The Geologist/Volume 5/Some Fossil Fruits from the Chalk
THE GEOLOGIST.
JANUARY 1862.
SOME FOSSIL FRUITS FROM THE CHALK.
We are not ashamed to confess our ignorance when we meet with anything we do not understand. On the contrary, we regard such confessions as one of the roads to knowledge; and we always wished it to be one of the features of this magazine that matters not understood should be brought before the world in its pages. We set the example ourselves in the most prominent part of our journal—its opening pages.
Few things are so little understood as fossil vegetables, and least of all are fossil fruits.
Fig. 1.
Some new species from the lower chalk of Rochester have just been added to the national collection in the British Museum, and we lay our drawings of them before our readers with the frank admission that we do not know what they are, and we ask as frankly for information or suggestions.
Some indeed, such as the coffee-like berries, fig-like fruits, and nipadites of the London Clay, carry in themselves the palpable evidence of the classes to which they belong; but there are many specimens from other rocks remaining undescribed in many a collector's cabinet from the want of the ability to give anything like a reasonable suggestion as to what they were, and often, indeed, from the sheer incapacity to assign to them even any probable affinities.
And there they will lie and rot, possibly, if their owners are not bold enough to confess their ignorance and ask for information. For them our pages offer a means of inquiry which they do not possess for us. Anonymously they can ask their questions; openly we must ask ours. These chalk fruits puzzle us, we confess it. Not because we could not soon find some fruits like them in outward form and shape, but because we really do not understand their mode of preservation. Any one can see from our drawings (Plate I., and woodcut, fig. 1) that, flattened as they now are, such flattening is due to pressure in the substance of the rock, and that originally they were round in form. As they are preserved, they are roundish lumps of chalk enveloped in a dark brown ochreous skin.
A superficial observer might look upon this ochreous skin as the real rind of the fruit, but these fruit-masses are perforated by large teredines (see woodcut, fig. 1), as if the central part of the fruit had been of a solid nut-like character, such as we see in the vegetable ivory.
And yet, if this were so,—and teredines bore we know only in hard substances,—how is it that the central solid part has all rotted away, and its place been supplanted with the same soft calcareous chalk as the stratum in which the fossils were imbedded, while the more tender skin only is preserved?
In the same beds of chalk with the fruits, there are not uncommonly to be met with fragments of fossil wood, reduced likewise to thin skin-like ochreous layers, and bored too, through and through, by teredos. These not only show the rotting away of the solid fibrous wood, but also its reduction to the film-like state in which we see it spread on the surface of the chalk. But these wood-fragments might have lain on the still, slowly accumulating surface of the cretaceous ocean-bottom, and have rotted down to their last pellicle in the ponderous lapse of time. Not so the fruits: they, if solid, have been hollowed out to their shells and then filled in. Whether these fruits and other vegetable remains in the chalk be so rare as has been thought, I somewhat doubt. I have myself collected fragments of fossils from the lower chalk of Dover and of Maidstone, which I believe, since I have seen these specimens, to have been fruits like them—and some few of these I think are still in the Folkestone collection—but in all cases the specimens seem to have suffered much decomposition from long-continued immersion before they were completely imbedded.
Here then, at the very outset, we are met with a difficulty which must be surmounted before we can compare with any usefulness these relics of the arborescent vegetation of the far-distant Cretaceous age with the fruits of any living class of trees. There are some in the botanical collection in Kew Gardens which present many points of similarity, but we should by no means be inclined to say of identity. The greatest mischief to fossil botany has arisen from the fact that many, if not most of our fossil species, have been named and described by men who were not botanists; and as so little is known of the vegetable remains preserved in the English chalk, we refrain from giving, and should hesitate long before we assigned, botanical characters to any new form from that formation, especially when so vaguely preserved as those before us.
We would however suggest that the film-like character of the ochreous envelopes of these fossils may be thus explained:—Supposing the fruits to have been solid nuts contained in a husk like the nipadites,—and in the cases of the British Museum there are fine specimens of nipadites from the middle eocene of Brussels, well riddled with teredines; the same is well known to be the case with the nipadites and other nut-like fruits of the London clay,—while the nuts were in the earliest stage of decay, a film of sulphuret of iron was deposited in the empty interspace between the nut and its outer husk, forming thus, when solidified, a thin metallic paper-like pellicle or case, having on its interior surface the impression of the exterior surface of the kernel, and on its exterior surface that of the interior of the husk. The fruit and husk might both then wholly decay away, and leave this metallic shell to be imbedded and filled in by the natural deposition of the cretaceous mud. Thus it will be desirable in searching for further specimens to look carefully for, and to preserve any fragments of real wood or black charcoal, however small, which may be attached to the inside or outside of the ochreous film, as in these fragments we might get some traces of structure to aid us.
That something like this has taken place seems indicated by the film-like character of such specimens of wood as those we have referred to, in which cases the sulphuret of iron was probably deposited in the fine parting between the wood and the bark. Moreover, the casts of the teredo-holes are covered over with the same film of red oxide of iron, which has resulted from the decomposition at a subsequent period of the sulphuret.
Although we attempt not then to determine their family or genera, we are not doing bad service to science in drawing attention to these fossil cretaceous fruits. The very knowledge of their existence will stimulate other observers to seek for more illustrative examples. What one is defective in, another may possess, and so from one to the other we may gain a general knowledge of the whole organism long before any perfect specimen has been brought to light.
In the present case we submit our plates and figures of these fruits, and leave the honour of naming them open to him who can really tell us What they are.