20 FERTILISATION OP CLERODENDRON AND CANDOLLEA, 



bend is the point of greatest irritability. As the insect passes its 

 proboscis down the tube, it inevitably touches the sensitive spot, 

 and the column immediately flies over, the gynsecium striking 

 the bee (if of the ordinary size) on the thorax. If the column be 

 at the first or or pollen-bearing stage, the pollen is deposited on 

 the bee's thorax, where it clogs the hairs. When the insect has 

 completed its work at the flower it moves ofi", and to do this, it 

 has to come out sideways on account of the way it is clasped by 

 the column ; in this movement the pollen is further brushed out 

 of the anther cells by the hairs on the bee's back. If the insect 

 then visits a flower in which the pollen is all shed and the stigma 

 mature, the same action of the column occurs, but in this case the 

 sticky hairs of the stigma act as a brush to remove the pollen 

 from the bee as it moves off sideways. Consideration of the 

 structure and action of the flowers leading me to form the above 

 theoi-y of its mode of fertilisation, I experimented with flies, but 

 they were either too small or would not go into the flower 

 properly. I therefore went to a spot where the plants were fully 

 in blossom, and soon observed a small native bee working at the 

 blossoms. But on account of its small size it was not efiectual — 

 the column striking beyond the insect. I noticed, however, in 

 this instance and with other insects, that the sudden blow from 

 the column did not startle them at all, so that they are evidently 

 accustomed to it. My friend, Mr. J. D. Cox, who assisted me in 

 the field observations, called my attention to a hybrid Italian bee 

 flying about the blossom spikes, and we soon had the pleasure of 

 seeing the bee going to the open side of the flowers. On its 

 inserting its proboscis into the tube, the column at once flew over, 

 and where the anthers were not empty, a little cloud of pollen 

 was seen to fly from the force of the blow. Where the stigma 

 was mature, an examination of it afterwards showed pollen on 

 the surface. We watched the insect visit a large number of 

 flowers, always acting as described. It invariably visited the 

 lower flowers in a spike first, and as these are always more 

 advanced than the upper, and have the stigmas mature, there was 

 little probability of any blossom being fertilised with pollen from 



