CaAP. II. OPHRTS APIFEEA. 57 



drawn out of its pouch a morement of depression 

 commences, by which the pollinium if attached to 

 the front of an insect's head would be brought into 

 a proper position for striking the stigma. When a 

 pollen-mass is placed on the stigma and then with- 

 drawn, the elastic threads by which the packets are 

 tied together break, and leave several packets on the 

 viscid surface. In all other Orchids the meaning of 

 these several contrivances is unmistakably clear — 

 namely, the downward movement of the lip of the ros- 

 tellum when gently pushed — the viscidity of the disc 

 — the depression of the caudicle as soon as the disc 

 is exposed to the air — ^the rupturing of the elastic 

 threads — and the conspicuousness of the flower. Are 

 we to believe that these adaptations for cross-fertilisa- 

 tion in the Bee Ophrys are absolutely purposeless, as 

 would certainly be the case if this species has always 

 been and will always be self-fertilised ? It is, however, 

 just possible that insects, although they have never 

 been seen to visit the flowers, may at rare intervals 

 transport the pollinia from plant to plant, during such 

 seasons as that of 1868, when the pollinia did not all 

 fall out of the anther- cells so as to reach the stigmas. 

 The whole case is perplexing in an unparalleled degree, 

 for we have in the same flower elaborate contrivances 

 for directly opposed objects. 



That cross-fertilisation is beneficial to most Orchids, 

 we may infer from the innumerable structures serving 

 for this purpose which they present ; and I have 

 elsewhere shown in the case of many other groups of 

 plants * that the benefits thus deiived are of high 

 importance. On the other hand, self-fertilisation is 

 manifestly advantageous in as far as it ensures a full 



* ' The Effects of Cross and Self-Fertilisation in the Vegetable 

 Kinmlom,' 1876. 



