NOTICE: This journal page - Variation in Polystichum acrostichoides - is released from copyright restriction of the author, Michael Papay (mjpapay iNaturalist) so that it may be copied, modified, and made use of by other iNaturalist members who wish to document variation in Polystichum acrostichoides in their region, or wish to adapt this page for documentation of variation in other taxa. Michael Papay (mjpapay iNaturalist) 26 January 2021.

NOTE: This journal post replaces that of 10 January 2021, whose errors were corrected. Also, a few links have been added or replaced. Most Recent Update: 26 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.
6a. Acroscopic: on upper edge of leaflet and points toward the stem tip - usual condition.
i. Short - wider than tall
ii. Usual - about as tall as wide
iii. Tall - taller than wide
iv. Separate - as a lobe, usually restricted to lower (basal) leaflets
6b. Basioscopic: on lower edge of leaflet and points toward base of stem
(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

Lähettänyt mjpapay mjpapay, 13. tammikuuta 2021 00:57