LIST OF ILLUSTRATIONS. 



Plate A. Outline map of Algeria, showing main features of surface 

 drainage. 

 PI. I , fig. I . View of the oasis of Laghouat. 



2. Wood market at Laghouat. Juniper, oak, pine, and other kinds of wood, 



each bunch a camel load, exposed for sale. 



3. Wood market at Laghouat. Roots of Zizyphus, branches of juniper and 



pine, and pine bark. The latter is said to be used for staining. 

 PI. 2, fig. 4. Shoot-habit of Acanthyllis tragacanthoides. Laghouat. 



5. Shoot-habit of Zollikoferia spinosa. Laghouat. 



6. Acanthyllis tragacanthoides on sandy plain. Laghouat. 



7. Zollikoferia spinosa in habitat, plain (hamada). Laghouat. 



PI. 3, fig.3 8. Detail of north slope of Nomad Mountains, where Zollikoferia spinosa 

 is the dominant species. Laghouat. 

 9. Vegetation of plain (hamada) at Tilrempt. The conspicuous shrub is 



Haloxylon articulatum. 

 10. The daya of Tilrempt from the plain, showing the character of the 

 depression. 

 PI. 4, fig. II. 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. 

 12. Jujube {Zizyphus) shrubs and betoum (Pistacia) at the daya of Tilrempt. 

 PI. 5, fig. 13. A young specimen of betoum in the midst of a protecting jujube at the 

 daya of Tilrempt. 



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



15. Leaves of the betoum (Pistacia atlantica) from the daya of Tilrempt. 

 PI. 6, fig. 16. South wall of the valley of the Oued M'Zab at Ghardaia. 



17. Detail of an eroded bank of the Oued M'Zab at Ghardaia. The over- 

 hanging stratum is hardpan similar to the "caliche" of southwestern 

 United States. 

 PI. 7, fig. 18. Shoot-habit of Haloxylon articulatum, from the plain near the daya of 

 Tilrempt. 

 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). 

 PI. 8, fig. 20. Vegetation in upper part of a "draw" on plain north of the M'Zab 

 Valley, Ghardaia. 

 21. Situation of square No. 2, on plain north of valley at Ghardaia. 

 PI. 9, fig. 22. Capparis spinosa at base of valley wall at Ghardaia. 



23. Leaves of Capparis spinosa from Ghardaia. 

 PL 10, fig. 24. Leaf-habit of Dcemia cordata. Ghardaia. 



25. Shoot-habit of Salvia cegyptica. Ghardaia. 



26. Upper surface of rocks, showing small incrusting lichens, on a low moun- 

 ~- tain about 5 km. north of M'Zab Valley, Ghardaia. 



PI. II, fig. 27. Habitat of Peganum harmala, at Melika, Ghardaia. 



28. Shoot and leaf habit of Peganum harmala, from Ghardaia. 

 PI. 12, fig. 29. Habit of Henophyton deserti at Ghardaia when growing in a protected 

 situation (cemetery). 

 30. Leaf-habit of Henophyton deserti. Ghardaia. 

 PI. 13, fig. 31. View in a cemetery at Ghardaia, to show the relatively abundant vege- 

 tation. 

 32. View in an M'Zabite cemetery, Ghardaia. Haloxylon articulatum is the 

 leading species shown. 

 PI. 14, fig. 33. Habit of Deverra scoparia, from plain about 3 km. north of M'Zab Valley, 

 Ghardaia. 

 34. Root-habit of Gymnocarpos fruticosum, from plain about 3 km. north of 

 M'Zab Valley at Ghardaia. 

 PI. 15, fig. 55. 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 compara- 

 tively deep. 



iv 



