260 FOOT-NOTES TO EVOLUTION. 
duties the same structure had to perform in the life of 
the creature’s ancestors. 
A plant may be defined as a sessile animal. It is an 
organic colony of cells, with the power of motion in 
parts but not that of locomotion. The 
plant draws its nourishment from inor- 
ganic nature—from air and water. Its 
life is not conditioned on a search for food, nor on the 
movement of the body as a whole. 
The plant searches for food by a movement of the 
feeding parts alone. In the process of growth, as Dar- 
win has shown, the tips of the branches and roots are in 
constant motion. This movement is in a spiral squirm. 
The movement of the tendrils of the growing vine is 
only an exaggeration of the same action. The course 
of the squirming rootlet may be deflected from a regu- 
lar spiral by the presence of water. The moving branch- 
lets will turn toward the sun. The region of sensation 
in the plant and the point of growth are identical be- 
cause this is the only part that needs to move. The 
tender tip is the plant’s brain. If locomotion were in 
question the plant would need to be differently con- 
structed. It would demand the mechanism of the ani- 
mal. The nerve, brain, and muscle of the plant are all 
represented by the tender growing cells of the moving 
tips. The plant is touched by moisture or sunlight. It 
“thinks” of them, and in so doing the cells'that are 
touched and “think” are turned toward the source of 
the stimulus. The function of the brain, therefore, in 
some sense exists in the tree, but there is no need in 
the tree for a specialized sensorium. 
The many-celled animals from the lowest to the 
highest bear in their organization some relation to loco- 
motion. The animal feeds on living creatures, and these 
it must pursue if it is to thrive. It is not the sensitive 
Mind of 
the plant. 
