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 



FIG. 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. 



FIG. 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 



