GHARDAIA TO OUARGLA — VEGETATION. 55 



could be seen (fig. 49). On one side was the barren zone, on the other the 

 immense plantation. Upon examination it was found that the Ephedra 

 was the only species of perennial. It had several points of interest, but 

 the short time at our disposal precluded more than a superficial examina- 

 tion. Usually keen about the desert species, it is curious to note that the 

 Arabs appear not to recognize this, called by them "alenda," as being re- 

 lated to the larger species of Ephedra with which they are well acquainted. 

 It is a small species, growing from 30 to 40 cm. high. It does not occur 

 singly, but has the habit of growing in groups of a half dozen or more. 

 Between the Ephedra colonies were only the dried remains of the annual 

 flora of the last rainy season. An examination of the root-system of the 

 species showed that, like other species of the genus, it has a well-developed 

 tap-root (fig. 50). 



Alenda, however, has a root-habit which, although not peculiar to it, is 

 at least very striking and of great importance to its survival. From the 

 root-crown a stolon arises which extends away from the parent for a distance 

 of about a meter. From this stolon there arise shoots which develop into 

 daughter plants. Through this method of reproduction the small colonies 

 of the species are formed and possibly the species mainly multiplied. From 

 the stolons small roots arise, giving aid to the mother root in providing the 

 offspring with moisture. This habit is very like that of Kceherlinia spinosa 

 of the Arizona desert, which has a similar type of root-system and which 

 reproduces vegetatively in a similar manner. Alenda continued to be the 

 dominant species until near the edge of the big chott (Mellala), a few kilo- 

 meters east of where it was first seen. 



Practically no plants were seen when descending through the eroded 

 portions of the hamada to the floor of the chott (fig. 52), but on reaching 

 the bottom of the great chott a surprisingly large number was observed, 

 including Anabasis articidata, Aristida pungens, Ephedra alaia, Limonias- 

 trum guyonianum, Retama retam, and Traganum nudatum (fig. 51). In the 

 wide central part of the chott, where the salts are perhaps most dense, 

 there are no plants; but on the eastern side are Euphorbia guyoniana, 

 Anabasis articidata, and Zygophyllum sp. These small species were grow- 

 ing far apart and were badly injured, either by being trodden under foot 

 or by being eaten by the passing animals. To the south of where we 

 crossed the chott and also to the north the sand mountains arise. After 

 leaving Chott Mellala we ascended gradually to go over a low pass sepa- 

 rating it from a small chott to the east. Here we obtained a backward 

 view of the sand mountains, low as seen from the pass, with sharp, wind- 

 made ridges, and bearing a few specimens of Aristida pungens. Descend- 

 ing somewhat, another but smaller chott was crossed. Between the latter 

 chott and the Ouargla plain the plants were very few and confined to the 

 slopes and the higher ground, avoiding almost wholly the depressions. Of 

 those recognized, Tragommi nudatum was the most abundant. This is the 



