1897 ] MYELOPTERIS TOPEKENSIS 17 
central medulla in which thin walled fundamental tissue pre- 
dominates, and a somewhat rigid, or at least firmer, outer zone. 
THE cCOoRTEX.—No proper cortical structure is represented 
in these specimens. The outer limits of the sections are defined 
by more or less broken down strands of sclerenchyma cells, with 
surrounding parenchyma tissue, making it clear that a certain 
amount of structure has been removed; and this accords with 
what has already been noted in specimens of Myelopteris, that 
“the tissue layers outside the sclerenchyma strands are very 
rarely preserved.’ In this case the thin surface layers of coal 
already described are in all probability to be regarded as 
representing the cortical structure, which must have been chiefly 
or wholly parenchymatous in character, and of small radial 
volume. <> 
THE SUB-CORTICAL LAYER.—The outer, continuous zone, 1.5™™ 
thick as aiready described, has its macroscopic differentiation 
from the medulla explained by the large amount of fibrous 
elements which it contains. Owing to the presence of these 
elements, and the peculiar way in which they are distributed, 
they have served not only to protect one another, but they have 
also served to prevent the effect of compression from falling 
with full force upon the intervening fundamental structure which — 
in consequence, has often retained its structural features in an 
exceptionally perfect manner (figs. 7 and 2). i 
_ PareEncHyMA.—The ground tissue, for the greater part, is 
much altered by decay and compression, so that all structural | 
features, a in the Seates area, cokes bee b pretty com- : : | ae 
