The following points will highlight the two major causes of fossil gymnosperms. The classes are: (1) Cycadopsida and (2) Coniferopsida. Fossil Gymnosperms: Class # 1. Cycadopsida: Order-Pteridospermales (Cycadofilicales): The Ptieridospermae or the Cycadofilicales are fossilized plants that first appeared in the upper Devonian. They were very common throughout the Carboniferous and extended upto Permian strata. After the Permian they began [...]
The below mentioned article provides an overview on Gnetopsida. After reading this article you will learn about: 1. Introduction to Gnetopsida 2. Systematic Position of Genus 3. Habit of Genus 4. Growth 5. Anatomy of the Stem 6. Reproduction 7. Economic Importance. Introduction to Gnetopsida: Class-Gnetopsida; Order-Gnetales; Genus Ephedra: The Gnetales are a small group of plants, comprising of three [...]
Gymnosperm is a large class that includes a number of fossils and living forms (Fig. 9.1). Various attempts have been made by different works to classify the gymnosperms. The classification as proposed by C.J. Chamberlain (1935) is as follows: Cycadales: (i) Cycadales include 11 living genera and more than 100 species of cycads. (ii) Cycads resembles with the pteridophytes. (iii) [...]