NATURE OF PLANTS 5 



that the stem grows toward the light and the root away from it 

 So the living substance of the plant while forming one united 

 whole varies in its sensitiveness in various parts of the plant. In 

 this respect the various parts may be compared to the receiving 

 stations of a wireless telegraphy system. The receiving stations 

 may have instruments sensitive to certain intensities of electrical 

 currents and other currents do not affect them. So the various 

 organs of the plant are sensitive, each in its own peculiar way, 

 to certain stimuli. As a result of this adjustment the various 

 parts of the plant, being attuned or sensitive to certain forces, are 

 led or induced to grow so that they come into the most helpful 

 and beneficial relation to these forces. Thus the leaves, branches, 

 and roots are stimulated to grow and develop so that each part 

 becomes properly related to light, moisture, gravity, etc. The 

 broad blades of the majority of leaves are exposed to the direct 

 rays of light. This arrangement is of the greatest benefit be- 

 cause they are using the light in the manufacture of foods. This 

 position is assumed, however, because they are sensitive to light, 

 gravitation and other forces which direct and cause the arrange- 

 ment. This is the most noteworthy feature about the sensitive- 

 ness of the protoplasm. Forces stimulate to growth in such a 

 way that the results are helpful and the greatest good comes to 

 the plant. In other words the reactions are purposive. These 

 growths are so elaborate and beneficial that they often appear as 

 the result of reason and will. The bending of the root into the 

 soil brings it into contact with water and other foods ; the tendril 

 coils about a branch and binds the plant firmly to the support. 

 The plant, however, does not direct these adjustments. These 

 reactions do not involve consciousness. These movements and 

 all others are absolutely directed and controlled by the various 

 forces which act upon the sensitive protoplasm. A definite re- 

 action follows a stimulation which the plant has no power to 

 alter or control. The root will bend down into a dish of mercury 

 with the same energy and directness as that with which it pene- 

 trates the soil, and the tendril will clasp your finger or a branch 

 of its own body as firmly as a serviceable support. 



