1.  vascular plants with neither flowers nor seeds
2.  spores are produced via meiosis in sporangia (or sporangial clusters known as sori - photo)
3.  spores are usually released from the parent plant (diploid sporophyte) to produce haploid, free-living (not dependent on sporophyte, usually photosynthetic) gametophytes (photo)
3. as opposed to flowering plants, gametophytes usually develop outside the spore (exosporic) and
both gamete-producing organs (antheridia, archegonia) are usually present (see text fig. 8-1, p. 94 and overview from Ohio State)
4. gametes (sperm free-living, motile)
5. embryo/sporophyte - dominant

 EUSPORANGIATE - a large sporangium developing from several initial cells producing many spores.  These are sometimes fused to form synangia.

 LEPTOSPORANGIATE - small, specialized sporangia developing from a single initial cell producing a small, definite number (< 128) of spores.  These often occur in a cluster (sorus) that is often covered by a flap of tissue known as an indusium (photo)
 

PSILOTACEAE  (Whisk Fern Family) - two genera (Psilotum - pan-tropical- and Tmesipteris - Oceania and Australasia) with about 4-8 species - terrestrial or epiphytic perennials. Only Psilotum nudum in Texas. A leafless (leaf-like projections = ENATIONS), rootless (rhizoids) photosynthetic stem with eusporangia  (synangia) and subterranean, mycotrophic gametophytes. Either a very primitive remnant of an ancient line, possibly basal to the vascular plants, or a highly specialized version of the "true" ferns. Currently a debate. Images from:   Australian National Botanic Gardens, Department of Botany, University of Wisconsin (Madison), and University of Hawaii Botany

Equisetaceae (Horse Tail or Scouring Rush Family) - a single genus - Equisetum - with 35 species, worldwide distribution; 4 species in Texas and 11 in the FNA. Perennial, rhizomatous herbs of moist places with jointed, ridged, cylindric stems; reduced-scalelike leaves connate to form a nodal sheath, eusporangia aggregated into a terminal STROBILI [termed "cones" in Correll and Johnston (1979)]. Gametophytes photosynthetic - can be unisexual. Easy to identify, the last of a line that was much more diverse prior to the rise of the flowering plants. Images from the Department of Botany, University of Wisconsin (Madison),the Vascular Plant Image Gallery, and University of Hawaii Botany

CLASS Lycopodiopsida (note class ending)
 
 
LYCOPODIACEAE (Club Moss or Gound Pine Family) - commonly treated as two genera Phylloglossum (1- Australia and New Zealand)) and Lycopodium (350-400 - cosmo - temperate - 4 species in Texas), but more recently (FNA) Lycopodium "split" into over 10 genera; FNA treats 7 genera (Lycopodium segregates)/27 species in NA. and 4 species in 3 genera in Texas. Microphyllous, homosporous with eusporangia in leaf axiles, often clustered a tips of dichotomously branching stems as STROBILI [STROBILUS]. Gametophytes either above or below ground, sometimes unisexual. Longest continuous fossil record of any vascular plant, make up most of the world's coal. Images from the Department of Botany, University of Wisconsin (Madison), the Vascular Plant Image Gallery, and the University of Hawaii Botany


CLASS Isoëtopsida
 

SELAGINELLACEAE - (Spike Moss Family) - single genus Selaginella of ca. 700 species (38 in the FNA) most diverse in tropical and subtropical regions of the world, 12 species in Texas, some adapted to quite xeric conditions ("resurrection plants"). Superficially similar to Lycopodium, but often prostrate, creeping with angular strobili. Distinctive by being heterosporous and endosporic. Images from the Department of Botany, University of Wisconsin (Madison), the Vascular Plant Image Gallery, and the University of Hawaii Botany.

