BATH FLORA, FERTILISATION, ETC. 225 



proboscis, or pencil, in the course, on an average, of 30 seconds. 

 The position of the pollinium after the movement is shown at 

 Figs. 4 and 5. Now after this movement and interval of time 

 (which would allow the insect to fly to another flower), it will be 

 seen by turning to the diagrams (Figs. 4 and 5) that if the pencil 

 be inserted into the nectary, the thick end of the pollinium will 

 exactly strike the stigmatic surface. 



Here again comes into play another pretty adaptation, long 

 ago noticed by Robert Brown. The stigma is very viscid, but not 

 so viscid as, when touched, to pull the whole pollinium off the 

 insect's head or off the pencil, yet sufficiently viscid to break the 

 elastic threads (Figs, i and 2), by which the packets of pollen, 

 grain are tied together and leave some of them on the stigma. 

 Hence a pollinium attached to an insect can be applied to many 

 stigmas and will fertilise all. Mr. Darwin relates that he has 

 seen the poUinia of Orchis pyramidalis adhering to the proboscis 

 of a moth, the stump-like caudicle alone remaining, all the packets 

 of pollen having been left glued to the stigmas of the flowers suc- 

 cessively visited. This description of the action of the organs in 

 O. masada applies to O. vio?'io and O. niaadata. These three 

 species present slight differences in the length of the caudicle, in 

 the direction of the nectary, and in the shape and position of the 

 stigma, but they are not worth detailing. The pollinia in O. 

 morio undergo after removal from the anther-cells the same 

 peculiar movement of depression as in O. viasaila. 



Ophrys viuscifera^ the Fly Ophrys. — The Ophrecv. differ from 

 Orchis mainly in having two separate pouch-formed rostellums, 

 instead of the two being confluent as in Orchis. This, as Mr. 

 Darwin observes, is not a strictly accurate description, but it may 

 be forgiven on account of its convenience. In the Fly Ophrys 

 (O. 1/iuscifera) the chief peculiarity is that the caudicle of the 

 pollinium (^, Fig. 13) is doubly and almost rectangularly bent. 

 The nearly circular piece of membrane, to the under side of 

 which the ball of viscid matter is attached, is of considerable 

 size, and plainly forms the summit of the rostellum, instead of 

 forming, as in Orchis, the posterior and upper surface ; conse- 

 quently the attached end of the caudicle, after the flower has 

 expanded, is exposed to the air. As might have been expected 



