180 SECTIONAL ADDRESSES. 
fronds may, in fact, be regarded as the little-differentiated branches of 
a thallus. It is often impossible to say whether we have to do with 
the ramification of a stem or with a frond. Halle even suggests that 
one of his species of Psilophyton, P. Goldschmidtii, may furnish us 
with an intermediate stage between the two, as required by Lignier’s 
hypothesis. Plants of the Rhynia type may represent a still 
earlier phase, in which there was no differentiation whatever, but 
merely a branched thallus. It is a curious point that ‘the circinate 
vernation of the Fern-fronds is paralleled in the branches of Psilophyton 
princeps.’ 
The evidence, as at present understood, seems to suggest that, in 
the earlier Devonian Flora, Ferns, properly so called, may not yet 
have been in existence. The predecessors of the Ferns (Lignier’s 
‘ Primofilicinées,’ not Arber’s ‘ Primofilices ’) were there no doubt, but 
not, so far as we know, the Ferns themselves. Yet it seems that 
highly organised stems of a Gymnospermous type were already present 
at about the same period. Thus the evidence from the older Devonian 
Flora, so far as it goes, materially supports the opinion that the Seed 
Plants cannot have arisen from Ferns, for the line of the Spermophyta 
seems to have been already distinct at a time when true Ferns had not 
yet appeared. 
The idea that the Gymnosperms were derived, through the Pterido- 
sperms, from the Ferns, which I once advocated, must, I think, be 
given up, on grounds which were stated two vears ago at the Bourne- 
mouth meeting of the Association. It is safer to regard the Pterido- 
sperms, and therefore the Seed Plants generally, as a distinct stock, 
probably as ancient as any of the recognised phyla of Vascular 
Cryptogams, and derived from some unknown and older source. At 
the same time the striking parallelism between the Pteridosperms and 
the true Ferns must be recognised. These views are essentially in 
agreement with those previously expressed by my friend Dr. Kidston. 
I may be permitted to quote in this connection an interesting remark 
made by Professor Paul Bertrand in a letter received last year. He 
was speaking of a strange group of plants of Lower Carboniferous or 
possibly Upper Devonian age, the Cladoxylee. These plants have a 
complex polystelic structure in both stem and petiole, but seem to be 
quite distinct from the later and better-known polystelic family, 
Medullosee. Professor Bertrand, the chief living authority on the 
Cladoxylez, speaks of them as very primitive types, in which the 
distinction between stem and petiole was still but little marked. Yet 
he considers them as most probably Phanerogams. These views, if 
confirmed, imply that the Phanerogams or Seed Plants started as a 
distinct phylum, quite low down, at a phase when the differentiation 
between stem and leaf was still incomplete. 
Without laying too much stress on an expression of opinion such as 
Professor Bertrand’s, I believe the present evidence is in harmony 
with the view he suggests. The Spermophytes, as it seems, have been 
an independent class of plants from very early times; they are not 
to be derived from the Vascular Cryptogams, as we have hitherto 
conceived them, but are of the same standing with them, having sprung 
