MANUAL OF GENERAL AGRICULTURE. 37 



The absence of any one will be readily shown in the 

 growth of the plant. As the seed contains a considerable 

 amount of plant food, no marked difference in growth may 

 be noted the first few days, even though one or more of 

 the necessary elements be absent. Where the necessity 

 of an element is to be determined it is omitted from the 

 water culture and replaced by some unnecessary com- 

 pound. 



For the cultures obtain 10 glass tumblers and make a 

 cover of paraffined paper for each by dipping ordinary 

 wrapping paper into a pan of melted paraffin. The paper 

 may be held in place by a string tied around the side of 

 the tumbler. Do not tie on the covers until directed. 



Thoroughly clean six vessels and make up the follow- 

 ing stock nutrient solutions : 



For calcium and nitrogen use calcium nitrate, 2 grams 

 in 500 c.c. distilled water. 



For potassium and nitrogen use potassium nitrate, % 

 gram in 500 c.c. distilled water. 



For magnesium and sulphur use magnesium sulphate, 

 1/2 gram in 500 c.c. distilled water. 



For potassium and phosphorous use potassium hydro- 

 gen phosphate, 1/2 gram in 500 c.c. distilled water. 



For potassium (in different form than above) use 

 potassium chlorid, *4 gram in 500 c.c. distilled water. 



For iron use ferric chlorid, two drops in 500 c.c. dis- 

 tilled water. 



Equal quantities of the above solutions taken will 

 give a full nutrient solution in proper proportions. 



Set up the following series of cultures: 



I. One culture in distilled water. 



II. One culture in tap water. 



III. One culture in full nutrient solution. (Use 40 c.c. 



each of the six solutions prepared.) 



IV. One culture in full nutrient solution minus nitrogen 



(1) For calcium nitrate substitute 40 cc. calcium 

 chlorid made by dissolving .4 gram in 100 cc. dis- 

 tilled water. 



