Included here is the Sahara - the largest desert in the world. In an east-west axis it stretches from the Libyan Desert to shores of the Atlantic Ocean, but the northern and southern boundaries are less well defined. In the north there is a gradual transition to Mediterranean vegetation, while in the south there is a transition to tropical vegetation.

Saharan Stipagrostis plumosa Desert Calcareous Grassland

Grassland dominated by tussocks of Stipagrostis plumosa can be found, for example, on the Eocene limestone in the Bahariyah, Sitra abd Farafra regions of Egypt. In the northern part of the Farfra oasis the vegetation typically grows in deep karstic holes filled with sand and known locally as flowerpot vegetation. Associated species mainly comprise herbaceous perennials and dwarf shrubs and may include Astragalus trigonus, A. vogelii, Calligonum comosum, Convolvulus pilosellifolius, Cotula cinerea, Fagonia arabica, Farsetia aegyptiaca, Launaea nudicaulis, Salsola baryosma, Stipagrostis zittelii, Tamarix passerinoides and the endemic or near endemic Anabasis articulata (Amaranthaceae), Cornulaca monacantha (Chenopodiaceae), Pituranthos tortuosus (Apiaceae), Suaeda vermiculata (Chenopodiaceae) and Zygophyllum album (Zygophyllaceae).

Saharan Halogypsophilous Vegetation

This salt tolerant vegetation is mostly confined to depressions devoid of any drainage and as a result subjected to high levels of evaporation. Salt from sub-surface strata is brought to the surface by capillary action. In hypersaline situations the extreme halophyte Halocnemum strobilaceum may be the only species present, but in less demanding situations species such as Limonium pruinosum, Nitraria glaucum, Salsola sieberi, Suaeda mollis, Zygophyllum cornutum, the endemic Arthrocnemum glaucum (Chenopodiaceae) and Limoniastrum guyonianum (Lamiaceae) and near endemic Salsola tetragona (Chenopodiaceae), Traganum nudatum (Chenopodiaceae) and Zygophyllum album (Zygophyllaceae) be can be found but there is some regional variation.  Where gypsaceous loamy sands occur a new suite of species are encountered often dominated by Salsola baryosma and the near endemic Suaeda vermiculata (Chenopodiaceae). Other associated species include the endemic Lycium inticatum (Solanaceae) and Nucularia perrinnii (Chenopodiaceae) and the near endemic Atriplex halimus (Chenopodaceae). 

References

Bornkamm, R. & Kehl, H. 1990. The plant communities of the Western Desert of Egypt. Phytocoenologia, 19: 149-231.

Davis, P. H. 1953. The vegetation of the deserts near Cairo. Journal of Ecology, 41: 157-173. 

Quezel, P. 1978. Analysis of the flora of the Mediterranean and Saharan Africa. Annals of the. Missouri Botanicl Garden, 65: 479-534.

White, F. 1983. The Vegetation of Africa. UNESCO.

Zohary, M. 1971. The Phytogeographical Foundations of the Middle East. In: Plant Life of South-West Asia. Eds. P. H. Davies, P. C. Harper and I. C. Hedge. The Botanical Society of Edinburgh.