PTERIDOPHYTA 



267 



Antheridium. The mother-cell of the antheridium (Fig. 230) divides by a 

 transverse wall into a superficial cell which develops into the outer wall, and an 

 inner cell which, by repeated divisions, produces the mass of sperm-cells. The 

 outer cells, according to Jeffrey (19), always divide ultimately into two layers, 

 like the cells covering the antheridial cavity in the Anthocerotales. The large 

 multiciliate spermatozoids are much like those of the typical Ferns. 



Archegonium. The archegonium (Fig. 230, C) does not differ essentially 

 from that of the typical Ferns. It has a straight neck, which is longer than 



cal 



FIG. 231. Botrychium Virginianum. Longi- 

 tudinal section of an advanced embryo 

 (X 35) ; s, stem-apex; c, cotyledon; /, foot; 

 r, root ; cal, calyptra. (After JEFFREY.) 



that of Ophioglossum, which it otherwise 

 resembles. 



The Embryo. The first division in 

 the embryo is transverse, and the develop- 

 ment of the organs of the young sporo- 

 phyte is much later than in the more 

 specialized Leptosporangiatae (Fig. 231). 

 This late external differentiation, and the 

 correspondingly long dependence of the 

 sporophyte upon the gametophyte, ap- 

 proach the condition found in the Bryo- 

 phytes. The stem and root grow from 

 a tetrahedral apical cell which is similar 

 to that found in the same parts of the 

 typical Ferns. The foot is very large, and 



FIG. 232. A, Ophioglossum vulgatum. 

 Sporophyte, slightly reduced. B, C, 

 O. pendulum. B, section of sporan- 

 gial spike ( X 3). C, transverse sec- 

 tion of the spike, showing the large 

 sporangial cavities (X 4). D, Botry- 

 chium Virginianum; spomngrd. (x3). 



the sporophyte may remain for several years attached to the gametophyte. 



The Mature Sporophyte 



The sporophyte in both Ophioglossum (Fig. 232) and Botrychium (Fig. 233) 

 has a short, upright stem which, in our native species, is subterranean. The 

 thick, fleshy roots contain a mycorhiza like that in the gametophyte. In some 

 tropical species e.g. Ophioglossum pendulum the plant is epiphytic. The 



