Filicales. 
21 
even the most complex of existing Cyatheaceaj as having undergone, 
in their evolution from the Psaronieae, simplication of the stele (32). 
Mr. Gwynne-Vaughan’s researches, however, clearly show that the 
Cyatheaceae form a series of increasing anatomical complexity, and 
that the more primitive solenostelic forms were almost certainly 
derived from protostelic ancestors (20). Among other differences 
between the two orders may be mentioned the diarchy of the 
Cyatheaceous roots and the polyarchy of those of the Psaronieae. 
Rudolph states that if we imagine the reduction suggested by 
him for the Cyatheaceae to be continued we reach the vascular 
system of the Polypodiaceae, and are faced by the possibility of 
joining them anatomically on to the Marattiaceae. “ It is, however,” 
he adds, “ naturally equally conceivable that the Polypodiaceae are 
derived directly from forms with a simple axile strand, without 
having passed through a circuitous course of reduction from the 
Marattiaceae ” (32). Mr.Tansley’s and Miss Lulham’s interpretation 
of the Lindsaya- stele (44), and Mr. Gwynne-Vaughan’s (20), and 
Mr. Chandler’s (16) work on the Polypodiaceae, however, clearly 
show that the latter alternative is the more acceptable, and that 
the Polypodiaceae are, on the whole, a series of increasing com¬ 
plexity. These objections apply with equal force to a close affinity 
with Loxsoma ; the latter being monocyclic differs more apparently 
from the Psaronieae. 
The anatomy and sequence of the fossil Osmundaceae show 
that this order is very remote from the Psaronieae. Further it is 
obvious that neither Marsileaceae nor Salviniaceae are at all closely 
related to the Psaronieae. 
MAKATTIACE/E. 
The Marattiaceae are dictyostelic ; in Archangiopteris there is 
a circle of bundles, usually enclosing an internal strand, but the 
latter may be absent locally and the vascular system become 
temporarily monocyclic (21). Kaulfussia and Dancea are slightly 
more complex, for in them an internal strand is constantly present 
and rather better developed. Marattia may possess as many as 
three concentric series of bundles (11), while in Angiopteris there 
are numerous zones of anastomosing strands. There is every 
reason to suppose that the simpler genera are the more primitive, 
and that the series is one showing progressive elaboration of the 
stele. 
In Marattia and Angiopteris a little secondary xylem and cortex 
is developed from a local irregular cambium. In Angiopteris the 
elements of the secondary wood are but half lignified (23). These 
