

NATURAL GRDERS © Ca 
tured, and the dises of the pollinia, which fit into the pouch 
of the rostellum, being sticky, adhere to the insect’s proboscis, 
and are carried to another flower. When the pollinia are 
first removed from the anther they are erect on the proboscis, 
but in.the course of thirty seconds they fall through an angle 
of 90 degrees ; so that by the time the insect reaches a second 
flower they are hanging down, and are in such a position as to 
come in contact with the stigmatic surfaces on each side of the 
rostellum, and thus the second flower is cross-pollinated. 
Were it not for this contrivance, the pollinia would merely. 
touch the anther of the fresh flower, and would not cross- 
pollinate it at all. There is another provision of Nature. 
that should be noticed: the stigmatic surfaces are sticky or 
viscid, but only sufficiently so to break the elastic threads 
which hold the pollen grains together; if they were more 
sticky, the whole pollinium would be pulled off from the 
insect; but as it is, only a-few grains are taken by each 
flower, so that one pollinium can cross-pollinate several 
flowers. | 
Darwin found that the majority of Orchids were cross- 
pollinated; the Bee Orchid, however, pollinates itself. The 
chief points of difference in the structure of this species are : 
The anther opens of itself as soon as the flower is fully 
expanded, and does not require any pressure on the rostellum — 
to liberate the pollinia ; then owing to the stalks being very 
slender and flexible, when the pollen masses fall out on the 
opening of the anther, the stalks hang freely in the air, and 
the pollen masses are in a position to strike the stigma. 
Darwin covered up a Bee Orchid with a net, in order to pre- 
vent insects getting to the plant, and was able to watch the 
exact movements of the pollinia. These differences in struc- 
ture account for the fact that the Bee Orchid pollinates 
itself. | 
The largest British genus is Orchis, which in- 
cludes several species, such as Early Purple, : 
Spotted, Pyramidal, Marsh, etc. ‘They’all have a spur. 
The genus Habenaria, which includes, among others, the 
Genera. 
