The document discusses several theories about the origin and evolution of angiosperms. It describes theories that proposed various plant groups as possible ancestors of angiosperms including isoetes, conifers, gnetales, bennettitales, caytoniales, and pentoxylales. However, many of these theories were later contradicted or disagreed with based on evidence from vascular anatomy, seed structure, and other characteristics. The document also outlines primitive and advanced characteristics seen in different angiosperm groups, showing their diverse evolutionary lines.

1. ORIGIN AND EVOLUTION OF ANGIOSPERMS.
PRESENTEDBY
SHAIKHSHABNOOR
MSC 1
1203.

2. ORIGIN OF ANGIOSPERMS.
 SuddenAppearance in Cretaceous age.
 Charles Darwin describedit as “abominable mystery” due to poor records.
 Many considerable differences of opinionamong botanists.
 About their age (late Jurassicor early cretaceous).
 Place of origin(Articor pacific basin).
 Possible ancestors (various theories).

3. ISOETES MONOCOTYLEDON THEORY
 Put forthby Campbell in 1928.
 Herbaceous angiosperms are primitive, inheritedfromfilicineanancestor.
 Isoetales, Lycopodales, ferns possesscharacteristics
same withmonocotyledons.
 Isoetesgrows in aquatic or amphibious environment indicating relationshipwith
monocotyledons.
 Similarity in structure and positionof embryo.
 No intervention of seedsdisappoints this theory.

4. CONIFER-AMENTIFERAE THEORY
 Put forth by Engler (1882) andlater Rendle (1904).
 Found similarity of angiosperms withConifers.
 ConsideredAmentiferous groupas primitive
angiosperms.
 Coverednature of seeds in araucaria.
 Naked inflorescence of amentifers compared
to conifers.
 Fertilizationin araucaria, pollenare deposited
on the scale andonly pollentube enters the micropyle.
 According to modernclassificationamentiferae is regardedas advancedplants.

5. GNETALES-ANGIOSPERMTHEORY
 Wettstein (1901) emphasisedrelationshipbetween Gnetales and angiosperms.
 Supportedby Markgraf (1930)and Fagerlind (1947) who proposed that gnetales and
angiospermevolvedfromsingleancestor.
 Presence of two cotyledons.
 Vessels in the secondary wood.
 Stamens apparently similar to angiosperms.
 Bitegmicovules of gnetales.
 Evidence fromvascular anatomy stronglyrefuse
relationshipbetweengnetales and angiosperms.

6. BENNETTITALEAN THEORY
 Put forthby Saporta and Marion (1885) and Arber and Parkin (1907).
 Benettitales as possible ancestor of angiosperms for
similarities betweenthe strobili of
Cycadeoideaand Magnolia.
 Strobili and flower both are bisexual.
 Elongatedcentral axis having bracts,
micro and megasporophylls.
 Carpel bear single ovule.
 Contradiction with stemanatomy disappoints this theory.

7. CAYTONIALEAN THEORY
 Proposed by H. HamshawThomas (1925).
 Caytoniales (jurrasicera fossil) as possible ancestor of angiosperm.
 Semi enclosed ovules (pouches) of caytonia
comparedto carpel/fruits of angiosperm.
 Reticulatevenation.
 Anthers of caytonanthus resembles
with that of angiosperms.
 Unitegmicovules of caytonales disappoints the comparisonand refusethis theory.

8. PENTOXYLALEAN THEORY
 Meeuse(1961) proposed pentoxylales (fossil) as probable ancestor of angiosperms.
 Affinities of pentoxylales to pandanus.
 Plants are erect and dioecious.
 Stemslender and cylindrical.
 Stembears a terminal tufts of
strap- shapedleaves arranged spirally;
 Seeds enclosed in sarcotesta.
 Later, Pant and Kidwai (1971) statedthat the above similarity appears as a result of
parallel evolution

9. EVOLUTION OF ANGIOSPERMS
 Different groups of angiosperms revealsdifferent linesof evolution.
 Primitive to highlyadvanced characters.
 Primitive characters:-
 Simple persistant leaves.
 Stomatawithsubsidiarycells.
 Floral partsfree.
 Solitary flowers.
 Actinomorphic and hypogynous conditiom.
 Carpels withlargeorthotropous ovules.
 Large endospermicseedwithsmallembryo.
 Stamens with4 microsporangia andpollengrains
with1 aperture.

10.  Advanced characters:-
 Cyclicor whorledfloral parts.
 Compound leaves withtendrils and spines.
 Gamopetalous, epipetalous, syncarpous, condition.
 Special Infloresence.
 Zygomorphicwith epigynous condition.
 Carpels few withanatropous ovule.
 Non endospermicseeds.
 Reduce no. of v.b 2º thickening.
 Stomata without guard cells.
 Extreme morphological, anatomical and physiological adaptation.

11. REFERENCES
 Textbook of botany- taxonomy of angiosperms.
 http://www.biologydiscussion.com/angiosperms/theories-about-the-
ancestors-of-angiosperms/