336 NOTES OF A BOTANIST 



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 (Sa/ix Hiunboldtiana\ noticeable for 

 their slender branches and long, narrow, yellow -green leaves, 

 contrasting strongly with the dark green of the spreading Guavas 

 (Ingje sp.), and with the bright green foliage (passing to rose at 

 the tips of the branches) of the Mango (Mangifera indica). 

 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. Twice 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 



