FERTILIZATION IN PLANTS. 
427 
iabellum is shown (1) with the opening' to the nectary. All the 
reproductive organs are combined together into one com- 
pound organ^ which is the column already referred to. The 
stigma is seated beneath a projection of the column_, and con- 
sists of two nearly confluent stigmas (fig. s), the surface of 
which is soft and viscid. The projection above this is a curious 
adaptation of the upper portion of the column^ and is named 
the rostellum (fig. 1, r), which supports the pollen masses. 
Here_, again^ a vast difference occurs between Orchids and 
other plants. In most flowers the pollen consists of a fine 
powder^ but in Orchids the grains cohere in masses; often 
borne upon a stalk or appendage, called the cauclicle. The 
pollen-masses, with their appendages of all kinds, are known 
as ijollinia. In the present species the anther (figs. 1 and 2 a) 
consists of two cells, separated from each other, each containing 
a pollen-mass. One of these pollinia removed from its cell, is 
shown at fig. 3, where is the pollen-mass ; c the caudicle or 
appendage ; and d a viscid disc, to which the caudicle is firmly 
attached. Each pollinium has a similar disc, which is imbedded 
within the rostellum, as shown at fig. 4. A section through 
one of these discs, and the rostellum in which it is imbedded, 
would present the appearance of fig. 5. The two discs, at the 
base of the caudicles of the two pollen-masses, lie quite un- 
attached within the cup of the rostellum, surrounded by fluid, 
except at the back, where the discs are each at first firmly 
adherent to a small portion of the membrane of the rostellum. 
How are these pollen-masses to be transferred to the viscid 
stigma lying beneath the projecting rostellum, and thus the 
ovules become fertilized ? To answer this question was one of 
the aims of Mr.Darwin^s work, and to explain it so satisfactorily 
as he has done, gives evidence of no small earnestness and 
perseverance, through years of close observation. Let us 
accept the Iabellum, or lower petal of the flower, as the landing 
place of an insect. The bee or butterfly alighting on this 
platform, thrusts its head into the chamber or cavity, at the 
back of which lies the stigma, in order to push its proboscis 
down into the nectary. As the rostellum projects above, it is 
almost impossible for the head of the insect to enter without 
touching the rostellum ; as it is pushed further, the lip is de- 
pressed, and one or both of the viscid discs at the base of the 
pollinia is sure to become attached to the head of the insect ; as 
this is withdrawn it bears with it one or both of the viscid discs 
attached to its forehead, together with their caudicles and pollen- 
masses. Let a pencil or any other object supply the place of 
the insect, and be thrust in at the mouth of the Orchis, in the 
direction of the nectary, and it will be found scarce possible 
to insert it without touching and bending down the lip of the 
