NOTES OF A BOTANIST 
CHAP. 
luxuriance, their ample fronds never mutilated by caterpillars 
as they are wont to be in other regions. On the river- bank 
grow also fine old Willows (Salix Humboldtiaiia)^ noticeable for 
their slender branches and long, narrow, yellow -green leaves, 
contrasting strongly with the dark green of the spreading Guavas 
(Ingae sp.), and with the bright green foliage (passing to rose at 
the tips of the branches) of the Mango {Mangifera iiidica). 
Mingled with these, or in square openings in the Algarrobo 
woods, are cultivated patches of sweet potatoes, yucas, maize, and 
cotton plants, the latter distinguishable by their pale but fresh 
green colour. It was a magnificent sight to look from this cliff 
towards the mouth of the Chira when the sun was just setting 
over it, steeping the hills of Mancora in purple and violet, and 
gilding the fronds of the palms and the salient edges of the 
adjacent cliffs, while the deep recesses of the latter and the 
Algarrobo woods were already shrouded in gloom. 
On descending into the valley, the natural forest of Algarrobo 
is found to occupy a strip of from a few hundred yards to three 
or four miles in width, extending from the river on each side as 
far out as there is permanent moisture at a moderate depth. It 
is divided by fences into plots of various sizes, all private 
property, except a small breadth of common lands adjacent to 
each village, I was surprised to hear these plots called not 
"woods" but "pastures" (potreros), for the trees grow in them 
as thickly as trees do anywhere, and there is not underneath 
them an herb of any kind. They are so called because the fruit 
of the Algarrobo is the main article of food for most of the 
domesticated animals, and therefore corresponds to the pasturage 
of other countries. The Algarrobo is a prickly tree, rarely ex- 
ceeding 40 feet in height, with rugged bark not unlike that of the 
elm, but more tortuous, and with bipinnate foliage like that 
of the Acacias, to which it is closely allied. The roots penetrate 
the soil to only a slight depth, but extend a very long way 
horizontally. On the desert I have seen an Algarrobo root, 
no thicker than the finger, stretch away to a length of 40 yards, 
evidently in quest of moisture. As the trunks never grow 
straight, and soon become tolerably corpulent, and their roots 
take too little hold of the friable earth to sustain them against 
the squally winds, they very generally fall over in age either into 
a reclining posture or quite prostrate, but immediately begin to 
turn their heads upwards, send off new roots from every part of 
the trunk in contact with the soil, and thus get up anew in the 
world ; so that an old potrero or Algarrobo wood has a most 
irregular and fantastic appearance. Tw ice in the year the 
Algarrobo puts forth numerous pendulous racemes of minute 
yellow-green flowers, which nourish multitudes of small flies and 
beetles, that in their turn afford food to flocks of birds — most of 
