BIOLOGY OF HIGHER SEED PLANTS 45 



annual rings, and spring and summer wood as 

 they appear in transverse, longitudinal, radial, and 

 tangential sections. Indicate ducts by circles, 

 summer wood by shading. Label these structures 

 in each view of the block drawn. 



PRACTICAL EXERCISE 



Study the various cuts of finished woods represented in the 

 finished woods in the tables, doors, and other wood furnishings 

 in the laboratory. See Figs. 48 and 50 of the text and the discus- 

 sions concerning the structure of finished woods. 



1. Determine the different cuts of wood, namely, the radial, 



tangential, and transverse cuts, represented in the finished 

 woods of the laboratory. 



2. Determine annual rings, heartwood and sapwood, u grain," 



"silver grain," etc. in each of the above cuts. 



3. Make sketches of the above structures in transverse, radial, 



and tangential sections of different kinds of finished 

 woods. Label all structures indicated in your drawings. 



MICROSCOPIC STRUCTURE OF WOODY STEMS 

 TRANSVERSE SECTIONS 



Observe transverse sections of shoots which are more than 

 one year old. Use only hand lens and low power in your first 

 studies. In preparations which have been stained with a red 

 dye (safranine) the wood and the thick-walled skeletal tissues 

 are stained red. The remaining tissues are usually stained purple 

 or blue with logwood dye (heematoxylin). 



1. General tissue layers in sections of living shoots. 



a. The bark. Note the limits of the layers designated as 

 brown bark and green bark in sections of fresh twigs. 

 Can you distinguish the epidermis and the brown 



