34 
Lepidium and Linum did not germinate at 0° €., but did germinate 
at 18°C. 
Collomia did not germinate at 3° C., but did germinate at 5.3° C. 
Nigella, [beris, and Trifolium repens did not germinate at 5.3° C., 
but did germinate at 5.7° C. 
Mays did not germinate at 5.7° C., but did germinate at 9° C. 
Sesamum did not germinate at 9° C., but did germinate at 13° C. 
Melon did not germinate at 13° C., but did germinate at 17° C. 
Malvacew, Gossypium herbaceum, variety not specified: Some cot- 
ton seeds on which experiments had been made two years before 
would not then germinate, but did germinate at this time at 40° C. 
Raphanus sativus (vadish): Lefebure had shown that these seeds 
germinate at 5° or 6° C. as their minimum temperature. 
Triticum (winter wheat), Hordeum (barley), Secale cereale (rye) : 
All of these Gramineze germinated at 7° C., according to Edwards 
and Colin, but this is probably not their minimum, for certainly 
barley will germinate at a lower temperature by prolonging the 
experiments. __ 
We conclude, therefore, that each species has a minimum tempera- 
ture at which it germinates, and the ordinary experience of the farmer 
would. suggest this, but in his work one can hardly decide whether 
seeds sown too early in the springtime are simply retarded by specific 
low temperatures or whether germination is quite impossible. These 
present experiments show that if the temperature is too low, then 
germination is prevented. In calculations on the relation of temper- 
ature to vegetation one must consider only facts deduced from pro- 
longed, constant temperatures. In the study of growth under natural 
conditions one must consider certain temperatures as useless and 
ineffective as concerns the germination of certain species of plants. 
There are, moreover, other facts that show that the same rule holds 
good for leafing, flowering, and maturing. 
According to De Candolle’s experiments, the species that require 
high temperatures as minima for germination are all from warm 
countries. Such species can not flourish in cold countries, for if they 
do germinate there this happens too late in the springtime and they 
can not ripen their fruits before winter. Among the species which 
germinate at low temperatures there are some that can exist in tem- 
perate climates, but these do not extend very far toward polar regions, 
either for reasons foreign to the germination or else because, having 
germinated too early, the delicate shoots are killed by frost. 
(3) There is for each seed a maximum temperature beyond which 
germination is impossible. The above experiments determine such 
maxima approximately as follows: 
Nigella does not germinate if the mean temperature exceeds 28° C. 
Collomia does not germinate if the mean temperature exceeds 28° C. 
