Theory:

The term palaeobotany (paleobotany) is derived from two Greek words, palaeon which refers to "old", and botany which refers to the study of plants.
Palaeobotany is a discipline of study concerned with the recovery and identification of geologically old plant remnants.
It is a branch of paleontology that focuses on plant fossils, including algae, fungi, and related organisms, as well as mosses, ferns, and seed plants.
It is a study that helps us understand both the evolution of plant life and the ecology of ancient eras.
Fossils:
The prehistoric impressions that can range in age from hundreds to millions of years are known as fossils.
Any preserved portion of a long-dead plant is known as a plant fossil.
Most plant fossils are disarticulated parts of plants, as it is uncommon to find complete plants preserved.
 
499px-Betula_leopoldae_SRIC_SR02-22-19.jpg
Fossil of Betula leopoldae
Importance of fossils:
  • Fossils play a prominent role in the phylogeny and evolution of plants.
  • They serve as a historical bridge between the plants of the old and new era.
  • They are useful in the classification of plants.
  • Fossils of plants are used in the field of descriptive and comparative anatomy.
Kaspar Maria Von Sternberg:
He is prominently known as the "Father of Paleobotany". He was born in Europe (\(1761\)-\(1838\)), established the Bohemian National Museum in Prague. He is also known as the founder of Modern Paleobotany.
Birbal Sahani
450px-Bust_of_Birbal_Sahni_(Birla_Industrial_&_Technological_Museum).jpg
Birbal Sahani (1891–1949)
  
He is popularly known as the "Father of Indian Paleobotany".
He presented his observations in two areas of Paleobotany: 
  1. The anatomy and morphology of Paleozoic Ferns, and
  2. Fossil plants from the Indian Gondwana Formations.
Reference:
https://commons.wikimedia.org/wiki/File:Betula_leopoldae_SRIC_SR02-22-19.jpg
https://commons.wikimedia.org/wiki/File:Bust_of_Birbal_Sahni_(Birla_Industrial_%26_Technological_Museum).jpg