ALTITUDINAL DISTEIBUTION OF OECHIDS. 305 



A host of beautiful orchids inhabit the forests of Mechoacan, especially around 

 Morelia, in the Cerro de Quinzeo, in the woods of Jesus del Monte, Irapeo, &c, among 

 them Spiranthes cinnabarina, Habenaria acutiflora, Malaxis galeottiana, and Epiden- 

 drum puniceum, as well as nearly all of those described by La Llave and Lexarza. 



The forests of the cold regions bordering the central plateau also shelter a few 

 orchids, including Govenia superba, Corallorhiza mexicana, and Pleurothallis violaeea. 



The Upper Cold Begion.— Phanerogamic vegetation reaches the summits of the loftiest 

 mountains. The heights of Popocatapetl, Iztaccihuatl, Toluca, Orizaba, and Cofre de 

 Perote, ranging between 10,800 and 13,600 feet, constitute a cold region of a very 

 special character, where Filices, Gentianaceae, Kanunculaceae, Grammes?, and Coniferae 

 predominate. At altitudes of 12,100 to 12,800 feet alders and oaks cease, and pines 

 become stunted and shrubby, trailing their branches on the ground. On the peak of 

 Orizaba, at about 13,600 feet, junipers form here and there small patches of verdure 

 on the trachytic rocks ; but at this altitude vegetation has become very poor and 

 scanty, for it is only on the margin of the rivulets, fed from the eternal snows above, 

 that one finds a few diminutive Umbelliferae, species of Cnicus, Senecio, Gentianaceae, 

 Vacrinium geminiflorum, Allium fragrans, Carex galeottiana, Bromus subalpinus, Poa 

 conglomerata, and Beyeuxia orizabce. 



On the small flats of volcanic sand at the foot of the glaciers, from 13,800 to 14,100 

 feet in altitude, grow dwarf species of Castilleja with orange-scarlet flowers, two 

 species of Composita?, two species of Cruciferae, and Bromus lividus ; and cryptogams 

 abound, especially lichens, covering the rocks, and running up to the limits of the snow, 

 which varies at different points. 



The orchids reaching the greatest elevations are : Habenaria prasina, Platanthera 

 nubigena, Spiranthes ochracea, Malaxis gracilis, and Platanthera longifolia, which do 

 not altogether cease below 12,500 to 12,800 feet on the peak of Orizaba. 



Odontoglossum nebulosum and Cattleya citrina live on the tall oaks of the Cerro de 

 Capulapam and the peak of San Andres at altitudes exceeding 10,500 feet, and they 

 are doubtless the only epiphytal species that ascend to so great an elevation in Mexico. 

 Odontoglossum membranaceum, Oncidium graminifolium, Epidendrum virgatum, E. 

 varicosum, E. puniceum, Govenia superba, and G. spicata disappear at about 9850 feet. 

 On looking back and re-examining the comparative distribution of orchids in the 

 three great regions defined, it will be apparent that the cold region is little behind 

 the temperate region, either in the variety or beauty of species peculiar to it. 



