[Plate 24:
Illustration: Fig. 56. Ouargla to Touggourt. Leaf-habit of
Limoniastrum guyonianum. The surface of the leaves is covered with an
incrustation of salts.
Illustration: Fig. 57. Habit of Limoniastrum guyonianum. About 25km.
north of Ouargla.]
[Plate 25:
Illustration: Fig. 58. Vegetation of the reg. desert, about 25km.
north of Ouargla. Ephedra and Retama are the leading species of the
area a spreading dune.
Illustration: Fig. 59. Shoot-habit of Halocnemon strobilaceum, about
28km. north of Ouargla.]
[Plate 26:
Illustration: Fig. 60. Habit of Halocnemon strobilaceum, on the edge
of a chott, about 28km. north of Ouargla.
Illustration: Fig. 61. Shoot and leaf habit of Anabasis articulata,
about 32km. north of Ouargla.]
[Plate 27:
Illustration: Fig. 62. Detail of the shoot-habit of Salsola
tetragona?, about 25km. north of Ouargla.
Illustration: Fig. 63. Habit of Nolletia chrysocomoides near the edge
of a chott, about 80km. north of Ouargla.]
[Plate 28:
Illustration: Fig. 64. Tamarix sp. as a sand-binder near
Bled-el-Amar, south of Touggourt.
Illustration: Fig. 65. Biskra. Habitat of Euphorbia guyoniana,
looking toward the Djebel Maouya, with the Chaine de Sfa in the
background.]
[Plate 29:
Illustration: Fig. 66. Characteristic vegetation on the north slope
of the Djebel Bou Rhezal, Biskra. Haloxylon scoparium is a prominent
species.
Illustration: Fig. 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.]
[Plate 30:
Illustration: Fig. 68. Flood-plain of the Oued Hamman es Salahin,
Biskra. Halophytes of various species occupy the foreground.
Illustration: Fig. 69. Habitat of Phelypæa violacea shown in figure
70.]
[Plate 31:
Illustration: Fig. 70. Young shoots of Phelypæa violacea, at north
base of Ed Delouatt hills, Biskra.
Illustration: Fig. 71. Habit of young specimens of Phelypæa. Except
for about 15cm., plants were buried by sand. Biskra.
Illustration: Fig. 72. Asphodelus sp. at north base of Ed Delouatt
hills, Biskra. Photographed in March.]
[Plate 32:
Illustration: Fig. 73. Detail of square No. 1, on low hills north of
Biskra.
Illustration: Fig. 74. Vegetation of north slope of the low hills
which are north of Biskra. Ferula vesceritensis is the perennial
appearing in the figure.]
[Plate 33:
Illustration: Fig. 75. Detail of square No. 2, neat area shown in
fig. 74. Ferula and Haloxylon are the leading species.
Illustration: Fig. 76. Root-habit of Haloxylon scoparium, from a wash
near Biskra.
Illustration: Fig. 77. Young shoots and mature roots of Ferula
vesceritensis. North of Biskra.]
[Plate 34:
Illustration: Fig. 78. Root-habit of Fagonia growing on edge of a
wash. Biskra.
Illustration: Fig. 79. Large lateral root of Haloxylon, with numerous
deciduous rootlets, no longer functional.
Illustration: Fig. 80. Shoot-habit, taken from above, of Fagonia from
the flood-plain of a small oued near Biskra.]
[Plate 35:
Illustration: Fig. 81. Spring annuals, March 17th, on north slope of
the Djebel Bou Rhezal, Biskra.
Illustration: Fig. 82. Root and shoot habit of Peganum harmala,
Biskra. The main root is especially well developed although the
species has a generalized root-system. (See text.)]
[Plate 36:
Illustration: Fig. 83. Annuals growing with Peganum, near Biskra.
Illustration: Fig. 84. General view of the north face of the Djebel
Bou Rhezal, Biskra. Apparently barren, plants are rather numerous in
the rock crevices and small washes of the mountains.]