THE NUTRITION OF THE ROOT 73 



tained in the interstices of the soil contains a greater or less 

 amount of nutritive substances which it has dissolved on its 

 way to the roots, and constitutes therefore the nutritive solu- 

 tion. According to the amounts present in the soil, the solu- 

 tion will contain more of one substance and less of another, and 

 Avill therefore be concentrated in various degrees. Now, every 

 root needs for the proper development of the upper portions of 

 the plant a definite saturation of the nutritive liquid of the 

 soil. The plant will not die if this advantageous degree of 

 concentration is not reached, but it will not flourish so well as 

 it might do with a greater concentration of the nutritive fluid, 

 other things being equal. 



If the fault lies in the fact that the solutions are too dilute, 

 the plant knows how to remedy the defect. The roots absorb 

 great quantities of the solution, and the plant gives off the 

 superfluous water through its leaves by an increased transpira- 

 tion, retaining the dissolved substances. The general appear- 

 ance of the plant betrays to some extent the method of its 

 nutrition, as large pale leaves are formed. No sickening of 

 the plant, however, is noticeable. The case becomes more 

 serious if the concentration of the water contained in the pot 

 becomes too strong, owing to a too rapidly repeated application 

 of manures. The growth of the upper portions of the plant 

 is then visibly retarded, the internodes are shortened, and the 

 leaves become puckered owing to the shortening of the midrib 

 and lateral veins, or are bent in various directions, spotted, and 

 fall oS" at an early period. The roots themselves are short, 

 thick, and bent up, and the newly-formed root-hairs are irre- 

 gular and shortened, soon become brown and discoloured, and 

 die away. As I know well from the many plants which have 

 been sent me by gardeners, these appearances are usually put 

 down to other causes, as gardeners are hard to convince that 

 plants may be easily overfed. This overfeeding of plants is 

 g-reatly on the inerease at present, and we shall prevent many 

 losses by being more moderate in the manuring of pot-plants. 



We must not forget that the kind of soil and manure which 

 is sufficient, and perhaps the best, for a certain species of plant 

 may be much too strong for another one, and cause it to sicken. 

 Ericaceae, Myrtace^, and many Leguminosa3 require a com- 



