172 MACOUN AND BURGESS ON" 



nia. Tho sporangia are usually collected in little masses called sort, which are oftenest found on the veins 

 or at the tips of the veins, and are often covered either by a little scale (indutium) produced from the epider- 

 mal cells, or by a general involucre formed from the recurved margin of the frond or its di\ isions. 



Suborder 1. Poi.vroDiAOE.a5. Sporangia globular, or slightly flattened laterally, collected in patches, lines or dots 

 of various shapes, stalked, and provided with a vertical Incomplete many-jointed ring which straight' 

 maturity and discharges the very minute spores, the sporangium opening by a transverse split across the 

 side not occupied by the ring. Terrcstial ferns. 



Tribe I. Polypodia^. Sori round or oblong, placed on the veins or at the ends of the veins ; indtisium none. 

 Stalk articulated to a slightly prominent knob of the usually elongated creeping rootstock. Veins free or 

 variously reticulated. 



1. POLYPODIUM. The only genus of the tribe, 



Tribe II. (jiranimilidcse. Sori more or less elongated, without indusium, superficial, placed on the back of 

 the frond or its divisions, and usually following the veins, or only near the tips of the latter and near the 

 margin. Fronds sometimes scaly or tomentose, or covered beneath with coloured powder. 



2. GYMNOGRAMMF. Sori much elongated, following the veins, and like them often branched or reticulated. 



Tribe III. Ptoridea*. Sori close to the margin, sometimes extending partly down the voins, covered, at 

 least when young, by an involucre, opening inwards and either consisting of the margin or produced from it. 



3. CHEILANTHES. Sori minute, at the ends of the unconnected veins, covered by a usually interrupted 

 involucre. Small ferns, often woolly, chaffy or pulverulent, 



4. PELLvEA. Sori near the ends of the veins, often confluent Involucre membranaceous, continuous round 

 the pinnules. Sterile and fertile fronds much alike and smooth ; the stalk dark-coloured. 



5. CRYPTOGRAMME. Sori extending down the free veins. Involucre very broad, at length flattened out and 

 exposing the now confluent sori. Sterile and fertile fronds unlike, smooth ; the stalk light-coloured. 



6. PTERIS. Sporongia borne on a continuous vein-like marginal receptacle, which connects the onds of the 



veins. Involucre continuous round tho pinnules. Stalk light-col. aired. 



7. ADIANTUM. Sporangia borne at the ends of the veins, on the under side of the reflexed margin of the 

 frond. Midvein of the. pinnules mostly eccentric or dissipated into forking veinlets. Stalk dark-coloured. 



Tribe IV. ISI<< iui< ;r. Sori more or less elongated, borne on a fruiting veinlet or on a special receptacle 

 parallel to the midrib, either near it or remote from it, and provided with a special usually concave or arched 

 indusium attached to the receptacle outside the sorus and opening along the inner edge. 



8. LOMARIA. Sori continuous from the base of the pinna to its apex, the receptacle nearer the margin than 

 the midvein. Fronds in our species once pinnate, the fertile, ones with contracted pinnse. 



9. WOODWARPIA. Sori interrupted, forming a chain-like row each side of the midvein. Fronds in our species 

 ample, compound ; the veins reticulated. 



Tribe V. A splenica*. Sori more or lees elongated, borne on veins oblique to the midvein, covered by a 

 special usually flattened indusium attached to the fertile veinlet by one edge and free on the other. 



10. ASPLENITJM. Sori on the upper side of the fertile veinlets, less commonly on both sides of them. Veins 

 free in our species. 



11. SCOLOPENDRIUM. Sori linear, straight, confluent in paiis, borne facing each other on contiguous veins, 

 the two indusia meeting by their free edges over the sporangia, and at length disclosing the. latter between 

 them. Fronds simple and veins free in our species. 



12. CAMPTOSORUS. Veins reticulated, many of the sori continuous along two or three sides of the areoles, 

 and therefore bent or angled ; other sori opposite and facing each other in pairs, and some single on either 

 the upper or lower sides of the veins. Fronds simple, the apex slender and elongated. 



Tribe VI. Aspidia*. Sori round or roundish, on the back, or sometimes at the tip, of the fertile veinlets, 

 naked or provided with a special indusium. Stalk not articulated to the rootstock, the tropical genus 

 Oleandra excepted. 



* Fa-til, mill si, ril, fronds nearly alike ; receptacU not elevated. 

 t Indusium none. 



13. PHEGOPTERIS. Sori dot-like, minute. 



f f Indusium orbicular or reniform. 



14. ASPIDIUM. Sori round, borne on the back or at the apex of the veinlets ; indusium attached at the centre. 



