66 SYLVICULTURE IN THE TROPICS w.i 



dodder (Cuscuta), which, on becoming a parasite, allows 

 its roots to perish in the ground whence it originated, 

 and, with similar habits, Cassytha, the former belong- 

 ing to the natural order of the Convolvulaceae, and the 

 latter to the Lauraceae. There are also the Oroban- 

 chaceae, such as Cistanche lutea, which shows a 

 preference for the roots of Capparis aphylla, but is 

 also found on those of Acacia, Zizyphus, etc. ; also the 

 handsome root-parasite of Malaya, the Rafjiesia, and 

 in montane regions of the Tropics Balanophora. 



In the fertilisation of flowers and in the distribution 

 of seeds animals are an important factor in the forma- 

 tion and maintenance of forests. Insects and birds are 

 largely responsible for pollination, especially the former, 

 and the character of the vegetation may easily vary 

 with the presence or absence of pollinating insects or 

 birds. 



Among the insects the Lepidoptera, Diptera, and 

 Hymenoptera are those which carry out these func- 

 tions, while among the tropical birds may be mentioned 

 the humming-birds, sun -birds, and honey -birds. So 

 dependent are certain trees on pollination by specific 

 kind of animals that they adapt their flowers to forms 

 or colours which will attract them and no others. 

 Thus plants fertilised by nocturnal insects will have 

 their flowers opening by night, white in colour, and 

 often sweet-scented. Others will shape the tube of the 

 corolla or the nectary in such a manner as to admit the 

 proboscis of certain moths or the beaks of certain birds. 

 It is true that certain noxious plants are also pollinated 

 by animals, e.g. the Loranthus longiflorus in India has 

 been found to be pollinated by the honey -bird (Arach- 

 nectra asiatica), 1 but nevertheless the amount of good 

 done far exceeds the evil. 



In the distribution of seed birds and mammals also 

 play an important part. In order to effect this a large 

 number of seeds are surrounded by an edible envelope. 

 We have already seen that the glutinous fruit of 



1 Indian Forester, vol. xxv. No. 12. 



