Fig. 281. Diagram of a Flax-flower; calyx imbricated and corolla convolute in the bud.
Imbricate or Imbricated, in which the outer parts cover or overlap the inner so as to "break joints," like tiles or shingles on a roof; whence the name. When the parts are three, the first or outermost is wholly external, the third wholly internal, the second has one margin covered by the first while the other overlaps the third or innermost piece: this is the arrangement of alternate three-ranked leaves ([187]). When there are five pieces, as in the corolla of Fig. [225], and calyx of Fig. [281], as also of Fig. [241], [276], two are external, two are internal, and one (the third in the spiral) has one edge covered by the outermost, while its other edge covers the innermost; which is just the five-ranked arrangement of alternate leaves ([188]). When the pieces are four, two are outer and two are inner; which answers to the arrangement of opposite leaves.
279. The imbricate and the convolute modes sometimes vary one into the other, especially in the corolla.
280. In a gamopetalous corolla or gamosepalous calyx, the shape of the tube in the bud may sometimes be noticeable. It may be
Plicate or Plaited, that is, folded lengthwise; and the plaits may either be turned outwards, forming projecting ridges, as in the corolla of Campanula; or turned inwards, as in that of Gentian Belladonna; or
Supervolute, when the plaits are convolutely wrapped round each other, as in the corolla of Morning Glory and of Stramonium, Fig. [282].
Fig. 282. Upper part of corolla of Datura Stramonium in the bud; and below a section showing the convolution of the plaits.