THE MONOCOTYLEDONES 



201' 



leaves. The flower spathes are white or yellow in colour and enclose a 

 yellow spadix. 



The most important member of the Colocasioideae is the genus Colo- 

 casia, which includes C. antiquonim whose rhizome is the source of Taro, 

 an important vegetable in the tropics. In the raw state it is poisonous but 

 when boiled it loses its poisonous nature and forms a valuable food. Species 

 of Alocasia which are found in tropical Africa are favourite greenhouse 

 plants on account of their variegated leaves. 



The Aroideae include the genus Arum of which A. maailatiim (Cuckoo 

 Pint) is wild in Britain, and A. italicum, a larger species, occurs rarely in 

 southern counties. The pollination mechanism of the Cuckoo Pint is 

 remarkable. The large spathe which surrounds the inflorescence acts not 

 merely as an attraction, in those species where it is brightly coloured, but 

 also as a protection against wind. In the same way the spadix, which is 

 often contrastingly coloured, also serves for attraction and possibly for 

 protection. Small flies, trying to escape from the wind, congregate in the 



Fig. 1955. — Ariaii maculntinii. Portion of the 

 spathe cut open to show the flowers. For 

 poHination see in text. 



spathe and crawl downwards into the more sheltered part. They are also 

 attracted by the warmth generated in the spadix as the result of the very 

 rapid respiration of its stored starch. Guided by the spadix they success- 

 fully pass below the constriction in the spathe and between the down- 

 wardly projecting hairs. Further down they pass another cluster of similar 

 hairs and reach the base of the spathe (Fig. 1955). Unable to find a 



