HARTLEPOOL BALLAST HILLS. 805 
presents a completely different aspect, especially that part lying 
west of the ‘Centaurea Calcitrapa.” Here the ground, instead 
of being covered with shrubs or grass, is almost quite bare, the 
plants have not been disturbed by bents or sand, for they are 
inland. They seem rather to have been quietly extinguished, 
but from what cause, I am quite at a loss even to guess. 
I have never been upon any Ballast Hills except those at 
Hartlepool, consequently my personal knowledge is confined to 
very narrow limits. Still, what is true in one case, one would 
naturally conclude, would hold good in others under similar cir- 
cumstances. 
Mr. Edward Mounsey has told me that very few of the plants 
mentioned by Winch, are now to be found upon the Sunderland 
Ballast Hills, which seems to bear out the supposition that none, 
or very few, of these introduced plants are finally naturalized. 
I was first led to make a list of these plants from the idea that 
they would spread themselves into the neighbouring country, and 
become confounded with the truly indigenous flora, but I am 
quite satisfied that such is not the case, and that we need appre- 
hend no danger on that score. 
Of course I do not pretend to say that all the plants do come 
up exactly in the years allotted to them by their affixed numbers. 
But what I do mean is this, that these periods are so distinctly 
marked as to admit of this arrangement, and the practical use of 
such an arrangement is to show the fruitlessness of searching for 
Annuals on old ballast, or for Perennials on that lately thrown 
out. For instance, the vanity of searching for ‘ Papaver 
somniferum”’ or “ Borago officinalis” on seven years old ballast, 
or for “Clematis Vitalba,” or “ Epilobium angustifolium” on 
two years old. 
I know of no better exemplification of the “ struggle for 
existence’”’ than is exhibited on these Ballast Hills. It is inter- 
esting above measure to notice how (¢.g.) “ Mercurialis annua ” is 
swallowed up by “ Diplotaxis,” how ‘“ Reseda lutea,” or “ Glaucitum 
luteum” gives in, after a long fight, to the combined attack of jug- 
wort and grass, and how at last even the sturdy ‘“ Diplotaxis ” is 
punished, for its cruelty to others, by the thick coarse grass. 
