ORCHIDEAE 



403 



hybridization by Lepidoptera between two species which have fixed their pollinia 

 to the upper and lower sides of the proboscis respectively, arises from the fact that 

 the flowers are sometimes half twisted round thus making transfer possible. 



2620. Habenaria bifolia R. Br. ( = Platanthera bifolia Rich.; P. solstitialis 

 Boenn. ; Orchis bifolia L. ; and Gymnadenia bifolia Meyer). (Darwin, op. cit., 

 PP- 73-4; Herm. Miiller, 'Fertilization/ p. 533, ' Alpenblumen/ pp. 70-2; 

 Kirchner, 'Flora v. Stuttgart,' p. 171; MacLeod, Bot. Jaarb. Dodonaea, Ghent, 

 V, 1893, p. 323; Sprengel, 'Entd. Geh.,' pp. 405-6.) The white moth flowers of 

 this species exhale a strong odour of pinks, particularly at night, and have a thin 

 spur 13-21 mm. long, which is often three-quarters full of nectar. The pollinia 

 adhere to the left and right sides of the proboscis of a moth, then turn in- and 



Fig. 372. Habenaria bifolia, R.Br, (after Herm. MuUer). A. Flower, seen from the side (almost 

 X 2). B. Do., seen directly from the front (x 4). C. Reproductive organs and entrance to the spur, 

 seen directly from the front (almost X 16). D and E. Pollinia and their disks after complete torsion 

 (almost X 16). a, anther; a' a', vestigial anthers; ar and al, right and left anther-lobes; br, bract; 

 c, caudicle ; d and d', disks ; n, nectary (in which secretion rises to x ) ; o, opening of spur ; ov, ovary ; pp, 

 upper petals; p', labellum; j.y, lateral sepals; s', upper sepal; st, stigma. 



downwards by the contraction of the caudicles, and, clinging to the base of a visitor's 

 proboscis, are brought to the stigma situated between the two disks. A. de Bonis 

 (Riv. fis. mat. sc. nat., Pavia, xiii, 1893) states that the species is sometimes fertilized 

 by means of the wind. 



Visitors. The following were recorded by the observers, and for the localities 

 stated. 



Darwin, Noctuid moths. Rogenhofer, the hawk-moth Sphinx pinastri L. (with 

 pollinia on its palps). Heinsius (Holland), 2 moths Hadena monoglypha H/n.i 

 and 5, and Plusia gamma L. (with pollinia on their palps) (Bot. Jaarb. Dodonaea, 

 Ghent, iv, 1892, pp. 1 16-17). Scott-Elliot (Dumfriesshire), large moths ('Flora of 

 Dumfriesshire,' p. 168). 



D d 2 



