Peat-Mosses 



Fertilisation occurs early in the spring, that is, sperm-cells 

 (antherosoids) from antheridia, swim over in water to a mature 

 egg-cell of an archegonium, coalesce with it and make possible 

 the development of an embryo spore-case (4). 



The Spore-case. The first embryos may be found late in 

 February. A study of their development shows that the fertilised 

 egg-cell divides into four cells and then by repeated division of 

 cells takes the form of the several diagrams in order, A, B, C, and 

 D. The embryo which has been formed as a result of fertilisation 

 is divided into two regions, the 

 three upper segments with the 



Okttr luxlX. 



Inner >nas 



Vertical section of developing embryo. 

 Sphagnum acutifolium. 



apical cell give rise to spores, while the lower segments with the 

 basal cell form a "foot." The rudimentary spore-case is at first 

 sessile, but later is raised by the lengthening of the apex of the 

 branch upon which it is borne. 



Veil (calyptrd). The veil is the fragmentary remains of the 

 old archegonium wall which was burst by the enlarging spore- 

 case within and left at the base, or carried up on the lid. 



Pedicel (seta). The "foot" of the Sphagnum* is homologous 

 with the pedicel of other mosses, as it is due to a development 

 of the base of the archegonium. The so-called pedicel (pseudo- 

 podium] is the result of a lengthening upward of the apex of the 

 branch which bears the archegonium. This branch so enlarges 

 just below the developing spore-case as to completely envelop 

 the "foot." 



Lid (operculum). When the spore-case is mature enough to 

 open, the upper portion separates from the lower by the breaking 

 down of the walls of a zone of cells. This zone of weak cells is 



121 



