AMERICAN SYLVICULTURE 



Other species of the zone are Red Spruce, Black Spruce, Balsam-fir, 

 Cotton- woods, Canoe Birch, Hemlock, White Cedar and Tamarack, 

 tlie latter here obtaining its optimum. 



B. The Nortli Mexican forest. 



The North Mexican flora intrudes, coming from Mexico, the 

 states of Arizona and New Mexico. It is small in area, but inter- 

 esting botanically. Forest not possible save at altitudes exceeding 

 5,500 feet. Forest proper — dense forest — but at 8 000 feet. 



I. North Mexican sub-tropical forest. 



Characterized by Cactus, Yucca, Agave and Mosquite (Prosopis). 

 Evergreen Oaks in moist valleys. Madrona (Arbutus), a beautiful 

 tree, on sunny slopes often mixed with Manzanita (Acrostaphyios 

 pungens). 



II. North Mexican forest of the moderately warm zone. 



This zone, very narrow, should contain winter-bald broad-leaved 

 species. The dryness of the soil and of the air, however, does not 

 allow of their occurrence save on moist ground along rivers. West- 

 ern Walnut, Mexican Ash, Poplars and Willows. The Pines are the 

 leading species of the zone, forming huge forests at altitudes ex- 

 ceeding 6,000 feet elevation. Some of these Pines are northern 

 sentinels from Mexico, others outposts from the States. Im- 

 portant is Pinus Chihuahuana, in Mexico largely used for timber, up 

 to 80 feet high, three feet in diameter, three needles. Pinus 

 Arizonica, a five-needled Pine, occurs at 6,000 feet elevation. Pinus 

 reflexa, locally known as White Pine, occupies moist dells at 8,000 

 feet elevation. Nut pines at lesser elevations as low brush, notably 

 Pinus edulis, monophylla, osteosperma. 



C. The Pacific forest. 



Typical difl'erencc from Atlantic forest lies in the relative lack, 

 not in species but in area, of broad-leaved woods. Tropical forest 

 is absent, possibly due to lack of moisture at low elevations in 

 Southern California. 



I. Pacific sub-tropical forest. 



Occupying Southern California. This zone is devoid of deaee 

 forests, the northern edge excepted. Evergreen Oaks, or rather 

 Winter Green Oaks (Pasania densiflora is leafless during dry sum- 

 mer) dot the ground in park-like groves. California Laurel (Um- 

 bellularia calif ornica) is a characteristic tree of this region, grow- 

 ing up to 100 feet high. Impenetrable bush thickets cover hot 

 aspects, formed by Leguminosae, Labiatae, Compositae, Rosaceae, 

 etc. The rare and beautiful Montery Cypress along the seashore. 



