^54 AGRICULTURE. 



{c) Pot these plants in similar-sized small pots, re- 

 potting as the sand in each pot becomes filled with roots 

 Place them under similar conditions as regards light 

 air, temperature, and water. Label the pots i, 2, and 3. 



{d) Prepare stock solution No. i, containing the es- 

 sential elements of plant-food in approximately the 

 proper proportions, by thoroughly pulverizing and dis- 

 solving in 1,000 parts of water (say 1 ,000 r. c.) 15 parts 

 monocalcium phosphate, 20 parts potassium sulphate, 

 2 parts magnesium sulphate, 30 parts sodium nitrate, 

 and 2 parts sodium chloride — adding a few drops of some 

 soluble iron compound. 



Prepare stock solution No. 2 in every way like No. i, 

 except that you leave out the sodium nitrate. 



Prepare stock solution No. 3 similar to No. i, except 

 that you leave out the potassium sulphate. (The mineral 

 matter will not entirely dissolve, so these solutions 

 should be well shaken before using.) 



(e) When watering plant No. i, occasionally add a 

 definite amount of solution No. i. (The condition of the 

 plant must be the guide as to the time and amount of 

 this food-supply.) Begin with a small amount, and 

 gradually increase or diminish it. 



At the same time add to the water used in watering 

 plant No. 2 the same amount from stock solution No. 2, 

 and to that used in watering plant No. 3 add the same 

 amouni: of stock solution No. 3. 



(/) Measurements and observations should be taken 

 at stated times during several months upon the follow- 

 ing points: Number, size, and color of leaves of each of 

 these plants; higlit and mean circumference of their 

 stems; number and size of branches; time of flowering; 

 number and character of blossoms; and in the tomato, 

 the number, size, and quality of fruits. 



Experiment 27. — If for any reason the above experi- 

 oient is not practicable, substitute {a) ordinary soil (no' 



