268 



ESSENTIALS OF BOTANY 



Fiu. 192. Section through An- 

 theridial Receptacle of Mar- 

 chantia. (Magnified.) 



u, antheridium. 



(/) The female receptacles, stalked structures with finger-like re- 

 curved arms radiating from the center. With the magnifying glass 



examine the under surface of a very- 

 mature receptacle and note the young 

 sporopliytes, or spore-plants, hanging 

 from the receptacle. Draw. 



344. Minute Structure of Thallus 

 and Buds. — Cut thin cross-sections 

 of the thallus and examine with l.p. 

 and then with m.p. Note : 



(a) The general structure of the 

 thallus, with a firm upper epider- 

 mis, spongy parenchyma beneath it 

 (which serves for the storage of re- 

 serve food materials), and a thin 

 lower epidermis. 



(V) The air-chambers beneath the 

 pores, each containing many short 

 branching threads, made of pear-shaped cells. 

 Compare these cells with others of the thal- 

 lus as regards the number of chlorophyll 

 bodies which they contain. What effect do 

 these cellular threads have on the amount 

 of surface for photosynthetic work in the 

 air-chamber ? 



(c) The rhizoids. From which surface 

 do they spring ? Are they all alilM ? 



Make a drawing to illustrate the general 

 structure of the thallus, showing position 

 of the air-chamber and attachment of the 

 rhizoids. INhike a detailed, highly magni- 

 fied drawing of the air-chamber. 



Pick out from the cups several buds and 

 examine them with m.p. Note : 



(a) The shape of the buds. 



(b) The notches which show the posi- 

 tion of the growing poiiiis of the bud. How many are there? 



(f) The minute stalk of each bud. How is this attached? 



Fig. 193. Sectional View 

 of an Antheridium of 

 Marchantia. 



a. 



antheridium; s, sperms. 

 ( X 700.) 



