Several workers (SA]3ET 1935, 1939; REI~OLD~ 1951; GA]~RT~E~ 1954 and MVSKAT 1955a, b) have made extensive studies on the soil fungi inhabiting natural soils or present in the rhizosphere of certain wild plants throughout the world.
The first author (SABET 1935(SABET , 1939) isolated--from Egyptian soil--many fungi inhabiting different types of soil, e.g. loamy fields, heavy clay, sandy natural soils, salt marshes, etc., and could prove variation in the abundance, as well as, genera and species of different isolates from the different localities under study. Similarly, REI~BOLDT (1951) found that most of the Phycomycetes isolated by her from certain localities, in Germany, were irregularly distributed throughout the soil, and their frequency within the rhizosphcre of certain higher plants was modified by the stimulatory and inhibitory influences of the latter. Among the plants that induced stimulatory effects were Rumex acetosa and chicory, while Chelidonium ma]us exerted a. repressive effect. Mention should be also made to the work of GAE~T~ER (1954), who showed that natural soil of North Sweden or certain localities of Germany were very poor in soil fungi, especially with respect to Mucoraceae and Pythiaceae, in comparison with those present in African soils. Similar results were also concluded by MVSKAT (1955a, b) on comparing the mold-fungi of Bavarian and Tunesian soils.
However, the above mentioned authors, and others were not interested in studying the rhizosphere microflora (bacteria and fungi) of desert plants with respect to depth of the soil or the root zones themselves. Furthermore, comparisons between mieroflora of the rhizosphere, rhizoplane, and direct surface of the different root zones of specific wild plants has not been worked out.
Among many of the edaphic factors which affect the relative distribution of rhizospheric microflora of a specific higher plant are the depth of soil and the root zones themselves. The latter, i.e. root tip, zone of lateral roots and root base are expected to possess different microbiological activities governed by several factors, e.g. moisture and humus content, water-soluble salts, physico-chemical structure of the soil, root exudates, etc. However, it is hardly to say that the presented literature, in the last decades, on the rhizosphere microflora of different Arch. l~Iikrobiol., Bd. 50 22