4i8 



ANGIOSPERMAE—MONOCOTYLEDONES 



as an alighting-platform, and is directed upwards in consequence of the twisting of the 

 ovary. Its lower margin surrounds the column, so that a tube-shaped flower-entrance 



(-? 



l\ 



1^ 

 1 



M 



c. 



Fig. 387. Corallorrhirra innaia, R.Br, (after Herm. Mailer). A. Flower, seen from the front. 

 B. Side view of do., after removal of all the perianth leaves except the labellum. C. Label lum spread 

 out. D. Front view of ovary and column, after removal of all the other parts. col, column ; 

 «, nectary ; ov, ovary ; pp, lateral petals ; /^, labellum ; r, rostellum ; ss, lateral sepals ; $\ upper sepal. 



is formed. The stigma and anthers are partly protected by the position of the 

 labellum. The column is divided into three parts longitudinally. The middle part 

 of the upper half is the rostellum. The upper margin of the lower part of the 

 column projects at the point where it is fastened to the base of the rostellum as 

 a deep fold — the stigmatic hollow — like a vest-pocket. The middle part, the rostellum, 

 is a long membranous projection covered with thin mucilage, and hollowed out 

 slightly at the back ; a small, tongue-shaped, viscid mass projects beyond its crest. 

 The column with stigma and rostellum is united on both sides with a green, 

 membranous expansion, arched outside and hollowed inside. These two membranes 

 are connected with the lower ends of the pollinia and form in this wa}' a deep 

 cup to protect the pollen. 



The anther dehisces while still in the bud and then shrivels up, so that in the 

 fully open flower the pollinia are fully exposed, with the exception of their broad 

 lower ends, each of which is situated in a little cup. The upper end of the pollinia 

 rests on the crest of the rostellum. 



When an insect inserts its proboscis or head into the narrow space between 

 the vertical labellum and the rostellum, it cannot avoid touching the small, projecting 

 viscid mass and carrying away the pollinia which are already firmly fastened to it, 

 but are otherwise free. This can be easily seen by experiment. When another 

 flower is visited, the very thin pollinia, which are fastened on the proboscis or head 

 of the insect, are pressed in, and their broad ends force their way into the pocket-like 

 stigma. 



In spite of their smallness and inconspicuousness the flowers are extremely 



