414 ANGIOSPERMAE—MONOCOTYLEDONES 



middle of the long, narrow, downwardly curved labellum. The large, thin, leaf-like, 

 pointed rostellum contains mucilage, which exudes in white, tenacious drops at the 

 slightest touch. The anther situated behind the rostellum dehisces while the flower 

 is still in the bud, so that when it opens the pollinia are freely exposed, lying on their 

 backs with their apices converging to the upper end of the rostellum, which then 

 curves slowly over the stigmatic surface. 



The smaller visitors, consisting largely of ichneumon-flies, use the lower end of 

 the labellum as an alighting-platform, creep slowly upwards, licking all the nectar out 

 of the groove from the bottom to the top, and ultimately strike their head against the 

 rostellum, which immediately exudes two small, white drops of mucilage. These run 

 together and fasten on one hand to the side of the head and on the other to the tips 

 of the pollinia, so that the latter are carried away by the visitor. During this process, 

 the rostellum curves quite over the stigma, thus preventing autogamy. It then 

 moves slowly back, leaving the stigma once more exposed. In the meantime this 

 has become very sticky, and the emptied nectar-groove again fills with nectar. 

 Should the insect now visit a flower from which the pollinia have already been 

 removed, the stigma is struck by the pollinia, part of which adhere to it. Crossing 

 is therefore always effected, and usually between separate stocks. 



Warnstorf describes the pollen-grains as united into tetrads, and 50-6 /a in 

 diameter. 



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



stated. — 



Sprengel saw ' a small beetle with black head and scutellum and brown elytra, 

 which had taken such a head-adornment (pollinia) from a flower.' This was 

 apparently the regular visitor Grammoptera laevis F. He also repeatedly observed 

 an ichneumon-fly ' bearing a pair of pollen-clubs in its head.' Herm. Miiller saw 

 Braconids and Ichneumonids effect pollination. Kaltenbach identified these as — 

 {a) Braconidae: i. Alysia sp., one; 2. Microgaster globata Z., var. rufipes Nees; 

 (3) Ichneumonidae : 3. Campoplex sp., one ; 4. Cryptus, 8 individuals of 3 sp. ; 

 5. Amblyteles uniguttatus Grav., one; 6. Phygadenon sp., 2; 7. Tryphon sp., 2. 

 Miiller also observed the humble-bee Bombus agrorum F., nect-lkg., but not removing 

 pollinia. RIacLeod (Belgium), a bee (Andrena sp.), 2 other Hymenoptera, and 

 a beetle. Plateau (Belgium), the hover-fly Melanostoma mellina Z. ; (Pyrenees), the 

 beetle Rhagonycha fulva Scop. (= R. melanura F.), nect-lkg. (Bot. Jaarb. Dodonaea, 

 Ghent, iii, 1891, p. 309). Darwin (England), 2 ichneumon-flies (Hemiteles sp., and 

 Cryptus sp.) with pollinia attached to the front of the head. 



2644. L. cordata R. Br. (Darwin, op. cit., p. 124.) — Darwin describes the 

 flower mechanism of this species as agreeing essentially with that of L. ovata. 



Visitors. — Darwin says there are small Diptera and Hymenoptera. 



829. Neottia L. 



Flowers with exposed to half-concealed nectar. 



2645. N. Nidus-avis Rich. ( = Ophrys Nidus-avis Z.). (Herm. Miiller, 

 ' Ferdsn.,' p. 531 ; Darwin, op. cit., p. 125 ; Kirchner, ' Flora v. Stuttgart,' p. 179 ; 

 Kerner, 'Nat. Hist. PI.,' Eng. Ed. i, 11, p. 195; Loew, ' Bliitenbiol. Floristik,' 

 p_ 344.) — Kerner says that the pale yellow-brown colouring of the plants of this 



