176 MONOCOTYLEDONS 



of the flower we see, immediately over the entrance to the 

 spur and attached to the column, two lateral stigma-lobes 

 (sg), and just above these a median beaked structure — the 

 rostellum {f) — ^which is supposed to represent a third stigma- 

 lobe, though it is incapable of acting as a receptive stigma. 

 Above and behind the rostellum is a single median stamen, 

 consisting of two lobes (a) separated by a somewhat broad 

 connective (cd). In addition to this fertile stamen there 

 occur two lateral stamens without anthers — staminodes (si) — 

 attached as appendages to the column, behind the two lateral 

 stigma-lobes. The single anther stands erect, and dehisces 

 towards the rostellum. Each anther-lobe is one-chambered, 

 and contains many pollen-grains adhering together to form 

 a pear-shaped mass — the poUinium {po, fig. 223) — which 

 possesses a short stalk — the caudicle (c). The rostellum is 

 shaped like a little bowl {b\ and contains a gummy mass. 

 The caudicles are attached by their bases to two small balls 

 [d) of this gummy substance. The ovary is one-chambered, 

 with many ovules (forming after pollination) on three parietal 

 placentae. Pollination. — There is no free honey in the flower ; 

 insects pierce the internal lining of the spur and suck the juice 

 from the wound. The flower is visited by bees and flies. The 

 labellum acts as a platform on which the insect alights. A bee 

 pushing its tongue into the spur must of necessity touch the 

 rostellum ; the consequence is that one or both pollinia are 

 transferred to its head, where they adhere by means of the ad- 

 hesive bases of their caudicles. At first the pollinia stand erect 

 on the head of the bee, but they subsequently bend slowly 

 forward, though remaining fixed at their bases. As a result of 

 this movement, the pollinia will inevitably be pushed against 

 the stigma-lobes of a subsequently visited orchid-flower. Did 

 the pollinia remain erect they would, in all probability, be 

 rubbed against the rostellum of a flower visited later : so that 

 no pollination would take place. [The action of the bee in 

 pollinating Orchis - flowers may be imitated by thrusting a 

 sharp-pointed lead pencil into the entrance of the spur ; the 

 separation of the pollinia and their subsequent movements 

 will then also be seen.] True morphology of the flower.— 

 Hitherto no reference has been made to a peculiarity in the 

 Orchis-flower. The wall of its inferior ovary in its growth 

 causes the flower to execute half a revolution — in fact, 



