RECENT ADVANCES IN SCIENCE 409 



branch of ecology, which the author puts in the first place 

 and terms autecology , deals with the living plant as an individual 

 and with its response under natural conditions to the various 

 factors of its environment. The influence of environmental 

 factors upon the various metabolic activities and upon growth 

 is to be studied under this head, and secondly the changes 

 occurring in the structure of plastic tissues. Proceeding, it 

 is laid down that ecology, and in particular the plant physio- 

 logical aspect of ecology, has an important function in agri- 

 culture, and it is pointed out that what has to be studied is 

 " the preparation of optimal conditions," under which head 

 the soil, the atmosphere, the selection and breeding of stock and 

 the choice of time and location are involved ; and, secondly, 

 the " preservation of optimal conditions," which includes the 

 control of soil moisture, light, temperature, root interference and 

 disease. It is clear at a glance what a tremendous and almost 

 untouched field lies here before the plant physiologist, especi- 

 ally when it is remembered that each crop and species will have 

 to be studied separately and questions of selection and adapta- 

 tion to climate also considered, all these being of first economic 

 importance. 



Liebig's Law of the Minimum in Relation to General Biological 

 Problems, by Prof. Henry D. Hooker, Jr. (Science, vol. xlvi. 

 Aug. 31, 191 7). — This striking paper, contributed by a botanist 

 of standing, is again an indication of the new and revitalising 

 tendency which is carrying plant physiologists to the study of 

 the living plant as a whole and to the investigation of its growth 

 and metabolic response to environmental conditions in each 

 phase of its life-cycle. The main content of the author's com- 

 munication is that Liebig's Law of the Minimum, of which 

 Blackman's theory of limiting factors is an application, has no 

 meaning in relation to the final results of the great complex 

 of processes making up the general metabolism of the plant. 

 The theory of limiting factors has been of much use in the 

 study of single plant processes, in particular as applied by 

 Blackman in his researches upon carbon assimilation, and 

 Prof. Hooker holds that it is justified, as an expression of 

 the Law of the Minimum, when applied in this way to isolated 

 processes. But when the experimenter comes to deal with 

 the resultant of metabolic processes as expressed in growth 

 and development, the Law of the Minimum no longer holds in 

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