794 
Notes . 
and cells such as a in Fig. 32, A are common, where a periderm ceil 
below the outer layer is beginning to take on the epidermoidal 
characters ; this explains the lack of linear continuity between the 
periderm as such and the outer layer, as the enlarging cell pushes the 
others to one side. In Fig. 32, B the linear arrangement is not 
disturbed, and we also get the remains of a layer outside the present 
functional one. 
It appears, therefore, that, at least in the English specimens, when 
periderm formation takes place, the primary epidermoidal layer of the 
young root is replaced by the specialized outer layer of periderm which 
is irregularly reinforced from the cells beneath. 
M. C. STOPES. 
University College, London. 
