118 



Study the wedge-shaped bundles out of which the first 

 annual ring is formed. 



Note how the medullary rays arise from the pinching of 

 the pith between the expanding wedges of wood. Note 

 the difference between that part of the ring which is formed 

 in spring and the part which is a later growth. In which 

 part are the wood ducts larger? What is the probable 

 reason for the difference ? Draw a portion greatly magnified. 



Read the chapter on woody stems in any textbook of 

 botany and endeavor to find as many structures as possible. 



Note. The study of the minute structure of monocotyl and 

 dicotyl stems is exceedingly difficult. The teacher's assistance is 

 demanded at every point, and the use of texts and charts will greatly 

 aid the beginner. 



Prepared microscopic mounts are better than fresh material on 

 account of their greater thinness and the effect of staining reagents. 



Exercise 



Select good specimens of the two types of stem and 

 compare them part by part. 



Cornstalk is the best common monocotyl stem, and some 

 thrifty dicotyl like the ailanthus is very good for comparison. 

 Tabulate your observations as follows : 



