176 



BOTANICAL GAZETTE 



[FEBRUARY 



They grew Fulcaster wheat for 18 days in 12 different molecular propor- 

 tions of the salt combination II. The nutrient solutions had a total osmotic 

 pressure of 1.75 atmospheres. Of the 12 volume molecular proportions tried 

 the following proved best: KNO3 0.0216, CaH2(P04)2 0.0026, MgS04 0.0150. 

 This finding must not be taken too seriously, however, for it is based on the 

 extremely slim experimental evidence of a single set of cultures with 6 seedlings 

 in each concentration ; also very different molecular proportions (KNO3 o , 0036, 

 CaH2(P04)2 0.0078, MgS04 0.0300) gave almost as good results as this opti- 

 mum and very much better results than the intermediate combinations. 



Using combination I (Shive's solution) with a total osmotic pressure of 

 1.75 atmospheres, Shive and Martin' have determined the optimum volume 

 molecular proportions for the development of buckwheat during its early period 

 of growth (24 days) and during its period of maturity. The following table 

 gives the results based on maximum production of dry weight: 



It is interesting to see Shive's solution far superior to Knop's and to 

 Tottingham's for growth of buckwheat. In former work by Shive the 

 maximum growth of wheat tops appeared in the following molecular propor- 

 tions: KH2PO4, 0.0180; Ca(N03)2, 0.0052; MgS04, 0.0150. The Ca(N03)2 

 needs for buckwheat rises greatly in the late growth period, while the KH2PO4 

 and MgS04 requirements both fall. 



Many of the excellent methods used in these 3-salt nutrient solution studies 

 were worked up by McCall. McCall and Richards'" summarize their 



"> Shive, J. W., and Martin, W. H., A comparison of the salt requirements for 

 young and for mature buckwheat plants in water cultures and sand cultures. Amer. 

 Jour. Bot. 5:186-191. 1918. 



'" McCall, A. G., and Richards, P. E., Mineral food rsquirements of the wheat 

 plant at different stages of its development. Jour. Amer. Soc Agron. 10:127-134. 1917. 



