76 OPHEEJi;. Chap. II. 



Professor Gray has seen a butterfly (Nisoniades) from 

 Canada with a pollinium of this species attached to 

 each eye. In the case of P. flava, moths are compelled 

 in a different manner to enter the nectary on one side. 

 A narrow but strong protuberance, rising from the base 

 of the labellum, projects upwards and backwards, so 

 as almost to touch the column ; thus the moth, being 

 forced to go to either side, is almost sure to withdraw 

 one of the viscid discs. P. hyperborea and dilatata 

 have been regarded by some botanists as varieties of 

 the same species; and Professor Asa Gray says that 

 he was formerly tempted to come to the same con- 

 clusion; but on closer examination he finds, besides 

 other characters, a remarkable physiological difference, 

 namely, that P. dilatata, like its congeners, requires 

 insect aid and cannot fertilise itself; whilst in P. 

 hyperborea the pollen-masses commonly fall out of the 

 anther-cells whilst the flower is very young or in bud, 

 and thus the stigma is self-fertilised. Nevertheless, the 

 various structures adapted for crossing are still present.* 

 The genus Bonatea is closely allied to Habenaria, 

 and includes plants having an extraordinary structure. 

 Bonatea speciosa is an inhabitant of the Cape of Good 

 Hope, and has been carefully described by Mr. Trimen ;t 

 but it is impossible to explain its structure without 

 drawings. It is remarkable from the manner in which 

 the two stigmatic surfaces, as well as the two viscid 

 discs, project far out in front of the flower, and from 

 the complex nature of the labellum, which consists of 

 seven, or probably of nine distinct parts all fused 



* Ml'. J. Mansel Weale has de- pnllinia not undergoing any move- 



scribed ('Journ. Lin. Soo. Bot.' ment or change of position when 



vol. xiii. 1871, p. 47) the method of removed from their cases, 



fertilisation of two South African f ' Journ. Linn. Soc. Bot.' voL 



(fpeoies of Habenaria : one ot ix. 1865, p. 156. 

 these is remarkable fiom the 



