While some of the species are bisexual, others are protandrous, self-fertilizing hermaphrodites.
These "psychically decadent" individuals appear to represent the entire male sex of a bisexual species, and become unnecessary owing to the grafting of hermaphroditism on the female sex.
Hydra is, moreover, bisexual, in contrast with what is known of hydroid colonies.
Both male and female gonoducts open through acornmon atrium to the exterior by tkis pore, but in three bisexual genera the male and female ducts are developed in separate individuals (Bilharzia, Didymozoon, Koellikeria).
A few species, however, are bisexual, e.g.
In bisexual or hermaphrodite flowers, that is, those in which both stamens and pistil are present, though self-pollination might seem the obvious course, this is often prevented or hindered by various arrangements which favour cross-pollination.
- Aplacophora with a distinct longitudinal ventral groove; bisexual with paired genital glands and no distinct liver.
A few species, as we have seen, are monoecious or dioecious, while many are polygamous (having unisexual as well as bisexual flowers as in many members of the tribes Andropogoneae, fig.
Spikelets bisexual, or male and bisexual, each male standing close to a bisexual.