Chap. VI. STEUCTUEE OF COLUMN. ] 51 



tion, at first appearing as a zone of hyaline tissue, is 

 gradually formed, which sets free the disc, as well as 

 the whole upper surface of the rostellum, as far back 

 as the point of attachment of the caudicles. If any 

 object now touches the viscid disc, it, together with 

 the whole back of the rostellum, the caudicles and 

 pollen-masses, can all be readily removed together. 

 In botanical works the whole structure between the 

 disc or viscid surface (generally called the gland) and 

 the balls of pollen is designated as the caudicle ; but 

 as these parts play an essential part in the fertilisation 

 of the flower, and as they are fundamentally different 

 in their origin and in their minute structure, I shall 

 call the two elastic ropes, which are developed strictly 

 within the anther-cells, the caudicles ; and the portion 

 of the rostellum to which the caudicles are attached 

 (see diagram), and which is not viscid, the pedicel. 

 The viscid portion of the rostellum I shall call, as 

 heretofore, the viscid surface or disc. The whole may 

 be conveniently spoken of as the poUinium. 



In the Ophrese we have (except in 0. pyramidalis 

 and a few other species), two separate viscid discs. In 

 the Vandeee, with the exception of Angrsecum, we have 

 only one disc. The disc is naked, or is not enclosed 

 in a pouch. In Habenaria the discs, as we have seen, 

 are separated from the two caudicles by short drum- 

 like pedicels, answering to the single and generally 

 much more largely developed pedicel in the Vandese. 

 In the Ophreae the caudicles of the pollinia, though 

 elastic, are rigid, and serve to place the packets of 

 pollen at the right distance from the insect's head or 

 proboscis, so as to reach the stigma. In the Vandese 

 this end is gained by the pedicel of the rostellum. 

 The two caudicles in the Vandese are embedded and 

 attached within a deep cleft in the pollen-masses. 



