312 Bower . — Studies in the Phytogeny of the Filicales. 
as well as many other characters of structure and conformation above noted, 
which clearly point to a relationship. The nature of this relationship has 
probably been that they sprang from a common stock. But while Gleichenia 
was conservative in its sorus, it specialized in its foliar development, so as 
to rival even Lygodium. On the other hand, the Cyatheaceae adopted an 
extension of the receptacle, and lateral dehiscence of the sporangium, com- 
bining these advantages with reduced spore-output per sporangium. In 
point of habit they became upright, and many of them definitely dendroid. 
It is here that the phyletic interest of Lophosoria comes in. Its 
features mark it out as a synthetic type,, both anatomically and sorally. 
Its solenostelic structure and creeping adventitious rhizomes link on with 
the similar structure seen in the most advanced Gleichenias. Its undivided 
leaf-trace comes off like theirs from the stele. But its internodes are short 
in the upright axis, though the leaf-gaps rarely if ever overlap, so that there is 
not actual dictyostely. Further, the meristele of its larger leaves may show 
a simple but temporary division into three parts, which anticipates the 
greater subdivision of the leaf-trace in Alsophila and Cyathea. The dermal 
appendages of Lophosoria are hairs only, like the most advanced Gleichenias. 
Scales are associated with the hairs in the definitely dendroid Cyatheaceae. 
There is thus a parallel progression in this apparently trivial character also. 
But it is most clearly in the sorus that Lophosoria shows its synthetic 
character. For while retaining the simple sorus of Gleichenia without 
extension of the receptacle in height or in area, it shows the lateral 
dehiscence of the sporangia. Thus anatomically and sorally it occupies 
an intermediate position. 
It may accordingly be held that Lophosoria is a synthetic type, 
and represents a phyletically early condition of Cyatheoid development. 
In relation to it the three leading genera are readily seriated phyletically, 
Alsophila being the nearest to Lophosoria , Hemitelia taking a middle 
position, and Cyathea representing the most advanced type. This con- 
clusion may be based partly on the sorus, partly on the anatomy, and the 
following brief statement will show that there is a parallelism in the 
progression in both of these respects. 
The description given by Gwynne-Vaughan of the anatomy of the 
young plant of Alsophila excelsa shows that certain stages of structure 
believed to indicate a natural phyletic progression are passed through with 
varying rapidity by the young plant of that species (‘ Annals of Botany ’, 
xvii, pp. 709-11). It is at first protostelic ; it then becomes solenostelic; 
this again merges into the dictyostelic structure by overlapping of the leaf- 
gaps ; and finally the first indication of the internal vascular strands makes 
its appearance ‘ at about the tenth leaf’. Comparing this ontogeny with 
the vascular structure in the series we are contemplating, the first stage 
finds its correlative in G.fiabellata ; the second in G. pectinata , and also in 
