Affinities of Sutcliffia . 
1051 
V. The Ground Tissue and the Secondary Cortex. 
The description given by Scott of the ground tissue of Sutcliffia 
insignis applies equally well in the case of the new fossil, for where patches 
of the cortex are preserved, ‘ the short-celled ground-parenchyma contains 
numerous sacs with carbonaceous contents, and is traversed by secretory 
canals and strands of sclerenchyma.’ The latter are in almost every case 
grouped round the leaf-trace strands, where they occur in an arc of three or 
four groups, varying in size, and lying on one side of the bundle only. 
A distinctive feature of the stem is the presence of a wide zone 
of tissue, which usually forms 
the limiting layer of the fossil, 
and which may attain a thickness 
of 15 to 20 elements in some 
parts. The elements composing 
this layer are clearly of secondary 
origin, for they are arranged with 
some regularity in radial series. 
Examination of longitudinal and 
transverse series shows the tissue 
to be composed of somewhat 
rectangular shaped cells, thin 
walled, and empty of contents, 
while occasional secretory ele- 
ments run between them (Text- 
%• 17 )- 
The development of this 
tissue can be traced in the upper 
part of the series. In the deli- 
cate tissues of the inner region 
of the cortex, here and there 
partially preserved, certain cells 
show obvious signs that a tan- 
gential division has just been completed (Text-fig. 18) ; in others further 
divisions have taken place. There can be little doubt that periderm forma- 
tion is here beginning. A comparison of the various stages of development 
between this beginning of periderm formation and the wide zone of tissue 
of secondary origin found lower in the stem has led to the conclusion 
that the latter represents only the secondary cortex produced by the 
phellogen. Support is given to this view by the fact that no sign of 
cambial activity can ever be detected on the inner margin of the tissue ; 
moreover, the cells do not show the characteristic features usually associated 
with cork, and finally it appears improbable that secretory elements would 
3 z 2 
Text-fig. 17. Transverse section of secondary 
cortex, x 70. s.c. = secretory elements ; i.s. = direc- 
tion of the stele ; o.s. ~ direction of the cortex. 
