Bentham and Hooker divided the Angiospermae into two classes: Dicotyledons and Monocotyledons and in between this they have placed Gymnosperms. Dicotyledons is again divided into three subclasses. They are Polypetalae,
Gamopetale and Monochlamydeae. These sub classes are again divided into series. Series is again divided into order or cohort and order into family.
1. Polypetalae (corolla of distinct petals)
- Series I Thalamiflorae: petals and stamens hypogynous. It includes the following 6 cohorts (orders): Ranales, Parietales, Polygalineae, Caryophyllineae, Guttiferales, Malvales
- Series II Disciflorae: petals and stamens hypogynous and a nectariferous disc. Surrounds the base of the ovary. It contains the following cohorts: Geraniales, Olacales, Celastrales, Sapindales
- Series III Calyciflorae: petals and stamens perigynous or sometimes epigynous. It includes 5 cohorts: Rosales, Myrtales , Passiflorales, Ficoidales, Umbellales
- Series I Inferae: ovary inferior. It includes 3 cohorts: Rubiales, Asterales , Campanales
- Series II Heteromerae: ovary superior, stamens as many or twice as many as corolla, Lobes, carpels more than two. The 3 cohorts are Ericales, Primulales, Ebenales
- Series III Bicarpellatae: ovary superior, stamens as many as the corolla lobes or fewer, carpels usually two. It has the following 4 cohorts: Gentianales, Polemoniales , Personales, Lamiales
- Series I Curvembryeae : embryo curved round the endosperm, ovule usually one.
- Series II Multiovulatae aquaticae: aquatics with numerous ovules.
- Series III Multiovulatae terrestris : terrestrial plants with numerous ovules.
- Series IV Microembryeae: embryo very small in copious endosperm.
- Series V Daphnales: ovary usually with one carpel and single ovule.
- SeriesVI Achlamydosporeae: ovary usually inferior, unilocular and one to three ovules.
- Series VII Unisexuales: flowers unisexual.It includes 9 Orders: Euphorbiaceae
- Series Vlll Ordines anomali: uncertain relationship.
- i) Cycadales - Ex: Cycas
- ii) Coniferales - Ex: Pinus
- iii) Gnetales - Ex: Gnetum
- Series I Microspermae :ovary inferior, seeds very small. It includes 3 Orders:
- Series II Epigynae : ovary usually inferior, seeds large.
- Series III Coronarieae :perianth petaloid, ovary superior.
- Series IV Calycinae : perianth sepaloid, ovary superior. It includes 3 Orders: Juncaeeae
- Series V Nudiflorae : perianth mostly lacking, ovary superior.
- Series VI Apocarpeae : carpels free.
- Series VII Glumaceae : perianth small, scale-like or chaff). It includes 5 orders: Eriocaulaceae, Cyperaceae, Poaceae etc