CuiV. VI. ACKOPEKA, AND SOME ALLIED GENEEA. 167 



any other such case, not that I fully understand the 

 contrivances in any Orchid, for new and admirable 

 ones become apparent, the longer I study even one of 

 our commonest British species. 



The thin and elongated rostellum of Acr opera projects 

 at right angles to the column (see diagram, fig. 23, p. 

 150) ; and the pedicel of the poUinium is of course 

 equally long and much thinner. The disc consists of 

 an extremely small cap, viscid within, which fits on 

 the extremity of the rostellum. The viscid matter 

 sets hard but slowly. The upper sepal forms a hood 

 enclosing and protecting the column. The labellum 

 is an extraordinary organ, baffling all description : it 

 is articulated to the column by a thin strap, so elastic 

 and flexible that a breath of wind sets it vibrating. 

 It hangs downwards ; and the retention of this posi- 

 tion seems to be of importance, for the footstalk (ova- 

 rium) of each flower is curved into a semicircle,- so 

 as to compensate for the pendulous habit of the plant. 

 The two upper petals and the lateral lobes of the 

 labellum serve as guides leading into the hood-like 

 upper sepal. 



The poUinium, when adhering by its disc to an 

 object, undergoes the common movement of depression ; 

 and this seems superfluous, for the stigmatic cavity lies 

 (see diagram, fig. 23) high up at the base of the rect- 

 angularly projecting rostellum. But this is a com- 

 paratively trifling difficulty ; the real difficulty lies in 

 the orifice of the stigmatic chamber being so narrow 

 that the pollen-masses, though consisting of thin sheets, 

 can hardly be forced in. I repeatedly tried, and suc- 

 ceeded only three or four times. Even after leaving 

 them to dry for four hours before a fire, and thus to 

 shrink a little, I rarely succeeded in forcing them 

 into the stigma. I examined quite young flowers and 



