CHAPTER XXXVIIi 



FUNCTIONS OF VEGETAL NERVE 



Feeble conducting power of cortical tissues Heliotropic and geotropic effects 

 dependent on response of cortical tissues only Phenomenon of correlation 

 Excitability of tissue maintained in normal condition only under action of 

 stimulus Physiological activities of growth, ascent of sap, and motile 

 sensibility, maintained by action of stimulus Critical importance of energy of 

 light Leaf- venation a catchment-basin Transmission of energy to remotest 

 parts of plants Plant thus a connected and organised entity. 



IN the animal body, different kinds of tissues are possessed 

 of different degrees of conductivity, the nerve being specialised 

 for the rapid transmission of stimulus. And it is now seen 

 that in the plant also we have a similar state of things, 

 cortical tissue, for example, though excitable, having feeble 

 conductivity, whereas the vegetal nerve possesses this power 

 in high degree. The question next arises : What is the 

 function subserved in the economy of the plant by a tissue 

 so highly specialised for the rapid conduction of stimulus ? 

 The various growth curvatures, by means of which plants 

 place themselves under the directive action of light and 

 gravity, are of advantage to the organism. But in bringing 

 about these movements, the plant-nerve takes little or no 

 part. And this is the case, even when the responsive 

 curvature takes place at a certain distance from the point of 

 stimulus. Here the transmission takes place slowly, through 

 the feebly-conducting cortical tissues. For example, in 

 Avena, curvature in consequence of such transmitted effect is 

 observed, even when the fibre-vascular bundles have been cut 

 across. 



If, indeed, the highly conducting nervous elements had 

 been concerned, these curvatures in response to unilateral 



