RESPONSE OF ISOLATED VEGETAL NERVE 



469 



preparation I bifurcated the specimen, stripping away from 

 one of the two limbs the fibre-vascular elements, and from 

 the other most of the ground tissue. Galvanometric connec- 

 tions were now made with the free ends of the fibro-vascular 

 and ground tissues respectively, and stimulus was applied by 

 means of transverse cut, or by application of a hot plate 

 across the area of union. The transmitted effect was now 

 perceived as galvanometric negativity, at the end of that 

 strip which was composed of fibro-vascular elements. 



In studying this 

 subject of conduction, 

 I found the transmitted 

 effect of excitation to 

 be universally well ex- 

 hibited in the petioles 

 of ferns, successive re- 

 sponses, obtained at a 

 distance from the point 

 of stimulation, being 

 in their case singularly 

 perfect and uniform. 



From this I was led 

 to the conclusion that 

 the disposition of the 



conductors must here 

 be particularly well 

 adapted to their purpose. 



FIG. 279. Frond of Fern with Conducting 

 Nerves N exposed in Enlarged Figure to Right 



I had long been desirous of isolating 

 whatever elements in the vegetable tissue were to be regarded 

 as performing the function of nerves, and it appeared to me 

 that I had here found a good subject for this investigation ; 

 and accordingly, on carefully breaking the hard casing of the 

 petiole, and pulling it away in both directions, I was able 

 to isolate the conducting fibro-vascular threads, which were 

 long, soft, and white in colour, remarkably similar in their 

 appearance to animal nerves (fig. 279). These threads vary 

 in number with different species of ferns, and resemble 

 animal nerves in general appearance. It is sometimes 



