46 A TEXT-BOOK OF BOTANY 
especially on sterile and exposed soil, and there may be an 
important relation between this fact and their habit. In 
such stems there is a distinct disadvantage in the display 
Fic. 45.—Prostrate stem of Potentilla. 
of leaves as compared with erect stems; for instead of being 
free to spread out leaves on all sides, one side is against the 
ground, and the free space for them is diminished at least 
one-half. All the leaves such a stem 
bears are necessarily directed toward 
the free side. 
. Fic. 46.—A strawberry-plant, showing a runner that has 
developed a new plant, which in turn has sent out an- 
other runner.—After SEUBERT. 
We may not know all the reasons why so unfavorable a 
position for leaf display is assumed; but among the results 
are protection in exposed situations in some cases, and the 
