OPHRYDE^—SERAPIADIN^-OPHRYS 239 



S^ Devon (J.B. p. 248 (1882)). Forms varying towards Tro/Zh' occur at Salisbury! 



Winchester! and Reigate. 



Fertilisation. The flowers of the Bee Orchid were primarily designed for cross- 

 pollmation by insects, the mechanism for the transport of the pollinia being exactly 

 similar to that of all other species of Opbrys wholly dependent on insects for pol- 

 Imation. ^ 



Nevertheless self-pollination is the rule. The pollinia emerge from the anther-cells 

 (their viscid discs, however, remaining m situ in the two pouches), and dangle on 

 their long thread-like flexible caudicles just in front of the stigma. According to 

 Darwm this takes place in the course of a few hours. The slightest breath of air makes 

 them oscillate, till they touch the stigma, and are caught and held by its viscid 

 secretion. He found that the poUinia of a spike in a still room remained free 

 suspended in front of the stigma, till the flowers withered, and said, "it can hardly 

 be doubted that O. apijera was at first constructed to be regularly cross-fertilised" ' 



Robert Brown was the first to observe that the Bee Ophrys is capable of self- 

 fertflisation, and erroneously believed that this peculiarity was common to the genus 

 Darwm pointed out that even now the poUinia can be withdrawn on a pencil in the 

 same way as those of other species of the genus (sometimes even after they have 

 adhered to the stigma) and also go through the same motion of depression tiU they 

 assume the exact position for touching the stigma of another flower. If the pencil 

 be then mserted into another flower, several packets of pollen adhere to the stigma 

 and the elastic threads fastening them to the poUinia break, leaving them on its viscid 

 surface. The mechamsm for the transport of the pollen is thus still in good working 

 order. No wonder that Darwin was surprised that none of its parts showed any 

 tendency to abortion, m spite of their uselessness to a self-fertilising plant He how- 

 ever, overstated the case when he said that 0. apijera has "almost certainly been 

 propagated m a state of nature for thousands of generations without having been 

 once intercrossed ".2 



That cross-fertilisation actually occurs in nature at the present day is proved by 

 the fact that natural hybrids have been found between O. apifera on the one hand 

 and O. arachnites (PL 56), aranijera, litigiosa and scokpax respectively, on the other 

 These could not possibly have arisen without the effectual visit of the same individual 

 insect to both the parents concerned. For one such visit to two different species 

 of Ophrys m succession, there must be very many more in which the insect confines 

 Itself solely to 0. apifera in conformity with the usual habit of bees. Darwins states 

 that out of 106 flowers gathered in Surrey three had lost one poliinium, and that out 

 of 136 flowers in the Isle of Wight 10 had lost both pollinia and 14 had lost one. 



3 Sr:s g;;: gs it i: in. - ^^--' ^— -^^^^/z/-/^--. p. 439. 



