342 BOTANICAL GAZETTE [DECEMBER 
blotters, regardless of the highest temperature reached in the 
different alternations. 
Pansy seeds germinated more completely at 17.5° than at 
15°C.; larkspur and poppy more completely at 15° than at 
17.5°; while with nasturtium and snapdragon seeds there was no 
difference between these two temperatures. Although the lark- 
spur seeds tested in 1914 germinated even more completely in the 
icebox than at 15°C., the slowness of germination in the icebox 
makes the use of so low a temperature undesirable. Furthermore, 
the difference in total germination in favor of the icebox tempera- 
ture was only with one lot of seeds, the other two germinating 
practically the same as at 15°C. 
The rather poor samples of pansy and snapdragon seeds which 
were tested in 1912 germinated more completely with an alterna- 
tion of temperatures than with a constant temperature of 20°C. 
These samples were not tested with the cooler constant temperatures 
which proved most favorable in 1914. The decrease in the average 
percentage of germination with rise in temperature above the opti- 
mum was rapid in the case of larkspur, somewhat slower in the 
poppy, and slow and gradual in nasturtium, pansy, and snapdragon. 
The low optimum temperature for germination of larkspur and 
poppy is reflected in the recognized practice of sowing these seeds 
in the fall or véry early in the spring, when the ground is cold. 
It is significant, too, as showing the adaptation of the seed to the 
general physiology and life history of the plant, that poppies fail to 
make satisfactory growth if started after the advent of warm weather 
when the soil temperature is above the optimum for germination 
of poppy seeds. In the case of larkspur and poppy, there was a 
great deal of variation in the relation of temperature to complete- 
ness of germination between even the different lots of the same 
kind of seeds. These two species will be considered separately in 
the following pages. 
TEMPERATURE REQUIREMENTS FOR GERMINATION OF LARKSPUR 
SEED.—Fig. 1 shows graphically the contrast in response to differ- 
ent temperatures of two different lots of larkspur seeds, tested 
simultaneously in 1914. Each of the three lots tested in 1914 
germinated much more completely in the icebox than at 17.5° C. 
Fig. 2 shows the total percentages of germination of one lot of 
