Ill] THE EFFECT' OF TEMPERATURE 217 



accelerated at temperatures above the normal temperature of 

 incubation, that is to say the temperature of the sitting- hen. In 

 the case of plants the fact that growth is greatly affected by tem- 

 perature is a matter of famiUar knowledge; the subject was first 

 carefully studied by Alphonse De Candolle, and his results and those 

 of his followers are discussed in the textbooks of botany*. 



That temperature is only one of the climatic factors determining growth and 

 yield is well known to agriculturists; and a method of "multiple correlation" 

 has been used to analyse the several influences of temperature and of rainfall 

 at different seasons on the future yield of our own crops f. The same joint 

 influence can be recognised in the bamboo; for it is said (by Lock) that the 

 growth-rate of the bamboo in Ceylon is proportional to the humidity of the 

 atmosphere, and again (by Shibata) that it is proportional to the temperature 

 in Japan. But BlackmanJ suggests that in Ceylon temperature conditions 

 are all that can be desired, but moisture is apt to be deficient, while in Japan 

 there is rain in abundance but the average temperature is somewhat low: 

 so that in the one country it is the one factor, and in the other country the 

 other, whose variation is both conspicuous and significant. After all, it is 

 probably rate of evaporation, the joint result of temperature and humidity, 

 which is the crux of the matter§. "Climate" is a subtle thing, and includes 

 a sort of micro-meteorology. A sheltered corner has a climate of its own; one 

 side of the garden -wall has a different climate to the other; and deep in the 

 undergrowth of a wood celandine and anemone enjoy a climate many degrees 

 warmer than what is registered on the screen ||. 



Among the mould-fungi each several species has its own optimum tempera- 

 ture for germination and growth. At this optimum temperature growth is 

 further accelerated by increase of humidity ; and the further we depart from 

 the optimum temperature, the narrower becomes the range of humidity within 

 which growth can proceed^. Entomologists know, in like manner, how over- 

 abundance of an insect-pest comes, or is apt to come, with a double optimum 

 of temperature and humidity. 



* Cf. {int. at.) H. de Vries, Materiaux pour la connaissance de I'influence de la 

 temperature sur les plantes, Arch. Neerlandaises, v, pp. 385-401, 1870; C. Linsser, 

 Periodische Erscheinungen des Pflanzenlebens, Mem. Acad, des Sc, 8t Petersbourg 

 (7), XI, XII, 1867-69; Koppen, Warme und Pflanzenwachstum, Bull. Soc. Imp. 

 Nat., Moscou, xliii, pp. 41-110, 1871; H. Hoffmann, Thermisehe Vegetations- 

 constanten, Ztschr. Oesterr. Ges. f. Meteorologie, xvii, pp. 121-131, 1881; Pheno- 

 logische Studien, Meteorolog. Ztschr. iii, pp. H3-120, 1886. 



t See [int. al.) R. H. Hooker, Journ. Roy. Statist. Soc. 1907, p. 70; Journ. Roy. 

 Meteor. Soc. 1922, p. 46. 



I F. F. Blackman, Ann. Bot. xix, p. 281, 1905. 



§ Szava-Kovatz, in Petermann's Mitteilungen, 1927, p. 7. 



II Cf. E. J. Salisbury, On the oecological aspects of Meteorology, Q.J.R. Meteorol. 

 Soc. July 1939. 



^ R. G. Tomkins, Proc. R.S. (B), cv, pp. 375^01, 1929. 



