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XI. On the Origin and Distribution of the British Flora.
With an Appendix on the River-basins of Essex as
Natural-history Provinces.
By Professor G. S. Boulger, F.L.S., F.G.S.
[Read at the Field Meeting held at Danbury, August 13th, 1881.]
Last week will be memorable in the annals of British
botanical science. Ten days ago I stood by the open grave
of Hewett Watson, who devoted the genius and labour of his
life to the elucidation of the geographical relations of British
plants ; and two days later appeared the eighth edition of
Professor Babington's Manual,—a work that, in its critical
discrimination of allied forms, has during the last thirty-
eight years ably reflected the advance of Botany in England.
The work of these two men is related to the two divisions
of the subject on which I am about to address you. First, I
wish to trace the origin of our flora by comparing it with
other assemblages of plants; and secondly, I wish to sketch
the distribution of its constituents through the British Isles.
The most unobservant traveller cannot fail to notice the
difference between the plants of one district and those of
another. If it may not have fallen to his lot to contrast the
luxuriance of a tropical jungle with the barren tundras of
Arctic Siberia, or the pastures of our temperate plains with
the pine forests of Scandinavian mountain-slopes, or the
stunted birches and willows of their summits, he will have
seen near his own home that the flowers of the field are not
those of the wood, and that those of the sea-shore are not
those of the river-banks.
Such experience leads us all at first to put down the
distribution of plants as the effect of differences of climate—
using the word in a broad sense; nor can it be denied that
climate is a most important factor in the problem. You will,