IX 



FILICINE^ LEPTOSPORANGIATAL 



341 



placenta. The basal cell takes no further part in the develop- 

 ment of the sporangium, and after a time becomes indistin- 

 guishable. The outer cell now divides by a wall, occasionally 

 transverse, but much more commonly strongly inclined (Fig. 

 190, A), and striking the basal wall. This is now followed by 

 two others, also inclined, and meeting so as to enclose a pyram- 

 idal apical cell, from which a varying number of lateral seg- 

 ments are cut off. These form three rows, corresponding to 

 the three rows of cells found in the stalk, which is not sharply 

 separated from the capsule, as stated by Goebel ( ( 10), p. 218), 

 and formed from the lower of two ])rimary cells, but is merged 



G. 



Fig. igo.—Polypodium falcatum. Development of the sporangium. A-E, from living 

 specimens; F, G, microtome sections; A, B, C, optical sections; D, E, the same 

 ■ sporangium, showing respectively the surface cells and central optical section; t, t, 

 tapetum. A-E, X400; F, G, X200. 



gradually into the capsule, and owes its three-rowed form to a 

 primary and not a secondary division. The upper part of the 

 young sporangium enlarges, so that it becomes pear-shaped 

 (Fig. 190, B), and a periclinal wall is then formed in the apical 

 cell. The cells of the stalk undergo no longitudinal divisions, 

 ;=and it remains permanently composed of three rows, 

 rrrr!; Kiindig (i) first called attention to the real state of affairs, 

 ;and since, C. Miiller (2) has investigated the matter further. 



