[Illustration: Fig. 468. Section of flower of cypripedium. _st_, stigma; _a_, at the left stamen. The insect enters the labellum at the center, passes under and against the stigma, and out through the opening _b_, where it rubs against the pollen. In passing through another flower this pollen is rubbed off on the stigma.] =862.= If we open carefully canna flower buds which are nearly ready to open naturally, by unwrapping the folded petals and staminodia, we shall see the anther-bearing staminodium is so wrapped around the flattened style that the anther lies closely pressed against the face of the style, near the margin _opposite that on which the stigma lies_. [Illustration: Fig. 469. Epipactis with portion of perianth removed to show details. _l_, labellum; _st_, stigma; _r_, rostellum; _p_, pollinium. When the insect approaches the flower its head strikes the disk of the pollinium and pulls the pollinium out. At this time the pollinium stands up out of the way of the stigma. By the time the insect moves to another flower the pollinia have moved downward so that they are in position to strike the stigma and leave the pollen. At the right is the head of a bee, with two pollinia (_a_) attached.] [Illustration: Fig. 470. Canna flowers with the perianth removed to show the depositing of the pollen on the style by the stamen.] =863.= The walls of the anther locules which lie against the style become changed to a sticky substance for their entire length, so that they cling firmly to the surface of the style and also to the mass of pollen within the locules. The result is that when the flower opens, and this staminodium unwraps itself from the embrace of the style, the mass of pollen is left there deposited, while the empty anther is turned around to one side. =668.= Why does the flower deposit its own pollen on the style? Some have regarded this as the act of pollination, and have concluded, therefore, that cannas are necessarily self pollinated, and that cross pollination does not take place. But why is there such evident care to deposit the pollen on the side of the style away from the stigmatic margin? If we visit the cannas some morning, when a number of the flowers have just opened, and the bumblebees are humming around seeking for nectar, we may be able to unlock the secret.