290 SHREVE: ACROSS THE SONORAN DESERT 
Franseria dumosa, Simmondsia californica, Abutilon palmert, 
Sebastiania pavoniana, Acalypha adenostachya, Euphorbia to- 
mentulosa, Franseria deltoidea, Solanum sp., Abutilon sonorae, 
and Horsfordia alata. 
After descending the slope to within 10 miles of the Gulf the 
vegetation becomes much poorer and more open. Prosopis, 
Olneya, Covillea, and Fouguiera are the most abundant of the 
larger plants. Pachycereus is much smaller and less abundant, 
and the only other cacti are the infrequent individuals of 
Echinocactus Lecontei and Opuntia gosseliniana 
The Bay of Libertad is a slight concavity in the coast line, 
stretching from Punto Lobos on the north to Punto Kino on 
the south, a distance of about 12 miles. There isa slight escarp- 
ment, of from 10 to 20 ft. along the entire coastline of the bay. 
The soil is a coarse loam except for a distance of about two miles 
just north of Punto Kino, where a belt of sand stretches for 
several miles inland. The surface of this area is stable and well 
covered with vegetation. Within half a mile of the escarpment 
the vegetation is very sparse, consisting of a few low individuals 
of Covillea and Prosopis, and occasional plants of Ptiloria 
pauciflora, Frankinia Palmeri, and Psorobatus megacarpus. Here 
also is to be found an interesting species of the night-blooming 
cactus, Wilcoxia, in which the storage organs are numerous 
enlarged portions of the root system resembling small sweet 
potatoes. Over 70 of these enlargements were taken from a 
single plant. 
At Punto Kino a low range of granitic hills abuts directly on 
the coast. To the south the mountainous outline of Tiburon 
Island is plainly seen standing well out into the Gulf, and suc- 
cessive ranges of hills end in abrupt seaward slopes along the 
entire coast as far as Tiburon Island. Across the Gulf it is 
possible to make out the low outlines of Angel Guardia Island 
and to see the profile of the hills of Lower California, culminating 
in the San Pedro Martir Mountains. During the five days that 
we were within sight of the Gulf there was no evidence of human 
existence detected on its waters. 
In sandy soil at the base of the outwash slopes which stretch 
north from the mountains at Punto Kino was found the heaviest 
stand of Pachycereus noted on the entire trip, accompanied by 
large and numerous examples of Elaphrium microphyllum. 
