THE GREAT GROUPS OF BRYOPHYTES 



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 



Fig. 97. Marchantia polymorpha. a common liverwort : 1, thallus, with rhizoids, 

 bearing a mature archegonial branch (f) and several younger ones (a, b, e, d. «); 

 S and 3. dorsal and ventral views of archegonial disk: 4 and 5, young sporophyte 

 (sporogonium) embryos; 6. more mature sporogonium still within enlarged venter 

 of archegonium : 7. mature sporogonium discharging spores: 8, 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). 



