4i6 NATURAL SCIENCE. June. 



presence known by their perfumes. They may be of that greenish white 

 which is liardly distinguishable from the background of foHage, and 

 yet be able to attract myriads of nocturnal insects. Pass by at 

 any time in the day and not the faintest trace of perfume lingers 

 upon them, but paddle along at night and you wonder whence comes 

 the overpowering fragrance. 



Diurnal flowers and insects are comparatively scarce when 

 contrasted with those of the night. The great tubular blossoms 

 which glow in the sunlight are visited by humming-birds, butterflies, 

 and bees, but the hum and whirr of insect life, so characteristic of 

 night in the forest, is almost wanting. Where a few butterflies may 

 be seen fluttering lazily from flower to flower at noon, after sunset 

 moths are attracted in numbers by the great white blossoms, or the 

 fragrance of thousands of smaller and less conspicuous flowers. 



How difficult it is to trace these perfumes. Sometimes it is 

 quite impossible. Who recognises the odour of the mora' flowers, or 

 knows anything of the numerous scents that are wafted across the 

 narrow rivers after nightfall ? As certainly as we see a particular 

 kind of whitish flower, we can confidently state that it is odoriferous 

 at night, but hardly a single species is known in this way. In passing 

 along the creek, a perfume is suddenly wafted across, but where it 

 comes from is a problem not easily solved. Even that common 

 orchid, Epidendrum nocturnuin, which derives its specific name from the 

 fact that it distils its perfume after nightfall, is rarely known by this 

 character. We have seen cases where these orchids have been kept 

 for years without their owners knowing anything of their perfume, 

 and when it was discovered, this came about by the accident of 

 bringing a plant into the house for an evening. Other orchids are 

 quite as peculiar in this respect ; a most delicious odour may be 

 perceived at one particular time, and not be appreciable at any other. 



Some flowers open for an hour or two, and then, whether 

 fertilised or not, droop and wither ; others are able to try again 

 perhaps at the same time next morning or evening. Those which do 

 not fall may still have their particular time for fertilisation, when it 

 appears as if every effort is strained to attract the particular insect 

 whose agency is so urgently required. It is surprising to find that so 

 many are successful in these efforts. Even when their odour is not 

 appreciable to us, the bees find them out. They may be hidden away 

 under a tangle of bush-ropes, and not a single insect of the species 

 required be visible in the neighbourhood, but somehow or other, as 

 the flowers open, the bees or moths appear in considerable numbers. 



Flowers must be peculiarly sensitive at these times. Some, as 



1 A gigantic timber tree, belonging to tiie family Leguminosae, and forming 

 extensive forests in British Guiana. It grows from 130 to 150 feet high, and pro- 

 duces a very tough and close-grained wood, which is imported into this country in 

 considerable quantities for ship-building, even rivalling oak in its non-liability to 

 splinter. The bark is astringent, and useful for tanning. ^Ed. 



