118 PARTICULAR CONSIDERATIONS ON THE 



It is also going somewhat beyond legitimate bounds to assert 

 positively that structure, form, and life are never now-a-days 

 imparted to the insensate elements. It is very true that 

 naturalists do not in general maintain the ancient doctrine of 

 spontaneous, or, as it should rather have been called, non- 

 parental generation. And I must at once admit that, having 

 to look to the authority of others for my data, I do not feel 

 entitled to rest with any confidence on that principle. While 

 protesting, however, against its being supposed indispensably 

 necessary to the present speculation, I may point out some of 

 the difficulties which stand in the way of its being conclu- 

 sively rejected, as well as some experiments which have resulted 

 in its favour. 



It is well known that vegetable life often appears in circum- 

 stances where the presence of seeds must be presumed as in the 

 highest degree unlikely. It is a familiar fact that, on earth 

 being thrown up from a great depth, as the bottom of a mine 

 or well, or on a new surface being formed in any other way, a 

 set of plants not always common in the district invariably 

 springs up at the place. Thus, after the great fire of London 

 in 1666, the entire surface of the destroyed city was covered 

 with such a vast profusion of a species of cruciferous plant, the 

 Sisymbrium iris of Linnaeus, that it was calculated that the 

 whole of the rest of Europe could not contain so many plants 

 of it. White, of Selborne, tells us that when old beech trees are 

 cleared away, the naked ground in a few years becomes clothed 

 with strawberry plants. It is well known that, whenever forest 

 ground is cleared, young trees of a different and complementary 

 nature spring up, and this without the ground being disturbed. 

 A crop of white clover arising from a quantity of lime, where 

 no such seeds were sown, is a familiar phenomenon ; it was 

 tried a few years ago in the centre of a wide moss, many miles 

 from clover crops of all kinds, and with entire success. It is 

 also known that, if a spring of salt water makes its appearance in 

 a spot, at a great distance from the sea, the neighbourhood is 

 soon covered with plants peculiar to a maritime locality, 

 plants which previous to this occurrence were entire strangers 

 to the country. Again, when a lake happens to dry up, the 

 surface is immediately usurped by a vegetation which is 

 entirely peculiar, and quite different from that which flourished 

 on its former banks. When the marshes of Zealand were 

 drained, the Car ex cyperoides was observed in abundance, 

 and it is known that this is not a Danish plant at all, but 

 peculiar to the north of Germany. In a work upon the useful 



