Care should be taken in collecting charae to secure, in the case of dioecious species, specimens of both forms, and also to get when possible the roots of those species on which the small granular starchy bodies or gemmae are found, as in C. fragifera.
A conspicuous example of a dioecious plant is the common aucuba, of which for years only the female plant was known in Britain.
The plant is usually dioecious, that is the sexes are on different plants, but can change from year to year!
In the case of unisexual flowers, whether monoecious, that is, with staminate and pistillate flowers on one and the same plant, such as many of our native trees - oak, beech, birch, alder, &c., or dioecious with staminate and pistillate flowers on different plants, as in willows and poplars, cross pollination only is possible.
Fortunei, the true Japanese plant is dioecious, and both sexes have received specific names, S. fragrans being simply the male of the true S. japonica.