260 BOTANICAL GAZETTE. [ October, 
variations in the amount of transpiration, or to the diminution of the 
water-content of the leaf, produced by injury or disease of the roots or 
stem. The direct influence of absence of light is comparatively slight, and 
the relation between temperature and defoliation was not fully enough 
tes i i i i 
solution of the middle lamella, by action of a ferment rather than by re- 
sorption of the wall. 
Dr. J. von Sacus gives in Arbeit, Bot. Inst. Wiireburg (iii. 372-388), the 
details of the experiments from which he Rochidee, that the invisible 
ological action—the yellow ra the d 
e yell ys and those near them cause 
Spa of carbon dioxide, and are active in assimilation; the blue and 
visible violet rays are the agents in the movements of irritation, 
