MEMOIRS OF THE NEW YORK BOTANICAL GARDEN. 



209 



from electric arcs, and electrical illumination for six hours daily, with 

 confinement during the remainder of the day in a dark room, were 

 described. The light from the lamps was of 1,400 candle power, 

 measured photometrically, and was of such intensity as to injure 

 leaves placed within three or four feet, an effect probably due in 

 part to the high temperatures set up. Experiments in which the 

 normal daily illumination was supplemented by nocturnal electrical 

 illumination, showed the most vigorous growth and greatest develop- 

 ment, and the same effect extended to the flowers and fruit. Noth- 

 ing in the results described could be found to support the theory that 

 light exerts a paratonic effect upon growth. 



Fig. 160. Spinach {Spinacia oleraca). A, normal plant. B, specimen grown 

 n daylight supplemented bj nocturnal electrical illumination. Redrawn, after Bailey. 



Deherain exposed a number of plants to continuous illumination 

 from electric arcs in 1886. One series was cultivated in a darkened 

 chamber, and another in a clear glass house. The lamps used were 

 of a nominal candle power of 1,400 to 4,000 and the illumination 

 (with the accompanying temperatures) was sufficient to produce 

 many injurious effects upon the plants used. When the lamps were 

 shaded by glass globes, less injurious effect was seen and some 

 etiolative attenuations of stems and petioles were observed.^** 



'*^Ann. Agronom. 7: 551. 18S1. 



