MARCHANTIA POLYMORPHA 93 



(/) In the cells of a gemma do you find chloroplasts ? 

 A nucleus? Oil drops? 



(g) Note the larger cells with clear contents from 

 which the rhizoids will develop. Do they con- 

 tain chlorophyll? 



(ti) Make a drawing 50 mm. in diameter, showing 

 all the features observed under D, 2 . 



(i) Draw the outline of an imaginary cross-section 



passing through the center of a gemma. 

 3. Thethallus. 



(a) Under high power study the surface cells and 

 air-pore. How many guard-cells are there? 

 Compare the air-pores of Marchantia with the 

 stomata of a foliage-leaf of a higher plant, and 

 of the moss and fern. Are they true stomata? 



(b) Study cross-sections of the plant mounted in 

 clearing fluid. 



(c) The careful study of the structure of the foliage- 

 leaf, already made, makes it unnecessary 

 to give detailed directions for these observa- 

 tions. Frame your own questions, to be 

 answered by observing the mounted section. 

 Note especially whether the tissues are differ- 

 entiated, and, if so, compare with a foliage-leaf 

 in this respect. 



(d) Look for sections passing through air-pores, 

 and compare their structure with that of the 

 stomata of the leaf. What causes the surface 

 appearance of the margins that delimit the 

 areolae? 



(e) Describe the place and mode of origin of the 

 rhizoids; of the cupules. 



(/) Is the thallus of the same thickness throughout? 

 (g) Describe the chloroplasts. In some of the 



