HOW PLANTS OBTAIN WATER. 



2 9 



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 pla:ed in damp paper or cloth for germination, one lot of 

 the soaked seeds should be planted in good soil and kept under the same 

 temperature conditions, for control. When the 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 compari- 

 sons 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. 



57. 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 

 ht 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 

 cultures they should be wrapped with black 

 paper or cloth to exclude the light from the 

 liquid, otherwise numerous minute algae 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. 



58. 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- 



Fig. 42. 



Culture cylinder to show position of 

 corn seedling iHansen). 



