In this article we will discuss about the merits and demerits of Throne’s system.
Merits of Thorne’s System:
1. The woody Annonales which are now universally accepted as the most primitive living Angiosperms are the starting point of his system and constitute the base of the phylogenetic shrub of Angiosperms. The Berberidaceae and the Nymphaeales, though more advanced than the Annonales are all considered to be closely related.
2. The arrangement of Dicotyledoneae is much more phylogenetic because it has brought the closely related taxa nearer to each other in their placement. The orders Ericales, Ebenales, and the Primulales, though more advanced are considered to be related to the Theales and all kept under superorder Theiflorae. The order Theales contains the closely related families Dilleniaceae and Sarraceniaceae.
3. The Amentiferae which has long been considered as an assemblage of unrelated families has been abolished and its families distributed in different orders near their relatives.
4. Inclusion of the orders Malvales, Urticales, Rhamnales, Euphorbiales, Solanales and the Campanulales under the superorder Malviflorae. Cornales and Dipsacales are placed in one superorder Corniflorae.
5. The orders Pittosporales and Proteales though more advanced than the Rosales are all considered to be related and kept under the superorder Rosiflorae.
6. The family Stylidiaceae is kept under the suborder Saxifragineae under the order Rosales.
7. The order Dipsacales are considered as related to the Cornales and both these orders are kept under the superorder Corniflorae.
8. Among the subclass Monocotyledonae, the order Liliales are considered to be the starting point, the highest evolved family of this order being the Orchidaceae. The Alismatales are considered to be more specialized than the Liliales.
9. The Typhales are considered as related to but more advanced than the Araceae. On the contrary, the traditional relatives of Typhaceae, the Pandanales are included under the superorder Areciflorae along with the orders Arecales and Cyclanthales.
10. Among the Commelinales, the Bromeliaceae forms the starting point while the Poaceae is the most highly evolved family of the order.
Demerits of Thorne’s System:
1. It is not of much practical value in identification.
2. Thorne’s of the view that angiosperms have originated from some Pteridospermous members is also not accepted by several taxonomists.
In the history of plant classification there is no final word. The systems which seem adequate today may become out mudded in light of further researches.