Pl. 24, fig. 56. Ouargla to Touggourt. Leaf-habit of _Limoniastrum
guyonianum_. The surface of the leaves is
covered with an incrustation of salts.
57. Habit of _Limoniastrum guyonianum_. About 25 km.
north of Ouargla.
Pl. 25, fig. 58. Vegetation of the reg desert, about 25 km. north
of Ouargla. _Ephedra_ and _Retama_ are the
leading species of the area—a spreading dune.
59. Shoot-habit of _Halocnemon strobilaceum_. About
28 km. north of Ouargla.
Pl. 26, fig. 60. Habit of _Halocnemon strobilaceum_ on the edge of
a chott, about 28 km. north of Ouargla.
61. Shoot and leaf habit of _Anabasis articulata_,
about 32 km. north of Ouargla.
Pl. 27, fig. 62. Detail of the shoot-habit of _Salsola
tetragona?_, about 25 km. north of Ouargla.
63. Habit of _Nolletia chrysocomoides_ near the edge
of a chott, about 80 km. north of Ouargla.
Pl. 28, fig. 64. _Tamarix_ sp. as a sand-binder near Bled-el-Amar,
south of Touggourt.
65. Biskra. Habitat of _Euphorbia guyoniana_, looking
toward the Djebel Maouya, with the Chaine de
Sfa in the background.
Pl. 29, fig. 66. Characteristic vegetation on the north slope
of the Djebel Bou Rhezal, Biskra. _Haloxylon
scoparium_ is a prominent species.
67. North base of Ed Delouatt hills, west of Biskra,
showing the low facing dunes. To the right is a
glimpse of an oued which pierces the hills in
the middle distance.
Pl. 30, fig. 68. Flood-plain of the Oued Hamman es Salahin,
Biskra. Halophytes of various species occupy
the foreground.