350 FILICES, [CHAP. 



of the pinnules, singly attached by the middle, each under 

 an imbricating bract-like indusium. Sporanges with longi- 

 tudinal striae. 



Osmunda (regalis). — Sporanges densely covering the 

 upper segments or pinnules of the fertile fronds, so as to 

 recall a panicled inflorescence. Annulus o. 



** Sporanges cohering. Aiumlus o. 



Kaulfussia. — Sporanges radiating, forming round, con- 

 cave sori, opening by slits at the top. 



Fig. 234. Portion of frond and sorus of Kaulfussia. 



*^* Fronds of two distinct pa7'ts — sterile or leafy ^ 

 and fertile or sporange-bearing. 



Ophioglossum. — Sporanges on an undivided spike. 

 Botrychiiim. — Sporanges on a divided or pinnatifid spike. 



The development of young Ferns from their spores may 

 be watched by growing the spores upon damp soil covered 

 by a bell-glass. From the germinating spore arises a small, 

 green, leafy expansion, termed the prothallus, which gives 

 off from its under surface numerous delicate root-hairs. 

 Scattered amongst these fibres, especially on the thicker 

 part o*" the prothallus, are several microscopic cellular 



