42 AGRICULTURAL RESEARCH AND THE FARMER 



process of trial and error, with the possibility of failure and 

 consequent scrapping; and before any improvement on this 

 method can be suggested we must find out how it is that the 

 root -stock so greatly influences the tree.* 



Problems of this sort, referring to the inner processes going 

 on in the plant, and the effect upon them of such external 

 circumstances as temperature, humidity, amount of hght, and 

 soil conditions, are studied at the Research Institute in Plant 

 Physiology, which is attached to the Imperial College of Science 

 and Technology, London. In the preceding paragraphs an 

 attempt has been made to emphasise the vital importance of 

 fundamental physiological research, partly because an account 

 such as this, relating to the work carried out quite recently and 

 to investigations in progress, cannot be expected to contain 

 much that is of direct interest to the agricultural reader. The 

 physiologist is engaged in discovering the facts of life in the 

 plant; it is for the apphed scientist — the plant breeder, the 

 plant " doctor " and so on — to take those facts and apply them 

 to agricultural and horticultural practice. While, however, the 

 following record of work done may not appear to foreshadow 

 much immediate advance in agricultural methods, it is hoped 

 that it may not be without interest as showing the progress of 

 an important line of pure research, and indicating a few of the 

 difficulties with which the research worker has to contend. 



Factors influencing Crop Yield. 

 In the first instance we may refer to investigations which 

 "bear on the important problem of crop yield, already referred 

 to in the second paragraph. The object of the work is to find 

 out what are the various factors which make for yield, how they 

 are related to one another, and how they are influenced by 

 external conditions. For example, when we supply a crop with 

 a certain quantity of nitrogenous manure we get an increase 

 in the total weight. Is this because the capacity of the plants 

 for utihsing sunlight has been increased — in other words, has 

 their " appetite " been improved — or is the benefit due to an 

 increase in the leaf surface of the plants, thus enabUng them, 

 without increasing their "efficiency," to utilise more sunlight? 

 To answer this question requires a detailed study of the distribu- 

 tion of materials in the various parts of a plant throughout its 



* This problem is also referred tojon page 55, in describing the root-stock 

 research in progress at the East Mailing Research Station. A member of 

 the Imperial College staff is attached to the Station, in order that his 

 investigation of the physiology of root-stock influence may be carried cut 

 in direct association with the work on classification of root-stocks. 



