WCP2440

[1]

28, Jermyn St.

London, S.W.

15 Jan[uary] 1891

Dear Mr Mitten

I must thank you most heartily for the trouble you have taken with the fragmentary mosses from Beeston. Did I not send a few dry specimens at the same time? — these were from other localities &, I think, included some from the Cromer Forest-bed.¹

The Beeston mosses seem to belong to an arctic or sub-arctic flora, and correspond in this respect with the flowering plant (Salix polaris, Betula nana, Tanacetum vulgaris, Isoetes lacustris, etc)

We are arriving at one important result in these researches in later Tertiary Botany — that in nature plants do not become acclimatised. The [2] various climatic changes, extending over long periods of time, seem to have driven the plants north or south, without allowing them to adapt themselves to the changed conditions. During the glacial period the temperate flora of the Cromer Forest-bed seems to have entirely disappeared, to be reintroduced when the climate again became genial. The pre-glacial flora of the Cromer Forest-bed is almost identical with that now inhabiting Britain, though between the two must be intercalated the arctic floras of Beeston & of Hoxne, respectively belonging to the commencement & to the close of the glacial period.

I hope we shall be able to obtain some more mosses from the Cromer Forest-bed, but at present I cannot find a good moss-bed [3] on this horizon, & we only know the 3 species from Pakefield determined by you.

The fossils from Balcombe are most probably worm castings. If they were plants or castings of mollusca we should expect them to be either carbonaceous or crushed quite flat. But your specimens are slightly flattened cylinders, such as would be left by worms that fed on mud or sand containing only a small proportion of organic matter. The apparent branching of a few of the specimens is probably deceptive and due not to the cohesion of two cylinders.

In a lacustrine deposit such as the Wealden we should expect worms to be very abundant, but all trace of these soft-bodied animals has now disappeared & we have only the castings & tubes. In your larger specimens at least one of these [4] vertical tubes is still preserved.

Mysterious marking of this sort are very abudant in most shoal-water deposits even as far back as the Cambrian, but naturally the study of extinct soft-bodied animals that have left no trace except their droppings is very difficult. The purely inorganic droppings, like those you send, are generally referred to annelids; but we have others full of organic fragments, such as fish bones, which are probably dropped by fish; & I have seen some made of calcareous sand which I expect belonged to Holothurians.

Yours faithfully | Clement Reid [signature] ²

W Mitten Esq^re A L.S.