166 Plant Physiology 



Calcium nitrate, 4 grams in distilled water 1000 cc. 

 Potassium nitrate, 1 gram in distilled water 1000 ec. 

 Magnesium nitrate, 1 gram in distilled water 1000 cc. 

 Potassium dihydrogen phosphate, 1 gram in distilled water 1000 



cc. 

 Potassium chlorid, .5 gram in distilled water 1000 cc. 



Taking 50 cc. of each of the preceding, cultures of the full nu- 

 trient solution lacking iron are prepared, the iron being added in 

 every culture where desired by a few drops of a 2 per cent solu- 

 tion of the salt indicated. 



In omitting the several elements separately, substitutions are 

 made from solutions of other salts made up in the same propor- 

 tion, but taking cognizance, in each case, of the smaller quantity 

 desired, the following substitutions being recommended : 



Less calcium, use NaNO 3 . 



Less nitrogen, use CaCL and KC1, respectively. 



Less potassium, use NaNO 3 , NH 2 PO.i, and NaCl, respectively. 



Less phosphorus, use KC1. 



Less magnesium, use NaoSO^ 



Less sulfur, use MgCl 2 . 



Set up duplicate cultures with full nutrient solution, with so- 

 lutions lacking each element successively, with distilled water, 

 with tap water, with Crone's solution. Also make for comparison 

 cultures of the Pfeffer solution both five times the strength and 

 one fifth the strength of that above used. Also set up two ad- 

 ditional tumblers (employing the full nutrient solution) of peas 

 to be employed in the last experiment. 



If it is possible to include tests with several plants, Canada 

 field peas, oats or wheat, and buckwheat are important, for each 

 manifests special requirements in the early stages of growth de- 

 pending largely upon the composition of the seed. 



Use ten plants in each culture, keep in a fairly moist place (or 

 invert a tumbler over each culture) for a day or two, then trans- 

 fer to greenhouse, if possible. Replace, as needed, by pipette 



