GEOGRAPHICAL DISTRIBUTION OF PLANTS. 569 



innocuous when tended by the skill and industry of man. Upon herbaceous and 

 flowering plants, the influence of cultivation is not less conspicuous. Different kinds of 

 cabbage savoy, broccoli, arid cauliflower, are supposed to be derived from a plant which 

 is sometimes found growing wild on our coasts, the Brassica oleracea ; the clove, pink, and 

 the carnation, are varieties of a flower found among the ruins of some of our old castles, 

 the Dianthus Caryophyllus ; and the polyanthus is probably a derivation from the wild 

 primrose. It is observed, however, that the primitive structure of plants never changes, 

 however cultivated and far transported. The potato grown in Chili at the height of 

 twelve thousand feet above the level of the sea is identical with the potato of Siberia. 



Involuntarily, man contributes largely to the propagation and dispersion of plants, 

 some of which are useless to him, or positively noxious. Their seeds become mixed 

 with the bales of merchandise which he transports, and with the ballast of ships, and are 

 thus conveyed to a distance from their place of growth, accidental circumstances leading 

 to their germination. De Candolle states, that at the gate of Montpellier there is a 

 meadow set apart for the purpose of drying foreign wool after it has been washed ; and 

 that scarcely a year passes without some foreign plants being found naturalised in this 

 drying ground, as Centaurea parviflora> Psoralea palcestina, and Hypericum crispum. 

 There is a remarkable instance in South America of a European plant, which was pro- 

 bably introduced by accident, soon after the first colonists of La Plata landed in the year 

 1535, which has now taken such entire possession of a large district, as to have obli- 

 terated nearly the whole of the spontaneous vegetation. This is a species of thistle, 

 Cynara Cardunculus, or cardoon, of the artichoke kind. In the Banda Oriental, remarks 

 Mr. Darwin, " very many, probably several hundred square miles, are covered by one 

 mass of these prickly plants, and are impenetrable by man or beast. Over the undu- 

 lating plains, where these great beds occur, nothing else can now live. Before their 

 introduction, however, the surface must have supported, as in other parts, a rank 

 herbage. I doubt whether there is any case on record of an invasion on so grand a scale 

 of one plant over the aborigines." Mr. Hinds is tempted to inquire, from its rifeness 

 and luxuriance, whether plants may not find a situation more favourable to their exist- 

 ence than that in which Nature has placed them, a question which the excessive 

 development of this stranger, as well as that of Psidium pyriferum at Tahiti, a species 

 of exotic guava, would seem to require an affirmative answer. The cardoon must not be 

 confounded with the giant thistle of the Pampas, so vividly described by Captain Plead, 

 from which it is essentially different. Fennel, another importation from Europe, has 

 widely spread itself in the same region, covering the banks of the ditches in the 

 neighbourhood of Buenos Ayres and Monte Video. In like manner, the common 

 English nettle speedily grew up in New England after the first colonists settled in the 

 district. 



When we consider the condition of the vegetable kingdom, and the operation of the 

 preceding agencies, it is impossible to resist the conclusion, that different species of 

 plants were originally planted by the Creator at several foci on the surface of the earth, 

 many of which have been subsequently widely diffused by the causes enumerated. It 

 has, indeed, been thought, that the occurrence of cryptogamous plants in mines and deep 

 excavations of the earth, presents a case which cannot be explained by any known 

 method of dispersion, and which seems to favour the doctrine of equivocal production. 

 But some striking facts deserve notice, which are calculated to remove the difficulty, by 

 establishing an extensive diffusion of seeds through the soil of the earth, in some 

 instances at a considerable depth, which past geological catastrophes have imbedded, and 

 which preserve their vitality, so as to germinate upon any accidental exposure to the 

 action of the atmosphere. Dr. Prichard gives the following example, upon the authority 



