142 STRUCTUEAL BOTANY 



peristome plays a part, as we shall see later, in the 

 dissemination of the spores. 



The whole of the fruit seta and capsule together 

 constitutes the sporophyte generation, and is derived 

 from the fertilised ovum. The latter first divides by 

 a transverse wall ; further divisions take place, so that . 

 a two-sided apical cell arises at both ends of this embryo, 

 and for a time both apical cells are active, each giving 

 rise to two rows of segments. The upper growing-point, 

 however, is the important one, for it produces the 

 capsule and the greater part of the seta, while the 

 lower apical cell only contributes to the foot, which 

 penetrates downwards into the tissues of the oophyte. 

 The segments derived from the upper apical cell under- 

 go division by walls parallel to the surface. In the 

 part which forms the capsule, the inner cells thua 

 formed constitute what is termed the endothecium, and 

 from this central part the columella and archesporium 

 are ultimately derived. Everything outside the 

 archesporium is the product of the peripheral cells or 

 amphithecium. This origin of the spore-producing layer 

 from the outer part of the endothecium is characteristic 

 of the great majority of Mosses. In the seta the 

 central group of cells, corresponding to the endothecium 

 of the capsule, simply gives rise to the central strand 

 of conducting cells. The differentiation of the capsule 

 from the seta takes place rather late in Funaria, after 

 the whole fruit has grown to a considerable length. 



4. GERMINATION OF THE SPORES 



As the capsule dries, the walls of the cells of the 

 annulus split across and the lid is detached. The 



