78 
THE FIRST BOOK OF BOTANY. 
another plant and compare the root and stem in the 
same way. Do yon find the same differences ? Com¬ 
pare the root and stem of a great many plants, and 
see if the differences you first noted are not always 
found. 
You may perhaps find parts of plants under ground 
that bear buds or are a sort of bud; but they are not 
common, and they are not roots. By-and-by, when 
you have studied the mode of growth of plants, you 
will find further differences between root and stem, 
but for the present you may know stems from roots 
by the presence of buds upon them. 
Look at a potato that has begun to sprout. Can 
it be a root ? It is a thickened portion of an under¬ 
ground stem, and botanists call it a Tuber. In Fig. 
Fig. 118. 
Tuber. 
118 you can see the nodes of this underground stem. 
Observe that roots are given off at these nodes the 
same as in the creeping stem shown at Fig. 104. 
Look for examples of roots given off from the nodes 
of stems that grow only above ground. 
