There are even dimorphic forms among the Syllids where the sexes are, as in many Polychaets, separate.
Darwin's works on dimorphic flowers and the fertilization of orchids gave powerful support to this statement.
Thus there are a few 3 Ferns which climb, others are .8 water plants, while many, especially those which live as epiphytes, are more or less xerophytic. Some of the epiphytic forms (Polypodium quercifolium, Platycerium) have strongly dimorphic leaves, the sterile leaves serving in some cases to catch falling debris, and thus to provide the plant with soil.
Such plants are called dimorphic. Other plants are timorphic, as species of Lythrum, and proper fertilization is only effected by combination of parts of equal length.