Ancient Plants: Being a Simple Account of the past Vegetation of the Earth and of the Recent Important Discoveries Made in This Realm of NatureStopes, Marie Carmichael
Science
Ancient Plants: Being a Simple Account of the past Vegetation of the Earth and of the Recent Important Discoveries Made in This Realm of Nature
Stopes, Marie Carmichael
Paleobotany
The section shown in fig. 100 is that cut at right angles to that in
which the sporangia are shown in fig. 98, viz. tangential to the axis. A
remarkable feature of the plant is that there were also round those
sporangia which bore the numerous small spores (corresponding to pollen
grains) enclosing integument-like flaps similar to those shown in fig.
100, _sp. f_.
[Illustration: Fig. 100.—Section through one Sporangium of
_Lepidocarpon_
_sp_, Sporophyll; _sp.f._, flaps of sporophyll protecting sporangium;
S, large spore within the sporangium wall _w_; _s_, the three aborted
spores of the tetrad to which S belongs.]
This type of fructification is the nearest approach to seed and pollen
grains reached by any of the Pteridophytes, and its appearance at a time
when the Lycopods were one of the dominant families is suggestive of the
effect that such a position has on the families occupying it, however
lowly they may be. The simple Pteridophyte Lycopods had not only the tall
trunks and solid woody structure of a modern tree, but also a semblance
of its seeds. Whether this line of development ever led on to any of the
higher families is still uncertain. The feeling of most specialists is
that it did not; but there are not wanting men who support the view that
the lycopod affinity evolved in time and entered the ranks of the higher
plants, and indeed there are many points of superficial likeness between
the palæozoic Lycopods and the Coniferæ. Judged from their internal
structure, however, the series through the ferns and Pteridosperms leads
much more convincingly to the seed plants.
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