303 
Bower . — Studies in the Phytogeny of the Filicales . 
relation to Acrophorus . Christ (‘ Farnkrauter ’, p. 280) ranks it next to 
Woodsia. Influenced by the example of Sir W. Hooker, and after in- 
sufficient personal observations, I had in 1899 assented to the relation with 
Davallia , § Leucostegia (Studies, IV, p. 76, and ‘ Land Flora’, p. 655). It 
will now be shown, on the basis of wider comparisons, that the relation is 
rather with Struthiopteris and other Ferns which have a superficial sorus, 
basal indusium, and a basipetal succession of sporangia. 
The anatomy of the stock of Cystopteris fragilis has been examined 
by G wynne- Vaughan, who found it to have, like Struthiopteris , a dictyostelic 
structure. The leaf-trace also consists of two vascular strands which arise 
separately from the dictyostele (‘ New Phytologist ’, vol. iv, p. 315)- He 
remarks, with regard to the peculiar involutions above the insertion of the 
leaves, that its stem furnishes almost as good an example of the develop- 
ment of epidermal pockets as Struthiopteris ( Onoclea ) germanica itself* 
although the whole structure is on a smaller scale. Thus there is a sub- 
stantial anatomical similarity with the stock of Struthiopteris. If the 
pockets be left out of account the structure corresponds also with that of 
Woodsia ; though in Cystopteris the meristeles are smaller and further apart, 
the disposition of them is essentially the same . 1 
Sections of the young sorus of Cystopteris show conditions resembling 
those of Struthiopteris , but on a reduced scale, and modified in relation to 
the flattening of the receptacle under an indusium which lies parallel to the 
leaf-surface. The formation of the sorus begins slightly back from the 
apex of the leaf-lobe, as an upgrowth subtended below by the scale-like 
indusium. The first sporangium, which Schlumberger ( 1 . c., p. 408) describes 
as being prior to the indusium, appears with regularity on the middle of 
the convexity (Fig. 38, a), several large cells intervening between it and the 
insertion of the indusium. Transverse sections show that the first sporangium 
occupies also a median position in relation to the indusium (Fig. 38, b) ; in 
fact, it occupies the apex of the small flattened receptacle. A comparison 
may be made with what has been seen in Struthiopteris (Fig. 37). Later 
other sporangia appear right and left (Fig. 39), while the cells which inter- 
vene between them and the base of the indusium give rise also to a regular 
gradate succession in basipetal sequence (Fig. 40). A comparison of the 
latter drawing with Fig. 90 of my Studies, IV, shows how similar this 
condition of the sorus is to that of Onoclea sensibilis. A comparison with 
S. orientalis also shows correspondence, due allowance being made for the 
relatively small number of sporangia shown in the garden-grown specimens 
on which the observations were made. But whereas in these Ferns the 
1 This account does not accord with that of O. Schlumberger (Flora, 1911, p. 410), who states 
that only a single strand enters each leaf. His observations seem to have been made on a young 
plant (‘ Keimpflanze *), and it may be true for the first leaves ; but the leaves of mature plants are 
supplied by two distinct strands, as in Struthiopteris and in Woodsia. This is already recorded by 
Luerssen (Rab. Krypt.-Fl., iii, p. 447.) 
