466 BOTANICAL GEOGRAPHY. 



of the south of Europe, they ascend far above the limit of perpetual snow. 

 Here the drying influence of the plateau, which lies far below the forests, is 

 removed by the masses of snow; not so, however, in Thibet, where the 

 country corresponding to the plateau ascends to the snow-line. On the 

 mountains of North America, as on the south side of the Alps, sufficient 

 water is thawed in summer from the large fields of snow to irrigate the 

 elevated forests : thus they are provided with a permanent source of moisture ; 

 even when the prairies are without rain for months, they never dry up, 

 whilst upon Pindus and the Apennines the winter snow soon disappears ; 

 whilst in Thibet the melted snow upon the elevated surface evaporates again, 

 without fertilizing the soil. 



In a botanical appendix to Duflot de Mofras' work 

 upon the western coast of North America (Exploration 

 du Territoire de 1'Oregon, &c., 2 vols. 8vo. Paris, 1844), 

 a list of about 300 Calif ornian plants is given. It is, 

 however, derived from old sources, and is disfigured by 

 errors of the press to such an extent as to be rendered 

 almost useless. 



In the work itself we find the following statements regarding the course of 

 the seasons in California : 1. In Upper California, e. g. in the latitude of 

 St. Francisco (38 N.), the rainy season, with prevailing south-east winds, 

 lasts from October to March. From April to September north-west winds 

 blow ; it then never rains, although fogs are common on the coast ; the soil 

 also then loses its verdure (ii, p. 46). On account of the length of the 

 drought, the total amount of the atmospheric precipitations is less than in 

 the south of Europe. 2. The vegetating season of the arid western coast of 

 Lower California, however (30 to 23 N. lat.), occurs with its atmospheric 

 precipitations during the summer (i, p. 239). 3. On the eastern coast of 

 this peninsula, at Cape Lucas, in the Gulf of California (mer vermeille), and 

 on the north-west coast of Mexico we find an inversion of the trade-wind, 

 (inversion d'alize, i, p. 171), as south-westerly or westerly winds predominate 

 there. In Mazatlan (23 12') the rainy season coincides with south-westerly 

 and westerly, and the dry season with north-westerly winds (i, p. 172) ; the 

 same is the case at St. Lucas, where these latter monsoons prevail from No- 

 vember to May (i, p. 229). Within the gulf, where, although it is beyond 

 the tropic, the monsoons are the same, the amount of rain appears to diminish 

 very considerably. We cannot imagine anything more miserable and 

 neglected than these two coasts, which lie waste from a deficiency of water 

 (i, p. 205). 



I find a notice of Plantse Lindheimerianse, by Gray, 

 which probably contains an account of Lindheimer's 



