Chap. IV. LISTEEA OVATA. 



119 



and rendered useless. I once found an injured flower 

 which had been pressed and had exploded before fully 

 expanding, and the anther with the enclosed pollen- 

 masses was permanently glued to the crest of the ros- 

 tellum. The rostellum, which is naturally somewhat 

 arched over the stigma, quickly bends forwards and 

 downwards at the moment of the explosion, so as then 

 to stand (fig. B) at right angles to the surface of the 

 stigma. The pollinia, if not removed by the touching 

 object which causes the explosion, become fixed to the 

 rostellum, and by its movement are likewise drawn a 

 little forward. If their lower ends are now freed by a 

 needle from the anther-cells, they spring up ; but they 

 are not by this movement placed on the stigma. In 

 the course of some hours, or of a day, the rostellum 

 not only slowly recovers its original slightly-arched 

 position, but becomes quite straight and parallel to 

 the stigmatic surface. This backward movement of 

 the rostellum is of service ; for if after the explosion it 

 had remained permanently projecting at right angles 

 over the stigma, pollen could not readily have been 

 deposited by insects on the viscid surface of the 

 stigma. When the rostellum is touched so quickly 

 that the pollinia are not removed, they are, as I have 

 just said, drawn a little forward ; but by the subse- 

 quent backward movement of the rostellum they are 

 pushed back again into their original position. 



From the account now given we may safely infer 

 how the fertilisation of this Orchid is effected. Small 

 insects alight on the labellum for the sake of the 

 nectar copiously secreted by it ; as they lick this they 

 slowly crawl up its narrowed surface until their heads 

 stand directly beneath the overarching crest of the 

 rostellum ; when they raise their heads they touch the 

 crest ; this then explodes, and the pollinia are instantly 



