She gave me a very satisfactory reason why the native vegetable productions of Great Britain are inferior in number to those of countries on the continent; few seeds are furnished with the means of flying across the Channel so as to have naturalised themselves here. Where no sea intervenes, they are gradually but continually spreading from one place to another. On the road sides and in the corn-fields of France, Germany, and Holland, we see many plants which have been imported for our gardens; even in the Flora Danica there are many belonging to that small country, which are not possessed by us; and all the mountainous regions of Europe, though separated by a great distance, have several species in common, while we can boast of very few which are found in Great Britain only.
Miss P. told me, however, of some; for instance, the Isle of Man cabbage has not yet been observed in any other parts of the world than in that island, in the Hebrides, and on the north-western shores of England and Scotland. One of the most interesting of our British plants, she says, is pipewort; for in no part of the continent of Europe is it, or any individual of this genus, to be found; and, what is very remarkable, though all the other species of the family are inhabitants of the tropics, yet ours is found in one of the most northern of the Hebrides, and in a lake which is peculiarly cold.
It is the same among the _cryptogamous_ tribes, such as lichens, fungi, and mosses. Though we think Britain rich in that extensive class, most of them are known in other parts of Europe, or in North America; and she says it is a singular fact, that the lower we descend in the scale of vegetation, the more universally are the individuals of those tribes dispersed over the surface of the globe. In Carolina, for example, a large proportion of the _fungi_ are the same with those of France and Germany, while among what she calls the _phenogamous_ plants, or those which have _visible flowers_, there are scarcely any that are common to Europe.
The _mosses_ too, which have been received from the higher parts of North America, and from Kamtschatka, are almost all indigenous in Europe.
_22nd._--I had often wished to see the contents of a set of nice little drawers under the book-cases on one side of the library; at last, to my great satisfaction, I have been allowed to examine the small geological collection which they contain. It consists of specimens of the different _series_ of rocks, accompanied by the organic remains which distinguish them.