Part 14

Crossing relatively small portions of the plain, in place of always following the bends of the Oued M’Zab, about noon of the second day we reached the bordj Zolfana, in the valley of the Oued amidst low and narrow dunes, which are moving slowly across the flats. (Fig. 44.) No vegetation appears on the dunes, but on the fixed sand between them, or on the stationary dunes at the border of the flats, some plants are to be found. Among these the most abundant, but really not numerous, are Euphorbia guyoniana and retam (Retama retam), which was often seen later along the line of march as well as in the vicinity of Biskra. Retam superficially resembles Ephedra alata in having rudimentary leaves and green, reed-like branches; it is carefully avoided by animals, although Genista saharæ, a very similar plant, which grows in like situations between Ghardaia and Ouargla, is said by Massart (loc. cit.) to be eaten greedily by them. (Fig. 43.)

A short distance beyond the bordj the bottoms suddenly widened, the dunes disappeared, and for the remainder of the day’s march we passed through the richest vegetation we had seen since reaching the M’Zab region. (Figs. 45, 46, and 47.) Here the shrubs were of fair size and of sufficient abundance to give character to the landscape. About the 63 kilometers camp the leading species are Retama retam, Ephedra alata, and Haloxylon schmidtianum. On the hamada adjoining the flat are several species, including Aristida ciliata, Artemisia herba-alba, Farsetia ægyptiaca, Farsetia linearis, Gymnocarpon fruticosum, Helianthemum eremophilum, Henophyton deserti, Marrubium deserti, Salsola vermiculata, Teucrium polium, Thymelæa microphylla, and Zollikoferia mucronata. On the hamada just adjoining the place of our camp, however, there appeared to be Haloxylon schmidtianum, to the exclusion of other species.

After crossing the bottoms of the oued the trail climbed up to the hamada and we did not see the M’Zab Valley afterward. The vegetation of the hamada soon becomes very sparse and as far as the eye can reach the appearance is that of entire bareness. But, as was found to be the case near Ghardaia, close examination revealed the presence of many living perennials as well as the remains of the previous annual flora. This plain, the Gantara, of wide extent, is the most arid region seen in southern Algeria. Massart estimates that there is an average precipitation of 15 cm. on the desert, but, from data previously cited, it would appear that this amount is rarely attained; indeed, several months, or even two or more years, may pass without any rainfall whatever. When one searches the hollows he finds a few small perennials; plants are almost wholly absent on the low ridges. But in some areas on the plain, where superficial examination does not show any plants, a surprising number were found. For example, on the level hamada, 96 kilometers from Ghardaia, on an area 16 meters square, 389 living plants were found, but only 24 were so large as to be seen from a distance; all were either eaten badly or trampled to the ground, so that it could not be learned what the flora of the area might have been had no animals interfered with its full development.

After leaving the 96 kilometer station the perennials were seen to diminish rapidly in numbers and to decrease in size, until the ridges of the low undulations were absolutely without plants, and there were but few in the hollows. There was no apparent change in the character of the hamada or in that of the soil. This sterile condition persisted for 26 kilometers, when vegetation similar in character to that previously seen was again encountered. The zone of better vegetation lasted for 3 kilometers, when the country became barren once more, which condition lasted for 10 kilometers. The presence of barren belts on the Gantara, where the plants at the best are insignificant in size as well as number and without change in topography or soil, points to an especially arid belt. This conclusion is further strengthened by the observation that the plants found were relatively of very small size.

The flora was also sparse upon the route followed by Massart across the Gantara, which was apparently somewhat farther to the north than the one now being described. He mentions having found Argyrolobium uniflorum, Asteriscus graveolens, Fagonia microphylla, Deverra chlorantha, Fagonia glutinosa, Halogeton alopecuroides, Helianthemum sp., and Herniaria fruticosa. He says that Deverra is one of the rare glabrous forms on the hamada. It is said to have the odor of parsley, and the Arabs have a belief that camels which eat it become blind, but Massart’s camels were not injured by eating the plant.

As we drew near the Chott Mellala, on the eastern edge of the barren zone mentioned in the preceding paragraph, we suddenly encountered a belt of Ephedra alenda, stretching to the north and to the south as far as could be seen (fig. 49). On one side was the barren zone, on the other the immense plantation. Upon examination it was found that the Ephedra was the only species of perennial. It had several points of interest, but the short time at our disposal precluded more than a superficial examination. Usually keen about the desert species, it is curious to note that the Arabs appear not to recognize this, called by them “alenda,” as being related to the larger species of Ephedra with which they are well acquainted. It is a small species, growing from 30 to 40 cm. high. It does not occur singly, but has the habit of growing in groups of a half dozen or more. Between the Ephedra colonies were only the dried remains of the annual flora of the last rainy season. An examination of the root-system of the species showed that, like other species of the genus, it has a well-developed tap-root (fig. 50).

