90 OUR NATIVE ORCHIDS 



the column to sip the nectar, to tip the little boat of pollen 

 that has just stuck to it, right against the stigma of the same 

 flower ? Not in the least, for in the young just-opened 

 flower the column lies so close to the tip that the bee can 

 barely force her proboscis through; moreover the stigma is 

 not sticky, and would not hold the pollen even if the bee 

 could get it there. But as the flower grows older, the bent 

 column slowly raises itself from the lip (Plate XXXVI. , Fig. 2), 

 leaving a much wider aperture into which the proboscis can 

 go far enough to unload the pollen on the surface of the 

 stigma, which has by this time become sticky. Asa Gray 

 writes humbly to Darwin, who called his attention to this 

 widening of the passage, "It is so sticky we wonder how we 

 overlooked it." 



Still it may not be quite clear how this widening of the 

 passage ensures cross fertilisation, for might not the bee 

 carry the boat-loads of pollen from a young flower to an 

 older flower on the same spike, and cause self fertilisation ? 

 We must turn to Darwin again for a simple observation which 

 gives the key to the situation. He noticed that "the bees 

 always alighted at the bottom of the spike, and crawling 

 spirally up it, sucked one flower after another. I believe," 

 he adds, "bumblebees generally act in this manner when 

 visiting a dense spike of flowers, as it is the most convenient 

 method — on the same principle that a woodpecker always 

 climbs up a tree in search of insects." This seems an 

 insignificant observation, but see the result. The bee goes 

 first to the lowest flower, and crawling spirally up the spike, 



