1920] ' CURRENT LITERATURE 355 



which are common throughout the growing season. One station at 2700 m. 

 gives an annual mean temperature 6.5, with a mean maximum of 13 .4 and a 

 mean minimum of o . i° C. Humidity at all times is low, while wind velocity- 

 is decidedly high and constant. Precipitation as recorded at 2000 m. seems 

 to be irregular and variable, the annual amounts ranging from 20 to 68 cm., 

 occurring principally in the colder months in the form of snow. This deficiency 

 of rainfall, combined with other factors, makes the vegetation not only very 

 scanty, but limited to valleys and slopes which possess streams or seepage 

 water from the glaciers and snowfields. In the absence of mountain lakes 

 aquatic vegetation is scanty, and anything resembling mountain meadows is 

 limited to the stream edges and small alluvial fans. Such grassy associations 

 appear to resemble closely similar alpine areas elsewhere. Related to the 

 alpine meadows are the "high Andean oases/' formed at 3200 to 3600 m., 

 where at the foot of talus or morainal slopes some alluvial soil has accumulated. 

 These oases vary in size, but rarely reach 100 m. in diameter. They are often 

 dominated by the juncaceous Andesia bisexualis 15 to 30 cm. high, forming a 

 thick carpet. 



Trees are absent throughout, and even in the valleys the shrubs do not 

 exceed 2 m. in height. Adesmia pinifolia (a legume) is the most plentiful 

 shrub; while among the others are Ephedra americana andina, Berberis empetri- 

 folia, and Senecio uspallatensis. Opuntia andicola, the only cactus of the 

 region, together with Azorella Gilliesii and Laretia acaulis, two umbellifers. 

 form a curious trio of herbaceous cushion plants confined to the valleys. 



Upon the more exposed parts of the mountains there is a notable abundance 

 of prostrate, tufted, rosette, and cushion plants, often with a striking develop- 

 ment of large woody roots. These growth forms are accounted for as being 

 a response to exposure to high winds and dependence upon a subterranean 

 water supply. Upon the slopes Adesmia trijuga, with shrubby cushions 

 30 cm. high, together with Poa chilensis and Stipa speciosa in tufts, dominate 

 the area, forming scattered dots over the rocky landscape. Most abundant 

 upon the summits between 3000 and 4000 m. are the subterranean woody 

 cushions of Adesmia subterranea, whose leaves form a carpet upon the surface. 

 Accompanying this species with similar growth forms are the more uncommon 

 Verbena uniflora and Oxalis bryoides. 



The entire vascular flora consists of 417 species, including one pteridophyte, 

 Cystopteris fragilis, and one gymnosperm, Ephedra. Among the richest 

 families are Compositae with 85 species, Leguminosae with 36 1 Gramineae 

 with 34, Cruciferae with 28, Portulacaceae with 15, Umbelliferae with 15, 

 Rosaceae with 12, Cyperaceae with 12, Oxalidaceae with 10, and Yiolaceae 

 and Caryophyllaceae with 9 species each. Large genera are Senecio with 

 26 species, Adesmia with 16, Calandrinia with 15, Astragalus with 12, Oxalis 

 with 10, and Viola with 9 species. The scarcity of the Saxifragaceae, with 

 two rare species, and the entire absence of the Ericaceae and Primulaceae are 

 worthy of note. Lichens, abundant at the lower altitudes, become very rare 



