SCIENCE IN THE PLANT WORLD 
climb up whatever support is handy, exhibit 
insensibility to light no matter from what angle 
it strikes. Stems, flower and leaves of all plants 
each give a different and scientific reaction 
to light in a way which looks much like direc- 
ting thought. 
Nothing is more scientific than the skill with 
which plants co-operate with gravity in con- 
structing their root systems. The roots are often 
trained to grow out horizontally and resist grav- 
ity for a certain distance. Then they grace- 
fully yield to its pulling power, and, curving 
their tips downward, grow straight toward the 
center of the earth. Any secondary roots which 
are sent out again start horizontally to repeat 
the above process on a smaller scale. All this 
makes for an efficient, well-balanced root- 
system. | 
A curious motion which is not thoroughly 
understood is a slight gyratory movement ob- 
servable in the tips of all living plants. It is 
possible that it is connected in some way with 
the earth’s rotation or is it merely a kind of 
groping, feeling gesture? In the case of roots, 
where the same gyrations occur, it undoubtedly 
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