Bower.—Studies in the Phytogeny of the Filicales. VIL 59 
pteris and Dicksonia , Dennstciedtia and Microlepia , Hypolepis, Polypodium 
(Dryopteris , C. Chr. ?) punctatum, Thunbg., and Monachosorum. Another 
sequence, probably related to Dennstaedtia and Microlepia , includes Davallia 
in the widest sense, Deparia , Nephrolepis , and perhaps also Oleandra . In 
these the sorus becomes increasingly superficial. The fundamental leaf- 
type of all of them was the Sphenopterid, with separate ultimate lobes, each 
traversed by a single vein as in Thyrsopteris —a type essentially similar 
to that of Hymenophyllum. Webbing is, however, not an unfrequent 
feature. But it does not bring with it the coalescence of the sori to form 
fusion-sori. In fact these Ferns are characterized by the sori maintaining 
their individuality as discrete developments upon the separate endings of 
the veins . 
These Ferns may probably be seriated from Thyrsopteris as a relatively 
primitive type ; though Loxsomopsis may eventually turn out to be the type 
of a still more simple starting-point, linking on to Loxsoma itself. The 
sequences roughly sketched above may be compared on the basis of the 
criteria of habit, dermal appendages , vascular construction , soral position , and 
indusium , the receptacle and sequence of sporangia, and the characters of the 
sporangia themselves. Unfortunately their gametophytes are too imperfectly 
known to serve as a further basis for the comparison. 
In habit they are mostly rhizomatous : but Thyrsopteris is a low Tree- 
Fern. It has, however, horizontal underground runners with long internodes. 
The habit of Thyrsopteris is to that of the dendroid Dicksonias as that of 
Lophosoria is to the large Cyatheas. Both are to be interpreted as having 
acquired the upright habit secondarily from a rhizomatous origin, which the 
dendroid forms carried farther. The leaves are as a rule highly divided, 
though webbing is frequent, and they have an open venation in all except 
in Deparia Moorei , which is a highly derivative form. 1 
The dermal appendages of Thyrsopteris , Dicksonia , Dennstaedtia, 
Microlepia, Hypolepis , Polypodium punctatum , and Monachosorum are all 
simple hairs of a characteristic brownish colour. But in Davallia , Nephro- 
lepis , and Olea 7 idra scales are present, indicating them as relatively advanced. 
The vascular construction of all is based on the solenostele, which 
is simple in Cibotium , Dicksonia , Dennstaedtia, Microlepia , Hypolepis , and 
Poly podium punctatum, and is only departed from to a slight dictyostely in 
Monachosorum. But Thyrsopteris and Dennstaedtia adiantoides and rubi- 
ginosa have in their larger axes medullary complications. The leaf-trace is 
as a rule undivided. All these are then relatively primitive. On the other 
hand, Davallia , Nephrolepis, and Oleandra have advanced dictyostely, with 
highly divided leaf-trace: characters which again indicate for them an 
advanced organization. 
In soral position , that of Thyrsopteris is actually marginal, and remains 
1 See Thompson, Trans. R. S., Edin. 
