266 
AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
the deficient substances quite rapidly in order that they may be stored in 
the reproductive parts of the plant. A wider variation in the composition 
of the straw is, therefore, to be expected. The results, as set forth in 
table 7, show this to be true. The variations in composition due to varied 
nutritive conditions are similar to, though more marked than, those of 
the grain. The extremely high phosphorus content of the straw from the 
nitrogen-deficient solutions confirms the idea that the phosphorus meta- 
bolism is blocked by the deficiency of proteins, and that, therefore, phos- 
phorus in the inorganic form piles up to some extent in the grain, but more 
markedly in the straw. The phosphorus content of the straw produced 
in the phosphorus-deficient culture solutions is very low, the average for 
the three years being approximately lo percent of the amount present in 
the straw from the normal solutions. The variations in the composition, 
although more pronounced in the straw, yet in general are identical with 
those in the grain. 
Table 8. The Average Composition of Plants Grown in the Normal Solution and in Solutions 
with One Nutrient Element in Each Case Reduced to One Tenth the Normal Amount 
Solution, Deficient Element 
Given 
Percent CaO 
Percent P2O5 
Grain 
Straw 
Grain 
Straw 
Normal 
0.697 
3-II4 
1.206 
0.628 
Ca O.I 
0.097 
0.408 
1.364 
0.667 
Mg O.I 
0.729 
2.589 
1.092 
0.673 
K O.I 
0.734 
2.763 
1.084 
0.427 
P O.I 
0.366 
1.727 
0.552 
0.068 
N O.I 
0.451 
1.519 
1.336 
1.463 
In summation, comparing the composition of the plants from the modified 
solutions with the composition of those from the normal, a deficiency of 
phosphorus in the culture solution causes a very marked lowering of the 
phosphorus content of both grain and straw of the plants grown in these 
solutions. A deficiency of either calcium or nitrogen causes an increased 
intake of phosphorus especially in the straw. A deficiency of potassium 
causes a slight reduction in the amount of phosphorus accumulated in the 
grain and a more marked reduction of phosphorus in the straw. Magnesium 
deficiency in the culture solutions causes a slight decrease of phosphorus 
in the grain of plants grown in these solutions, and a small increase in the 
phosphorus content of the straw. The average composition of the plants 
for the three years is given in table 8, and in graphic form in figure i. 
The Relation of Climate to the Composition of the Oat Plant 
The experiments of Lawes and Gilbert (1884), Cserhati (1908), Grisdale 
(191 3), and Tretiakov (19 13) have shown very strikingly that the factors 
of climate and geographical location cause a wide variation in the composi- 
tion of plants. Lawes and Gilbert (1884) explain these variations by devia- 
