8 TERMINATION OF THE SEED. CHAP. I. 



hours in an ordinary degree of heat, may be made 

 to germinate in the space of three hours by ex- 

 posing them to a greater degree of heat ; and that 

 seeds transported from the climate of Paris to that 

 of Senegal, have their periods of germination ac- 

 celerated from one to three days.* Upon the same 

 principle, seeds transported from a warmer to a 

 colder climate, have their period of germination 

 protracted till the temperature of the latter is 

 raised to that of the former. This is well exem- 

 plified in the case of our green-house and hot-house 

 plants, from which it is also obvious that the tem- 

 perature must not be raised beyond a certain degree, 

 otherwise the vital principle is totally destroyed. 



SUBSECTION IV. 



Access of Moisture. A fourth condition ne- 

 cessary to germination is the access of moisture. 

 Seeds will not germinate if they are kept perfectly 

 dry. Water, therefore, or some liquid equivalent 

 From rain to it, is essential to germination. Hence rain is 

 watering. 3 always acceptable to the farmer or gardener, imme* 

 diately after he has sown his seeds ; and if no rain 

 falls, recourse must be had, if possible, to artificial 

 watering. But the quantity of water applied is 

 not a matter of indifference. There may be too 

 little, or there may be too much. If there is too 

 little, the seed dies for want of moisture ; if there 



* Families des Plantes, vol. i. p. 84. 



4 



