10 



in space and time ; and we explain many of its physical phenomena 

 by adopting the theory of undulatory or wave-like motion. Of 

 electiicity we are still more ignorant ; we cannot even assert it 

 to be a form of energy ; and yet we have had demonstrated to 

 us during the past year some very marvellous results produced on 

 organic life by the action of what is known popularly as the electtic 

 hght. We appreciate the results, but the complete elucidation of 

 the "how'' and the "why" has yet to be attained. 



The old satirist spoke with undisguised contempt of the 

 scientific experimentalists of his day, laughing at them as essaying 

 to extract "sunbeams fi'om cucumbers;" but now vegetable or 

 carbon points diffuse a light having many of the qualities pos- 

 sessed by sun-light. Sober men of science look upon trees and 

 plants as incorporating -within themselves the sun-light and heat 

 of to-day; while our coal fires, with their unconsumed smoke 

 and their fog-creative activities, represent the imperfectly liberated 

 sunbeams of prehistoric ages, warming our houses but eclipsing 

 our present sun. 



It has been long known, that vegetable organisms are to a great 

 extent dependent upon the direct influence of light for vigorous and 

 healthy development. The extreme sensitiveness of some plants 

 to the action of light has been clearly shown in a paper recently 

 read before the Linnean Society by Mr. Francis Darwin, on" "The 

 power possessed by leaves of placing themselves at right angles to 

 incident light." As an illustration, he took cotyledons of the 

 seedling radish. "When the plant is illuminated fi-om above the 

 cotyledons are extended horizontally, being thus at right angles 

 to the light falling upon them. If the seedling is placed at a 

 window, so that it is lighted obliquely from above, and if the stem 

 (hypocotyl) is prevented from bending, the cotyledons will accom- 

 modate themselves to the changed conditions by movements in a 

 vertical plane. The cotyledon which points to the light will sink, 

 Avhile the other will rise, until both are once more at right angles 

 to the incident light. Two different theories have been suggested 

 to account for this property in leaves. One by Frank, who 

 ascribes to leaves and some other organs a specific sensitiveness 

 to light, which, for simplicity's sake, he calls Transversal-heliotro- 

 pismus; the other by De Vries, who thinks the effect is produced 

 by the ordinary forms of heliotropism nnd geotropism acting in 



