The flowers of Halophila are submerged and apetalous.
It has narrow, shortstalked leaves and inconspicuous, apetalous, unisexual flowers borne in short spikes.
The genus Myrica is the type of a small, but widely distributed order, Myricaceae, which is placed among the apetalous families of Dicotyledons, and is perhaps most nearly allied to the willow family.
The starting-point of the class, however, and the position within it of apetalous families with frequently unisexual flowers, have provoked much discussion.
In the Euphorbiaceae we have an excellent example of the gradual suppression of parts, where from an apetalous, trimerous, staminal flower we pass to one where one of the stamens is suppressed, and then to forms where two of them are wanting.