138 Recent Work on Transpiration. 
In the course of the work on transpiration the present writer 
has collected a number of data with regard to the behaviour of 
stomata under various conditions, such as the loss of water 
from the leaf (see Laidlaw and Knight, 16), the effect of the con¬ 
tinued exclusion of light from the plant and the existence of 
an induced rhythm of opening and closure. These details, however, 
at present lack correlation, and it is not proposed to publish them 
yet, but work has been intermittently in progress. 
In 1916 a series of experiments was started to investigate 
further the phenomenon of the preliminary stomatal opening which 
occurs on reducing the water-supply of the leaf. The work involved 
the determination of the leaf water content at various stages of the 
process, but on account of the difficulties encountered owing to the 
variations of different leaves, the work promised to be laborious, 
and was therefore postponed in favour of other work then in hand 
until a more favourable opportunity should present itself. 
It is hoped that by means of the self-recording apparatus 
mentioned above, such problems as these may be investigated, 
with the object of throwing more light on the question of stomatal 
change in general. 
LITERATURE CITED. 
1. Bakke, A. L. Studies on the Transpiring Power of Plants as Indicated 
by the Method of Standardized Hygrometric Paper. 
Journal of Ecology, 2, 1914, p. 145. 
2. Bakke, A. L. The Index of Foliar Transpiring Power as an Indicator of 
Permanent Wilting in Plants. Botanical Gazette, 
60, 1915, p. 314. 
3. Bakke, A. L., and Livingston, B. E. Further Studies on the Foliar Tran¬ 
spiring Power in Plants. Physiological Researches, 
2, 1916, p. 51. 
4. Balls, W. L. The Stomatograph. Proc. Roy. Soc., 85, B, 1912, p. 33. 
5. Blackman, V. H., and Knight, R. C, A Method of Controlling Air Move¬ 
ments in Transpiration Experiments. Ann. Bot., 
31, 1917. 
6. Briggs, L. J., and Shantz, H. L. Hourly Transpiration Rate on Clear 
Days as Determined by Cyclic Environmental 
Factors. Journ. Agric. Research, 5, 1916, p. 583. 
7. Darwin, F. Observations on Stomata. Phil. Trans. Roy. Soc., 190, B, 
1898, p. 531. 
8. Darwin, F. A Self-recording Method Applied to Movements of Stomata. 
Botanical Gazette, 37, 1904, p. 81. 
9. Darwin, F., and Pertz, D. F. M. A New Method of Estimating the 
Aperture of Stomata. Proc. Roy. Soc., 84, B, 
1911, p. 136. 
10. Darwin, F. The Effect of Light on the Transpiration of Leaves. Proc. 
Roy. Soc., 87, B, 1914, p. 281. 
11. IIjin, W. S. Die Regulierung der Spaltoffnungen in Zusammenhang mit 
der Veranderung des osmotischen Druckes. Beih. z. 
Bot. Centralbl, 32, 1914, p. 15. 
12. Knight, R. C. The Inter-relations of Stomata Aperture, Leaf Water- 
Content and Transpiration Rate. Ann. of Bot., 31, 
1917. 
