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The floral leaves are well differentiated in these three examples.   In Solanum tuberosum the sepals completely enclose the rest of the flower until shortly before it opens (yellow arrows) after which they remain discreetly behind the petals (red arrows).

The sepals of Papaver orientale remain tightly closed around the corolla until the flower is ready to open (white arrow).  The flower opens by means of the calyx splitting into several segments (magenta arrow) to release the corolla.  The calyx segments then usually fall away to play no further part in proceedings.

In the case of Digitalis purpurea, the sepals enclose the immature flower bud, though the corolla emerges from within the calyx several days before it fully opens (green arrow).  Because the corolla is fused into a single tube it cannot open wide enough to force the calyx back, as happens in Solanum tuberosum, and therefore the sepals retain there original form (blue arrow).  They continue to do so after fertilisation when the corolla is shed and the calyx persists around the maturing seed capsule.


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