KXHiniTTOX MRETINCJj 1950 
H5 
SPECIMENS OF PLANTS COLLECTED ON THE INTERNATIONAL EXCURSIONS 
TO : — 
i. The Abisko district of Northern Lappland, and 
ii. the Alps, with a diagram to show the route taken. 
A. N. Girra'. 
SPECIMENS FROM THE BURREN, CO. CLARE. F. M. BaRTON. 
3. MAPS. 
MAPS ILI.USTRATING THE SPREAD OF SOME RELATIVELY RECENT ADDITIONS 
TO THE BRITISH AVEED FLORA. 
(These maps, together with specimens of the species con- 
cerned, formed an exhibit which was included in the Temporaiw 
Exhibition ‘Weeds and Weed Control’ held in the Department 
of Botany, National Museum of Wales, Cardiff, May-October 
1950. Exhibited by the courtesy of the Museum.) 
The inaps relate in the main to plants which have come into 
this country since the year 1800, though a few species are in- 
cluded which arrived earlier but did not spread until more 
recently. Each map is tinted so as to show how the species con- 
cerned has spread within the British Isles since the date of its 
arrival or' first record. (The time value of the various tints 
employed varies from one map to another.) 
It was formerly supposed that most iveeds of cultivation were in- 
troduced into this country by man in the course of plant and 
animal husbandry, but many wdld species at present confined 
to fields and waste places are now known to have colonised the 
ground left bare b.y the decay of the ice sheet at the end of the 
last Glacial Period. If, as seems probable, these plants have 
persisted in suitable situations ever since, they must be regarded 
as natives. Doubtless, their numbers have also been .swelled 
in the course of time by other species brought in with grain ; 
this kind of invasion must have begun some 4,000 years ago 
and probably is still going on ; it has been reinforced in the 
neighbourhood of seaports by the former practice of ballasting. 
Until about 1930 or later ships used to arrive in Wales from 
abroad carrying ballast in the form of soil or sand. This 
material was discharged on arrival and dumped at or near the 
port concerned; from the many weed seeds ivhich it contained 
sprang the alien plants still to be found groiving around the 
docks. 
Some of our more recently established weeds have escaped 
from gardens. 
H. A. Hyde & A. E. Wade. 
SELECTED MAPS SHOWING THE DISTRIBUTION OF VARIOUS SPECIES IN THE 
ISLE OF MAN. D. E. Allen. 
