120- TYPE STUDIES 



B. Structure of the thallus. 



1. Examine the upper surface with a hand lens. Draw a 

 portion showing the diamond-shaped areas, each with a 

 central pore. 



2. Cut cross sections in pith and compare the cell structure 

 of the upper and lower surfaces. Note the air chambers, 

 opening to the outer air through the pores, and containing 

 branching filaments of ovoid cells with large and numer- 

 ous chloroplasts. From your knowledge of leaf structure, 

 what would seem to be the functions of the air chambers 

 and green filaments ? Study the structure of the thallus 

 below the air chambers. 



3. Examine the attachment and structure of the fringes and 

 rhizoids. 



Draw a cross section illustrating the above points. Micro- 

 tome sections of the thallus (Sec. 212) will show cer- 

 tain details more clearly, as, for example, the structure 

 of the pores, but they should be used only in compari- 

 son with sections of the living plant, in which the dis- 

 tribution of the chlorophyll-bearing tissue may best be 

 studied. 



C. The cups or cupules} 



1. Draw a cup somewhat magnified as it appears on the sur- 

 face of the thallus, showing the buds, or gemmce, within. 

 Are cups found on the same thallus with the stalked disks 

 and umbrellarlike structures ? 



2. Examine a bud under m.p., noting the two notches on 

 opposite sides, which are growing points, and the scar- 

 where it was attached to a stalk. 



3. Search for young Marchantia plants developing from 

 buds. 



4. Section a cup in pith, and study the development of the buds and 

 their attachment. 



1 Lunularia, a relative of Marchantia and frequently common in greenhouses, 

 has a cup of quite different form, but otherwise agrees closely with Marchantia 

 and may be substituted for it. 



