Chap V MODIFIED CIECUMNUTATION. 263 



CHAPTER V. 



MoDiriED CiKCCMNUTATioN : Climbino Planvs ; Efinastio and 

 Hyponastio Movements. 



Ciicumnutat.ion modified through innate causes or through the action 

 of external conditions — Innate causes— Ciinibing plants; similarity 

 of tlieir movements with those of ordinary plants ; increased ampli- 

 tude ; Qpeasional points of difference — Epmastic growtli of young 

 leaves — Hyponastic growth of the hypoootyls and epicotjls of seed- 

 lings — Hooked tips of climbing and other plants due to modified 

 circumnutation — Arapelopsis tricuspidata — Smithia Pfundii — 

 Straightening of the tip due to hyponasty— -Epinastic growtli and 

 oireuinnulation of the flower-peduncles of Trifulium repens and 

 Oxnlis carnosa. 



The radicles, hypocotyls and epicotyls of seedling 

 plants, even before they emerge from the ground, and 

 afterwards the cotyledons, are all continually circum- 

 nutating. So it is with the stems, stolons, flower- 

 peduncles, and leaves of older plants. We may, there- 

 fore, infer with a considerable degree of safety that all 

 the growing parts of all plants circumnutate. Although 

 this movement, in its ordinary or unmodified state, 

 appears in some cases to be of service to plants, 

 either directly or indirectly— for instance, the circum- 

 nutation of the radicle in penetrating the ground, or 

 that of the arched hypocotyl and epicotyl in breaking 

 through the surface — yet circumnutation is so general, 

 or rather so universal a phenomenon, that we cannot 

 suppose it to have been gained for any special pur- 

 pose. We must believe that it follows in some un- 

 known way from the manner in which vegetable tissues 

 grow, 



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