DESCRIPTIVE FLORA 



DIVISION I. PTERIDOPHYTA 

 (FERNS AND FERN ALLIES) 



Male generative cells (spermatozoids) spirally coiled motile bodies, 

 not developing into a tube. Plants with more or less distinct alter- 

 nation of generations. The sexual stage, a small thalloid body ; the 

 asexual provided with vascular tissue and (with rare exceptions) 

 differentiated into stem and leaves (fronds), some of these modified 

 to bear asexual reproductive bodies or spores (without embryo), 

 which again give rise to the sexual generation. Often called 

 Vascular Cryptogams or Higher Flowerless Plants. 



HYMENOPHYLLACEAE (FILMY FERN FAMILY) 



Delicate ferns with slender often filiform creeping rootstocks. Fronds 

 pellucid, of a single layer of cells. Sporangia sessile on a bristle-like receptacle 

 within a cup-shaped, tubular, or bivalvular involucre, from the apex of a vein, 

 the ring transverse and complete. Chiefly tropical, inhabiting damp places, 

 often epiphytic. Fronds circinate in vernation. 



1. TRICHOMANES L. FILMY FERN 



Involucre tubular-funnel-shaped, the mouth nearly or quite truncate. Spo- 

 rangia bursting vertically. Ours a small creeping fern with much divided 

 fronds. (An ancient Greek name for some fern.) 



1. T. Boschianum. Sturm. Fronds oblong-lanceolate, 1-2 dm. long, 12-35 mm. 

 wide, bipinnatifid ; rhachis narrowly winged ; pinnae triangular-ovate, the divi- 

 sions toothed or again lobed ; capillary receptacle often much exserted. ( T. rad- 

 icans Man. ed. 6, not Sw.) On moist and dripping sandstone cliffs, Ky. to 

 Ala. 



POLYPODlACEAE (FERN FAMILY) 



Leafy plants (ours herbaceous), with creeping rhizomes. Spores borne in 

 sporangia (spore-cases), these collected in dots, lines, or variously shaped clusters 

 (sori or fruit dots) on the back or margins of the frond or its divisions, cellular- 

 reticulated, stalked, 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 

 GRAY'S MANUAL 3 33 



