Chap. II. OPPEE^. 79 



the chief facts with respect to the movements of the 

 poUinia, all due to the nicely regulated contraction of 

 that small portion of membrane (together with the 

 pedicel in the case of Habenaria) lying between the 

 layer or ball of adhesive matter and the extremity of 

 the caudicle. In a few cases, however, as with some 

 of the species of Disa and Bonatea, the caudicles when 

 removed from their cells do not undergo any movement ; 

 the weight of the pollen-masses sufficing to depress 

 them into a proper position. In most of the species of 

 Orchis the stigma lies directly beneath the anther-cells, 

 and the poUinia simply move vertically downwards. 

 In Orchis pyramidalis there are two lateral and inferior 

 stigmas, and the poUinia move downwards and outwards, 

 diverging to the proper angle, so as to strike the two 

 lateral stigmas. In Gymnadenia the pollinia move 

 only downwards, but they are adapted for striking the 

 lateral stigmas, by being attached to the upper lateral 

 surfaces of the proboscides of Lepidoptera. In Nigri- 

 tella they move upwards, but this depends merely on 

 their being always affixed to the lower side of the 

 proboscis. In Habenaria the stigmatic surface lies 

 beneath and between the two widely-separated anther- 

 cells, and the pollinia here converge, instead of diverg- 

 ing as in Orchis pyramidalis, and likewise move down- 

 wards. A poet might' imagine that whilst the pollinia 

 were borne through the air from flower to flower, 

 adhering to an insect's body, they voluntarily and 

 eagerly placed themselves in that exact position, in 

 which alone they could hope to gain their wish aud 

 perpetuate their race. 



