206 MR. C. REID AND ELEANOR M. REID ON 
On/the Pre-Glacial Flora of Britain. / 
By Сгемехт Reip, F.R.S., F.L.S., and ELEANOR M. Rio, B.Sc. 
(PLATEs 11-15.) 
[Read 20th June, 1907.] 
THE plants living in Britain immediately before the cold of the Glacial Epoch 
have attracted attention for many years. A certain number of species were 
colleeted as far back as 1861 by the Rev. S. W. King. These were deter- 
mined by Heer, and Lyell published his list, amounting to twelve species *. 
A few more were added later on; but in 1877, when the Geological Survey 
commenced the examination of the Norfolk and Suffolk coast, the list was 
still under twenty species. 
In the course of this survey a number of seeds and leaves were collected 
(by C. В.), and this collection, which was mainly determined by Mr. Car- 
ruthers, amounted to nearly thirty species f. Tt is now in the Museum of 
Practical Geology, as is the King collection. This small list was of so much 
interest that after the survey was finished the work was continued during 
holiday visits. A collection of ripe seeds of British plants (so poorly repre- 
sented in recent herbaria) was slowly formed, and the fossil flora gradually 
crept up to fifty-six species in 1890 {, and to seventy-eight in 1899 $. 
The work of the last few years has led to the discovery of so many 
additions to this meagre list, that the time has now arrived for a revision of 
our pre-Glacial flora. This is the more necessary, as on the character of this 
flora depends the geologist’s view of the climatic conditions which then 
prevailed. We want also to take a census of the plants, in order to under- 
stand what amount of change and extermination took place during the forced 
migrations consequent on the cold period which supervened. And, thirdly, 
we should like to know what variation the species have undergone during a 
period of many thousand years. — * 
As regards the certainty of the determinations, it may be as well to say at 
once that in the case of seeds and fruits—and it is on these that we mainly 
rely—there is seldom any doubt in either recent or well-preserved fossil 
specimens. Almost every species that can be distinguished by other 
characters can be distinguished also by the seed alone ; and often the seed 
or fruit, though apparently undescribed, gives better specific characters than 
the whole of the rest of the plant. The cases where there is doubt are 
usually seeds of plants belonging to closely allied species, which give almost 
as much difficulty when we compare the whole plant. Thus we do not 
* í Antiquity of Мап, 4th ed. 1873, p. 256. 
t C. Reid, “Geology of the Country around Cromer,” Mem. Geol. Survey, 1882, 
pp. 62-64. 
Е C. Reid, “ Pliocene Deposits of Britain," Mem. Geol. Survey, 1890. 
$ C. Reid, “The Origin of the British Flora,” 8vo, 1899. 
