The plumage of the male is of a uniform black colour, that of the female various shades of brown, while the bill of the male, especially during the breeding season, is of a bright gamboge yellow.
It is strained, deprived of its moisture, and receives an admixture of gamboge, cinnabar, acetous protoxide or some other coloring matter.
The hard transparent resins, such as the copals, dammars, mastic and sandarach, are principally used for varnishes and cement, while the softer odoriferous oleo-resins (frankincense, turpentine, copaiba) and gum-resins containing essential oils (ammoniacum, asafoetida, gamboge, myrrh, scammony) are more largely used for therapeutic purposes and incense.
In some Guttiferae, as Hebradendron cambogioides (the Ceylon gamboge plant), the anther opens by a lid separating from the apex (circumscissile dehiscence) .
Nux vomica, gamboge, caoutchouc, cardamoms, teak and other valuable woods and gums are among the natural products.