THE ROCK SPLEENWORTS. 



manages to exist upon many shaly hillsides 

 where the falling fragments are constantly 

 crowding its fronds. 



The fronds are borne on very short 

 stipes in tufts from a small rootstock. 

 There is a noticeable difference between fer- 

 tile and sterile blades. The latter are seldom 

 more than six inches long and an inch wide 

 and spread close to the earth. 

 They are once pinnate with close 

 set, short, blunt and obscurely 

 serrate pinnules eared on the su- 

 perior side at base. The fertile 

 are three or four times longer, 

 stiffly erect, in marked contrast 

 to the others. The pinnules are 

 also much longer, often an inch 

 or more in length, usually con- 

 spicuously serrate and inclined to 

 be eared on both sides at base. 

 They are about linear-oblanceo- 

 late, tapering acutely below and with pin- 

 nules much farther apart than in the sterile 

 frond. The rachis in 

 both kinds of fronds is 

 dark shining brown. The 

 sori are borne in a double 

 row on each pinnule at 

 some distance from the 

 margins. When young the white indusium 

 is conspicuous, but it soon withers and the 

 sori, becoming confluent, cover most of the 

 under surface of the frond. The fertile 



