563 History of the Doctrine of [BOOK in. 



the mean temperature of the same period, the products do not 

 deviate widely from one another in the same species. It was 

 thereupon assumed that these deviations are due to incorrect 

 observation, and that such a constant product of the period ot 

 vegetation and the mean temperature will be found in every 

 species. This product then received the unmeaning appella- 

 tion of the sum of the temperature. If such a relation between 

 vegetation and temperature really exists, it would necessarily 

 follow that other things, such as light, moisture, the soil, &c., 

 have no influence at all on the period of vegetation, not to 

 speak of those internal causes which help to complicate the 

 simplest processes of growth. It is unnecessary to expose in 

 this place the absurdities involved in this idea of the sum of 

 the temperature ; the needful remarks will be found in the 

 ' Jahrbiicher fur wissenschaftliche Botanik' of 1860, i. p. 370. 

 It is a remarkable fact however that such monstrous reasoning 

 should have been able to prejudice science in various ways even 

 later than the year 1860. A new science was actually invented 

 and called Phaenology, which accumulated thousands and thou- 

 sands of figures, in order to discover the sum of the tempera- 

 ture for every plant, and as this crude empiricism showed that 

 the simple multiplication of the period of vegetation by the 

 temperature gave no constant result, the square of the tempera- 

 ture was tried and other tricks of arithmetic adopted. Though 

 Alphonse de Candolle as early as 1850 expressed well-founded 

 objections to the whole of this method of treating the subject, 

 in which the mean temperature played much too important a 

 part, yet he was so far unable to keep clear of the prevailing 

 ideas, that he thought he could express the effect of light by an 

 equivalent number of degrees of temperature, and so save the 

 supposed law of temperature in vegetation. To this idea may 

 be traced his work on the geography of plants, published in 

 two volumes in 1855, which however contains a rich treasure 

 of personal experience and knowledge of the works of other 

 writers. 



