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#annulus

2 public questions tagged with this topic.

Plant Classification

Vertical interrupted annulus is typical of

Advanced Polypodiales including Polypodiaceae, Pteridaceae, Aspleniaceae exhibit sporangia with vertical incomplete annulus interrupted by stomium lips and subtended by long slender stalk, enabling classic elastic ejection with coiling and sudden recoil in dry conditions. Primitive ferns like Osmunda have subterminal transverse annuli, Gleicheniaceae oblique, clubmosses lack annulus entirely having simple longitudinal dehiscence, horsetails possess sporangiophores with no annulus but spores with elaters. Vertical interrupted type reflects derived condition optimizing explosive mechanism and sy

Ref: Kramer & Green 1990; Tryon & Lugardon Spores of Pteridophyta; Advanced Ferns

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Plant Classification

Annulus in ferns is involved in

Annulus consists of specialized row of thick-walled hygroscopic cells with inner and radial walls heavily thickened with lignin in U-shaped pattern, forming arc partially encircling leptosporangium capsule on one side. Upon dehydration under low humidity, annulus cells lose water, contract differentially, storing elastic energy, then snap backward violently rupturing stomium region and ejecting spores catapult-like up to several centimeters into air stream. Nutrition or protection functions performed by tapetum and indusium, germination unrelated process. Presence and position provide taxonomi

Ref: Goebel Organography; Hollowell Fern sporangium mechanics, Ann NY Acad Sci; Campbell

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