Early History of Lycopods 215 
also in the entire group, there is an evident relation to the Equisetales ; 
hence it is of great interest that Nathorst has described, from the 
Devonian of Bear Island in the Arctic regions, a new genus Pseudo- 
bornia, consisting of large plants, remarkable for their highly com- 
pound leaves which, when found detached, were taken for the fronds 
of a Fern. The whorled arrangement of the leaves, and the habit 
of the plant, suggest affinities either with the Equisetales or the 
Sphenophyllales; Nathorst makes the genus the type of a new class, 
the Pseudoborniales. 
The available data, though still very fragmentary, certainly suggest 
that both Equisetales and Sphenophyllales may have sprung from a 
common stock having certain fern-like characters. On the other hand 
the Sphenophylls, and especially the peculiar genus Cheirostrobus, 
have in their anatomy a good deal in common with the Lycopods, 
and of late years they have been regarded as the derivatives of 
a stock common to that class and the Equisetales. At any rate the 
characters of the Sphenophyllales and of the new group Pseudo- | 
borniales suggest the existence, at a very early period, of a synthetic 
race of plants, combining the characters of various phyla of the Vascular 
Cryptogams. It may further be mentioned that the Psilotaceae, an 
isolated epiphytic family hitherto referred to the Lycopods, have 
been regarded by several recent authors as the last survivors of the 
Sphenophyllales, which they resemble both in their anatomy and in 
the position of their sporangia. 
The Lycopods, so far as their early history is known, are remark- 
able rather for their high development in Palaeozoic times than for 
any indications of a more primitive ancestry. In the recent Flora, 
two of the four living genera? (Selaginella and Isoétes) have spores 
of two kinds, while the other two (Lycopodium and Phylloglossum) 
are homosporous. Curiously enough, no certain instance of a homo- 
sporous Palaeozoic Lycopod has yet been discovered, though well- 
preserved fructifications are numerous. Wherever the facts have 
been definitely ascertained, we find two kinds of spore, differentiated 
quite as sharply as in any living members of the group. Some of 
the Palaeozoic Lycopods, in fact, went further, and produced bodies 
of the nature of seeds, some of which were actually regarded, for 
many years, as the seeds of Gymnosperms. This specially advanced 
form of fructification goes back at least as far as the Lower Carboni- 
ferous, while the oldest known genus of Lycopods, Bothrodendron, 
which is found in the Devonian, though not seed-bearing, was typically - 
heterosporous, if we may judge from the Coal-measure species. No 
1A, G. Nathorst, ‘“‘Zur Oberdevonischen Flora der Baren-Insel,” Kongl. Svenska 
Vetenskaps-Akademiens Handlingar, Bd. 36, No. 3, Stockholm, 1902. 
2 Excluding Psilotaceae. 
