A. LEUCOPHYLLA — A. PENTANDRA. 



293 



separated from the ancestral line during its northward migration. A close study of forms 

 in Lower California and on the mainland of western Mexico may bring further evidence 

 to bear on this question. 



ECOLOGY AND USES. 



Atriplex leucophylla may constitute the pioneer consocies on the strand just beyond the 

 reach of the waves, or it may form dunelets in moving sand farther back. It grows alone 

 over much of its zone, but behind it is associated with Abronia marilima, A. umbellata, 

 Franseria bipinnatifida, Mesembryantheum nodiflorum, or Dislichlis. The prostrate 

 woody stems and the numerous erect branches enable it to resist erosion, and to accumu- 

 late wind-blown sand in small amounts. It is a marked halophyte, as indicated by its 

 habitat, and the dense scurf of leaves and stems. The flowers appear from April to 

 October. 



No uses are known for this plant, though it is doubtless an occasional cause of hay- 

 fever. 



Lvs. broadest above Lvs. broadest below 



the middle, lower the middle, green on 



surface white; bracts both sides; bracts 



2-jmm.long,reticu- 2-2.5 '"'"■ 'ongi "°* 

 late \ reticulate 



Perennial; lvs. 



long, nearly 



linear, under o.4cm. 



wide, entire, gray 



beneath; bracts :-2 S mm. long 



Bracts globoid, Bracts compressed, 

 ^-A mm. long, not 2.5-5 mm. long, 

 nerved v /^-nerved 



Perennial; lvs. 

 entire ; bracts 5-7 

 long ; seeds large, 

 (2.5-3 mm. long) 



Perennials; lvs. entire, reduced 



(0.5-2 cm. long, under 0.5 cm. wide)j 



(Californian) 



Fio. 39. — Phylogenetic chart of the Atriplex ptnlandra group. 



