32 



(m) TE]MPERATURES from -iO^ TO 41° c. 



Two Sesamum seeds germinated in 10^ hours under 40.7°, and the 

 others immediately after; 3 Melon seeds germinated in 04 hours 

 under 40.6° ; none of the other seeds germinated at all in 4 days. 



(n) higher temperatures. 



MM. Lefebure (1800) and Edwards and Colin (1834) have shown 

 that most seeds undergo an alteration at a temperature of 50° C, so 

 that they will not germinate after that, even Avhen put under most 

 favorable conditions. Some seeds when kept dry can be warmed in a 

 stove almost to the point of combustion, but in water they lose the 

 power of germination at 55° or 50°, or perhaps lower. In humid 

 soil the seed is altered in proportion to the abundance of the water 

 and the temperature of the soil. Thus, in De Candolle's above-given 

 experiments, the seeds being kept quite wet could lose the power of 

 germinating under 50° and perhaps under 34°, as some of the pre- 

 ceding experiments show, without, hoAvever, precisely defining this 

 limit. Therefore De Candolle only experimented on the seeds of 

 Sesamum at high temperatures with the following results: The 

 temperature varied from 50° to 57° C. The seeds were watered 

 copiously. One seed in 5 germinated in 25.7 hours at an average 

 temperature of 51.5° C. On repeating the experiment, 3 seeds in 12 

 germinated at the end of 6 days, and 2 subsequently, but the majority 

 did not germinate, the temperature having averaged 44° C. during 

 the first 26 hours and 20° C. during the remainder. 



For ease of study I have collected most of De Candolle's results for 

 each of the eleven plants, respectively, into the following small tables : 



Tables showing results of De Candolle" s experimenis on the genu iiiat ion of seeds 

 at different temperatures. 



lepidium sativum. 



SINAPIS ALBA. 



