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Fig. 35. Root-habit of a mature specimen of Peganum harmala, from the Boor of the M'Zab Valley 

 near Ghardaia. The soil at the place is comparatively deep. (See text for further explanation.) 



Fig. 36. Root-systems of Helianthemum sessiliflorum (right), Haloxylon articulatum, and Nolletia 

 chrysocomoides (left), from the flood-plain of the Oued M'Zab, Ghardaia. 



