BIOLOGY OF HIGHER SEED PLANTS 49 



they connected with the wood rays ? with the 

 ducts ? Do they have cytoplasmic and nuclear 

 contents ? What is the function of these cells ? 

 (6) Drawings. 



(a) Draw a small portion of the summer and spring 

 wood at the junction of the two in an annual 

 ring. Show the details of ducts and fibers. 

 (&) Draw the cambium and a portion of the phloem 

 and xylem on either side of it, including at 

 least two wood rays. Indicate the, orderly 

 arrangement of the tissues which arise from 

 the cambium. Draw the cells and tissues with 

 great accuracy. 



LONGITUDINAL SECTIONS 



Study thin longitudinal sections of the wood of oak, birch, 

 or a similar woody stem. See Fig. 53 of the text. 



1. Select a portion of your section in which you can demon- 



strate most clearly the following main wood tissues in 

 long section : namely, ducts, fibers, living cells, and 

 wood rays. 



2. Study and draw accurately the above tissues of the wood 



in long section. Indicate in each tissue the relative 

 thickness and cell- wall markings, the nature of the cell 

 contents if present, and the shape of the cells com- 

 posing the tissue. 



3. Observe the form and structure of the cambium cells and 



the phloem cells, consulting the text figure. These 

 tissues are usually too difficult for accurate delineation 

 by beginning students. 



