List microsporogenesis and megasporogenesis pdf six eminent botanists who contributed to the phylogenetic system of plant classification:- 1. Adolf Engler, Professor of Botany, University of Berlin.
20 volumes, including all the known genera of plants from algae to the phanerogams along with key to identify the plants. 2 volumes in 1954 and 1964. The system of Engler has been widely used in the American and Europian continents. The Angiospermae is divided into two Classes — Monocotyledonae and Dicotyledonae. The Class Monocotyledonae is divided directly into 11 Orders.
On the other hand, the Class Dicotyledonae is divided into two Subclasses — Archichlamydeae i. The Archichlamydeae is further divided into 33 Orders, and Metachlamydeae into 11 Orders. The Orders are divided into Suborders, Families, Genera and finally into Species. In this system, the Plant Kingdom contains 309 families. The Class Monocotyledonae starts with the family Typhaceae and ends in Orchidaceae, while the class Dicotyledonae starts with the family Casuarinaceae and ends in Compositae. In this system, Engler considered that in Embryophyta Siphonogama the flower without perianth is the primitive one. Thus, plants like Oak, Willow etc.
The term Natural order has been replaced by Family. The term Series or Cohort has been replaced by Order. The entire Plant Kingdom was broadly treated with excellent illustrations, and phylogenetic arrangement of many groups of plants was made. Juncaceae, Amaryllidaceae and Iridaceae are placed judiciously nearer to Liliaceae. The placement of Amentiferae and Centrospermae almost at the beginning of Dicotyledones, even before Ranales, are not justified. Metachlamydeae increased the distance of closely related orders.
The placing of the order Helobiae between the advanced orders Pandanales and Glumiflorae is questionable. Araceae was placed much earlier than Liliaceae, from which it has been derived. Fossil evidences gave little support to this system. He developed and proposed his system based on Bentham and Hooker and also on Bessey. He made several revisions in different years. 2nd September 1972 and the 3rd i. Evolution takes place in both upward and downward direction.