COROLLA. ea 



LECTURE XII. 



The term Corolla, or corol, is derived from the Latlll, corona, a 

 crown or chaplet. As the calyx is formed by a continuation of the 

 libres of the outer bark, the corolla is a continuation of the inner 

 coat of the same. The texture of the corolla is delicate, soft, wa- 

 tery, and coloured. It exhales carbonic acid gas, but not oxygen, 

 neither in the dark, nor when acted upon by light. The cuticle, or 

 outward covering of the corolla, is of an extremely fine texture. 

 The rich and variegated colours of flowers, are owing to the deli- 

 cate organization of the corolla ; and to this cause the transient du- 

 ration of this organ may also be attributed. 



The corolla exhibits every variety of colour except black; florists 

 sometimes present us \\ath what they term black roses, and we see 

 some other flowers which approach this colour, yet none are per- 

 fectly black ; the darkest being but a very deep shade of purple. Co- 

 rollas are white, yellow, blue, violet, &c. ; in some, different colours 

 are delicately shaded, and blended ; in others, they meet abruptly, 

 without any intermediate teint. The colour of the corolla, in the 

 same species, often varies without any assignable cause. This fact 

 is strikingly illustrated in the Four o'clock, (Mirabilis ;) the flowers 

 of which are sometimes of pale yellow, sometimes bright crimson, 

 and oilen richly variegated. These varieties are the result of cir- 

 cumstances not under the control of man ; the florist watches these 

 changes, and, as far as possible, avails himself of them in the pro- 

 duction of new beauties in the vegetable kingdom. 



The corolla, before blossoming, is folded in the calyx, as the leaves 

 are within the scales of the leaf-bud, and the whole is then called the 

 flower-bud. In most cases, the calyx and corolla are so distinctly 

 marked, that it is perfectly easy to distinguish them. The colour 

 usually constitutes a very striking mark of difference ; the calyx 

 being ordinarily green, and the corolla of a more lively hue. But 

 the colour is not always a criterion, for in some cases the calyx is 

 beautifully coloured. In the Fuschia, (Lach/s ear-drop,) the calyx is 

 of a bright scarlet; you might at first think it to be the corolla; but 

 if you remove the scarlet coat, you may see, wrapped around the 

 eight stamens, a purple covering; on taking olT each piece carefully, 

 you will find four petals,* as distinct as the petals of a rose ; you 

 will then perceive that the outer covering must be the calyx. 



Linnoeus made the following distinction between the corolla and 

 the calyx ; viz> that the corolla has its petals alternate with the sta- 

 mens, and the calyx has its leafets arranged opposite to them. This 

 rule is not found to be invariable ; it has led some botanists to call 

 that the corolla which others have named the calyx. It seems that 

 we must come to the conclusion that nature has not placed any ab- 

 solute limits between these two organs. 



The corolla sometimes falls off" soon afl;er the flowering, as in the 

 poppy ; it is then said lo be caducous ; sometimes it fades and with- 

 ers upon the stalk, as in the blue-bell ; it is then said to be marescent, 

 or withering; 



* Some botanists call these nectaries, but this seems to be making an unnecessary 

 confusion in terms ; for they have as much the appearance of petals, as those of a rose 

 or pink. 



Corolla-^Description of the corolla— lt3 situation before expanding— How distia* 

 guished from the calyx"? — Rule of Linneeus— Duration. 



