Ill 



MARCHANTIEyE 



45 



and in the latter form, which is extremely common in green- 

 houses, the plant multiplies only by gemma, as the plants 

 are apparently all female. These gemmae, as is well known, 

 are produced in special receptacles upon the dorsal side of the 

 thallus. The receptacles are cup-shaped in Marchantia, and 

 crescent-shaped in Ljinularia, where the forward part of the 

 margin of the cup is absent. These cups are apparently 



A. 



Fig. 12. — JSIarchantia jiolyinorphaiX--')- A, Plant with gemma cups (z^', ^), X2; B-F, develop- 

 ment of the gemmae, X 525 ; G, an older gemma, X 260 ; v, v' , the two growing points. 



specially developed air-chambers, which, closed at first, except 

 for the central pore, finally become completely open. The 

 edge of the fully-developed receptacle is fringed. The gemmae 

 arise from the bottom of the receptacle as papillate hairs, and 

 their development is the same in the two genera where they 

 occur. Fig. I 2 shows their development in M. polymorpJia. 



One of the surface cells of the bottom of the receptacle 

 projects as a papilla above the surface, and is cut off by a 

 transverse wall from the cell below. The outer cell next 



