DEDUCTION, GENERAL INSTANCES. 175 



continually circumnutating, though often on a 

 small scale. Even the stems of seedlings be- 

 fore they have broken through the ground, as 

 well as the buried radicles, circumnutate as far 

 as the pressure of the surrounding earth permits. 

 In this universally present movement we have 

 the basis or groundwork for the acquirement, 

 according to the requirements of the plant, of 

 the most diversified movements. Thus the great 

 sweeps made by the stems of twining plants and 

 by the tendrils of other climbers result from a 

 mere increase in the amplitude of the ordinary 

 movements of circumnutation. The position 

 which young leaves and other organs ultimately 

 assume is acquired by the circumnutating move- 

 ment being increased in some one direction. 

 The leaves of various plants are said to sleep 

 at night, and it will be' seen that their blades 

 then assume a vertical position through modified 

 circumnutation, in order to protect their upper 

 surfaces from being chilled through radiation. 

 The movements of various organs to the light, 

 which are so general throughout the vegetable 

 kingdom, and occasionally from the light, or 

 transversely with respect to it, are all modified 

 forms of circumnutation; as, again, are the 

 equally prevalent movements of stems, etc. 

 towards the zenith, and of roots towards the 



