104 NOTES ON THE FERTILISATION 



orchids but these were passed by unnoticed. In the case of 

 this aerides nearly all the flowers produced seed pods which is 

 as I have already stated an uncommon occurrence for a large 

 flowered orchid. By experiment I found that any flower could 

 be fertilised by its own pollinia so that the chances of fertili- 

 sation are very much better than those of an orchid which like 

 Dendrobium crumenatum must be cross fertilised. 



Another very common orchid indigenous to Sarawak is 

 the Arundina speciosa popularly called the 'Bau orchid.' Ac- 

 cording" to Dr. Forbes this species has become so modified in 

 Java that self-fertilisation without the intervention of any in- 

 sect always takes place and all the flowers set seed pods. Now 

 this never occurs in Sarawak though the flowers can be artifici- 

 ally self-fertilised ; ordinarily very few seed pods are formed on 

 this orchid and fertilisation when it occurs at all is effected by 

 insect visitors. Dr. Forbes statement has been recently con- 

 firmed by Mr. Smith of Buitenzorg who cites other instances 

 of like phenomena viz : all the specimens of Tainia penangiana 

 from Java and Ambon cultivated in the Buitenzorg gardens 

 shew auto-fecundation but specimens sent over from Singapore 

 and grown in Buitenzorg under exactly the same conditions 

 are never self-fertilised : 



Spathoglottis plicata from western Java is self-fertilised 

 but a specimen from Ambon behaves differently : Phajus 

 Blumei in Singapore is in some individuals self-fertilised and 

 in others not so (H. N. Ridley) and Mr. Smith found the same 

 thing in Java where the majority however are self-fertilised. 

 It seems then that it is not very unusual to find orchids which 

 in general floral structure are almost typical and which never- 

 theless are habitually self-fertilised without the help of insects 

 all the flowers producing good seed pods ; as regard those 

 orchids wmich are dependent on insects the species which are 

 capable of self-fertilisation set far more pods than those which 

 must be cross fertilised. Further all the orchids have good 

 method of vegetative reproduction though this will not effect 

 a wide dispersal of the species except perhaps in such cases as 

 Arundina speciosa Whose lateral branches readily break off. at 



Jour. Straits Branch 



