The direct effect of water upon the composition of plants has been observed by many students.  For instance, Mayer, working in Holland, found that, in a soil containing throughout the season 10 per cent of water, oats was produced containing 10.6 per cent of protein; in soil containing 30 per cent of water, the protein percentage was only 5.6 per cent, and in soil containing 70 per cent of water, it was only 5.2 per cent.  Carleton, in a study of analyses of the same varieties of wheat grown in humid and semi-arid districts of the United States, found that the percentage of protein in wheat from the semiarid area was 14.4 per cent as against 11.94 per cent in the wheat from the humid area.  The average protein content of the wheat of the United States is a little more than 12 per cent; Stewart and Greaves found an average of 16.76 per cent of protein in Utah dry-farm wheats of the common bread varieties and 17.14 per cent in the durum varieties.  The experiments conducted at Rothamsted, England, as given by Hall, confirm these results.  For example, during 1893, a very dry year, barley kernels contained 12.99 per cent of protein, while in 1894, a wet, though free-growing year, the barley contained only 9.81 per cent of protein.  Quotations might be multiplied confirming the principle that crops grown with little water contain much protein and little heat-and fat-producing substances.

Climate and composition

The general climate, especially as regards the length of the growing season and naturally including the water supply, has a strong effect upon the composition of plants.  Carleton observed that the same varieties of wheat grown at Nephi, Utah, contained 16.61 per cent protein; at Amarillo, Texas, 15.25 per cent; and at McPherson, Kansas, a humid station, 13.04 per cent.  This variation is undoubtedly due in part to the varying annual precipitation but, also, and in large part, to the varying general climatic conditions at the three stations.

An extremely interesting and important experiment, showing the effect of locality upon the composition of wheat kernels, is reported by LeClerc and Leavitt.  Wheat grown in 1905 in Kansas was planted in 1906 in Kansas, California, and Texas In 1907 samples of the seeds grown at these three points were planted side by side at each of the three states All the crops from the three localities were analyzed separately each year.

The results are striking and convincing.  The original seed grown in Kansas in 1905 contained 16.22 per cent of protein.  The 1906 crop grown from this seed in Kansas contained 19.13 per cent protein; in California, 10.38 percent; and in Texas, 12.18 percent.  In 1907 the crop harvested in Kansas from the 1906 seed from these widely separated places and of very different composition contained uniformly somewhat more than 22 per cent of protein; harvested in California, somewhat more than 11 per cent; and harvested in Texas, about 18 per cent.  In short,