BRYOPHYTA 



These undergo further sub-divisions to constitute an endothecium of four cells, 

 and a many-celled amphithecium (Fig. 134 G). The hypobasal half, which 

 has meanwhile undergone irregular divisions, together with the two lowest 

 segments of the epibasal region remains sterile, and constitutes the short 

 seta and enlarged foot. Three or four only of the upper segments are 

 fertile, while the rest go to form the sterile apex of the capsule (Fig. 134 E). 



FIG. 134. 



Development of sporogonium of Andreaea. A= young embryo of A. crassinervia, 

 Brch. B = A. petrophila, Ehrh. C = of A . crassinervia, older. D = of A . sp. , older still. 

 E= optical longitudinal section of A. petrophila ; ,y/r= archesporium. J F=optical trans- 

 verse section of a young embryo ; jj = segment- walls ; rr = radial walls ; aa = first divisions 

 of the quadrants. G = older stage ; ^="grund-quadrat." // = older stage with division 

 to form archesporium. / = archesporium differentiated. /if = archesporium divided into 

 two layers; as/> = outer spore-sac ; col. =columella. (After Waldner.) D after C. Miiller- 

 Berol. (From Engler and Prantl.) 



The archesporium is here, as in all other Mosses, derived from the endo- 

 thecium : the peripheral cells which result from the segmentation of the 

 endothecium, become densely granular, and give rise to spore-mother-cells, 

 the internal cells form the columella (Fig. 134 E, j, K). It is not stated 

 by Waldner how the archesporial dome is completed at its apex: probably 

 it is by certain cells of the inner product of the endothecium, forming 

 spore-mother-cells, in place of sterile cells of the columella. In this there 

 would be no theoretical difficulty, for on the present theory all cells derived 

 from the endothecium were at first potentially fertile cells ; moreover, as 

 bearing indirectly on this point, the internal limit between the archesporium 



