590 
Balls . — Temperature and Growth . 
Practical Conclusions. 
7. Under the conditions of this research it is unlikely that any other 
factor should be limiting at the ‘ stopping-point 5 than the factor ‘ x\ 
8. The Pfeiffer Hot-Box is quite unreliable for accurate measurements 
of the varying temperature of objects in the microscope field. 
9. The ordinary forms of hanging-drop culture chamber are also 
unreliable when used with other than constant temperatures, on account 
of the irregular heating of the various parts, of the temperature-lag induced 
by the proximity of the objective, and of the changes in drop-concentration 
which result from this irregular heating. 
My sincere thanks are due to Dr. F. F. Blackman, who has given 
me much assistance in the early stages of the work by advice on apparatus 
and methods. The present paper is to be regarded as an attempt to extend 
to growth-phenomena the principles which he has outlined in ‘ Optima and 
Limiting Factors 
Works of Reference. 
Blackman, F. F. — Optima and Limiting Factors. Ann. Bot., vol. xix, No. LXXIV, April, 1905. 
Blackman, F. F., and Matthaet, G. L. C. — A Quantitative Study of Carbon dioxide Assimilation 
and Leaf Temperature in Natural Illumination. Proc. Roy. Soc., vol. B., 76, 1905. 
Smith, A. M. — On the application of the theory of limiting factors to measurements and observations 
of growth in Ceylon. Ann. Roy. Bot. Gard., Peradeniya, vol. iii, part 2. 
Pfeffer. — Physiology of Plants, vols. i and ii. Oxford, 1900. 
Appendix. 
Influence of Temperature on Infection. 
The artificial infection of a cotton seedling with the Sore-shin fungus 
can be readily effected by placing the former on several layers of damp 
blotting-paper in a Petri dish, and then placing a fragment of rapidly 
growing mycelium from a cool culture in contact with it. The dish is 
then stored at 2o°C., and within twenty-four hours the seedling will be 
found to have rotted at the point of inoculation. The portion of the 
seedling stem which is in contact with the damp paper is not usually 
rotted, because at that point the aeration is usually insufficient. 
If the trial is repeated at a temperature of 33 0 C., a brown superficial 
scar is formed, 1 but the fungus does not extend its attack into the inner 
layers of the cortex. 
At 38° C. no infection can be found. 
On the ‘ ^-hypothesis 5 it should be possible to bring about rapid 
infection at the higher temperatures by keeping the infected area in contact 
1 The whole research was founded on this observation. 
