$ 
; 
! 
1 
120 PROF. BOWER : 
sense, but states or conditions, which appear to have been arrived at along 
a plurality of lines of evolution. This had long ago been recognized in 
the case of Phegopteris, which is Polypodioid merely by abortion of the 
Dryopterid indusium: it is quite distinct racially from — Eupolypodium, 
Niphobolus, or Phymatodes, in which there is reason to believe that no 
indusium ever existed. It thus seems probable that the Polypodioid state 
may have arrived along a plurality of distinct lines. The same is the 
ease with the Acrostichoid state. All that now remains of the genus 
Acrostichum, according to Christensen’s Index, are A. aureum and prea- 
stantissimum. And these are now seen to be derived from Pteris. Other 
Acrostichoid Ferns have arrived from some five other phyletie sources. 
Though the matter is not yet worked out in detail, it may be confidently 
asserted that the large congeries of Ferns styled Gymnogramme had also a 
plural phyletic origin, some of the species being originally destitute of 
indusium ; others, such as G. Pozoi, being destitute of indusium by abortion. 
The species named is clearly a non-indusiate Asplenium, as is also the genus 
Aspleniopsis Mett. 
New attempts to group the Filicales phyletically have thus resulted in the 
recognition of a number of lines, divergent, parallel, or convergent, all 
starting from Eusporangiate sources. These were characterized by having a 
simple sorus, consisting of few sporangia, or even of a single one. There is 
reason to believe that the position of that sorus was in the first instance 
marginal. That is its position in the Botryopterids, the Ophioglossaces, the 
Schizæaceæ, and Osmunda, all very primitive types. In others, as in the 
Marattiaceæ, the Gleicheniacew, and Todea, the position is superficial. 
But in several lines of descent, notably among the derivatives from the 
Schizæaceæ, a transition from the marginal to the superficial by gradual 
steps can be traced. And it seems probable that such a transition is 
accountable for the origin of a superficial position in the other types 
also. But in them it was carried out at an earlier period in Descent. 
We may designate the first collectively as the * Marginales," and the 
latter as the ** Superficiales?” This may be recognized as a broad phyletie 
distinction, dividing the later Filicales into two, for the most part easily 
distinguished sequences. But our working hypothesis will be that this 
distinction does not mark an absolute difference: it is only a difference 
of degree in respect of the time of the transition of the sorus from the 
margin to the surface. But since the soral position is as a rule constant 
in the species or the individual, the distinction is reliable as a basis for 
phyletie segregation. 
Each of the two main phyla thus distinguished includes a number of 
subsidiary phyla. Of the Superficiales the Marattiaceze probably ended 
blind, except for their relation to the Cycadales. The Gleicheniacem 
probably led on the one hand to the Cyatheoid and Nephrodioid Ferns, 
and finally to their Polypodioid and Achrostichoid derivatives, such as 
