Angiosperm phylogeny group (APG) classification

APG (Angiosperm Phylogeny Group) classification is the most recent system for flowering plants, based on phylogenetic DATA rather than morphology alone, published across four successive versions - APG I (1998), APG II (2003), APG III (2009) and APG IV (2016) - each version supplanting the one before. It recognises MONOPHYLETIC groups using evidence from gross morphology, anatomy, embryology, palynology, karyology, phytochemistry, and - most heavily - molecular data: two chloroplast genes (atpB and rbcL) and one nuclear gene (18S ribosomal DNA). APG IV (2016) recognises 64 orders and 416 families, of which 259 families are represented in India. It is currently the accepted system worldwide among leading taxonomic institutions and practising taxonomists, though it has not yet percolated into the Indian botanical curriculum.

APG IV splits angiosperms into three clades. Early angiosperms (the ANA-grade + magnoliids + Chloranthales: Amborellales, Nymphaeales, Austrobaileyales; 8 orders, 26 families) always have two cotyledons, ethereal oils, simple net-veined leaves, floral whorls with many parts, a usually spirally-arranged perianth (or parts in threes), broad-filamented stamens, tetrasporangiate anthers, monosulcate pollen, rare nectaries, usually free carpels and a very small embryo. Monocots (11 orders, 77 families - basal monocots + lilioids + commelinids) have a single cotyledon, a short-lived primary root, a single adaxial prophyll, rarely ethereal oils, are mostly herbaceous with no vascular cambium, have scattered vascular bundles, parallel-veined leaves, floral parts usually in threes, tepals, monosulcate pollen, hollow styles and successive microsporogenesis. Eudicots (45 orders, 313 families - early diverging eudicots + super rosids + super asterids) always have two cotyledons, trilacunar nodes with three leaf traces, anomocytic stomata, rarely ethereal oils, simple or compound usually net-veined leaves, flower parts mostly in twos/fours/fives, simultaneous microsporogenesis, a solid style and tricolpate pollen. …