214 BOTANICAL GAZETTE [MARCH 
that the Van’t Hoff law applies approximately up to 30° C., then 
the growth rate acceleration decreases to a point which he pro- 
poses to call the ‘‘stopping point,” a point below the lethal tem- 
perature. 4 
Kanitz has written a monograph on the effect of temperature 
of life processes in which he cites over three hundred pieces of 
literature distributed among several fields. The following is based 
on DENNY’s review of this monograph. He derives formulae from 
those of BERTHELOT, ARRHENIUS, VON Essen, and VANn’r Horr, by 
means of which the value of Q,., the coefficient for 10° C. rise in 
temperature, can be calculated from pecans “Oe data at any 
two temperatures. These formulae are Q,,= k, ie and Q,.= 
] xk. --] k, . . 
wis 08 oe a in which k,=rate of process at tempera- 
ture t,, and k,=rate of process at temperature t,. He found that 
when he calculated results at short temperature intervals instead of 
long ones, Q,,. is often not a constant at all intervals, but falls at 
high temperatures. He also states that many processes in plants 
and animals exhibit a temperature coefficient the same as the Van’t 
Hoff one within certain temperature limits, and cites in this con- 
nection such plant processes as CO, assimilation between o° and 
37° C. (MaTTHAEI); respiration of seedlings between o° and 35° C. 
(KuIjPER); water intake of barley grains between 3.8° and 34.6° C. 
(Brown and Wortey); permeability of plant cells and tissues 
between 0° and 30° C. (RYSSELBERGHE); etc. Some of these pro- 
cesses show higher values of Q,, at lower temperatures, or tem- 
peratures near the minimum of the process. 
BEAL (2) has found that seeds of Amaranthus retroflexus are 
long lived; that they are still viable after burial in the ground for 
thirty years. Delays in germination of seeds are due (putting aside 
the stimulus idea held by some workers) either to embryo characters 
such as immaturity of embryo, or need of fundamental chemical 
changes in the embryo preceding germination in a seemingly 
otherwise mature embryo (5), or to coat effects acting jointly with 
embryo characters. The embryo in the latter case is not dormant 
when naked and exposed to ordinary germinative conditions. 
