3888 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM, 
as trees (instead of bushes) and becoming 4.5 to 6 meters high. Specimens were col- 
lected in flower on June 20, the trees presenting a showy appearance, the deep dark 
blue flowers affording a pleasing contrast. When not in flower the gray foliage blends 
with the desert surroundings and the plants are inconspicuous. The species was 
afterwards noted along the trail from Agua Dulce to Jaragu4y and between Cala- 
mahué and Yubay. Brandegee found it growing as a small tree or bush in the sand 
of dry stream beds at Calamahué. It has also been recorded from Sonora and the 
lower Colorado Valley north of the United States boundary, and thus seems assign- 
able to the Lower Sonoran Zone. 
GERANIACEAE. Cranesbill Family. 
Erodium texanum A. Gray. ALFILERILLA,. 
This, or one or more allied species, grows abundantly in many places, especially on 
sandy or gravelly mesas in the northern half of the Peninsula. At the time of our 
visit the rains of the preceding season had matured a crop which added materially 
to the scanty forage available for our pack and saddle animals. The species presents 
wide variation in size and form, evidently due to local environmental conditions. 
On very dry gravelly slopes tiny upright plants 2 inches or less in height mature 
seed, while along moist sandy arroyos, perhaps only a few feet away, vigorous indi- 
viduals may spread like a mat for several feet over the ground. Watson records this 
species from Dr. Palmer’s collection at Los Angeles Bay on the Gulf coast. 
ZYGOPHYLLACEAE. Caltrop Family. 
Covillea glutinosa (Engelm.) Rydb. CREOSOTE BUSH. 
This is one of the most abundant and widely ranging shrubs in the Peninsula. It 
extends southward from the Colorado Desert along the east side of the Sierra del 
Pinal and the San Pedro Martir mountains, reaching upward through San Matfas 
Pass into Trinidad Valley, while south of the mountains it is abundant from near 
Rosario over the greater part of the Peninsula as far as La Paz. Brandegee records 
the species as far as Todos Santos on the west coast. It was not noted in the Cape 
District south of these points and is absent from the high mountains and the north- 
west coast region. Along the adjacent coast of the Mexican mainland it seems to 
reach its extreme southern limit a few miles south of Guaymas, but on the table- 
lands of the interior it ranges to the southern part of the State of San Luis Potosf. 
It is one of the species which serve best to characterize the Lower Sonoran Zone. 
RUTACEAE. Rue Family. 
Cneoridium dumosum Hook. f. 
This shrub was common at altitudes between 900 and 1,200 meters in the Upper 
Sonoran Zone on the west slope of the San Pedro Mirtir Mountains. A specimen 
still retaining a few ripe fruits was taken above San Antonio, July 28. 
Esenbeckia flava T. S. Brandeg. PALO AMARILLO. 
First seen along our route 5 or 6 miles southwest of El Potrero, where it was taken 
in fruit at about 600 meters altitude on a steep mountain side, October 31. It was 
not noted again until we entered the hills between Agua Colorada and Cerro Colorado 
on our way from Matancita to La Paz. From this point southward to Cape San Lucas 
it was rather common at the lower elevations in the hill country. It is a small tree 
6 to 9 meters in height and is well known to the people in the Cape District as “palo 
amarillo,” a name applied farther north to Adenostoma sparsifolium. 
