190 THE HUMAN SIDE OF PLANTS 



numerous evidences of it in the plant's power to 

 discover the presence of objects necessary to its 

 welfare. A climbing plant, which needs a prop, 

 will creep toward the nearest support; but should 

 this be shifted to a spot several feet from its for- 

 mer position, the vine will, within a few hours, 

 change its course to the new direction. Is it possi- 

 ble that the plant sees the pole? This may explain 

 the action in this instance; but if the plant grows 

 between two mounds or ridges, and behind the one 

 ridge stands a wall, which will afford good climb- 

 ing, but is invisible from the position of the plant, 

 while behind the other ridge is no form of support, 

 the plant invariably will bend its course over the 

 ridge behind which is the wall. Examples of this 

 may be found wherever climbing or creeping plants 

 grow. The support is invisible from the plant's 

 starting point; and there is no odour which, as is 

 possible in the location of water, might give the 

 plant some clue to the direction in which its support 

 may be found. The only explanation seems to be 

 the existence in the plant of a psychic sense. 



There is at least one other sense which is pos- 

 sessed by plants to a marked degree. This may be 

 called the physical sense. For example, most 

 house-plants, which in their domestication have as- 

 sumed more or less artificial forms, will, on being 



