Paleobotany includes the study of plant life of geologic past. It tells about preserved vestiges of the plant life of the past. It is defined as the branch of botany which deals with the study of such plants which were living in the past but are vestigial now.
Fossils: Fossils of fossil remains of plants that lived long ago. Fossils are impressions or cast of the organelles living sometime back but now are extinct on rocks occurring in the earth and requiring to be dug out. Poleontology is the study of fossils. Normally the plant dies and it soon starts generation. This generation continues till the entire body is broken into single chemical compound. Sometimes in certain circumstances degeneration of plant body stops and part of body remains in visible form. These remains are known as fossils. Plant fossils are present in rocks composed of sediments deposited in water. These strarified rocks are super imposed upon one another. These rocks are built of sediment, that accumulate in bottom of seas, lakes, swamps, flooded valleys. Rock formation is co related with geological approach in the subject paleobotany. In fact fossils are the makers of geologic tume.
Importance of Paleobotany:
(1) Fossil plants show light on phylogeny and evolution of plants. Extinct plants tell us some stages by which existing group has passed during course of their development.
(2) Fossil plants give historical approach to plant kingdom.
(3) Fossils are helpful in classification of plants.
(4) Fossil plants can be used in the field of descriptive and comparative avatomy.
Fossilization:
First of all wind or stem borne plants comes into quit water and becomes satirated. Now it begins to sink. The entire plant or some part of it lie in parallel to horizontal position. In presence of mud or savd plant woll sterile with sand. Much sediment will cause rapid accumulation and the plants separated from one another. Thus rocks are formed in between which plant parts (mainly stem leaves) remain present. As the sediments increases in thickness. If the plant part is cylindrical and made up of hard tissues the weight of sediment will produce a lens shaped object. Thus the rocks have the compression of impression of plant. Thus rock having compression when split open on one surface usually bears the umpressed outer part.
Types of Fossil plants: They are as under:
(1) Petrifications or mineralized plants:
In this type of plant fossil cell of plant tissue is retained by means of some mineral like CaCo3, silica etc that has infiltered the tissue. In this type of fossil sometimes the material of original plant may be preserved e.g.: coal balls, silicified wood.
(2) Cast on incrusation:
In this type of plant fossil the form of plant is preserved as a cast. The cast result from the filling of a cavity formed by decay of tissues of plant part. Here the internal structures are destroyed and carbonaceous substances of the plant has totally gone e.g.: Stem leaf seers, larger seeds.
(3) Compressions:
In this type of plant fossil the external form of plant is modified and leaves impressions on the sediment which over lie it.
(4) Compaction or Mummified plants:
In this type of plant fossil, the plants or their partes get compressed by vertical pressure against one another. Mostly plant rudiments found in Pea and Coal as compactions. Coal or Coal balls are important source of plant fossils. Coals are irregular or subspherical mass of calcium or magenesium carbonates.
(5) Impressions:
In this type of plant fossil the roots, stems, leaves, fruits and seeds are preserved as impressions in such a fashion that they seem to be the actual dried speciments laid on the stone.
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