THE ANGIOSPERMAE 1297 



III. Zoidiophily or Pollination by Animals 



This undoubtedly represents the highest stage in the evokition of 

 polHnation mechanisms and occurs in far the greater proportion of Angio- 

 spermae. It is important, however, to reahze that, although insects are the 

 most frequent agents, several other groups of animals are to a minor extent 

 concerned in pollination. Three groups are active agents, the bats, birds and 

 molluscs, and, although they are treated separately, it should be realized that, 

 at least as far as birds are concerned, most of the same factors operate that 

 we shall consider under insects. 



A. Pollination by Bats (Chiropteriphily) 



The number of authentic cases of bat pollination is small. Bats move 

 extremely rapidly and often at night and in some instances it has proved 

 difficult to determine whether the bat visiting flowers was really assisting 

 in pollination or whether it was engaged in catching night-flying insects, 

 who were really responsible for pollination, the presence of the bat being 

 merely incidental. 



Most of the available information rests on observations made in the 

 Royal Botanic Gardens in Trinidad, although the first recorded case came 

 from the Botanic Gardens at Buitenzorg in Java. The following description 

 of the pollination of Baiihinia megalandra illustrates one mode of operation. 



Baiihinia megalandra is a tropical American tree, reaching a height of 

 about 30 ft. It produces long white flowers which only open in the evening, 

 between 4 p.m. and 6 p.m., in the month of January. About 5.30 p.m. bats 

 of various species were seen flying very rapidly from flower to flower. It 

 was observed that their visits were immediately followed by a cascade of 

 white petals. Next morning the tree was examined and it was found that 

 not a single complete flower remained. In almost every case not only the 

 petals, but also the stamens had been removed. Apparently the bat settles 

 on the flowers by holding on to the stamens, at the same time getting a grip 

 with its legs on the recurved petals. 



The cause of their visits however, remains obscure, for the flowers 

 secrete no nectar and it can only be assumed that the bats were attracted 

 by the presence of night-flying moths which had been drawn to the flowers 

 by their pure white colour. Despite the damage caused to the flowers it was 

 observed that in almost every case the style was undamaged, and since in 

 the course of their activities the bats became liberally dusted with pollen 

 it was inevitable that some w^ould be scattered on the stigmas by so violent a 

 disturbance. 



Another case concerns the leguminous tree Eperua falcata in British 

 Guiana, regularly visited by bats. In this case only one particular species 

 of bat was concerned and it was found to have a brush-like tongue, resem- 

 bling that of a Humming Bird. Its behaviour, when visiting the flower, was 

 so similar to that of a moth that it seems clear that it did effect pollination. 



One of the most striking instances of bat pollination is that of the culti- 



