LIST OF ILLUSTRATIONS. V 



PI. 15, fig. 36. Root-systems of Helianthemum sessiliflorum (right), Haloxylon articu- 



latum, and Nolletia chrysocomoid.es (left), from the flood- plain of the 



Oued M'Zab, Ghardaia. 

 PI. 16, fig. 37. Shoot and root habit of Citrullus colocynthis. Oued M'Zab, Ghardaia. 



38. Euphorbia guyoniana, in the valley of the Oued M'Zab at Ghardaia. 

 PI. 17, fig. 39. Habit of Euphorbia guyoniana. Ghardaia. 



40. To the left, shoot of Centaurea sp., showing effect of grazing; to the right, 



shoots of Teucrium pseudo-chamcepitys. From Ghardaia. 

 PI. 18, fig. 41. Habit of Salsolasp. (below) and Echinopsilon muricatus, from the M'Zab 



Valley, Ghardaia. 

 42. Ghardaia to Ouargla. View overlooking the hamada about 28 km. from 



Ghardaia. The relatively abundant vegetation is associated with a 



light cover of sand over the area shown. The leading species are 



Aristida, Deverra, and Haloxylon. 

 PI. 19, fig. 43. Retama retam, in dunes about 58 km. from Ghardaia. 



44. Dates at the Bordj Zolfana, about 58 km. from Ghardaia — one of two 



wells encountered between Ghardaia and Ouargla. 



45. Ghardaia to Ouargla. View overlooking flood-plain of the Oued M'Zab, 



or a tributary of this oued. The adjacent upland is apparently with- 

 out plant life. 

 PI. 20, fig. 46. Vegetation on edge of the Oued M'Zab, about 63 km. east of Ghardaia, 

 showing habitat of Rhantherium adpressum in foreground. 



47. Sandy flood-plain of the Oued M'Zab, about 63 km. from Ghardaia. 



Retama, Genista, and Ephedra are the leading plants in this place. 



48. Habit of Ephedra alata in habitat shown in figure 47. This specimen was 



1.5 m. high. 



PI. 21, fig. 49. View of habitat of Ephedra alenda, 138 km. from Ghardaia. 



50. Detail of suckering habit of Ephedra alenda, from habitat shown in 

 figure 49. 



PI. 22, fig. 51. Vegetation, mainly Ephedra and Retama, of the western edge of the 

 Chott Mellala. 

 52. Approach to western edge of the Chott Mellala, showing characteristic 

 rounded hills, or mamelons. 



PI. 23, fig. 53. View between the Ouargla plain and the Chott Mellala, showing char- 

 acteristic appearance of eroded hills. 



54. Looking toward the Ouargla plain (reg). 



55. Shallow well about 25 km. north of Ouargla. 



PI. 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. 

 PI. 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. 

 PI. 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 arliculata, about 32 km. north of 

 Ouargla. 

 PI. 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. 

 PI. 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. 

 PI. 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. 

 PI. 30, fig. 68. Flood-plain of the Oued Hamman es Salahin, Biskra. Halophytes of 

 various species occupy the foreground. 

 69. Habitat of Phelypcea violacea shown in figure 70. 

 PL 31, fig. 70. Young shoots of Phelypcea violacea, at north base of Ed Delouatt hills, 



71. Habit of young specimens of Phelypcea. Except for about 15 cm., plants 

 were buried by sand. Biskra. 



