From 400 to 600 feet above the river is the middle zone, and that which contains the Calisaya-plants. The vegetation chiefly consists of huge balsam and India-rubber trees, _huaturus_, _Melastomaceæ_, Aceite de Maria (_Elæagia Mariæ_), Compadre de Calisaya (_Gomphosia chlorantha_), and occasional trees of _Cascarilla Carua_, which straggle up from the lower zone. Here the young trees of _C. Calisaya_ grow in great abundance, but the cascarilleros had certainly done their work well in former years, for every single tree of any size had been felled, though many of the young root-shoots were 20 and 30 feet high, and covered with capsule-bearing panicles. These precious trees were most plentiful under the ridges of rock which crop out at intervals, where the ground was not so thickly covered with vegetation, and where the young plants obtained plenty of light and air, while they were partially protected from the direct rays of the sun by the spreading branches of taller trees. The _Calisaya_-trees, on the Ccasa-sani precipice, however, had no shade whatever. They were covered with capsules. I observed that when the young plants of _C. Calisaya_ grew up the sides of the rocks, and actually came in contact, they often threw out roots from their stems or branches. The _C. Calisaya_ is by far the most beautiful tree of these forests. Its leaves are of a dark rich green, smooth and shining, with crimson veins, and a green petiole edged with red, and the deliciously sweet bunches of flowers are white, with rose-coloured laciniæ, edged with white marginal hairs. But it was evident that we did not see them to advantage in these forests; they ran up tall and straggling, as if seeking the sun, and seemed to pant for more light and air, and a deeper and richer soil. Martinez told me that, when the Calisaya is much overshadowed by other trees, it loses the crimson colour on the petioles and veins of the leaves; and that fifteen leagues lower down the river (I suppose at about four thousand feet above the sea) the leaves of the _Calisaya morada_ become quite bright purple all over the under side. Gironda and Martinez told me that there were three kinds of Calisaya-trees; namely, the _Calisaya fina_ (_C. Calisaya, α vera_, Wedd.), the _Calisaya morada_ (_C. Boliviana_, Wedd.), and the tall _Calisaya verde_. They added that the latter was a very large tree, without any red colour in the veins of the leaves, and generally growing far down the valleys, almost in the open plain. A tree of this variety yields six or seven quintals of bark, while the _Calisaya fina_ only yields three or four quintals; and Gironda declared that he had seen one, in the province of Munecas in Bolivia, which had yielded ten quintals of _tabla_ or trunk-bark alone.