34 



INDIAN FOREST MEMOIRS. 



Importance 

 of careful 

 Field Obser- 

 vations. 



plant in nature, the way in which they appear to act and the conditions capable of affecting 

 their action. The necessity of acquiring a preliminary knowledge of the factors at work 

 in each case, before attempting to organise experiments, or to interpret experimental 

 results, will be more clearly understood perhaps from an example. 



In the preliminary work which has been carried out with forest grasses it has been 

 ascertained that while Saccharum Munja may be killed out by repeated early firing on 

 sand, early firing on loam is practically innocuous. Also that although Andropogon 

 monticola may be more or less injured by an early fire on sand, repeated early firing on 

 such soil may result in this species becoming dominant on areas formerly occupied by a more 

 vigorous species Saccharum Munja, owing to the fact that the latter is liable to suffer more 

 severely by fires. If such points had not been ascertained by preliminary field work, it 

 is practically certain that experiments would have given incomplete and apparently contra- 

 dictory results, whereas when such points have been ascertained from field-work they can 

 subsequently be checked and confirmed by suitably organised experiments as opportunity 

 occurs, when this is considered desirable. 



The view which has been emphasized above then consists in this that forest experiments 

 cannot, as a rule, be properly organised in such a way as to give results of practical value 

 and of wide application and the results obtained from such experiments cannot as a rule 

 be correctly interpreted until careful and extended field observations have first indicated the 

 principal factors which are at work and the way in which they act. 



In addition to the above considerations also, owing to the recent organisation of the 

 ".Research Institute, the Botanist had not the staff required for the organisation and conduct 

 of extensive field experiments. 



31. While the capacity of forest experiments 

 (on the scale on which they are usually conducted) to supply satisfactory evidence regarding 

 the effect and importance of various factors is frequently over-estimated, the importance 

 of careful and systematic field observations on the other hand is often not sufficiently 

 appreciated. 



It has been pointed out in paragraph 28 above that satisfactory evidence can often be 

 obtained by careful and systematic field observations, In a wide series of observations in 

 which all important factors are constant, or vary only within very narrow limits, with the 

 only exception of a single important factor which varies considerably, if the growth and 

 vigour of a particular species is invariably found to vary in direct proportion to the 

 variations of that single factor, it is logical and permissible to conclude that such a varia- 

 tion of growth has been caused by the factor in question and such a conclusion is obviously 

 of great practical importance. 



Difficulty is of course experienced in the case of factors which are closely correlated, 

 such as the intensity of light and the amount of available moisture, when dealing with 

 species for which the possible range of intensity of both factors is very limited, seeing that 

 a given condition of growth may frequently be due as much to one of these factors as to 

 another. It is however perfectly possible to arrange a series of observations in the forest 



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