^ ^.rr 



'jT rif:>..r 



28 \'.(>-\.\):\<:\\. FEATUKES OJ THE ALTiEWAN SAHARA. 



\/ " ' ■""'- that Hoe spedes has a t/>;> ' i-cting of severe riiooto, sprmg- 



jr M? root-crown at the level ^ ^ ^ound, and a root-system in 



rrals and the main root are aKkc well developed. In order 



t: ., already estabHdied, can maintain this geaersl relation dtiring 



t? in^ up of the sand, the main rrx^t must grow at the crown as fast 



'! encroaches. This is exactly what happens, so that, when the 



1 on^ the shoot of the species is elevated for a ^pace equaling 



uui any,:. (A irus aand^ which is half a meter or more. From the probability 



that Acanihyllis is of very slow growth and that the dunes ar*^ lov/, it follows 



that thf; raV; of diin^ movement must be slow. 



TIf. AEOf;T LAGHOUAT. 



ran Atlas lie to the north of La^iouat, 

 wii/ur. v rge (the Nomad Mountains) is not 



...otmtains extend both to the west and 

 " -'!«ated. There are also two higji, 

 , the town lying between, and it 

 he water is forced to the surface, 

 The hill to the west of the 

 ^ <^>n the south side of the Nomad 



Mounta: / m; the south face of these moun- 



tains is 'Au^j AiiTuiA, r , \Axt on the northern face the slope 



is gradual anrl ' h rocks arc abundant. 



Tv". ■'"'•■'. <,..>j >.: ..J /.ri tains were seen. One was in a 



pan * ' '^h cara . -. . ;] en rcMte to Lagbouat, from the High 



Platf: ore diV.'i.r»t T^;M: the second to the east of the pass 



ismtr ' rj physical plant conditions appeared 



V. in hx/th \(jf:ni\(fr. . '..<■. ajiT^/roa/^^ the mountains from 



the Bouth t; plant iintil on the south face they 



quite diimpix;ar, but on attainir i they quickly increase and form 



a not: " ' ' ' nt in '' ' Jn fact, the flora of the nort,hr:ni 



gentl'. '; the ar<i relatively favorable, is much 



richer --- .. ^ '-•'''' ff- '' •^': RhruV^fl U^^m of good size 



they would ' . 



A certain area on the nf/riYi ' of the Nomad Mountains, not far 

 from the pa^^a through v/hich tl/ ' I zi goes, was selected for making 



*The mott striking diaoge to the general character of the vegetation which the 

 travd^ flotioes as he goes from the less arl^ to the mrjr«: arid porttc«ijof southern Algeria 

 ts its decrease in amount, lliis occurs through dwarfing effects of whatever cause and 

 through a decrease in the number of individuals. Within certwn limits the results 

 observed are to be attributed mainly to the first of these, since there is often a sur- 

 pri«ngl/ large nurntx&r of perennials on any given area. But in other and more intensely 

 arid regions (as pcntio' ■ ' ^ ^ht Arabian -Bg^yptian Aneti, and indeed a limited area on 

 tYub hstmadA hetweea'^ . and Ou;ir;$bij plants are wh<»lly wanting. Whether such 



is generally the case on the tea or the hamH/in. tanhfzr south in southern Algeria is not 

 known. 



