Ohap. V MODIFIED CIKCUMNUTATION. 2QiS 



CHAPTER V. 



Modified Ciroumnctation: Climeino Planvs ; Epinastio and 



HyPONASTIC MOVEMliNTS. 



Ciicumniitation modified through innate causes or through the action 

 of external coijditions — Innate causes— Cliiubing plants; similiirity 

 of tlieir movements with those of ordinary plants ; increased :impli- 

 tude ; occasional points of difference — Epinastic growth of young 

 leaves — Hyponastic growth of the hypo^'otyls and epitotyls of seed- 

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

 circumuutation — Ampelopsis tricnspidiita ■ — Smithia Pfuudii — • 

 Straightening of the tip due to liyponasty — Epinastic growth and 

 oircuiunuliition of the flmver-peduiicles of Trifulium 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 circumuutation 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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