THE STEM. 49 



microscope. Draw one or two cells with their contents, 

 taking care to show details of structure. 



II. Examine in the same way sections from various 

 other underground stems, such as ginger, mandrake, etc. 



III. Prepare sections from pieces of a dahlia "tuber" 1 

 that have lain in commercial alcohol for some weeks. 

 Draw a few cells, showing the peculiar sphere-crystals of 

 inulin. 



IV. In some stems, as, for example, an onion bulb, sugar 

 is stored. This may be tested for in the way described by 

 Strasburger, Practical Botany, p. 48. 







MODIFIED STEMS. 



I. Make a thorough study of the common potato, ob- 

 taining for the purpose a number of different varieties. 

 What reasons are there for considering it a stem rather 

 than a root? What are the "eyes"? Where are they 

 most abundant? Are they all alike? Find where the 

 potato was attached. Draw an outline and indicate by 

 a dotted line the direction of growth in length. Does it 

 ever branch? Cut a transverse section so that it will 

 pass through a bud. Indicate in an outline sketch the 

 position of pith, wood, and bark. Notice that the wood 

 has been reduced to a minimum. It appears to the naked 

 oye as a faint circular line. 



Write a complete description, and discuss the mor- 

 phology of the potato. See Gray, Structural Botany, p. 59. 



II. Study a collection of other modified stems in the 

 same way, endeavoring in each case to satisfy yourself as 



1 This is really a root, but on account of its convenience it is selected 

 instead of a stem. 



