STEMS AND STEM STRUCTURE 39 



3. What has the mode of branching to do with the arrangement 



of the leaves ? with the position of the flower-bud scars ? 

 24. Twig of poplar. 



A. Sketcli a vigorous young twig of poplar for of liickory, 

 magnolia, or tulip tree) in its winter condition, noting par- 

 ticularly the respects in which it differs from the horse- 

 chestnut. Describe in writing any facts not shown in the 

 sketch. Notice that the buds are not opposite, nor is the 

 next one above any given bud found directly above it, but 

 part way round the stem from the position of the first one. 



B. Ascertain, by studying several twigs and counting around, 

 which bud is above the first and how many turns round the 

 stem are made in passing from the first to the one directly 

 above it.^ 



C. Observe with especial care the difference between the poplar 

 and the horse-chestnut in mode of branching, as shown in a 

 large branch provided for the study of this feature. 



STRUCTURE OF THE STEM 



Stem of Moxocotyledoxous Plants 



25. Gross structure of the corn stem.* * Refer to the sketches of 

 the corn seedling to recall the early history of the corn stem. 



A. Study the external appearance of a piece of corn stem or 

 bamboo two feet or more in length. Note the character of 

 the outer surface. Sketch the whole piece and label the 

 enlarged nodes and the nearly cylindrical internodes. 



B. Cut across a corn stem and examine the cut surface with 

 the lens. iSfake some sections as thin as they can be cut 

 and examine with the lens (holding them up to the light) 

 or with a dissecting microscope. Note the firm rind com- 

 posed of the epidermis and the underlying tissue, the large 



1 This may be made clearer by winding a thread about the twig, making it 

 touch the base of each bud. 



