CHAPTER XVI. GENERAL REMARKS ON THE CHINCHONA-PLANTS OF THE range of my observations in the chinchona-forests extended for a distance of forty miles along the western side of the ravine of Tambopata, and one day's journey on the eastern side. This region is covered, with few exceptions, from the banks of the river to the summits of the mountain-peaks, by a dense tropical forest. The formation is everywhere, as I have before said, an unfossiliferous, micaceous, slightly ferruginous, metamorphic clay-slate, with veins of quartz, and the streams all contain more or less gold-dust. When exposed to the weather this clay-slate quickly turns to a sticky yellow mud,1 and lower down it is very brittle, and easily breaks off in thin layers. The soil formed by the disintegration of the rock, mixed with decayed vegetable matter, is a heavy yellowish brown loam, but there is very little of it on the rocky sides of the ravine, and no depth of soil except on the few level spaces and gentle slopes near the banks of the river. Mr. Forbes, in speaking of the extensive range of Silurian formation, of which the Tambopata hills form a part, attributes the frequent occurrence of veins of auriferous quartz, usually associated with iron pyrites, to the proximity of granite, whence they have been injected into the Silurian slates. In the cooling and solidification of granite the quartz is the last mineral element to crystallize and become solid, and he suggests that, during the cooling, the conse Hence the name Lenco-huayccu. Lenqui is anything sticky in Quichua, and huayccu a ravine. quent expansion due to the crystallization of the constituents has forced the quartz and gold, still fluid, into the fissures of the neighbouring rocks, and so formed the auriferous quartz veins. These are only developed in the slate rocks, which, when such veins occur, must be at no great distance from granitic eruptions, either visible, or such as may be inferred to exist.2 The chinchona forests which I examined in the Tambopata valley are between lat. 13° and 12° 30' S. The elevation above the sea, on the banks of the river, is 4200 feet, while the loftiest crests of the mountains which overhang it on either side attain an elevation of about 5000 feet. In the preceding chapter I have given a general idea of the nature of the climate throughout the year, and my stay was too short to enable me to give any more detailed information for most of the months; but I did not fail to take careful observations while I remained in the valley, which will give an accurate idea of the climate during the month of May. During the fourteen first days of May the results were as follows: 2 Quarterly Journal of the Geological Society, Feb. 1, 1860, p. 59. The wind generally blows up the valley during the daytime, when the clouds ascend, to be condensed by the colder night-air. Thus we almost invariably had rain at night, generally in a heavy fall, but occasionally in small drizzle, which usually continued until the forenoon. At noon it cleared up for a fine afternoon, and only on two occasions did we have rain throughout the day. The valley, and the course of the river, bear N.N.W. and S.S.E. The three valuable species of chinchonæ found in Tambopata grow in distinct zones as regards elevation, together with other chinchonaceous plants, up the declivitous sides of the ravine. From the banks of the river to about 400 feet up the mountains, the forest consists of bamboos, several genera of palms, tree-ferns, paccays, and other Leguminosa, Lasionemas, Cascarilla Caruas, and the Chinchona micrantha, together with the chinchonaceous tree called by Martinez Huiñapu. This is the lower zone. The C. micrantha, called by Martinez verde paltaya and motosolo,3 was in flower in May. I met with it constantly in moist low places; and several trees, with their very large ovate leaves, and bunches of white fragrant flowers, were actually drooped over the waters of the river. It produces a good quality of bark, and I collected seven fine seedling-plants of this species. 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, Melastomacea, Aceite de Maria (Elæagia Maria), 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 3 Dr. Weddell believes it to be a distinct species from the C. Micrantha of Huanuco, and has named it C. Affinis. 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 lacinia, 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, a 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. My remarks respecting the position of C. Calisaya trees, on the sides of the ravine, only apply to the forest below Lencohuayccu; above that position they are not found so high up the sides of the mountains, probably owing to their greater proximity to the snowy region of the cordillera. The nearest snow may be about forty miles from Lenco-huayccu, as the crow flies. I also found that the Calisaya fina was most abundant about the Yana-mayu, while the variety called morada was plentiful in the upper part of the ravine. But it was very difficult for an unpractised eye to detect the slightest difference between these two varieties, until their leaves were placed side by side, when that of the morada appeared to be just a shade darker green. Dr. Weddell has, in his work, named the Calisaya morada, as a distinct species, C. Boliviana, but I understand that he is now of opinion that it is scarcely more than a variety of the Calisaya vera, its bark being very generally collected and sold as that of the latter. No plants which I saw in the forests could be compared, for vigour and regularity of growth, with the tree which I have already described as having been planted on the edge of a clearing; and I think this tends to prove that plenty of light and air is essential to the vigorous growth of the C. Calisaya, so long as there is a sufficient supply of moisture, and protection from the direct rays of a scorching sun for the first year or two. The C. Calisaya is undoubtedly the most delicate and sensitive of all the species of chinchona. Above the region occupied by C. Calisayas, in the forests, is the third or upper zone, from 600 to 800 feet above the river. Here, amidst very dense humid vegetation, covered with ferns and mosses, are first met the trees of C. pubescens, |