The Philippine Journal of Science, C. Botany 
Vol. XIII, No. 6, November, 1918. 
THE THEORY OF LIMITING FACTORS 
By William H. Brown 
(From the College of Liberal Arts, University of the Philippines, and the 
Bureau of Science, Manila, P. /.) 
one text figure 
Since the appearance in 1905 of Blackman’s 1 paper on limit- 
ing factors, this subject has received considerable attention. In 
his paper Blackman postulates as an axiom: When the process 
is conditioned as to its rapidity by a number of separate factors, 
the rate of the process is limited by the pace of the 4 slowest ’ 
factor. 
While such a theory might work in some cases, it may be said 
that it is a theory only, and that it has not been proven 'to be 
generally applicable to physiological processes. Blackman’s best 
evidence appears to have been deduced from Matthei’s work on 
photosynthesis. 2 However, Brown and Heise 3 have shown that 
the conclusions reached by Matthei were due to misinterpreta- 
tion. An examination of their paper would seem to show that 
this work cannot be used in proof of Blackman’s theory. In re- 
viewing Brown and Heise’s paper Crocker 4 made a mistake in 
saying that they misquoted Kanitz’s formula, an error which 
he himself has since corrected. 
The idea of limiting factors as developed by Blackman has 
not been clearly understood by all writers on the subject, so it 
may be well to examine its meaning. According to Blackman’s 
development of this theory, there would appear to be a limiting 
factor for a physiological process under all conditions. An 
increase in the intensity of any other factor (unless, perhaps, 
the increase were so great as to be harmful) would be without 
effect, as the rate of the process is limited by the limiting factor. 
Blackman, F. F., Optima and limiting factors, Ann. Bot. 19 (1905) 
281-295. 
* Matthei, G. L. C., Experimental researches of temperature on carbon 
dioxide assimilation, Phil. Trans. Roy. Soc. London B97 (1905) 47-105. 
3 Brown, W. H., and Heise, G. W., The application of photochemical 
temperature coefficients to carbon dioxide assimilation, Philip. Journ. Sci. 
12 (1917) Bot. 1-25. 
* Crocker, Wm., Photosynthesis, Bot. Gaz. 65 (1918) 568-569. 
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