EOCENE FERNS. 
59 
The preceding table^ is full of suggestive interest and contains new evidence bearing 
upon questions of the highest physical importance. 
In conclusion the principal types are recapitulated, in order to include details of 
distribution and relationship to other recent and fossil Eerns omitted in the specific 
descriptions. 
1. Gleichenia Hantonensis, Wanhlyn. (Page 43.) 
The only Gleichenia yet met with in the Eocene closely resembles G. dichotoma, the 
sole existing representative of a well-defined subsection of the genus. The agreement 
between them is striking, and extends to some minute details ; thus, the primary veins 
are grouped and divided identically, the sori are identical in form, and, like in G. dicho- 
toma, although usually situated on the upper or left hand secondary vein only, some- 
times occur on both the secondary veins. This duplication of the normal single sorus to 
each primary vein characterises De Bey and Ettingshausen's genus Bidymosorus, a 
genus which can hardly now be sustained since G. dichotoma has sometimes more than one 
sorus to each primary vein. From the very fragmentary condition of the few specimens 
figured by De Bey and Ettingshausen, it cannot yet be said that the possession of two 
sori to each primary vein is a constant character. But were the fixity of this character 
apparent there might now be hesitation in attaching specific value to it. The stipes, 
rachis, and even the leaves in vernation were glabrous. 
Specimens of Gleichenia dichotoma from Sydney and East Australia appear less rigid 
and more membranous in character than those from elsewhere, and the Eocene species 
^ We have but to consider the almost complete absence of any records of other herbaceous plants, the 
difficulty with which mountain species, which form a large proportion of fern-floras, or species with such 
habits as Ophioglossum, Asplenium ruta-muraria, A. Ceterach, &e., could find their way into these deposits, 
to realise that we are probably only acquainted with those ferns whose habits favoured their preservation. 
But as nearly the whole of them have been found at Bournemouth, almost on one spot, and as 
repeated search has brought no new forms to light, there can be little doubt but that we possess a nearly 
complete knowledge of the Eocene lowland forest fern-flora of at least this locality, and probably no existing 
area would furnish a greater variety of types under similar conditions. Although, therefore, the number is 
small compared to other orders of plants, we cannot help believing the fern-flora to have been extremely 
rich, considering, as we have said, the complete absence of genera even as cosmopolitan as Asplenium, whose 
habits are less favorable to preservation. 
The British and foreign Ferns provisionally placed together in this table were united, in some cases, 
from a comparison of illustrations and descriptions only, and the grouping is therefore to a certain extent 
but an indication of useful work still to be carried out. 
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