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called in this case, thallus ? "What is the color of 

 the thallus? Does the color vary in different 

 places ? Does the plant apparently contain chlo- 

 rophyll ? Place a plant in sixty per cent, alcohol 

 for a few hours. What change in the color of the 

 alcohol ? In the plant ? Is the plant of sufficiently 

 firm structure to stand upright by itself? Can 

 you distinguish an upper and a lower side on the 

 thallus ? The plant consists of an attached por- 

 tion or disk, from which proceeds the stem, the 

 latter dividing into flattened branches. 



h. The disk. — Shape of the disk? In structure which 

 does it resemble the more closely, the stem or the 

 branches ? By what means is the disk attached ? 

 Is it very firmly attached ? Is the plant attached 

 by any other part than the disk? Do you ever 

 find more than one stem growing from the same 

 disk ? Is the disk merely an organ of attachment, 

 or does its appearance warrant regarding it an or- 

 gan of absorption, or root, as well ? 



c. The stem. — Where does the stem begin 1 Is 



there any sharp distinction between disk and 

 stem ? What is the shape of the stem ? Does it 

 on its lower part bear any wing-like expansions ? 



d. The branches. — Trace the branches of the stem 



up into the expanded portions or branches of the 

 thallus. Here they form the midribs of the flat 

 branches. How do you distinguish the midrib 

 from the other parts, wings, of the branch? 

 What part of the branch does the midrib occupy? 

 Does each branch have a midrib ? If so, does it 

 extend to the end of the branch? Note the 



