12 OPHRE^. Chap. I. 



it is scarcely possible that any object can be pushed 

 into it without the rostellum being touched. The ex- 

 terior membrane of the rostellum then ruptures in the 

 proper lines, and the lip or pouch is easily depressed. 

 When this is effected, one or both of the viscid balls 

 will almost infallibly touch the intruding body. So 

 viscid are these balls that whatever they touch they 

 firmly stick to. Moreover the viscid matter has 

 the peculiar chemical quality of setting, like a 

 cement, hard and dry in a few minutes' time. As the 

 anther-cells are open in front, when the insect with- 

 draws its head, or when the pencil is withdrawn, one 

 pollinium, or both, will be withdrawn, firmly cemented 

 to the object, projecting up like horns, as shown (fig. 2) 



Fiff. 2. 



A. Pollen-mass of 0. mascula, when I B. Pollen-mass of 0. mascula, after 

 first attached. | the act of depression. 



by the upper figure, A. The firmness of the attach- 

 ment of the cement is very necessary, for if the 

 pollinia were to fall sideways or backwards they could 

 never fertilise the flower. From the position in 

 which the two pollinia lie in their cells, they diverge a 

 little when attached to any object. Now suppose that 

 the insect flies to another flower, or let us insert the 

 pencil (A, fig. 2), with the attached pollinium, into 



