II. A GENERALIZED PLANT (Spirogyra) 



A. Naked-eye Characters: 



1. Carefully take a small bit of this plant between the 

 thumb and fingers and note its "feel." Suggest 

 why it is sometimes referred to as "green silk." 



2. Carefully lift up some of the material with a needle, 

 and describe the form of the plant. How many 

 centimeters long are the longest filaments you can 



% observe? 



3. Can you detect any evidences of a differentiation 

 of the plant into shoot (i.e., stem and leaves) and 

 root ? 



B. Microscopic Characters: 

 i. The plant as a whole. 



(a) Mount two or three filaments in water. 



(b) Note that the filament is composed of separate 

 structural units, placed end to end. These 

 units are cells. 



(c) Are the filaments more than one cell thick? 

 Do they branch? Are they of uniform diame- 

 ter? Compare the length of the various cells 

 with each other. Compare the shape of the 

 end cell with that of the others. What is the 

 shape of the filament as seen in imaginary cross- 

 section? Very careful focussing is necessary in 

 order to answer this question correctly. 



(d) Accurately measure the length (in millimeters) 

 of a piece of filament lying straight under the 

 cover-glass, then count the number of cells in 



ii 



