RHYNIA

CLASSIFICATION OF RHYNIA

Kingdom :-  Plantae

Division :- Pteridophyta

Sub-division :- Psilophytopsida

Class :- Rhyniopsida

Order :- Rhyniales

Family :- Rhyniaceae

Genus :- Rhynia

EXTERNAL FEATURES OF RHYNIA​

• Rhynia is a fossil member (not found living in the present age), discovered from Rhynichert Beds (or upper Devonian era) in Aberdeenshire of Scotland, by Kidston and Lang in 1917. 
• The two species R. major, about 40-50 cms in height and R. gwynne-vaughani, about 20 cms in height, found at this station, were well preserved, hence their form and structure are well known. 
• The plant grew in swampy marshes. It was differentiated into horizontally creeping rhizome and an upright branched shoot without leaves.
• There were no roots. Unicellular rhizoids were borne in patches, on underside of the rhizome. 
• The upright branches were dichotomously branched and gradually tapering. The sporangia terminated these branches.

ANATOMY OF RHIZOME AND AERIAL SHOOT​

• Both aerial branches and rhizome were differentiated into epidermis, cortex and stele. 
• The epidermis was cuticularized with stomata scattered on the aerial shoot. They were absent from the rhizome. 
• The cortex was differentiated into outer and inner zone. 
• The outer cortex was only 1-4 layered and had compact parenchymatous cells.
• The inner cortex had spherical cells with large intercellular spaces. The inner cortex is believed to be the chief photosynthetic region of the plant.
• The stele was a typical protostele with xylem completely surrounded by phloem.

REPRODUCTIVE ORGAN OF RHYNIA​

• It was nearly oblong in shape, broad at the base and pointed at the apex.
• The wall of the sporangium was several layered, of which two could be easily distinguished. 
• The outer wall was cuticularized and the innermost acted as tapetum.
• Inside the sporangium were spores, all of which were of the same size. Spores in tetrads were also seen in some specimens. 
• Columella was absent from the sprangium.

IDENTIFICATION OF RHYNIA

• DIVISION – Pteridophyta
  1. True roots generally present (except in Psilopsida),
  2. True vascular strand present.
• Sub-division :- Psilophytopsida
  1. True roots absent.
  2.  Shoot differentiated into subterranean rhizome and apical portion.
  3. Sporangia borne terminally.
  4.  Homosporous.
• Order – Psilophytales
  1.  Sporophyte dichotomously branched.
  2.  Sporangia generally borne singly.
• Family – Rhyniaceae
  1. Rhizoids unicellular, on rhizomes.
  2. Aerial portion leafless.
• Genus – Rhynia
  1. Subterranean portion not corm-like.
  2. No columella in sporangia.

REFERENCES

• https://en.wikipedia.org/wiki/Rhynia
• https://www.shutterstock.com/search/rhynia
• Text book of practical :- botany