588 FILICES. (FERNS.) 



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

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



TaiBB I. POI.YPODIE.flE. Fructification dorsal, naked, entirely destitute of any in- 

 dusiuin, iu 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. 8TKUTIIIOPTEKIS. 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 intrauiarginal, provided with a 

 general iudusium formed of the (either altered or unchanged) margin of the frond, and 

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

 respects the veins. Venation in our genera free. 



Indusiuui continuous, consisting of the entire reflexed and altered (scarious-menibranaceoufl) 



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

 8. ALLOSORUS Sporangia borne on the free and separate extremity of the veins 01 veinlets, 



becoming confluent laterally. Indusiuui broad. 

 4. PTEKIS. Sporangia borne on a continuous receptacle, in the form cf a slender marginal 



line, which connects the tips of the v inlets. 



* 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 end.s of the veins or veinlets. 



6. AD1ANTUM. Sporangia borne on the under side of the strictly reflexed indusium. Mid 



rib of the pinnules marginal or none. 



<J. CHEILANTIIES. Sporangia borne on the frond, the unaltered herbaceous summit ot 

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

 central. 



TRIBE III. BL.ECII1VE.3E. 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 flici 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 leaa 



reticulated. 



TMBB IV. ASPLENIE^E. Fructification dorsal; the more or less elongated fruit- 

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

 rib and margins, each with a special iudusium fixed to the fruitful veiu by one margin, 

 and free and opening at the other. 



8. CAMPTOSOKUS. Vtins reticulated except near the margin. Fruit-dots irregularly scat- 



tered over the frond, inclined to approach in pairs. 



9. SCOI-Ol'ENDllIUM. Veins simply forked, straight and free. Fruit-dots linear, confluent 



in i>airs, which appear like a single one with a double iudu.Mum, opening down the 

 middle 



10. ASPLEXiUM. 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 indusia ar on tho 

 same vein, back to back. 



TUBE V. DICIiSOariEjE. Fructification marginal: fruit-dots roundish, borne on 



the apex of a free veiu, furnished with an iudusium in the form of a cup, open at the 



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



11. DICKSONIA SITOLOB1UM. Indusium hemispheru-al-cup-fliaped or almost globular. 



niembrau:iceous. 



TEIBK VI "WOODSIE^E. Fructification dorsal : the globular fruit-dots borne on th 

 back of a free vein, furnished with a special (soinetiries evanescent) iiidu-ium ia tlio toi m 

 Of a membrane attact-ed underneath all round, and bursting open at the tup. 



