THE OVULE AS AN INDICATOR OF EVOLUTIONARY STATUS IN ANGIOSPERMS

Abstract

S ummary The crassinucellate ovule has long been regarded as more primitive among angiosperms than the tenuinucellate. Support for this view is provided by thirteen highly significant statistical correlations between the crassinucellate condition and other dicotyledon characters, both floral and vegetative. This character is therefore included among a total of twenty‐two characters believed to be of use in assessing evolutionary status. The ‘advancement indices’ of dicotyledon families are re‐calculated, using the most recently available facts. While the most primitive families are among the Magnoliales, there are also some very primitive ones among the Myrtiflorae, Violates, Geraniales, Rosales, Guttiferales and Fagales. It is concluded that the ancestral type of ovule in angiosperms was crassinucellate with three envelopes (two integuments and an aril) each of which received a vascular supply.