678 FILICES. (FERNS.) 



ORDER 131. FILICES. (FERNS,) 



Leafy plants, with the leaves (fronds) usually raised on a stalk or peti- 

 ole (stipe), rising from a (sometimes greatly elongated) rootstock, sepa- 

 rately rolled up (circinate) in the bud, and bearing on the under surface 

 or along the margin small reticulated sporangia, which at length split open 

 and discharge the numerous minute spores. Prothallus green, above ground, 

 normally monoecious. 



SUBORDER I. Polypodiacege. Sporangia collected in dots, lines, 

 or variously shaped clusters (sori or fruit-dots) on the back or margins 

 of the frond or its divisions, cellular-reticulated, stalked, the stalk run- 

 ning into a vertical incomplete many-jointed ring, which by straightening 

 at maturity ruptures the sporangium transversely on the inner side, dis- 

 charging the spores. Fruit-dots often covered (at least when young) by 

 a membrane called the indusium (or less properly the involucre), growing 

 either from the back or the margin of the frond. (Plates 16-19.) 



Tribe I. POLYPODIE^E. Fructification on the back of the frond, in round or 

 roundish fruit-dots (sori) placed on the veins or at the ends of the veins, without indu- 

 sium of any kind. Stipes articulated to the rootstock, leaving a distinct scar when 

 separated. Veins free (not reticulated) in our species. 



1. Polypodium. Sori round, in one or more rows, on each side of the midrib or of the 



segments of the frond. 



Tribe II. GRAMMITIDE^E. Sori more or less elongated, without indusium, placed 

 on the back of the frond, usually along the veins or near their extremities. Veins free 

 in our species. 



2. Notbolnoiia. Sori short, of few rather large sporangia, placed near the tips of the 



veins ; under surface of the frond usually either chaffy, woolly, or powdery. 

 Tribe III. PTERIDE.32. Fructification marginal or intramarginal, provided with a 

 general indusium formed of the (either altered or unchanged) margin of the frond. Stipes 

 not articulated to the rootstock. Veins free in all our species. 

 * Sporangia at the ends of the veins, on a reflexed portion of the margin of the frond. 



3. Adiantum. Midrib of the pinnules marginal or none. Stipe black and polished. 



* * Spprangia borne on a continuous marginal vein-like receptacle, connecting the apices of 



the veins, and covered by a delicate whitish indusium formed of the reflexed margin. 



4. Pteris. Midrib of the pinnules central. Stipe light-colored. 



* * * Sporangia at or near the ends of the unconnected veins, borne on the under surface 



of the frond ; indusium various. 



5. Cheilanthes. Sori minute, at the ends of the veins ; indusium continuous or inter- 



rupted. Fronds mostly chaffy, woolly, or pulverulent, rarely smooth. 



6. Pellaea. Sori on the upper part of the veins, distinct, or mostly forming a confluent sub- 



marginal band of sporangia. Indusium membranaceous, continuous, rarely wanting. 

 Sterile and fertile fronds not very unlike ; stipes dark-colored ; fronds smooth. 



7. Cryptogramme. Sori roundish or elongated and extending far down the free veins, 



at first covered by the very broad continuous indusium, at length exposed and con- 

 fluent. Sterile and fertile fronds very different ; stipes light-colored ; fronds smooth. 

 Tribe IV. BEECHNE^E. Sori oblong or linear, borne on a veinlet parallel to the 



midrib, and covered with a special usually concave or arched indusium attached to the 



fruiting veinlet, and opening along the inner side. 



8. Woodwardia. Sori forming a chain-like row each side of the midrib or central vein. 



Veins reticulated. 



