CH. V. SAHARA VEGETATION. 109 



soon after five a.m. — the thermometer marked only 54° 

 Fahr., but by six a.ji. it reached 67°. The observation for 

 altitude gave 1,132 feet (345"5 m. ) above the sea ; probably 

 too low by fifty or sixty feet, owing to the local effect of 

 radiation in depressing the temperature of the air in 

 contact with the surface. 



We were on our way soon after six; and, on leaving 

 behind the bushes and small trees that grow on the skirts 

 of the irrigated groimd, we entered on a wide bare plain, 

 stretching unbroken as far as the eye can reach, which 

 forms the most singular feature in the aspect of this part 

 of Marocco. The surface is covered with calcareous rough 

 gravel, mixed in places with siliceous concretions. The 

 scanty vegetation was already nearly all dried up, and it 

 was not without difficulty that we secured specimens of 

 most of the few species that can endure the parching heat 

 and drought. Conspicuous among these was Peganum 

 TIarmala, forming at intervals green patches amid the 

 general barrenness. Stipa tortilis was frequent, but 

 mostly dried up, and here and there occurred tufts of 

 a meagre variety of Avena barbata. More interesting 

 than these were a diminutive annual species of Echium 

 (E. modestum, Ball) and two species of Centaurea — one 

 hitherto known as Rhaponticum acaule of Decandolle, 

 the other, before undescribed (C. maroccana, Ball). In 

 its general aspect, and in the character of its vegetation, 

 this region bears a striking likeness to the stony portions 

 of the Sahara, and we were not sorry to include this among 

 our Marocco experiences, though weU pleased that the 

 acquaintance was not to be much prolonged. 



Some six or seven miles east of Ain Oumast we passed 

 a short way north of Sidi Moktar, the tomb of a saint 

 much venerated in this region, and the last spot where for 

 a long distance water is to be found at all seasons. This 

 is one of the halting-places, called Nzelas, frequented by 

 ordinary travellers who follow this road. The Nzela is one 

 of the peculiar institutions of this country deserving of 



