90 



BOTANY. 



by a single row of cells (canal cells), with more granular contents than the 

 outer cells, the lowest cell of the row being somewhat larger than the 



others (Fig. 54, C, o). When nearly 

 ripe, the division walls of the" canal 

 cells are absorbed, and the proto- 

 plasm of the lowest cell contracts 

 and forms a globular naked cell, 

 the egg cell (Z), o). If a ripe arche- 

 gonium is placed in water, it soon 

 opens at the top, and the contents of 

 the canal cells are forced out, leav- 

 ing a clear channel down to the egg 

 cell. If the latter is not fertilized, 

 the inner walls of the neck cells 

 turn brown, and the egg cell dies ; 

 but if a spermatozoid penetrates 

 to the egg cell, the latter develops 

 a wall and begins to grow, forming 

 the embryo or young sporogonium. 

 The first division wall to be formed 

 in the embryo is transverse, and is 

 folio wed by vertical ones (Fig. 54, E, 

 em.). As the embryo enlarges, the 



walls of the basal part of the archegonium grow rapidly, so that the em- 

 bryo remains enclosed in the archegonium until it is nearly full-grown 



(Fig. 55). As it increases in size, it 

 becomes differentiated into three parts : 

 a wedge-shaped base or " foot " pene- 

 trating downward into the upper part 

 of the plant, and serving to supply 

 the embryo with nourishment ; second, 

 a stalk supporting the third part, the 

 capsule or spore- bearing portion of the 

 fruit. The capsule is further differen- 

 tiated into a wall, which later becomes 

 dark colored, and a central cavity, in 

 which are developed special cells, some 

 of which by further division into four 

 parts produce the spores, while the 

 others, elongating enormously, give rise 

 to special cells, called elaters (Fig. 56,.B). 



FIG. 55. Longitudinal section of a 

 nearly full-grown sporogonium of 

 Madotheca, which has not, however, 

 broken through the overlying cells, 

 x 25. sp. cavity in which the spores 

 are formed, ar. abortive arche- 

 gonium. 



FIG. 56. Spore (.4) and two 

 elaters (jB) of Madotheca, x 300. 



