Q. Hutchinsons System of Classification?
John Hutchinson, a renowned British Botanist proposed 24 phyletic dicta or principles and based on these dicta he published a phylogenetic system in 2 volume book entitled "The Families of Flowering' Plants" (1926-1934). The volume I deals with Dicots while the Volume I1 having Monocots. The revised and detailed treatment of the system was published in 1959 and the most recent revised system appeared in 197.1.
Outline and Basis of Classification
As pointed out earlier, the system is mainly based on 24 phyletic dicta. Thus, it seems proper to give a brief account of these phyletic dicta.
1. Evolution is both upwards and downwards, the former tending towards preservation and the latter to their reduction and suppression (of characters). Examples of former are towards the sympetalous condition and epigyny and of latter towards the apetalous state of many flowers and unisexuality in flowering
Plants.
2. Evolution does hot necessarily involve all organs of the plant at the same time. One organ or set of organs may be advancing while another set may be stationary or retrograting.
3. Evolution has generally been consistent, and when a particular progression or retrogression has set in, it is persisted into the end of the phylum e.g., strong tendency to zygomorphy of the corolla coupled with the reduction in the number of stamens in Engler's hypogynous Metachlamydeae and the vast tendency to perigyny and epigyny in Archichlamydeae and Metachlamydeae as seen in the families Umbelliferae and Rubiaceae respectively.
4. In certain groups, trees and shrubs are probably more primitive than herbs e.g., Mirnosaceae and Caesalpiniaceae (trees and shrubs) as compared with the derived family Papilionaceae (Fabaceae) (often herbaceous).
5. Trees and shrubs are older than climbers in any one family or genus, the latter habit being acquired through particular environment.
6. Perennials are older than biennials, and from then annuals are derived e.g., there are only a few annuals in the primitive family Ranunculaceae while there are many more in the more advanced and natural family Cruciferae.
7. Aquatic flowering plants are derived from terrestrial ancestors, Epiphytes, saprophytes and parasites are more recent than plants of normal habit.
8. Dicotyledones with collateral vascular bundles arranged in a cylinder are more primitive in origin than Monocotyledones with scattered vascular bundles, although it does not necessarily follow than Monocots are directly derived from Dicots.
9. The spiral arrangement of leaves on the stem and of the floral leaves is more primitive than the opposite and whorled arrangement.
10. Simple leaves are usually more primitive than compound leaves.