2 I 8 
Smith and Butler. — Relation of 
third day, wheat, it will be remembered, lost 62 per cent, of its weight, but 
corn is not deleteriously affected at all. In fact, the mean weight of a plant 
of corn grown in the absence of potassium for three days is about 7 per 
cent, greater than that of a plant grown ab initio in the presence of potas- 
sium. The difference in behaviour of corn and wheat is significant. To 
what is it due ? In the case of wheat the plants growing in the full 
nutritive solution used 1 grm. potassium for every 15*33 g rm - °f dr y matter 
formed, while those growing in the nutritive solution to which potassium was 
added after three days produced 15*65 grm. of dry matter for every gramme 
of potassium absorbed. The figures for corn are: Plants growing in the full 
nutritive solution produced 14-52 grm. of dry matter per gramme of potassium, 
and those growing in the solution to which potassium was added after three 
days formed 14*46 of grm. dry matter per gramme of potassium absorbed. 
The relation of potassium to dry matter formed is very similar in both wheat 
and corn, the only difference being that a delayed addition curtails growth 
in the former and not in the latter. We interpret this to mean that some 
substance necessary for growth and to the formation of which potassium is 
essential was present in larger quantity in the corn than in the wheat. 
Potassium is known to be present in relatively greater abundance in 
young organs. 1 Weevers 2 believed that potassium functions in the regula- 
tion of turgidity and in the synthesis and metabolism of proteids. Ltipke 3 
held the view that potassium does not exercise a limited and special 
function, but plays a role in metabolism more general in nature, and, like 
nitrogen, phosphorus, sulphur, &c., is essential to the growth of each 
individual cell. Loew 4 considered potassium essential in the synthesis of 
carbohydrates, fat, and proteins, its role in the reactions being that of a con- 
densing agent. He also noted a fact, not without importance, that in 
seeds there is a closer relation between potassium and protein than between 
potassium and starch. Basing his calculations on the analyses of Wolf 
(‘ Aschen-Analysen ’, vol. i), he found that the mean ratio of potassium to 
protein in the Gramineae was 1:17 and in the Leguminosae 1 : 23. 
With the above opinions the results we have obtained do not conflict, 
with the exception of the relation to carbohydrate synthesis, which it does 
not seem to us the data presented in this paper support. 
Experiment 4. Japanese buckwheat was used in this experiment, and 
the plants were grown in water culture, solution F being used as the 
nutritive medium. The plants were grown in the full nutritive solution, in 
1 Pfeffer, W. : Physiology of Plants, English trans., vol. i, p. 430, and literature there cited. 
2 Weevers, T, : Untersuchungen iiber die Lokalisation und Funktion des Kaliums in der Pflanze. 
Rec. Trav. Bot. Neerland., viii. 289-332, 1911. 
3 Liipke, R. : Ueber die Bedeutung des Kaliums in der Pflanze. Landw. Jahrb. xvii. 887-913, 
1888. 
4 Loew, O. : The Physiological Role of Mineral Nutrients. Div. Veg. Phys. and Path., U.S. 
Dept. Agr., Bull, xviii, p. 26 et seep, 1899. 
