54 BOTANICAL FEATURES OF THE ALGERIAN SAHARA. 



Ghardaia, close examination revealed the presence of many living perennials 

 as well as the remains of the previous annual flora. This plain, the Gantara, 

 of wide extent, is the most arid region seen in southern Algeria. Massart 

 estimates that there is an average precipitation of 15 cm. on the desert, 

 but, from data previously cited, it would appear that this amount is rarely 

 attained; indeed, several months, or even two or more years, may pass 

 without any rainfall whatever. When one searches the hollows he finds a 

 few small perennials; plants are almost wholly absent on the low ridges. 

 But in some areas on the plain, where superficial examination does not 

 show any plants, a surprising number were found. For example, on the 

 level hamada, 96 kilometers from Ghardaia, on an area 16 meters square, 

 389 living plants were found, but only 24 were so large as to be seen from 

 a distance; all were either eaten badly or trampled to the ground, so that 

 it could not be learned what the flora of the area might have been had no 

 animals interfered with its full development. 



After leaving the 96 kilometer station the perennials were seen to dimin- 

 ish rapidly in numbers and to decrease in size, until the ridges of the low 

 undulations were absolutely without plants, and there were but few in the 

 hollows. There was no apparent change in the character of the hamada 

 or in that of the soil. This sterile condition persisted for 26 kilometers, 

 when vegetation similar in character to that previously seen was again 

 encountered. The zone of better vegetation lasted for 3 kilometers, when 

 the country became barren once more, which condition lasted for 10 kilo- 

 meters. The presence of barren belts on the Gantara, where the plants at 

 the best are insignificant in size as well as number and without change in 

 topography or soil, points to an especially arid belt. This conclusion is 

 further strengthened by the observation that the plants found were rela- 

 tively of very small size.* 



The flora was also sparse upon the route followed by Massart across the 

 Gantara, which was apparently somewhat farther to the north than the one 

 now being described. He mentions having found Argyrolobium uniflorum, 

 Astericus graveolens, Fagonia microphylla, Deverra chlorantha, Fagonia gluti- 

 nosa, Halogeton alopecuroides, Helianthemum sp., and Hemiaria fruticosa. He 

 says that Deverra is one of the rare glabrous forms on the hamada. It is 

 said to have the odor of parsley, and the Arabs have a belief that camels 

 which eat it become blind, but Massart's camels were not injured by eating 

 the plant. 



As we drew near the Chott Mellala, on the eastern edge of the barren 

 zone mentioned in the preceding paragraph, we suddenly encountered a 

 belt of Ephedra alenda, stretching to the north and to the south as far as 



* In the case of annuals the differences in development of the shoot between plants 

 well watered and those with only a meager supply are very striking. In one instance 

 in the Tucson region specimens of Parietaria debilis growing in extreme conditions, one 

 moist and the other arid, varied in length between 39 cm. and 8 mm., or a difference 

 with a ratio of 49 to 1. (Root Habits of Desert Plants, loc. cit.) 



