364 
SUMMARY OF CURRENT RESEARCHES. 
Recording' Apparatus for the Study of the Transpiration of 
Plants.* — Mr. A. F. Woods describes an apparatus which he has found 
useful for this purpose. It consists essentially of two parts, a balance 
and a register. The two parts are in an electrical circuit which is opened 
or closed whenever the equilibrium of the balance is disturbed. When 
the circuit is closed, the movement of the armature of the magnet 
mounted on the left arm of the balance engages a notched wheel, which 
turns a long screw parallel to the beam. This screw works in a half-nut 
attached to the carriage of the counter-weight, and is adjustable, so that 
the weight may be set at any point along the beam. For recording 
evaporation a left-hand screw is used, moving the weight from left to 
right. As evaporation from the plants goes on, the right arm of the 
scale rises, thus closing the circuit above the beam. The armature of 
the magnet is then attracted, and turns the screw carrying the counter- 
weight ; at the same time the pen on the register is carried along by a 
similar mechanism. This is continued until the balance is brought to 
equilibrium, and the circuit broken. Further evaporation causes a 
repetition of the process. 
Bot. Gazette, xx. (1895) pp. 473-6 (1 pi. and 1 fig.). 
