Orchids 309 
The White Helleborine (Cephalanthera pollens), as 
indicated, is similar to Hpipactis, except that there 
is no rostellum. The petals and sepals have their 
margins curled inwards, and the lip is constricted in 
the middle, dividing it into a basin-like basal portion 
and a terminal yellow lobe, which at first folds 
upwards and closes the entrance to the flower. Some 
of the pollen-grains adjacent to the edge of the stigma 
throw out their shoots and partially self-fertilise the 
seed-eggs. Darwin was of opinion that the principal 
object of this is to retain the pollen until insects 
arrive, to which the grains adhere, and by which the 
flowers can alone be perfectly fertilised. 
The very rare Lady’s Slipper (Cypripedium 
calceolus) must be my last example of the British 
Orchids ; and this shows 
considerable variation 
from the structure and 
mechanism of the other 
species. The sepals and 
petals are long and 
slender, and they spread = 
widely apart. The lip 
is developed into a large 
bag the edges of whose 
mouth turn inwards. 
In all the other species 
I have mentioned a ‘ys Slipper 
single anther usually 
bears two pollen masses. The fundamental plan 
of all Orchid flowers suggests three stamens, but 
usually two are aborted and the third developed. 
Now, in Cypripedium the usually aborted anthers are 
