HOOKER LECTURE, 1922. 231 
reference. Ina preliminary account hy Dr. Bommer of the morphological 
features of specimens of Weichselia discovered by Father Schmitz at 
Bernissart in Belgium—a locality rendered classic by the wonderful assem- 
blage of Tguanodon skeletons—it is shown that in the structure of the stem 
and petioles, the habit of the fronds, and in the organisation of the sori there 
is a close resemblance to Matonia. Dr. Bommer thinks that in a less degree 
the sum of characters suggests comparison with the Marattiaceæ. 
Mr. Berry has figured some fern fronds, unfortunately sterile, from the 
Potomac Formation of Eastern America under the name Ânowltonella 
Maxoni, which he refers to the Matonineæ. The fronds are described as 
pseudodichotomous, at least in part; the pinnules are linear-lanceolate and 
the rachis is winged. No anastomosis of the lateral veins could be seen. 
This American fern resembles a Cretaceous species, Phlebomeris spectanda, 
figured by Saporta from Portugal, but neither affords convincing evidence of 
close relationship to Matonia. 
Map B (Pl. 17) is intended to present in broad outline the geographieal 
distribution of members of the Dipteris-Matonia alliance treated collectively ; 
it does not show the range in space of each genus, It is, however, important 
to consider briefly some of the data collected in the course of a general 
review of the geological records. 
It is not my aim to connect the Mesozoic records with the Paleozoic : 
between the two there appears to be a wide gulf. Among the numerous 
fronds of Pteridosperms and Ferns in the Upper Carboniferous and Permian 
strata there are indications, both in vegetative and reproductive characters, 
of possible connecting-links between the different phyla of Leptosporangiate 
Ferns which assumed a dominant position in the Rhætic and Jurassic 
periods. The difficulty of making direct contact between the age of Pterido- 
sperms and the succeeding age of Ferns may be largely due to the difficulty 
of determining whether a Paleozoic fern-like frond should be classed as 
a Pteridosperm or a true Fern, but on the other hand the relationship 
between the two ages may not be as close as it is usual to assume. In the 
latter part of the Triassic period we seem to pass with remarkable suddenness 
to a new phase of plant evolution ; the old order gives place to the new; one 
cycle is completed and another has begun. This transformation in the plant- 
world may be intimately associated with some far-reaching event in the 
physical history of the. earth’s crust. It may well be that crustal foldings 
in the latter part of the Paleeozoic era and the prevalence of desert or semi- 
arid conditions over wide regions during a part of the Triassic period were 
factors which influenced the progress and direction of plant development, 
The genus Camptopteris, if not the oldest, is one of the earliest represen- 
tatives of the Dipteris-Matonia line ; it occurs in the rich Upper Triassic 
plant-beds of Lunz in Austria, the flora of which has never been adequately 
deseribed. It occurs also in Upper Triassic beds in Würtemberg. The 
