Introduction The literature having a direct bearing on the effect of temperature 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 retrofiexus in particular. In the first group the articles by SMITH (io), LEHENBAUER (7), LEITCH (8), BALLS (i), and KANITZ (6) on relation of growth to temperature are of interest. SMITH found that temperature, 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 3I0 C. the initial rate is not maintained, there being a falling off with time. He further found that the coefficients for ioo C. rise in temperature are greater at lower ranges of temperature (6.56 at I20-220 C.), and less (o.o6 at 33?-430 C.) at higher ones. He states that the optimum changes with length of exposure, and that there are not two optima, as stated by KOEPPEN. Miss LEITCH, in work with rate of growth of seedlings of Pisum sativum, found that the Van't Hoff law applies only from IO? to 28? or 300 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. BALLS offers an explanation of the time factor, and says