CHAPTER X 



THE STEM — ITS GENERAL STRUCTURE 



There are two main types of stem structure in flowering 

 plants, the differences being based on the arrangement of 

 bundles or strands of tissue. These types are endogenous 

 and exogenous (page 20). It will require patient laboratory 

 work to understand what these types and structures are. 



Endogenous, or Monocotyledonous Stems. — Examples of 

 endogenous stems are all the grasses, cane-brake, sugar- 

 cane, smilax or green-brier, 

 palms, banana, canna, bam- 

 boo, lilies, yucca, aspara- 

 gus, all the cereal grains. 

 For our study, a cornstalk 

 may be used as a type. 



A piece of cornstalk, 

 either green or dead, should 

 be in the hand of each 

 pupil while studying this 

 lesson. Fig. 69 will also 

 be of use. Is there a swelling at the nodes.' Which 

 part of the internode comes nearest to being perfectly 

 round .' There is a grooved channel running along one 

 side of the internode : how is it placed with reference to 

 the leaf ? with reference to the groove in the internode 

 below it .'' What do you find in each groove at its lower 

 end? (In a dried stalk only traces of this are usually 

 seen.) Does any bud on a cornstalk besides the one at 



Fig. 69.'— Cross-section of Corn- 

 stalk, showing the scattered fibro- 

 vascular bundles. Slightly enlarged. 



