RODENTS OF LIBYA 19 



Phytogeographic Characteristics 



Ozenda summarizes the phytogeographic characteristics of the 

 Saharo-Sindien Floral Region, which includes most of Libya, as fol- 

 lows : 



(1) Great poverty of species (of the nearly 1,500 species of plants 

 present, 1,000 occur in the Sahara). In the Sahara, there are 150 species 

 of vascular plants per 10,000 square kilometers, as opposed to 1,000 to 

 2,000 in an area of comparable size in Europe. In the tropics the num- 

 ber of species increases to 3,000 or 4,000 per 10,000 square kilometers. 



(2) Extreme sparseness of individual plants, the vegetation being 

 thinly scattered. 



(3) Monotony of the country and of the plant groups (one type or 

 species of plant may occupy a vast area). 



(4) Absence of characteristic systematic groups above the genus 

 (there are no families or tribes that are most typical of the Sahara, but 

 several species and genera are typical of the region) . 



(5) The presence of a large number of endemic species. 



(6) Human economy based on the culture of the date palm. 

 Cryptogamic vegetation is relatively sparse in the Sahara and is 



represented by approximately 100 species of mushrooms, lichens, 

 algae, liverworts, and mosses; they comprise approximately 12 to 18 

 percent of the floral composition. Bacteria and filamentous mushrooms 

 have developed even in barren soils which contain no phanerogamic 

 vegetation. 



Systematic Composition 



The Gramineae, Leguminosae, and the Compositae are considered by 

 Ozenda to represent the dominant families of the Sahara. Even though 

 these three families represent about 35 to 40 percent of the floral com- 

 position of the Sahara, they are not the most typical Saharan families. 

 The Chenopodiaceae with two endemic genera, Fredolia Coss. and Dur. 

 and Nucularia Batt. ; the Cruciferae represented by numerous genera 

 and species; and the Zygophyllaceae including the genus Fagonia L., 

 are the most typical families of plants in the Libyan flora. Representa- 

 tives of the latter family are almost nonexistent in the Mediterranean 

 littoral. The Cruciferae and Chenopodiaceae, however, have numerous 

 representatives in the Mediterranean region and the entire Holarctic 

 Floral Empire. 



Generic dominance, with the number of species in each genus of the 

 plants of the northern Sahara, including Libya (Fezzan), is as follows: 

 Astragalus L., 8; Fagonia L., 8; Aristida L., 8; Launaea Cassini, 7; 

 Reseda L., 6; Salsola L., 6; Plantago L., 6; Tamarix L., 5; Euphorbia L., 

 5. These genera belong to the families Gramineae, Leguminosae, Com- 



