الفهرس 
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Abstract
The present study was carried out in Department of Agriculture Botany, Faculty of Agriculture, Ain Shams University. This work aimed to study the morphology and anatomy of two desert plant obtained from Cairo-Suez desert road, Wadi Hagool and Ain El Sokhna coast. For this objective, a survey of the naturally growing plants was made. The survey accounted about 36 species belonging to 35 genera and 20 families. Two medicinal, widely distributed species were chosen, namely, Zygophyllum album (Zygophllaceae ) and Nitraria retusa (Nitrariaceae). These two species were subjected to morphological and anatomical studies. The results obtained from these studies were summarized in the following:
I. Zygophyllum album L.f.
1. Morphology
Z. album is a perennial herb (25-50 cm) gray in color with many succulent branched stems. The leaves are petiolate, bifoliolate and opposite. The petiole and the leaflet are cylindrical or obovoid. The plant produces small solitary, pedicelled, hermaphrodite, symmetrical and pentamerous flowers. The fruit is capsule, 5-lobed with pear-shaped.
2. Anatomy
The root
The old root has the ordinary secondary thickening: the periderm, the pericyclic derivatives and the vascular tissues. There are few druses observed in the parenchyma of functioning or nonfunctioning phloem. Several lignified cells were observed in the nonfunctioning phloem either solitary or in groups of 2 to 8 cells.
The stem
The stem is composed of a uniseriate epidermis with thick cuticle layer and provided with many unicellular 2- armed trichomes and several slightly sunken stomata. The vascular cylinder consists of about ten collateral vascular bundles with different size. The ground tissue differentiates into a wide cortex and a narrow parenchymatous pith. The outermost layers of the cortex is differentiated into photosynthetic layer.Groups of fibers were observed near the phloem intervening the cortical cells. Groups of small cells having one druse in each were shown in both cortex and pith. The old stem has the ordinary secondary growth with its original epidermis and cortex.
The leaf
The leaflet consists of a uniseriate epidermal cells with thick cuticle, sunken stomata and numerous unicellular, biforked trichomes. The mesophyll is centric, differentiated into palisade tissue outwards and water storage parenchyma inwards. A lot of idioblasts with druses were observed intervening the palisade tissue. The vascular tissue of the leaf is differentiated into main central bundle and two small lateral ones embedded in the water storage tissue. In addition, numerous smaller bundles occur on the inner periphery of the palisade tissue or inserted in the innermost palisade layer. The petiole has the same structure of the leaflets.
The flower
The pedicel has a similar structure to that of the young stem. The calyx consists of five free sepals. Each sepal has two uniseriate epidermal cells covered with a many unicellular trichomes enclosing a homogenous mesophyll, traversed by 5-7 small vascular bundles. The corolla consists of five free petals. The petals has two uniseriate epidermal cells and one vascular bundle embedded in parenchymatous ground tissue. The androecium consists of ten winged stamens arranged into two whorles. The winged filament is formed of a uniseriate epidermis, parenchymatous ground tissue and amphicribral vascular bundle in the center. The anther is bilobed and tetrasporangiate. The mature anther contains two large pollen sacs, the pollen grains are spherical in shape. The wall of the mature anther consists of an epidermal layer; endothecium, i.e., subepidermal layer, with secondary wall thickening in the form of strips. The gynoecium consists of five completely united carpels, a single style and one stigma. The ovary has five locuoles with two ovules (or more) in each, the placentation is axial. The ovary has outer epidermis covered with trichomes, the inner epidermis of the locuoles are isodiametric or palisade in shape.
The study of vascularization revealed that each sepal has three traces, one median and two laterals. The median trace diverged directly from the receptacle, as well as the lateral bundles derived from two different receptacular ones. Each petal and the opposite stamen of the outer whorle have the same origin from the receptacle since their origin (strands) ramifies into two traces, one of them penetrates the base of the petal and the outer penetrates the filament of the opposite stamen. While the inner whorle of the stamens has its own origin from five vascular strands migrate from the receptacle and penetrate its filaments. Each carpel has five bundles one dorsal, two laterals and two ventrals.
