16 GROWTH OF WHEAT SEEDLINGS. 



Plants were withdrawn from these pans and arranged as in figure & 

 to show the effect of the potassium nitrate. This salt gave an alka- 

 line reaction to the solution and produced excellent plants. The 

 " fishhooks " on the roots of the potassium sulphate plants are seen 

 in this plate also (No. 4). 



The experiment with aluminum hydrate was repeated with ferric 

 hydrate. This was prepared from ferric chlorid by precipitation 

 with ammonium hydrate and was also washed free from all im- 

 purities in order to insure freedom from chlorin and ammonium. 

 A blank culture solution prepared with the ferric hydrate contained 

 less than 0.5 part per million of ammonium. The 5-day-old plants 

 are shown in Plate VII, and when compared with the preceding 

 plates show that the same general characteristics prevail whether 

 calcium carbonate, aluminum hydrate, or ferric hydrate is used to 

 keep down the acidity. 



EXPERIMENTS USING CLOVER AND TIMOTHY WITH WHEAT. 



Another experiment was made with clover and timothy, using cal- 

 cium carbonate to neutralize the acidity. The small seeds were 

 sprinkled upon pieces of bolting cloth of a large mesh, placed on 

 'the aluminum disks, and grown with some wheat seedlings. It was 

 found impossible to obtain satisfactory photographs of the timothy 

 plants, but both the timothy and the clover behaved in the same way 

 as did the wheat plants, and were even more sensitive to the acids. 

 A few of the clover plants are shown in Plate VIII, figure b. 



Both with the wheat and the clover cultures the effect of potassium 

 chlorid was not so harmful as that of potassium sulphate. In nearly 

 every case a much better root development was obtained in the 

 potassium chlorid solutions. 



While it is a well-known fact that the presence of certain solids by 

 their absorptive action stimulate the growth of seedlings in water 

 culture, the objection to the presence of a solid (calcium carbonate, 

 ferric hydrate, or aluminum hydrate) in one-half of the cultures 

 is overcome by the fact that another solid, carbon black, existed in 

 all alike, and that this solid has as great an absorptive power as 

 either of the others. 



It is also clearly evident that a salt, potassium sulphate for ex- 

 ample, is not taken into the plant as such, that is, as the molecule 

 (K 2 SO 4 ), but rather as an ion (K). When the potassium sulphate 

 (K 2 SO 4 ) is applied to the soil. as a fertilizer it goes into solution 

 and dissociates that is, splits apart into two radicals, K and SO 4 . 

 The potassium is taken up as the ion, while for the time being the 

 SO 4 radical remains in solution and combines with the water to form 



