Notes of a naturalist in South America. Ball John
had been one of extreme difficulty. In some of the valleys heavy rains had washed away tracks and carried away bridges, and he had been driven back to seek a passage by some other route. About one-half of his train of mules with their loads had been carried away by torrents, or otherwise lost; but our buoyant countryman, now virtually arrived at his journey’s end, seemed to think the experiment a fairly successful one. He had received no news from England since the beginning of the previous November, so that one or two newspapers five weeks old were eagerly accepted.
The return journey from Chicla to Lima was easy and agreeable, but offered little of special interest. I noticed a curious illustration of the effects of the sea-breeze on vegetation even at a distance of thirty or forty miles from the coast. As we descended, I observed that the acacias which abound in the middle zone of the valley were densely covered with masses of the white flowers of a climbing Mikania, quite masking the natural aspect of the shrub. I thought it strange that this appearance should not have struck me while on my way ascending the valley. On closer attention, I saw that the Mikania was entirely confined to the eastern side of the acacia, so that the same shrub, looked at from the western side, showed no trace either of the leaves or flowers of the visitor. On reaching the Lima station, I was kindly greeted by Mr. Nation, who at once relieved my most pressing anxiety by telling me that I should find two reams of filtering paper awaiting me at my hotel.
CLIMATE OF THE PERUVIAN ANDES.
Having given in the twenty-second volume of the Journal of the Linnæan Society a list of the plants collected during my excursion in the Cordillera, it is needless to overload these pages with technical names, and I shall content myself with a few general remarks on the vegetation of this region, amidst which I passed a brief period of constantly renewed admiration and delight. In the first place, the general character of the flora of Chicla differed altogether from my anticipations, for the simple reason that the climate is completely different from what might, under ordinary conditions, be expected. I had seen reason to conjecture that, in ascending from the Pacific coast to the Cordillera, the rate of diminution of mean temperature would be less considerable than in most other parts of the world, but I was no way prepared to find it so slight as it really is. During the time of my visit, the mean temperature at Lima, 448 feet above the sea, was very nearly 70°, while the annual mean appears to be 66·6° Fahr.9 The mean temperature at Chicla at the same season was estimated by me at 54°, with a maximum of 65·7°, and a minimum of 42°, and the first figure probably approximates to the annual mean. For a difference in height of 11,774 feet this would give an average fall of 1° Fahr. for 935 feet of elevation, or 1 °Cent. for 512 metres; whereas, as is well known,10 the ordinary estimate found in physical treatises, resulting chiefly from the observations of Humboldt, would give for Equatorial America a fall of 1° Fahr. for about 328 English feet of increased altitude, or 1 °Cent. for 180 metres. This rate of decrease would give a fall of 36·6° Fahr. in ascending from Lima to Chicla, whereas, as we have seen, the difference is probably little more than one-third, certainly less than one-half, of that amount. It is, therefore, with some astonishment that the stranger, arriving in this region of the Cordillera, finds himself amidst a vegetation characteristic of the Temperate zone,11 and that many of the most conspicuous species are such as in mid-Europe require the protection of a greenhouse. Amongst the more attractive and characteristic of the Andean flora, I may mention five species of Calceolaria, Alonsoa, two fine Loasaceæ (one with large deep orange flowers and stiff hairs that penetrate the gloves, the other a climber with yellow flowers), several bushy Solanaceæ, and a beautiful clematis, which may hereafter adorn European gardens.
Along with many types of vegetation peculiar to the Andes, or more or less widely diffused throughout the Western continent, it was very interesting to a botanist from Europe to find so large a proportion of the indigenous plants belong to types which characterize the mountain vegetation of our continent. Of the genera in which the plants collected by me are to be classed, fully one-half belong to this category, and these genera include more than an equal proportion of species. I find, indeed, that fully sixty per cent. of the species in my collection belong to European genera, but that, with trifling exceptions, the species are distinct and confined to the Andean region. The reasonable conclusion is that the types which are thus common to distant regions must be of very great antiquity, and that the ancestors of the existing species must have spread widely at a very remote period of the world’s history. Most of the plants in question belong to genera having very numerous species, of which it may be presumed that the parent forms possessed a strong tendency to variation.
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