DESCRIPTIVE FLORA 



DIVISION I. PTEKIDOPHYTA 

 (FEKNS 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. 



POLYPODIACEAE (FERN FAMILY) 



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

 ' - 'ille.cted in dots, lines, or variously shaped </!/.?< iv* 



(sori or fruit dots) on < margins of the frond or its divisions, cellulnr- 



stalked, tl- -i'tlk running into a vertical incomplete many-jointed 

 ring, which ,<j at maturity ruptures the sporangium trans* 



on the inner side, discharging the spurm. Fruit dots often covered (at least 

 CRAY'S MAMAL 3 33 



