#pteridophytes

• Amphiphloic — Having or characterized by the presence of phloem tissue on both sides of the xylem; an adjective used in plant anatomy to define a structural type of central cylinder (amphiphloic siphonostele or solenostele), commonly found in ferns, where the central pith is successively surrounded by an inner ring of phloem, a central ring of xylem, and an outer ring of phloem.
• Anemia mandioccana — A species of perennial fern in the genus Anemia, family Anemiaceae, endemic to the humid tropical forests of Brazil (notably the Atlantic Forest biome). This structural botanical entity is characterized by short, creeping rhizomes, pinnately compound sterile fronds with rigid ovate segments, and an erect fertile axis branched at the base elevating the sporangia-bearing panicles.
• Anemia phyllitidis — A species of perennial fern in the family Anemiaceae, native to the tropical regions of Central and South America. This botanical entity is structurally distinguished by its pinnately compound sterile fronds, whose segments resemble those of the genus Phyllitis, and by the presence of two elongated, erect fertile segments modified exclusively for spore production and dispersal.
• Anemia tomentosa — A species of perennial fern in the family Anemiaceae, native to the dry tropical and subtropical regions of South America and parts of the West Indies. This plant is structurally characterized by a dense indumentum of long, reddish or brown hairs (tomentum) covering the rhizome and fronds, acting as an effective protective barrier against dehydration in its rocky, arid habitats.
• Angiopteris — A genus of giant tropical terrestrial ferns, belonging to the Marattiaceae family, characterized by massive, bipinnate fronds that can reach remarkable structural lengths of several meters, and fleshy, globose rhizomes. This well-defined taxonomic entity, typically represented by the species Angiopteris evecta, constitutes an archaic group of flowerless vascular plants (pteridophytes), considered a true living fossil due to the conservation of morphological characters from ancient geological times.
• Angiopteris evecta — A species of giant terrestrial fern in the Marattiaceae family, native to the tropical regions of Australia, Southeast Asia, and Oceania, recognized as one of the largest ferns in the world due to its spectacular bipinnate fronds that can reach lengths of up to 6-9 meters. This well-defined taxonomic entity thrives in warm, humid rainforests, possessing a massive fleshy rhizome and sporangia grouped into synangia, and is considered an archaic plant of significant importance for studying pteridophyte evolution.
• Anogramma — A genus of small, terrestrial ferns in the Pteridaceae family, characterized by finely dissected fronds and an annual or ephemeral lifecycle unusual for pteridophytes. The best-known species is Anogramma leptophylla, a unique structural plant that survives from year to year primarily as a perennial tuberous gametophyte, colonizing damp, shaded, rocky soils in Mediterranean and temperate climates.
• Anogramma leptophylla — A unique species of small fern in the Pteridaceae family, remarkable for its annual or ephemeral life cycle, an atypical phenomenon among pteridophytes. The plant possesses thin, delicate, translucent fronds, but its ultimate structural feature is that the sporophyte regularly dies off during the dry season, survival from year to year being secured by a perennial tuberous gametophyte colonizing shaded rocky niches in Mediterranean and temperate zones.
• Apogamic — Pertaining to apogamy, specific to the asexual developmental process where a sporophyte arises from a gametophyte cell without prior fusion of sexual gametes; synonymous with apogamous. In plant histology, the term characterizes embryonic structures that maintain chromosomal consistency by avoiding typical syngamy phases, opening alternative pathways for natural cloning.
• Genus Asplenium — A major taxonomic genus of ferns in the Aspleniaceae family, popularly known as spleenwort; it comprises over 700 cosmopolitan species, either epiphytic or terrestrial, adapted to shaded environments, limestone rocks, and tropical tree bark. It is characterized by short rhizomes, often leathery leaves (either entire or divided), and elongated sori arranged obliquely along the secondary veins, globally cultivated as hardy ornamental plants.
• Asplenium decorum — An exotic fern species in the genus Asplenium, found in isolated tropical or island regions (such as certain zones within Pacific Ocean archipelagos). This plant is characterized by a compact growth habit and fronds with an extremely ordered, elegant, and symmetrical geometry, a refined structural appearance from which the specific epithet 'decorum' (decorative / elegant) originates. It is a rare species, studied primarily in niche botanical monographs.
• Asplenium dimorphum — A rare species of perennial fern in the Aspleniaceae family, endemic to Norfolk Island in the Pacific Ocean, popularly known as the two-branched spleenwort. It stands out due to its spectacular structural phenomenon of foliar dimorphism, developing two completely different types of fronds on the same plant: the sterile ones are broad, glossy, and partially divided, while the fertile fronds, which bear the spores, are finely dissected into thread-like segments, giving the plant a highly distinctive exotic look.
• Asplenium trichomanes — A species of small, perennial fern in the Aspleniaceae family, popularly known as maidenhair spleenwort. It is a cosmopolitan plant that grows in the crevices of shaded limestone or siliceous rocks and on old stone walls. It is easily recognized by its long, narrow, simply pinnate fronds with rounded or oval leaflets attached to a rigid, glossy, dark brown to black stipe, which persists on the plant even after the green segments have withered.
• Athyrium alpestre — A specific species of fern in the Athyrium genus (synonymous with Athyrium distentifolium), commonly known as the alpine lady-fern. This plant grows at high altitudes, in rocky areas, damp screes, subalpine forests, and open ridges, adapted to harsh climate conditions and characterized by small, round sori often completely lacking an indusium.
• Athyrium filix-femina — A representative fern species in the Athyrium genus, commonly known as the lady-fern. It is a common perennial plant in shady, damp forests of the Northern Hemisphere, recognized by its large, highly elegant, finely divided fronds and elongated or crescent-shaped sori protected by a characteristic horseshoe-like indusium.