ORCHIDEAE 



415 



species is enough to bring them out in relief against the dark ground of the wood, 

 thus rendering them conspicuous. Loew objects to this that the colouring resembles 



Fig. 38^. Neottia Nidus-avis, Rick, (after Herin. Muller). (i) Flower, seen from the side. 

 (2) Side view of the labellum. (3) Front view of do. ; the small circles represent drops of nectar. 

 (4) The column, seen from the side, a, anther; br, bract; co, corolla; ov, ovary; p, lateral petal; 

 ^', labellum ; po, polliniom ; r, rostellum ; ,y, sepals ; st, stigma. 



that of the dead leaves, and the plant therefore is often difficult to distinguish among 

 them. In his opinion the colouring is less for display than for protection. 



The flower mechanism agrees essentially 

 with that of Listera ovata, but the nectar is 

 concealed in a labellum which forms a shallow 

 bowl, and is therefore not quite so exposed 

 as in Listera. Also the poUinia adhere less 

 completely and securely. If insect-visits fail, 

 therefore, automatic self-pollination frequently 

 takes place, the very crumbling pollen falling 

 automatically upon the stigma. 



, Visitors. Herm. Miiller observed a nect-lkg. fly (Helomyza affinis Mg.), which 

 took up pollen in the most anterior part of its thorax. 



Fig. 384. Neottia Nidus-avis, Rick, (after 

 Herm. Muller). A. Flower. B. Column, 

 a, anther; n, stigma ; r, rostellum. 



Nectar concealed. 



830. Spiranthes Rich. 



2646. S. autumnalis Rich. ( = Ophrys spiralis Z.). (Darwin, op. cit., p. io6 ; 

 Kirchner, 'Flora v. Stuttgart,' pp. 180-1.) The small, whitish, horizontal flowers 

 of this species possess an odour of hyacinths. The reflex part of the labellum serves 

 as a platform for visitors, which find two globular nectaries on the lower part of the 

 organ, their abundant secretion being collected in a small receptacle situated below 

 them. The access to this is rendered very narrow by the nectaries and the 

 projecting margin of the stigma. The rostellum, forming a long, thin, narrow 

 process, is united with the stigma by two diverging shoulders. The middle part 

 of the posterior side of the rostellum forms a somewhat elongated receptacle for 

 mucilage. A longitudinal line on the anterior side is slightly hollowed over the 

 middle of this receptacle. Slight contact ruptures this anterior side longitudinally, 

 so that some mucilage exudes. The slit then extends to the back of the rostellum, 



