BRYOPHYTA 



181 



divisions before vertical walls appear, so that the embryo becomes elon- 

 gated (Fig. 149A-C). A foot, seta, and capsule, always present, are 

 differentiated early. The formation of periclinal walls in the upper part 

 of the embryo dehmits the amphithecium from the endothecium, the 



D E F 



Fig. 148. Development of the archegonium of Pellia epiphylla, X400. A, division of 

 initial; B, appearance of vertical walls in outer cell; C, formation of cover cell and central 

 cell; D, formation of primary neck canal cell and primary ventral cell; E, formation of four 

 neck canal cells and division of primary ventral cell; F, nearly mature archegonium with 

 egg, ventral canal cell, and six neck canal cells; G, cross section of neck. 



former giving rise to the capsule wall, the latter to the sporogenous tissue 

 (Fig. U9D). 



The seta undergoes considerable elongation, especially upon the ripen- 

 ing of the spores. The capsule is highly developed, producing both 

 spores and elaters. It may be spherical, as in Pellia, or more or less elon- 

 gated, as in Pallavicinia. In some genera an elaterophore is developed 

 inside the capsule. It may be either apical, as in Riccardia and Metzgeria, 

 or basal, as in Pellia (Fig. 150). The elaterophore consists of a group of 

 sterile cells to which some of the elaters are attached. The fixed elaters 

 generally are shorter than the free elaters and often have a greater number 

 of spiral bands. The spore mother cells, unlike those of the Marchan- 



