210 VANDEiE. Chap. VII. 



right or left, according to the position of the flower 

 on the spike. The twisted stigmatic surface extends 

 down to the base of the column and is hollowed out 

 into a deep cavity at its upper end. The large viscid 

 disc of the pollinium is lodged in this cavity close be- 

 neath the rostellum ; and the rostellum is seen in the 

 drawing (2^d.) covered by the bowed pedicel. 



The anther-case (a in the figure) is elongated and 

 triangular, closely resembling that of Catasetum ; but 

 it does not extend up to the apex of the column. The 

 apex consists of a thin flattened filament, which from 

 the analogy of Catasetum I suppose to be the produced 

 filament of the stamen ; but it may be a prolongation 

 of some other element of the column. In the bud- 

 state it is straight, but before the flower expands, it 

 becomes much bent by the pressure of the labellum. 

 A group of spiral vessels runs up the column as far as 

 the summit of the anther-case ; they are then reflexed 

 and run some way down the anther-case. The point 

 of reflexion forms a short thin hinge by which the top 

 of the anther-case is articulated to the column beneath 

 its bent summit. The hinge, although smaller than a 

 pin's head in size, is of paramount importance ; for it 

 is sensitive and conveys the stimulus from a touch to 

 the disc of the pollinium, causing it to separate from 

 its place of attachment. The hinge also serves to 

 guide the pollinium during its ejection. As it has 

 to convey the necessary stimulus to the disc, one may 

 suspect that a portion of the rostellum, which lies in 

 close contact with the filament of the anther, runs up 

 to this point ; but I could not here detect any differ- 

 ence in structure on comparing these parts with those 

 of Catasetum. The cellular tissue round the hinge 

 is gorged with fluid, and a large drop exudes when 

 the anther is torn from the column during the ejection 



