POLLINATION 25 



other European orchid, is provided in the shape of two erect guiding plates 

 (/') on the base of the hp converging towards the narrowed spur-entrance, 

 which acts like an old wife's gadget for threading a needle. In several species of 

 Orchis, etc., a groove in the base of the lip answers a similar purpose, but with 

 less accuracy. If a fine bristle is inserted between these plates, it is automatically 

 guided till it pushes against the pouch of liquid in which the viscidium is immersed. 

 This swings back and exposes the strongly adhesive under-surface of the disc. The 

 bristle, or in the case of Lepidoptera the proboscis, shdes along the centre of the 

 viscidium which coils round it and cements itself thereto. The proboscis of Acontia 

 luctuosa figured by Darwin i bore seven pairs of polUnia arranged with perfect sym- 

 metry. The moth Caradrina hlanda had no less than eleven pairs. The flowers are well 

 visited by insects. Darwin found that six plants in Devonshire had had both pollinia 

 removed from 102 flowers. A spike from Folkestone with 49 flowers produced 

 48 seed-capsules. Not without reason did Darwin remark, "How well moths and 

 butterflies perform their office of marriage priests l"^ Even a human hair is stiff 

 enough to depress the pouch, and the strap-shaped viscidium adheres to it. If the 

 pouch be pushed only slightly, it springs back to its original position. 



I saw Apis mellifica ^ (liive-bee) withdraw two pairs of pollinia at Guildford from 

 a spike of this species, and saw Calioxjs rujescens Lep. $ visit another without with- 

 drawing pollinia. The spur oi A. pyramidalis contains no free nectar, but is dry inside. 

 The outer and inner walls are, however, separated to an unexpected degree, and the 

 inner skin is extremely delicate and easily pierced. If a spur from wliich the tip has 

 been cut off is gently pressed, large drops of fluid are expelled. On the other hand 

 in the very similar spur of Gjmnadenia conopsea, which is full of nectar for at least 

 one-third of its length, the inner and outer skins of the spur are closely united, though 

 the inner presents the same structure and papillas as those of A. pjramidalis^ It does 

 not follow that the Hquid between the walls of the latter species is nectar. The spur 

 may be simply an alluring drinking fountain on a thirsty day, the visitors piercing 

 the tender inner skin to suck their fill. The immense value of this may be easily 

 realised by anyone who has noticed the numbers of bees and butterflies setding on 

 sandy soil with a tiny trickle of water beneath. The author some years ago saw by 

 the roadside in the Malay Peninsula what appeared to be a large circular white flower 

 variegated with blue, the hke of which he had never seen before. On his eager ap- 

 proach it dissolved into a cloud of white and blue butterflies setded round a patch 

 of wet sand. 



I Ihid. p. 31, Fig. 4. ^ Ibid. p. 34. 3 Ibid. p. 40. 



