BUTTERWORTH, Structure of Psaronius. 



Explanation of Plate 2. 



Fig. I. Photograph of a portion of a section cut through 

 the roots of Psaronius cromptonensis, showing 

 ttvo roots (a) and {b) without secondary 

 thickening, (c) a root tvith secondary growth on 

 one side. 



Fig. 2. Photograph of the central cylinder of a root of 

 Psaronius cromptonensis with a complete ring 

 of secondary wood. 



