138 
DR JOHN M'LEAN THOMPSON ON 
its base — is a smooth and dorsiventral structure, channelled on one side (its left), 
and curved on another (its right) like the free rachial portion of a leaf. The left- 
hand limb of the second branching mentioned above is cylindrical and rugged 
like the lower part of the plant. For about f inch it remains slender, but above 
this it widens considerably and divides into three parts. The middle part is a 
short columnar structure with a slight central depression on its broad apex. The two 
lateral members show the same rachial characters as were noted above ; for though 
they are perfectly cylindrical for about 2 inches from their bases, they finally 
assume a dorsiventral form. Their channelled surfaces face each other, and no 
branching occurs. They end distally in fractured surfaces. 
The three distal branches may be tentatively held to be of petiolar character, 
Text-figs. 2-9. 
while the remaining portions of the plant may be considered axis. This division is 
in keeping with the figures and descriptions given of Stromatopteris. In the plant 
under discussion the petiole is exceedingly long, and greatly exceeds the 4-inch 
measurement given elsewhere ; but it should be remembered that during development 
the petiole is open to intercalary growth, and is accordingly liable to vary consider- 
ably in length. At no point in this specimen are roots apparent, and, as will be 
shown immediately, they are entirely absent. 
The rugged appearance of the branched axis is due to a very varied assemblage 
of emergences and dermal appendages. In some cases the emergences are mounds 
of thick-walled cells, irregularly disposed, and devoid of intercellular spaces. One 
of these mounds is represented in sectional view in text-fig. 2. On the other hand, 
many are large conical structures, composed of thick-walled elongated cells, which 
converge on a small-celled apical group. From the centre of this group springs a 
