Touggourt to Biskra — Physical Features and Vegetation
From Ouargla to Touggourt we have found that the country gradually descends, the former place being 124 meters and the latter 77 meters above the level of the sea. From Touggourt, also, for a distance of about 120 kilometers, the descent along the route continues until at the Chott Merouan a level of 6 meters is attained. The lowest places in every case are of course the chotts and the connecting oueds. The most important chott of this series is Melrirh, 11 meters or more below sea-level. This drainage system is the northern culmination of the vast one of which the Oued Igharghar is the most important part. In an earlier age water came north in the oued from the highlands of central Sahara and poured into the Chott Melrirh, having passed successively through the lesser chotts farther south. At that time, also, the Chott Melrirh probably was connected with the Gulf of Gabes.
From Touggourt to Chott Merouan, the lowest portion of the route to Biskra, the topography is that of a region of chotts; that is, there are salt spots surrounded on every side by higher ground, which in many cases is of sand. From Chott Merouan the route passes over a higher desert of a different character, which in part bears a remote resemblance to the Gantara and in part to the Ouargla plain. It is a vast plain, with little topographical diversity, which rises to meet the Atlas Mountains to the west and north. In the eastern portion it is somewhat rolling, stones are strewn plentifully on its surface (hamada), and there has been considerable erosion, so that gullies are formed. In the portion nearer Biskra the surface is more level, the soil is fine (reg), and there has been comparatively little erosion.
The soil of the chott region is largely of sand; on the hamada there is much clay, while on the reg it is fine and easily blown by the wind, and this in spite of the fact that the most vegetation seen in the Sahara was in this region. A slight breeze picks up the dust and carries it long distances in dark clouds. It fills the throat, nose, and eyes of the traveler and makes crossing the reg exceedingly disagreeable.
The plant life as seen along the portion of the route through the chott region consists almost wholly of halophytes, as would be expected, in addition to which, where for short distances the hamada or dunes were crossed, there were forms characteristic of such areas. The Tamarix is especially common in the region and Limoniastrum guyonianum is also often met.
The date gardens of the Oued Rirh are justly famous. One passes numberless plantations where the date is cultivated, and in the neighborhood of each group of gardens one sees squalid Arab villages. Over 19,000 tons of dates are said to be carried each year by camel from the Oued Rirh to Biskra, whence they go to the markets of the world. One day we passed 700 camels laden with dates going to Biskra.
As soon as the chott region is left and the higher ground is reached a different as well as a richer flora is encountered. Here diversity of topography favors diversity of plant life. On the reg near Biskra vegetation is especially abundant. Here, in fact, one passes through large thickets of Tamarix and other species, and sees that the desert is much less intense than that in the south, especially in the region of the M’Zab, where in many respects the topography is similar. The kinds of plants also, as the list below will indicate, are different in the main from those farther to the south. Where the surface is most rolling we find Tamarix sp. on the heights, Zizyphus lotus in the hollows, and the following grasses: Stipa tortilis, Hordeum maritimum, and Phalaris minor. A salsolaceous shrub (Arthrocnemon macrostachyum) may be found in washes, Nitraria and Limoniastrum guyonianum on sandy places, and Odontospermum pygmæum and Anastatica hierochuntica occur between rocks. On clay flats one finds Halocnemon strobilaceum and Suæda vermiculata, indicating the presence of salts.
The preceding notes are in part from Massart. The following species are given by Doumet-Adanson as having been collected by him between Biskra and Touggourt:
| Savignya longistyla. | Nitraria tridentata. | Nonnæa micrantha. |
| Eremobium lineare. | Astragalus gyzensis. | Lithospermum callosum. |
| Lonchophora capiomontana. | Ononis serrata. | Heliotropium undulatum. |
| Monsonia nivea. | Ammodaucus leucotrichus. | Plantago ciliata. |
| Erodium pulverulentum. | Cyrtolepis alexandrina. | P. albicans. |
| Fagonia sinaica. | Anacyclus clavatus. | Limoniastrum guyonianum. |
| Haplophyllum tuberculatum. | Pyrethrum fuscatum. | Statice pruinosa. |
| Lœfflingia hispanica. | Nolletia chrysocomoides. | Echinopsilon muricatus. |
| Paronychia nivea. | Tanacetum cinereum. | Traganum nudatum. |
| P. cossoniana. | Ifloga fontanesi. | Ephedra alata. |
| Herniaria fruticosa. | Artemisia herba-alba. | Cutandia memphitica. |
| Zygophyllum album. | Anvillæa radiata. | Erythrostictus punctatus. |
| Z. cornutum. | Atractylis flava. | Asparagus albus. |
| Peganum harmala. | A. prolifera. | Aristida pungens. |