662 Part IV. Chapter 6. 
to mingle with the oaks; yet the latter still predominate and constitute the bulk of the forest. 
Such oaks as Quercus lanceolata, Q. laurifolia, Q. glabrata mingle with Ostrya, Tilia, Salix and 
Cornus. Above 7,000 feet, the oaks are gradually replaced by pines and elevations of 8—10,000 feet, 
such species as, Quercus spicata, Q. reticulata, Q. chrysophylla and Q. pulchella are found scat- 
tered among the pines. 
In this forest region with a temperature of 70° and favored by the long rainy season, the 
richest vegetation of Mexico exists and orchids reach their maximum with some two or three 
hundred species, some terrestrial, but mostly epiphytal?). At 4,000 feet, according to my obser- 
vations, I found forest trees the limbs of which had been broken off by the weight of epiphytes 
consisting of Epidendrums (E, virens), Tillandsias, Cereus triamgularis, Phyllocactus grandis, Poly- 
podium aureum and others. At San Antonio, Huatusco and San Bartolome, oaks reach their 
highest development, not only in the number of species but also in their size. Associated here 
with the oaks, grow trees of the orders Lauraceae, Myrtaceae, Anacardiaceae and Anonaceae with 
an undergrowth consisting of tree ferns, Lygodium, Zamia and species of Citrosma, Acacia, Mimosa, 
Yucca, Triumfetta, Jatropha, Croton, Magnolia, Symplocos, Aralia and Aesculus. Liquidambar 
styraciflua has a very definitely defined vertical area Iying between 3,500 and 5,500 feet. Platanus 
mexicanus only grows by running water at 4,500 to 5,500 feet at the upper limit of the tropie 
forest. a. umbellatum climbs into the trees, according to my observations at Orizaba. 
midst of these forests of tall trees, belonging to the families Leguminosae, RT 
FERNE Meliaceae, according to H. GALEOTTI?), are found growing as epiphytes Stanhopea 
tigrina, S. saccata, Maxillaria (Lycaste) aromatica, Epidendrum ancipticaulon, E. rigidum, E. Can- 
dollei, Pleurothallis microphylla, Oncidium ._— O. stramineum, Coelia Baueriana, Galeottia 
(Zygopetalum) grandiflora and Ponera striat 
The tropic forest in Yucatan is not extensive. HEILPRIN?) found near 
Sitilpech on the Camino Real to Valladolid a forest of tropic luxuriance. The 
large trees /nga xylocarpa and others of it are decked with orchids and epi- 
phytes among which are species of Epidendrum, Cattleya, Tillandsia, Cereus, 
Oncidium. Among other components of the vegetation may be mentioned 
Yucca, Furcraea, Cereus grandiflorus, C. flagelliformis associated with C. 
peruvianus and other species in dense and impenetrable thickets. 
Palm Forest Formation. About Rascon on the Tampico branch of the 
Mexican Central railroad, according to my observations occurs an almost pure 
formation of a fan palm Erythea edulis (see Fig. 32), forty to fifty feet tall 
and covering many square miles of level country and mountain ridges, in 
places associated with a tall and flexuous species of bamboo. Alternating with 
these palm forests are open meadows, which lead back between hills whose 
sides are grassy glades and whose summits are covered with oaks. The 
country is intersected by rivers along which are swamps, meadows, river jungles 
in endless succession, unexplored by the botanist and unknown. 
Central American Regions. 
The following region is a distinct one, for the reason that phytogeographi- 
cally it stands intermediate between the South American phytogeographic 
ı) Hemstev, W. B.: Biologia Centrali-Americana. Botany 
IV: 
2) Ramırez, Dr. Jose: La Vegetacion de Mexico. 1899. Pages RE where the details 
of the orchid distribution in Mexico are given. 
3) HEıLprın, A.: Flora of northern Yucatan: see Bibliogr. p. 83. 
