12 EXPERIMENT STATION RECORD. 



Another factor which is no less important is tlic capacity of soil for 

 water. For the same proportion of water soils of different natures, as 

 already explained, possess different coellicients of hygroscopicity, per- 

 meability, and liability to desiccation. 



The early experiments of Sachs' sliow that tobacco suffers when the 

 water content of clay soil is 8 per cent and of sand l.."> per cent. The 

 writer has rei)eated these experiments with many phints in order to 

 settle the following ([uestions : (1) Is the power of resistance to drought 

 of a given i)Iant the same in ditt'erent soils! This question must be 

 answered in the affirmative. (2) Is the water content of the soil at the 

 time when plants wilt the same for all stages of plant growth ? No; it 

 fluctuates in such a way as to i)roduce a curve. These two ques- 

 tions are interesting to agriculture from the point of view of rational 

 irrigation. 



The following plants become dry and sulfer from drought with the 

 given water contents of the soil : 



The writer would urge agricultural experiment stations to make 

 experiments analogous to these with different cultivated jjlants. Tlie 

 following plan is suggested: Establish a series of experiments on typ- 

 ical soils and on the mixed soils which are found at the stations. In 

 order to eliminate the influence of the subsoil, use pots about SO cm. in 

 diameter and about 80 cm. in depth. Large barrels cut in two serve 

 the purpose well. Bore o or 6 holes of about 4 cm. in diameter in the 

 bottoms for aeration, and place the tubs in holes in the ground upon 

 supports about 20 cm. in height, so that the edge of the tubs will be 

 about on a level with the surrounding soil. For each plant experi- 

 mented with 2 series of 10 pots each will be required. In the first pot 

 place clay soil, in the second lime, in the third humus, in the fourth 

 clay, in the fifth peat soil, in the sixth garden soil, and in the seventh, 

 eighth, ninth, and tenth mixed soils. The two series shouhl give the 

 same results. If they do not, a possible error is indicated. Many 

 experiments may be made during the year with difterent varieties of the 

 lu'incipal cereals. If it is desired to study 5 varieties of wheat, 100 pots 

 will be required. The plants should be studied from the two points 

 of view stated above. It is necessary to note the point at which wilt- 

 ing occurs during each stage of growth, taking samjAes of soil and 



• J. Sachs, Physiology of Plants, Trauslated hy II. Marshall Ward, 1887, j). 258. 



