=815. The carpels are often united.=—The pistil is then said to be _compound_. Where the pistils are consolidated, usually the adjacent walls coalesce and thus separate the cavity of each ovary. Each cavity in the compound pistil is a _locule_. In some cases the adjacent walls disappear so that there is one common cavity for the compound pistil (examples: purslane, chickweeds, pinks, etc.). In a few cases there is a false partition (example, in the toothwort and other crucifers). The compound pistil is very often lobed slightly, so that the different pistils can be discerned. More often the styles or stigmas are distinct, and thus indicate the number of pistils united. =816. Union of the parts of different series.=—While in the buttercup and many other flowers, all the different parts are inserted on the torus or receptacle, in other flowers one series of parts may be joined to another. This is _adnation_ of parts, or the two or more series are _adnate_. In the morning glory the stamens are inserted on the inner face of the corolla tube; the same is true in the mint family, and there are many other examples. The insertion of parts, whether free or adnate, is usually spoken of in reference to their relation to the pistil. Thus, in the buttercup the floral envelopes and stamens are all free and _hypogynous_, they are _below_ the pistil. The pistil in this case is _superior_. In the cherry, pear, etc., the petals and stamens are borne on the edge of the more or less elevated tube of the calyx, and are said to be _perigynous_, i.e., around the pistil. In the cranberry, huckleberry, etc., the calyx is for the most part united with the wall of the ovary with the short calyx limbs projecting from the upper surface. The petals and stamens are inserted on the edge of the calyx above the ovary; they are, therefore, _epigynous_, and the ovary being under the calyx, as it were, is _inferior_. III. Arrangement of Flowers, or Mode of Inflorescence. =817. Flowers are solitary or clustered.=—_Solitary flowers_ are more simple in their arrangement, i.e., it is easier for us to determine and name their relation to each other and to other parts of the plant. They are either _axillary_, i.e., on short lateral shoots in the axils of ordinary foliage leaves, or they are _terminal_, i.e., they are borne on the end of the main axis of an ordinary foliage shoot. In either case they are so far separated, and the foliage leaves are so prominent, they do not form recognizable groups or clusters. The manner of arrangement of flowers on the shoot is called _inflorescence_, while the group of flowers so arranged is the _flower cluster_.