368 
The British Association at Dundee. 
glucose or enzyme, while the blue, white and red flowers contain 
more or less of these. 
Physiological Papers. 
An interesting communication was contributed by Mr. 
Lawrence Balls on “ Thermotoxy or Factors in the Growth of 
Cotton in Egypt.” He had previously shown that the tempera¬ 
ture growth acceleration of a fungus hypha was arrested at a 
temperature of 37-5°C, owing to the formation and excretion of a 
toxic katabolite, and now brought forward evidence of a similar 
phenomenon in the higher plants. In Egyptian cotton under field 
conditions, growth takes place chiefly during the night, and, as a 
rule, follows the night temperature, hut when the day temperature 
has exceeded 35"C the growth during the following night is sub¬ 
normal, limited by the accumulated toxin. If a normal day follows 
the toxin is decomposed—probably oxidised, and the next night’s 
growth is normal. 
Different races and species of Gossypium differ in their liability 
to this poisoning, and there are indications that this liability is a 
character which shows Mendelian segregatiou. The growth-tem¬ 
perature curve of a root in non-aerated water-cultures suggests a 
similar toxic accumulation as the result of a limited air-supply. 
Mr. W. E. Hiley contributed a paper on “The Values of 
Different Degrees of Centrifugal Force on Geotropic Stimuli.” He 
described an ingenious apparatus based on the principal of Fitting’s 
intermittent clinostat, by which seedlings in a box are submitted 
alternately to a stimulus of gravity in one direction and any pre¬ 
arranged centrifugal force up to 20g. in the opposite direction. 
When the two opposing stimuli neutralise each other and the 
radicles show no ultimate bend, it is found that the product of the 
stimulating force multiplied by the time of action is the same in 
each direction. But these results were only obtained when the 
times were short. If the sum of the individual times in the two 
directions is greater than fifteen minutes, the larger force has less 
effect than that calculated on the basis given, and the radicles must 
be exposed to the force for a longer time in proportion to the period 
of rest. 
Professor Bottomley has found that when peat, which is acid 
in reaction and contains no soluble humates, is treated with certain 
micro-organisms, a large quantity of soluble humus is produced 
and the peat is rendered alkaline. An aqueous extract of the treated 
peat will supply all the plant food necessary for successful water 
cultures, while plants fail to grow in raw peat extract. 
Mr. A. G. Harper dealt with vitality and distribution of 
growth in defoliated Larch trees. The general effects of defo¬ 
liation were reduction in radial growth increment, and reduction in 
the ratio of the autumn tracheids to the total breadth of the 
annual ring. 
