HORNEOPHYTON LIGNIERI

Contents

CLASSIFICATION OF HORNEOPHYTON LIGNIERI

Kingdom :- Plantae

Division :- Pteridophyta

Sub-division :- Psilophytopsida

Class :- Rhyniopsida

Order :- Rhyniales

Family :- Rhyniaceae

Genus :- Horneophyton

Homeophyton with one species H. lignieri was found with Rhynia in the Rhynichert bed of Aberdeenshire, Scotland. It was previously named as Homeo.
The rhizome was a lobed parenchymatous body bearing non-septate rhizoids but with no continuous vascular strand of its own
The rhizome gave rise to upright shoots which ranged from 1 to 2 mm. in diameter and were dichotomously branched.
Sporangia were borne on the tips of these branches and were 1 to 2 mm in diameter and 2 or more mm in length.

The sporangium was oval or slightly cylindrical spore sac, somewhat pointed distally.
The sporangial wall consisted of a cuticularised epidermis followed by several layers of thin walled cells. The innermost layer was a well defined tapetum.
The most striking feature was the presence of central columella projecting into the spore cavity from the base. The columella was continuous with the phloem of the main stem.
Surrounding the columella and within the sporangial wall were many spores.
The spores were about 50 m in diameter and occur as tetrads.

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.
Order– Psilophytales
1. Sporophyte dichotomously branched.
2. Sporangia generally borne singly.
Family – Rhyniaceae
1. Rhizoids unicellular, on rhizomes.
2. Aerial portion leafless.
Genus – Horneophyton
1. Rhizome-a lobed parenchymatous body
2. Rhizome without a continuous vascular strand of its own
3. Presence of columella in the sporanigum.