750 



MECHANICAL LAWS OF GROWTH. 



This table shews, if the ascertained temperatures are correct, that grains of wheat 

 cannot germinate below 5° G, or seeds of the gourd below i3°*7, &c., however long they 

 may lie in moist earth ; and that they no longer germinate, but quickly perish at temper- 

 atures above those named in the third column ; while at the temperatures named in the 

 second column germination takes place in a shorter time than at either higher or lower 

 temperatures. It may however be taken for granted, from the great difficulty of obtain- 

 ing these numbers, that the result of further observations will not be identical, though 

 probably approximate. It is clear that many series of experiments will be necessary 

 in order to determine each of the cardinal points. The following figures, obtained by 

 Koppen, agree moderately well with mine, as far as they relate to the same plants. 



The following results ', obtained by Alphonse de Gandolle, are moderately trustworthy 

 as far as relates to the inferior limit, but hardly so much so with respect to the superior 

 limit and the temperature of most rapid growth, as may be concluded by comparing 

 with those of other observers. 



I take the figures from the table of curves in De Candolle's treatise, with the assistance of the 



text. 



^ De Candolle remarks that the seeds of maize, melon, and Sesamum become brown, the first 

 as if burnt at 40° C, a phenomenon which has not been noticed by others. These ' burnt ' seeds 

 however germinated afterwards at a lower temperature. 



