30 



A TERN BOOK TOU EYERYBODY. 



Clusters circular.— Coy e^mg Mdney-sliaped in the Eoss 

 Eehns {Lastrea.) (Fig. 12.) 

 Covering circular in the Shield 

 Feens {Folysticlmoii). (Fig. 13.) 



Clusters oblong or linear. — Covering oblong, kidney- 

 shaped, and fringed at the outer 

 margin, Lady Feri^ {Athjriim). 

 (Pig. 14.) 

 Covering straight in Spleenworts 

 {AspJeniim). (Fig. 15.) 



Clusters in pairs. — Covering opening down the centre be- 

 tween the twin clusters in Hart's 

 Tongue (Scolopendrium) . (Fig. 16.) 



Fig. 15. Fig. IG. 



Spore-cases concealed amongst brown cha% scales, 

 in the Scale Ferk (CeteracJi). 



Finally, the clusters of spore-cases form a continuous 

 line along the back of the frond between the mid-rib and 

 the margin, with a linear covering, in the Hard Fern 

 {JBlecJinum). (Fig. 17.) 



It will be observed that in all the above seven genera, 

 in which there is a true covering, the fructification is 

 dorsal ; that is, it is borne on the back of the frond. In 



