Sphagnales. 15 
from the inner layer of the amphithecium, the endothecium of the 
capsule forming the sterile columella. The archesporium soon 
becomes four-layered, and the cells adjoining it on both sides 
divide so as to form a small-celled spore-sac layer, as in Bryales. 
The stalk of the fertilised archegonium expands as the haustorium 
bores down into it and into the underlying tissue of the stem, the 
lower part of the venter also stretching to keep pace with the 
growth of the capsule, while the withered neck and upper portion 
of the venter are carried up on the surface of the calyptra. 
Fig. 66. Sphagnum compactum ; later stage in development of sporogonium. 
Chlorophyll is present in the developing capsule, especially in 
the tissue lying outside of the spore-sac and in the small cells of the 
spore-sac itself. As the capsule matures, the cells of the super¬ 
ficial layer acquire thickened and brown coloured walls, forming a 
well defined epidermis ; along a circular transverse line near the 
top of the capsule these cells remain small, forming the groove¬ 
like annulus and delimiting the lid by which the capsule eventually 
dehisces (Fig. 67, Fig. 68 c). The epidermis shows numerous 
rudimentary stomata, which begin to develop like those on the 
