GENERAL REMARKS ON THE CHINCHONA-PLANTS OF CARAVAYA. 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, 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:— 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 LeguminosÆ, 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, 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 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 My remarks respecting the position of C. Calisaya trees, on the sides of the ravine, only apply to the forest below Lenco-huayccu; 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, Above the zone of the C. ovatas, and nearer the snowy cordillera (for lower down the valley the forests cover the crests of the mountains), commence the open grassy pajonales, which I have already described. Here the formation is exactly the same as that in the valley of Tambopata; and the vegetation of the thickets which fill the gullies, and are interspersed over the grassy glades, consists of huaturus, GaultheriÆ, VacciniÆ, LasiandrÆ, and other MelastomaceÆ, ChinchonÆ, palms, and tree-ferns. The chinchonÆ consist of C. Caravayensis, and of the shrubby variety of C. Calisaya, which is called ychu cascarilla by the natives. The shrub Calisaya ( Josephiana) is generally from six and a half to ten feet high, but I met with an individual plant which I believe to belong to this variety, which had attained a height of eighteen and a half feet; and this inclined me to think, at the time, that this shrubby form could not even be considered as a variety of the normal C. Calisaya, and that its more lowly habit was merely due to the higher elevation and more rigorous climate in which it grew. Dr. Weddell remarks that its appearance varies very much according to the situation in which it grows, I found the shrub Calisaya in flower in the end of April. We crossed two pajonal regions, one above the valley of Sandia, and the other between the valleys of Sandia and Tambopata. The height of the former above the level of the sea was 5422 feet, and of the latter 5600 feet. The time of my visit was the end of April and beginning of May, and I traversed both regions twice, so that an abstract of my meteorological observations will give a tolerably correct idea of the climate at that time of the year; although they only extend over the 25th, 26th, 27th, and 28th of April, and a few days in the middle of May.
In the early morning there were generally masses of white clouds lying in the ravines, and in the afternoon a thick mist drifted across the pajonal, with drizzling rain. The shrub-Calisayas, which were growing plentifully by the roadside, above the valley of Sandia, were entirely exposed, without any shade whatever, and the hill on which they grew had a western aspect. There is a difference in elevation of about 1000 feet between the locality where we saw the shrub-Calisayas, and the region of the normal tree-Calisaya in the Tambopata forests; and the shrubby form is also many leagues nearer the snows of the cordillera. These circumstances are alone sufficient to account for the difference in the habit of these two forms of C. Calisaya; and there seems to be no doubt that the barks of the shrubby varieties of chinchonÆ are specially good when their stunted growth is owing to the altitude of the locality. Our collection of chinchona-plants in the Tambopata forests, and on the pajonales, was completed on May 14th, as follows:—
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