ISOËTACEAE - (Quillwort Family) - a single genus (Isoëtes [150 species - worldwide - 24 in FNA and 2 in Texas] with one possible generic segregate (Stylites [1 species - Andes]). Largest microphylls of the Pteridophytes; perennial, often aquatic plants that have a tufted, grass-like aspect, typically occur in moist situations. Heterosporous (megaspores important in species identifications) and gametophyte development is endosporic. See the Vascular Plant Image Gallery and the Department of Botany, University of Wisconsin (Madison)

"True" ferns, the others are "allies".  Diverse and the subject of much taxonomic confusion - lumping vs. splitting. About 12,000 species worldwide. Major elements:
 

Subclass Ophioglossidae (note subclass ending)
 
Ophioglossaceae - 5 genera (three monotypic and two - Ophioglossum (Adder's tongue - 40, 5 in Texas) and Botrychium (Grape Fern - 50-60, 30 in FNA and 2 in Texas) common. Eusporangiate, homosporous with a strong leaf dimorphism (sterile (Sporophore) vs. fertile (Trophophore)) with eusporangia in "fertile spikes" and underground, micotrophic gametophytes. Images from the Department of Botany, University of Wisconsin (Madison) and the Vascular Plant Image Gallery.


 Subclass Polypodiidae
 

Osmundaceae (Royal Fern Family) - 3 genera (2 Old World) with Osmunda (10) having 2 species in Texas and 3 in FNA. Often placed as intermediate between eusporangiate and leptosproangiate ferns - a "cusp" taxon. Usually with striking leaf dimorphism (sporangia bearing vs. photosynthetic) - species are often good indicators of acid (often bogs) habitats. Images fromthe Department of Botany, University of Wisconsin (Madison) and the Vascular Plant Image Gallery.

"Other" Ferns: the largest and most diverse group - leptosporangiate, homosporous, variously classified, often (as in Correll and Johnston, 1977) put together as the Polypodiaceae (50 genera worldwide, 22 genera with 71 species in Texas - flora of Robertson county lists 9 genera with 10 species).  Fern leaf (frond) terminology:  PINNA [primary division of a pinnate leaf or leaflet], PINNULE [primary division of a PINNA], STIPE [= petiole].. Hatch, et al. (1990) Vascular Plants of Texas also include the Schizaeaceae (Curly Grass Family - Anemia, Lygodium), and the Parkeriaceae (Water Fern Family - Ceratopteris). Texas ferns listed by the Biota of North America Program "split" genera of the Polypodiaceae (s. lat.) into 7 additional families, a perspective followed by the FNA treatment. Images available on the network include:  


Pteridium aquilinum
Polypodium species
Polystichum acrostichoides
Asplenium species and
Tree Ferns


Subclass Marsileidae

 
Marsileaceae - Water Clover Family.  Sori within hard bean or pea-shaped bodies knows as SPOROCARPS.  Heterosporous (sori of both types in the sporocarp) and, as with the flowering plants, endosporic.  Spore germination occurs after rupture of the sporocarp wall. Subsequent hydration produces a gelatinous structure that carries the sori and spores into the water.  3 genera, ca. 50 species worldwide, 2 of these with 7 species in the FNA, two genera (Marsilea [4 species] and Pilularia [1 species]) in Texas.  Images from the Vascular Plant Image Gallery and the Department of Botany, University of Wisconsin (Madison).


Subclass Salviniidae

 
Salviniaceae and Azollaceae - Floating Ferns - [Azolla treated as Salviniaceae in Correll and Johnston (1979) - 2 genera, ca. 17 species worldwide, 1 Salvinia (FNA) and 2 Azolla (FNA) species in Texas) - heterosporous, endosporic and - showing a further elaboration of leaf dimorphism, sporangia born in "containers" made up of specialized leaves known as SPOROCARPS. Very distinctive ferns. Images from the Department of Botany, University of Wisconsin:  Azollaceae and Salviniaceae

Note:  Recent higher level revision of the classification structure presented here, as a phylogenetic 'hypothesis' based in part on molecular cladistics, suggests fundamental changes in major lineage relationships (see reprint - pdf file).