Fertilization of Flowering Plants. 191 
the bee may have brought from another flower is deposited on the 
small lip of the stigma, which then closes, so that pollen from its 
own flower is prevented from entering when the bee withdraws 
its proboscis. 
Some of the Papilionacez, such as the bird’s-foot trefoil, have 
a kind of piston-apparatus. The free end of the keel forms a 
hollow cone, open at the apex, and closed by the dilated ends of 
the stamens. When the keel is depressed by a bee alighting 
upon the flower, the stamens, being fixed, are forced further into 
the conical cavity, and expel some of the pollen through the 
orifice on to the under side of the bee, and is again deposited on 
the stigma of an older flower. In the broom the same effect 
ced with explosive effect when the flower is visited by 
a bee. 
In Salvia there is a remarkable modification of the stamens. 
Here the two anthers are separated from each other by a very 
long connective articulated to a firm erect filament so as to form 
a lever. When a bee enters the flower it pushes against the 
short arms of the lever, so that the long upper arms fall and 
deposit the pollen on the middle of the bee’s back. And here let 
me mention that bees generally visit the lowest flowers on a 
plant first. In the case of Salvia these are first developed, so 
that the styles in the uppermost flowers are not in a receptive 
condition as early as the lower; consequently the bee will 
remove the pollen from the last visited flower of one plant to 
the lower flower of another where the style occupies such a 
position as to come into contact with the bee’s back, and so 
becomes fertilized. 
The stigmas of Mimulus exhibit sensitive movements. When 
the pollen is deposited by an insect on the lower lip of the 
stigma, which stands in its way when it enters, the two lips 
immediately close together like the leaves of a book. When the 
insect withdraws its proboscis there is no chance of the pollen, 
which it is taking from the anthers, getting into the interior of 
the stigma, since the stigma is still shut up, and no longer 
stands in the way of the insect. 
The orchids exhibit great variety in their arrangements for 
promoting the access of insects. 
In Phalenopsis the smooth labellum has a little projection 
which serves as a footstool to the visiting flies. Behind the 
footstool is the column, the apex of which is occupied by the 
anther, and whose lower portion is excavated into a stigmatic 
cavity. Leading into this honey-lined cavity is a circular aper- 
ture or window, and projecting into the upper margin of this 
window is the little pointed rostellum. When a fly desires to 
abstract honey from the stigmatic cavity it stands on the foot- 
stool and puts its head in at the window. In doing so it touches 
c 2 
