166 



PLANT MORPHOLOGY 



Air chiimbers and air pores are developed on both the male and female 

 receptacles. In Reboulia and Asterella the air pores on the female recep- 

 tacle are compound, while those occurring elsewhere on the plant are 

 simple. In Conocephalum the air pores are compound on both the male 



Fig. 133. Female structures of Marchantia polymorpha. A, longitudinal section through 

 young female receptacle, showing a row of archegonia, X40; B, mature archegonium with 

 egg ready for fertilization, X300; C, young embryo lying within the archegonium, X300. 



and female receptacles, but are simple on the thallus. In Marchantia 

 the air pores are everywhere compound. 



The mature antheridia of the Marchantiales are club-shaped structures 

 with a short stalk (Fig. 1325). The chamber in which each lies com- 

 municates with the surface of the thallus or receptacle by a pore through 

 which the sperms escape. The antheridium arises from a single super- 

 ficial initial cell that becomes papillate and then divides transversely 

 (Fig. 134^). The outer segment undergoes several additional transverse 



