SECTIONAL TRANSACTIONS.—K. 487 
7. Mr. C. Hunrer and Miss K. M. Ricu.—Observations on the Effect 
of Carbon-diexide Accumulation on Root Elongation. 
Variations of carbon-dioxide concentration affect the rate of root elongation. 
Plants show different degrees of sensitiveness to this factor. Attention is here 
restricted to the reactions exemplified by Vicia Faba and Impatiens Balsamina. 
Modifications of the rate of root elongation due to the addition of carbon 
dioxide or the removal of accumulations of this gas can be detected by direct 
measurement. The occurrence and duration of minute fluctuations during root 
elongation are affected by this treatment. The addition of carbon dioxide 
disturbs the equilibrium of the condition of the root as indicated by changes 
of its electrical resistance. 
8. Mr. F. Y. Henperson.—The Direct Effect of Light on the Rate 
of Water-loss from the Mesophyll of the Leaf. 
The evidence for and against the control of transpiration by stomata is 
reviewed. The question of the direct action of the mesophyll cells in such 
control is discussed, and experimental work—using Darwin’s ‘ slitting ’ method, 
in which the stomata are rendered non-operative—is brought forward. 
9, Mr. 8. G. Jones.—The Life-history and Cytology of Rhytisma 
acerinum. 
(1) The ascospores : dispersal and germination; penetration and cytology uf 
the germ-tube. 
(2) Infection experiments : formation of the conidial stroma and cytology of 
the conidia. 
(3) The apothecial stroma: its development in the epidermis; the sexual 
organs, their development and cytology; cytology of the ascus. 
(4) Ecology of the parasite. 
Friday, September 14. 
10. Dr. F. F. Buackxman, F.R.S.—Oxygen and Respiration. 
11. Prof. V. H. Buacxman, F.R.S., and Mr. A. T. Leaa.—The 
Effect of Electric Currents on the Growth of Plants in Pot 
Cultures. 
Pot-culture experiments carried out during a period of six years with wheat, 
barley, and maize show that these plants exhibit increases of dry weight when 
subjected to electric currents as low as 0.1x10-!° amp. per plant. A percentage 
increase in dry weight of 27+5.7 was shown by maize plants grown under glass 
for little more than a month. Currents of the order of 1x10-8 amp. per plant 
and higher were found to be injurious. With barley plants subjected to the 
discharge for various periods the greatest effect was obtained from electrifica- 
tion during the second month of growth, when an increase of 118 per cent. in 
grain and 39 per cent. in dry weight was obtained. 
12. Prof. V. H. Buackman, F.R.S., Mr. A. T. Lae, and Dr. F. G. 
GreGory.—The Effect of a Direct Electric Current of very 
Low Intensity on the Rate of Growth of the Coleoptile of Barley. 
There is a marked acceleration of growth when the coleoptile of barley is 
exposed to an electric discharge from a point charged positively (about 10,000 
volts), and placed at such a distance above it that a current of 0.5x10-!° amp. 
passes through the coleoptile. The increased rate shows itself from the first 
hour onward, reaching in the third hour a percentage increase of 7.53+1.95. 
After the cessation of stimulation an after-effect, which is greater than the 
direct effect, is to be observed. The after-effect shows in the fifth hour a 
percentage increase of 15.68+2.62. The after-effect is greater with a short 
period of discharge than with a longer period. When the point is negatively 
charged the rate of growth is increased at first, but it soon falls again. An 
after-effect follows here also, but it is markedly less than that resulting from a 
positive discharge. 
