CHAP. IV. LYTHRUM SALICAEIA. 147 



is brought, not into any pathway from the outside 

 towards the nectar-secreting recesses of the flower, but 

 into the circular route which insects follow in proceed- 

 ing from one nectary to the other. In Scrophularia 

 aquatica the pistil is bent downwards from the mouth 

 of the corolla, but it thus strikes the pollen-dusted 

 breast of the wasps which habitually visit these ill- 

 scented flowers. In all these cases we see the supreme 

 dominating power of insects on the structure of flowers, 

 especially of those which have irregular corollas. 

 Flowers which are fertilised by the wind must of 

 course be excepted; but I do not know of a single 

 instance of an irregular flower which is thus fertilised. 

 Another point deserves notice. In each of the three 

 forms two sets of stamens correspond in length with 

 the pistils in the other two forms. When bees suck the 

 flowers, the anthers of the longest stamens, bearing the 

 green pollen/ are rubbed against the abdomen and the 

 inner sides of the hind legs, as is likewise the stigma of 

 the long-styled form. The anthers of the mid-length 

 stamens and the stigma of the mid-styled form are 

 rubbed against the under side of the thorax and be- 

 tween the front pair of legs. And, lastly, the anthers 

 of the shortest stamens and the stigma of the short- 

 styled form are rubbed against the proboscis and chin ; 

 for the bees in sucking the flowers insert only the front 

 part of their heads into the flower. On catching bees, I 

 observed much green pollen on the inner sides of the 

 hind legs and on the abdomen, and much yellow 

 pollen on the under side of the thorax. There was 

 also pollen on the chin, and, it may be presumed, on 

 the proboscis, but this was difficult to observe. I had, 

 however, independent proof that pollen is carried on 

 the proboscis ; for a small branch of a protected short- 

 styled plant (which produced spontaneously only two 



