Plant Taxonomy Prof. (Dr.) Punam Jeswal Head M.Sc semester ll Department of Botany Thorne's System of Classification of Angiospermic Plant Robert F. Thorne (1983) published a pure phylogenetic system of classification based on the characters adopted from the comparative morphology, paleontology, ultrastructure, cytology, pollen and seed morphology, phytogeography and host-parasite interactions. Salient Features - The author considered relationships or similarities more important than differences and claimed his taxa to be more inclusive than those with more disintegrative tendencies. According to him the divergence of his system from other systems are startling realignments that are new or at least different from standard treatments. He considered angiosperms as well as two classes, Magnoliopsida and Liliopsida, as monophyletic taxa. The system includes data from all available evidences like other contemporary authors. Thorne divided class Annonopsida (Angiospermae) into 2 subclasses, 28 super- orders, 54 orders, 73 suborders, 350 families, 12,255 genera and 2,25, 490 species. Angiospermae (Annonopsida) 2 subclasses Dicotyledonae Monocotyledonae (Annonidae) (Liliidae) 1. Annoniflorae 22. Rhamnales 1. Liliiflorae 1. Annonoles 23. Euphorbiales 1. Liliales 2. Nelumbonales 10. Rutiflorae 2. Triuridiflorae 3. Paeoniales 24. Rutales 2. Triuridales 4. Berberidales 11. Proteiflorae 3. Alismatiflorae 2. Nymphaeiflorae 25. Proteales 3. Alismatales 5. Nymphaeales 12. Hamamelidiflorae 4. Zosterales 3. Rafflesiflorae 26. Hamamelidales 5. Najadales 6. Rafflesiales 27. Casuarinales 4. Ariflorae 4. Theiflorae 28. Fagales 6. Arales 7. Theales 13. Rosiflorae 5. Cyclanthiflorae 8. Ericales 29. Rosales 7. Cyclanthales 9. Fouquieriales 30. Pittosporales 6. Pandaniflorae 10. Ebenales 14. Loasiflorae 8. Pandanales 11. Primulales 31. Loasales 7. Areciflorae 12. Polygonales 15. Myrtiflorae 9. Arecales 5. Chenopodiiflorae 32. Myrtales 8. Typhiflorae 13. Chenopodiales 16. Gentianiflorae 10. Typhales 14. Geraniales 33. Oleales 9. Commeliniflorae 6. Celastriflorae 34. Gentianales 11. Commelinales 15. Celastrales 35. Bignoniales 12. Zingiberales 7. Santaliflorae 36. Lamiales 16. Santalales 17. Solaniflorae 17. Balanophorales 37. Solanales 8. Violiflorae 38. Companulales 18. Violales 18. Corniflorae 19. Capparales 39. Cornales 9. Malviflorae 40. Araliales 20. Malvales 41. Dipsacales 21. Urticales 19. Asteriflorae 42. Asterales Fig :- Outline of Thorne's System of Classification Critical Comments Merits - 1. Annonales are universally accepted as the most primitive living angiosperms, and they form the starting point of this system. 2. The divisions of dicots into Archichlamydeae and Metachlamydeae are abolished as against the traditional system. 3. Largely the similarities are given greater emphasis than differences and related taxa are placed closer. 4. After abolishing Amentiferae (a group of unrelated families), their families have been distributed in different orders. 5. Inclusion of orders Malvales, Urticales, Rhamnales and Euphorbiales under one superorder Malviflorae is appreciable feature of this system. 6. Classification of the related orders Cornales and Dipsacales under one superorder Corniflorae is also a commendable merit of the system. Demerits - 1. The system has no practical value for identification of plants. 2. The system includes box in box categories, which makes it confusing and complex. 3. Several taxonomists do not accept Pteridospermous origin of angiosperms in early Cretaceous times, as the author advocated. 4. Against the inclusiveness of the taxa over contemporary systems, as claimed by the author himself, the main theme however remained the same as proposed by Takhtajan and Cronquist. 5. Commenting upon the system, Merxmuller (1977) stated, This reminds me a little of the old Englerian times in which so many infra-specific categories like proles, subvariety, subforma and so have been in vogue. We should deliberate whether this superordinal inflation is not another fruitless trial of expressing quite doubtful phylogenetical contexts by box-in-box schemes. He further narrated that At all events this inflated classification is a perfect means for confusing non-taxonomists by a fashionable application of non-existing nomenclatural rules to these higher categories. .