4i6 



ANGIOSPERMAEMONOCOTYLEDONES 



and the cavity of the anther is exposed. Each loculus contains two very crumbling 

 pollinia, which are separated above, and united in the middle by elastic threads. 



The upper part of the loculi, pressed against the back of the rostellum, dehisces 



before the flower opens, 

 the pollinia thus coming 

 into contact with the back 

 of the mucilage-receptacle. 

 The oblique surface of the 

 stigma projects below the 

 rostellum. Darwin ob- 

 served humble-bees as 

 visitors; the mucilage-re- 

 ceptacles with the adherent 

 pollinia cling to their pro- 

 boscides; thus only the 

 lateral, furcate parts of the 

 rostellum were left. After 

 the flower has been open 

 one or two days, the la- 

 bellum moves away a little 

 from the rostellum, thus 

 widening the approach to 

 the stigma, which is now 

 encountered by humble- 

 bees bringing pollinia. 

 Not only crossing of separate flowers, but usually also of separate stocks is thus 

 effected, as humble-bees are in the habit of sucking nectar from the inflorescence 

 from below upwards. 



Fig. 385. Spiranthes autumnalis. Rich, (after Darwin). A. Lateral 

 view of a flower, after removal of the two lower perianth leaves ; the 

 labellum is fringed anteriorly. B. Do., enlarged still more, after re- 



moval of all the perianth leaves. The position of the labellnm and the 

 upper sepal is indicated by dotted lines. C. Stigma and rostellum, with 

 the embedded, central, boat-shajjed disk, seen from the front. D. Do., 

 after removal of the disk. E. Disk, removed from the rostellum, greatly 

 enlarged, viewed posteriorly, with the attached elastic threads of the 

 pollinia ; the pollen-grains have been removed from the threads, a, anther ; 

 cl, edge of clinandrum ; , nectar receptacle ; p, pollinia ; r, rostellum ; 

 s, stigma ; /, threads of the pollinia. 



831. Goodyera R. Br. 



Nectar concealed. 



2647. G. repens R. Br. (=Satyrium repens L.). (Darwin, op. cit., p. 103; 

 Herm. Miiller, 'Alpenblumen,' pp. 75-7; Kirchner, 'Flora v. Stuttgart,' pp. 179-80.) 

 The horizontal flowers of this species are small, whitish in colour, and feebly fragrant : 

 they are united into unilateral spikes of about 20 flowers. The shield-shaped, almost 

 square rostellum projects a little beyond the stigma. On being lightly touched the 

 surface of this projection exudes mucilage, and is easily pressed upwards, when it 

 carries with it a membranous strip to the posterior end of which the pollinia adhere. 



The anther-lobes dehisce while still in the bud, the pollinia clinging with thei 

 anterior sides to the back of the rostellum, and being thus almost entirely expose 

 The posterior, excavated part of the labellum contains nectar ; the anterior groove 

 part is bent downwards and serves as a platform. In consequence of the narrownes 

 of the entrance to the stigma between the labellum and the rostellum, the probosci 

 of an insect probing for nectar strikes against the latter and removes the ppllii 



