COROLLA. 93 



firm petals, and each one resting upon a broad strong basis, 

 are able to support themselves, and they have no calyx. 



In some plants the calyx serves as a seed-vessel ; as in the 

 order Gymnospermia, of the class Didynamia, where there are 

 four naked seeds lying in the bottom of the calyx. 



LECTURE XII. 



Corolla. 



The term corolla, or corol, is derived from the Latin, corona, 

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

 of the fibres of the outer bark, the corolla is a continuation of 

 the cellular integument, or inner coat of the same. The tex- 

 ture of the corolla is delicate, soft, watery, and coloured. It 

 exhales carbonic acid gas, but does not give off oxygen, either 

 in the dark, or when acted upon by light ; as is the case with 

 the green parts of plants. 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 delicate organi- 

 zation of the corolla ; and to this cause, its transient duration 

 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 flowers, which approach this colour, yet 

 none are perfectly black ; the darkest being but a very deep 

 shade of purple. 



Corollas are white, yellow, blue, violet, &c. ; in some, dif- 

 ferent colours are delicately shaded, and blended ; in others, 

 they meet abruptly, without any intermediate tint. 



The colour of the corolla, in the same species, often varies 

 without any assignable cause. This fact is strikingly illustra- 

 ted in the Four o'clock, (MIRABILIS,) the flowers cf which are 

 sometimes of a pale yellow, sometimes a bright crimson, and 

 often richly variegated. Man does not create these varieties; 

 they are the result of circumstances unperceived by him, and 

 not under his controul ; the florist watches these changes, and as 

 far as possible, avails himself of them in the production 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 corol- 



Corolla Derivation of the term A continuation of the cellular integument 

 Description of the corolla Colour Its situation before expanding. 



