190 
PLANT STUDIES 
drouth it is very com- 
mon for plants to 
diminish the exposed 
surface in a very de- 
cided way. In such 
cases there is what 
may be called a peri- 
odic surface decrease. 
For example, annual 
plants remarkably 
diminish their ex- 
posed surface at the 
period of drouth by 
being represented 
only by well-pro- 
tected seeds. The 
whole exposed sur- 
face of the plant, 
root, stem, and leaves, 
has disappeared, and 
the seed preserves the 
plant through the 
drouth. 
Little less remark- 
able is the so-called 
geophilous habit. In 
this case the whole of 
the plant surface ex- 
posed to the air dis- 
appears, and only 
underground parts, 
such as bulbs, tubers, 
etc., persist (see Figs- 
45, 46, 66, 67, 68, 
69, 70, 75, 144, 168, 
169). At the re- 
FIG. 168. The bloodroot (Sanguinaria), showing 
the subterranean rootstock sending leaves and 
flower above the surface. After ATKINSON. 
