CHAPTER III. 



ABSORPTION OF LIQUID NUTRIMENT. 



45. We are now ready tq inquire how plants obtain food 

 from the soil or water. Chemical analysis shows that certain 

 mineral substances are common constituents of plants. By 

 growing plants in different solutions of these various substances it 

 has been possible to determine what ones are necessary constitu- 

 ents of plant food. While the proportion of the mineral ele- 

 ments which enter into the composition of plant food may vary 

 considerably within certain limits, the concentration of the solu- 

 tions should not exceed certain limits. A very useful solution is 

 one recommended by Sachs, and is as follows : 



46. rormula for solution of nutrient materials : 



Water looo cc. 



Potassium nitrate O- 5 g^* 



Sodium chloride 0.5 " 



Calcium sulphate 0.5 " 



Magnesium sulphate o. 5 " 



Calcium phosphate 0.5 * ' 



The calciiun phosphate is only partly soluble. The solution which is not 

 in use should be kept in a dark cool place to prevent the growth of minute 

 algse. 



47. Several different plants are useful for experiments in water cultures, as 

 peas, corn, beans, buckwheat, etc. The seeds of these plants may be germi- 

 nated, after soaking them for several hours in warm water, by placing them 

 between the folds of wet paper on shallow trays, or in the folds of wet cloth. 

 The seeds should not be kept immersed in water after they have imbibed 

 enough to thoroughly soak and swell them. At the same time that the seeds 

 are placed in damp paper or cloth for germination, one lot of the soaked seeds 



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