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. |
THE BISKRA REGION.
TOPOGRAPHY.[29]
Biskra lies immediately south of the Atlas Mountains, in the Department of Constantine, 220 kilometers from the Mediterranean and about 400 kilometers from Ouargla. To the northeast of the oasis lie the Aurés and to the west the beginning of the Saharan Atlas, which run south of west across Algeria into Morocco. Just north of the place are small hills and low, jagged mountains—detached spurs from the main ranges. These are the Djebel Bou Rhezal, running nearly northeast and southwest. The highest of them, directly west of Biskra and about 8 kilometers distant, has an altitude of 463 meters. The Bou Rhezal Mountains have a precipitous southern face, but fall away more gradually to the north, where the slope joins a wide and undulating plain. The latter extends to the base of the main Atlas ranges. Southwest of the oasis, and about 2 kilometers distant, a range of rocky hills extends for a distance of about 6 kilometers, or until they join the mountain range of the Saharan Atlas. These hills are called Ed Delouatt. To the south of Biskra, as has already been stated, there extends a vast plain, the reg, which dips gently to the south and drains into the Chott Melrirh, 50 kilometers or more distant. The situation of Biskra relative to the mountains on the one side and the desert on the other, together with its altitude, governs the climate of the place. Except Laghouat no vicinity in the desert proper was seen with so great an amount of precipitation (about 200 mm.) as Biskra, which is indicated by the relatively rich flora. One who has seen only Biskra can not draw conclusions regarding the vegetation or the conditions of plant life of those portions of the Sahara that lie farther to the south, where much more intense conditions of aridity obtain.
The soils of the vicinity of Biskra are various. That of the low hills between the town and the Djebel Bou Rhezal is only a few centimeters in thickness, but in the washes from the hills it is a meter or more. Here the soil is a sandy loam with an admixture of small stones and pebbles. On the flat ground to the north and to the south of these hills it is of a finer texture, approaching the adobe of the southwestern United States. On the reg to the south of the oasis the soil is also fine, and in some places, if not underlying the plain as a whole, there are strata of gravel at varying depths beneath the surface. This soil in places carries considerable salts. It dries to a powder during the long dry seasons and is easily blown by the winds. Owing to outcropping rock, the south face of the Bou Rhezal Mountains has but scant soil, but that of the northern side resembles the soil of the low hills to the south, which has already been characterized. Near the town are dunes of good size. Especially to the southwest the sand banks against Ed Delouatt hills is in large amount. In the opposite direction, but farther from the oasis, the dunes are fairly extensive.
The Oued Biskra is of great importance to the oasis, since it carries water for several weeks of the year and furnishes water for irrigation. Its channel lies about 3 meters, or possibly more, below the general level of the oasis, and possibly in earlier times may not have been so well defined as at present, spreading its waters over its flood-plain during high water. The oued is made up of several tributary oueds which cross the plain north of Djebel Bou Rhezal, unite where there is a pass in these mountains, and finally debouch on the reg to the south of the town, where the channel becomes continually less well defined. Another oued takes its origin in the Bou Rhezal Mountains in several independent branches which unite at a pass in Ed Delouatt hills and extend for a distance of 15 kilometers or more into the reg. One of the feeders of this oued is from hot springs, Hamman es Salahine, about 8 kilometers northwest of Biskra.