378 
DR JOHN M'LEAN THOMPSON ON THE 
variation in sporangia! construction is a natural feature, and indicate transitional 
states from which a uniform sporangial type with regular vertical annulus might 
emerge. At the same time they suggest that as in stem and leaf, so also in sporangia 
similar advances may not be made in all features. 
General Conclusion. — The anatomical state of Llavea is regarded as transitional. 
It bears no conclusive evidence of the nearer affinities of this plant, though the 
solenostely is such as to indicate a connection downwards. The dermal appendages 
show mixed characters, but the scales are distinctly advanced. The stelar anatomy 
provides no outstanding characters which suggest direct phyletic comparisons. 
The leaf- trace is simple, but of a more advanced type than is seen in J amesonia. At 
its base the anatomical state is peculiar, and is open to interpretation as showing 
a first step towards division of the trace in the median radial plane. This is held 
to be a feature of advance. As in J amesonia, the pinna-trace supply is of a simple 
marginal origin. It is open to a Schizseaceous comparison, but carries no decisive 
weight in a question of affinity. 
With Cryjptogramme it shares the possession of dimorphic pinnules, but the 
sporangial characters detailed are sufficiently distinctive to preclude a belief in a 
close affinity for these plants. The occasional reticulations mark the venation as of 
a more advanced type than is seen in J amesonia. 
Individually the structural features are indeterminate. The most significant is, 
however, the presence of scales of advanced type. Collectively they constitute a 
transitional state giving a more advanced condition than is seen in J amesonia. 
The “ Acrostichoid ” sporangial arrangement is open to the same explanations as 
were advanced in the case of Jamesonia. It may be the result of extension of non- 
indusiate sori along the veins, or a primitive arrangement as in modern Schizaeacex. 
The sudden transition from the “ simple ” to the “ mixed ” condition during develop- 
ment of the superficially initiated sporangia is a feature of advance. The elongated 
stalk and the occasional vertical uniseriate annulus are upgrade characters, but the 
frequent irregularities of annulus are considered accompaniments of a change in 
position of the annulus. The sporangia are held to be of upgrade type, in which 
variation of the annulus may naturally be expected to persist, and is still pronounced. 
This constitutes a feature which provides a ready contrast with J amesonia. In the 
latter, irregularities of the annulus are fairly common, but never dominant. 
