FLORAL ENVELOPES — COEOLLA. 



203 



of the claw, it is called linear ; when the limb is prolonged at the base, 

 so as to form two rounded lobes, it is cordate, as in the petal of Genista 

 candicans (fig. 310) ; and when the lobes are acute, it may be sagittate 

 or hastate. The meaning of the terms indicating the forms of petals 

 will be understood by consideriftg those applied to leaves. As a rule, the 

 terms refer to the limb of the petal, which is frequently the only portion 

 developed. In the Poppy, the petals have a puckered or corrugated 

 appearance, arising from their delicacy, and the mode in which they are 

 folded in sestivation. Other petals have a crisp or wavy margin. 



A corolla rarely consists of one petal, and when this occurs, as in 

 Amorpha, it depends on the abortion or non-development of others. 

 Such a corolla is unipetalous (unus, one), a term quite distinct from 

 monopetalous. In general, the corolla consists of several petals, equal- 

 ling the sepals in number, or being some multiple of them. When 

 this is the case, the floral envelopes are said to be symmetrical ; when, 

 however, by the abortion of some of the petals the numbers do not 

 correspond, then the flower becomes unsymmetrical. Under the head 

 of floral symmetry the various changes consequent on non-development 

 of petals will be noticed. A corolla is dipetalous, tripetalous, tetror 

 petalous, or pentapetalous, according as it has two, three, four, or five 

 separate petals. 



The general name of polypetalous ('jroXig, many), or dialypetalous 

 (bia'kyin, to divide), is given to corollas having separate petals, while 

 monopetalous or gamopetalous (/j^ovog, one, and 

 yd/jLog, union) is applied to those in which 

 the petals are united. This union generally 

 takes place at the base, and extends more 

 or less towards the apex ; in Phyteuma the 

 petals are united at their apices also. In 

 some polypetalous corollas, as that of the 

 Vine, the petals are separate at the base, and 

 adhere by their apices. That a monopetal- 

 ous corolla consists of several petals united 

 is shown in such plants as Phlox amoena, 

 where some specimens have petals more or 

 less completely disunited, whUe others ex- 

 hibit the normal form of coherent petals. 

 When the petals are equal as regards their 

 development and size, the corolla is regular; 

 when unequal it is irregular. Even although 

 the separate petals are oblique, still, if they are all equally so, as in 



Fig. 311. Eegular monopetalous or gamopetalona tubular corolla of Spigelia marylandioa. 

 c. Calyx, t, Tube of the corolla. I, Limb of the corolla, s, Stigma at the summit of style. 

 Fig. 312. Irregular gamopetaloua or monopetalous corolla of Digitalis purpurea. Fox- 

 glove, e. Calyx, p. Corolla, t. Tube. I, Limb. 



Fig. 311. 



Fig. 312. 