Alenda, however, has a root-habit which, although not peculiar to it, is at least very striking and of great importance to its survival. From the root-crown a stolon arises which extends away from the parent for a distance of about a meter. From this stolon there arise shoots which develop into daughter plants. Through this method of reproduction the small colonies of the species are formed and possibly the species mainly multiplied. From the stolons small roots arise, giving aid to the mother root in providing the offspring with moisture. This habit is very like that of Kœberlinia spinosa of the Arizona desert, which has a similar type of root-system and which reproduces vegetatively in a similar manner. Alenda continued to be the dominant species until near the edge of the big chott (Mellala), a few kilometers east of where it was first seen.

Practically no plants were seen when descending through the eroded portions of the hamada to the floor of the chott (fig. 52), but on reaching the bottom of the great chott a surprisingly large number was observed, including Anabasis articulata, Aristida pungens, Ephedra alata, Limoniastrum guyonianum, Retama retam, and Traganum nudatum (fig. 51). In the wide central part of the chott, where the salts are perhaps most dense, there are no plants; but on the eastern side are Euphorbia guyoniana, Anabasis articulata, and Zygophyllum sp. These small species were growing far apart and were badly injured, either by being trodden under foot or by being eaten by the passing animals. To the south of where we crossed the chott and also to the north the sand mountains arise. After leaving Chott Mellala we ascended gradually to go over a low pass separating it from a small chott to the east. Here we obtained a backward view of the sand mountains, low as seen from the pass, with sharp, wind-made ridges, and bearing a few specimens of Aristida pungens. Descending somewhat, another but smaller chott was crossed. Between the latter chott and the Ouargla plain the plants were very few and confined to the slopes and the higher ground, avoiding almost wholly the depressions. Of those recognized, Traganum nudatum was the most abundant. This is the “vamran” 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 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. Matthiola livida. Malcolmia ægyptica var. linearis. Moricandia cinerea. Sisymbrium pendulum. Savignya longistyla. Reseda stricta. R. arabica. Helianthemum sessiliflorum. H. ellipticum. Randonia africana. Frankenia pulverulenta. Silene nicoeensis. Monsonia nivea. Erodium glaucophylum. Fagonia glutinosa. F. frutescens. Polycarpæa fragilis. Gymnocarpus decandrus. Retama retam. Genista saharæ. Astragalus gumbo. Anthyllis henoniana. Neurada procumbens. Ammodaucus leucotrichus. Mesembryanthemum sp. Deverra chlorantha. Nolletia chrysocomoides. Senecio coronopifolius. Anthemis monilicostata. Tanacetum cinereum. Ifloga fontanesii. Centaurea purpuracea. Amberboa omphalodes. Rhantherium adpressum. Atractylis flava. A. prolifera. A. microcephala. Tourneuxia variifolia. Catananche arenaria. Spitzelia saharæ. Zollikoferia chondrilloides. Z. squamosa. Scorzonera undulata. Echium humile. Echiochilon fruticosum. Arnebia decumbens. Statice pruinosa. Limoniastrum guyonianum. Plantago ciliata. P. psyllium. Scrophularia saharæ. Linaria fruticosa. Euphorbia guyoniana. Atriplex dimorphostegius. Caroxylon tetragonum. Echinopsilon muricatus. Calligonum comosum. Haloxylon articulatum. Anabasis articulata. Cornulacea monocantha. Thymelea hirsuta. Th. microphylla. Aristida flaccosa. A. pungens. Cyperus conglomeratus. Ephedra fragilis. Erythrostictus punctatus. Scilla sp. Dipcadi serotinum. Asphodelus pendulinus. Ruppia maritimus. Chara fœtida.

=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. Eremobium lineare. Lonchophora capiomontana. Monsonia nivea. Erodium pulverulentum. Fagonia sinaica. Haplophyllum tuberculatum. Lœfflingia hispanica. Paronychia nivea. P. cossoniana. Herniaria fruticosa. Zygophyllum album. Z. cornutum. Peganum harmala. Nitraria tridentata. Astragalus gyzensis. Ononis serrata. Ammodaucus leucotrichus. Cyrtolepis alexandrina. Anacyclus clavatus. Pyrethrum fuscatum. Nolletia chrysocomoides. Tanacetum cinereum. Ifloga fontanesi. Artemisia herba-alba. Anvillæa radiata. Atractylis flava. A. prolifera. Nonnæa micrantha. Lithospermum callosum. Heliotropium undulatum. Plantago ciliata. P. albicans. Limoniastrum guyonianum. Statice pruinosa. Echinopsilon muricatus. Traganum nudatum. Ephedra alata. Cutandia memphitica. Erythrostictus punctatus. Asparagus albus. Aristida pungens.

=THE BISKRA REGION.=

TOPOGRAPHY.