300 APPENDIX. 



ALTITUDINAL DISTRIBUTION OF ORCHIDS IN SOUTH MEXICO, AND 

 THE DOMINATING FEATURES OF THE GENERAL VEGETATION. 



The general distribution of orchids is discussed with some fulness in a preceding 

 paragraph (p. 267) ; and here we propose reviewing the salient features of their 

 distribution in South Mexico, especially in relation to the sequence in which the 

 various types appear in ascending from the coast to their upper limits on the mountain- 

 peaks, and also, briefly, in relation to the characteristic plants with which they are 

 associated in the successive zones. Too much importance must not be attached to the 

 actual heights given, because they greatly vary for the same genera and species, 

 according to situation, aspect, and other local conditions. The data are almost wholly 

 extracted from an article by Richard and Galeotti*, compiled from Galeotti's own 

 observations, supplemented by those of Linden, Ghiesbreght, Hartweg, Andrieux, and 

 other travellers. Their zonal divisions, though perhaps not the best that could be 

 devised, are adopted, as any deviations therefrom would deprive the sketch of much of 

 its value. Metres have been roughly reduced to feet. 



1. The Tropical or Hot Begion. — This is divisible into two subregions. The vegeta- 

 tion covering the slopes of the cordillera from the sea-shore up to an approximate 

 altitude of 3250 feet is tolerably uniform in character. Little else than prickly 

 mimosas, tall grasses, and arboreous bignonias is to be seen, though here and there the 

 burning solitude is relieved by patches of verdure looking like so many oases. From 

 the end of October until June this desolate region is scorched up and almost inanimate. 

 But there is a region within a region in this zone, formed by the numerous ravines 

 which serpentine through the plains, and shelter a rich and varied vegetation. 

 Prominent among the trees are : — Ceeropia, Castilloa elastiea, various species ofBignowia 

 and Zamia, with such orchids as Schomburg&ia tibicinu and various Oncidia having 

 cylindrical fleshy leaves. Even in the small ravines which pierce the dunes near Vera 

 Cruz Mormodes pardina and Chysis aurea grow, hidden in the darkest and most humid 

 localities, whilst the Cyrtopodia attach their long pseudobulbs to the basaltic rocks in 

 the most exposed and sunny situations. The nearer we approach the cordillera the 

 richer are these ravines in interesting and curious plants, the rock varying in composi- 

 tion in different States. Thus in Vera Cruz it is basaltic ; in Tamaulipas calcareous ; 

 and schistose or gneissic in Oaxaca, embellished with dwarf palms of the genus Chamw- 

 dorea ; various ferns, such as Aspidium serra, A. heraeleifolium, Adiantum villosum, 

 Polypodium eordifolium, and Lygodium polymorphum ; Ficus of kinds, Cecropia ; showy 

 Gesneracese, as Gloxinia guttata f , Episcia rosea, and Achimenes grandiflora ; the tall 



* " Monographic des Orchidees Mexicaines, precedee de considerations generates sur la Vegetation du 

 Mexique et sur les diverses stations ou croissent les especes d'Orchidees Mexicaines." Par A. Richard et H. 

 Galeotti. Comptes Rendus des seances de l'Academie des Sciences, xviii. 1844. 



t Some of the names cited in this sketch stand as synonyms in our Enumeration, while a few others 

 chiefly of orchids, given by Richard and Galeotti, have not been connected with their respective species by 

 subsequent botanists. 



