Galium is found nearly throughout the world, mainly in warm to cold temperate regions and tropical mountains. It is sometimes overlooked as Rubiaceae due to its whorled leaves that apparently do not have interpetiolar stipules, but apparently the leaves are opposite and the stipules are foliaceous and morphologically similar to the actual leaves. The foliaceous stipules are sometimes also divided, so the leaves are ternate to 8-verticillate. The inflorescences are axillary and sometimes also or mainly terminal, and the flowers are quite reduced with usually no calyx limb and a very small (0.5-2 mm long) greenish to white or yellow corolla. The plants are variously hermaphroditic to monoecious, polygamo-dioecious, or sometime strictly dioecious. The fruits are usually rather small dry schizocarps, with the mericarps smooth to densely pilose or often pubescent with hooked hairs (which make the fruits appear as if they are covered with velcro). In some species the fruits are a little fleshy to quite juicy.
Puff & Mantell (1982) presented a revision of the Madagascar species of Galium, recognizing 5 species there. They did not present detailed descriptions for previously described species except for an emended description of G. polyacanthum. They presented a key (p. 58) to the species, with a significant typographical error: in the first lead, the number of leaf veins is reversed, so that the first species keyed, G. thunbergianum, is described as having the leaves "1-nerved" while it actually has 3 veins, and the remaining species are described as "3-nerved" but they all have 1 vein. This error has probably led to misidentifications of specimens collected after their study, so those should be double-checked in many cases.