OF A FEW ORCHIDS IN SARAWAK. 101 



tions of a wasp (Vespa dorylloides) but as there remain only 

 very few pollinia this wasp cannot be considered an important 

 agent in effecting the fertilisation of Dendrobium crumenatum. 

 In the morning smaller bees (Nomia elegans, a eratina and 

 several Trigonas) accompany the Apis but they do not remove 

 the pollinia and in fact one of them, (the eratina), does not 

 trouble to enter the flower but pierces the base of the perianth 

 tube and thus reaches the sweet liquid nectar. 



In the case of the pigeon orchid the number of seed pods 

 produced is surprisingly small. An experiment was under- 

 taken to test the possibility for self-fertilisation. 



1 ' Self-fertilised ' a number of flowers. 



2 Grossed 2 flowers on the same spike. 



3 Crossed 2 flowers from different lateral off shoots, 

 arising from the same basal bulb. 



4 Crossed 2 flowers on shoots from different bulbs 

 in the same clump. 



5 Crossed 2 flowers belonging to entirely different 

 clumps. 



The result w T as that only those belonging to class 5 set 

 seeds shewing that for seed formation cross fertilisation in its 

 limited sense is essential. This however is unusual amongst 

 the orchids of Sarawak for most of them are capable of self- 

 fertilisation. One of the most remarkable facts in the life- 

 history of the pigeon orchid is the simultaneous flowering of 

 all the plants in the same area. The flower spikes make 

 their first appearance a week or so before the day of flower- 

 ing, they all blossom on the same day, the next day they are 

 faded and the series repeats itself at irregular intervals in- 

 definitely : the point to note is that the intervals are of vary- 

 ing length of time and yet flowering is quite simultaneous 

 throughout. This periodically corresponds with no known 

 seasonal variation and until the flower spikes make their first 

 appearance it is quite impossible to prophesy when the next 

 pigeon orchid day will appear. Such are the main facts of the 

 question but it is somewhat complicated by a more erratic 

 flowering on the part of a few individuals. In the following 



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



