PTERIDOPHYTA* 



FERNWORTS. 



Plants of two distinct generations, in one consisting of a plant- 

 body (sporophyte), which has stems containing vascular tissue 

 and produces spores asexually, in the next, developing from the 

 spore, consisting of a thalloid-body (gametophyte or prothallium), 

 which bears the sexual reproductive organs (archegones and anther- 

 ids). The plant-body develops from the oosphere within the 

 archegone, after being fertilized by spirally coiled motile bodies 

 (spermatozoids), produced by the antherids. 



KEY TO THE FAMILIES. 



PAGE 



Leaves usually broad, entire or dissected, not scale-like; fern-like plants. 

 Spores of one kind, minute, borne in sporanges. 



Vernation not spirally coiled; sporangia ringless, leathery, opening by a transverse 



slit, arranged in spikes or panicles. 1. OPHIOGLOSSACEAE. 1038 



Vernation spirally coiled; sporangia membranous, provided with a ring, which 



opens elastically. 2. POLYPODIACEAE. 1040 



Spores of two kinds, minute microspores (male) and larger macrospores (female), 



borne in sporocarps. 



Plant rooting in the mud; leaves 4-foliolate, petioled. 3. MARSILIACEAE. 1050 

 Plant minute, floating; leaves entire or 2-lobed. 4. SALVINIACEAE. 1051 



Leaves scale-like or awl-like; moss-like or rush-like plants. 



Sporanges in an apical cone, borne under peltate bracts; stem usually hollow, rush- 

 like. 5. EQUISETACEAE. 1051 

 Sporanges in the axils of small leaf-like bracts; stem solid. 



Leaves awl-like, elongate, borne on a short thick corin-like caudex; water plants. 



6. ISOETACEAE. 1053 



Leaves scale-like, flat, borne on a distinct stem; land plants. 



Spores uniform, minute. 7. LYCOPODIACEAE. 1054 



Spores of two kinds, microspores and macrospores. 8. SELAGINELLACEAE. 1056 



FAMILY 1. OPHIOGLOSSACEAE. ADDER'S TONGUE FAMILY. 



Leafy succulent plants with fleshy rhizomes and fibrous, often fleshy, 

 roots. Leaves (fronds) erect to reflexed, but not coiled in vernation, con- 

 sisting of a sterile simple or compound leaf-blade and one or more stalked 

 spore-bearing spikes or panicles (sporophylls), all borne on a common stalk. 

 Sporanges bivalvular, formed from the interior tissue of the sporophylls. 

 Prothallia underground, not green, monoecious. Spores of one kind. 



1. BOTRYCHIUM Sw. MOONWORT. 



Terrestrial plants, with erect rhizomes and usually only one frond. Roots 

 clustered, fleshy. Common stalk with more or less of its length below ground, 

 the bud of the frond of the following year enclosed within its hollow base. Veins 

 free, forking. Sporophyll single. Sporangia distinct, globose, arranged in two 

 rows. 



Frond-bud without hairs. 



Sporophyll and sterile leaf-blade not completely bent down in the bud. 



Sporophyll erect in the bud, the sterile leaf-blade erect or with the apex bent over; 

 segments of the sterile leaf commonly cuneiform or fan-shaped. 



1. B. simplex. 



* Contributed by Miss Margaret Slosson, except the families Equisetaceae, Isoetaceae, 

 and Selaginellaeeae, and the key to the families. 



1038 



