From what has been said regarding the large numbers of domestic animals that gain their entire living on the desert, it follows that of plants growing within the range of the flocks only such as are poisonous, distasteful, armed, or otherwise protected, escape partial or complete consumption. Only such species as are too small for fuel or can not be eaten by animals attain to the usual development year by year. In the vicinity of Laghouat the most prominent of the immune plants is the quedad (_Acanthyllis tragacanthoides_), which is well protected by its stout spines; and even this species is not wholly undisturbed. The jujube, also, although not common here, is provided with short spines. It is stated by Massart[13] that the camels used by him, not having eaten for five days, consumed the branches of the jujube in spite of the spines, and that _Anvillea radiata_, a composite with acrid juice, was passed by. Perhaps the plants most frequently eaten are of the genus _Haloxylon_, generally distributed from the High Plateau southward into the region of the M’Zab. That this genus is not exterminated is interesting, since it is rarely permitted to come into flower and fruit, and it appears not to reproduce to any extent, if at all, in a vegetative way. =FROM LAGHOUAT TO GHARDAIA.= REGION OF THE DAYAS. From Laghouat the way lay through a gently rolling country, ever dipping to the south and southeast. No mountains relieved the monotonous horizon. “A hard stony desert alternated with rolling sandhills,” followed by a “vast level plain dotted with dayas,” to quote again from Tristram’s narrative. Somewhat to the south of Laghouat depressions are met here and there, separated from each other by the low ridges of the plain, which receive the drainage each of a limited territory. (See figs. 10 and 11.) These are dayas, and are in fact oases with an uncertain water-supply but with favorable soil conditions, so that such rain as falls on them, or is conducted to them from higher ground, sinks deeply and creates relatively favorable conditions for plants. In that the daya is the center of a drainage system, and has no visible outlet, it is comparable to the chott or salt-spot, but it is to be distinguished from the chott by the absence of salts in excessive amounts. That salts are not present in the dayas in quantity is probably due to subterranean drainage, the daya being in fact similar to the bolsons of western America. On the plain in the northern portion of the daya region the following may be observed:[14] Echinops spinosus. Acanthyllis tragacanthoides. Thymelæa microphylla. Peganum harmala. Euphorbia guyoniana. Citrullus colocynthis. Artemisia herba-alba. Artemisia campestris. Haloxylon articulatum. Anabasis articulata. Teucrium polium. Aristida obtusa. Stipa gigantea. Noæa spinosissima. Asteriscus pygmæus.