Anogramma is a small genus of ferns belonging to the subfamily Pteridoideae within the family Pteridaceae (order Polypodiales, class Polypodiopsida). It contains three accepted species, the best known of which is Anogramma leptophylla (L.) Link, commonly called Jersey fern or annual fern.
The genus is notable for a biological trait that is extremely rare among ferns: the sporophyte generation of its leading species, A. leptophylla, completes its life cycle annually, dying back each year. The gametophyte, by contrast, is perennial and capable of remaining dormant for up to two and a half years, persisting underground until temperature and moisture conditions favour the emergence of a new sporophyte. This annual sporophyte strategy sets Anogramma apart from the vast majority of fern genera, in which the sporophyte is the long-lived, dominant generation.
Plants are characteristically small, rarely exceeding 8 cm in height. The fronds are delicate and two-pinnate; the inner fronds are fertile, carrying linear sori (spore-bearing structures) on the undersides of nearly circular leaflets, where they occupy most of the surface area. Leaf margins are not recurved, distinguishing Anogramma from superficially similar genera with indusiate or marginal sori.
The genus has a wide but oceanic-temperate distribution, centred on the Mediterranean basin and extending through Africa, southern and eastern Asia, Oceania, and the Americas as far south as South America. It favours walls, banks, and bare soil in moist but well-drained spots, particularly where underlying granite or warm microseepage creates a mild microclimate through winter.
Etymology
The name Anogramma derives from Greek roots: ana- (upward, along) and gramma (line or writing), referring to the linear arrangement of the sori along the veins on the frond undersides.
Distribution
Anogramma has an oceanic-temperate distribution spanning the Mediterranean basin, Africa, southern and eastern Asia, Oceania, Mexico, and Central and South America. In the British Isles, the sole occurrence is on the island of Jersey in the Channel Islands. Plants grow on walls, rocky banks, and bare soil, with a preference for moist, well-drained substrates — particularly where warm water seeps from crevices in granite — which moderates winter temperatures in otherwise cool climates.
Ecology
Anogramma leptophylla, the principal species of the genus, occupies warm, sheltered microhabitats alongside other heat-tolerant plants including pellitory-of-the-wall (Parietaria lusitanica), Mediterranean clubmoss (Selaginella denticulata), the liverwort Targionia hypophylla, and the mosses Rhynchostegiella tenella and Timmiella anomala. These associates share the same strategy of exploiting warm-water microseeps from rock crevices, which create a near-tropical microclimate enabling survival through winter at the northern edge of the genus's range. Because Anogramma is not strongly competitive, it is typically found on bare or sparsely vegetated soil rather than in closed vegetation.
Taxonomy Notes
Anogramma is placed in the subfamily Pteridoideae of the family Pteridaceae. Earlier classifications placed some members in the family Sinopteridaceae. The genus currently encompasses three accepted species: Anogramma leptophylla (L.) Link, Anogramma lorentzii (Hieron.) Diels, and Anogramma reichsteinii Fraser-Jenk. The annual sporophyte life cycle of A. leptophylla is cited as one of the very few confirmed examples of annual habit among ferns.
