpeas 

 17 per cent. 



(4) Other forms of soluble nitrogen than those precipitated by 

 phosphotungstic acid and sodium hydroxide occur. In these series they 

 constitute an average in the tops of both soybeans and cowpeas about 68 

 per cent of the soluble nitrogen ; in the roots "]"] per cent ; in the nodules 

 of the soybeans 89 per cent, and in the nodules of the cowpeas 53 per cent. 



(5) Fixation takes place at a very earlj^ period in the growth of the 

 seedling— sometimes within 14 days. It is rapid in some cases, especially 

 with cowpeas. 



(6) Plants grown under the conditions of these experiments contain 

 no ammonia, nitrites or nitrates, as measured by the most accurate che- 

 mical methods. 



1067 -The Effect of Heavy Dressings of Mineral Salts on the Development and Struc- 

 ture of Plants. — Warnebold, ir. ill LandunrtschaftUche Jahrbiichfr, Vol. 49, No. 2, 

 pp. 215-234. Berlin, March 25, 11)16. 



In order to investigate the harmful effects of mineral salts when ap- 

 plied in excessive quantities, plants were grown in pot cultures and as 

 soon as they were past the seedling stage, Wagner P. K. K. salt (contain- 

 ing 8.3 per cent of nitrogen, 26.8 per cent of potash and 17.5 per cent of 

 phosphoric acid) was added to the pots in successive dressings which were 

 continued even after injury to the plants had been observed. The plants 

 were then left in the pots another few weeks before being removed for ex- 

 amination—anatomical and morphological. The actual amount of salts 

 applied was not determined accurately as the object was merely to injure 

 the plants by over manuring. An ordinar}^ garden soil was used in all 

 cases but one i. e. HcUanthus annuus which was cultivated in silver sand 

 mixed with nutrient salts. Controls fed so that normal development could 

 ta.ke place were grown in all instance. . The plants selected for the^trials 

 were : Cucurhita Pepo, Helianthus annuus, Raphanus caiidatus, Atriplex 

 hortensis, Fagopyrmn esculentum, Phaseolus vtdgaris nanus, Borago offici- 

 nalis. Datura Stramonium, Tropaeolum majus, Rumex alpinus. 



The results showed that the critical or harmful dose of Wagner salt 

 varied with the species of plant. Their order of sensitiveness was as 

 follows : Atriplex, Cucurbita, Datura, Helianthus, Tropaeolum, Rumex, 

 Raphanus, Borago, Fagopyvum. Also the amount of injury done varied 

 with individuals and with the degree of huniidity in the air, though no 

 generalisations can yet be made with regard to the latter observation. 



Leaving aside leaf modifications it may be said in a general way that 

 large doses produced similar results in all the species employed. Normal 

 development was always checked, and the plants were all more or less 

 dwarfed. It should be pointed out, however, that with Cucurbita, Pha- 

 seolus and Datura growth was at first stimulated, especially leaf growth, 



