144 MISSOURI BOTANICAL GARDEN BULLETIN 
anthes, as previously stated, the lip is in the shape of a bucket 
and in Catasetum maculatum, the lip is hooded, whence its 
name monk’s hood orchid. In the latter species the lip is 
at the top of the flower and this is in reality its correct 
position. The usual placement of the labellum at the bot-— 
tom, as in Cattleya, is brought about by a twisting of the 
ovary in the early stages of development. 
Insects do not visit orchid flowers for the purpose of polli- 
nating them, but rather to collect the nectar which is stored 
in the glands or to feed upon the succulent petals and sepals. 
To effect an entrance into the flower, the visiting insect must 
traverse a rather definitely prescribed pathway, which is ar- 
ranged in such a manner that pollination is almost certainly | 
brought about by the visitor. The monk’s hood orchid 
shows perhaps the most remarkable adaptations for insect 
pollination. The staminate and pistillate flowers are pro- 
duced on separate individuals, the flowers being so different 
in shape that the two kinds of plants were at first erroneously 
described as separate species. No nectar glands are present 
in these flowers, the fleshy hood alone serving as an attrac- 
tion for certain gnawing insects. On the interior of the 
lip and situated near the posterior portion of the latter, are 
two sensitive antennae or “triggers,” which are indirectly 
connected to the pollen masses. The caudicle, which at- 
taches the latter to the viscid disc, fits over the slightly 
rounded rostellum. While feeding on the labellum, the 
insect is almost certain to come into contact with the 
“trigger,” thus causing the thin membranaceous caudicle to 
rupture spontaneously, thereby forcibly ejecting the two large 
pollen masses. The viscid disc adhering to the latter serves 
to attach the masses to the insect’s back. When an insect so 
charged with pollen visits a pistillate flower, the masses are 
brought into contact with the stigmatic surface and pollina- 
tion is effected. 
The slipper orchid belonging to the genus ripedium, 
differs from the preceding farm ti that it a fertile 
stamens instead of one. The insect readily enters through 
the large opening at the top of the slipper and feeds upon 
the nectar secreted at the base of the interior of the lip. 
When the visitor attempts to leave the flower, however, it 
finds it impossible to escape by the way it entered, because 
the inside of the slipper is so smooth that it cannot gain a 
foothold to reach the opening at the top. The only other 
possible place of escape is through two small openings above 
the stigmatic surface, send theme se be Wat Manchied te 
a pathway of hairs which furnish a sure footing for the 
