Bower.—Studies in the Phytogeny of the Filicales. 523 
more advanced than itself. There can now be little question of the relations 
of Cheiropleuria downwards. Its nearest affinity is with Dipteris , and less 
closely with Matonia. This is shown by the similarity of form of the shoot, 
and of the dermal appendages. The form of the lamina, and especially of 
those variants of it which have more than two cusps, and the venation also, 
link it clearly with Dipteris. The steps towards a webbed character of the 
lamina seen in D. Lobbiana , quinquefurcata , and conjugctta lead, in a manner 
which cannot be overlooked, to the more complete integration of the lamina 
as it is seen in the one-cusped type so frequent in Cheiropleuria. This 
conclusion is also borne out by comparison of the outline and venation of 
the leaves of young plants of Dipteris. 
In venation, the types of Gleichenia , Matonia , Dipteris , and Cheiro¬ 
pleuria form an interesting sequence. In Gleichenia the venation is open 
throughout, thus showing a state which is usually held to be primitive. In 
Matonia there are occasional vein-fusions, especially in relation to the 
sorus. But in the narrow-leaved species of Dipteris such fusions are so 
frequent as to form a reticulum, while in the webbed species D. conjugata , 
the type is that of ‘Venatio Anaxeti ’. This venation is characteristic also of 
Cheiropleuria , as it was also of the fossil genera, Dictyophyllum , Clathropteris , 
and Hausmannia (see Seward, Fossil Plants, vol. ii, p. 380, &c.), which have 
been referred to the Dipteridinae. Thus, as regards the venation, Gleichenia 
corresponds to the type prevalent in the Palaeozoic Period ; Matonia takes 
a middle position, and the Dipteridinae show a venation characteristic of 
Mesozoic or later periods. Cheiropleuria is, as regards this character, as 
recent as any of them, notwithstanding the primitive structure seen in 
its axis. 
The Matonioid Ferns, including the Dipterids, have been habitually 
regarded as Gleichenioid derivatives (Land Flora, pp. 622, 623). But 
hitherto the anatomical conditions have not materially helped this com¬ 
parison, for in the mature state both Matonia and Dipteris have advanced 
solenosteles, while Gleichenia shows in most of its species a protostelic state. 
It is here that Cheiropleuria comes in as a synthetic link. The comparison 
of its protostelic axis with that of Gleichenia (Figs. 8-12) is very striking. 
Similarly its leaf-trace comes off at first as an undivided strand, though its 
early division into two indicates a state advanced beyond that of any 
Gleichenia , or indeed -of Matonia. But it shows some similarity to what 
is seen in Dipteris Lobbiana , which is even more advanced in the division 
of its leaf-trace ; for it there arises as two or even four distinct strands 
(Text-fig. 6). 
As regards the protostelic state of Cheiropleuria , it may be noted that 
a similar protostely has been found in the young plant of all of the related 
Ferns which have been examined. Thus Cheiropleuria maintains to maturity 
that primitive anatomical state which others have departed from early. 
