FILICINR.K LEPTOSPORANGIA T.K 



•^ -J '-\ 



contain nearly all stages of development. The sporangium 

 here can be readily traced back to a single epidermal cell. 



The sporangial cell protrudes until it is nearly hemi- 

 spherical, when it is cut off by a wall level with the surface of 

 the placenta. This basal cell takes no further part in the 

 development of the sporangium, and after a time becomes 

 indistinguishable. The outer cell now divides by a wall, 

 occasionally transverse, but much more commonly strongly 

 inclined (Fig. 167, A), and striking the basal wall. This is 



fiG. i6j.—Po!ypodiuiit fakatiiiir (^KiMogg). Development of the sporangium. A-E, from living 

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

 showing respectively the surface cells and central optical section ; /, t, tapetum. A-E, X400 ; F, 

 G, X 200. 



now followed by two others, also inclined, and meeting so as to 

 enclose a pyramidal apical cell, from which a varying number 

 of lateral segments 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,^ and formed from the lower of two primary cells, but 

 is merged 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 



' Goebel (lo), p. 21S. 



