The Phylogeny of Monocotyledons*

S ummary A large number of positive correlations exist among the following characters, which have been shown to be primitive for the Monocotyledons: Perianth present Perianth segments more than 5 Perianth homoiochlamydeous Perianth actinomorphic Perianth free Hermaphrodite Stamens 6 or more Carpels 3 or more Ovary inferior Ovules many Endosperm helobial or cellular Ripe pollen binucleate Ovules anatropous Parietal cell cut off from archesporial cell Embryo‐sac monosporic Pollen development simultaneous Leaves linear (uncertain) The antitheses of these characters (perianth absent, segments fewer than 6, hetero‐chlamydeous, etc.) represent advanced conditions. Four lists of taxa were used: Engler's families, Hutchinson's families, Engler's subfamilies and Hutchinson's tribes. In general the more taxa in the list the greater the proportion of significant results. Although Hutchinson's families are fewer in number than Engler's sub‐families, they give more significant results, suggesting that Hutchinson's system is the more ‘natural’. The ‘advancement indices’of the taxa comprising the two systems are compared. Hutchinson's scheme is found to be much more uniform than Engler's regarding the range of advancement within orders and families, further indicating that Hutchinson's is more ‘natural’. The trends of evolution in the Monocotyledons show a number of similarities with those found by Sporne in the Dicotyledons. For some characters evolution in the Monocotyledons appears to have taken a course similar to the more recent of the two Dicotyledonous trends. It is suggested that this indicates the derivation of the Monocotyledons from the Dicotyledons. The taxa have been arranged according to their relative advancement (Tables 10–13). This is a contribution towards our understanding of the phylogeny of the Monocotyledons. The interconnections of the taxa, backwards through time, can however be elucidated only by increased knowledge of the fossil record.