Marsh , and its Relations to Evaporation, &c. 317 
(c) Mean of daily minima. Obtained in a similar manner to [b\ 
by taking the mean of all the absolute minima. 
(d) Mean diurnal range . This is calculated by first finding the daily 
range, i. e. the difference between the maximum and minimum for each day. 
The mean of all these is here called the mean diurnal range : it corresponds 
to the ‘ non-periodic amplitude 5 of meteorologists. 
(e) Absolute extremes are the actual maximum and minimum recorded 
during the whole of any series of experiments. 
Comparison between Sun and Shade Temperatures, etc. 
A comparison maybe made between the * temperatures in the sun 
taken at Wicken and the shade temperatures for the corresponding days 
taken at the Cambridge Botanic Garden. For this purpose the 1908 experi- 
ments will suffice. In Table V the means of the daily maxima were seen 
to be : — 
A, 23.5° C. : B, 25-6° C. : C, 22*2° C. 
The corresponding mean of the daily maxima at Cambridge was 21*5° C. 
Thus the mean maximum at A, four feet above the ground, and fully 
exposed to the sun and wind, was 2*o° C. higher than at Cambridge, also 
taken at four feet above the ground, but screened in the usual way. This 
may give some indication of the kind of differences that may be expected 
when sun temperatures are taken. But of course it is at best only a rough 
approximation. 
The means of the daily minima at Wicken, for the same period, were 
respectively : — 
A, 8.5° C : B, 6-0° C : C, 6-9° C. 
The mean of the Cambridge minima, taken on the grass, and therefore 
comparable to the Wicken minima, was 8*8° C. It was to be expected that 
the minima on low-lying marsh land should be lower than those on some- 
what higher, drier land. 
Bibliography. 
Blackman, F. F., and Tansley, A. G. (’05) : Ecology in its Physiological and Phytotopographical 
Aspects : A Review. New Phytologist, vol. iv, p. 232, 1905. 
British Rainfall (’69 onwards) : Formerly edited by Dr. G. J. Symons, now by Dr. H. R. Mill, 
London. 
Clements, F. E. (’05) : Research Methods in Ecology. Lincoln, Nebraska, 1905. 
Field, R., and Symons, G. J. (’69) : Appendix on Evaporation, see British Rainfall, p. 151, 1869. 
Goebel, K. (’91) : Pflanzenbiologische Schilderungen, Zweiter Teil. Marburg, 1891. 
Groom, P. (’08) : Longitudinal Symmetry in Phanerogamia. Phil. Trans. Roy. Soc. Lond., B., 
vol. cc, p. 57, 1908. 
