PERAMIUM 113 



sepals at the side spread out widely, but the third and upper 

 one is united with the petals to form a hood. The lip is 

 rounded without being notched, and curves up into a little 

 sac with outspread edges that give a visiting insect a thresh- 

 old to stand upon. 



By cutting a blossom through longitudinally, as Mr. 

 Gibson has done in his sketch, one can follow the steps by 

 which the insects forces its way in, and becomes fertilised 

 with pollen. 



The column, that is, the combination of stigma and 

 anther, is peculiarly constructed. 



The stigma has a sticky minutely toothed surface (Plate 

 XLIV., Fig. 4). The incurved lip, with its reflexed edges, 

 almost closes the throat of the flower (Figs, i, 2 and 3). Above 

 the stigma the column projects up into a little arm that holds 

 the anther, and out on either side like wings. This places 

 the anther in such a position that there is a little cup-shaped 

 cavity behind it. Under the broad anther lie two pollen 

 masses, united at their base to a common viscid gland 

 (Figs. 3, 4). The back or upper surface of this anther, called 

 the rostellum, comes off easily like a shield, and to it adhere 

 the pollen masses. The pollen grains cohere in little packets 

 (Fig. 5), as in orchis, and these packets are tied together 

 by strong elastic threads, which, under a powerful micro- 

 scope, may be made out — at first individually and then 

 running together into a single brown elastic ribbon, by which 

 the pollen masses are fastened to the shield or removable 

 portion of the rostellum. 



