Chap. VI. SHAPE OF THE POLLINIA. 153 



for instance, in Phalfenopsis and Saccolabium, yet when 

 I inserted their pollinia attached to a rough object into 

 the stigmatic chamber, they did not adhere with suffi- 

 cient force to prevent their removal from the object. I 

 even left them for some little time in contact with the 

 adhesive surface, as an insect would do whilst feeding ; 

 but when I pulled the pollinia straight out of the 

 stigmatic chamber, the caudicles, though they were 

 stretched to a great length, did not rupture, nor did 

 their attachment to the object yield so that the balls 

 of pollen were withdrawn. It then occurred to me 

 that an insect in flying away would not pull the 

 pollinia straight out of the chamber, but would pull 

 at nearly right angles to its orifice. Accordingly I 

 imitated the action of a retreatins; insect, and drajr^ed 

 the pollinia out of the stigmatic chamber at right 

 angles to its orifice ; and now the friction on the 

 aaudicles thus caused, together with the adhesiveness 

 of the stigmatic surface, generally sufficed to rupture 

 them ; the pollen-masses being left on the stigma. 

 Thus, it seems that the great strength and extensi- 

 bility of the caudicles, which, until stretched, lie em- 

 bedded within the pollen-masses, serve to protect the 

 pollen-masses from being accidentally lost by an insect 

 whilst flying about, and yet, by friction being brought 

 into play, allow them at the proper time, to be left 

 adhering to the stigmatic surface ; the fertilisation ol 

 the flower being thus safely effected. 



The discs and pedicels of the pollinia present great 

 diversities in shape, and an apparently exhaustless 

 number of adaptations. Even in species of the same 

 genus, as in Oncidium, these parts differ greatly. I 

 here give a few figures (fig. 24), taken almost at hazard. 

 The pedicel generally consists, as far as I have seen, 

 of a thin ribbon-shaped membrane (fig. A) ; sometimes 



