4:0 THE PLANT. 



of azotised or non-nitrogenous substances are found com- 

 bined in its organism. 



To enable a plant to attain its maximum of growth, 

 the soil must at all times yield, in an available form, 

 the whole quantity of each of its constituents ; and, on 

 the other hand, the cosmic conditions heat, moisture, 

 and sunlight must cooperate to transmute the absorbed 

 substances into the organs of the plant. If the sub- 

 stances that have passed from the soil into the plant 

 cannot be turned to account, from the want of this co- 

 operation, no fresh substances are absorbed; in un- 

 favourable weather, the plant does not grow. No more 

 does it grow, even though the outward conditions are 

 favourable, if the soil contains no proper nourishment. 



In the second half of the period of developement, the 

 roots of the turnip plant, having penetrated through the 

 arable surface deep into the subsoil, absorb more potash 

 than in the preceding stage. If we suppose that the 

 absorbing spongioles of the root reach a stratum of soil 

 poorer in potash than the upper layer, or not sufficiently 

 rich in that material to yield a daily supply commensu- 

 rate with the requirements of the plant, at first, indeed, 

 the plant may appear to grow luxuriantly; yet the 

 prospect of an abundant crop will be small, if the sup- 

 ply of the raw material is constantly decreasing, instead 

 of enlarging with the increased size of the organs. 



In the economy of the turnip, the root receives dur- 

 ing the last month of vegetation nearly one-half of all 

 the movable constituents of the leaves ; and this consti- 

 tutes, after the completion of its first year's period of 

 vegetation, a store of organisable matter for future use. 



During the spring of the following year the root 

 begins to shoot, putting forth a slight leafy top, and a 

 flower-stalk several feet high ; with the developement 

 and maturing of the seed, the plant dies. The chief 

 bulk of the food stored up in the root is applied, in the 

 second year or third period, in quite a different direc- 

 tion ; though, beyond the mere supply of water, the soil 

 seems to take no part in this new act of life. 



All monocarpous plants that is, all plants which 



