THE COEOLLA. 



51 



almost in contact with the calyx ; — the cup {cupula) of the acorn (fig. 232), which 

 is composed of small imbricated scales ; — the foliaceous cup, with cut margins, of the 

 Filbert (fig. 233). The prickly cup of the Chestnut (fig. 234), and the calyciform cup 

 of Euphorbia (fig, 235), only differ from the preceding in being many- flowered. 



THE COROLLA. 



The corolla (corolla) is the whorl next within the calyx ; it is usually simple 

 {Rose), sometimes double, i.e. composed of several whorls {Magnolia, Nymphoea) ; its 

 leaves are petals {petala). 



Petals are usually coloured, that is, not green like the (usually foliaceous) 

 sepals ; som^e plants, however {Buckthorn, Vine, Narcissus viridiflorus), have green 

 petals, while others {Helleborus, Aconite, Larhspwr, Columbine, Fennel) have coloured 

 or petaloid sepals. 



In the polypetalous corolla (c. polypetala, dialypetala) the petals are entirely 

 separate from each other {Wallflower, Strawberry, Columbine) ; — in the monopetalous 

 or gainopetalous corolla (c. mono- gamo-petala) the leaves cohere more or less, so as 

 to form a corolla of a single piece. 



The corolla is regular (c. regularis), when its petals, whether free or united, are 

 equal, and form a symmetrical whorl ; irregular (c. irregularis), when the reverse. A 

 corolla may be formed of unequal divisions, and yet be regular ; this is when the 

 petals are alternately large and small, the small being all alike and the large all 

 alike ; or when its divisions are oblique, but all alike, the whole corolla being still 

 symmetrical {Periwinkle, fig. 274). 



Polypetalous Corollas. — The petals are clawed {p. unguiculata), when the broad 

 part, or limb {lamina, fig. 9, l), is narrowed at the base into a petiole called the claw 



237. Eanunculns. 

 Petal. 



i. Barberry. 

 Petal. 



239. Lydinis. 

 Petal. 



{wnguis. Wallflower, fig. 9 ; Pink, fig. 236) ; the petals of the Rose and Ranunculus 

 (fig. 237) are shortly clawed ; those of the Philadelphus and Orange are sessile. 



The claw of the petal is necta/riferous {u. nectarifer), when it bears a honey- 

 secreting gland {Ranunculus, fig. 237) ; this gland may be protected by a scale 

 (fig. 237), or naked {Barberry, fig. 238) ; and the claw itself is naked {u. nudus), when 

 it bears neither gland nor scale {Wallflower, fig. 9; Pink, fig. 286)^ the claw is 

 winged {u. alatus), when it bears a longitudinal membrane on its inner surface {Rose 

 Campion). Little pits {formces) are often found at the point of junction of the claw 



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