ORGANIZATION OF THE FOSSIL PLANTS OF THE COAL-~MEASURES, 699 
Plates 16 and 17; figures from camera-lucida drawings, made by 
Mr. Gzorcr Bresyer. 
PLATE 16. 
Fig. 1. Part of a transverse section of a young 9-arch root, at the commencement of 
secondary thickening. C.N. 1308. x 100. (See p. 687.) 
p, p, Cells of pith. 
x, x, Primary xylem. 
px, Protoxylem at the exterior of primary xylem. 
x*, x, Secondary wood, bordered externally by cambium. 
ph, ph, Two groups of primary phloém. 
en, en, Probably the functional endodermis. The thin-walled layers within 
this may be either perciycle or inner endodermis, 
c, c, Cells of the inner cortex. 
This figure represents part of the section figured by WiLLiaMson in 
“ Organization,” Part XII., Plate 28, fig. 2 (near d”), and is from the 
original specimen of “ Myriophylloides,” Hick and Casu. 
Fig. 2. Part of a transverse section of a more advanced 9-arch root. CO.N. 1314. 
X 100. (See p. 689.) 
p, p, Cells of pith. 
x, x, Strand of primary xylem. 
px, Protoxylem. 
x*, Secondary wood. 
fir, Fascicular ray. 
Fig. 3. Part of a radial section of a similar root. C.N.1317. x 100. (See p. 687.) 
~p, p, Pith. 
x, «, Primary xylem. 
px, Protoxylem at the outer border of «, consisting of spiral trachez. 
x*, Secondary wood. 
The parenchymatous tissue, /7, belongs to the fascicular ray. 
Fig. 4. Transverse section of a tetrarch rootlet. The outer cortex (similar to that 
shown in photograph 5) was partly preserved, but is not represented. 
C.N. 1888. x 100. (See p. 691.) 
px, The four protoxylem-groups of the primary wood, which probably 
reached the centre, though the central thin-walled cells perhaps 
represent a minute pith. 
x*, Secondary xylem, which is beginning to form between the protoxylem- 
groups. (Reference-line omitted.) 
ph, Phloém, of which there are four groups, alternating with the proto 
xylem. 
4x2 
