Innocent: A Century's Changes in the Sheffield Flora. 219 
Salt’s great hunting ground for the rarer hydrophiles was 
Potterick Carr to the South-East of Doncaster, the drainage 
of which has caused the following species to be added to the 
list of extinctions.:— 
Ranunculus lingua. Alisma vanunculotdes. 
Myriophyllum verticillatum. Lemna trisulca. 
Helosciadium tnundatum. Stratiotes alotdes. 
Utricularia vulgaris. Sparganium natans. 
Myrica gale. Isolepis fluitans. 
Ceratophyllum demersum. Carex dioica. 
C. ampullacea. 
These marsh plants may be considered as examples of a 
class of extinctions due to decreased distributional area, and 
this will be most harmful to seed-propagated plants, especially 
annuals; the smaller the relative area the more difficult is 
effective seed dispersal and the continuance of the species, 
and in such a case the wider the seed dispersal of the plant, the 
worse it will be for it. 
The break-down of the old method of agriculture enabled 
the farmers to respond to the demand for corn caused by the 
Napoleonic wars and the increase of population, but the repeal 
of the Corn Laws later led to the decrease of the land under 
corn, and the cornfield weeds, necessarily annuals, suffered 
from this decrease of distribution area, but in addition to this, 
they were growing under cultivation conditions, which involved 
the selection of the seed most free from weeds. It is not sur- 
prising, therefore, that the cornfield weeds form a large group 
of extinctions and decreases as follows; (1) extinctions :— 
Papaver argemone. Linaria elatine. 
Fumaria capreolata. Mentha avvensis. 
Trigonella ovnithopodiotdes. Lamium amplexicaule. 
Bupleurum votundifolium. Galeopsis ochroleuca. 
Caucalis daucotdes. Lithospermum avvense. 
Torilis nodosa. Lolium temulentum. 
and (2) decreases :— 
Ranunculus arvensis. Chrysanthemum segetum. 
Lychnis Githago. Achillea Ptarmica. 
Scleranthus annuus. Bartsia odontites. 
Scandix pecten-veneris. Galeopsis versicolor. 
Centaurea cyanus. Echium vulgare. 
The cornfield weeds which are now found in most abun- 
dance appear to be those which have a much wider range than 
cornfields, merely, such as Corn Spurrey, Scarlet Pimpernel, 
and Climbing Persicaria. 
|Note.—As the discovery of the functions of earth-worms is generally 
ascribed to Darwin, it is worth noting that Miller’s ‘ History of Doncaster,’ 
published a.p. 1804, contains a letter from Gilbert White of Selborne, 
with reference to Potterick Carr, explaining the use of earthworms in 
rendering soil fertile}. 
ro1r June tr. 
