622 FILICES. (FERNS.) 



ORDER 164. FILICES. (FERNS.) 



Leafy plants, mostly with perennial rootstocks (caudex), which in 

 this climate are creeping and slender, or stouter and sometimes as- 

 cending, but in the tropics often grow many feet high, with a diameter 

 of several inches, giving the plants an arborescent appearance (tree- 

 ferns). Leaves (fronds) circinately rolled up in vernation, and raised 

 on a stalk or petiole (stipe). Spore-cases (sporangia), one-celled, borne 

 on the under side of the fronds or along their margins, often covered 

 by a membrane of various shape (indusium or involucre), containing 

 numerous exceedingly minute spores. 



Synopsis. 



SUBORDER I. POLYPODINPL-E. Sporangia collected in dots, lines, or 

 variously shaped clusters (so/-/ or fruit-dots), or in indefinite masses, cellular- 

 reticulated, mostly pedicelled ; the stalk running into a vertical incomplete 

 elastic ring, the straightening of which ruptures the ripe sporangium on 

 the inner side, discharging the spores. Frouds simple or variously divided. 



TRIBE I. ACROSTICHE^E. Sporangia collected in large or indefinite masses on 

 the back of the frond : indusium none. 



1. ACROSTICHUM. Sporangia covering the lower surface of the upper pinnae. Veins 



reticulated. 



TRIBE II. POLYPODIE^E. Fruit-dots roundish, distinct, destitute of indusium, 

 borne on the back of the frond. 



2. POLYPODIUM. Fruit-dots scattered variously on the back of the frond, borne at or 



near the ends of the veins. 



TRIBE III. GRAMM1TIDE.33. Fruit-dots usually linear, dorsal, variously arising 

 from the veins. Indusium none. 



3. TJJNITIS. Fruit-dots linear, central or submarginal. 



TRIBE IV. VITTARIEJE. Sporangia borne in a continuous elongated marginal or 

 sub-marginal furrow. 



4. VITTARIA. Fronds simple, narrowly linear. 



TRIBE V. PTERIDEJEo Fruit-dots marginal, separate or continuous. Indusium 

 formed by the reflexed margin of the frond or its lobes, opening toward the midrib. 



* Indusium thin and membranaceous, continuous around the margin of the fertile pinnae. 



5. PTERIS. Sporangia borne on a transverse intraniarginal veinlet. 



6. PELLJiA. Sporangia borne on the ends of the veins, at length confluent. 



* * Indusium rarely continuous, mostly formed of the reflexed ends of the lobes or divisions 



of the pinnae or pinnules. 



7. CHEILANTHES. Sporangia borne on the veins beneath the reflexed margin of the 



frond. Pinnules with a midrib. 



8. ADIANTUM. Sporangia borne on the under side of the indusium. Midrib none or 



eccentric. 



9. CERATOPTERIS. Fruit-dots on the upper part of the veins, distinct, or forming a 



marginal band of sporangia. 



