CuAi'. IV. OIECUMNUTATIOM 201 



CHAPTEE IV. 



Tub OlKCDMNUTATING MOVEMENTS OP THE SEVEEA. PABTS Off 



Matube Plants. 



Circumnutation of stems : onncluding remarks on— Circumnutatioii ol 

 Btol(jns: aid thus affmded in wiiidiog amongst the sti.msof sur- 

 rouniling plants — Circumnutation of flower-etema — Circumnu(ution 

 of Dicotyledonous leaves — Singular oscillatory movement of leaves 

 of Dionifia— Leaves of Cannabis sink at night — Leaves of Gymno- 

 sperms— Of Munocotvkdons — Cryptogams — Concluding reinurks 

 on the circumnijt iticn of leaves : generally rise in the evening and 

 sink in the morning. 



We have seen in the first chapter that the stems of all 

 seedlings, whether hypocotyls or epicotyls, as well as 

 the cotyledons and the radicles, are continually cir- 

 cumnutating — that is, they grow first on one side and 

 then on another, such growth being probably preceded 

 by increased turgescence of the cells. As it was 

 unlikely that plants should change their manner of 

 growth with advancing age, it seemed probable thai 

 the various organs of all plants at all ages, as long as 

 they continued to grow, would be found to circum- 

 nutate, though perhaps to an extremely small extent. 

 As it was important for us to discover whether this 

 was the case, we determined to observe carefully a 

 certain number of plants which were growing vigor- 

 ously, and which were not known to move in any 

 manner. We commenced with stems. Observations 

 of this kind are tedious, and it appeared to us that it 

 would be sufficient to observe the stems in about a 

 score of genera, belonging to widely distinct families 

 and inhabitants of various countries. Several plants 



