138 “PE OWERING PLANTS 
pencil touches the rostellum, the pollinia adhere to it, and — 
when the pencil is withdrawn one or both pollinia may be 
seen on it. oe 
Each pollinium consists of a stalk, 
which bears the pollen masses, and at 
_ the opposite end it terminates in a disc, 
which fits into the rostellum. 
The remaining stamens are suppressed ; 
their position is indicated in the floral 
diagram. Judging from other Mono- 
Fic. 133,Portria COtyledonous Orders, the “number of 
or ORCHIS. stamens would be 6, and Darwin has 
c, stalk ; d, disc; p, shown clearly that there are traces of 6 
pollen grams forming in the Orchid (Fig. 134). | 
The gynecium consists of 3. carpels, 
with 3 parietal placentz; the ovary is twisted, and it is this 
that makes the true posterior side of the flower appear to be 
anterior. The style unites with the stamen, as mentioned 
above; 2 stigmatic surfaces are easily seen just beneath and 
on each side of the anther ; whilst 
it is considered that the rostellum, 
into which the discs of the pollinia 
fit, is a modified stigma. 
The fruit is a capsule, dehiscing 
by 3 valves; the seeds are small 
and light, and scattered by the 
wind. | 
In the floral diagram (Fig. 134) 
it must be noticed that the parts 
of the flower are represented in 
their true positions, the labellum on the posterior side, the 
single stamen on the anterior, ete. ° 
eae The labellum serves as a landing-place for the 
Pollination. . , : 
insect, which pushes its head into the chamber 
leading to the nectary. Projecting into this chamber is the 
rostellum, which must therefore be touched by the insect. As 
the insect touches the rostellum its outer membrane is rup- 


Fic. 134.-—FLorRAL DIAGRAM 
OF ORCHIS. 
