116 CREEPING PLANTS [CH. 



new tufts of leaves, or to throw up new stems in compara- 

 tively unoccupied ground, and most plants which put out 

 these travelling shoots prove themselves advantageously 

 endowed by the facility with which they spread them- 

 selves rapidly over large areas and even dispossess others 

 already in occupation of the soil. This is well exemplified 

 by the garden Hawkweeds which rapidly infest a whole 

 bed by means of their creeping stolons above ground, or 

 by species of Equisetum which will do the same thing by 

 means of their underground rhizomes. 



Taking the super- terranean shoots first, their nature is 

 always easy to understand, because they have definite 

 nodes and internodes and develope ordinary leaves from 

 the former, and often, as is well seen in the runners of the 

 Strawberry, put out roots from the nodes which enter the 

 soil direct. 



Differences are observable in these creeping shoots 

 according as they are annual or perennial, and primary 

 or accessory structures. Thus, in the creeping Willows, 

 of which our Salix repens is a common example, and of 

 which many species exist in high latitudes, the prostrate 

 stems are perennial and woody and are the only ones 

 formed by the plant, remaining for years connected to the 

 original centre ; many Potentillce and Labiate plants 

 behave similarly. In other cases the older parts behind 

 die off after a year or more, as in many Clovers, the 

 Periwinkle, the creeping Lysimachice (L. Nummularia, 

 L. nemorum) and many Saxifrages and Hawkweeds. In 

 these cases the lengthening internodes drive the terminal 

 parts forward year by year, and these root, while the 

 hinder parts perish, so that each year the current plant is 

 developed further and further away from the parent centre, 

 and becomes independent by the dying off of the hinder 

 parts of the creeping shoots. 



