=864.= We see that in a recently opened canna flower, the petal which directly faces the style in front stands upward quite close to it, so that the flower now is somewhat funnel-shaped. This front petal is the _labellum_, and is the landing place for the bumblebee as he alights on the flower. Here he comes humming along and alights on the labellum with his head so close to the style that it touches it. But just the instant that the bee attempts to crowd down in the flower the labellum suddenly bends downward, as shown in fig. 468. In so doing the head of the bumblebee scrapes against the pollen, bearing some of it off. Now while the bee is sipping the nectar it is too far below the stigma to deposit any pollen on the latter. When the bumblebee flies to another newly opened flower, as it alights, some of the pollen of the former flower is brushed on the stigma. =865.= One can easily demonstrate the sensitiveness of the labellum of recently opened canna flowers, if the labellum has not already moved down in response to some stimulus. Take a lead-pencil, or a knife blade, or even the finger, and touch the upper surface of the labellum by thrusting it between the latter and the style. The labellum curves quickly downward. =866.= Sometimes the bumblebees, after sipping the nectar, will crawl up over the style in a blundering manner. In this way the flower may be pollinated with its own pollen, which is equivalent to self pollination. Undoubtedly self pollination does take place often in flowers which are adapted, to a greater or less degree, for cross pollination by insects. [Illustration: Fig. 471. Pollination of the canna flower by bumblebee.] [Illustration: Canna flower. Pollen on style, stamen at left.] CHAPTER XLIV. THE FRUIT. I. Parts of the Fruit. =867. After the flower comes the fruit.=—With the perfection of the fruit the seed is usually formed. This is the end towards which the energies of the plant have been directed. While the seed consists only of the ripened ovule and the contained embryo, the fruit consists of the ripened ovary in addition, and in many cases with other accessory parts, as calyx, receptacle, etc., combined with it. The wall of the ripened ovary is called a _pericarp_, and the walls of the ovary form the walls of the fruit. =868. Pericarp, endocarp, exocarp, etc.=—This is the part of the fruit which envelops the seed and may consist of the carpels alone, or of the carpels and the adherent part of the receptacle, or calyx. In many fruits the pericarp shows a differentiation into layers, or zones of tissue, as in the cherry, peach, plum, etc. The outer, which is here soft and fleshy, is _exocarp_, while the inner, which is hard, is the _endocarp_. An intermediate layer is sometimes recognized and is called _mesocarp_. In such cases the skin of the fruit is recognized as the _epicarp_. Epicarp and mesocarp are more often taken together as exocarp.