1298 A TEXTBOOK OF THEORETICAL BOTANY 



vated banana. Both male and female flowers are open at night and have a 

 rank odour and copious nectar which attract numerous bats. They hold on 

 to the bracts and thrust their heads into the flowers. As the cukivated 

 banana is parthenocarpic and seedless, no advantage accrues to the plant 

 and in the wild species, where pollination is needed, visits by bats have not 

 been observed. In Oroxylum indiciim (Bignoniaceae) in Malaya the flowers 

 have the same characteristics as those of the banana, namely dull colour, 

 rank scent and copious nectar, and they attract such numbers of bats that 

 the tree has been dubbed the " Midnight Horror ". 



The extent to which bats play a role in pollination still requires investi- 

 gation by botanists in the tropics. Observations hitherto have been few, 

 but there are arguments in favour of bats as pollinators which make them 

 at least worth consideration. Their addiction to eating sweet fruits, the 

 actual observation of nectar collection in some species and the long exten- 

 sible tongue, show that they have functional possibilities. Some Australian 

 marsupials have also been known to seek nectar, including both the non- 

 flying Tarsipes, which uses chiefly a honey diet, and the flying Petaiinis 

 sdiireiis, known in New South Wales as the " Sugar Squirrel ", but their 

 relationships to the flowers they visit are unknown. 



The Flying Fox, Pteropiis edulis, in Java, which feeds on the fleshy bracts 

 of Freycinetia species, may be another animal pollinator. 



B. Pollination by Birds (Ornithophily) 



The number of birds which effect pollination is small and is restricted 

 to a few tiny species, referred to collectively as the Humming Birds and 

 Honey Thrushes. These birds, often only an inch or so in length, hover 

 in front of flowers, thrusting in their long slender beaks to sup up the 

 abundant nectar. In most instances the pollination is effected directly by 

 the bird, which carries the pollen which is shed on to its head to another 

 flower where it comes into contact with the stigma, but certain types are 

 known in which the mechanism is indirect. In these latter cases the amount 

 of nectar secreted is often smaU and is produced in a position unsuitable 

 for the long beak or tongue of the bird. Such flowers, however, may attract 

 insects. By themselves these insects could not effect pollination, for the 

 shape of the flower is not suitable, but the presence of the insects attracts 

 smafl birds, who, while catching the insects, themselves bring about 

 pollination. 



Many flowers which are visited by nectar-hunting birds are not depend- 

 ent on them for pollination. Most of the true ornithophilous flowers are 

 coloured scarlet, a colour which is common in the tropics but rare else- 

 where. Nectar secretion is usually prolific but perfume plays little part in 

 the process of attraction. Another characteristic feature is the tough con- 

 sistency of the flower parts to withstand the onslaughts of the powerful 

 little visitors. 



The Floney Thrushes are direct pollinators, for nectar is their main diet 

 and they are not insectivorous. Their beaks form sucking tubes and are not 



