Potassium to Growth in Plants. 
219 
solution F less potassium, and in solution F to which potassium was only 
added after three, six, nine, and twelve days. Four jars containing four 
plants each were used in every instance, the seedlings being placed in the 
jars when the combined length of root and hypocotyl was 2 cm. The 
experiment was begun on April 6 and was discontinued after twenty-two 
days. Growth measurements were taken periodically and the data obtained 
are shown in Table XXVIII. A study of the table shows that the rate of 
growth of the plants in the full nutritive solution was during the first three 
days somewhat greater than that of the plants growing in the absence of 
potassium, and continued very uniformly throughout the remaining eighteen 
days. After the third day the growth of the plants in the solution less 
potassium falls off, while that of the plants growing in the solution which 
received its potassium complement on the third day continues unimpaired, 
and at the close of the experiment is very nearly equal to that of the plants 
growing in the full nutritive solution. After six days the growth of the 
plants in the solution less potassium virtually ceases, but an immediate 
response is shown whenever potassium is added, even when the addition is 
delayed until the twelfth day. 
After nine days’ growth, the plants in the full nutritive solution had 
long stout hypocotyls, broad cotyledons, and two leaves unfolded ; the 
plants growing in the solution to which potassium was only added after 
three days were somewhat smaller in all their parts than the plants growing 
in the full nutritive solution ; the plants growing in the solution to which 
potassium was added on the sixth day were considerably smaller than the 
plants growing in the full nutritive solution, and the cotyledons showed 
slight marginal chlorosis which had in some cases a tendency to work 
inwards towards the veins ; in the case of the plants growing in the 
potassium-free solution, one-fourth showed marked intraveinal chlorosis 
with a tendency towards albinism and drying margins, while the remaining 
plants showed less-pronounced symptoms of disease. 
After fifteen days the plants growing in the full nutritive solution and 
in the solution to which potassium was added after three days were ‘much 
alike : two pairs of leaves had expanded and the flower buds were develop- 
ing. The plants growing in the solution to which potassium was supplied 
after six days were undersized ; they had two pairs of leaves unfolded, but 
only two out of sixteen plants possessed flower buds. The plants growing 
in the solution to which potassium was not added until the ninth day 
showed still greater loss of stature ; they had two pairs of leaves unfolded, 
but flower buds had not formed. The plants growing in the solution to 
which potassium was added after twelve days had made no response, and, 
like those growing in its entire absence, showed marked chlorosis and 
marginal drying of the leaves. After twenty-one days the plants growing 
in the full nutritive solution and in the solution to which potassium was 
