1922] BENSON—HETEROTHECA GRIEVII 125 
tended, narrow cells. These sheaths, probably as a result of the 
shrinkage of the tissues due to carbonization, often become sepa- 
rated from the tissues which must have abutted on them in the 
living state. In the case of the central loculi the sheaths are often 
ruptured or entirely 
dissolved away, leav- 
ing the spores among 
the elements of the 
ground tissue (figs. 5, 
11, 12). Small scle- 
rotic plates often be- 
come incorporated 
with the walls of 
loculi, and when seen 
in profile are very 
characteristic (text 
figs. 4, 6, stp"). 
In one synagium 
(figs. 11, 12) every 
loculus contains nu- 
merous ripe spores 
of tetrahedral form, 
similar in size and 
character to those in 
the pollen chamber 
of Sphaerostoma ovale 
(CN.270.1) among 
specimens of which 
it lies (text fig. 5). 
The spores measure 
29» in their trans- 
verse and 20u in 
their radial extent. 
Fic. 4.—Diagrammatic drawing of transverse sec- 
tion of class II synangium (CN.411.31); swollen ground 
tissue not entered in detail; two deeply lying vascular 
undles shown in transverse section (vb,, vb.); one pe- 
ripheral vascular bundle also cut transversely on left, but 
most are cut so obliquely that they are merely indicated 
by hatching; nerve ending seen near center with its 
delicate branch strand; one or two central loculi are 
broken down, and carbonization of peripheral ones prob- 
fig. 5); at 
in profile as in CN. 307.18, for which consult text fig. 6 
and fig. 12. 
In this specimen some of the locular walls have broken down, but 
many of the peripheral and at least two of the central loculi are 
still intact. In other cases spores can be demonstrated only in 
some of the loculi, while others show opaque black or dark brown 
