NOTE: This post replaces 10 January 2021, whose errors were corrected. Also, a few links were added or replaced. [Most Recent Update: 16 January 2021]

The Christmas Fern, Polystichum acrostichoides, in the un-glaciated lower Piedmont and Triassic basin of North Carolina, exhibits the diversity of color and form indicated below. erwin_pteridophilos (@erwin_pteridophilos) advised that the source of the variation may at least in part be due to the expression (phenotypic re-emergence) of ancestral genes. This appears to be corroborated by observations of individual Polystichum acrostichoides with completely separate fertile fronds (unlike the usual situation in Polystichum acrostichoides where the fertile section is located at the end of an otherwise sterile frond), and in individuals with twice-divided fronds (unlike the usual once-divided fronds of this species).

What variation occurs in previously glaciated realms? Are populations there more diverse? Less diverse? Differently diverse?

I have not encountered (observed) individuals with long, wide pinnae (leaflets) outside of the Triassic Basin, and then only in lowland mesic areas. They are absent (or scarce?) in adjacent uplands where usual forms still abound.

(1) Green
(2) Darkest Green
(3) Blue-green
(4) Bicolor
a. Blue-Green blade with green central vein
b. Bright Edge

a. Shallow Serration
b. Shallow-Lobe
c. Lobed
d. Twice Divided, lobes which themselves are lobed
e. crested/fasciated leaflets, edges terminate in multiple divisions
a. Straight-ish; usual
b. Curved, sometimes doubly so (recurved)
c. Undulate (“crisped” in old parlance)
a. Short: less than 2 inches
b. Usual: about 2 inches (5 cm) long
c. Long: much longer than 2 inches
a. Usual: leaflets about 3/8ths inch (1 cm) wide when 2 inches (5 cm) long
b. Narrow (relative to length)
c. Wide relative to length
(5) TIP
a. Acute, pointed – usual case for mature plants
b. Blunt, rounded – all young plants
c. Divided, also called “crested”
(6) EAR, auricle: located near the stem-side of the leaflet, points toward the stem tip.
a. Short - wider than tall
b. Usual - about as tall as wide
c. Tall - taller than wide
d. Separate - as a lobe, usually restricted to lower (basal) leaflets
(7) GAP (between adjacent leaflet edges)
a. Slight gap, usual
b. Wide gap
c. Overlapping, or touching along long edge

a. Miniature: plants fertile when small, remain small in old age
b. Short
c. Usual frond length
d. Long, larger plants
a. Various, upright & lateral
b. Upright
c. Lateral
a. Unbranched, usual condition
b. Branched near apex of frond
c. Branched at base of frond

(1) Combined with sterile frond
a. Fertile portion of frond constricted in comparison to the infertile leaflets of the same frond; fertile portion of frond restricted to the top of the frond; fertile portion of frond shorter than the sterile portion
b. Fertile portion of frond gradually blends into the lower infertile portion of frond; fertile portion of frond equals or somewhat exceeds length of sterile portion
(2) Separate fertile frond

Publicado por mjpapay mjpapay, 13 de enero de 2021
Vida Silvestre es una entidad asociada a la Organización Mundial de Conservación