588 FILICES. (FERNS.) 



young) by a membrane called the indusium, growing either from the back 

 or the margin of the frond. (Tab. 9-12.) 



TRIBE I. POLYPODIES. Fructification dorsal, naked, entirely destitute of any in- 

 dusium, in roundish separate fruit-dots. 



1. POLYPODIUM. Fertile fronds like the sterile ones, wholly leaf-like, not rolled up. Fruit- 



dots scattered on the back, borne each on the end of a veinlet. 



2. STllUTIIIOPTERTS. Fertile frond very different from the sterile, contracted and rigid, its 



pinnate divisions rolled up from each margin into a closed necklace-like body, conceal- 

 ing the fruit-dots within, which are borne on the middle of a vein. 



TRIBE II. PTERIDE^E. Fructification marginal or intramargiiial, provided with a 

 general indusium formed of the (either altered or unchanged) margin of the frond, aud 

 which is therefore free and opens on the inner side, towards the midrib, transverse as 

 respects the veins. Venation in our genera free. 



* Indusium continuous, consisting of the entire reflexed and altered (scarious-membranaceous) 



margin of the fertile frond or of its pinnae or pinnules. 

 8. ALLOSORUS Sporangia borne on the free and separate extremity of the veins or veinlets, 



becoming confluent laterally. Indusium broad. 

 4. PTEHIS. Sporangia borne on a continuous receptacle, in the form of a slender marginal 



line, which connects the tips of the veinlets. 



* * Indusium the summit or margin of a separate lobe or tooth of a fertile frond or of its 



divisions turned over. Sporangia borne on the free ends of the veins or veinlets. 

 6. ADIANTUM. Sporangia borne on the under side of the strictly reflexed indusium. Mid- 

 rib of the pinnules marginal or none. 



6. CHEILANTHES. Sporangia borne on the frond, the unaltered herbaceous summit or 



margins of the lobes of which are recurved to form an imperfect involucre. Midrib 



central. 



TBIBE III. BIjECIINE^l. Fructification dorsal ; the oblong or linear fruit-dots borne 

 on cross veinlets parallel to the midrib, transverse as to the principal veins, covered with 

 a special indusium (entirely separate from the margin of the frond), which is fixed by 

 the edge that looks towards the margin, but free and opening towards the midrib. 



7. WOODWARDIA. Fruit-dots oblong or linear, distinct or contiguous : veins more or less 



reticulated. 



TRIBE IV. ASPIjENIE.35. Fructification dorsal; the more or less elongated fruit- 

 dots borne on the back of the frond, on direct veins oblique or at right angks to the mid- 

 rib and margins, each with a special iudusiuui fixed to the fruitful vein by one margin, 

 and free aud opening at the other. 



8. CAMPTOSORUS. Veins reticulated except near the margin. Fruit-dots irregularly scat- 



tered over the frond, inclined to approach in pairs. 



9. SCOLOPENDKIUM. Veins simply forked, straight and free. Fruit-dots linear, confluent 



in pairs, which appear like a single one with a double indusium, opening down the 

 middle 



10. ASPLENIUM. Veins forked and free. Fruit-dots oblique, separate, each on the upper 

 (inner) side of a vein, rarely some of them double, when the two indiusia are on tho 

 same vein, back to back. 



TRIBE V. DICKSONIE.52. Fructification marginal: fruit-dots roundish, borne on 



the apex of a free vein, furnished with an iudusiuui in the form of a cup, open at the 



top, formed in part of (or confluent with) a toothlet or portion of the margin of the frond. 



U. DICKSONIA SITOLOBIUM. Indusium hemispherical-cup-shaped or almost globular. 



membranaceous. 



TRIBE VI. WOODSIEJE. Fructification dorsal : the globular fruit-dots borne on tbo 

 back of a free vein, furnished with a spi-rial (sometii IBS evanescent) indusium in tkeioim 

 of a membrane attached underneath all round, and bursting open ut the top. 



