4IO 



ANGIOSPERMAEMONOCOTYLEDONES 



xxiv, 1888.) Darwin, Ridley, and Kirchner describe the flowers of this species as 

 autogamous. The pollen is loose and friable. The single grains are almost entirely 

 separate from each other and are only united by a few threads. The anthers dehisce 

 before the flower opens, when the pollinia fall on the upper margin of the stigma 

 situated below them, so that automatic self-pollination takes place. Cross-pollination 



by means of insects is, however, 

 possible. In this case the anterior 

 part of the labellum, bent at right 

 angles to the rest, serves as a platform 

 for them. The visitor then scatters 

 the pollen broadcast into the upright 

 flower, gets dusted with it, and may 

 transfer it to the stigma of another 

 blossom. After pollination has taken 

 place, the terminal lobe of the labellum 

 erects itself and closes the entrance 

 to the flower. 



2634. C. ensifolia Rich. ( = C. 

 xiphophylla Reichb. /.). (Kirchner, 

 'Beitrage,' pp. 10- 11 ; Delpino, 'Ult. 

 oss.,' II, p. 149.) The white flowers 

 of this species possess a yellow-brown 

 patch at the tip of the labellum, 

 which is continued behind by several 

 ridges of the same colour, running 

 down into the flower base. Nectar 

 is probably secreted in the sacculated 

 posterior part of the labellum. The 

 anterior part of the labellum, of 

 which the edges are turned upwards, can be easily pressed down, and it then 

 springs back into its original position by elasticity. Delpino therefore concludes 

 that this species can only be pollinated by means of insects, and describes the 

 manner somewhat as follows : The column is so bent downwards in the mouth 

 of the flower, that the visitor, backing out to fly away, smears a short length of its 

 back and head with the abundant tenacious mucilage of the stigma. The part thus 

 covered comes into contact immediately with the pollinia, fastening them firmly to it. 

 When the insect visits another flower, a part of these pollinia is deposited on the 

 stigma. It is easy to imitate this proceeding: if one touches the stigma with 

 a needle, some of the stigmatic mucilage adheres to it, and if the pollinia are 

 immediately touched with it, they cling sufficiently firmly. If they are then brought 

 into contact with the stigma of the same or another flower, they remain adhering 

 to it. Insect visitors obviously bring about the pollination of this species in 

 a similar manner. That insect-visits are adequate appears from the fact that in 

 many spikes all the pollinia are removed. Automatic self-pollination seems to be 

 excluded. 



Fig. 379. Cephalanthtra f>alUiis, Rich, (after Dar- 

 win). A. Flower, seen obliquely from the front. B. 

 Colnmn seen from the front after removal of all the 

 perianth leaves. C. Do., from the side : a poUiniom 

 can be seen above between anther and stigma, a, anther ; 

 /, terminal lobe of labellum; o, vestigial anther; p, 

 pollinia ; ^, stigma. 



