48 Scientific Proceedings, Boyal Diihlin Society. 



rostellum. The filament is attached just behind the apex of the anther, and 

 broadens towards its base, where there is a well-marked fold as though it 

 were being kept forcibly bent backwards ; a great deal of the elasticity of the 

 filament is no doubt due to this fold. The rostellum is broad ; its anterior 

 margin is thin and recurved ; its posterior margin is thickened ; it is jointed 

 about its middle to the prolonged anterior border of the stigma. Immediately 

 behind the rostellum is the large, slightly concave stigma which occupies 

 almost the whole breadth of the column, and forms a great part of the roof 

 of the passage. 



This Dendrobiam is pollinated, as far as my observations go, entirely 

 by one species of bee. This bee Lieut.-Col. C. T. Bingham has very kindly 

 identified for me, from a very imperfect specimen, as Litliurgus atratus, a 

 species about the size of our honey-bee. 



When the bee enters an undisturbed flower, it forces its way along the 

 passage towards the nectary, till its head rests in the angle formed by the 

 thickened disc of the lip and the column, its weight depressing the lip 

 sufficiently to admit of the insertion of its proboscis into the nectary. So 

 far, the position of neither the anther nor the rostellum has been altered. 

 On looking at the semi-diagrammatic representation of a section through 

 the flower on Plate YI., fig. 1, it will be seen that the retreat of the bee 

 is impeded by the posterior margin of the rostellum and the free margin 

 of the anther, both of which point downwards and backwards. As the 

 rostellum is jointed on to the upper border of the stigma, and the anther 

 is jointed to the tip of the filament, the bee, as it retreats, tilts both these 

 structures. The rostellum is tilted upwards till it comes in contact with 

 the poUinia, and deposits on them some of its sticky secretion ; the anther 

 is continuously tilted till the polliuia, now smeared with the sticky secretion 

 of the rostellum, come in contact with the thorax of the bee, to which 

 they firmly adliere. As the bee further retreats, the pollinia, now adherent 

 to the bee, are drawn completely out of their cells. By this time, the anther 

 has been tilted till it is completely free of the clinandrium, and when, by 

 the further retreat of the bee, it has been completely released, the elasticity 

 of the filament comes into play, and the empty anther is jerked downwards 

 till it lies in front of the entrance to the passage (Plate VI., fig. 2), When 

 free from the flower, the bee flies away with the polliuia adherent to its 

 thorax; on visiting another undisturbed flower, it makes its way into the 

 passage of that flower, wliere the pollinia on its thorax come into contact with 

 the stigma, and adhere to it. As the bee retreats, it leaves the pollinia of the 

 first flower on the stigma of this second flower, and withdraws the pollinia 

 of this flower from tlieir cells, leaving the anther blocking the entrance to 



