Bower.—Studies in the Phytogeny of the Filicales. VII. 61 
Dicksonioid Ferns, and borne on the distal ends of the veins, would form a 
peripheral series nearly related to one another. The fusion in the Pteris 
series does not stop at the ‘ webbing' of the ultimate segments, but extends in 
varying degree to the sori themselves, which become linked laterally into 
fusion-sori. A certain step towards this fusion has already been described 
by Goebel 1 in the case of Saccoloma elegans, which is probably related 
to Microlepia. In this case it is only the upper indusium which fuses, the 
lower indusium and the receptacle remaining separate. But in Lindsay a 
both the indusial lips are confluent, while the receptacles may show varying 
degrees of coalescence . 2 
The genera included in the Pteris series as thus characterized are 
Saccoloma , Lindsay a, Dictyoxiphium, Paesia , Pteridhtm , Lonchitis, Histio - 
pteris, Pteris (excluding Dory op ter is), and A nop ter is, with Acrostichum , L., 
as an ultimate derivative. They may now be compared according to the 
criteria already used for the Dicksonioid series. The large majority are 
rhizomatous, though some, such as Saccoloma , Dictyoxiphium, Lonchitis , 
some species of Pteris, and Acrostichum, are upright; but none develop an 
advanced dendroid habit, and the creeping axis is prevalent for the group. 
The more advanced webbing of the leaves leads to larger continuous surfaces 
of the lamina, with entire margins, as against the more deeply cut leaves of 
the Dicksonioids. This is less marked in Paesia and Pteridium, but 
becomes a more prominent feature in such Ferns as Histiopteris incisa , 
Lonchitis aurita, the Litobrochia section of Pteris, and finally in Acrostichum 
aureum. In all of these Ferns the further step to reticulate venation has 
been made, which is the physiological corollary upon advanced ‘ webbing \ 
Most of these Ferns have also advanced to the condition of bearing- 
o 
scales. These are sometimes restricted to the stock, and commonly they 
are associated with simple hairs. But the genera Paesia and Pteridium are 
distinguished by bearing hairs only, as in the case of Dicksonia, Dennstaedtia, 
and Microlepia. This indicates for them a special position. 
All of the creeping types, excepting Lindsay a, are solenostelic, but in 
those in which the stem is ascending or upright a dictyostelic condition may 
be approached. Accessory medullary developments may appear, which in 
Saccoloma, Pteris podophylla, and Acrostichum aureum reach a high degree 
of polycycly, while Pteris elata and Pteridium show this in less degree. 
These may be held as isolated signs of structural advance, seen in the later 
ontogeny of certain types. They indicate a capacity in these which does 
not materialize, if indeed it exists, in the rest. Being so sporadic as they 
are, the facts cannot serve as a basis for consecutive phyletic argument. 
The mature stelar state of Lindsay a is well known, as standing 
between protostely and solenostely. In this Lindsaya is peculiar among 
1 Flora, Bd. cv, 1912, p. 46. 
2 Studies, III. Ann. of Bot., vol. xxvii, PI. XXXIV, Figs, 20, 21. 
