MORPHOLOGY 
Sporophytc. The sporophyte is the most characteristic and com- 
plicated structure in true mosses (fig. 254). As it develops from the 
fertilized egg, the venter and stalk of the archegonium 
develop a remarkable calyptra, which enlarges very 
much, but is finally ruptured near the base by the 
growing sporophyte and is carried up as a cap or hood 
on the top of the capsule. The first division of the 
egg is transverse, and an apical cell with two cutting 
faces is developed in the outer cell or in some one of 
its early progeny. A variable number of segments 
is cut off (fig. 258), resulting usually in a much 
elongated embryo. In the upper end of the embryo 
the usual differentiation into amphithecium and endo- 
thecium occurs ; the former develops into several 
layers, the latter into quite a mass of cells (figs. 259, 
260). The sporogenous tissue is cut off late from the 
periphery of the endothecium, but does not cap the 
columella, which extends completely through the 
capsule as an axis (figs. 261, 262). The sporogenous 
tissue becomes two layers of cells, the mass not being 
dome-shaped, as in Anthoceros 
and Sphagnum, but barrel-shaped. 
Among bryophytes, the sporoge- 
nous tissue, therefore, reaches its 
greatest relative reduction in true 
mosses. 
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5 
Fte. 357. True Capsule. The final structure of the 
moss: an archego- capsule is extremely complex, and a 
nium, showing the longitudinal section may be outlined as 
conspicuous stalk, f o n ows (fig. 2 g 3 ) > beginning with the out- 
the long neck, and side . (i) thee ; dermal , e (a) ^^ 
the axial row (com- , 
posed of egg, ventral la y er , s of waH cells > <3> a region of inter- 
canal cell, and nu- cellular cavities traversed by threads of 
merous disorganized chlorophyll tissue, (4) a tapetal layer phyte> showing the 
neck canal cells). (see p. 126) ; these four regions belong to wor k' f t he apical 
the amphithecium. The endothecium is ce ii. After BARNES 
differentiated as follows : (5) the two layers of sporogenous and LAND, ined. 
cells, (6) an inner tapetal layer, (7) a region of intercellular 
cavities traversed by threads of chlorophyll tissue, (8) the columella. The 
inner region of cavities (7) is present only in such peculiarly organized forms 
as Polytrichum. At the maturity of the capsule the water fails, all the 
