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 photosynthesis. The structure of the lower cells of the thallus 



FIG. 1 88. 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. 



