The plants seen during the first day’s march from Ghardaia
were such as have already been observed to be characteristic of
the valley of the Oued M’Zab or of the neighboring hamada. The
vegetation of the hamada, usually very sparse, was noticeably more
abundant wherever the sand had been drifted over it from the dunes
of the valley, even if the thickness of the sand was so slight
as to be little more than a mulch. Here low grasses, much eaten,
were the prevailing forms. On the dunes in the valley of the
M’Zab, 20 kilometers from Ghardaia, the number of species and
individuals is relatively large, the most abundant species being
drinn (_Aristida pungens_), although _Deverra scoparia_ is also
fairly numerous. Somewhat farther on the route, and in a sandy flat,
besides these two species, there is much _Ephedra alata_. On the
slopes leading from this flat and on the plain above, there is an
almost pure stand of _Rhantherium adpressum_.
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.[28]
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.=