274 



CHAPTER V. 



OF THE BRACTS AND FLORAL ENVELOPES. DISENGAGEMENT 



OF CALORIC. 



The bracts, when but slightly removed from the colour and 

 form of leaves, no doubt perform functions similar to those of 

 the latter organs ; and when coloured and petaloid, it may be 

 presumed that they perform the same office as the corolla. 

 Nothing, therefore, need be said of them separately. 



With regard to the calvx, corolla, and disk, I sliall 

 chiefly follow Dunal's statements in his ingenious pamplilet, 

 (Swr les Fonctions des Organes Jloraux colores et glanduleux. 4to. 

 Paris, 1829. 



The calyx seems, when green, to perform the functions of 

 leaves, and to serve as a protection to the petals and sexual 

 organs ; when coloured, its office is imdoubtedly the same as 

 that of the corolla. 



The common notion of the use of the corolla is, that, inde- 

 pendently of its ornamental appeai'ance, it is a protection to 

 the organs of fertilisation : but, if it is considered that the 

 stamens and pistils have often acquired consistence enough to 

 be able to dispense with protection before the petals are enough 

 developed to defend them, it will become more probable that 

 the protecting property of the petals, if any, is of secondary 

 importance only. 



Among the many speculations to which those interesting 

 ornaments have given birth is one, that the petals and disk 

 are the agents of a secretion which is destined to the nutrition 

 of the anthers and young ovules. These parts are formed in 

 the flower-bud long before they are finally called into action ; 

 in the almond, for example, they are visible some time before 

 the spring, beneath whose influence they are destined to ex- 

 pand. In that plant, just before the opening of the flower, 



