20C 



BOTANY 



communicate with the air outside by means of pores, which, in the 

 higher Marchantiaceae, may have the form of chimney-shaped stomata. 



D 



ar. 



FIG. 164. Fimbriaria (Hypenantron) Californica. A, plant with two sporogonial 

 receptacles, slightly enlarged. B, a receptacle (carpocephalum) (x4). C, the 

 same cut longitudinally, showing the " perianth," per, surrounding the sporophyte, 

 sp. D, young carpocephalum, in longitudinal section, showing one of the growing- 

 points, x, and an archegonium, ar. L, air-spaces; st, stoma; r, rhizoids (x 40). 

 E, growing-point and archegonium (X 300). 



The air-chambers may be clearly denned, each with a single stoma, 

 and, in such cases, the upper surface of the thallus presents a regu- 



