

442 



BOTANICAL GAZETTE 



[JUNE 



Holly, Dorsetshire, prickles on leaves 26 



Holly, Somersetshire, prickles on leaves 18 



Ash, Dorsetshire, leaflets on leaves 18 



Ash, Monmouthshire, leaflets on leaves 18 



Ceterach, Somersetshire, lobes on fronds 18 



Wild ivy, mixed, leaf-indices 17 



Spanish chestnut, mixed, veins in leaves 15 



Ash, Buckinghamshire, leaflets on leaves 15 



Spanish chestnut, Buckinghamshire, veins in leaves 14 



Beech, Buckinghamshire, veins in leaves ; 10 



29 



74 

 65 



57 



25 



77 

 72 



46 



77 



It appears by these comparisons that the lobing of the leaves of 

 Podophyllum is rather less variable than leaf characters in general. 



Turning now to the question of the degree of similarity between 

 the two leaves, and calculating the coefficient of correlation between 

 the number of lobes on the lower leaf and the number of lobes on the 

 upper leaf by the familiar product-moment method, we find the corre- 

 lations, 



For the Valley Park series 428± .028 



For the Palos series 468 ± . 029 



Difference 040± . 040 



I was considerably surprised when these values turned up on my 

 dividing machine. A priori, I would have expected considerably 

 higher coefficients, say about . 700, for the correlation between organs 

 so closely associated as the leaves of Podophyllum. In thinking of 

 the correlation between the leaves of Podophyllum, it had always 

 seemed to me organic rather than homotypic in nature. The two 

 leaves seemed so nearly exactly opposite and the whole "normality" 

 of the plant seemed to depend so much upon their forming a symmetri- 

 cal pair that I had expected the usual homotypic resemblance plus 

 something more. 2 But instead we find values which fall directly 

 in line with those found by Pearson and others for homotypes in 

 general. Taking merely the leaf characters noted above, we find the 

 homotypic relationship calculated by Pearson and his coworkers 

 (5) to be the following: 



Ceterach, Somersetshire, lobes on fronds - 6 3 x 



Holly, Dorsetshire, prickles on leaves -599 



3 For a clear statement of the distinction between organic and homotypic correlation 

 see page 340 of Pearson's splendid reply (6) to Bateson's criticism of the theory of 

 homotyposis. 



