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NOTICE OF A FOSSIL LYCOPOUIACEOUS FRUIT. 7
trace of a line of regular (lehiscence, are points iu Avbicli tliey resemble
specially the sporangia of Isoeies ; but in this genus the sporangia are
situated at the very base of the leaves, which are borne on a very short
and bulbiform stem.
In the fossils, on the contrary, the sporangia are borne on a kind of
bracts, or squaniseform leaves united in a spike, which, like those of
Selagindlu, probably terminated the branches.
There is, then, here a singular combination of characters : sporangia
analogous to those of hoUtes, arranged in a spike similar to that of Lyco-
podlmn, but much larger.
The great size of their organs is, indeed, one of the striking charac-
teristics of these spikes. It iigrees with the arborescent habit of Lepido-
dendron, compared with that of the living Lycopodlacece, but it is not on
this account the less reraarkal)le, as the organs of reproduction do not
generally follow the growth of the vegetative organs ;
ferns have not greater sporangia than the smallest species ;
the largest tree-
and, in the
same way, the flowers of our large trees are often smaller than those of
the most humble herbaceous plants.
In these palaeozoic plants the growth has been simultaneous in the
two systems of organs.
Thus, Lepidodeadron, a genus of arborescent Lycopodiacea;, had
spikes of fructification agreeing iu their size with the cones of Firs
and Cedars, containing very large sporangia, rather than with those of
Isoetes, which they resemble in form and structure.
And the question remains to be considered, have the fruits of true
Lepidodeudron, i. e. Lepidostrohns, which have been described by Dr.
J. D. Hooker, only one kind of spores, or has the imperfect state of the
specimens prevented the true nature of the spores contained in the
lower sporangia of the spike from being ascertained ? The form of the*
spores of Lqndosti'obus diff"ers so much from those of the microspores
of Triplosporites as to induce me to consider these plants as belonging
to different genera, and that the genus Triplosporites of Eobert Brown
ought to be retained.
The three known specimens of this fossil do not enable us to esta-
blish its true geological position. The origin of that described by K.
Brown and of the one in the Strasbourg Museum is entirely unknown.
That which I have just described was found in the drift iu a Pyrenean
valley far from tlie formation in which it was originally preserved
;