Chap. VII. MOBMODES IGKEA. 217 



strange position of the labellnm, perched on the summit 

 of the column, ought to have shown me that here was 

 the place for experiment. I ought to have rejected 

 the notion that the labellum was thus placed for no 

 good purpose. This plain guide was overlooked, and 

 for a long time I completely failed to understand the 

 structure of the flower. 



We have seen that when the poUinium is ejected 

 and swings upwards, it adheres by the viscid surface 

 of the disc to any object projecting beyond the edge 

 of the labellum directly over the column. When thus 

 attached, it forms an irregular hoop, with the torn-off 

 anther-case still covering the pollen-masses which are 

 close to the disc, but protected from adhering to it 

 by the dependent curtain. Whilst in this position 

 the projecting and bowed part of the pedicel would 

 effectually prevent the pollen-masses from being placed 

 on the stigma, even supposing the anther-case to have 

 fallen off. Now let us suppose the poUinium to be 

 attached to an insect's head, and observe what takes 

 place. The pedicel, when first separated from the ros- 

 tellum, is damp ; as it dries, it slowly straightens 

 itself, and when perfectly straight the anther-case 

 readily drops qff. The pollen-masses are now naked, 

 and they are attached to the end of the pedicel by 

 easily ruptured caudicles, at the right distance and in 

 a proper position for their insertion into the adhesive 

 stigma, as soon as the insect visits another flower. 

 Thus every detail of structure is now perfectly adapted 

 for the act of fertilisation. 



When the anther-case drops off, it has performed its 

 triple function ; namely, its hinge as an organ of sense, 

 its weak attachment to the column as a guide causing 

 the poUinium at first to swing perpendicularly upwards, 

 and its lower margin, together with the curtain of the 



