EXTERNAL FACTORS ON THE SPAWN DATE 



145 



shows the beta coefficients, calculated as percentages. They give a 

 good idea of the relative importance of the factors. It can be seen that 

 the most important are — 



Retarding influences: raised temperature in Mo, increase in 

 latitude, increased simshine in Mi. 



Accelerating influences: increase in longitude, raised temperature 

 in M2, increased rainfall in Mi. 



Table 7 

 j3 COEFFICIENTS 



This list alone is enough to show how impossible it would be to 

 unravel such a complex subject without a large quantity of data and a 

 full use of statistics. No human mind could hope to see what was 

 happening merely by examining the records, much less by making 

 observations in one district. 



Discussion 



It now seems desirable to gather together a considerable number of 

 the compHcated facts that have been discovered, for if they are con- 

 sidered as a whole, it will be seen that they form a defmite pattern, not 

 detectable from any of them alone. 



The properties of water appear everywhere. There is the effect of 

 rainfall, viewed simply as an accelerating factor. Apart from this, a 

 critical point at o°C can surely not be related to anything else than 

 the freezing point of water. The evaporation of water from the soil is 

 of economic importance, and Penman (1948) showed that the main 

 factors in this are: temperature, wind velocity, humidity and bright 

 sunshine. Run-off is obviously related to the same factors, with the 

 addition of the rain itself It is well known that run-off ceases altogether 



