5O PLANT BIOLOGY 



uous stems. These so-<alled stemless plants die to tlie 

 ground every year. 



Stems are erect when they grow straight up (Figs. 53, 

 54). They are trailing when they run along on the ground, 



FIG. 53. STRICT SIMPLE 

 STEM OF MULLEIN. 



FIG. 54. STRICT UPRIGHT SUM 

 OF NARROW-LEAVED DOCK. 



as melon, wild morning-glory (Fig. 55). They are creep- 

 ing when they run on the ground and take root at places, 



FIG. 55. TRAILING STEM OF WILD MORNING GLORY ( Convolvulus arv ensis) . 



as the strawberry. They are decumbent when they lop 

 over to the ground. They are ascending when they lie 

 mostly or in part on the ground but stand more or less 

 upright at their ends; example, a tomato. They are 



