1833.] THE CARDOOX. 119 



when grazed by cattle, changes into common pasture land. I 

 am not botanist enough to say whether the change here is owing 

 to the introduction of new species, to the altered growth of the 

 same, or to a difference in their proportional numbers. Azara 

 has also observed with astonishment this change : he is likewise 

 much perplexed by the immediate appearance of plants not oc- 

 curring in the neighbourhood, on the borders of any track that 

 leads to a newly-constructed hovel. In another part he says,* 

 " ces chevaux (sauvages) ont la manie de preferer les chemins, 

 et le bord des routes pour deposer leurs excremens, dont on trouve 

 des monceaux dans ces endroits." Does this not partly explain 

 the .circumstance? We thus have lines of richly-manured land 

 serving as channels of communication across wide districts. 



Xear the Guardia we find the southern limit of two European 

 plants, now become extraordinarily common. The fennel in 

 great profusion covers the ditch-banks in the neighbourhood of 

 Buenos Ayres, Monte Video, and other towns. But the cardoon 

 (Cynara cardunculus)']' has a far wider range : it occurs in these 

 latitudes on both sides of the Cordillera, across the continent. 

 I saw it in unfrequented spots in Chile, Entre Rios, and Banda 

 Oriental. In the latter country alone, 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 

 undulating 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 any case is on record of an invasion on so grand 

 a scale of one plant over the aborigines. As I have already 

 said, I nowhere saw the cardoon south of the Salado ; but it is 



* Azara's Voyage, vol. 5. p. 373. 



f M. A. d'Orbigny (vol. i. p. 474) says that the cardoon and artichoke are 

 both found wild. Dr. Hooker (Botanical Magazine, vol. Iv. p. 2862), has 

 described a variety of the Cynara from this part of South America under 

 the name of inermis. He states that botanists are now generally agreed that 

 the cardoon and the artichoke are varieties of one plant. I may add, that an 

 intelligent farmer assured me that he had observed in a deserted garden 

 some artichokes changing into the common cardoon. Dr. Hooker believes 

 that Head's vivid description of the thistle of the Pampas applies to the car- 

 doon ; but this is a mistake. Captain Head referred to the plant, which I 

 have mentioned a few lines lower down, under the title of giant thistle 

 Whether it is a true thistle, I do not know ; but it is quite different from tlif 

 cardoon ; and more like a thistle properly so called. 



