178 EEIATION BETWEEN CLIMATE AND VEGETATION 



knotted trunks and covered with round black fruit : this forest 

 was followed by another of a very peculiar aspect, owing to the 

 great number of short thick-stemmed Palms which grow in it.* 



On the 25th I reached Piray, in the province of Cordil- 

 lera, which is bounded on the south by the forest of Eugenia, 

 alt-eady mentioned. The country between Piray and the 

 Rio Pilcomayo is inhabited by the Cliiriguanos, who speak 

 Guarani. The Rio Piray, which flows to the south of the vil- 

 lage or Pueblo of the same name, is perfectly impassable in the 

 rainy season, although when I crossed it the water was not knee- 

 deep. Such is the character of the streams of this country ; 

 shallow and quiet or even dry in the hot weather, they swell, in a 

 moment after a heavy rain, into furious torrents which it would 

 be madness to think of crossing. Two leagues from Piray are 

 the village and river of Florida ; and 6 leagues further, at the 

 edge of a pretty wood, is the Pueblo of Cabe^as, which is sepa- 

 rated by a sandy plain 4 leagues in extent, from Abapo, beyond 

 which I, for the second time, crossed the Rio Grande. This 

 river, descending from the Andes of Cochabamba, encloses in an 

 immense bend a large portion of the department of Santa- 

 Cruz, which probably owes its sandy soil to successive deposits 

 from it. 



It was not far beyond the Rio Grande that I found the species 

 of Quinquina which I afterwards named Cinchona australis, 

 because it marks the southern limit of this interesting genus. 

 The mountains on which it grows are composed of a quartzy and 

 iron sandstone, covered in some points with violet schistoid clay. 

 Further on 1 skirted the mysterious lake of Opamon, the water 

 of which is salt, smells strongly of Sea-weed, and is coloured 

 dark green by some microscopical Algae, the only plants that 

 can live in it. 



Beyond this lake the road dives into a thick forest of Coper- 

 nicias (Carandai) with a swampy soil, and then runs along 

 narrow tracts of Pampas, bounded on each side by small wooded 

 mountains, and dotted here and there with groups of Mimosas 

 and Nightsliades. On the 2nd of December I arrived at Gu- 

 tierres, tlie capital (there are only some half dozen huts) of the 

 province of Cordillera. The forests in this neighbourhood are 

 not at all like the magnificent ones of Brazil ; one might imagine 

 oneself quite out of the torrid zone. Amongst the most interest- 

 ing of the trees, and one which is found throughout the region of 

 the Andes, is the Quina-quina {Myroxylon Peruiferum), with a 

 dark red wood, smelling like balsam, from the bark of which 



* This tree, called Motacu in Bolivia, bears the name of Acuri in Matto- 

 Grosso and the province of Goyaz. 



