306 MONOCOTYLEDONES. 



containing one ? , nnd the posterior 8-10 $ -flowers in two series ; in some the 

 stamens in the single c? -flowers unite and form a columnar " synaudrium " 

 (e.g. in Iricffenbachia, Colocasia, Alocasia, Caladium, Taccarnm, ^ijngoninm). 

 A remarkable spadix is found in Spathicarpa ; it is united for its entire length, 

 ou one side, with the spathe, and the flowers are arranged upon it in r-iws, the 



9 to the outside, and the $ in the middle (Zostera has a similar one). Pistia 

 similarly deviates considerably, it is a floating water-plant, with hairy, round 

 rosettes of leaves ; in it also the spathe and spadix are united ; at the base a 



$ -flower is borne, which consists of one unilocular ovary, and above several 



$ -flowers, each composed of two united stamens. 



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 5-padix (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 30C. 

 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. 

 Zantedescliia. 



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. Acorns 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. 



USES. Many species have pungent, and even poisonous properties (e.g. 

 Dieft'enbachia, Lagenandra, Arum), which are easily removed by boiling or 

 roasting; the rhizomes of many species of Caladium, Colocasia (C. antiquoi urn, 

 esculents etc.), are very rich in starch, and in the Tropics form an important 

 source of food. An uncommon occurrence in the order is the highly aromatic 

 rhizome of Acorus calamus; this contains calamus-oil and acorin which are used 

 in perfumery. Many are ornamental plants, e.g. Zantedescliia ceilnopica (South, 



