56 
Proceedings of the Royal Society of Edinburgh. [Sess. 
cells below the curves, and also elsewhere in the pericycle, where there 
was previously no external cambium, divided up rapidly by periclinal 
walls. They thus formed a typical cambium from which were developed 
secondary bundles and conjunctive tissue. Such developments have 
already been noted by Haberlandt (1) and verified by Miss Spratt (4) 
as being of the nature of fibrous tracheids. As secondary growth from 
Fig. 10. 
the internal cambium spread round and became more active, the secondary 
tissue formed from it joined up through the gaps in the endodermis with 
that formed by the external cambium. The endodermal ring now 
appeared much broken, many of the cells being carried up on the outside 
of the internal cambium, and left lying in little groups of a few cells 
each in the midst of the thick- walled conjunctive tissue between the 
secondary bundles (fig. 10). The last sections cut from root 2 showed a 
