86 Elementary Plant Physiology. 



proper temperature. The solution in the bottle should be 

 renewed at least once a week. It will be found advan- 

 tageous to imbed the culture jar in soil, and it should be 

 shielded from the direct rays of the sun. Compare the growth 

 of the seedling in the above culture with one grown in soil in 

 a pot placed near it. The solution contains all the elements 

 which the plant is supposed to derive from the soil. 



84. Growth of plants in solutions lacking nitrates. 

 Make up the following solution : 



1.5 grams neutral potassium phosphate. 



1.5 grams magnesium phosphate. 



1.5 grams potassium chloride. 



600 cc. distilled water. 



Dilute as above with ten parts of water to fill culture jar, 

 and add a small bit of iron chloride. In this the plant is given 

 no nitrogen, that in the air not being accessible to it. 



Compare growth of seedlings of corn, sunflower, or wheat in 

 this solution with others grown in soil or in normal complete 

 culture solutions. Can the plant attain development without 

 nitrates? (See " Practical Text-book of Plant Physiology.") 



85. Growth with distilled water as a nutritive 

 fluid. Set up a water culture, using all the precautions given 

 above, but filling the jar with distilled water only. The seed 

 contains an amount of food sufficient for limited growth, and 

 the seedling depends upon this until its absorbent and chloro- 

 phyl-bearing organs are developed under normal conditions. 

 In this instance the stage will soon be reached where the sup- 

 ply will be exhausted and growth will cease. 



86. The food-forming power of green leaves 

 Germinate a number of seeds of corn, sunflower, or bean, and 

 grow three seedlings in each of two pots. Place one pot in a 

 position where it may receive sunlight, and the other in a 

 room from which light is wholly excluded. Note the differ- 

 ence in the appearance and form of the two seedlings from 



