الفهرس 
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Abstract
The family Zygophyllaceae is a cosmopolitan family, represented by 25 genera and about 250 species distributed all over the world. It contains many important desert plants and has significant variations within its genera. Accordingly, the family is divided into five subfamilies in all the taxonomic systems; Larreoideae, Morkillioideae, Seetzenioideae, Tribuloideae and Zygophylloideae. Members of the Zygophyllaceae include trees, shrubs, and herbs that are often jointed at the nodes. The leaves are usually opposite, 2-ranked, and evenly pinnately compound. They usually have stipules and are often resinous. The genus Zygophyllum (about 100 species), the largest genus in subfamily Zygophilloideae, is found from northern and southern Africa to Central Asia, India, and Australia. While the genus Fagonia (30 - 40 species) is widespread in warm deserts of North and South America, the Canary Islands, the Mediterranean and Saharo-sindian regions, southwestern Africa, and southwestern Asia to northwestern India (Paul, 2014). Porter (1963) states that ″Fagonia is a genus known from the warm arid regions of all continents except Australia″. In Libya the family comprises eight genera and twenty five species (Feng et al., 2013). One of the important genera belonging to this family is Fagonia. The genus comprises twelve species growing in different phytogeographical regions in Libya (Abdul Ghafoor, 1977).
The taxonomy of Fagonia is very difficult mainly due to a high degree of morphological plasticity and thereby adaptations to climatic conditions (Zohary, 1972 and Danin, 1996). Ozenda and Quézel (1956) grouped the North African Fagonia species into four natural groups; which can be considered as sections according to Melbourne System of Nomenclature (2012); according to vegetative morphological characters: (1) F. kahirina-cretica-flamandii group, (2) F. arabica-bruguieri group, (3) F. glutinosa-latifolia group, and (4) F. microphylla- group. However, Batanouny and Batanouny (1970) and El Hadidi (1966 a) described 18 species of Fagonia and constructed an artificial key for their identification. The latter author classified the Fagonia species in Egypt into three groups. These groups are summarized in table 1.
Also, El-Hadidi (1972 b and 1974 a) classified Fagonia species into complexes according to morphological variations. Beier et al. (2004) studied the phylogenetic relationships within genus Fagonia based on trnL and its DNA sequences and they did not support the natural groups of Fagonia, and showed that all species from the Old World, except Fagonia cretica form a weakly supported clade. Fahn and Shimony (1996) described the glandular hairs and secretory cells covering the leave of three Fagonia species grown in Jerusalem, F.mollis var. hispida, F.glutinosa and F.arabica Abdel Khalik and Hassan (2012) investigated seed and trichome morphology of Fagonia in Egypt and indicated that the seed and trichome morphology are useful in distinguishing the species and not supporting the natural groups. The results of the previous works confirmed that all species of Fagonia form a well-distinguished group, characterized by several characteristics: obconical fruit shape, smooth seed architecture, non-winged mericarp edge, ovoid seed shape, filament length (3 - 7 mm), seed size (1.8 - 4.2 x 1.3 - 3.7 mm), subprolate to prolate pollen shape, 1-3-foliolate leaf and glandular hair shapes. Within this group, we can show that Fagonia arabica, F. bruguieri, F.sinaica, F.latifolia, and F.scabra form a subgroup; F.cretica forms a subgroup and another one includes.