322 
JAMES GEERE DICKSON 
solutions is nearly doubled, and for those grown in nitrogen-deficient 
solutions it is more than trebled. Figure 5 shows the general relation 
of the respective nutrient elements to the economic use of water by the 
oat plant. 
Summary 
1. The general development of the plants studied is most severely 
affected by a deficiency in phosphorus or hitrogen. 
2. A deficiency in phosphorus or nitrogen prevents the stooling of 
the plants. 
3. The general vigor of growth is increased by a deficiency in 
magnesium or calcium, and is greatly decreased by a deficiency in 
phosphorus or nitrogen. 
4. The period of development is shortened by a deficiency in 
potassium, phosphorus, or nitrogen, and is lengthened by a deficiency 
in magnesium or calcium. 
5. The total dry weight of the plants is greater than the normal 
when magnesium or calcium is deficient, and less than the normal 
when potassium, phosphorus, or nitrogen is deficient. 
6. Grain production is lowered by a deficiency in any one of the 
elements in question: magnesium, calcium, potassium, phosphorus, 
and nitrogen. 
7. The ratio of grain to straw is decreased by a deficiency in mag- 
nesium or calcium, and is increased by a deficiency in potassium, 
phosphorus, or nitrogen. 
8. The weight of the individual kernels is lowered by a deficiency 
in magnesium or calcium, and is raised by a deficiency in potassium, 
phosphorus, or nitrogen. 
9. The water requirement of the plants is decreased by a deficiency 
in magnesium, slightly increased by a deficiency in calcium, and 
greatly increased by a deficiency in potassium, phosphorus, or nitrogen. 
10. In general, the effects upon the plants of limiting the supply 
of phosphorus or nitrogen are much more noticeable than the effects 
of limiting the supply of magnesium, calcium, or potassium. 
Department of Botany, 
University of Wisconsin. 
