Watch bees and other insects visiting buttercups and notice how they stand on the flower to obtain the nectar from the nectaries. Does a bee on leaving go to another buttercup, or does it change to another kind of flower?
In a flower from which the sepals, petals, and stamens have fallen, notice the compound fruit ([Fig. 66]), consisting of ripened carpels. Open a carpel with a needle and pick out the single seed.
2. Other plants of the buttercup family.—Notice that in the anemone ([Fig. 67]) and marsh marigold ([Fig. 68]), the sepals appear to be absent (the three leaves under the anemone flower are not parts of the flower; they are called bracts). The apparent petals are really the sepals; it is the corolla which is absent. Observe the large number of stamens, and notice that the pistil consists of several separate carpels.
In what kind of ground have you seen these plants growing wild?
Fig. 65.—Buttercup. (× ¹⁄₁₀.)
The buttercup family.—The buttercup ([Fig. 65]) and its relatives resemble the crucifers (1) in being dicotyledons (as is indicated ([p. 40]) by the venation of the leaves), and (2) in the fact that, of the parts which compose the flower, each group is arranged separately on the receptacle. For example, the stamens are not connected with either the calyx, the corolla or the pistil. Having noted these points of resemblance, however, we are met by some important differences. In the buttercup there are usually five sepals and five petals; there may be twenty or more stamens; and the pistil is not a single structure, but consists of a number of separate parts, each of which is called a carpel, and contains a single ovule. The pistil of a crucifer consists of only two carpels; these are welded together into a single structure, and until the fruit ripens a slight notch in the stigma is the only external indication that the pistil is in two parts.
