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The most notable elements in point of size and form, and the 
plants which fix the attention on approaching the hill are the 
above mentioned cactus, Cereus giganteus, the ocotillo (Fouguteria 
splendens) and the palo verde (Parkinsonia microphylla), so called 
on account of its bare green stems. The distinctly green note 
in the color effect of the hill during the dry season is due to this 
small tree, which here occurs in considerable numbers. 
At the time of my arrival, the giant cactus was at the end of 
its flowering season, and the earlier matured fruits were bursting. 
Fic. 27. Flowers, opened and unopened, of the saguara (Cereus givandeus), 
This plant is certainly one of the most remarkable productions of 
the vegetable kingdom. Consisting of a single columnar green 
shaft, or having a few branches extending outward and upward 
rom a point somewhat below the middle of the main axis, its 
stands with sentinel-like immobility and emphasizes rather than 
abates the weirdness of the desert landscape. ven when as- 
sailed by the storm winds it scarcely nods, while its spines accen- 
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