THE MONOCOTYLEDONES 2099 



detached from the pencil. As they dry they bend forwards and downwards 

 so that they will impinge on the stigmatic surface of the next flower that the 

 insect visits. Moreover it can be shown that the pollen masses of which the 



Fig. 2035. — Orchis mascula. A, Labellum and column in face view. B, Flower in section 

 showing the caudicles of the pollinia covered by the prominent rostellum which stands 

 over the entrance to the spur. C, Two pollinia attached by their retinacula to the head 

 of an insect. (After Darivin.) 



pollinia are composed are attached strongly to one another by a viscid sub- 

 stance so that only a small number are actually detached on the stigmatic 

 surface. In fact many stigmas can be pollinated by the same pollinium 

 as the insect passes from flower to flower. 



The genus Ophrys includes some thirty species with a wide geographical 

 distribution in temperate climates. In Britain we have O. apifera (Bee 

 Orchid), O. insectifera (Fly Orchid) and O. sphegodes (Early Spider Orchid). 

 They are terrestrial species whose floral structure is more or less similar to 

 that of Orchis, except that there is no spur. In O. apifera (Fig. 2036) we 

 have one of the few examples of an orchid which can be self-pollinated, for 

 if the pollinia are not removed by a visiting insect they drop out of the 

 anthers and dangle on their long caudicles in front of the stigma against 

 which they are almost certain to be blown or knocked. 



Anacamptis [A. pyramidalis in Britain) is another genus closely related 

 to Orchis. The flowers are fragrant and nectar is formed at the end of a long 

 spur. There are two round stigmatic surfaces, one at each side of the 

 rostellum. The adhesive foot of the caudicles is saddle-shaped and fits over 

 the proboscis of a visiting insect, to which it and the attached pollinia 

 adhere. As the caudicles dry they bend forward at right angles so that the 



