DEVELOPMENT OF PLANTS 



283 



like pore over the center of each cavity. From the bottom of 

 the chamber numerous delicate chlorophyll-bearing cells arise. 

 This arrangement of the tissues is again suggestive of the chlor- 

 enchyma of the leaf and it is manifestly protective and adapted 

 to photos3mthesis. The structure of the lower cells of the thallus 



Fig. 188. Section through the center of the thallus of Marchantia, show- 

 ing one of the air chambers and chimney-like pores in the epidermis — ch, 

 palisade-like chlorenchyma arising from bottom of air chamber. The lower 

 cells of the thallus are nearly colorless and filled with watery solutions or 

 mucilage, r, rhizoids; /, leaf-like plates of cells. 



and the distribution of the rhizoids and ventral plates are essen- 

 tially as in Ricciocarpus. 



Marchantia, as in many of the liverworts and some mosses, 

 multiplies extensively by means of buds or gemmae. They are 



Fig. 189. Diagram of a section of one of the cups shown in Fig. 186— g, 

 . buds or gemmae associated with small glandular cells. 



