BIOLOGY. The inflorescences are adapted for _insect-pollination_; they are protogynous, since the viscous, almost sessile stigmas come to maturity and wither before the pollen, which is generally dehisced by apical pores, is shed; some pollinate themselves freely by the pollen from the higher ♂-flowers falling upon the ♀-flowers below them, and in some it is conjectured that the pollination is effected by snails. The coloured spathe, and the naked end of the spadix (often coloured) of certain genera function as the coloured perianth in other orders; during flowering a very powerful smell is often emitted. _Arum maculatum_ is worthy of notice; small flies and midges creep down into the spathe, between the sterile flowers (Fig. 301 _b_), which are situated where the spathe is constricted, and pointing obliquely downwards prevent the escape of the insects; in the meantime, the stigmas are in a condition to receive any pollen they may have brought with them; after pollination the stigmas wither, and exude small drops of honey as a compensation to the flies for their imprisonment; after this the anthers (_m_) open and shed their pollen, the sterile flowers wither, and the insects are then able to escape, and enter and pollinate other inflorescences.--In many, a _rise of temperature_ and evolution of carbonic acid takes place during flowering; a spadix may be raised as much as 30°C. above the temperature of the surrounding air.--Again, under certain conditions, many species absorb such large quantities of water by their roots that water is forced out in drops from the tip of the leaf; this may often be observed in _Zantedeschia_. About 900 species in 100 genera. Home, the Tropics, especially S. America, India, and the Indian Islands, preferably in shady, damp forests growing as epiphytes upon trees, and on the banks of streams. Outside the Tropics few are found. _Acorus calamus_ was introduced into Europe from Asia about 300 years ago; it, however, never sets any fruit, as the pollen is unfertile. In England _Arum maculatum_ is a very common plant; this and _A. italicum_ are the only native species. _Colocasia antiquorum_ comes from Polynesia and the Indian Islands, and also _Alocasia macrorrhiza_. Fossils in Cretaceous and Tertiary.