THE LIFE OF A FERN. 



pocket lens (one that will magnify eight or ten 

 diameters will answer), we shall generally find that 

 the spores fall from little cases (sporangia), which 

 are collected in groups (sorus, pi. sort). These 

 (see PL 5, Fig. 7) are usually on or at the termina- 

 tion of a little vein. Sometimes they are in circu- 

 lar patches on the vein, and unprotected by any 

 covering, as in Polypodium (PL 5, Fig. 4) ; some- 

 times they are covered or protected by a little 

 membrane, which may be attached at the centre 

 as in Aspidium (PL 5, Fig. 7), or on one side as in 

 Asplenium. Sometimes the cases are in lines 

 along the whole length of the vein, as in the Cali- 

 fornia Gold-Fern (Gymnogramme triangularis) (PL 

 5, Fig. 8) ; or along the entire edge of the leaflet 

 (pinnule), as in Pteris (PL 5, Fig. 9) ; or, again, along 

 the edge in detached groups, as in the Maiden-hair 

 (Adiantuiri). The sporangia of ferns are found to 

 have five quite distinct forms, upon which the 

 Orders are founded. With the largest order, the 

 Polypodiacea, the spore-cases are stalked, and have 

 around them a vertical ring of cells more elastic 

 than those of which the rest of the case is com- 

 posed (PL 5, Fig. i). When the spores are ripe, 

 this ring contracts, rupturing the case, and allowing 

 the spores to be discharged into the air, where they 

 fly off like dust. The common Polypodium, Aspi- 

 dium, and Asplenium are illustrations. With the 

 Lygodiums and Anemias the spore-cases are sessile 



