THE GREAT GROUPS OF BRYOPIITTES 



113 



cells more or less modified for conduction. Above these 

 the dorsal region is organized into a series of large air cham- 

 bers, into which project chlorophyll-containing cells in the 



^^Ji 



Fig. 97. Marchantia polyinorphn. a common liverwort : U thallns. with rhizoide, 

 bearing a mature archegonial branch if) and several younger ones (fl, b. c. d, e)\ 

 2 and 5, dorsal and ventral views of archegonial disk; h and ,-7. young sporophyte 

 (sporogoninm) embryos; G. more mature sporogonium still within enlarged venter 

 of archegonium: 7. mature sporogonium discharging spores; S, three spores and 

 an elater. — After Kny. 



form of short branching filaments. Overarching the air 

 chambers is the dorsal epidermis, and piercing through it 

 into each air chamber is a conspicuous air pore (Fig. 94, B). 



