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 === CHAPTER XVII. JOURNEY FROM THE FORESTS OF TAMBOPATA TO THE PORT OF ISLAY. Establishment of the plants in Wardian cases.