NOTlCS ON THE BISHOP PINE 



89i 



often thereafter as was practicable. Both seedbeds were treated after 

 sowing with 0.1 fluid ounce of commercial sulphuric acid per square 

 foot of seed bed area as a preventative against damping-off injury. 



Table 3. — Comparative Total Gennination of Bishop Pine Seed During go Days 

 Including Those Which Died After Germinating. 



This table indicates two interesting things : 



(1) The germinating capacity of seed from young trees is much 

 higher in general than that from old trees even though the seed has 

 been retained in closed cones for the same length of time. 



(2) There is apparently no relation between the length of time 

 seed has been held in the cones and its germinative capacity ; inspection 

 of the table indicates this lack of correlation but it is more positively 

 demonstrated by calculation of the Pearson coefficient of correlation, 



r = in which x and y represent the two sets of values; 



n6x6y 



in the present case x = age of cones and y = germination per cent. 



The coefficient r not only shows presence or lack of correlation but its 



magnitude indicates to what extent one set of values is related to 



the other. 



Carl Hartley in a recent paper describes the significance of this 



coefficient correlation as follows : 



"A perfect correlation should result in a coefficient of 1.0 and a 

 perfect inverse correlation in a coefficient of — 1.0, while if the 

 subject and relative vary absolutely independently of each other the 

 coefficient should be 0. In actual use neither of these figures will be 

 obtained. In cases where one set of values is absolutely dependent on 

 the other on the face of the figures there will be no need of calculating 



