Proceedings of the Linnean Society of London - University Library

58
PEOCEEDI^'GS OF THE
these organs are of too advanced a type to throw light on the
probable derivation o£ the group.
The anatomical characters clearl_y indicate an affinity with the
Fern-stock closer than that with any other Cryptogamic phylum.
The male organs, now beginning to be known, further support
this affinity. Hence we are led to conclude that the Pteridosperms
had a common origin with the Perns, and may assume
that the common ancestors resembled Perns in being Cryptogamic
rather than Spermophytic.
The difficulty arises from the surprising extension of the
Pteridosperms, which threaten to absorb everythmg Palaeozoic
that used to be called a Pern. But this idea is of the nature of a
" scare." Though the Perns were not the dominant group in the
Palseozoic that they were once supposed to be, there is as yet no
justification for the extreme view that they were non-existent.
The important position of the Botrj^opteridese as a synthetic family,
perhaps most nearly i-epresenting among known Palaeozoic plants
the common stock from which Perns and Pteridosperms may have
sprung, has already been indicated by a previous speaker. I agree
with him that the family is best regarded as a special type of a
much more extensive group.
As regards the other great question under discussion—the
affinities of the Coniferse—the data are still very inadequate, for
we have little knowledge of the structure of early forms of
Coniferae. In some Permian plants referred to Araucarieae, the
structure of the wood was of the Araucarioxulon type, a widespread
form of wood, common to Cordaitese, Pteridosperraeae, and
even Botryopterideae, but almost wholly absent from the Lycopod
phylum. Whatever this character may be worth, it favours a
connnon origin of the Araucarian Conifers with the Cordaitean
and Pteridospermic series.
The existence of the Cordaitese, offering clear points of agi-eeraent
at once with Pteridosperms, Cycads, Giukgoales, and Conifers,
certainly suggests that all these groups ultimately had a common
oingin from the same great plexus of primitive Pilicineae. Ginlr/o
itself forms a bond of union between the Cordaitean phylum and
the Taxaceae among Conifers.
The Lycopods attained a high development on their own lines,
producing seed-like organs in certain cases, and showing some
anatomical analogies with Conifers. A more exact comparison
appears to indicate that these characters are homoplastic, and not
indicative of any affinity with the higher plants.