62 NATIVE BRITISH ORCHIDACEyE 



Fertilisation. The rostellum consists of a ball of very adhesive material enclosed 

 in a membrane so excessively tender that it can be pierced by a human hair, and the 

 pollinia are firmly attached to its upper surface or cap. If a small feather is brushed 

 lightly upwards against the rostellum, the membrane bursts, and the cap comes away 

 with a certain quantity of the friable pollen attached, but the pollinia are not with- 

 drawn as a whole; but if the feather is so held that at the same time it slightly pushes 

 up the blunt end of the anther, the pollinia are set free, and are as cleanly removed 

 as they are by insects.^ 



The flower when ready for visitation stands out at right angles to the stem. Both 

 before and after this it is drooping, so that an insect can see at once which flowers 

 are best for its purpose. The front part of the lip forms a convenient platform to 

 alight on, and is joined to the cup containing nectar by a flexible elastic hinge, which 

 is depressed even by the weight of a fly, but springs back smartly when the weight 

 is removed. The flowers are mainly frequented by hive-bees. When a bee alights, the 

 lip bends down, opening the way to the nectar-hlled cup; when he takes flight, the 

 lip springs back, throwing the bee slightly upward, like a spring-board, ensuring that 

 he pushes up the end of the anther, and enabling the pollinia to be removed unbroken. 

 This beautiful and delicate mechanism is not found in any other European Epipactis; 

 in all other species the front part of the lip is rigid and fixed, there being no need for 

 the anther to be lifted up as the pollinia he free in the clinandrium. 



E. pakstris is the only European Epipactis pollinated by hive-bees. Darwin's son 

 watched hundreds of plants for some hours on three occasions, but although many 

 humble-bees were flying about, not a single one alighted on a flower, but he saw 

 about a score of flowers visited by hive-bees. He also saw the carrion-loving Sarco- 

 phaga carnosa on the flowers, and two had pollinia on their foreheads.- They were 

 probably seeking to deposit eggs or larvae amongst aphides in the flower, as observed 

 in the case of a blow-fly by Mr Burton on Aceras anthropophora (p. 165). Several 

 smaller flies {Calopa frigida, which haunts sea-weed) were seen visiting the flowers, 

 with pollen-masses adhering rather irregularly to the thorax, and three or four kinds 

 of Hymenoptera, one of small size being Crabro brevis, perhaps seeking small beetles 

 with which to provision its nest. These may be regarded as accidental visitors, though 

 they may sometimes bring about pollination, but they do not remove the pollinia so 

 effectively as hive-bees, which are the main agents of pollination. It is curious that 

 the nectar is unattractive to humble-bees. 



The American "Chatterbox", Epipactis gigantea, belongs to this section, and is very 

 like E. palustris. A large clump of it in Mr St Quintin's rock-garden, near Malton in 

 Yorkshire, flowered freely, but I could never see any insects going to it. The hmge 



' Darwin, Fert. Orch. ed. 2, p. 98. 

 ^ Ibid. p. 100. 



