Fossil plants, Vol. 1 : $b [A text-book] for students of botany and geologySeward, A. C. (Albert Charles)
Science
Fossil plants, Vol. 1 : $b [A text-book] for students of botany and geology
Seward, A. C. (Albert Charles)
Paleobotany
This species was founded on specimens from the Wealden beds of
Sussex[443], but numerous examples of Chara ‘fruits’ and stems have
long been known from the uppermost Jurassic rocks of the Dorset coast
and the Isle of Wight, which may probably be included in this species.
These fossil Charas are abundant[444] in the Chert beds of Purbeck age
seen in the cliffs near Swanage. Pieces of corticated stems from this
locality are represented in fig. 45 _A_ and _B_.
The cortical cells surrounding a large internodal cell are very clearly
seen in the section shown in fig. 45 _B_, and in the longitudinal view
in fig. 45 _A_. The resemblance of these specimens to the stems of
recent Stoneworts is very striking.
[Illustration: FIG. 47. _Chara Knowltoni_, Sew. × 30.]
The single oogonium of fig. 47 was found in the Wealden beds near
Hastings.
3. _Chara Wrighti_, Forbes. Fig. 46, _d_ and _e_.
This species is characterised by globular or somewhat elliptical
oogonia, with six or seven spiral bands.
It is very abundant in the Lower Headon beds of Hordwell Cliffs on the
Hampshire coast[445]. Various species of _Chara_ are commonly met with
in the Oligocene beds of the Isle of Wight and Hampshire, as well as
in the Paris basin beds, and elsewhere. Well preserved ‘fruits’ and
stem fragments are met with in a siliceous rock of Upper Oligocene age
imported from Montmorency in the Paris basin, and used as a stone for
grinding phosphates at some chemical works near Upware, a few miles
from Cambridge.
Many other species of fossil Charas are known from various horizons
and localities, but the above examples suffice as illustrative types.
In Post-Tertiary deposits masses of _Chara_ and plant fragments
occasionally occur forming blocks of Travertine. Examples of such Chara
beds have been recorded by Sharpe from Northampton[446], by Lyell[447]
from Forfarshire, and by other writers from several other districts.
Beds of calcareous marl are occasionally seen as whitish streaks in the
peat of the Fenland[448]; these often consist in great part of Charas.
A season’s growth of _Chara_ in a shallow lake or mere in the Fens may
appear as a white line in a section of peaty and other material which
has been formed on the site of old pools or lakes.
The recognition of specific characters in the isolated Chara ‘fruits’
usually met with in a fossil state is exceedingly unsatisfactory; the
features usually relied on in the living species are not preserved, and
great care should be taken in the separation of the various forms.
CHAPTER VIII.
BRYOPHYTA (Muscineae).
I. HEPATICAE (Liverworts). II. MUSCI (Mosses).
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