REMOVAL OF POLLEN IN ORCHIDS. 



255 



is licked up by small beetles. In other instances the back of the lip is produced 

 into a spur lined with cells full of sweet juice, to which insects obtain access by- 

 piercing the walls of the cells. The genus Orchis affords an example of this. 

 Honey of a sort peculiarly attractive to butterflies is secreted in the tubular spur 

 in other cases, such as Gymnadenia and Habenaria (see fig. 258 ', p. 227). 



Two separate particles of viscid matter are often produced on the rosteUum, 

 each being in connection with one only of the pollen-masses (e.g. Habenaria 



Fig, 268. — Withdrawal and deposition of pollinia in the flowers of an Orchid 



Flowering spike of the Broad-leaved HeUeljorine (^Epipactis latifolia) upon which a wasp {Vespa Aiistriaca) is alighting. 

 ^ A flower of the same seen from the front. » Side view of the same flower with the half of the periantii towards the 

 observer cut away. * The two pollinia joined by the sticky rosteUum. fi The same flower being visited by a wasp, which 

 is licking honey and at the same time detaching with its forehead the tip of the rosteUum together with the pair of 

 pollinia. 6 The wasp leaving the flower with the pollinia cemented to its head ; the pollinia are erect. ? The wasp 

 visiting another flower and pressing its forehead with the polUnia (which in the meantime have bent down) against the 

 stigma. 1 nat. size ; the other figures x 2. 



chlorantha, the Large Butterfly Orchis). Insects then frequently only draw one 

 of the pollen-masses out of the anther, instead of both, as they leave the flower. 

 In species of the Twayblade genus (Listera) the rosteUum is scale-like and 

 arches over the stigmatic surface. At the commencement of the flowering 

 period it is not connected with the pollinia, but the moment it is touched it 

 exudes a drop of viscid fluid which sticks, on the one hand, to the body touching 



