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 situation 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 Phragmites 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 Retama 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 exudation 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 Touggourt and Ouargla, zaita can live 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” (Anabasis sp.), and Halocnemon strobilaceum, which appears especially resistant. (See figs. 59, 60, 61, and 62.)
Other forms appear on the higher ground and on the plain about 50 kilometers 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 peculiar. 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.
About 75 kilometers from Ouargla, and on a plain similar to that just referred to, “dhamran” (Traganum nudatum) was the most common species, but was by no means abundant. The census of an area 16 by 16 meters, taken in a locality where dhamran was dominant, resulted in finding 31 living and a few dead plants, probably all Traganum. It is to be understood that the vegetation of the reg desert not far distant is much richer, not only in species but especially in individuals, and also that the plants are much larger.
From 56 kilometers to about 71 kilometers from Ouargla the route lay over more or less continuous dunes, where the leading species seen were Aristida sp., Ephedra sp., Euphorbia guyoniana, Limoniastrum guyonianum, and Traganum nudatum.
In or about the edges of the chotts, which are the leading topographical features of the region immediately south of Touggourt, the most common species are Haloxylon sp., Salsola tetragona, Limoniastrum guyonianum, and Arabis aphyla. Besides these forms, about 28 kilometers south of Touggourt fine specimens of Halocnemon strobilaceum were seen growing in an extremely salty situation, to the total exclusion of other species. Tamarix also is to be found in and about salt spots near Touggourt. (See fig. 64.)
Both Massart and Doumet-Adanson (Bull. Soc. Bot. France, 39, 1892) have discussed the flora of the Touggourt-Ouargla region. The following exhaustive list is given by the latter author as having been collected between the two desert towns:
| Henophyton deserti. | Ammodaucus leucotrichus. | Plantago ciliata. |
| Matthiola livida. | Mesembryanthemum sp. | P. psyllium. |
| Malcolmia ægyptica var. linearis. | Deverra chlorantha. | Scrophularia saharæ. |
| Moricandia cinerea. | Nolletia chrysocomoides. | Linaria fruticosa. |
| Sisymbrium pendulum. | Senecio coronopifolius. | Euphorbia guyoniana. |
| Savignya longistyla. | Anthemis monilicostata. | Atriplex dimorphostegius. |
| Reseda stricta. | Tanacetum cinereum. | Caroxylon tetragonum. |
| R. arabica. | Ifloga fontanesii. | Echinopsilon muricatus. |
| Helianthemum sessiliflorum. | Centaurea purpuracea. | Calligonum comosum. |
| H. ellipticum. | Amberboa omphalodes. | Haloxylon articulatum. |
| Randonia africana. | Rhantherium adpressum. | Anabasis articulata. |
| Frankenia pulverulenta. | Atractylis flava. | Cornulacea monocantha. |
| Silene nicoeensis. | A. prolifera. | Thymelea hirsuta. |
| Monsonia nivea. | A. microcephala. | Th. microphylla. |
| Erodium glaucophylum. | Tourneuxia variifolia. | Aristida flaccosa. |
| Fagonia glutinosa. | Catananche arenaria. | A. pungens. |
| F. frutescens. | Spitzelia saharæ. | Cyperus conglomeratus. |
| Polycarpæa fragilis. | Zollikoferia chondrilloides. | Ephedra fragilis. |
| Gymnocarpus decandrus. | Z. squamosa. | Erythrostictus punctatus. |
| Retama retam. | Scorzonera undulata. | Scilla sp. |
| Genista saharæ. | Echium humile. | Dipcadi serotinum. |
| Astragalus gumbo. | Echiochilon fruticosum. | Asphodelus pendulinus. |
| Anthyllis henoniana. | Arnebia decumbens. | Ruppia maritimus. |
| Neurada procumbens. | Statice pruinosa. | Chara fœtida. |
| Limoniastrum guyonianum. |