The bottom lands, as already has been shown, are relatively favorable
for plant life; here the soil is the deepest and the water relations
are the best. Accordingly we should expect to find in the valley of
the M’Zab more plants than we have seen on the plain, and we will
not be disappointed in these expectations; but it is almost certain
that in primitive times the vegetation of the valley was even richer
than at present. In fact we now find in the unprotected places only
such plants as are too small for fuel or are not good for food, and
the useful sorts are largely wanting. In other and similar valleys,
which have not been so much disturbed by man as the M’Zab and where
primitive conditions still largely obtain, there is a surprising
wealth of vegetation. Such conditions were seen between Ghardaia
and Ouargla and will be specially noted on another page.
At present no trees occur naturally in the valley in the vicinity of
Ghardaia or any of the sister cities. The French portion of Ghardaia
contains ornamental or shade trees, such as the ash, sycamore, and
betoum. The largest native shrubs are a species of _Tamarix_, growing
by the oued, and a few specimens of _Zizyphus lotus_, the latter
confined to the side gulches and numbering half a dozen specimens.
Among the most generally distributed plants in the valley are
_Peganum harmala_ (figs. 27 and 28) and _Haloxylon articulatum_; the
former is a half-shrub of wide distribution in southern Algeria,
occurring from Biskra on the north, and although not strictly
confined to the flood-plains of the oued is most abundant where the
soil is relatively deep. The leaves are rather large and do not appear
to have unusual protection against drought.[23] Like its relative
in the southwestern portion of the United States, the creosote bush
(_Covillea tridentata_), it is not eaten by any animals, although not
armed and not poisonous. This species, therefore, is one of the few
which to-day probably retains essentially the same distribution and
appearance it had before the country was inhabited. It is interesting
to note that _Peganum_ is generally distributed through the M’Zab
Valley, being especially abundant between Ben Isguen and Melika. Here
in November _Peganum_, except where trodden under foot by the flocks
and caravans, retained much of its foliage, although rain was said
not to have fallen for twelve months. In the protected areas also,
as will be mentioned below, this species was found to be fresh green,
showing little or no indication of the long drought. Of other species
found in unprotected places in the valley, _Haloxylon articulatum_
and _Henophyton deserti_, although eaten by animals so as to be
recognized only with difficulty, were also fairly abundant. There
were found also _Euphorbia guyoniana_, called “le bain” by our
French-speaking Arab helper, because it is used by the natives as
a soap, and _Nolletia chrysocomoides_, _Æluropus_ sp., and others.