58 PLAlsT STUDIES 



certainly one of protection, and it has a further advantage 

 in the way of migration and vegetative propagation. As 

 the stem advances over the ground, roots strike out of the 

 nodes into the soil. In this way fresh anchorage and new 

 soil supplies are secured ; the old parts of the stem may 



'^ 



''^■ 



Fig. 48. Two plants of a saxifrage, showing rosette habit, and also the numerous 

 runners sent out from the base, which strike root at tip and produce new plants. 

 —After Keener. 



die, but the newer portions have their soil connection and 

 continue to live. So effective is this habit for this kind of 

 propagation that plants with erect stems often make use of 

 it, sending out from near the base special prostrate branches, 

 which advance over the ground and form new plants. 

 A very familiar illustration is furnished by the straw- 

 berry plant, which sends out peculiar naked '^ runners'' 

 to strike root and form new plants, which then become 



