CHAPTER XVIII 



THE ELECTRIC CHARGES ON THE SPORES 



ALTHOUGH the matter may be of but small biological interest, it 

 seemed desirable to ascertain whether or not the falling spores 

 carry electric charges, and, if so, of what kind. The apparatus for 

 the investigation of the problem was constructed as follows. A 

 brass chamber, shown at B by two sections in Fig. 67, was supported 

 on a rod, R, and covered in front and behind with glass discs, GG'. 

 At its centre were fixed two brass plates, PP', 1/2 cm. wide and 

 2 cm. high, so that they were parallel to one another and about 

 1*5 mm. apart. The plates were attached to wires introduced 

 through lateral holes in the chamber, insulation being secured by 

 means of glass tubing, TT', and sealing-wax, S. Above the plate 

 was suspended a piece of the pileus of a Mushroom, F, with the 

 gills looking downwards. This was held in position by means 

 of a pin stuck into a cork, K, covered with tinfoil, N. The brass 

 chamber, and thus also the piece of fungus, was carefully earthed 

 by means of a wire attached to a gas-pipe at E. By means of 

 other wires the two plates were connected with a mercury com- 

 mutator, C. The latter was then connected on one side with the 

 gas-pipe, E, and on the other with the city main, M, of 220 volts. 

 The lamp, L, was placed in the circuit for the purpose of detecting 

 any accidental flow of current. By moving the handle of the 

 commutator to the right, both the piece of fungus and the brass 

 plates were earthed and therefore rendered neutral, whilst by 

 moving it to the left the plates were given charges of opposite 

 signs. 



A vertical plane, passing between the plates towards their 

 centres, was focussed and observed by means of a horizontal 

 microscope with a magnification of about 25 and a field of 



view 5'5 mm. in diameter (cf. Plate IV., Fig. 29). When the 



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