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. 286. Marchantia polymorpha, a common liverwort : i, thallus, with rhizoids, 

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

 2 and 3, dorsal and ventral views of archegonial disk; h and 5, young eporophyte 

 (eporogonium) 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. 283, B). 



