CHAPTER XXIX 



MOVEMENT 



All things work and move. 

 — J. S. Dwight. 



All plants possess to a certain degree the power of motion, and 

 Ihe following classification of the various movements exhibited 

 by plants is as complete as our present knowledge permits. Each 

 type of movement will be discussed briefly in turn. 



I. Active or spontaneous movements. 



a. Internal 



1. circulation 



2. rotation 



3. streaming 



4. orientation 



b. External 



1. change of position 



A. through growth 



B. through independent locomotion (taxies) 



a. amoeboid movements 



b. ciliary movements 



c. excretory movements 



2. no change of position — curvature 



A. due to imbibition 



B. due to turgor changes 



a. autonomic 



1. nutations 



2. nastic movements 



b. paratonic 



1. nastic movements 



2. shock movements 



C. due to permanent growth 



a. autonomic 



1. nutations 



2. nastic movements 



b. paratonic — tropisms 



II. Passive movements — caused by wind, blows, etc. 



Internal Movements. — The internal movements of the cells 

 are visible only with the microscope, but are more or less char- 

 acteristic of all living cells. Cytoplasmic motion, which is an at- 

 tribute of all active cells, is manifested either by isolated stream- 

 ing movements, which may be reversed, now going in this direction 

 and now in that, or by a single stream, whose direction is constant. 

 These two forms of movements are known as circulation and ro- 

 tation respectively. In circulation the motion is observed not 



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