204 APPENDIX. [March, 



K. 



CHEMICAL PHENOMENA IN GERMINATION AND VEGETATION. 



" The conditions necessary to germination are three fold ; namely, 

 moisture, a certain temperature, and the presence of oxygen gas. The 

 necessity of moisture to this process, has been proved by extensive ob- 

 servation. It is well known that the concurrence of other conditions 

 cannot enable seeds to germinate, provided they are kept quite dry." 



A certain degree of warmth is not less essential than moisture. 

 Germination cannot take place at 32° ; and a strong heat such as that 

 of boiling water, prevents it altogether, by depriving the germ of the 

 vital principle. The most favorable temperature ranges from 60° to 

 80° ; the precise degree varying with the nature of the plant ; a cir- 

 cumstance that accounts for the difference in the season of the year at 

 which different seeds begin to germinate. 



That the presence of air is necessary to germination, was demon- 

 strated by several philosophers, such as Ray, Boyle, Maschenbroeck, 

 and Boerhaave, before the chemical nature of the atmosphere was dis- 

 covered ; and Scheele soon after the discovery of oxygen, proved that 

 beans do not germinate without exposure to that gas. Achard after- 

 wards demonstrated the same fact, with respect to seeds in general, 

 and his experiments have been fully confirmed by subsequent observ- 

 ers. It has been even shown by Humboldt, that a dilute solution of 

 chlorine, owing to the tendency of that gas to decompose water, and 

 set oxygen at liberty, promotes the germination of seeds. These cir- 

 cumstances account for the fact, that seeds when buried deep in the 

 earth, are unable to germinate. 



It is remarkable that the influence of light, which is so favorable to 

 all the subsequent stages of vegetation, is injurious to the process of 

 vegetation. Ingenhouz and Sennebier, have proved that a seed germi- 

 nates more rapidly in the shade, than in the day-light; and in diffused 

 day-light, quicker than when exposed to the direct solar rays. 



From the preceding remarks, it is apparent that when a seed is placed 

 an inch or two under the surface of the ground in the spring, and is 

 loosely covered with earth, it is in a state every way conducive to ger- 

 mination. The ground is warmed by absorbing the solar rays, and is 

 moistened by occasional showers ; the earth, at the same time, protects 

 the seed from the light, but by its porosity, gives free access to the air." 

 Turner's Chcmistnj, p. 562. 



