158 VANDE.E. Chap. VI. 



manner shortened, it is hardly possible that the flower 

 could have been fertilised. After this movement, the 

 pollinium attached to any small object can be inserted 

 into the flower, and the balls of pollen readily adhere 

 to the stigmatic surface. Here we have an instance 

 of one of those compensating actions in the poUinia, 

 before alluded to, in relation to the shallowness of 

 the stigma. 



In some cases, besides hygrometric movements, 

 elasticity comes into play. In Aerides odorata and 

 virens, and in an Oncidium {roseum ?), the pedicel of 

 the rostellum is fastened down in a straight line, at 

 one extremity by the disc, and at the other by the 

 anther ; it has, however, a strong elastic tendency to 

 spring up at right angles to the disc. Consequently, 

 if the pollinium, attached by its viscid disc to some 

 object, is removed from the anther, the pedicel instantly 

 springs up and stands at nearly right angles to its 

 former position, with the pollen-masses carried aloft. 

 This has been noticed by other observers ; and I agree 

 with them that the object gained is to free the pollen- 

 masses from the anther-cells. After this upward elastic 

 spring, the downward hygrometric movement imme- 

 diately commences, which, oddly enough, carries the 

 pedicel back again into almost exactly the same 

 position, relatively to the disc, which it held whilst 

 forming part of the rostellum. In Aerides the end of 

 the pedicel, to which the pollen-masses are attached 

 by short dangling caudicles, after springing up, remains 

 a little curved upwards; and this curvature seems 

 well adapted to drop the pollen-masses into the deep 

 stigmatic cavity over the ledge in front. The differ- 

 ence between the first elastic and the second or re- 

 versed hygrometric movement, was well shown by 

 placing the pollinium of the above Oncidium into 



