Winter Meeting. 287 



and some sulphate. The last two — iron and some sulphate — are 

 never added to the soil, unless this be incidental to secure some 

 other nutrient, for they are already present in sufficient quantity. 

 When the physiologist grows a bottle-fed plant in a water culture 

 in the laboratory, then these substances must be supplied. 



In recent years we have had to admit that it is t)ecoming 

 more and more important to give annual attention to iwo other 

 compounds — to lime and magnesia — or to the relation of lime to 

 magnesia. 



From the solutions of the soil there are obtained, therefore, 

 nutrient salts or substances containing seven elements, nitrogen 

 (nitrates), phosphorous (phosphate), potassium (potash com- 

 pounds), calcium (lime compounds), magnesium (magnesia com- 

 pounds), sulphur (sulphates), and iron. 



All these things are then necessary and all enter into the com- 

 position of every living cell. If any one of these fails, the plant 

 shows immediately an indication of lack of vigor, and must event- 

 ually die. If any one of these is not present in sufficient quan- 

 tity, the total amount of the orchard crop will be proportionately 

 reduced, or will fail entirely. If any one of the first four is pres- 

 ent only in relatively small quantity, and the others in an unusually 

 large quantity, an unfortunate condition prevails, which may re- 

 act upon orchard products. This will be considered in detail later. 



Some special functions of the nutrients — The absence of phos- 

 phoric acid in the orchard is felt in the general appearance of the 

 trees, most particularly, perhaps, in those which are bearing fruit, 

 or under conditions favorable for growth. You may notice the ab- 

 sence of phosphoric acid, as the consequent inability to produce 

 fruit, as quickly in the cultivated orchard as in the uncultivated 

 orchard. Special evidence of this lack of food is noticed particu- 

 larly in the leaves, which are then sure to have a sickly, yellow 

 color. Of course, a yellow color may be produced by fungous dis- 

 eases and other general causes also, but the lack of phosphoric 

 acid is the chief cause. Phosphorus is a great balance wheel 

 among nutients ; especially does it regulate the amount of nitrogen 

 which may be economically used. 



Potash has some very important special functions to perform 

 in the growth of plants besides that of being a direct and import- 

 ant food. It is with much force claimed that a tree grown upon 

 a soil rich in potash will suffer less from drouths, on account of 

 the greater ability of the potash-fed tree to take water from a soil 

 holding little water. That is a claim; it should be thoroughly 



