578 Part IV. Chapter 3. 
day sun, and the lowest elevation at which this species occurs is 6,970 feet. Elsewhere the same 
rings of trees is noticeable. North and west of Black River Pinus ponderosa prefers the 
tern and southern slopes, but in the watershed tributary to Eagle Creek and Blue River its 
re appear to be reversed, and it is found principally on the slopes facing the north; in fact 
it is found where Pseudotsuga Douglasii and Abies concolor would naturally be expected. 
noticeable feature in regard to the timber es of the San Francisco, the Mogollon 
and the Black ranges in New Mexico is the striking ee ofthe different species, 
On the San Francisco and Tularosa ranges the heaviest growth of mixed timber stands on the 
north-facing hillsides, while the southern ones are practically nn being given up to scrub 
owths of small oaks and pifion pine, Pinus edulis. On the Mogollon Mountains the alpine 
species appear in their heaviest growth on the eastern slope, while on the Black range they are 
only found on the western slope.. On the Mogollon Mountains the yellow pine ascends the 
western slope of the range very nearly to the summit, while on the east slope it does not reach 
within 500 feet. On the Black Range the conditions are reversed. The main cause of this strik- 
ing difference is that each range has a gradual incline to the Gila River, the one to the east, 
the other to the west, and this gradual slope is naturally the more humid, and as humidity is 
an absolute necessity for the prolific growth of alpine species, wherever the slopes are steep, 
alpine species become reduced in number and disappear, and are replaced by more arid types 
such as oak, juniper and piion pine 
The components of this forest and the pifion timber belt in Arizona 
are: Pinus ponderosa, Picea Engelmanni, Pinus strobiformis, Pseudotsuga Dou- 
glasii, Abies concolor, Pinus flexilis, Picea Engelmanni var. franciscana, Funi- 
EN 
perus pachyphloea, Fiss trichocarpa, P. tremuloides, Quercus Gambel, 
O. Emoryi, Cupressus arizonica, Alnus rhombifolia, Platanus racemosa mentioned 
in the order of their importance. 
The low mountains south of the central range of Arizona are clothed 
with a different forest vegetation than that about San Francisco Peak, forming 
scarcely one per cent of the forest area. They are properly to be considered 
as included in the Mexican phytogeographic province and will be treated in 
connection with the Mexican flora. It may be well to briefly refer to the 
peculiarities of their flora at this point. The mountain summits show the pre 
sence of Pinus Ponderosa, a tree of extensive range. Below this pine groW | 
Pinus edulis, P. cembroides (a southern tree) and Oxercus undulata. — he 
Chiricahua Mountains’) have in the spruce belt Picea Engelmannt, Pins 
ponderosa, below which in the fir belt are ?. arizonica, Abies concolor, while 
in the pine belt occur ?. chihkuakuana (entirely unknown north of the Santa 
Catalina Mountains) P. Mayriana and P. cembroides. Here two species of pine 
come together: P. Rexrzilis (northern) and P. strobiformis (southern). ART 
8000 feet (2440 m) on these mountains we find the well-shaded northern slope& 
covered with a forest of Pinus strobiformis, Pseudotsuga Douglasii and Abies 
concolor associated with which are the heavy gold-crowned tussocks of Dugal- 
dea Hoopesii, Senecio eremophilus, Solidago Bigelovii and Helianthella guin- 
quenervis arizonica, while of smaller size near the cool ground are found 
Cerastium Bram, Fragaria bracteata, Lathyrus graminifolius, Aphyllon 
ı) BLUNER, ]. c.: On the plant Geography of the Chiricahua Mountains. Science neW set. 3 
XXX: 720—724 
Da PETE ” Se se Z 
