318 
ON THE EOSSIL PLANTS OF THE COAL-MEASURES. 
Fig. 36. Diagram representing the arrangement of the foliar bundles and vessels of the 
medullary sheath. 
Fig. 37. Diagram representing a typical vertical section of a Lepidodendroid tree with 
Lepidodendroid branches, Diploxyloid stem, and Stigmarian roots. 
The letters of reference employed in the above figures are applied as follows, the 
application being as nearly as possible identical with that of my previous memoir ; I have 
given the list complete, though several of the letters refer to root-structures and other 
parts not described in detail in this memoir, and some additional ones are employed. 
a. Medulla. 
h. Medullary cells. 
c. Medullary vascular cylinder. 
d. Ligneous zone. 
e. Vessels of ligneous zone. 
f. Medullary rays. 
g. Innermost parenchymatous bark (rarely 
if ever present in these Burntisland 
plants as a distinct layer). 
h. Inner parenchymatous bark. 
i. Prosenchymatous bark. 
k. Subepidermal parenchymatous bark. 
L Leaf-petioles and leaves. 
m. Foliar bundles of vessels. 
n. Root-bundles of vessels. 
o. Rootlet. 
j). Cups for rootlets (not present). 
r. Cone-scars (not present). 
s. Axis of strobilus. 
t. Bracts of strobilus. 
u. Sporangium. 
v. Cellular sporangium-wall. 
w. Microspores. 
x. Macrospores. 
y. Leaf-scars. 
