740 Mr. Brown on the Organs and Mode of 



My observations on this point and on the gradual production 

 and descent of these cords have been made chiefly on Bonatea 

 speciosa, perhaps the most favourable subject for such experi- 

 ments in the whole family. 



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 inse- 

 parably 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 Bo- 

 natea 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 Ophrydeae, as well as in many Neottese 

 and Arethuseae. 



But even in Ophrydeae 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 that organ. 



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

 nation 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, whose assistance seems to be unne- 

 cessary, 



