Classification of Plants : Bentham & Hooker

Topics included :- Systems involved, Bentham & Hooker flowchart, class and sub-class wise description,salient features, merits and demerits

1. Slide 1 CLASSIFICATION OF PLANTS [ BENTHAM AND HOOKER ] BY : S. DASH

2. Slide 1 CLASSIFICATION OF PLANTS Artificial Systems Phylogenetic systems (Based on morphological features) (Based on evolutionary and genetic relationship) Natural systems (Based on their natural affinities)

3. Slide 1 ARTIFICIAL SYSTEMS These systems of classification were based on one or few morphological characters. Theophrastus (370 – 285 BC) Otto Brunfels (1464-1534)  Andrea Caesalpino (1519-1603) Joseph Pitton de Tournefort (1656-1708) John Ray (1627-1705) Carolus Linnaeus (1707-1778)

4. Slide 1 NATURAL SYSTEMS In these systems the organisms are classified on the basis of their natural affinities (i.e. the basic similarities in the morphology) rather than on a single character for determining the affinities. A.L. de Jussieu (1748-1836) A.P. de Candolie (1778-1841) Bentham and Hooker’s Classification

5. Slide 1 PHYLOGENETIC SYSTEMS: Classification based on evolutionary features is known as phylogenetic system. Engler and Prantl (1884-1930) John Hutchinson (1884-1972)

6. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION

7. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION CLASS-I DICOTYLEDONAE Leaves show reticulate venation Flowers are tetramerous or pentamerous. Polypetalae Monochlamydeae Gamopetalae

8. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION SUB-CLASS-I POLYPETALAE Flowers with free petals come under polypetalae. The flowers are with distinct calyx and corolla. THALAMIFLORAE DISCIFLORAE CALCYFLORAE Flowers with conical or dome shaped thalamus Flowers having prominent disc shaped thalamus below ovary Flowers with cup shaped thalamus. Ovary is superior Ovary is superior Ovary is superior or inferior, sometimes half inferior 6 orders and 34 families 4 orders and 23 families 5 orders and 27 families

9. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION SUB-CLASS-II GAMOPETALAE Flowers with petals , which are either partially or completely fused to one another . The flowers are with distinct sepals and petals. INFERAE HETEROMERAE BICARPELLATE Flowers are epigynous Flowers having prominent disc shaped thalamus below ovary Flowers with cup shaped thalamus. Ovary is inferior Ovary is superior with more than two carpels Ovary is inferior, with two carpels only. 3 orders and 9 families 3 orders and 12 families 4 orders and 24 families

10. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION SUB-CLASS-III MONOCHLAMYDEAE Flowers with single whorl of perianth(sepals and petals not distinguished). Flowers are incomplete. Tepals are present in two whorls. Sometimes, both the whorls are absent. Includes 8 series and 36 families

11. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION CLASS-II GYMNOSPERMAE Naked ovules or seeds. Ovary is absent. Gnetaceae Cycadaceae Conifera

12. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION CLASS-III MONOCOTYLEDONAE Leaves show parallel venation. Flowers are trimerous Have fibrous root system Has 7 series and 34 families.

13. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION SALIENT FEATURES: 1. It is a classification of only the “seed plants” or phanerogams. 2. They described 97,205 species of seed plants belonging to 7,569 genera of202 families starting from Ranunculaceae up to Gramineae . 3. They classified all the seed plants into 3 groups or classes i.e. Dicotyledons (165 families), gymnosperms (3 families) and monocotyledons (34 families). 4. Monocotyledons were described after the dicotyledones . NAME : SHRITILEKHA DASH REG No. : 19PBI822 CLASS : M.Sc. BIOCHEMISTRY (Semester-2)

14. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION SALIENT FEATURES: 5. The dicotyledons were divided into 3 Divisions (Polypetalae, Gamopetalae and Monochlamydeae ) and 14 series. Each series again divided into cohorts (modern orders) and cohorts into orders (modern families). 6. The authors did not mention anything about the origin of the angiosperms. 7. Creation of the Disciflorae , a taxon not described by the earlier taxonomists. 8. Among the Monochlamydeae , major taxa, like the series, were divided on the basis of terrestrial and aquatic habits. NAME : SHRITILEKHA DASH REG No. : 19PBI822 CLASS : M.Sc. BIOCHEMISTRY (Semester-2)

15. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION MERITS : Bentham and Hooker’s classification is the most natural system, based on actual examination of specimens. 2. The description of plants is quite accurate and reliable. 3. The flora describes geographical distribution of species and genera. 4. The generic descriptions are complete, accurate and based on direct observations.

16. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION MERITS : 5. Larger genera have been divided into sub genera, each with specific number of species. 6. Although this system is natural, most of the aspects of this system show affinity to modern concepts of evolution.For example-dicots begin with the order Ranales which are now universally considered as to be the most primitive angiosperms. 7. Placing of monocots after the dicot is again a natural one and according to evolutionary trends. 8. As it is is easy to follow, it is used as a key for the identification of plants in Kew herbarium and several other herbaria in the world. 9. The placing of gamopetalae after polypetalae is justified since union of petalsis considered to be an advanced feature over the free condition.

17. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION DEMERITS : 1. Keeping gymnosperms in between dicots and monocots is anomalous. 2. Subclass monochlamydeae is quite artificial. 3. Placing of monochlamydeae after gamopetalae does not seem to be natural. 4. Some of the closely related species are placed distantly while distant species are placed close to each other.

18. Slide 1 BENTHAM AND HOOKER’S CLASSIFICATION DEMERITS : 5 . Certain families of monochlamydeae are closely related to families in polypetalae, e.g. Chenopodiaceae and Caryophyllaceae . 6. Advanced families, such as Orchiadaceae have been considered primitive in this system by placing them in the beginning. Placing of Orchidaceae in the beginning of monocotyledons is unnatural as it is one of the most advanced families of monocots. Similarly, Compositae (Asteraceae) has been placed near the beginning of gamopetalae which is quite unnatural. 7. Liliaceae and Amaryllidaceae were kept apart merely on the basis of characters of ovary though they are very closely related. 8. There were no phylogenetic considerations

19. Slide 1 REFERENCES: http://en.m.Wikipedia.org/wiki/ . http://www.braincart.com . College Botany(Volume-1)by Dr. B.P. Pandey. Plant taxonomy by O.P. Sharma.

20. Slide 1 THANK YOU!