580 Benson.—Mazocarpon or the Structural Sigillariostrobus. 
ground-plan, but differing in showing a constriction at the plane of 
attachment to the axis. The cone-scales are exceptionally caducous. 
There is no free lamella directed downwards, but a convex thicker 
portion without a ridge may extend to about o*8 mm. below the plane of 
the keel of the proximal part of the bract (cone-scale). The distal erect 
part tapers from 6 mm. in width to a point at not less than 6 mm. above. 
The sporangia are characterized by the possession of much sterile persistent 
tissue and the proliferation of the distal wall beyond the limit of the 
attachment of the sporange to the brae 
In the megasporange this lamella is shovel-shaped and fits into the 
adaxial concave surface of the upturned part of the bract. 
The megaspores are limited in number (the maximum so far found in 
any species of Upper Carboniferous age being eight) and germinate in situ ,' 
while the spore-wall is plastic. The organic apex of each so-called ‘ spore * 
is directed centroscopically with reference to the sporange. 
There is a considerable range of form, determined by the position 
which the germinating ‘spore’ occupies in the space between the sporange- 
wall and the subarchesporial pad. The form of those occupying the wider 
distal end of the sporange in M. Shorense tends to be that of a shallow 
crucible with the organic apex in the hollow, but many asymmetric forms 
occur. The spore-wall bears pointed prong-like teeth over its convex base, 
i. e. the surface directed towards the wall of the sporange. 
The cone is pedunculate. 
The sectional area of cone-axis and peduncle is so far found to be 
hexagonal. 
The cone may be several inches in length and half an inch in diameter. 
Denuded axes are far commoner than those with cone-scales still attached, 
only three of which have so far been recorded. 
One detached microsporange has been described and is shown to 
resemble certain incrustation specimens from the same horizon described by 
Dr. Kidston. 
Part II. The Evidence for the Attribution of 
Mazocarpon to Sigillaria. 
Section X. Introduction to Part II. 
Although Mazocarpon has been recognized since 1902, full data were 
not to hand respecting its form and dimensions. Without sections in 
recognizable planes or in series, the sporangial lamella was a very puzzling 
feature, nor was it possible to determine the number of megaspores and their 
relative position in the sporange. It was in the course of a special search 
for more material (see Section I) that the association of Mazocarpon with 
Sigillarian leaves was observed. This first clue was obtained in May, 1913, 
and, being confirmed by Dr. Scott’s observations independently, it was 
