50 



THE PLANT. 



Constituents 



Combustible. . 

 Incombustible. 



In looking at these figures we must remember that 

 Ahrens could only determine what the overground part 

 of the plant had received from the root, not, as Ander- 

 son in the case of the turnip, what the whole plant had 

 derived from the soil. The great disparity in the in- 

 crease of combustible and incombustible substances 

 evidently depends rather upon the unequal distribution 

 of the materials absorbed, than upon any disparity in 

 the quantity derived from the soil. The whole period 

 of developement comprised about 92 days, and we see 

 that for more than the first half (49 days) the plant re- 

 mains stationary at an apparently low stage of growth, 

 the foliage alone being developed, and that not fully. 

 In the next 12 days, from the 18th to the 30th June, 

 the plant gains double the weight of incombustible con- 

 stituents, and grows twice as high as in the 49 days 

 preceding ; and within this short time, the overground 

 parts absorb nearly the same quantity of incombustible 

 constituents as they had previously taken up. In fact, 

 the plant takes up 8J times the quantity of combustible 

 matter, and 3f times more of ash constituents on one 

 day of shooting, than upon one of the 49 previous days. 



We cannot suppose it at all likely that the external 

 conditions of nutrition, the supply of food by the atmos- 

 phere and from the ground, or the absorptive power of 



