176 



the peas is checked, and the air in proportion sur- 

 fers but little change. A jar containing some steep- 

 ed peas, supported on a hoop, was, as before, in- 

 verted over mercury ; but within it was previously 

 placed a small glass cup, rilled with powdered lime, 

 which floated on the mercury. The jar, during the 

 whole experiment, continued dry ; the peas sprout- 

 ed but little, and shrunk nearly to the same size as 

 when in their dry state ; and the lime greatly in- 

 creased in bulk. The residual air, when examined, 

 suffered no diminution by being shaken with lime 

 water ; but it still contained a large portion of oxy- 

 gen gas ; while the air of another jar, placed in si- 

 milar circumstances, except that it held no lime, 

 had in the same time lost the whole of its oxygenous 

 portion : the peas also were nearly double their ori- 

 ginal sizo, and their radicles 1.2 inch long. Hence, 

 therefore, it is clear, that whatever obstructs the 

 emission of moisture and carbon from the seed, or 

 too rapidly draws off the moisture, necessarily puts 

 a stop to those reciprocal changes between the seed 

 and the air, so essential to its future growth. 



139. That the carbon which issues from the seed 

 during its germination, is given out in union with 

 the moisture previously imbibed, will, perhaps, ap- 

 pear more evident from what we have next to offer 

 concerning the carbon furnished by plants during 

 their vegetation. It has been shewn (3O.), that the 

 presence of oxygen gas is essential to the growth of 

 plants, and that, by the upper surfaces of their 

 leaves (26.), it is converted into carbonic acid : it 

 has been also shewn (39.), that the carbon, which 

 effects this conversion, proceeds neither from the 



