442 BOTANICAL GEOGRAPHY. 



pp. 241. Paris, 1845, 4 to) ; as regards the earlier sys- 

 tematic parts of this illustrated work (t. ii), see the Ann. 

 Rep. for 1840-1. 



JBoissier's excellent account includes the coast-terraces between Gibraltar 

 and Almeria, towards the centre of the country as far as the elevated sur- 

 faces of Andalusia, and thus entirely includes the highest mountain-chains 

 of the south of Spain. Along the entire coast-line a series of isolated moun- 

 tain-chains, consisting of marmoraceous limestone, arise directly, in almost 

 every case, without any intervening land, the western extremity always 

 ascending highest, whilst towards the east the ridge gradually falls : to this 

 system belong the Serrania de Honda (6000') 3 Sierra Tejeda (6600'), and 

 Sierra Gador (7000'). These chains, which run parallel with the coast, may 

 be considered as forming the southern mountain-border of the Spanish pla- 

 teau ; for its northern foot, at an elevation of from 2000' to 2500', passes 

 directly into the elevated plain of Honda, the Vega in Granada, or the great 

 plains of Guadix and Baza. In a line from Ducal to Almeria, not far from 

 Granada, the chain of the Sierra Nevada, twenty-two leagues only in length, 

 is inserted between the boundary chain and the elevated plain ; it is nearly 

 twice their altitude, but narrow, its highest summits ascending to an elevation 

 of 11,000'. In fact, the passes in the western portion are not situated below 

 9500', whilst toward the east the mean height of the crest appears to dimi- 

 nish to 6000'. The Sierra Nevada is mainly composed of mica-slate, but on 

 its flanks secondary and tertiary formations have been carried up with it as 

 far as an altitude of 6000'. The district of Alpujarra forms an important 

 constituent of these mountains ; it includes the longitudinal valley running 

 between the coast-chain S. Contraviesa and the Sierra Nevada, together with 

 the southern, intersecting valleys of the latter. The following are some 

 of the heights which were measured by Boissier with the barometer : The 

 city of Honda, on the plateau, 2300'; Granada, 2200'; Sierra Nevada, the 

 farm of San Geronimo, 5064'; Col de Vacares, 9472'; Picacho de Veleta, 

 10,728'; Mulahacen, 10,980'. 



Four botanical districts, which Boissier distinguished in South Granada, 

 yielded him vascular 1900 plants, which he is inclined to regard as forming 

 three fourths of all the indigenous plants of this district. The author con- 

 siders the following as among the general characters of the flora viz. that 

 many forms cover the soil in gregarious condition, and that the south of 

 Spain contains more thorny plants than any other country in Europe, and 

 hence resembles the steppes of Western Asia, although the families which de- 

 velope the thorns are not the same. The hot region (region chaude) comprises 

 the coast declivity up to a level of 2000'. Intense atmospheric precipitations 

 fall during October and November ; the vernal rainy season, which is less 

 regular, lasts from February to March, sometimes until April ; uninterrupted 

 drought prevails from April to the end of September. Thus the dry season 



