THE PHYSIOLOGICAL R(')LP] OF WATER IN PLANTS. 9 



Waringtou' lias shown tlie compariitivc value of aiinnoniacal nitrogen 

 and nitric nitrogen on dry soils, moist soils, light sandy soils, and inarl 

 soils. A dry soil is inliuenccd to a soniewliat greater degree by the 

 nitrates than by ammonia salts, Mdiile the converse apidies to moist 

 soils. Warington's resnlts Avere as follows: 



Action of II Ural (' uf xoda and aiiiinniiia salts in drif and wet seasons. 



It is nnnecessary to multii)ly researches on this point. It is evident 

 that as regards fertilizers there is an opportunity for selection with 

 reference to special conditions which will greatly increase the profit 

 from their use. 



The results of fertilizer experiments must not be accepted as infal- 

 lible. Duclaux - has said that "the meteorology of a region influences 

 the vegetation more than the geology," and we believe that under 

 different climatic infiueuces fertilizers will give different results. 



The life of a plant is in effect the resultant of a number of physical 

 conditions acting in conjunction. For example, the action of water will 

 not be the same during a hot and a cold season nor in a moderately 

 cold temperature and a tropical region. The exact knowledge of the 

 influence of water on the phenomena of vegetation, therefore, requires 

 a comj^arative study of this influence as affected by such factors as 

 temperature, light, fertility of soil, etc. 



The fertilizing substances are partially absorbed and retained by the 

 soil and partially dissolved. It is known that drainage water carries 

 off' only a small portion of i)otash, the (juantity thus removed being- 

 least in well-manured soil. The potash is retained not only by the 

 humus but also by the clay colloids. With an excess of water in the 

 soil the solvent action is largely increased, as shown by the experiments 

 of Gasparin and of Berthelot and Andre. While the soil, therefore, may 

 contain large quantities of soluble potash it is retained with such 

 energy that enormous quantities of water are necessary to dissohe ir. 

 The solubility of the potash is greatly increased if some sulphate such 

 as gypsum is added to the soil. 



Way^ has shown that the quantity of ammonia absorbed by a soil is 

 nearly coustaut when the solutions present have the same concentration. 



1 Aun. Agron., Vr> (1889), p. 213. 



2 Relation entre la iiK^trorologic et la geographic, Ami. CJcog., 1894. 



3 Jour. Roy. Soc. Ayr. Euglaud, 1850, p. 313. 



