CHAP V MODIFIED CIRCUMNUTATION. 263 



CHAPTEK V. 



MODIFIED CIRCUMNTJTATION : CLIMBING PLAIT, s ; EPINASTIC AND 

 HYPONASTIC MOVEMENTS. 



Circumnutat.ion modified through innate causes or through the action 

 of external conditions Innate causes Climbing plants ; similarity 

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

 tude ; occasional points of difference Epinastic growth of young 

 leaves Hypouastic growth of the hypo^otyls and epicotyls of seed- 

 lingsHooked tips of climbiug and other plants due to modified 

 circumnutation Ampelopsis tricuspidata Sinithia Pfundii 

 Straightening of the tip due to hyponasty Epinastic growth and 

 circumuutation of the flower-peduncles of Trifolium repena and 

 Oxalis 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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