Silicon, which with oxygen makes ordinary sand, is essential to the growth of plants and is everywhere found in abundance. Sulphur, united with oxygen and the metals to form sulphates, is generally abundant enough. The same may be said of chlorine, which, united with sodium or potassium, is always present in our prairie soils. Phosphorus, as it occurs in the phosphates, is one of the most essential ingredients of a fertile soil. Calcium and magnesium are found in combination as carbonates and sulphates, and, though essential, are usually abundant, especially where limestone rocks underlie the soil and outcrop in so many places. Potassium is found united with chlorine or sulphuric acid. It is one of the elements that is most liable to be exhausted from the soil by a succession of crops. Sodium exists almost everywhere. It is one of the elements of common salt, and, though much like potassium, cannot take the place of the latter in plant nurture. Iron is abundant and at the same time necessary in small quantities. The elements above mentioned, together with oxygen, are to be found in the ashes of plants. Besides, there are two elements that come largely from the atmosphere, namely carbon and hydrogen, which, united with oxygen, make up the bulk of the plant. Thus, wood is a substance containing carbon, hydrogen, and oxygen, with small quantities of nitrogen and mineral salts. The mineral salts represent about one per cent. of air-dried wood. Having considered in a general way the constituents of the plant, and having noticed the source of each of these constituents, it may be of interest to look at the composition of the soil as revealed by chemical analysis. "A" is the analysis of a soil from Finney county, as made in the laboratory of the Kansas State University, by the author. "B" is a soil from Wyandotte county, as reported in the report of the Kansas State Board of Agriculture for 1874. "C" is a prairie soil from Dakota, as reported by Prof. E. Richards, of the department of agriculture.