256 FILICES. 



bearing panicle or pinnate spike, distinct from the leafy 

 frond, and the sporanges without any trace of the annulus 

 which usually surrounds them, partially or wholly, in 

 other Ferns : and Adder's tongue (Ophioglossum vul- 

 gatttm], similar to Moonwort, but the leafy and fertile 

 fronds undivided. 



The development of young Ferns from their spores 

 may be watched by sowing the spores upon damp soil, 

 covered by a bell-glass. From the germinating spore 

 arises a small, green, often obcordate or obovate hori- 

 zontally spreading leaf-like expansion, called a prothal- 

 Hum, which gives off delicate root-hairs from its under 



FIG. 200. Pinnule and sorus of Hymenophylhun. 



surface. Upon the same surface, scattered amongst these 

 hairs, especially on the thicker part of the prothallium, 

 are several minute microscopic cellular bodies, of two 

 distinct kinds, both originating in the epidermal layer of 

 the prothallium. One kind, the more numerous, called 

 antheridia, consists of a few superposed cells, forming a 

 minute papilliform projection, surrounding a cavity con- 

 taining a number of extremely small vesicles, each of 

 which contains a microscopic spirally-twisted motile 

 filament of dense protoplasm, called an antherozoid, which 

 performs the function of a pollen-grain. The other kind, 

 called archegonia, which are somewhat similar to the 

 antheridia externally, consist when mature, of a few rows 

 of superposed cells surrounding a narrow canal at the 



