176 POPULAR SCIENCE MONTHLY. 



of tubes. This conclusion, however, disregards many well-known ad- 

 verse facts. Thus it is possible to secure the conduction of an impulse 

 through a section of stem, one or even two centimeters in length, which 

 has been killed by a steam jacket and allowed to desiccate. Then 

 again, when excised stems have been placed in connection with the 

 most powerful force pumps, or the action of the strongest osmotic solu- 

 tions, and artificial disturbances set up, no reactions were induced in 

 the pinnules, although great hydrostatic movements must have been ini- 

 tiated. The above mentioned hypothesis must be declared 'not proven,^ 

 although it is a puzzling matter to attempt any suggestion of a method 

 by which transmission could be accomplished tl>rough 2 cm. of dead 

 tissues, and a meter of living tissue. 



3..J:; 



Fig. 5. Fibrillar Structures in Cells of Plerome of Root of Onion supposed hv 

 Nemec to transmit Impulses. 



Nemec finds a somewhat regular coincidence of fibrillar structures 

 in the apical portions of roots, with the pathway which impulses should 

 travel in passing from the perceptive region to the motor zones. The 

 occurrence of these structures has been well known for some time, and 

 the theory of their function as special transmitting organs has something 

 in its favor, especially as these fibrillae have continuous intercellular 

 communications. No facts are at hand to suggest the presence of 

 these fibrillar organs in other members of the body. 



The decentralized organization of the plant, the intimate and deli- 

 cate morphogenic and physiologic correlations existing among all its 

 members and its reflective system of irritability, make unnecessary, and 

 preclude, the differentiation of transmitting tracts, except in certain 

 narrowly specialized organs adapted to other than their typical vegetative 

 purposes. The most recent hypothesis as to the geotropic action of the 



Fig. 6. Statolithic Action of Cells of Stelar Sheath containing Starch, by thk 

 Aid of which Equilibrium is supposed to be maintained. 



plant is in accordance with these ideas. By this theory the maintenance 

 of equilibrium is made possible by the appreciation of gravity as the 

 result of the position of granules in sheath cells in every part of the 

 body, these cells acting as statoliths and sending impulses to the motor 

 zones of the organs in which they are found. 



