Electricity—Radium-, N-, and X-rays 
vegetable substances. Wood, leaves, seeds, bulbs, blot- 
ting-paper, as well as coal, resin, and jet, could all take 
photographs of themselves. The exposure varies from a 
few minutes to eighteen hours, and the only necessity is 
to make sure that the material is absolutely dry. He is 
careful, however, to point out that this effect is probably 
due not to radio-activity but to a vapour of resin.” 
There is also a mystery connected with what are called 
N-rays. These seem to be only produced by fresh and 
living protoplasm, for when the plants have been chloro- 
formed they do not give out N-rays.1® 
The botany of to-day contains therefore many in- 
teresting problems in physics which still await a proper 
explanation. 
1 Ewart. 2 Pollacci, Ewart and Bayliss, Plowman. 3 Stone. 
4 Lowenherz. © Foulerton and Kellas. § Sigmund. 
7 Polacci. 8 Molisch, (Dorn, Baumann, Valentiner). 
® Dauphin and Green, Koernicke, Dixon and Whigham. 
10 Green. 11 Tommasina, 12 Russell. 18 Meyer, 
ary 
