180 



STEMS 



ground stems, being the kind of underground stem most common 

 among Grasses and weeds. Many wild plants, such as the Ferns, 

 May Apple or Mandrake, Solomon's Seal, Iris, Water Lily, and 

 others, have rhizomes. (Fig. 156.) 



Fig. 156. — Rhizome of the Mandrake (PodophyUum), showing aerial 

 shoot and two scars (a) left by previous shoots. 



One striking feature is the difference in the way that rhizomes 

 and their aerial shoots respond to gravity and light. While their 

 aerial shoots grow toward the light and away from the earth, the 



