312 



PLANT STUDIES 



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. 386. MarcJiantia polymorpha, a common liverwort : i, thallus. with rhizoide, 

 bearing a mature archegonial branch (/) and several younger ones {a, b, c, d, e)\ 

 2 and 3, dorsal and ventral views of archegonial disk; k and 5, young sporophyte 

 (sporogonium) embryos; G, 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. 283, B). 



