Ancient Plant Rhynia's Classification and Life Cycle

Presented By…
Thakor Maitri M.
M.Sc. (Botany)
Department of Life Sciences,
H.N.G.U., Patan.
1

CONTENT
Introduction
 classification of Rhynia
 External features of the plant
 Internal features of the plant
 Sporangia of Rhynia
 Gametophyte stage in Rhynia
 Life cycle
2

INTRODUCTION
The fossils of the genus Rhynia
were discovered by Kidston and Lang
in 1917,1921 from the Rhynie locality
(chert) of Aberdeenshire in Scotland.
( in middle Devonian Era)
3

 According to Parihar (1996) the
chert deposites at Rhynie, originally
thought to be of middle Devonian are
now believed to be lower Devonian
(Late Siegenian or Emsian epoch –
about 390 to 374 million years ago.
The specimens are so well
preserved that they give detailed
information about the form and
structure of this very primitive
vascular plants.
Rhynia is a single- species genus
of Devonian Vascular plants.
4

CLASSIFICATION
Division : Pteridophyta
Sub Division : Psilophyta
Class : Psilophytopsida
Order : Psilophytales
Family : Rhyniaceae
Genus : Rhynia
5

EXTERNAL FEATURES OF THE PLANT
 Kidston and Lang(1951), thought and
supported by estimony that in those
times the plants grew in swampy
marshes near the volcanoes.
 The genus is named after the locality
and possess two species : (1)Rhynia
gwynne vaughani
(2)Rhynia major.
R. major & R. gwynne vaughani were
herbaceous plants.
R. major was larger than R. gwynne
vaughani.
6

 The plant was
differentiated into
horizontally cree-
ping rhizome & an
upright branched
shoot without -
leaves. There were
rootless.7

 The aerial stem of R. major were
around 50 cms high and 1.5 mm to 6
mm in diameter , whereas, the
corresponding structures of R.
gwynne vaughani were 20 cms in
height & 1 to 3 mm in diameter.
 The aerial branches were
cylindrical, naked, leafless,
dichotomously forked & tapering at
their apices.
The aerial branches end in tapering
vegetative apices or bore pear –
shaped terminal sporangia.
8

INTERNAL FEATURES OF THE PLANTS
The internal organization (anato-my)
of the rhizome as well as of the aerial
stem was practically similar in both
species of Rhynia except that some
of the slenderest twigs of R. gwynne
vaughani were destitute of any
vascular structure.
 In the anatomy of the aerial stem
are as followed :9

 Epidermis :
♣ It was the outermost single- layered
envelope covered by a thick layer of
cuticle. The epidermis of the aerial
shoot was interrupted by stomata.
10

♣ Each stomata have two guard cells,
therefore, the rhizome didn’t contain
any stomata. The rhizome possessed
unicellular rhizoids on it’s surface.
 Cortex :
☻The epidermis was followed by a
well organised and make broad zone
at cortex.
☻The cortex is differentiated into
two zones.
(a)The outer cortex(hypodermis)
(b)The inner cortex
11

(a) Outer cortex :
☻ The outer cortex consisted of 1-4
cells layer of compactly arranged
polygonal paranchy-matus cells
without any inter-cellular spaces.
♣ This region perhaps represents
hypodermis.
(b) Inner cortex :
☻ Inner to the hypodermis, there was
broad zone of inner cortex.
12

♣ The inner cortex was composed of
spherical parenchymatous cells with
large intercellular spaces which
maintained continuity with the outer
atmosphere through the stomata
present in the epidermis.
♣ This indicates that the inner cortex
was the chief photosynthetic region.
(c) Stele / Central cylinder :
☻ A protostele was present in the
central part of the axis as well as
rhizome.
13

♣ The xylem was surrounded by the
phloem.
♠ The xylem was composed of only
tracheids with annular or spiral
thickening.
♣ The phloem was
represented by 4 -
5 layers of thin
walled elongated
cells with oblique
end walls.
14

THE REPRODUCTIVE STRUCTURE
(THE SPORANGIA )
 Sporangia were borne singly on the
apices of some of the aerial branches.
 They were oval / slightly cylindri-cal
/ club / elongated shaped, with a
diameter slightly greater than that of
the subtending branch tip.
 The sporangia of R. major ;
Length: 12 mm , Breath: 1.4 mm
Spore : 65µ in diameter.
15

 The sporangia of R. gwynne
vaughani ; Length: 4 mm , Breath: 1.4
mm , Spore : 40µ in diameter.
 Their wall is
three layered;
(a) Outer epi-
Dermal.
(b)Middle three
cell rows thick
layer & (c) an
inner layer .
♣The outer layer heavily cutinized.
16

GAMETOPHYTE STAGE OF RHYNIA
 Within the same Rhynie chert beds
were some germinating spores which
show multicellular structure developing
at the end of germ tube. This was the
indication of the presence of
gametophyte in Rhynia.
 Merker (1961) opined that the
underground creeping parts of Rhynia is
the gametophyte but not the rhizome.
♣ As sex organs were not presents in
these organs, the gametophyte nature
because speculative only.
17

Pant (1960) regarded the small sized
R. gwynne vaughani to the
gametophytic part of R. major.
 Puri (1961) is of opinion of the
plants described as sporophyte may
be gametophytes.
18

REFERENCES
[1] Botany For Degree Students –
Pteridophyta
♣ Edition : 2006
♣ Authors : P.C Vashishta,
A.K. Sinha,
Dr. Anil kumar.
[2] Pteridophyta
♣ Edition : 2015
♣ Author : S. K. Singh.
[3] A text book of Botany
♣ Edition : Volume – 1
♣ Author : N. C. Kumar.
[4] WWW.Slideshsre.net
20

Ancient Plant Rhynia's Classification and Life Cycle

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Ancient Plant Rhynia's Classification and Life Cycle

Similar to Ancient Plant Rhynia's Classification and Life Cycle (20)

More from MaitriThakor

More from MaitriThakor (8)

Recently uploaded

Recently uploaded (20)

Ancient Plant Rhynia's Classification and Life Cycle