FAM. 3. 21 



P. Cretica. Leaves ternate or pinnate, smooth, ovate. Shady woods. 

 5. Indusmm double, --------- Pteridium 



P. aquilinum (, Pteris aquilina), Bracken or Brake Blades large, ternate, the 

 three divisions each bi-pinnate, the terminate pinnules often elongated. 

 In sunny places. 

 A cultivated variety of Pteris is the beautifully striped albolineata; other species 

 of the greenhouse are P. serrulata, P. tremula, etc. 

 7. Sori linear, more than twice as long as broad, ------ 8 



7. Sori roundish, - - - - ---- --n 



S. Sori parallel to the midrib, ---------9 



8. Sori oblique to the midrib, - - - - - - Asplenium, Spleenwort 



a. Blades pinnate, sori straight, --------b 



a. Blades 2-pinnate, sori curved. A. Filix foemina, Lady-fern. In low shady woods. 



b. Rachis brown or black, leaflets auricled, ------ c 



b. Rachis green, leaflets crenate, - - - A. dentatum. In sandy soil 



c. Leaflets mostly opposite, - - A. resiliens (parvulum). On limestone 

 c. Leaflets mostly alternate, - A. platyneuron (ebeneum). On shady rocks 



9. Veins free, sori more or less continuous, - - - - Blechnum 



B. serrulatum (angustifolium). Petioles rigid; leaves long and leathery, with 

 12-24 pairs of leaflets, the fertile leaves narrower than the sterile ones. 

 Coarse swamp-ferns. 



9. Veins reticulate, sori interrupted. - - - -- --10 



10. Leaves of the same kind, -------- Anchistea 



A. (Woodwardiaj Virginica. Petioles stout, darker below; blades pinnate, leath- 



. ; veins reticulate along the midrib, free toward the margin. In swamps 

 and shallow ponds. 



10. Leaves of two kinds. -------- Lorinseria 



L. areola ta (Woodwardia angustifolia). Fertile blades on longer petioles than 



the sterile ones; the segments of the latter making a broader wing along 

 the rachis than those of the former. In swamps and low grounds. 



11. Sori on the back of the veins, -------- \2 



11. Sori at the ends of free veins, - - Nephrolepis 

 Nephrolepis with long pendent or spreading blades and numerous leaflets is 



an epiphytic genus from South Florida, but has several cultivated spec- 

 ies, as N. Davallioides furcans {Boston Staghorn), N . exaltata (Sword- 

 fern), with the varieties Bostonensis (Boston Fern), and crista ta {Crested 

 Boston Fern), N. rufescens tripinnatifida (Ostrich Feather), etc. The 

 true Staghorn-ferns belong to the genus Plarycerium. 



12. Indusium orbicular and peltate, fixed by the center; veins free, Polystichum 

 P. Aspidiumi acrostichoides, Christmas Fern. Petioles very chaffy; blades 



pinnate, leaflets with spiny teeth; sori copious. In rocky woods. The 

 P. capense is a cultivated species, while Cyrtomium falcatum, Holly 

 Fern, single or crested, is closely related. 

 12. Indusium cordate-reniform, fixed at the sinus, - - Dryopteris, Shield Fern 

 D. Aspidiumi Thelypteris. Rootstock slender; blades thin, scarcely narrowed 

 at the base, leaflets deeply pinnatifid, margin o£ fertile segments strongly 

 revolute. veins forked; sori crowded. In swamps. 

 D. Aspidium/ patens. Rootstock stout; blades long. thin, pubescent beneath, 

 leaflets deeply pinnatifid. veins simple; sori near the margin, indusia small, 

 pubescent. In shady woods. 



