EFFECT OF TEMPERATURE ON GERMINATION OF 
AMARANTHUS RETROFLEXUS 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 291 
CLYTEE R. EVANS 
(WITH FOUR FIGURES) 
Introduction 
The literature having a direct bearing on the effect of temper- 
ature on germination may be divided into two groups: one deals 
with growth in relation to temperature, and the other with delay 
in germination of seeds in general and of Amaranthus retroflexus in 
particular. In the first group the articles by SmiTH (10), LEHEN- 
BAUER (7), Lerrcu (8), BALts (1), and Kanirz (6) on relation of 
growth to temperature are of interest. SmirH found that temper- 
ature, possibly internal temperature of the growing parts, may be a 
limiting factor to growth in Furchraea and Agave. LEHENBAUER, 
in his work on rate of growth of maize seedlings, found that the 
Van’t Hoff law applies only at medium temperatures; at 31° C. 
the initial rate is not maintained, there being a falling off with time. 
He further found that the coefficients for 10° C. rise in temperature 
are greater at lower ranges of temperature (6.56 at 12°-22° C.), and 
less (0.06 at 33°-43° C.) at higher ones. Hestates that the optimum 
changes with length of exposure, and that there are not two optima, 
as stated by KoEppen. Miss Lerrcu, in work with rate of growth 
of seedlings of Pisum sativum, found that the Van’t Hoff law applies 
only from 10° to 28° or 30° C.; that there is the same type of 
gradation in the coefficients relating rate of growth to temperature 
that LEHENBAUER found; and that above 29°C. the relation of 
growth to temperature can no longer be expressed as a curve, so 
that a different curve must be constructed to express the rate of 
growth in successive time intervals. She defined the optimum 
temperature as the highest one at which the time factor does not 
enter. Batts offers an explanation of the time factor, and says 
213] {Botanical Gazette, vol. 73 
