the flanking cells are much Jarger than the cells in the 
interior of the ray. No conspicuously vertically elongated 
| 
Texa Fic. Vangential section of sec- 
ondary wood, showing portions of one 
uniseriate ray and two multiseriate 
rays. The center ray, as characteristic 
of the larger rays, is composed of cells 
of two sizes; the larger along the mar- 
gin, and the smaller, internal. The 
outlines of the tracheids, rays, and 
some of the ray cells were drawn with 
a camera lucida. Other ray cells were 
drawn by direct comparison with the 
thin section. ~ 50. 
cells cun be observed 
either in the untseriate 
rays or at the margins 
of the  multiseriates 
(Text Fig. ). 
Cells of the cambium 
ure not visible, but the 
phloem tissue is” pre- 
served in some. areas. 
The sieve elements are 
crushed, but appear as 
double or triple rows 
between the — flaring 
phloem rays (Plate 
ILNIV, fig. 1). 
As noted, very little 
of the cortex was  pre- 
served, and leat’ traces 
were not seen. A single 
row ol sclerotic strands, 
just outside the phloem 
region, extends around 
the secondary body of 
rach) woody cylinder. 
There is no evidence of 
internally = developed 
periderm. 
Diagnosis 
Medullosa Olseniae Roberts & Barghoorn sp. nov. 
A stem, elliptical in cross sectional outline, approxi- 
mately two X four cm. in diameter at outer margins of 
. 
the ‘“‘polystele.”” The 
‘polystele’” consists of three to 
