Consciousness in Plants. 327 
some influence from the tip. As with a horizontally extended 
radicle, whose tip has been cut off or destroyed, the part 
which should bend most remains motionless for many days 
or hours, even though exposed at right angles to the full 
influence of gravity, we cannot do otherwise than conclude 
that the tip alone is sensitive to this power, and transmits 
some stimulus to the neighboring parts, thereby causing 
them to bend. Direct evidence of such transmission has 
been obtained. When a radicle was left extended horizon- 
tally for an hour or an hour and a half, by which time the 
supposed influence will have travelled some distance from the ° 
tip, and the tip was then cut off, the radicle subsequently 
became bent, although it was placed in a perpendicular posi- 
tion. Terminal portions of several radicles thus treated con- 
tinued for some time to grow in the direction of their newly- 
acquired curvature, for being destitute of tips they were no 
longer acted upon by the power of gravity. New vegetative 
points, however, appeared, and being acted on by this influ- 
ence coursed themselves perpendicularly downward as was 
their custom. 
Investigation having shown that it is the tip of the radicle 
that is sensitive to geotropism in the members of such 
distinct families as the Leguminose, Malvacee, Cucurbitacee 
and Graminezw, which may be represented by the Clover, 
Mallow, Gourd and Rye, we may justly infer.that this char- 
acter is common to the roots of most _ seedling-plants, 
Whilst a root is penetrating the ground, the tip must take 
the incipient step, as it has to determine the direction of the 
entire root. When, however, it is deflected by any subter- 
ranean obstacle, it is essential that a considerable length of 
the root should be able to bend, particularly as the tip itself 
grows slowly and bends but little, so that the proper down- 
ward course should be recovered. Immaterial as it would 
seem whether the entire growing part should be so sensitive 
to geotropism as to effect this movement, or that it should 
be brought about by an influence transmitted exclusively 
