416 BOTANICAL GAZETTE [NOVEMBER 
proportion would be heightened if a number of herbaceous peren- 
nials with woody bases or stocks were included. This ligneous 
character is not confined to the lava flow plants, however, nor is 
Fic. 22.—Typical ligneous thorny species dominant in xerophytic habitats, on 
lava flows and coastal plains, Acacia Farnensiana; man is standing on explosively 
produced tufa strata. 
