56 BOTANICAL FEATURES OF THE ALGERIAN SAHARA. 



"vararan" of the Arabs and is an inconspicuous shrub frequently seen 

 later on the way to Touggourt. 



OUARGLA TO TOUGGOURT— VEGETATION. 



Ouargla is an ancient, rambling town, somewhat in decay, set in the 

 midst of extensive palm gardens. There are said to be 500,000 date palms 

 at the oasis. It was founded in the tenth century by the M'Zabites and 

 later taken possession of by the Arabs. The town is peculiar in its situa- 

 tion and its gardens, lying, as before described, in the flood-plain of an 

 ancient river. The plants cultivated in the town as ornamentals are fewer 

 than at Ghardaia, but of the same kinds, and (besides dates) the gardens 

 contain fewer fruits and apparently fewer kinds of vegetables. Between 

 the gardens one finds Tamarix in some abundance. 



Leaving Ouargla by the western gate and turning north, we soon passed 

 through the crooked streets and reached the reg desert to the north. There 

 is little vegetation near Ouargla, but on some low dunes extending over the 

 reg we found Aristida pungens and Phargmites sp., growing in a hollow. 

 On the flood-plain there were a large number of individuals and probably 

 a large number of species. Among the most conspicuous of the shrubs were 

 Retania retam and Limoniastrum guyonianum, the "zaita" of the Arabs. 

 (See figs. 56 and 57.) Zaita is a handsome shrub with cylindrical leaves often 

 covered with a fairly heavy salt incrustation. So abundant is the exuda- 

 tion that in localities where the species is especially abundant, as at our 

 camp 32 kilometers south of Touggourt, the plants have the appearance of 

 being covered with snow. Although, like many other species between Toug- 

 gourt and Ouargla, zaita can Uve where there are salts in excess, it appears 

 not to be an extreme type of halophyte and does not occur where the salts 

 are most dense. It was seen both on the dunes and on the low lands. 

 Other common halophytes are "souid" (Salsola tetragona), "belbel" {Ana- 

 basis sp.), and Halocnemon strohilaceum, which appears especially resistant. 

 (See figs. 59, 60, 61, and 62.) 



Other forms appear on the higher ground and on the plain about 50 kilo- 

 meters from Ouargla, where Ephedra alata especially is common. There 

 are no dunes on the plain, but some sand swept across it from the fluvial 

 desert to the west passes eastward and augments the dunes farther east. 

 The larger specimens of Ephedra are rather effective sand-binders and bring 

 about the formation of diminutive dunes. The effect on the growth of the 

 species by the piling sand is pecuHar. As the sand accumulates it covers 

 the lower branches of the shoot; these are stimulated to unusual growth 

 and new branches may spring from them. Thus the effect is similar to 

 that habitually occurring in E. alenda, but in E. alata the habit is not a 

 fixed one. As an instance of the length which such submerged branches 

 may attain, it may be mentioned that one, 2 to 3 cm. in diameter, was over 

 4 meters long. 



