Plant Taxonomy Prof. (Dr.) Punam Jeswal Head M.Sc semester ll Department of Botany

Dahlgren's System of Classification of Angiospermic Plant

R. M. T. Dahlgren's System -

Rolf M. T. Dahlgren, Professor at the Botanical Museum, University of Copenhagen, Denmark, proposed a system of classification (1980, 1981 and 1983) drawing, data from several disciplines of botany including comparative morphology, anatomy, embryology and chemistry.

Salient Features -

 He considered that none of the extant group of flowering plants is ancestor to any other present day group.  The Magnoliaceae - Ranunculaceae stock is not ancestor to other flowering plants but has simply retained the large number of primitive features.  Angiosperms have monophyletic origin from particular line of Gymnosperms.  Magnoliiflorae have been considered as most primitive among dicots and Alismatiflorae have been regarded as most primitive among monocots.  Dicots (Magnoliidea) have been divided into 25 superclasses and 85 orders while Monocots (Liliidae) have been divided into 8 superorders and 25 orders.

Critical Comments -

Merits - 1. In constructing this classification, an attempt has been made to consider as much informations as possible. 2. The system is phylogenetic and dicots have been considered more primitive than monocots. SYSTEMS OF CLASSIFICATION

Magnoliopsida 2 Classes

Magnoliidae Liliidae (Dicotyledoneae) (Monocotyledoneae)

1. Magnoliiflorae 8. Violiflorae 12. Podostemiflorae 21. Solaniflorae 1. Alismatiflorae 1. Annonales 23. Violales 49. Podostemales 70. Solanales 1. Hydrocharitales 2. Aristolochiales 24. 13. Proteiflorae 71. Boraginales 2. 3. Rafflesiales 25. Salicales 50. 22. Corniflorae 3. Zosterales 4. Magnoliales 26. Tamaricales 14. Myriflorae 72. Fouquieriales 2. Triuridiflorae 5. Lactoridales 27. Capparales 51. Haloragales 73. 4. Triuridales 6. Chloranthales 28. Salvadorales 52. Rhizophorales 74. Eucommiales 3. Ariflorae 7. Illiciales 9. Theiflorae 53. Myrtales 75. Sarraceniales 5. Arales 8. Laurales 29. Dilleniales 54. Chrysobalanales 76. 4. Lilliflorae 9. Nelumbonales 30. Paeoniales 15. Fabiflorae 77. Dipsacales 6. 2. Nymphaeiflorae 31. Theales 55. Fabales 23. Losaliflorae 7. 10. Piperales 10. Primuliflorae 16. Rutiflorae 78. Loasales 8. 11. Nymphaeales 32. Primulales 56. Sapindales 24. Gentianiflorae 9. Burmanniales 3. Ranunculiflorae 11. Rosiflorae 57. Rutales 79. Goodeniales 10. 12. 33 Ebenales 58. Polygalales 80. Oleales 5. Brobelliflorae 13. Papaverales 34. Trochodendrales 59. Geraniales 81. Gentianales 11. Velloziales 4. Caryophylliflorae 35. Cercidiphyllales 60. Balsaminales 25. Lamiiflorae 12. 14. 36. Hamamelidales 61. Tropaeolales 82. Scrophulariales 13. Haemodorales 5. Polygoniflorae 37. Geissolomomatales 17. Santaliflorae 83. Hippuridales 14. Philydrales 15. Polygonales 38. Balanopales 62. Celastrles 84. Lamiales 15. Pontederiales 6. Plumbaginiflorae 39. Fagales 63 Vitales 85. Hydrostachyales 16. Typhales 16. Plumbaginales 40. Juglandales 64. Santalales 6. Zingiberiflorae 7. Malviflorae 41. Myricales 18. Balanophoriflorae 17. 17. 42. Casuarinales 65. Balanophorales 7. Commeliniflorae 18. Urticales 43. Buxales 19. Araliflorae 18. 19. Euphorbiales 44. Cunoniales 66. Pittospermales 19. Hydatellales 20. Thymeleales 45. 67. Araliales 20. Juncales 21. Rhamnales 46. Droserales 20. Asteriflorae 21. Cyperales 22. Elaeagnales 47. 68. Campanulales 22. Poales 48. Rosales 69. Asterales 8. Areciflorae 23. 24. Cyclanthales 25. Fig. Outline of Dahlgren's System of Classification

Demerits -

1. The divisions of angiosperms () into two subclasses, Magnoliidea and Liliidae seem to be arbitrary.

2. The author considers angiosperms to be monophyletic in origin form particular line of Gymnosperms, but several attributes like secondary endosperm, 8- nucleated embryosac, companion cells in phloem etc. would hardly have evolved independently in different gymnospermous groups.

3. The variability of characters among Magnoliidea (Dicots) indicate their polyphyletic origin , however, Liliidae stand out as a possibly monophyletic group by virtue of their single cotyledon and characteristic triangular protein bodies in the sieve tube plastids.

4. This system is closely similar to the Takhtajan original plan with some additional data.

5. Prof. Corner (1981) criticized this system and holds that the classification includes unnatural orders and superorders. Regarding the nomenclatures of various groups adopted by Dahlgren, he suggested the name Pseudon for a conjectural taxon.