THE FLORAL ENVELOPES COROLLA. 109 



hairs, constituting what is called the pappus (figs. 182, 183). In 

 Centranthus the limb of the calyx is undeveloped when the flower 

 opens, but expands during the ripening of the fruit into a crown 

 of feathered processes. It is doubtful whether the pappus is not 

 in some cases a series of mere epidermal growths or trichomes. 



Duration. The duration of the calyx varies much. In the Papave- 

 racefe it is caducous, falling off when the flower opens ; if it falls with the 

 corolla soon after fertilization of the ovules, it is deciduous ; very fre- 

 quently it is persistent during the ripening of the seeds, as in Labiates, 

 some Solanaceae (fig. 184), Composite (fig. 183), &c. ; the upper part 

 sometimes separates by a circular slit, leaving the. base, as in Datura 

 Stramonium ; occasionally it grows during the maturation of the fruit, 

 and is then accrescent , forming in Phy sails and Trifolium fragiferum, for 

 example, a vesicular envelope to the fruit. In the Marvel of Peru and 

 other plants it is marcescent, remaining and growing into a firm envelope 

 of the fruit. 



Further details respecting the characters of the calyx are given under 

 the head of the Perianth. 



The Corolla. The corolla is composed of all the leaf-like organs 

 or floral envelopes situated between the calyx and the stamens ; 

 these are individually called petals, and may exist in one or more 

 circles. "Where many circles exist, the inner organs often become 

 stunted or deformed, and more or less resemble barren filaments or 

 abortive stamens (Nymphcea). Each petal, under ordinary circum- 

 stances, intervenes or alternates between two sepals. 



The petals are either distinct, and then the corolla is called dialypeta- 

 lous or polypetalous ; or they are more or less coherent or inseparate, and 

 the corolla is gamopetalous, sympetalous, or monopetalous. 



When more than one circle of petals exists, the corolla is multiple or 

 double ; this is normal in certain plants, but is very liable to occur from 

 transformation of stamens, &c., or from actual multiplication of whorls, 

 as in cultivated flowers of the Rose, Camellia, Ranunculus, Anemone, &c. 

 The petals are usually direct outgrowths from the thalamus, but some- 

 times they appear not to be autonomous parts but secondary outgrowths 

 from the stamens, as in some Mallows, Primroses, &c. 



The Petals. Although petals frequently depart more than or- 

 dinary sepals from the character of true leaves in colour and tex- 

 ture, they present greater resemblance in some respects, since they 

 frequently have a more or less developed petiolar region, which is 

 sometimes of considerable length, at other times a mere thickened 

 point ; and they are commonly articulated to the receptacle. The 

 petiolar portion of the petal is called the claw (unguis), the expanded 

 portion the limb (lamina) (fig. 185). Petals are likewise more 

 frequently cut at the margins, as in the fringed petals of Pinks and 

 the laciniated petals of Lychnis Flos-Cticuli, or they are deeply 



