NATURE OF PLANTS 5 



stimulates the mustard plant in such a way that the stem grows 

 toward the light and the root away from it. So the living sub- 

 stance 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. 



