Durand : Marchantia polymorpha 



335 



Fig. 98. The deeply staining foot has begun to penetrate the base of the arche- 

 goniura, and the cells of the sporogenous tissue have begun to elongate somewhat. 



Fig. 99. Sporogenous cells about as in figure 98, but the foot has pressed into 

 the base of the archegonium and expanded to form a pileus-shaped absorbent organ, 

 which is filled with food material. 



Fig. 100. A more advanced stage in which the sporogenous cells have separated 

 from one another and become long-triangular in shape and often arranged in pairs. 



Fig. ioi. Somewhat older than the last. The sporogenous cells have become 

 differentiated into two kinds : stout ones and more slender elaters. 



Fig. 102. The stout cells of the last figure have become divided into 8 (rarely 4) 

 spore-mother-cells, those of each group being arranged either in single rows (# , d, e) 

 or in a triangular or subbiseriate manner (6, c>f>g> A). The groups are frequently 

 arranged in pairs (b, c, /i) corresponding to the paired cells of figures 100 and toi. 



tig. 103. An older stage in which each spore-mother-cell has divided into four 

 spores, the tetrads still clinging together in groups of 4 or 8. In /// *the oldest stage, 

 they have begun to separate but still form an easily recognized group. 



