656 FILICES. (ferns.) 



Subouder I. POLYPODIA CEJE. The True Ferns. 



Sporangia collected in dots, lines or variously shaped clusters {sori o* 

 fruit-dots) on the back or margins of the frond or its divisions, stalked, 

 cellular-reticulated, the stalk running into a vertical incomplete many- 

 jointed ring, which by straightening at maturity ruptures the sporangium 

 transversely on the inner side, discharging 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 15-18.) 



Tribe I. POLYPODIES. Fructification on the back of the frond, in roundish or 

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

 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 each side of the midrib or of the seg- 



ments of the frond. 



Tribe II. PTERIDEJE. Fructification marginal or intramarginai , proTided 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, borne on a reflexed portion of the margin of the frond. 



2. Ailiantuni. Midrib of the pinnules near the lower margin or none. Stipe black and 



polished. 



* * Sporangia borne on a continuous marginal vein-like receptacle, which connect* the apices 



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

 of the pinnule. 



3. Ptci'is. Midrib of the pinnules central. Stipe light-colored. 



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



the frond : indusium various. 



4. Cb.eiluu1.lies. Sori minute, at the ends of the veins, indusium continuous or inter- 



rupted. Fronds mostly chaffy, woolly or pulverulent. 



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



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

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



6. Allosorus. Sori roundish or elongated and extending far down the free veins, at first 



covered by the reflexed herbaceous margin of the segment, at length exposed and con- 

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



Tribe III. ASPLElVIEiE. Sori more or less elongated, occupying one or both sides 

 (but not the back) of the veins, covered by a special indusium which is attached by one 

 side to the fertile vein, and is free on the other. Stipes not articulated. 



* Sori linear or oblong, borne on cross veins parallel to the midrib. 



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



Veins reticulated. 



* * Sori linear or oblong, borne on veins oblique to the midrib. 



8. Asplcnimn. Sori on the upper side of the fertile veinlet, rarely on both sides of a 



veinlet. Veins free in all our species. 



9. Scolopemdrium. Sori linear, confluent in pairs, each pair appearing like a single 



sorus with a double indusium opening down the middle. Veins free. 



* * * Sori borne partly on veins parallel to the midrib, partly on veins oblique to the midrib. 



10. Camptosorus. Sori oblong or linear, the outer ones often approximating in pairs. 



Veins reticulated. 



