It is also a very important question whether larches, firs, and birch-trees might not be naturalized in the more sheltered ravines of these lofty treeless regions; where large plantations might be formed for the supply of timber and fuel. The Indians are now entirely dependent, for the framework of their roofs, on the crooked poles of the _queñua_ tree (_Polylepis tomentella_); and for fuel on llama's dung and the _tola_ shrubs (_Baccharis_). The winters, from May to September, are not nearly so cold as in Scotland, though very dry; and, during the summer or rainy season, though it is cold, there is plenty of moisture. The introduction of these plantations would change the whole face of the country, and the introducer would confer an inestimable blessing on the inhabitants. I remained for some time at Puno, in order to collect information, and come to a determination respecting the best course to pursue in the performance of the service on which I was employed. The supply of the bark of _Chinchona Calisaya_ trees is now entirely procured from the forests of Munecas, Apollobamba, Yuracares, Larecaja, Inquisivi, Ayopaya, and the _yungus_ of La Paz in Bolivia; but I found that the difficulties in the way of making a collection of plants and seeds in these districts would be very great, and it afterwards turned out that these difficulties would have been insurmountable. As a considerable part of the revenue of Bolivia is derived from the bark trade, which is not the case in Peru, the Bolivians are exceedingly jealous of their monopoly; and the nature of my mission was already suspected. Moreover there was an imminent prospect of a war between Peru and Bolivia; a large army was massed in three divisions--at Puno under General San Roman, at Vilque under Beltran, and at Lampa under Frisancho; and, as soon as hostilities commenced, it would have been next to impossible for a private person to preserve his mules from seizure. This war did not actually take place, but Linares, the President of Bolivia, issued a decree on May 14th prohibiting all traffic, or the passage of travellers, from one country to the other;[145] a decree which was strictly enforced, and which would have rendered it impracticable at that time to have conveyed myself and companion, with laden mules, from Bolivia to the coast, without long delays and detentions. One of the pretexts for this threatened war is perhaps the most extraordinary that has ever been alleged in modern times; namely, that the Bolivian Government persisted in coining and deluging Peru with debased half-dollars. A strange way of settling a financial difficulty!