CHAPTER XVI.

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,[342] 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 consequent 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.[343] 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:-- Mean temperature 69-5/6° Fahr. " " at 7 A.M. 68 " " at 3 P.M. 71-1/2 " " at 9 P.M. 69 Mean minimum in the night 62-5/7 Highest temperature observed 75 Lowest " " 56 Entire range 19 Mean variation in the 24 hours 10-1/3 Greatest " " 15 Least " " 6 Mean of the dew-point 61-4/5 } " " at 7 A.M. 61.9 } Dry bulb " " at 3 P.M. 62.5 } as above. " " at 9 P.M. 60.9 } 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_,[344] 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_, _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. 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_, and _Pimentelia glomerata_, and a little higher up are numerous trees of the two valuable species of _C. ovata_, namely, α _vulgaris_ and β _rufinervis_, with very large ovate leaves, the latter being distinguishable by the deep red of the leaf-veins. The _Cascarilla bullata_ grows with them, and extends still higher up the sides of the mountains. The bark of the β _rufinervis_ variety is habitually used to adulterate the Calisaya, which it very closely resembles, and is called _zamba morada_ by the cascarilleros, while the α _vulgaris_ variety is known as _morada ordinaria_. Martinez said that the _zamba morada_ was very tenacious of life, and that, having once thrown away a branch amongst some moss, he found it a fortnight afterwards, still throwing out shoots. Both varieties of _C. ovata_ yield valuable barks. 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_ (β _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, and that the colour and texture of the different parts change according to the amount of exposure. 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. Mean temperature 59° Fahr. Mean minimum at night 52 Highest temperature observed 67 Lowest " " 49 Entire range 18 Mean of the dew-point 53.6 (dry bulb as above). 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:-- No. of Plants. _C. Calisaya_ (_calisaya fina_) 237 _C. Boliviana_ (_calisaya morada_) 185 _C. ovata, var. α vulgaris_ (_zamba ordinaria_) 9 _C. ovata, var. β rufinervis_ (_zamba morada_) 16 _C. micrantha_ (_verde paltaya_) 7 _C. Calisaya, var. β Josephiana_ (_ychu cascarilla_) 75 --- Total 529 ===