314 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
the determinations of Mr. Shaw, typical P. cembroides is widely distributed on the 
Mexican mainland, but is known on the Peninsula only from the Sierra de la Laguna,! 
which it therefore must have reached from the opposite side of the Gulf of California. 
In these mountains we found it growing abundantly in the Upper Sonoran Zone 
above about 1,500 meters elevation, usually taking the form of a much branched, 
widely spreading tree 9 to 18 meters in height and 30 to 60 cm. in diameter at base. 
A specimen was taken at La Laguna, near the summit of the mountains, January 26, 
The species had previously been collected by Brandegee in the same vicinity. 
Pinus edulis Engelm. PINYON, 
A nut pine collected by us at 1,800 meters altitude near Rancho Santo Tomas, on 
the west slope of the San Pedro Mértir mountains has been referred by Mr. Shaw to 
edulis, 
Pinus quadrifolia Parl. PARRY PINYON, 
This is the abundant species of pinyon on the western and northern slopes of the 
San Pedro Martir mountains and extends southward along the Rosarito Divide to 
the cliffs about Matomi, the extreme southern limit of the conifers in this range. 
On the northwestern basal slopes of the San Pedro Mértir mountains and outlying 
foothills considerable forests of these pinyons occur. This is the main nut pine of 
the Indians, one of whose old camp sites we found at Piién. 
The distribution of the pinyons, or nut pines, in northern Lower California is imper- 
fectly known. Whether two or more forms occur together or have separate and well- 
defined ranges was not determined by us. The pinyon taken at Hanson Laguna 
has been referred by Mr. Shaw to P. parryana. None were seen in the coast region 
near Ensenada, but on the Sierra del Pinal they form a scattered growth over the 
western slopes above about 1,620 meters altitude and down to 1,350 meters on the 
east slope. A few were also seen on the rocky, rolling plains 15 miles east of El Alamo 
and at San Matfas Spring. Pinyons were noted at a number of localities along the 
western side of the San Pedro Miartir mountains, where they apparently extend 
rather sparingly in a horizontal belt, reaching from about 990 to 1,500 meters (depend- 
ing upon the slope exposure) and up to about 1,950 meters along the open ridges. 
They extend through San Matfas Pass and along the north side of Windy Canyon; 
on the east slope of the mountains a few were noted as low as 900 meters altitude, 
From this low elevation on the east side'a few scattering individuals range up to 
2,700 meters on the warm, dry slopes facing the Gulf of California and unaffected 
by the cooler, more humid climate of the west slope. 
Pinus monophylla Torr. & Frem. SINGLE-LEAF PINYON, 
Edmund Heller reported this from the east slope of the Sierra del Pinal, east of 
Laguna Hanson, below 1,350 meters. Further work will probably show that it has 
a much more extended range in this region. 
Pinus contorta Doug. LONGPOLE PINE. PLATE 104, B. 
Not known to occur in Mexico except on the upper slopes of the San Pedro Martir 
mountains. It grows on the western side above about 2,400 meters altitude and is 
one of the few forest trees representing the Canadian Zone in these mountains. At 
Vallecitos, where specimens were taken, we found it the most common pine border- 
ing open-mountain meadows. On the rough slopes it is associated with the yellow 
pine. The tree attains a height here of 22 to 30 meters or more, with straight stem 
* Sierra de la Laguna is the name of the high northern section of the Victoria Moun- 
tains, 
