276 THE BIOLOGY OF THE PLAIJT 



"wise consist of nodes and internodes ? What 

 relation exists between the appendages and the 

 nodes ? What variations in the length of the in- 

 ternodes do you find ? Put a piece of the lower 

 portion of a plant into dilute hydrochloric acid. 

 What result ? Try the tip end. Do you get the 

 same result? Compare with the similar experi- 

 ments on the exoskeleton of the lobster and on 

 the mussel sheU. 

 Make a drawing, showing the last six internodes and 

 appendages. 



Microscopic Structure. 

 a. The stem. — With the hand-lens examine one of 

 the upper -internodes in water. Notice the elon- 

 gated cells running in a spiral from the base to 

 the apex of the node. How many turns does the 

 spiral make ? Does the internode have any out- 

 growths ? Lay the same specimen on a slide and 

 examine under the low power, using no cover- 

 glass. Can you now trace the course of the spiral 

 cells ? Is each one continuous from one node to 

 the next ? If not, do you find that each spiral is 

 made up of the same or of different kinds of 

 cells ? If the latter, how many kinds do you 

 find, how do they differ from one another, and 

 how are the various kinds arranged? Examine 

 the lower portion of the stem and compare with 

 the upper. 

 Draw two or three segments of the stem. 



Hold a piece of a fresh or preserved stem be- 

 tween two pieces of pith, and with a sharp razor 

 cut thin transverse and longitudinal sections 

 through nodes and internodes. With a pipette 



