Part 18

Illustration: Fig. 8. Detail of north slope of Nomad Mountains where Zollikoferia spinosa is the dominant species. Laghouat.

Illustration: Fig. 9. Vegetation of plain (hamada) at Tilrempt. The conspicuous shrub is Haloxylon articulatum.

Illustration: Fig. 10. The Daya of Tilrempt from the plain, showing the character of the depression.]

Illustration: Fig. 11. Near view of the Daya of Tilrempt. The fortified stage station, bordj, and a nomad camp are to be seen. The flattened, level, lower surface of the trees is the effect of grazing, mainly by camels.

Illustration: Fig. 12. Jujube (Zizyphus) shrubs and betoum (Pistacia) at the Daya of Tilrempt.]

Illustration: Fig. 13. A young specimen of betoum in the midst of a protecting jujube, at the Daya of Tilrempt.

Illustration: Fig. 14. Leaf and shoot habit of the jujube (Zizyphus lotus). Daya of Tilrempt.

Illustration: Fig. 15. Leaves of the betoum (Pistacia atlantica), from the Daya of Tilrempt.]

Illustration: Fig. 16. South wall of the valley of the Oued M’Zab at Ghardaia.

Illustration: Fig. 17. Detail of an eroded bank of the Oued M’Zab at Ghardaia. The overhanging stratum is hardpan similar to the “caliche” of southwestern United States.]

Illustration: Fig. 18. Shoot-habit of Haloxylon articulatum, from the plain near the Daya of Tilrempt.

Illustration: Fig. 19. Agriculture at Ghardaia. The fields are divided into plots about 3 by 4 feet in size, for the more economical use of water. Young barley is shown growing (November).]

Illustration: Fig. 20. Vegetation in upper part of a “draw” on plain north of the M’Zab Valley Ghardaia.

Illustration: Fig. 21. Situation of square No. 2. on plain north of valley at Ghardaia.]

Illustration: Fig. 22. Capparis spinosa at base of valley wall at Ghardaia.

Illustration: Fig. 23. Leaves of Capparis spinosa, from Ghardaia.]

Illustration: Fig. 24. Leaf-habit of Dæmia cordata. Ghardaia.

Illustration: Fig. 25. Shoot-habit of Salvia ægyptica. Ghardaia.

Illustration: Fig. 26. Upper surface of rocks, showing small incrusting lichens, on a low mountain about 5km. north of the M’Zab Valley, Ghardaia.]

Illustration: Fig. 27. Habitat of Peganum harmala, at Melika, Ghardaia.

Illustration: Fig. 28. Shoot and leaf habit of Peganum harmala, from Ghardaia.]

Illustration: Fig. 29. Habit of Henophyton deserti at Ghardaia when growing in a protected situation (cemetery).

Illustration: Fig. 30. Leaf-habit of Henophyton deserti. Ghardaia.]

Illustration: Fig. 31. View in a cemetery at Ghardaia, to show the relatively abundant vegetation.

Illustration: Fig. 32. View in an M’Zabite cemetery, Ghardaia. Haloxylon articulatum is the leading species shown.]

Illustration: Fig. 33. Habit of Deverra scoparia, from plain about 3km. north of M’Zab Valley, Ghardaia.

Illustration: Fig. 34. Root-habit of Gymnocarpos fruticosum, from plain about 3km. north of M’Zab Valley, Ghardaia.]

Illustration: Fig. 35. Root-habit of a mature specimen of Peganum harmala, from the floor of the M’Zab Valley near Ghardaia. The soil at the place is comparatively deep. (See text for further explanation.)