214 VANDExE. Chap. VII 



face of tlie rostellum. As the two pollen-masses 

 adhere, at first, rather firmly to the anther-case, the 

 latter is torn off by the rebound ; and as the thin 

 hinge at the summit of the anther-case does not yield 

 so easily as the basal margin, the pollinium together 

 with the anther-case is instantly swung upwards like a 

 pendulum. But in the course of the upward swing 

 the hinge yields, and the whole body is projected 

 perpendicularly up in the air, an inch or two above and 

 close in front of the terminal part of the labellum. If 

 no object is in the way, as the pollinium falls down, 

 it generally alights and sticks, though not firmly, on 

 the folded crest of the labellum, directly over the 

 column. I witnessed repeatedly all that has been 

 here described. 



The curtain of the disc, which, after the pollinium 

 has formed itself into a hoop, lies on the anther-ca^e, 

 is of considerable service in preventing the viscid edge 

 of the disc from adhering to the anther, and thus 

 permanently retaining the pollinium in the form of a 

 hoop. This would have been fatal, as we shall pre- 

 sently see, to a subsequent movement of the pollinium 

 which is necessary for the fertilisation of the flower. 

 In some of my experiments, when the free action 

 of the parts was checked, this did occur, and the 

 pollinium, together with the anther-case, remained 

 permanently glued together in the shape of an ir- 

 regular hoop. 



I have already stated that the minute hinge by 

 which the anther-case is articulated to the column, a 

 little w^ay beneath its bent filamentary apex, is sen- 

 sitive to a touch. I tried four times and found 

 that I could touch with some force any other part ; 

 but when I gently touched this point with the finest 

 needle, instantly the membrane which unites the disc 



