12 Bower.—Studies in the Phytogeny of the Filicales. VII. 
thickened nerve, excepting at the apex, and extending for various lengths: 
hairs either cell-rows or flattened scales : spores tetrahedral. Pterozonium , 
Jamesonia, Anogramme , Gym no gram me, Nothochlaena> Ceratopteris. 
The grading of these three divisions of the Pterideae was primarily on 
the relation of the sorus to the margin of the leaf. This point had already 
occupied Prantl’s attention among the Schizaeaceae, where he showed that 
the sporangia are actually marginal. In 1882 he wrote further with regard 
to certain Pterideae: ‘ In all the forms quoted, that is in the genera Pteris , 
Pellaea , and Cryptogram me, as also in Adiantum and Nothoclilaena (N. 
Marantae ), the first sporangium appears always at some distance from the 
leaf-margin; but in Cheilanthes it is quite close to it, so that as the young 
sporangia develop at first quicker than the margin, the appearance is almost 
as though (as they actually do in Mohrid) they sprang directly from the 
marginal cells/ 1 
Unfortunately this was tested by him only in two species of Cheilanthes. 
When these statements are put in relation with the old remark of Sir W. 
Hooker 2 that Mohria combines the capsules of the order (Schizaeaceae) 
with the habit of Cheilanthes , the suggestion of phyletic relationship 
directly with that order appears uncommonly strong. 
On the other hand, the series with double indusium included in Prantl’s 
Lonchitidinae, which differ widely in habit from Cheilanthes , show a soral 
condition comparable to the doubly-indusiate Dicksonia-Dennstaedtia series, 
in which the marginal origin of the sorus has recently been demonstrated. 3 
This suggests a second and probably distinct phyletic line. The first 
problem before us will therefore be, on the basis of new observations, to 
see whether there have not been two main lines of descent (possibly more) 
within the limits of the Pterideae. This will involve the revision of certain 
developmental and structural characters. 
Since we contemplate thus a reasonable probability of two modes of 
phyletic origin for the Ferns which have been designated Pterideae, it will 
tend to lucidity of exposition if the Ferns in question are described 
separately. This is especially desirable because they may appear closely 
alike in the structure of their sori, though this result may have been arrived 
at by different channels of evolution. The two series thus contemplated 
may be provisionally distinguished under the names ‘Pterideae bi- 
indusiatae ’, or Pteris series , in a restricted phyletic sense ; and ‘ Pterideae 
uni-indusiatae or Cheilanthes series. The former includes those in which 
there are, or in which there is reason to believe that in descent there have 
been, two indusia, as in the Dicksonioid-Davallioid-Lindsayoid Ferns ; and 
the grouping will apply whether or not the one or the other indusium is 
actually present, for either may be abortive. The latter will include those of 
Engler’s Bot. Jahrb., 1882, p. 484. 2 s yn . Fil., p. 436. 
3 Studies, III. Ann. of Bot., vol. xxvii, p. 443. 
1 
