British ferns (Filicopsida)
Microsorum diversifolium (Willd.) Copel.; Phymatosorus diversifolius (Willd.) Pic. Serm.; probably = Microsorum pustulatum (G.Forst.) Copel.
Sporophyte. The rhizomes fleshy, fragile, stout; creeping; bearing scales (these appressed, deciduous). Plants with no clear distinction into fertile and sterile leaves (but sometimes heterophyllous, with the leaves variable in form on the same rhizome).
Leaves in two rows, distributed along the rhizomes; to 20–60 cm long; simple; entire to conspicuously, pinnately lobed (sometimes from entire juvenile to very deeply pinnately divided mature fronds on the same plant). The petioles shorter than the blades to longer than the blades; jointed and ultimately abscising at the point of attachment to the rhizome; vascularised by several discrete strands. Leaf blades in outline ovate, or lanceolate; leathery. The venation of the lamina invisible in the whole, fresh leaf, but reticulate (with the free vein endings in the numeous areolae terminating in hydathodes).
The sporangia exposed; aggregated in sori. The sori sub-orbicular (in a row on either side of the main midrib and of the midribs of the main lobes); remaining discrete at maturity; perceptibly sunken and creating conspicuous rows of circular impressions on the upper surface of the lamina; naked and neither indusiate nor pseudo-indusiate. Paraphyses present in the sporangia (in material seen). The sporangia with a vertical annulus. The mature spores monolete; without a perispore.
Distribution and habitat. In damp places in woods, and on shady walls. Naturalized. Native to Australasia, naturalized in S Kerry, Guernsey and the Isles of Scilly.
Vice-county records. Britain: West Cornwall, Channel Islands. Ireland: South Kerry.
Classification. Family Drynariaceae (Swale and Hassler); Polypodiaceae (Stace). Order Polypodiales (Swale and Hassler).
Comments. It may be preferable to treat Phymatosorus and Phymatodes as synonyms of Microsorum (cf. Bostock and Stokes, 1998). Furthermore, the current name of the British representative appears to be Microsorum pustulatum (G.Forst.) Copel.
Illustrations. • Phymatodes diversifolia: close-up views of leaf, with details of sori.
To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2004 onwards. British ferns (Filicopsida). Version: 4th January 2012. http://delta-intkey.com’.