ADVERTISEMENTS:
The following points highlight the three main lines of evolution in angiosperms.
Angiosperm: Evolution # 1.
The First Line:
I. It consists of Rhoeadales, Sarraceniales, Parietales, Malvales, Geraniales, Sapindales, Rhamnales and some Tubiferales. In this case the hypogynous condition remained unchanged.
ADVERTISEMENTS:
II. Labiatae is the most advanced family of this line. It is characterized by fusion of sepals, petals and carpels, and epipetalous condition and the number of floral parts are reduced to four or two.
III. Solanaceae is also characterized by fusion of sepals, petals and carpels, and epipetalous condition.
IV. Rhoeadales and Sarraceniales evolved parallely from Ranales.
ADVERTISEMENTS:
V. A definite relation persists between Parietales and Rhoeadales due to the development of the gynophore in Capparidaceae.
ADVERTISEMENTS:
VI. Malvales evolved through Bombacaceae and Malvales are related to Geraniales.
VII. Geraniales are related to Sapindales and Sapindales in turn are related to Rhamnales.
Angiosperm: Evolution # 2.
The Second Line:
I. It consists of Campanulales, Rosales, Myrtales, Umbellales and Rubiales. In this case, there is a change from hypogyny to epigyny through perigyny, which is seen clearly in Rosales.
II. Campanulales top this line with the presence of pappus, irregular flowers, and fusion of floral parts.
III. In Myrtales, there is a change of perigyny to epigyny due to the development of hypanthodium.
IV. In Umbellales, epigyny and syncarpy show advancement over Myrtales, and the former are related to Rubiales due to presence of characters such as suppression of calyx, epigyny, the presence of umbel-like inflorescence, etc.
Angiosperm: Evolution # 3.
The Third Line:
ADVERTISEMENTS:
It includes Liliales and Orchidales. It shows a few resemblances with monocotyledons (e.g. Alismataceae) and dicotyledons (e.g. Ranunculaceae).
I. Liliales differ from Ranales in the number of floral parts and fusion of carpels.
II. Iridaceae and Amaryllidaceae are more advanced than Liliales due to presence of epigynous condition.
III. Poaceae seems to have originated from Liliaceae. However the reduction in the number of stamens and carpels and also the loss of perianth parts clearly indicate that Poaceae is more advanced than Liliaceae.
ADVERTISEMENTS:
IV. Orchidaceae is characterized by insect-pollinated, irregular and showy flowers, and is thus the most advanced family of monocotyledons.
