OF A FEW ORCHIDS IN SARAWAK. 103 



blossom on a full clay. But such is not the case as we ascer- 

 tained from several observations : for instance on Feb. 29. 08 

 one solitary flowering spike found in a large clump of pigeon 

 orchids was marked and on May 25 w T hen the clump produced 

 its numerous spike this very same spike was in flower also. 

 Mr. H. N. Kidley has stated that the pigeon orchid days of 

 Singapore do not synchronise with those of Siam but if plants 

 be brought from Siam to Singapore these introduced plants 

 follow the Singapore dates behaving just like plants native to 

 Singapore. 



Now the general flowering of a number of individuals on one 

 particular day cannot be accidental and it is evident that the 

 flowering of Dendrobium crumenatum is not merely a habit 

 induced by endless repetition from time immemorial but also 

 that the species is in such exact relation to the climatic con- 

 ditions of the environment that a certain series of external 

 conditions produces precisely the same response in many or all 

 of the orchids which are subjected to those conditions : and 

 after all this phenomenon differs only in degree from the 

 seasonal changes of plants in countries where seasons are well 

 marked. 



From observations on cultivated plants of all orders it ap- 

 pears that the bees of Sarawak affect particularly all blue 

 flowers — the morning glory convolvulus for in instance is daily 

 visited by swarms of bees, these mostly of small species how- 

 ever — and too they are attracted by fragrant flowers of any 

 colour. Now none of the orchids are blue so that speaking 

 generally the only orchid flowers that are visited by bees are 

 such as have a fragrant odour. To this class belongs the 

 aerides odoratum known in Sarawak as the 'Lingga orchid.' 

 This orchid blooms once a year — in 1908 it flowered about the 

 middle of January : the inflorescences are large and conspicuous 

 and there is a fragrant odour. These flowers are visited by 

 large numbers of the big black carpenter bee (Xylocopa latipes) : 

 they pass from flower to flower seeking the nectar and at the 

 same time removing some pollinia. In the same neighbour- 

 hood there happened to be a big clump of sweet smelling pigeon 



R. A.Soc, No. 54. 1909- 



