140 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 Ophrydez, as well as in many Neottez 
and Arethusez. 
But even in Ophrydez 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, 
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