COROLLA. 
59 
LECTURE XII. 
COROLLA. 
Che term Corolla, or corol, is derived from the Latin, corona, a 
i>. own or chaplet. As the calyx is formed by a continuation of the 
liv.res 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 oi 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 with what they term black roses, and we see 
some other flow^ers 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 often richly variegated. These varieties are the result of cir- 
cumstances not under the control of man ; the florist watches these 
cbanges, 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 hvely hue. But 
the colour is not always a criterion, for in some cases the calyx is 
beautifully coloured. In the Fuschia, {Lady^s ear-drop,) the calyx is 
of a bright scarlet; you might at first think it to be the corolla; but 
if y-ou remove the scarlet coat, you may see, wrapped around the 
eight stamens, a purple covering; on taking off" 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. 
Linnaeus 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 after 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 marescentj 
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— Its situation before expanding —Ho w distin- 
guished from the calyx 1 — Rule of Linnaeus— Duration. 
