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UPWARD GROWTH OF THE HEAD, AND [Part II. 
General growth 
of head towards 
light; general, 
growth of root 
to wherever it 
can find good 
soil. 
tween gravity and light is the origin of very 
beautiful growth in many trees. 
Were I to lay down a general rule about the 
direction of the growth of the greater part of 
plants, it would be, that the growth above is in 
whatever direction it can find light; and that 
the growth below is in whatever direction it can 
find the best soil. I except the growth of the 
first tap-root of the seedling, and of its first 
gemmule, as long as this is below the earth, and 
consequently not exposed to light. 
The fact shown us by Knight’s most beautiful 
experiment, much as it says, says no more in 
favour of gravity, or weight, as the director of 
the growth of plants, than the fact which we see 
every day, that plants are drawn by light, says 
in favour of light. 
‘‘Fools will rush in where angels fear to tread 
and we may have plenty of them to settle these 
questions for us nicely. But can the philo¬ 
sophic, or the unphilosophic, consider this first 
principle in physiology as settled, any more than 
any other first principle of it ? The whole is 
doubt and darkness. 
We are ignorant of how the sap is first im¬ 
bibed. We are ignorant of what causes it to 
