70 



The soil cmd the plcmt 



where sufficient water was given (Pot 3) the plants grew 

 very well and had thick stems and large leaves ; where 

 too much water was given (Pot 16) the plants were very 

 sickly and small. 



The weights were : — 



Fig. 33 shows two pots of wheat, one kept only 

 just sufficiently moist for growth, the other kept very 

 moist but not too wet. You can see what a diffisrence 

 there is ; in the drier pot the leaves are rather narrow 

 and the plants are small, in the moister pot the leaves 

 are wide and the plants big. But there was also another 

 difference that the photograph does not bring out very 

 well — the plants in the rather dry soil were, as you can 

 see, in full ear, ripe and yellow, while those in the very 

 moist soil were still green and growing. We see then 



(1) that on moist soils there is greater growth than 

 on dry soils, but the plants do not ripen so quickly; 



(2) in very wet soils mustard — and many other plants 

 also — will not grow. 



Water is not itself harmful. It is easy to grow 

 many plants in water containing the proper food, 

 but air must he blown through the water at frequent 

 intervals. In the water-logged soil of Pot 15 the 

 trouble arose not from too much water but from too 

 little air. Air is wanted because plants are living and 



