212 Variations in Growth-Rates [410 
period. At the end of each week several different kinds of 
measurements of the plants were made, and the data thus 
obtained were studied to bring out the seasonal variations in 
growth-rates. Since the solutions were alike for all sets and 
the seedlings used were selected for likeness, it is fair to sup- 
pose that observed differences in growth-rates, between the 
different sets of cultures, must have been mainly due to fluc- 
tuations in the uncontrolled conditions of the surroundings, 
such as temperature, light and the evaporating power of the 
air. 
The experiments were carried out in one of the experiment 
greenhouses of the Laboratory of Plant Physiology. No 
artificial shade was applied to the greenhouse. Two sets of 
cultures were always carried out simultaneously, one under 
unmodified greenhouse conditions and the other in a cheese- 
cloth chamber in the greenhouse, but the data obtained from 
the chamber cultures will not be dealt with in the present 
paper. A continuously rotating table 76 cm. in diameter was 
used in each case, the jars standing near the margin of the 
table. 
Japanese buckwheat, Fagopyrum esculentum Moench., was 
employed, and Shive’s? three-salt nutrient solution, no. 
R 4C2 (total osmotic value 1.75 atmospheres), was used 
throughout the entire series. Aside from renewing the 
solution at the middle of the four-week period, water was 
always added at the end of the third week of growth, to bring 
the solution back to its original volume. When the transpi- 
ration rates were excessive a still further addition of water 
was made during the fourth week of growth, in order to pre- 
vent the root systems from becoming unduly exposed. The 
first experiment began Feb. 14, 1916. 
Of the plant characteristics measured at the end of each 
four-week period of growth, only stem height, total dry weight 
and total area of the leaves (one surface only) are here con- 
*Shive, John W., “A study of physiological balance in nutrient 
media.” Physiol. Res. 1: 327-397. 1915. 
