220 



THE PLANT WORLD. 



The life-history of the members of the fihny fern family resem- 

 bles that of the common brake iPtcridiiiiii) of our roadsides, but 

 varies in certain details. Along the margins of the fronds at the 



ends of the veins are 

 the receptacles or sori, 

 within which the spores 

 are borne. These sori 

 are flattened in the 

 genus HyiuenophyUum 

 (fig. 34, A) and have 

 the form of a two- 

 valved capsule. In the 

 gfenus Triclwiiiancs the 

 sporangia are attached 

 to the protruding vein 

 and the sorus has a 

 vase-like form (fig. 34, 

 B ) . This elongation of 

 the veins beyond the 

 margin gives this genus 

 Triclwinaiics its name 

 (Greek, thrix, hair). 



The spore-cases are encircled horizontally by a ring or annnhis 



(fig. 35, a) of diick-walled cells, and burst vertically downward. 



The spores are green, and are spherical or triangular in shape in 



different species. They often 



besfin to orerminate while thev 



are still within the sporan- 

 gium, though the later de- 



velopment is often extremely 



slow. They do not produce a 



heart-shaped prothallus like 



that of the brake, but in the 



genus Hyinciiophylliiiii, at 



least, a slender, tapering 



structure which bears the sexual organs at its base; the male, 



or antheridia (fig. 36, a), and the female, or archcgonia {b). 



Fig. 34. Filmy Ferns. A, Hymcnophylla 

 aspic noidcs: B, Trichoinaiics rigidum. 



Fig. 35. Sporangia and Spores. 



