''Jamesonia'' is a genus of
fern
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...
s in the subfamily
Pteridoideae of the family
Pteridaceae
Pteridaceae is a family of ferns in the order Polypodiales, including some 1150 known species in ca 45 genera (depending on taxonomic opinions), divided over five subfamilies. The family includes four groups of genera that are sometimes recogni ...
. It now includes the formerly separate genus ''Eriosorus''.
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Description
Species of ''Jamesonia'' are terrestrial or grow on rocks. They vary considerably in their detailed morphology. The rhizomes are short, dark brown, and creeping, with a more or less dense covering of hairs and bristles. The fertile and infertile frond
A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...
s are similar. Species show one of two different frond morphologies, related to habitat. These were formerly used to distinguish ''Jamesonia'' and ''Eriosorus'',[ but do not correspond to the evolutionary history of the species.][ Species with "''Jamesonia''-type" morphology have many fronds with short, often leathery ]pinnae
The auricle or auricula is the visible part of the ear that is outside the head. It is also called the pinna (Latin for "wing" or " fin", plural pinnae), a term that is used more in zoology.
Structure
The diagram shows the shape and location ...
, and are associated with exposed habitats. Species with "''Eriosorus''-type" morphology have fewer fronds with longer, thinner pinnae, and are associated with more sheltered areas including cloud forests. The stalks ( petioles and rachises) of the frond are dark brown and usually grooved on the upper (