June, i92o.] S03IE SOLUTION CULTURES OF WHEAT 77 



conditions). No attempt was made in our experiment to control 

 either the solution temperature or any of the aerial conditions ; these 

 were furnished by the greenhouse room in which the cultures stood 

 and they were approximately like those of any rather dry, artificially 

 heated greenhouse in which plants are being grown, in a climate 

 like that of the month of February in Baltimore. Some of the aerial 

 conditions of our culture plants are roughly described by the thermo- 

 metric and atmometric data that will be mentioned below. — The 

 present preliminary study is thus seen to deal with the relations 

 holding between (a) the growth of young wheat plants in solution 

 culture, and (b) the non-temperature conditions of the solution, when 

 the frequency of change of the solution and the solution temperature, 

 as well as all the influential aerial conditions, had the intensities and 

 fluctuations that characterized our greenhouse during the experiment 

 period. It is unfortunate that plant physiology has not yet advanced 

 far enough to make it possible to control a larger number of the 

 influential conditions, or at least to record their values in quantitative 

 terms. It is safe to say that the results obtained by us would have 

 been very markedly different, if the climatic conditions and the "oxygen 

 and carbon-dioxide conditions of our cultures had been sufficiently 

 different. Also, the results would surely have been different if we had 

 employed some other kind of plant. 



Tottingham, 1 * Shive, 2) and others have noted that when wheat 

 seedlings are grown for several weeks in nutrient solutions having 

 certain characteristics, the plants show recognizable symptoms of what 

 may be called physiological or nutritional diseases. Some ^-salt 

 solutions are well-balanced and support good growth, while others 

 (differing from the well-balanced ones in total concentration, salt pro- 

 portions, or perhaps only in kinds of salts used) show sickly plants, 

 and in some cases the symptoms of sickness are clear enough to be 

 described morphologically. Among the diseased conditions thus pro- 

 duced in young wheat plants grown in well-controlled aqueous solutions 

 is one called by Tottingham magnesium injury. Shive found that this 

 form of injury occurred after the first two or three weeks of growth in 

 3-salt solutions made from KH 2 P0 4 , Ca(N0 3 ) 2 and MgS0 4 , having total 

 concentrations corresponding to either 1.75 or 4.00 atmospheres of 

 osmotic pressure, and having MgS0 4 : Ca(N0 3 ) 2 -ratio values of 3.00 or 



1) Tottingham, Wm. E. A quantitative chemical and physiological study of 

 nutrient solutions for plant cultures. Physiological Researches 1 : 133-245. 1914. 



2) Shive, 1916; I.e. 



