336 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
tom of Windy Canyon to 1,080 meters altitude near San Matfas Pass. It is associ- 
ated with many Lower Sonoran plants and seems to belong in the list of species 
characteristic of this zone, but it represents a genus mainly tropical in distribu- 
tion. In northeastern Lower California it grows 4.5 to 7.5 meters high. Like other 
species of the genus it is commonly called “palo verde,’ a name derived from the 
smooth, greenish bark. 
Cercidium peninsulare Rose. PALO VERDE. PALO DE PGA. PLATE 114, 
The type of this species was taken by the present writer on the open plain near 
La Paz April 16, 1899, then in flower. It isabundant throughout the Cape District south 
of La Paz except on the upper slopes of the mountains and reaches northward to an 
undetermined limit, its range overlapping or so continuous with that of torreyanum 
that we did not distinguish between them. The species was collected by Dr. J. N. 
Rose in the spring of 1911 at various places in the Cape District and on Carmen and 
Cerralvo islands. Where forage for stock is scarce, especially in the extremely arid 
central desert region, the branches of palo verde trees are lopped and the tips and 
leaves are eaten by mules with apparent relish. Although generally known as “palo 
verde,”’ this tree is also called locally “palo de pta.” It is generally distributed 
over rocky hills and sandy deserts, but is usually more abundant along dry washes. 
During the dry season and droughts the trees are nearly or quite bare, but leaves 
appear in a remarkably short time after even a single local shower. In places the 
appearance of the palo verde trees showed a sharp line of demarcation between the 
area recently visited by rain and that over which drought still prevailed. The 
abundance of this species in the Cape District and its association with so many tropical 
plants seem to place it with the tropical element, to which most members of the 
genus Cercidium belong. 
Haematoxylon boreale 8. Wats. Brasit. Pato DE Brasit. Loawoop. 
The “Brasil,” or “palo de Brasil,”’ as it is called by the people, was common at 
the lower elevations along our route in the Cape District south of La Paz. It grows 
as a scrubby tree 4.5 to 7.5 meters in height. The trunks of the older trees may be 
very thick at the base, but are usually hollow and have deeply fluted bark. We 
did not find the species used asa dyewood. Specimens with ripe seed pods were taken 
between Tres Pachitas and Valle Flojo, December 25, 1905, and in flower between 
San Pedro and La Paz, February 1, 1906. Brandegee records the species from La 
Paz, Todos Santos, and San José del Cabo. 
Hoffmanseggia microphylla Torr. 
At San Felipe this species is quite common in sandy places along the Gulf shore. 
It grows asa shrub 1 to 1.5 metershigh. At the time of our visit, June 20, it was nearly. 
leafless, but bearing flowers and fruit. Recorded by Brandegee from Calamahué. 
Parkinsonia aculeata LL. RETAMA. 
This species has a wide range in Mexico, extending southward from near the south- 
ern border of the United States within the limits of the Lower Sonoran Zone. It 
occupies the greater part of Lower California, but is absent on the high mountains and 
in the northwest coast region. Specimens were collected at Agua Dulce, 30 miles 
southeast of San Fernando, in September, 1905. The species was noted by Bran- 
degee from San Gregorio to Calamahué and San Fernando. It was also collected 
at La Paz by Doctor Rose in June, 1897. 
Parkinsonia microphylla Torr. RETAMA, 
The range assigned this species by Sudworth comprises adjoining portions of the 
desert region in southern California, southern Arizona, northeastern Lower Califor- 
