Woodhead : Notes on the Bluebell. 85 



Fig-. 9 is a tree map. The shaded areas show the distribu- 

 tion of shade trees, chiefly sycamore and elm. The unshaded 



Fig. 9. Distribution of trees in Birks Wood. 



part consists of trees with an open canopy, mainly oak. In- 

 dividual trees of other species are indicated by symbols. On 

 comparing- the two we find that while the bluebell g-rows in 



Fig. 10. Soil map. 



abundance in one part of the oak area, it is absent in others. 

 The species of overshadowing- tree, therefore, is not the sole or 

 even the main factor in its distribution. 



1904 March i. 



