Chap. III.] DOWNWARD GROWTH OF THE ROOT. 
97 
vertical height; and in June, 1850, the plant 
itself was 7 ft. 8 in. high. In the autumn of 
1851 the roots were near the top of the third 
chimney-pot, having grown vertically upward 
about 7 ft. The plant itself was within an inch 
of 9 ft. In the spring of 1852, I raised the 
column of earth to 8 ft. 1 in., and in the summer 
the plant was 9 ft. 8 in. high. 
In other similar experiments the soft gem- 
mules, or stems, of garden beans and scarlet- 
runners forced themselves upward through about 
10^- in. of earth, came through the holes of the 
flower-pot, and grew towards the light till the 
runners required training. 
Hence it would appear that, while in the earth, 
the first gemmules have a straight upward 
tendency independent of light. If we attribute 
this straightness to turgescence, I do not see 
why the growth should be in a straight line up 
more than down , or in any other direction. But 
the gemmule seems beautifully endowed with an 
internal structure differing from that of every 
other part of the plant, by which, when buried 
too deeply, it takes the most direct line to the 
atmosphere in which it is formed to flourish: 
though it would puzzle our philosophy to say 
the agent by which this growth is directed, as 
H 
Upward growth 
of first gem- 
mule when de¬ 
prived of light. 
