Classification of Gymnosperms

i) K.R. Sporne in 1962 classified the whole gymnosperms into three classes and they are again divided into orders.

1. 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

2. Coniferopsida
Orders: Cordaitales, Coniferales, Ginkoales and Taxales

• Includes larger dominant gymnosperms.
• Wood is pycnoxylic
• Sporophylls form cones.
• Seeds are bilaterally symmetrical.
• Examples: Pinus, Taxus, Ginko

3. Gnetopsida
Orders: Gnetales

• Includes advanced gymnosperms.
• Secondary xylem shows vessels.
• Ovules are orthrotropous with long tubular micropyle.
• Examples: Gnetum , Ephedra, Welwitschia

ii) Bierhorst (1971) Gymnosperm Classification