Classification
Class
Polypodiopsida
Subclass
Polypodiidae
Order
Polypodiales Link
Family
Blechnaceae Newman
Genus
Blechnum L.
 Nomenclature
Scientific Name:
Blechnum ×digenum (Parris) Brownsey & Perrie, New Zealand J. Bot. 57: 240 (2019)
Synonymy:
  • ≡ Doodia ×digena Parris, New Zealand J. Bot. 10: 596 (1972)
Holotype: Kitekite Falls, Piha, Auckland, B.S. Parris, 26 May 1966, CHR 202054!
Etymology:
From the Latin digenus (of two kinds), a reference to the hybrid origin of this plant.
 Recognition

Blechnum ×digenum is believed to be the hybrid between B. molle and B. parrisiae, usually arising wherever the two parent species occur together. It is recognised by its intermediate morphology. The fertile and sterile fronds are dimorphic, unlike those in B. parrisiae. The fronds are harsh, and the rachises bear scales, unlike those in B. molle. There are 22–30 pairs of pinnae, intermediate between the range of 11–21 in B. molle and 20–50 in B. parrisiae. The pinnae at mid-lamina are stalked, rather than sessile or adnate as in B. parrisiae. Spores in some hybrid plants (e.g. WELT P017873, Wairua Falls near Whangārei, and WELT P015771, Pukemokemoke) are of very irregular sizes (but not shrivelled and aborted); others appear normal, as reported by Parris (1972).

 Biostatus
Indigenous (Endemic)
 Cytology

n = >30 univalents + >60 bivalents (Brownlie 1961– as intermediates between Doodia caudata and D. media). The presence of bivalents and univalents strongly suggests that the spores would be sterile.

 Bibliography
Brownlie, G. 1961: Additional chromosome numbers – New Zealand ferns. Transactions of the Royal Society of New Zealand. Botany 1: 1–4.
Brownsey, P.J.; Perrie, L.R. 2019: Taxonomic notes on the New Zealand flora: lectotypes and a new combination in Blechnaceae. New Zealand Journal of Botany 57(4): 238–248.
Brownsey, P.J.; Perrie, L.R. 2021: Blechnaceae. In: Breitwieser, I. (ed.) Flora of New Zealand — Ferns and Lycophytes. Fascicle 29. Manaaki Whenua Press, Lincoln.
Parris, B.S. 1972: The genus Doodia R.Br. (Blechnaceae: Filicales) in New Zealand. New Zealand Journal of Botany 10: 585–604.
Parris, B.S. 1980: Further notes on Doodia, Grammitis, and Blechnum (Filicales). New Zealand Journal of Botany 18: 145–147. [as Doodia ×digena Parris]