242 PJnjslologhal P re-determination 



an increase of 90 kilograms of grain, 300 kilograms of straw, and 280 

 kilograms of chaff per hectare in favour of the treated seed was obtained. 

 On dry soil with a low humus content, on the other hand, the plants 

 from the treated seeds gave a slightly smaller yield than the controls 

 to the following extent, 10 kilograms of grain, 4 kilograms of straw, and 

 20 kilograms of chaff per hectare. The seeds used in Schleh's experi- 

 ment were soaked for 48 hours in distilled water. 



The importance of the conditions under ivhich the soaking 

 treatment is carried out. 



Although the soaking treatment appears to be simple, the immediate 

 and subsequent effects of soaking seeds in water are complex, and diiJer 

 widely according to the conditions under which the soaking of the seed 

 is carried out. 



During the natural uptake of water preceding germination the whole 

 physiological system of the seed is set in motion. Enzymes are liberated, 

 no doubt, from pro-enzymes, and soluble food-materials increase, etc. 



When seeds are immersed in water for the purpose of swelling, the 

 conditions to which the plant is subjected are abnormal, as is shown by 

 the fact that germination is inhibited. Under these abnormal conditions 

 there is no doubt that many of the complex of processes usually accom- 

 panying the initiation of germination are modified. In addition, however, 

 it is definitely known that a considerable exosmosis of essential soluble 

 food-reserves occurs^, the supply of oxygen to the seed is decreased, 

 and carbon dioxide accumulates in the seed. 



It is obvious that both the leaching out of essential food- reserves, and 

 the conditions of oxygen supply and of carbon dioxide escape, must be 

 greatly influenced by such factors as time of soaking, temperature of 

 soaking, relative amount of water used, movement of the water, surface of 

 the water exposed to the air, size of the seed, and density of the seed-mass. 



How far the leaching out of food-material and the modification of 

 the rate of gaseous exchange under the abnormal conditions of soaking 

 are related to the beneficial alterations in subsequent development and 

 in yield observed has not been satisfactorily investigated. Wollny and 

 his contemporaries considered that the leaching out of essential food- 

 reserves was always detrimental and comparable to the partial removal 

 of the cotyledons or endosperm as described above, and endeavoured 



> See especially A. Zol)l (44). F. Haborlandt (IS), T. Yokoi (43) and C. Andir (1 ). Data 

 puhliKhod by Zcibl and Andiv sliow that the pliosjjhorus and potassium of the soed-contents 

 are very rapidly lost when seeds are soaked in pure water. 



