4 



is quite evenly distributed throughout the leaves, stem, and seed, and 

 generally occurs in the entire plant in the largest proportion of any of 

 the essential ash constituents. The function of potassium is apparently 

 to aid in the production and transportation of the carbohydrates. The 

 flavor and color of fruits is generally credited to potassium. In fact, this 

 element seems to supplement the action of nitrogen by filling out the 

 framework established by the latter. Potash with nitrogen is always an 

 important fertilizer with special crops where the object is to produce 

 sugar, starch — as with sugar beets and potatoes. It is also apparently 

 essential for the formation of protein, and, thus, indirectly, aids in the 

 formation of all organic matter. 



Phosphorus, in the form of phosphates, is found in all parts of the 

 plant, but tends to accumulate in the upper parts of the stem and leaves, 

 and particularly in the seed. Its function is apparently to aid in the pro- 

 duction and transportation of the protein. It also seems to aid the as- 

 similation of the other plant food elements. An insufficient supply of 

 phosphoric acid always results in a poorly developed plant, and particu- 

 larly in a poor yield of shrunken grain. Nitrogen forces leaf and stem 

 growth, and phosphoric acid hastens maturity. 



Calcium, or lime, is a constituent of the stem rather than the seed, 

 and seems to impart hardiness to the plant. It has been noticed that 

 soils containing an abundance of lime usually produce well nourished 

 crops that are capable of withstanding unfavorable climatic conditions, as 

 drouth and early frosts, better than are crops not so well supplied with 

 lime. The exact function of lime is not clearly understood, but it seems 

 to aid in the construction of the cell walls. According to some authori- 

 ties, its absence is felt in less time than either potassium or phosphorus. 

 It is claimed that a supply of lime is just as essential to the plant in order 

 that it may form cell walls from sugar and starch, as it is for the forma- 

 tion of bone in animals. It also has a verv decided influence on the me- 

 chanical condition of the soil, and is a liberator of plant food, particu- 

 larly potash, held in insoluble forms in the soil. 



There can be little doubt that a proper balance in the supply of these 

 four important plant nutrients has a very decided influence on the nature 

 of the plant produced. Each has its own particular work to do, and the 

 absence or deficiency of any one of them will cause the death or the in- 

 complete development of the plant. Moreover, they are absorbed during 

 th j early stages of growth; for a cereal crop contains at the time of full 

 bloom all the nitrogen and potash which is found in the mature plant ; 

 the assimilation of phosphoric acid continues somewhat later. It is thus 

 plain that crops require a good supply of these important constituents of 

 plant growth in a readily available form if they are to make a proper 

 development. 



DIFFERENCES IN FOOD REQUIREMENTS. 



Again, plants, like animals, differ very much in their requirements 

 and in their ability to secure that which they need. Cereal crops contain 



