322 BOTANICAL GAZETTE [MAY 
institute at Leipzig since 1893 (18). Such a usage of the term 
is not in harmony with the meaning of “perception” in the 
domain of psychology, since here it is used to denote a much 
higher form of activity, coupled with the presence of conscious- 
ness, ora much higher form of consciousness than is exhibited 
by roots, and the use of the word “perception” to denote any 
of its functions is therefore wrong and misleading. It is evident 
that the most appropriate term must be derived from the term 
sensor. The following use of the term by Clifford (3, 2: 108) 
will illustrate quite fully the significance of the term: 
Various combinations of disturbances in the sensor tract lead to the appro- 
priate combination of disturbances in the motor tract. 
I have therefore denoted this specially irritable zone as the 
sensory zone. Some sharp distinctions exist between the general 
nature of the sensory zone of roots and that of tendrils and other 
special forms of irritable organs, in which a similar coincidence 
of several. forms of irritability occurs. In the latter, the sensory 
zone is composed of morphologically differentiated protoplasts 
which retain their directive function during the entire period of 
activity of the organ of which they form a part, and although 
they give rise to impulses in response to several classes of stim- 
uli, the reaction, with minor modifications, is invariable in kind 
and direction, and shows differences in degree due to the 
specialization of the motor tracts, which retain their epee! 
during the activity of the member of which they are a part In 
roots, on the other hand, the sensory function moves cgay 
from protoplast to protoplast, as also does the motor function; 
and while the sensory zone converts many different classes of 
_ stimuli into motor impulses, yet the reaction is by no means 
invariably the same. The root may move toward or away from 
_ the different stimuli, or may move toward an amount of stimulus, 
Pe constituting its optimum, and move away from a greater intensity 
of gues ees eae inclusiveness of the purpose of the root | 
as le for the wider range of reaction; and itis 
: also to be said that i 7 is a natural result of morphological neces 
= and ernie a : 
