SECT. 1. CONDITIONS* 



fied with the indications of our instruments, till 

 such time as other instruments shall he invented 

 capable of detecting their errors ; and with the pre- 

 vious conclusion, till such time as some positive fact 

 shall he opposed to the experiments from which it 

 is deduced. 



SUBSECTION in. 



Action of Heat. A third condition necessary 

 to germination is the access of heat. No seed has 

 ever been known to germinate at or below the 

 freezing point. Hence seeds do not germinate in 

 winter, even though lodged in their proper soil. 

 But the vital principle is not necessarily destroyed 

 in consequence of this exposure ; for the seed will 

 germinate still, on the return, of spring, when the 

 ground has been again thawed, and the temperature 

 raised to the proper degree. But this degree varies Different 

 considerably in different species of seeds, as is q^e d!f- 

 obvious from observing the times of their germi'- 

 nation, whether in the same or in different cli- 

 mates. For if seeds which naturally sow themselves, 

 germinate, in different climates, at the same period ; 

 or in the same climate, at different periods ; the 

 temperature necessary to their germination must of 

 consequence be different. Now these cases are 

 constantly occurring and presenting themselves to 

 our notice ; and have also been made the subject 

 of particular observation. Adanson found that 

 seeds which will germinate in the space of twelve 



