144 LIFE OF 



amplified in a fresh volume, in which the veteran was mate- 

 rially assisted by his son, Mr. Francis Darwin. Its object 

 was to describe and connect together several large classes 

 of movements, common to almost all plants. The sur- 

 prising fact was established, that all the parts or organs 

 of plants, whilst they continue to grow, are continually 

 revolving, or circumnutating as Darwin called it. This 

 movement commences even before the young seedling 

 has broken through the ground. The combination of 

 this with the effects of gravity and light explains countless 

 phenomena in the life of plants. The tip of the rootlet 

 is thus enabled to penetrate the ground, and it is proved 

 to be more sensitive than the most delicate tendril. Move- 

 ment goes on through all stages of life. Every growing 

 shoot of a great tree is continually describing small ellipses; 

 the tip of every rootlet endeavours to do the same. The 

 changes of position of leaves and of climbing plants, and 

 the sleep of leaves are all brought under this great principle 

 of circumnutation. It is impossible in reading the book 

 not to be struck with the great resemblance between the 

 movements of plants and many of the actions performed 

 unconsciously by the lower animals. " With plants an as- 

 tonishingly small stimulus suffices, and, even with allied 

 plants, one maybe highly sensitive to the slightest continued 

 pressure, and another highly sensitive to a slight momentary 

 touch. The habit of moving at certain periods is inherited 

 both by plants and animals, and several other points of 

 similitude have been specified. But the most striking 

 resemblance is the localisation of their sensitiveness, and 

 the transmission of an influence from the excited part to 

 another which consequently moves. Yet plants do not 



