K.R. Sporne in 1962 classified the whole gymnosperms into three classes and they are again divided into orders.i. Cycadopsida
Orders: Pteridospermales, Bennettiales, Pentoxylales, Cycadales
- Primitive group, represented by small plants.
- Wood is manoxylic
- Male cones are large with compactly arranged microsporophylls
- Megasporophylls are loosely arranged does not form a cone.
- Seeds are radially symmetrical
- Examples: Cycas, Zamia
Orders: Cordaitales, Coniferales, Ginkoales and Taxales
- Includes larger dominant gymnosperms.
- Wood is pycnoxylic
- Sporophylls form cones.
- Seeds are bilaterally symmetrical.
- Examples: Pinus, Taxus, Ginko
- Includes advanced gymnosperms.
- Secondary xylem shows vessels.
- Ovules are orthrotropous with long tubular micropyle.
- Examples: Gnetum , Ephedra, Welwitschia