106 A. H. Graves, 
A cross section of the coleorrhiza as represented in Text-fig. 23 
shows that it is composed principally of a single cell-layer. The 
section was cut purposely near the junction of root with stem, in 
order to show how toward the proximal end of the coleorrhiza a few 
of the cells of the subepidermal layer enter into its composition. 
As is shown by 
rae: SII) longitudinal — sec- 
Sad S tions, the cells inthe 
CoS: © i) outer or more distal 

region of this sub- 
a jacent layer are un- 
Qe doubtedly the re- 
AS sults of divisions 
Me: ee similar to those 
which take place in 
the epidermal or 
coleorrhizal layer, 
but at the proximal or basal part of this subjacent layer the cells 
are larger and two or three rows deep, and those immediately adja- 
cent to the root are considerably flattened. In this region, there- 
fore, the subepidermal layers of the coleorrhiza are derived im- 
mediately from the cells of the stem without division, being forced 
outward by the development of the root and coleorrhiza. 
Figure 25.—Portion of cross section of root show- 
ing surrounding coleorrhizal layer. >< 400. 
pe 

Figure 24.—Photomicrograph of longitudinal section of young 
root still enclosed in coleorrhiza; co/, coleorrhiza; 7, root. >< 50. 
Pl. VI, fig. 38 shows a well advanced stage, where by pressing 
with the cover glass the root was detached from its connection 
