vi LIST OF ILLUSTRATIONS. 



PI. 31, fig. 72. Asphodelus sp. at north base of Ed Delouatt hills, Biskra. Photographed 



in March. 

 PI. 32, fig. 73. Detail of square No. 1, on low hills north of Biskra. 



74. Vegetation of north slope of the low hills which are north of Biskra. 

 Ferula vesceritensis is the perennial appearing in the figure. 

 PI. 33i fig- 75- Detail of square No. 2, near area shown in fig. 74. Ferula and Haloxylon 

 are leading species. 



76. Root-habit of Haloxylon scoparium, from a wash near Biskra. 



77. Young shoots and mature roots of Ferula vesceritensis. North of Biskra. 

 PL 34, fig. 78. Root-habit of Fagonia growing on edge of a wash. Biskra. 



79. Large lateral root of Haloxylon, with numerous deciduous rootlets, no 



longer functional. 



80. Shoot-habit, taken from above, of Fagonia from the flood-plain of a 



small oued near Biskra. 



PI- 35. fig- 81. Spring annuals, March 17, on north slope of the Djebel Bou Rhezal, 

 Biskra. 

 82. Root and shoot habit of Peganum harmala, Biskra. The main root is 

 especially well developed, although the species has a generalized 

 root-system. 



PI. 36, fig. 83. Annuals growing with Peganum, near Biskra. 



84. General view of the north face of the Djebel Bou Rhezal, Biskra. Appar- 

 ently barren, plants are rather numerous in the rock crevices and 

 small washes of the mountains. 



