52 Proceedings of the Royal Society of Edinburgh. [Sess. 
growth and division there occurred interruption and separation of the 
cells in the endodermal ring by the intrusion and growth between the 
endodermal cells of one or more parenchymatous cells either from the peri- 
cycle or from the cortical cells just outside the endodermis (see cells x, x, 
fig. 4). In either case there arose bending of the endodermal ring, and 
displacement of the cells as shown in fig. 5. The next few sections showed 
a rather quick disappearance of cambial activity until there was practically 
no division of pericyclic cells, and the endodermis was again a complete 
ring of typically thickened cells. Internal cambium then began again 
with a quick division of its cells, resulting in a considerable amount of 
separation of the cells of the endodermis by intrusive parenchyma. Again 
occurred a falling off of cambial activity, and a consequent linking up of 
the endodermal cells into a more complete ring. There were now If inches 
of root left uncut, and sections were continued at about If inches from its 
junction with the stem. The first sections cut here showed still a very 
small amount of internal cambium, and the endodermis almost complete ; but, 
in addition, there was a slight division of certain cortical cells just outside 
the endodermis. These formed small isolated patches of outer or external 
cambium made up of ten to twenty cells in two radial rows. The succeed- 
ing sections showed the endodermis complete and no cambial development 
on the inside, but there was increasing cambial development on the outside 
(fig. 6). The cells often divided by obliquely tangential walls, therefore did 
