Bentham and Hooker System of Classification

• George Bentham (1800-1884) and (1817-1911) were British Botanists from the Royal Botanic Gardens, Kew, England. • He proposed a natural system of classification, in which all natural characters of plants both vegetative and reproductive are considered. • Bentham and Hooker's published his taxonomic work in their book ‘Genera plantarum’ in three volumes between 1862 and 1883. • The Genera plantarum includes about 97,205 species belonging to 202 families and 7,569 genera. • This system of classification has been used for seed plants. • They divided plants into three classes, namely, Dicotyledonae, Gymnospermae and Monocotyledonae. • The brief classification of this system can be mentioned as follows: Class I Dicotyledonae Seeds of dicotyledonous plants contain two cotyledons. Leaves show reticulate venation. Flowers are tetramerous or pentamerous. It consists of three sub-classes, Polypetalae, Gamopetalae and Monochlamydeae.

Sub-class I- Polypetalae - Plants having flowers with free petals and separable calyx and corolla. This subclass comprises three series - Thalamiflorae, Disciflorae and Calyciflorae.

Series (i)Thalamiflorae- Plants having flowers with dome or conical thalamus and superior ovary. Consists of 6 orders and 34 families.

Series (ii) Disciflorae- Plant having flowers with prominent disc shaped thalamus below the ovary (superior). Divided into 4 orders and 23 families.

Series (iii) Calyciflorae - Plants having flowers with cup shaped thalamus. Ovary is superior or inferior or sometimes half inferior. Consists of 5 orders and 27 families.

Sub-class 2. Gamopetalae - Plants having flowers with partially or completely fused petals. Sepals and petals are distinct. Divided into three series, namely inferae, heteromerae and bicarpellatae.

Series (i) Inferae- Plants with epigynous flowers and inferior ovary. Consists of 3 orders and 9 families.

Series (ii) Heteromerae- Plants with more than two carpel, hypogynous flower and superior ovary. Consists of 3 orders and 12 families.

Series (iii) Bicarpellatae- Plants with only two carpel, hypogynous flower and superior ovary. Consists of 4 orders and 24 families.

Sub-class 3. Monochlamydeae- Plants having flowers with single whorl of perianth, incomplete flowers and two whorls of tepals. Sometimes both the whorls are absent. Consists of 8 series and 36 families. The 8 series of this subclass are: Curvembryeae Multiovulateae aquaticeqa Multiovulateae terrestres Microembryeae Daphneles Achlamydosporeae Unisexuales Ordines anomali

Class II Gymnospermae- Plants with naked ovules or seeds. Consists of three families namely, Gnetaceae, Coniferae and Cycadaceae.

Class III Monocotyledonae- These plants contain only one cotyledon. Leaves show parallel venation. Flowers are trimerous having three members in various floral whorls. Fibrous root system present. Consists of 7 series and 34 families. The 7 series of this class are: Microspermae Epigynae Coronarieae Calyeinae Nudiflorae Apocarpeae Glumaceae

• Merits 1. It is the natural system, based on actual specimen or preserved herbarium of plants. 2. The description of plants is quite accurate and definitive. 3. It is easy to follow and can be used as a key for the identification of plants herbaria. 4. This system shows harmony with modern concepts of evolution. 5. Larger genera have been divided into sub genera with specific number of species. 6. Dicots begin with the order Ranales most primitive angiosperms. 7. Placing of monocots after the dicot is justified. 8. The placing of series disciflorae in between thalamiflorae and calyciflorae is quite natural. 9. The placing of gamopetalae after polypetalae is justified 10. The placement of Monocotyledonae after Dicotyledonae is in accordance with the evolutionary trends.

• Demerits 1. Gymnospermae was wrongly placed between Dicotyledonae and Monocotyledonae . 2. Several important floral characters have been omitted. 3. Some closely related families have been separated and placed under different groups. 4. Some unrelated families have been placed together. 5. Placing of monochlamydeae after gamopetalae is not justified 6. and were kept apart. 7. Placing of Orchdaceae in beginning of monocots is unnatural. 8. Phylogenetic concept has not been integerated.