538 ON THE OUGANS AND MODE 0¥ FECUNDATION 



My first observation on Bonatea related to the probability 

 of a single insect impregnating several or even many 

 flowers with one and the same mass of pollen. 



To effect this, it is only necessary that the viscidity of 

 the retinaculum or gland with which the pollen mass 

 becomes inseparably connected, and by means of which 

 the mass is removed from its cell and adheres to the insect, 

 should exceed that of the surface of the stigma, and that 

 the viscidity of the stigma should be sufficient to overcome 

 the mutual cohesion of the lobules composing the mass. 



These different degrees of viscidity are very manifest in 

 Bonatea speciosa, in which, imitating the supposed action 

 of the insect, I have succeeded in impregnating most of the 

 flowers of the spike with a single pollen mass. I believe 

 they exist also in the greater number of Ophrydese, as well 

 as in many Neottese and Arethusese. 



But even in Ophrydese they are not universally met 

 with, a very remarkable exception existing, I believe, in 

 the whole genus Ophrys, in which the resemblance of the 

 flower to an insect is so striking, and in which also the 

 retinacula, whose viscidity hardly equals that of the stigma, 

 are included and protected by concave processes of the 

 upper lip of tliat organ. 



It may also be remarked, that in the genus Ophrys im- 

 pregnation is frequently accomplished without the aid of 

 insects, and in general the whole pollen mass is found 

 adhering to the impregnated stigma. Hence it may be 

 conjectured, that the remarkable forms of the flowers in 

 this genus are intended to deter not to attract insects, 

 741] whose assistance seems to be unnecessary, and the action 

 of which, from the diminished vicidity of the retinaculum, 

 might be injurious. On this subject I will also hazard 

 another remark, that the insect forms in Orchideous 

 flowers, resemble those of the insects belonging to the 

 native country of the plants. 



The next object I had in view was to determine the first 

 appearance and progress of the mucous tubes. 



My observations on the origin of these tubes are not 

 altogether satisfactory. 



