112 BAHIA BLANCA TO BUENOS AYKES. [CHAP. vi. 



change in the aspect of the country after having crossed the Salado. 

 From a coarse herbage we passed on to a carpet of fine green 

 verdure. I at first attributed this to some change in the nature of 

 the soil, but the inhabitants assured me that here, as well as in 

 Banda Oriental, where there is as great a difference between the 

 country around Monte Video and the thinly-inhabited savannahs 

 of Colonia, the whole was to be attributed to the manuring and 

 "razing of the cattle. Exactly the same fact has been observed in 

 the prairies * of North America, where coarse grass, between five 

 and six feet high, 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 like- 

 wise much perplexed by the immediate appearance of plants not 

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

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

 " 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 cir- 

 cumstance ? "VVe thus have lines of richly manured land serving 

 as channels of communication across wide districts. 



Near 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 : J it occurs in these latitudes 

 on both sides of the Cordillera, across the continent. I saw it in 



* See Mr. Atwater's account of the Prairies, in Silliman's N.A. Journal, 

 vol. i. p. 117. 



t Azara's Voyage, vol. i. p. 373. 



J 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 cardoon ; but this is a mistake. Captain Head referred to 

 the plant, winch 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 the cardoon ; and more like a thistle properly so called. 



