198 MOSSES AND FERNS chap, vii 



cell in contact with the endothecium, and an outer larger one. 

 This first division separates the wall of the capsule from the 

 outer spore-sac. The latter next divides by radial and trans- 

 verse walls, and later by periclinal walls into two layers (Fig. 

 96). Almost coincident with the latter, the rows of cells 

 lying immediately outside it show a very characteristic appear- 

 ance. They cease to divide, and with the rapid growth in 

 diameter of the capsule become much extended both vertically 

 and laterally, but are compressed radially. It is between these 

 cells and the spore-sac that the characteristic air-space found 

 in the capsule is formed. This is first evident shortly after 

 the enlargement of the base of the capsule begins. The 

 development can be very easily followed in longitudinal 

 sections made at this stage. The formation of the space 

 begins at the base of the capsule and proceeds toward the top. 

 The line of cells bordering on the spore -sac is very easily 

 followed, owing to their being so much larger than the neigh- 

 bouring ones. As this is followed down, it is found that at 

 the base of the capsule the cells are separated by large 

 intercellular spaces, which become less marked toward the 

 apex. With the rapid enlargement of the capsule these spaces 

 become very large, and sections made a little later show that 

 during this process the cells remain in contact at certain 

 points, and form short filaments that extend across the space 

 and unite the wall of the capsule with the outer spore-sac. 

 At the base of the capsule the formation of intercellular spaces 

 is not confined to the single layer of cells but involves the 

 whole central mass of tissue, which becomes thus transformed 

 into a bundle of filaments connecting the columella with the 

 basal part (apophysis) of the capsule. The innermost of the 

 two layers of cells between the archesporium and the air-space 

 finally undergoes a second periclinal division, and in the full- 

 grown sporogonium the archesporium is bounded on the 

 outside by three layers of cells. 



The differentiation into seta and capsule takes place late 

 in Funaria, and the first indication of this is the enlargement 

 of a zone between the two, forming the apophysis, which at 

 this stage (Fig. 97) is much greater in diameter than the 

 upper part of the capsule. Sections through the apophysis 

 and seta show a less regular arrangement of the cells than the 

 sporiferous part of the capsule, but the general order of cell- 



