94 NATURE OF PROSTRATE STEMS 



become separate plants by -the decay of the old stem, as in 

 the strawberry, gill-over-the-ground, cinque foil, etc. These 

 new plants repeat the mode of growth of the parent plant and 



FIG. 69. Hotise leek forming buds at the end of short branches or stolons. 



in this way many prostate stems spread out over the soil, estab- 

 lishing new plants in wider and wider circles. If you will ob- 

 serve the number of new plants established and the distances 

 traversed by some of these creeping stems each year you will 

 see the reason for the common occurrence of the large mats and 

 colonies of plants with prostrate stems. 



47. The Rhizome Type of Stems. In a third type, the stems 

 have become so modified that they respond to the various stimuli 

 in quite a different way from the forms noted above. They 

 creep along in the soil and frequently resemble .roots more than 

 stems. For this reason they are called rootstpcks or rhizomes. 

 They are, however, real stems, as is attested by the numerous 

 leaves and often erect branches that spring from their nodes 

 as seen in the ferns, sweet flag, cat tail, grasses, etc. Plants of 

 this type are well protected against drought, cold, and fires, and 

 like prostrate stems they are adapted to establishing new plants 

 as is apparent in grassy meadows, colonies of golden-rod and 

 daisies or reedy banks of cat tails, sedges, etc. These stems 

 are also well adapted to propagating new plants because they 

 generally serve as storage organs for food and are therefore 

 often of a fleshy character (Fig. 70). For these reasons it is 

 sometimes very difficult to eradicate plants of this type. This 

 is very well illustrated in the quack grass, often a troublesome 

 pest in cultivated land. Plowing and hoeing only serves to 

 break up the rhizome into numerous parts each of which may 



