FULL-GROWN PLANT AND ITS PARTS 49 
stand erect, but are between erect and prostrate stems. 
Some ascend; that 1s, the end of the stem arises some- 
what from the ground, although the rest of it may be 
prostrate. Zhese are ascending stems. Others topple 
over so that the end is turned toward the ground. 
They are downward bent (decumbent). 
Burrowing stems. ‘Then there are stems which 
burrow, as it were. They creep along under the sur- 
face of the ground, the bud pushing or burrowing along 
as the stem grows. The iris, Solomon’s seal, and 
the common bracken fern are well-known examples. 
The iris and Solomon’s seal, and some others, as you 

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Fic. 78. Burrowing type, — the bracken, — a “‘ rhizome.” 
know, form each year erect stems which rise above 
the ground. Stems which burrow along under the sur- 
face of the ground are called rootstocks, or rhizomes, 
which means root form. ‘They are known from roots 