The nectary is a glandular ten-redged disc arise on the top of the pedicel below the ovary. No special vascular supply for the nectary was observed.
II. Nitraria retusa
1. Morphology
N. retusa is a perennial shrub 1-2 m in length; mound-shaped. Stems are many with spines. The leaves are simple, alternate, petiolate, and obovate to spatulate, fleshy, entire or ending in 3-5 teeth. The flowers are carried in short terminal cymes, pedicellate, actinomorphic, bisexual, pentamerous. Tetramerous flowers were also found. The calyx and petals are free. The androecium has fifteen stamens (twelve in the tetramerous flowers). The gynoecium consists of three-carpellate pistil ending in a single style and three stigmas. The fruit is fleshy drupe and red.
2. Anatomy
The root
The old root has a normal secondary thickening. There are groups of parenchymatous cells which store starch in the phloem. Near the outermost layers of the secondary phloem there is a ring of fibers surrounding the vascular tissues with two cells in width.
The stem
The stem has a uniseriate epidermis covered with thick cuticle, provided with unicellular trichomes and few somewhat sunken stomata. The outer cortical cell layers have many chloroplasts. No supported tissue of any kind was observed in the cortex. The cortex is rich in dark cells contain tannins and mucellage. The innermost cortical layer is differentiated into starch sheath. The vascular cylinder consists of several collateral vascular bundles. The pith is parenchymatous and free of dark cells occurred in the cortex.
The leaf
The leaf consists of two simple epidermises; both of them are uniseriate with thick cuticle provided with unicellular, unbranched trichomes and sunken stomata. The mesophyll is intervened by small vascular bundles and differentiated into palisade tissue toward both surfaces and spongy tissue with many idioblasts cells in between (unifacial leaf). All the veins are embedded in the uppermost spongy layers. The petiole is cylindrical with uniseriate epidermis. The ground tissue is parenchymatous with many ideoblasts. It has one collateral vascular bundle surrounded by two layers of lignified cells. The phloem locates toward the abaxial or surrounds the xylem tissue except the adaxail side.
The flower
The pedicel has a similar structure to that of the young stem. The calyx consists of five free sepals each one has two uniseriate epidermal cell, provided with many unicellular trichomes, few stomata enclosing a homogenous mesophyll, traversed by 5-7 small vascular bundles. The flower has five free petals with cap shape. The petals has two uniseriate epidermal cells with thick cuticle and one vascular bundles embedded in parenchymatous ground tissue. The androecium consists of fifteen stamens arranged into two whorls forming five triplets. The filament is formed of a uniseriate epidermis, parenchymatous ground tissue and amphicribral vascular bundle in the center.The anther is bilobed and tetrasporangiate. The mature anther contains two large sacs, the pollen grains are spherical in shape. The wall of the mature anther consists of an epidermal layer, endothecium, i.e., a subepidermal layer, with secondary wall thickening in the form of strips. The gynoecium consists of three united carpels, a single style and three stigmas. The ovary has two fertile locuoles with one ovule and one sterile locuole, the placentation is pendulous. The ovary wall consists of epidermis and parenchymatous ground tissue penetrated by six vascular bundles and three bundles occur in the center of the ovary.
The study of vascularization revealed that each sepal has three traces, one median and two laterals. The median trace diverged directly from the receptacle, while the laterals and the petal trace have the same origin (strands). Since each strand ramifies into three traces; two of them constitute the lateral traces of the two adjacent sepals and the median one penetrates the base of the petal. Each stamen has one trace diverged directly from the receptacle and penetrates its filament. Each carpel has five traces, one dorsal two laterals and two ventrals.
The nectary appears in transverse section as five cavities developed on the receptacle between the stamen bases