THE AMERICAN BOTANIST 57 



10 degrees in the average plant. The rising and lowering lines 

 never coincide thus giving a lateral movement as well ; t he- 

 two motions which when combined, generate irregular 

 ellipses. The amount of vertical and lateral movement var- 

 ies with the time of day, amount of moisture and heat, and 

 due to these conditions the ellipses are variable. 



The periodicity of plant movements is a very interesting 

 phenomena. Generally they rise a little in the evening and 

 early part of the night, sinking again on the following morning. 

 The upward movement in the evening is at first slow, begin- 

 ning at very different hours, and gradually increasing to a 

 ma.ximum. Leaves possessed of a pulvinus have more dis- 

 tinct nocturnal movements, known as "nyctitropic movements." 

 The insectivorous plants are very little affected as far as their 

 movements are concerned by light, and it is probable that they 

 do not have any night movements. 



CIRCUMNUTATION OF CUMBERS AM) RIXXKRS 



The ^im[)lest case of modified circumnutation is found 

 in the movemment of climbing plants, with the exception oi 

 those Avhich climb by rootlets or motionless hooks. The climb- 

 ers have a tremendous amplitude of movement, caused verv 

 likely by the greatly increased grow^th over a small length. 

 The movement is more regular than of ordinarv plants, but 

 the ellipses are formed in all directions. 



This i)ower is innate in the plant, and is not excited by 

 any external agent except touch so far as can be ascertained. 

 It is this power which has been gained for the sake of ena- 

 bling climbing plants to ascend to a greater height and thus 

 reach more light. The tendrils in their movement, feel a 

 support and twine spirally around it. The circumnutating 

 stems of some plants can twine around a support only when 

 it is thin and flexible, while some can twine around a support 



