114 BRITISH PLANTS AT THE OASIS. ch. ,. 



before us a green shallow basin, at the farther end of which 

 our eyes rested gladly on the abundant foliage of gardens 

 and orchards. A stream from the Great Atlas, diverted 

 into numerous slender irrigation channels, is the source 

 of this apparent fertility, but so much of the water is 

 taken up in this way that only a trifling surplus remains ; 

 and, save after heavy rains, it seems that a mere streamlet 

 flows northward to join the Oued Tensift, the chief river 

 of South-western Marocco. The green that gladdened our 

 eyes seemed to have given but deceptive promise, for we 

 at first entered on a scrub formed exclusively of Cheno- 

 podicaeous bushes, including Arthrocnemum fruticosum, 

 Caroxylon articulatum, Suceda fruticosa, and Atriplex 

 Halimus. 



The same thing happens here that may be noticed in 

 the neighbourhood of the freshwater canal in the Isthmus 

 of Suez. Where the soil contains a quantity of soluble 

 salts, the first effect of admitting moistm-e by irrigation is 

 to form a salt marsh, which becomes covered with its own 

 characteristic vegetation ; but if the surface is so dis- 

 posed as to allow the percolation of fresh water, the salts 

 are gradually carried off, the salt marsh is converted into 

 fertile land, and the ugly Chenopodiacece disappear. 

 Accordingly, after traversing a broad belt of scrub, we 

 soon found ourselves amidst luxuriant vegetation, and 

 saw our tents, which had preceded us, pitched under the 

 shade of tall fig-trees, in one of the orchards belonging to 

 the village of Sheshaoua. This place is a true oasis, and 

 an abundant growth of fig, olive, pomegranate, apple, 

 plum, and apricot, with an undergrowth of grasses and 

 herbaceous plants, affords a striking contrast to the desert 

 tracts surrounding it. 



The vegetation of the irrigated land, excepting a few 

 tall palms, was almost exclusively European ; and not 

 without pleasure we gathered many common English 

 species, such as our common bramble, dandelion, charlock, 

 Sisymbrium Irio, Geranium dissectum, Hypochceris 



