ANATOMY AND AFFINITY OF CERTAIN RARE AND PRIMITIVE FERNS. 375 
laterally expanded, the two abaxial protoxylems are replaced by a single group, and 
phloem is on the abaxial xylem face alone (text-fig. 10). As will be seen from text- 
figs. 10, 11, the vascular supply to the pinna has a marginal origin. The potential 
perforation of the leaf-trace described above is a constant feature throughout our 
specimen, and seems worthy of special note. 
The mature sterile pinnules are cordate. Their venation is advanced, with the 
lateral veins reaching the margins and showing occasional simple reticulations 
(text-fig. 12). The fertile pinnules are typically long and narrow, and their 
margins are strongly inrolled and membranous ; there are no reticulations, and the 
lateral vein-endings fall far short of the margins (text-figs. 13, 14, 15). The only 
dermal appendages which have been found are simple hairs, scattered mainly 
among the sporangia along the veins (fig. 27) and on the pinnule-margins (text- 
fig. 15). 
Sporangia . — The sporangial distribution is “ Acrostichoid.” The mature condi- 
tion is a “mixed” one (fig. 27), and with few exceptions the sporangia are on the 
veins (text-fig. 14). The sporangial-stalk is slender, and consists of three rows of 
cells (figs. 27, 30, 37). The capsule is slightly lopsided, and the annulus is variable 
in both form and position. During development the same sudden transition from 
the “simple” to the “mixed” condition, recorded for Jamesonia, occurs, and in 
the mature pinnule the developmental range may be as in fig. 27. 
In only a small proportion of - the sporangia is the annulus uniseriate and 
vertical. The most regular condition found is represented in fig. 35, which shows 
