After this long digression, we return to our Evening Primrose. Its large yellow flowers are disposed in clusters at the top of a stem often twenty inches long. The Pythagorean tetrad (_i.e._, the number 4 and its double) predominates in all its organs: 4 stigmata crowning a filiform stylus; quadrangular capsule with 4 polyspermous lobes; opening at top by the separation of 4 valves; twice 4 stamens; 4 petals on a large, emarginated limb; 4 sepals. These are united at the base, but not so as to prevent the observer from distinguishing their number. The general terms "regular" and "irregular," applied to the calyx, as to every other organ, require to be employed with considerable reserve. The delicate shades, which ought to separate regularity from irregularity, are often so inappreciable that it is almost impossible to say where one begins and the other ends. See, for example, the Labiatæ. In most genera and species of this family, the two lips, one of which consists of two and the other of three foliola, bring out very completely the inequality of the calyx. But there are also Labiatæ, the inequality of whose sepals completely effaces the character of the irregular bilabiated calyx. In certain inflorescences, where the flowers comprising them are very close together, as, for example, in the capitules of the Synantheraceæ, the free upper portions of the calyx may take the most irregular forms; as, sometimes, a tuft, simple or feathery; sometimes, membranous or scarious spangles; and, sometimes, bristles of greater or less stiffness. What elements of the calyx do these transformations represent? The veins, and notably the midrib of the limb of the sepals, united underneath. The free foliola of the _polyphyllous_ calyx may vary in form, like the caulinary leaves whence they issue by way of metamorphosis; they may be oval, elliptical, linear, &c. Yet none have ever been observed of a heart-shape (_cordiform_). Certain foliola of the polyphyllous calyx affect fantastic outlines. In the _Delphinium_, the upper sepal is prolonged into a spur. In the aconites it is hollow like a helmet. The spur of the calyx of the monk's-hood (_Capucine_) is the result of the united prolongation of these foliola. The buckler (_Scutellum_), from which is named the _Scutellaria_, a genus of Labiatæ, is a demi-orbicular boss formed below the inferior lip of the calyx. * * * * * The union of the calicinal foliola sometimes forms a conical calyx, as in the _Silena conica_, and sometimes a cup-shaped calyx, as in the orange; sometimes, moreover, an urceolate calyx, as in the henbane (_Hyosciamus niger_). These forms may vary singularly. The calyx of the black alder (_Rhamnus frangula_) is shaped like a top; that of the haricot (_Phaseolus vulgaris_), like a bell; that of the tobacco-plant, or the _Mollucella spinosa_, is infundibuliform (or funnel-shaped). [Illustration: FIG. 45.--The Henbane.]