820 



C. SKOTTSBERG 



Fig. 5. Badly eroded slopes in Valle Colonial, Masatierra. Left El Yunque, in centre Pico Central 

 behind this peak Cerro Piramide. In foreground to left a carpet of Acaena argentea. 



Photo 30 3 1917. 



subject to intense erosion (Figs. 5 and 32), the products of weathering are con- 

 stantly carried down by running water, after a downpour in the mountains the 

 streams overflow with muddy water, and a wide reddish fringe along the shores 

 bears witness of the quantities of fine material carried out to sea. Little level 

 ground is found where alluvial deposits are accumulated. Locally the abundant 

 weeds and a few native herbs and grasses, particularly ferns, have stabilized the 

 soil; Acaena argentea and BlecJunini auriciilatiim deserve to be mentioned as forming 

 patches of some extension, but occasionally they are uprooted and carried off. 

 Natural reforestation is not to be thought of. The ridges near the sea on Masa- 

 tierra and the gently sloping table-land of Masafuera between the chasms of the 

 deep quebradas are covered with a more or less natural, xerophilous grass-land, 

 where the thin, sandy or gravelly soil lies bare between the grass-tufts. 



In the inner, wooded parts of the valleys the soil cover is deep, perhaps at 

 least 50 cm, with an A-horizon of dark brown to black vegetable mould, covered 

 with debris and interwoven with roots and rhizomes, and below this layer a yellow 

 to orange-coloured clayey subsoil (B-horizon), which always retains a high percen- 

 tage of moisture. The flat or gently sloping floor of \alleys like V. Ingles, V . 

 Colonial, V. Anson and Rabanal, which is covered with alluvial material washed 

 down from the surrounding ridges, once bore magnificent forest; a profile in 

 the level clearing in Valle Anson, known as Plazoleta del Yunque, shows old 



