May, 1921] 
DICKSON — COMPOSITION OF OAT PLANT 
Tretiakov (1913), Headden (1916, a, b), and others have studied the relation 
of nutrition and dimate to the protein composition of plants. Wiley (1901) 
and Wilfarth and Wimmer (1903) have shown that fertilizers and climate 
cause a marked variation in the sugar content of the sugar beet. Seissl 
and Gross (1902) state that the starch content of the potato is changed quite 
markedly by the addition of fertilizers. Parrozzani (1908) and Jakouchkine 
(191 5) find considerable variation in the organically combined phosphorus 
of plants when different fertilizers are employed. Garner (191 4) and others 
have shown that the oil content of plants is modified by the addition of 
certain fertilizer elements to the soil. 
A review of this literature on the relation of plant environment to com- 
position brings out two very striking facts: first, that the plant as a whole 
responds quite markedly to environment by changes in its composition, 
and second, that for no two cases are these responses the same. Most of 
the work on the relation of fertilizers to plant composition has been done in 
the field where sufficient quantities of most of the elements have been present 
to supply the minimum needs of the plant; therefore, the changes in com- 
position, especially in that of the seed, have not been very marked. The 
conclusion has thus been drawn that the composition of the grain, the 
reproductive part, is very constant, while the response or change in plant 
constituents takes place in the leaves and stems of the plants. 
It has been the purpose of the experiments herein recorded to study the 
effect of limiting certain essential nutrient elements upon the composition 
of the grain and straw of well matured plants when other environmental 
factors were controlled as far as possible. 
The culture work from May to August, 1915, and May to August, 1916, 
was carried on under climatic conditions different from those that governed 
the latter part of the work, which differences may in some cases explain the 
differences between the data recorded for the two respective periods. A 
brief comparison of the meteorological data for the two periods has been 
included in the present paper. 
From September, 1916, until the conclusion of the experiments the 
work has been carried on in the laboratory of plant physiology at the 
University of Wisconsin. It is a pleasure to acknowledge my indebtedness 
to Professor J. B. Overton for his advice and assistance in supplying the 
apparatus necessary during the course of the investigation. Acknowl- 
edgment is also gladly given Professor W. E. Tottingham for his advice 
and assistance in the analytical work necessary during the progress of the 
experiments. 
MeTthods 
Cultural methods employed in growing the plants under varied nutritive 
conditions are given in detail in a previous paper (Dickson, 1918). In 
brief, the complete cultural series consisted of the "normal" solution — that 
