ABSORPTION NUTRIMENT. 



23 



should be plante*^ in good soil and kept under the same temperature condi- 

 tions, for control. When ^he plants have germinated one series should be 

 grown in distilled water, which possesses no plant food; another in the nutrient 

 solution, and still another in the nutrient solution to which has been added a 

 few drops of a solution of iron chloride or ferrous sulphate. There would 

 then be four series of cultures which should be carried out with the same kind 

 of seed in each series so that the comparisons can be made on the same species 

 under the different conditions. The series should be numbered and recorded 

 as follows : 



No. I, soil. 



No. 2, distilled water. 



No. 3, nutrient solution. 



No. 4, nutrient solution with a few drops of iron solution added. 



48. Small jars or wide-mouth bottles, or crockery jars, can be used for the 

 water cultures, and the cultures are set up as follows ; A cork which will just 

 fit in the mouth of the bottle, or which can be supported by pins, is perforated 

 so that there is room to insert the seedling, 

 with the root projecting below into the liquid. 

 The seed can be fastened in position by insert- 

 ing a pin through one side, if it is a large one, 

 or in the case of small seeds a cloth of a coarse 

 mesh can be tied over the mouth of the bottle 

 instead of using the cork. After properly set- 

 ting up the experiments the cultures should be 

 arranged in a suitable place, and observed from 

 time to time during several weeks. In order to 

 obtain more satisfactory results several dupli- 

 cate series should be set up to guard against the 

 error which might arise from variation in indi- 

 vidual plants and from accident. Where there 

 are several students in a class, a single series 

 set up by several will act as checks upon one 

 another. If glass jars are used for the liquid Fig. 28. 



cultures they should be wrapped with black Culture cylinder to show position of 



, , , , , ,. , „ , corn seedling (Hansen), 



paper or cloth to exclude the light irom the 



liquid, otherwise numerous minute algse are apt to grow and interfere with the 



experiment. Or the jars may be sunk in pots of earth to serve the same 



purpose. If crockery jars are used they will not need covering. 



49. For some time all the plants grow equally well, until the nutriment 

 stored in the seed is exhausted. The numbers i , 3 and 4, in soil and nutri- 

 ent solutions, should outstrip number 2, the plants in the distilled water. 

 No. 4 in the nutrient solution with iron, having a perfect food, compares favor- 

 ably with the plants in the soil. 



