304 Bower . — Studies in the Phytogeny of the Fi lie ales. 
receptacle rises symmetrically from the leaf-surface, here it is compressed 
below the indusium, and develops its basipetal sequence as a rule only on 
the side away from the leaf-surface. None the less is it a gradate sorus, 
and, contrary to my statement of 1899 (1. c., p. 76) (which was made from 
old sori), irregularly intermixed stages of sporangia have not been observed 
in the young state. The segmentation of the sporangia is also a matter 
for note. It will be seen that the stalk is a relatively massive one with 
irregularly inclined walls (Fig. 38,$). This corresponds closely with what 
is seen in Onoclea sensibilis , and with the Cyatheoid series, and is in sharp 
contrast to the simple transverse segmentation of the stalk seen in Davallia 
(Studies, IV, Figs. 134, 135). In form the mature sporangia of Cystopteris 
correspond to those of Struthiopteris in having their annulus continued to 
the stalk, but there interrupted ; while the stalk itself is relatively massive, 
and consists of three rows of cells. But the number of cells of the annulus 
is smaller than in Struthiopteris , being only about thirty. The conclusion 
is, then, that sorally Cystopteris is in near relation to Onoclea and Struthio- 
pteris , and is essentially of the Gradate type ; while the characters of 
anatomy and of habit support the alliance with the Cyatheoids, and espe- 
cially with certain of their derivatives. Schlumberger, however, considers 
that the facts of development of the sorus indicate a relationship of 
Cystopteris to the Davallieae ( 4 Flora 5 , 1911, p. 408), rather than with the 
Cyatheoid series. This opinion I do not share, preferring to regard the 
peculiarities of the sorus as a consequence of a flattening of the receptacle 
between the indusium and the leaf-surface, together with an absence of the 
sporangia on the side of it next to the leaf-surface. 
The characters of the prothallus of Cystopteris , as described by Schlum- 
berger (l. c., p. 386), are of some importance in considering the relation of 
the genus to the other Ferns mentioned above. The hairs which it bears 
are only unicellular glandular hairs, as in the 4 Polypodiaceae ’, not multi- 
cellular as in the Cyatheaceae. Further, the lid-cell of the antheridium is 
undivided, which is again a Polypodiaceous as against a Cyatheoid feature. 
These characters, together with the flattened type of the sorus above 
alluded to, accentuate the aloofness of the genus. But its gradate sorus 
and its anatomy and habit all indicate a relationship to the Ferns with 
a basal indusium. It may be held to occupy a middle position linking the 
Woodsieae, especially Struthiopteris , with the Aspidieae. 
Acrophorus , Presl. 
This genus was founded by Presl in 1836, to receive the single species 
now designated A. stipellatus , (Wall.) Moore. It was placed by him in close 
relation with Cystopteris : but the species had previously been styled Aspidium 
nodosum by Blume. Sir Wm. Hooker merged it in Davallia , but evidently 
with some doubt, as it stands in the 4 Species Filicum ’, vol. i, p. 157, under 
