90 NATIVE BRITISH ORCHIDACE.E 



Spiralis, as used by Linnaeus, was not the name of a species, but of a genus mistaken 

 for a species, and was not intended to apply solely to S. mtumnalis. To replace the 

 latter by S. spiralis Koch is to give priority to a name of 1839 over one of 1818. 



Fertilisation. Nectar has already collected in the hollowed base of the hp when 

 the flower opens. This attracts humble-bees, of which Darwin saw two species visit 

 the flowers. In one case the pollinia were attached to the upper surface of the pro- 

 boscis, as well as three viscid discs without pollinia, so that the bee had removed 

 the pollinia from four flowers and distributed all the pollen from three of them on 

 the stigmas of others. I saw the moth Vlusia gamma visit some flowers, but without 

 withdrawing the pollinia. When the flower first opens, the rostellum hes so near the 

 lip that the space between them will only admit a fine bristle, so that a bee's proboscis 

 cannot reach the nectar without touching the viscidium, which at once adheres, 

 becoming well glued to it in four or five seconds, the attachment being wonderfully 

 strong when the cement sets hard, which it does in about a minute. This early stage 

 of the flower is the most favourable for the removal of the pollinia. In a day or two 

 the opening becomes wider, the Hp turning more downwards, and, according to Prof. 

 Asa Gray, the column moving back from the lip. The passage is now large enough 

 for a proboscis bearing polHnia to enter. The pollen-leaves are very brittle, and large 

 pieces easily break off and adhere to the sticky stigma. Thus in a newly expanded 

 flower the poUinia can readily be removed, but pollen cannot be placed on the stigma, 

 which moreover is not so viscid as it is later. The anther-ceUs are pressed against the 

 back of the rostellum and open in bud, so that the pollinia come in contact with the 

 viscidium, to wliich they become firmly fixed by their projecting tlireads. Later the 

 anther-cells shrivel up, leaving the polhnia naked and free, ready for removal. The 

 narrow boat-shaped viscidium, filled with a milky extremely adhesive fluid, originally 

 forms an integral part of the rostellum. The groove beneath the latter is sensitive, 

 and if touched by a bristle or by the proboscis of an insect, instantly splits along its 

 whole length, the fissure running all round the edges of the viscidium, setting it free 

 for removal. Tliis does not occur spontaneously, and if insects are excluded, fails to 

 take place. The flowers are freely visited soon after expansion. Darwin found that 

 six out of seven open flowers on one spike, and all the eight expanded ones on another 

 had had the poUinia removed, i The long narrow viscidium is intended to adliere 

 longitudinally to the upper surface of a flat proboscis, as in humble-bees, and is in 

 contrast with the strap-shaped disc of Anacamptis pjramidalis, wliich curls round and 

 clasps the cylindrical proboscis of Lepidoptera. 



I Darwin, Fert. Orch. ed. 2, p. iii. 



