430 ELECTRICITY. PART n. 



that plant, and in the Colocasia, the water flows in 

 canals along each rib into a general duct, which runs 

 along the border of the leaf, and terminates in an orifice 

 upon the surface. 



Since electricity is developed by chemical action in 

 unorganized matter, it may be inferred that it is also 

 developed within the vegetable cell where so many 

 organic compounds are formed ; but it is probably given 

 off from the points of the leaves or by evaporation from 

 their surfaces. Professor Fleming ascertained by actual 

 experiment, that the sap of a leaf, and its surface, are in 

 different electric states ; he also found that the surface 

 of the spongioles of the roots of plants and the ascending 

 sap have opposite electricities. Both of the preceding 

 cases the Professor ascribes, in part at least, to organic 

 changes which take place during vegetation. Slight 

 currents of electricity were obtained from the petioles of 

 flowers, but fruits and tubers give powerful electrical 

 currents due to the reaction of different vegetable juices 

 upon one another. The tuberose is said to emit scin- 

 tillations and dart small sparks of light in a hot electric 

 evening, and gardeners have long been aware that mush- 

 room spawn is most prolific in stormy weather. 



The irritability of the tissues of plants which renders 

 them liable to be acted upon by external causes, has 

 occupied the attention of many celebrated botanists. 

 From experiments by Professor Ferdinand Cohn and his 

 pupil M. Krabsch upon the irritability of the stamens in 

 the florets on the discs of composite flowers, more espe- 

 cially the Centaureas, they have come to the conclusion 

 that susceptibility to the excitement of light, as well as 

 to tha,t of mechanical and probably electrical impulse, is 

 possessed by all young vigorous tissues, and upon com- 

 paring the phenomena of these with those of animal 

 irritability, they further conclude that the faculty of re- 

 sponding to external irritation by internal movements 

 and change of form, belongs to cells, and holds good in 



