ALTITUDINAL DISTRIBUTION OF ORCHIDS. 303 



from those found on the eastern side ; Epidendrum cochleatum and E. radiatum are 

 perhaps the only epiphytal species common to both mountain chains. The moist 

 ravines of Arumbaro shelter Cypripedium irapeanum, which here grows larger than in 

 the vicinity of Jalapa. Other orchids of this region are : Bletia coccinea, B. secunda, 

 B. campanulata, Spiranthes aurantiaca, Eabenaria lactiflora, Oncidium suttoni, 0. 

 galeottianum, Epidendrum viscidum, Malaxis myurus, Maxillaria cucullata, M. varia- 

 bilis, Physosiphon carinatus, and Isochilus linearis. In the State of Jalisco, Bletia 

 reflexa, SchomburgMa galeottiana, and Eabenaria lactiflora occur. Lcelia grandiflora, 

 which belongs to the cold region, occasionally descends into this, for instance in the 

 vicinity of Morelia. 



The beautiful forests and gneissic rocks of Juquila, Zacal tepee, &c, in the State of 

 Oaxaca, furnished a large number of new or interesting orchids ; among others, Epi- 

 dendrum pulchellum, E. ramosum, E. ledifolium, E. oppositifolium, Gongora galeottiana, 

 Lcelia peduncularis, Bletia purpurata, various species of Stanhopea, Malaxis galeottiana, 

 Spiranthes pubens, S. orchioides, Eabenaria adenantha, and Platanthera propinqua. 



3. The Temperate Cactiferous Regions. — The plains of some of the Mexican plateaus, 

 and all the slopes descending into the central plains, are covered with a totally different 

 vegetation from the humid sides of the Cordilleras. The geological nature of the soil, 

 the great rarefaction of the air, the little forest, the enormous radiation from the 

 immense surface, the scarcity of rain and consequent absence of streams, com- 

 bined, account for the almost universal barrenness of these plains and the very marked 

 differences in the vegetation. Orchids are extremely rare, yet various species 

 of Laelia and Spiranthes are scattered here and there. Cactaceae, on the contrary, 

 abound, and are remarkable alike for their singular shapes and their brilliantly coloured 

 flowers. Prosopis dulcis and sundry other spiny Mimoseai cover large areas in the 

 plains of Baxia, Guadalajara, Tepic, Tehuacan, and Oaxaca, while prickly Bromeliacese 

 and formidably armed Agaves constitute nearly the whole of the vegetation of the 

 calcareous and schistose soil of Zimapan, Izmiquilpan, and Mextitlan. 



4. The Cold Regions. — The cold Alpine regions commence at elevations of about 

 7200 to 7500 feet, where there is an intermingling of temperate and alpine forms, but 

 at elevations of from 8850 to 9200 feet the vegetation is more characterized. Various 

 species of Pinus, Qaercus, Arbutus, Arctostaphylos, Pyrola, and Kosacese give the scene 

 quite a special character. 



The cold regions of the cordillera may be divided into three subregions, namely : a 

 lower, from 7550 to 8850; a middle, from 8850 to 10,800, or even to 11,500; and an 

 upper, extending from the latter to the upper limits of phanerogamic vegetation. 



The Lower Cold Region. — The following plants ascend more or less into this region : 

 Choisya ternata, Clethra mexicana, Elaterium floribundum, Lobelia hartwegi, L. persi- 

 cifolia, Siegesbeckia jorullensis, Cerasus capollin, Cotoneaster denticulata, Crataegus 

 pubescens, Spiranthes chloreceformis, S. pubens, Lcelia furfuracea, L. albida, Poly- 



