4.4.2 MR. R. ALLEN ROLFE ON THE GENUS VANILLA. 
known forms. Several, however, are still very imperfectly 
known, and it is greatly to be wished that those who have the 
opportunities would collect a series of flowering and fruiting 
specimens, which would materially assist in completing our 
knowledge of this very difficult genus. 
FERTILIZATION. 
Owing to their highly complex structure the flowers are 
incapable of self-fertilization, and in the case of V. planifolia, 
which is so largely cultivated as an economic plant, artificial 
fertilization is invariably practised, except in Mexico and 
Central America, where the species is indigenous. Here 
Deltiel records that the flowers are fertilized by bees of the 
genus Melipone, which visit the flowers for the honey they 
afford. I have not succeeded in finding any further records on 
the subject, and it would be interesting if this point could be 
cleared up. In other regions nothing whatever seems to be 
known of the insects which fertilize the flowers, although the 
genus is so widely diffused through the tropics. As regards 
V. planifolia it may be said that the flowers are fragrant, and 
that they secrete a large amount of honey at the bottom of the 
tube, which would naturally attract insects. The front lobe of 
the lip is reflexed and somewhat rough, and thus would afford 
a lighting place for the insect, which would then crawl into the 
tube to suck the honey. A small bee would easily get the 
front part of its body past the anther, because the appendages 
of the crest are all deflexed towards the base, but on retreating 
these would present an obstacle, and in order to pass them the 
bee would have to elevate its body, and thus would press 
against the incumbent anther and dislodge the pollinia. In 
what way these become attached to the insect in this case is 
perhaps not known, but it may be safely assumed that they do 
become so attached and are carried away. On retreating from the 
flower the bee would also lift up the flap-like rostelluam which 
protects the stigma, and thus any pollen would inevitably be 
deposited on the latter and fertilize the flower. In other 
species of the genus the structure is similar, so that it may 
safely be assumed that fertilization is effected in the same way. 
